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Sustainability of the Dairy Industry: Emissions and Mitigation Opportunities

October 2021
Frontiers in Animal Science 2

DOI:10.3389/fanim.2021.760310

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Authors:

University of California, Davis

Dairy cattle provide a major benefit to the world through upcycling human inedible feedstuffs into milk and associated dairy products. However, as beneficial as this process has become, it is not without potential negatives. Dairy cattle are a source of greenhouse gases through enteric and waste fermentation as well as excreting nitrogen emissions through their feces and urine. However, these negative impacts vary widely due to how and what these animals are fed. In addition, there are many promising opportunities for further reducing emissions through feed and waste additives. The present review aims to further expand on where the industry is today and the potential avenues for improvement. This area of research is still not complete and additional information is required to further improve our dairy systems impact on sustainable animal products.

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SYSTEMATIC REVIEW

published: 18 October 2021

doi: 10.3389/fanim.2021.760310

Frontiers in Animal Science | www.frontiersin.org 1October 2021 | Volume 2 | Article 760310

Edited by:

Pasquale De Palo,

University of Bari Aldo Moro, Italy

Reviewed by:

Andrea Bragaglio,

University of Bari Aldo Moro, Italy

Andrea Vitali,

University of Tuscia, Italy

*Correspondence:

Frank M. Mitloehner

fmmitloehner@ucdavis.edu

Specialty section:

This article was submitted to

Animal Physiology and Management,

a section of the journal

Frontiers in Animal Science

Received: 18 August 2021

Accepted: 17 September 2021

Published: 18 October 2021

Citation:

Peterson CB and Mitloehner FM

(2021) Sustainability of the Dairy

Industry: Emissions and Mitigation

Opportunities.

Front. Anim. Sci. 2:760310.

doi: 10.3389/fanim.2021.760310

Sustainability of the Dairy Industry:

Emissions and Mitigation

Opportunities

Carlyn B. Peterson and Frank M. Mitloehner*

Department of Animal Science, University of California, Davis, Davis, CA, United States

Dairy cattle provide a major beneﬁt to the world through upcycling human inedible

feedstuffs into milk and associated dairy products. However, as beneﬁcial as this process

has become, it is not without potential negatives. Dairy cattle are a source of greenhouse

gases through enteric and waste fermentation as well as excreting nitrogen emissions

through their feces and urine. However, these negative impacts vary widely due to how

and what these animals are fed. In addition, there are many promising opportunities for

further reducing emissions through feed and waste additives. The present review aims to

further expand on where the industry is today and the potential avenues for improvement.

This area of research is still not complete and additional information is required to further

improve our dairy systems impact on sustainable animal products.

Keywords: cows, sustainability, greenhouse gases, methane, ammonia, enteric emissions, waste emissions

INTRODUCTION

Dairy production is considered a major societal asset globally due to its economic and nutritional

beneﬁts. In 2019 alone global milk production totaled 851.8 million tons in milk equivalents

(Outlook, 2020). This contributes to substantial trade impacts, totaling about 76.7 million tons

in 2019, as well as major per capita consumption at about 111.4 kg/year globally (Outlook,

2020). There are over 245 million dairy cows worldwide that on average produce 2,300 kg

per year; although average production is less informative as there is such a major disparity

between production in diﬀerent countries (FAO, 2009). This vast amount of milk production

has a major global beneﬁt—for human health, society, and the economy. In countries with

developing economies livestock serve many purposes including: a source of household income,

a ﬁnancial asset for women, a source of food security, risk management, and a direct link to

human health (Herrero et al., 2013). These beneﬁts increase substantially when viewed from a

macro lens. Global dairy imports totaled over $42.2 billion in 2014 and global dairy exports

expanded 175% from 2005 to 2014 (Davis and Hahn, 2016). There are many dairy commodities

being produced and traded as part of these exports with whole milk powder being the highest,

followed by skim milk powder, butter, and cheese (Outlook, 2020). India is the largest dairy

producer globally, with 22% of global production and 52,841,810 total dairy cattle, the US

is second in production, followed by China, Pakistan, and Brazil (FAO, 1997; Knips, 2005).

While the US may not be the largest global milk producer, the total economic beneﬁt of the

dairy industry is substantial, totaling $628.27 billion dollars in 2018 (O’Keefe, 2018). There are

currently 9,336,000 dairy cows in the U.S. that on average produce 10,610 kg of milk each year,

which amassed to over 99,056,409 kg of milk in 2019 (USDA, 2020). The US dairy sector also

generates over 2.9 million jobs either through direct or indirect support (O’Keefe, 2018). The

Peterson and Mitloehner Sustainability of the Dairy Industry

top ﬁve milk producing states in the US are California,

Wisconsin, Idaho, New York, and Texas, with California

accounting for nearly 20% of national production (Sumner and

Matthews, 2019; USDA, 2020). The dairy industry is such a major

part of California’s economy that in 2019 the associated impact

from milk production and processing was about $57.7 billion

dollars, providing over 179,900 jobs (Sumner and Matthews,

2019). Dairy is the leading agricultural commodity produced

in California, accounting for nearly 13% of the $49.9 billion

dollars in cash receipts generated for the top ranked agriculture

producing state (CDFA, 2019). Not only is the dairy industry a

major driver of the economy but its products serve a substantial

nutritional beneﬁt to the growing human population.

Milk and dairy products are a well-known source of calcium,

vitamins, and other selected minerals as well as being a

complete high-quality protein. One of the most well-documented

nutritional beneﬁts of dairy products is for bone health—

particularly for its ability to prevent osteoporosis and other

bone diseases. In particular the calcium in milk positively aﬀects

bone mass in children and when coupled with vitamin D, as

seen in fortiﬁed milk products, will prevent bone loss and

osteoporotic fractures in aging populations (Caroli et al., 2011).

For low-income countries struggling with nutritional deﬁciencies

in children, studies have shown that supplementation with

dairy products causes a signiﬁcant increase in vitamin B-12

plasma concentrations, improves cognition, growth and activity

(Allen, 2003; Siekmann et al., 2003). In addition, maternal milk

intake during pregnancy is positively associated with infant

birth weight, and subsequent bone mineral content during

childhood (Gil and Ortega, 2019). Other milk components,

including bioactive peptides present in the whey components

of milk were shown to beneﬁt the immune system due to their

antimicrobial and immunomodulatory properties (Madureira

et al., 2010). Consumption of dairy products has shown

an inverse relationship with cardiovascular disease in that

consumption of milk and dairy is associated with a lower

incidence of type-2 diabetes and improvements in glucose

homeostasis (Hirahatake et al., 2014). While milk is relatively

high in saturated fat it has been shown that milk intake

did not increase cardiovascular risk (Visioli and Strata, 2014).

Furthermore, milk intake was associated with reduced risk of

childhood obesity as well as improved body composition and

weight loss in adults (Thorning et al., 2016). Dairy intake was

also shown to be inversely associated with incidence of cancer

including colorectal, bladder, gastric, and breast cancer and was

not shown to be associated with any other additional forms

of cancer (Thorning et al., 2016). Although dairy production

serves many beneﬁts to overall nutrition, human health, and the

economy, there has been increasing concern about the impact of

dairy on the environment.

Impact of Dairies on Climate Change and

Air Quality

The earth’s surface has undergone massive increases in

temperature, primarily in the last three decades, and the last 30

years we have seen the warmest period ever recorded (IPCC,

2014). In addition to this temperature increase, there have been

other major changes to the climate including trends of increasing

ocean temperature, rising sea level, as well as a major increase in

greenhouse gas emissions (IPCC, 2014). Another phenomenon

that has occurred over the last few centuries is an increase in

ocean uptake of CO2, causing ocean acidiﬁcation and a decrease

in surface water pH, as well as a rapid decrease in glaciers and

ice sheets around the globe. These major changes in the climate

are primarily due to anthropogenic (human caused) emissions

of GHGs that have steadily increased since the beginning of the

industrial revolution in the 1750s (Place and Mitloehner, 2010).

Atmospheric concentrations of CO2, CH4, and N2O are also

the highest they have been in at least the last 800,000 years,

with about 78% of these CO2emissions resulting from industrial

processes and the combustion of fossil fuels (IPCC, 2014). Several

studies have indicated that the production of livestock, including

the stages of growing, transport, processing, and consumption

have a relatively large impact on climate change (de Vries and

de Boer, 2010; Milani et al., 2011). Dairy cattle in particular

were shown to impact the environment through their potential

negative contributions to air, water, and land (Naranjo et al.,

2020).

In regards to the environment, the US Dairy industry has

seen substantial improvements over the years. In particular it

has seen a great increase in milk production primarily due

to dramatic increases in milk production per cow, increase in

average cow numbers per farm, as well as an overall decrease

in total animal numbers (Wolf, 2003; Barkema et al., 2015).

Some other major changes over the last 50 years include a shift

to a primarily Holstein dairy herd (90%), an increased heifer

growth rate, decreased age at ﬁrst calving, and an increase in the

use of artiﬁcial insemination (Capper et al., 2009). Nutrition of

dairy animals has also allowed for a substantial improvement in

production via use of total mixed-rations balanced for nutrient

and energy requirements accounting for each animals age and

stage of lactation (National Research Council, 2001). Genetic

selection has also been a major driver in increased productivity,

longevity, and eﬃciency of dairy cows, further reducing the

environmental impact per unit of milk production (Pryce

and Haile-Mariam, 2020). These improvements in nutrition

and genetics, in conjunction with improvements to herd

management, accomplished primarily through increasing density

on dairy farms, have resulted in a fourfold increase in milk yield

from the mid-1940s until 2007 (Von Keyserlingk et al., 2013).

This eﬃciency of milk production has continued to improve to

2014 where 1 kg of energy and protein corrected milk (ECM) for

California emitted between 1.12 and 1.16 kg of CO2equivalents

(CO2e) in 2014 compared with 2.11 kg of CO2e in 1964, resulting

in a 45% reduction in CO2e (Naranjo et al., 2020). The dairy

industry has continued to still further these improvements. Dairy

production systems in 2017 compared with 2007 have reduced

their inputs by 25.2% for animal numbers, 17.3% for total feed,

20.8% for land, and 30.5% for water of one million metric ton

of energy-corrected milk, furthering the exceptional productivity

gains and environmental progress of the industry (Capper and

Cady, 2020). Even with these major advancements made over

the last century, dairy systems still impact the environment

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Peterson and Mitloehner Sustainability of the Dairy Industry

through: GHG emissions from enteric fermentation, manure

management, and feed production, water use for feed production

and milk processing, water quality with contaminants including

nitrogen (N) and phosphorous (P) from manure, as well as the

requirement for land used in feed production (Naranjo et al.,

2020). In addition to the direct impacts of cattle, such as N

and P as a result of dairy production systems, there are also

environmental impacts associated with dairy processing and

subsequent production (Milani et al., 2011).

Manure Emissions From Dairy Cattle

Dairy manure has the potential to negatively impact the

environment. Nitrogen not retained by the animal or secreted

in milk will be excreted in the urine and feces of the animal

(Hristov et al., 2019). Urine is more susceptible to losses of N to

the environment from the animal waste as compared with fecal

N (Dijkstra et al., 2013, 2018a). Dairy waste is a signiﬁcant source

of N and P that when land applied in excess of crop requirements

can cause contamination of surface water (Knowlton and Cobb,

2006). This excess N and P in water causes a rapid bloom in

the growth of algal populations that consume dissolved oxygen

in water, termed eutrophication, which reduces the available

dissolved oxygen required for growth of aquatic animal life

(Knowlton and Cobb, 2006). Excess N can also contaminate

ground water through leaching. This poses a problem for human

and animal health as consumed nitrate from drinking water

is converted to nitrite in the digestive tract, which replaces

oxygen in hemoglobin and leads to cyanosis (oxygen starvation)

(Knowlton and Cobb, 2006).

Air quality also aﬀects human and animal health as well as

the environment, and dairy cattle have been known to contribute

to poor air quality. One such compound that aﬀects air quality

produced by dairy cattle is NH3. Ammonia is produced when

N in urea from the animal’s urine reacts with urease present in

feces (Place and Mitloehner, 2010). Ammonia production from

dairy waste is dependent on a variety of factors including: urea

content in urine, pH, and temperature, as well as the enzymatic

activity of urease (Muck, 1982; Sun et al., 2008). In addition

to NH3losses from fresh waste, volatilization can occur during

waste application to soil as a fertilizer, as well as during the

long term housing and storage of manure (Bussink and Oenema,

1998). Total losses of NH3can be between 0.82 and 250 g

NH3/cow/day, with the total loss dependent on the amount and

composition of animal waste as well as the environment and

management conditions of the manure storage (Bussink and

Oenema, 1998; Hristov et al., 2011). Dairy waste management

strategies greatly inﬂuence air emissions of NH3. The greatest

NH3emissions occur after ﬁeld application, followed by the

manure management strategies, for example, separated liquid

and solids, aerated, straw covered, untreated, then anaerobic

digested (Amon et al., 2006).

Nitrogen in waste can also contribute to GHG production

through the formation and volatilization of nitrous oxide

(N2O). Nitrous oxide is created during incomplete microbial

denitriﬁcation process where nitrate is converted to N gas with

the potential to create N2O, an extremely volatile byproduct

(Place and Mitloehner, 2010). Land applied dairy manure on

cropland as well as the long term storage of manure in lagoons

can contribute to emissions of N2O (Velthof et al., 1998; Place

and Mitloehner, 2010). The N2O emissions during storage

depend on the N and carbon content of the manure (Amon et al.,

2006). Nitrous oxide production and subsequent volatilization

is also dependent on environment and management. Higher

temperatures as well as surface coverings contribute to increasing

emissions, whereas anaerobic conditions, such as those found

in lagoon systems, have lower N2O emissions (Dustan, 2002).

The process of long term storage of manure seems to also

contribute a larger proportion of N2O emissions compared with

land application with aerated, straw covered, digested, separated,

and untreated manure contributing decreasing amounts of N2O

emissions (Amon et al., 2006).

Another substantial GHG produced by dairy cattle waste

is methane (CH4). The amount of CH4emitted by dairy

waste is dependent on the amount of carbon, hydrogen, and

oxygen present in the waste, making manure storage, diet, and

bedding major contributors to total CH4production (Place and

Mitloehner, 2010). A smaller proportion of CH4is also produced

in the hindgut of the animal via post ruminal digestion and

fermentation (Ellis et al., 2008). This CH4is mostly absorbed

from the hindgut (89%) and eventually eructated by the animal

or excreted with the manure (11%) (Murray et al., 1976; Immig,

1996; de la Fuente et al., 2019). Manure CH4emissions are

substantially higher from long term storage compared with ﬁeld

application (Amon et al., 2006). These emissions are highest from

straw covered manure and emissions decrease with untreated

manure, followed by separation, aeration, and digested manure

management methods (Amon et al., 2006).

Dairy waste can also produce volatile organic compounds

(VOC). Volatile organic compounds are a class of chemicals

that when reacted with oxides of N and sunlight contribute

to ozone formation (Place and Mitloehner, 2010). There were

73 detectable VOCs from slurry wastewater lagoons with the

most common VOCs being methanol, acetone, propanal, and

dimethylsulﬁde (Filipy et al., 2006; Shaw et al., 2007). As

with other waste emissions, VOCs from dairy waste increase

with ambient air temperature with summer months having the

highest rates of VOC emissions (Filipy et al., 2006). The largest

contribution of VOCs on dairy systems come from fermented

feedstuﬀs (i.e., silage) (Place and Mitloehner, 2010).

Effect of Nutrition on Emissions From Dairy

Cattle

Dairy cattle enteric emissions have been shown to contain a

variety of gases. For example dairy cattle emit CO2as a byproduct

of aerobic cellular respiration, which is the GHG with the greatest

contribution to climate change (Place and Mitloehner, 2010).

However, this gas is not considered a net contributor to the rise in

GHGs due to the CO2having been previously recycled from the

atmosphere by ﬁxation during photosynthesis in plants, which

are then consumed by the cattle (Steinfeld et al., 2006). Dairy

cattle can also produce N2O from enteric emissions as a result of

the NO3reduction process that takes place by the microbes in the

rumen (Kaspar and Tiedje, 1981). Due to the small production of

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Peterson and Mitloehner Sustainability of the Dairy Industry

enteric N2O, these emissions are not always considered in dairy

emission analyses (Casey and Holden, 2005).

The most signiﬁcant enteric emission compound from dairy

cattle is CH4. Methane acts as a hydrogen sink in the rumen and

is an end product of CO2reduction by methanogenic archaea

(Janssen and Kirs, 2008). Methanogens serve an important role

in rumen health by removing this hydrogen that can be toxic

to some bacterial communities and also causes the disease state

rumen acidosis (Beauchemin et al., 2009). In addition to being

a potent GHG, CH4also accounts for a 2–12% loss of potential

energy available to the animal that could otherwise be used for

maintenance and productive purposes as growth gestation, or

lactation (Moe and Tyrrell, 1979).

Dairy cattle diets have a signiﬁcant impact on enteric

emissions, mostly CH4. As there is large variability in the

ingredient and chemical composition of diets fed to dairy cattle,

nutrition and feeding strategies have the greatest potential for

reducing CH4emissions, with potential reported reductions

between 2.5 and 15% (Knapp et al., 2014). The amount of CH4

produced is dependent on many factors including intake and

chemical composition of the carbohydrate, retention time of feed

in the rumen, rate of fermentation of diﬀerent feedstuﬀs, as well

as the rate of methanogenesis (Beauchemin et al., 2009). Altering

feed digestibility and chemical composition cause a shift in the

proportions of volatile fatty acids (VFA) with the predominant

VFAs being propionate, butyrate, and acetate (Knapp et al., 2014).

This shift in VFA proportion is important because propionate

also acts as a hydrogen sink so shifting from acetate and butyrate

formation to propionate will consume reducing equivalents

and help preserve the pH balance in the rumen (Hungate,

2013). An overall reduction in CH4emissions or a shift in

VFAs can be accomplished through a variety of altered feeding

strategies. More energy dense or more digestible feedstuﬀs result

in additional energy available to the animal and generate less

CH4from fermentation (Knapp et al., 2014). An increase in

starch proportion of the diet, such as through an increase in

concentrate levels, also results in a more rapid fermentation

of these feedstuﬀs and therefore decreased CH4production

(Moe and Tyrrell, 1979; Johnson and Johnson, 1995). Feeding

higher starch diets requires increased grain production, which

can cause additional consumption of fossil fuel and fertilizers

that results in an increase in N2O and CO2; however, this

system is usually oﬀset by the substantial decrease in overall

in CH4emissions (Johnson et al., 2002; Lovett et al., 2006).

Feeding of cereal forages can also favor propionate production

and reduce CH4emissions due to the higher starch concentration

(Beauchemin et al., 2009). Higher concentrations of legumes,

such as alfalfa, when compared with grass forage based diets can

also lead to an overall decrease in CH4emissions (McCaughey

et al., 1999). Age of harvest of forage also has a signiﬁcant

impact on emissions, with advancing maturity resulting in more

ligniﬁed and less fermentable substrate contributing to increasing

emissions associated with higher ruminal acetate (Pinares-Patiño

et al., 2003). In addition to alterations in forage or concentrate

composition and ratio, supplementation of lipids to dairy cattle

diets can also mitigate enteric emissions (Hristov et al., 2013b).

Replacing concentrates with lipids results in a decrease in

fermentable substrate by the microbes in the rumen and can

also decrease total protozoa and methanogen populations (Ivan

et al., 2004). An inclusion of high-oil by-products, such as

distillers grains or oilseed meals, can result in decreased CH4

emissions (Hristov et al., 2013b). Research on ensiled feeds in

relation to enteric emissions is generally lacking, although it is

anticipated that corn silage will mitigate emissions due to its

higher starch content (Gerber et al., 2013). Furthermore, when

directly comparing grass-versus corn silage, a higher inclusion of

corn silage seems to mitigate enteric CH4emissions (Mills et al.,

2008; Doreau et al., 2012). There are many potential methods

to mitigate enteric emissions through alterations to nutrition

strategy and composition.

Manure emissions are also signiﬁcantly impacted by various

dairy cattle feeding strategies. One of the main issues with

altering feeding strategies to reduce enteric emissions is that

fermentable substrate in the manure can increase, as has been

seen with increasing the concentrate to forage ratio in the diet

(Hindrichsen et al., 2006; Beauchemin et al., 2009). This response

has also been seen with the supplementation of certain fatty

acids (Kreuzer and Hindrichsen, 2006). To alleviate this issue,

feeding concentrate with higher ligniﬁed ﬁber has been shown

to mitigate both enteric and manure-derived emissions (Kreuzer

and Hindrichsen, 2006; Aguerre et al., 2012). These changes

to concentrate ratio do not have an impact on N containing

manure emissions, as would be expected (Hindrichsen et al.,

2006; Aguerre et al., 2012). The greatest impact of diet on waste

emissions can be seen when feeding low crude protein (CP)

diets to dairy animals, which results in decreased excreted N and

subsequent NH3volatilization (Cardenas et al., 2007; Lee et al.,

2012; Edouard et al., 2019). Comparing fresh grass with prepared

hay at the same CP content, feeding hay causes a higher overall N

and C/N ratio excreted but waste from grass fed animals tends to

volatilize more NH3emissions (Külling et al., 2003). Corn silage

inclusion in diets has also caused changes to manure emission

proﬁles. For example when comparing corn silage versus grass

silage, corn silage tended to reduce urinary N excretion (Mills

et al., 2008). When adding corn silage to alfalfa silage based diets

there is also an improvement in N eﬃciency leading to a decrease

in N losses in urine and subsequent decreases in available NH3

and N2O volatilization (Gerber et al., 2013). Higher sugar forages

also reduce N excretions, which also have the potential to limit

the N available to be volatilized as gaseous emissions (Miller et al.,

2001; Parsons et al., 2012; Gerber et al., 2013). Overall a variety

of feeding strategies can be employed to help mitigate emissions

from enteric and waste sources of dairy animals.

Mitigation Strategies for Dairy Cow Enteric

Gas Emissions

In addition to changes to the diet ingredient composition, there

are also additives to diets that may mitigate enteric emissions.

While there are various types of strategies to alter enteric

sourced emissions this section will focus primarily on methods

to alter CH4. One promising strategies for CH4reduction is

via feed supplementation of the methanogenic inhibitor, 3-

Nitrooxypropanol (3-NOP). 3-Nitrooxypropanol is a structural

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Peterson and Mitloehner Sustainability of the Dairy Industry

analog to methyl-coenzyme M, which acts on methyl-coenzyme

M reductase (MCR), a nickel enzyme involved in the ﬁnal

reduction stages of methanogenesis (Duin et al., 2016). In the

rumen system 3-NOP was shown to mimic methyl-coenzyme M

and target the active site of MCR, thus inhibiting the enzymes

activity and subsequently causing a decrease in CH4production

(Duin et al., 2016). Research demonstrated that feeding 3-NOP

to cattle decreased enteric CH4emissions up to 95% in vitro

(Martínez-Fernández et al., 2014) and 84% in vivo (Vyas et al.,

2016). 3-NOP was tested in vivo in multiple ruminant models

including sheep (Martínez-Fernández et al., 2014), beef cattle

(Romero-Perez et al., 2015; Vyas et al., 2016), as well as Holstein

dairy cattle (Reynolds et al., 2014; Hristov et al., 2015; Lopes

et al., 2016; Haisan et al., 2017). Reynolds et al. (2014) fed 3-

NOP at a rate of either 500 or 2,500 mg/d via rumen ﬁstula

before each feeding and using respiration calorimetry found a

reduction of 6.6 and 9.8% in CH4emissions, respectively. They

also found a decrease in dry matter intake (DMI) and an increase

in milk protein at the higher dose, without other changes in

production parameters. Haisan et al. (2017) also fed 2,500 mg/d

and using the SF6 systems measured a reduction in emissions

from 17.8 to 7.18 g/kg of DMI without adverse eﬀects to milk

or DMI. Hristov et al., 2015 fed 3-NOP at a rate of 40, 60, or 80

mg/kg of DMI and measured reductions via a GreenFeed system

of 25, 31, and 32%, respectively. They also found no changes

to DMI or milk production with an increase in protein yield

following supplementation. Similarly, Lopes et al. (2016) also

fed 60 mg/kg of DMI and found a 31% decrease in emissions

with an increase in milk fat concentration. Dijkstra et al. (2018b)

evaluated the overall eﬃcacy of 3-NOP in research trials and

determined that greater 3-NOP dose results in a greater reduction

of CH4emissions. These trials also used diﬀerent diets, which did

not seem to eﬀect the impact of 3-NOP on emissions. However,

this molecule has yet to be evaluated for its eﬃcacy among

diﬀerent dairy breeds and the potential side eﬀects of its use have

not fully elucidated. Additionally, it has yet to be determined

whether 3-NOP has any unintended consequences of carryover

to the excreta of supplemented animals.

Nitrates oﬀer great promise for their potential to mitigate

CH4and have been well studied for their use in beef cattle

diets with more recent literature focusing on the potential for

use in dairy cattle. Nitrate in the diet serves as a non-protein

N source that acts as an electron receptor resulting in eﬀective

and consistent reduction of enteric emissions. However, nitrate

has the potential to induce methemoglobinaemia and is a known

carcinogen (Lee and Beauchemin, 2014). Nitrate toxicity can

generally be avoided when the rumen ecosystem is allowed time

to adapt (Hristov et al., 2013b). Even with the potential for

toxicity, the beneﬁts of 16–50% reduction in CH4emissions

continue to drive research feeding nitrates (Leng and Preston,

2010). Van Zijderveld et al. fed nitrate at a rate of 21 g/kg DMI

and measured a persistent reduction in CH4of 16% via use of

open-circuit indirect calorimetry chambers (Van Zijderveld et al.,

2011). They did not measure changes in milk yield or DMI for

the supplemented animals. Similar research conducted by other

authors found a reduction in emissions of CH4/d from 363 g

for control animals to 263 g for nitrate supplemented animals

also at 21 g/kg DMI (Klop et al., 2016). They also measured

a reduction in milk protein concentration as well as DMI for

nitrate-supplemented cows. When high levels of nitrate (20 g/

kg DMI) were supplemented in a similar study design they

found a 31% reduction in CH4along with a decrease in DMI

during nitrate feeding (Lund et al., 2014). Another study found

a 28% decrease in methanogenesis after feeding nitrate at 2.3% of

DM to nonlactating cows, however they also found a signiﬁcant

decrease in feed intake from the supplemented animals (Guyader

et al., 2015). Another trial reported a 10% decrease in DMI,

coupled with a 17% decrease in CH4where dairy cattle diets were

supplemented with nitrate at 1.5% of DMI (Meller et al., 2019).

A meta-analysis found a persistent reduction in CH4emissions

in both in vitro and in vivo studies (Lee and Beauchemin, 2014).

Similar to 3-NOP, TMR composition did not seem to have a

major eﬀect on nitrate supplementation as these studies all saw

a signiﬁcant decrease in emissions with vastly diﬀerent diets.

Plant biological compounds have also been explored for their

potential to reduce emissions. Condensed tannins are secondary

phenolic compounds that generally discourage consumption by

herbivories and also concentrate N in the plant (Waghorn, 2008).

When consumed by dairy cattle these tannins bind protein

in the rumen, which reduces the degradation of protein and

enhances protein ﬂow to the intestines (Beauchemin et al.,

2009). Tannin source appeared to make a major diﬀerence in

subsequent mitigation of CH4emissions from dairy cattle. For

example, the Hedysarum coronarium species supplemented at

27 g /kg DMI resulted in lower CH4emissions by dairy cattle

(Woodward et al., 2002). Whereas, Schinopsis quebracho-colorado

supplemented at 0, 1, or 2% of dietary DM did not have any

eﬀect on enteric emissions or dry matter intake of beef cattle

(Beauchemin et al., 2007). Additional studies looking at Lotus

pedunculatus (fed at 10% of dry matter) and Medicago sativa (fed

at 0.1% of dry matter) tannin supplementation found decreased

CH4emissions from both strains of condensed tannins, although

DMI was not measured, which were attributed to reducing

hydrogen production and direct inhibition on methanogenic

archaea (Tavendale et al., 2005). A meta-analysis identiﬁed a

general anti-methanogenic eﬀect of tannins across diﬀerent

sources and that the variation in methane reduction seen in

previous studies may have been due to the low tannin levels

used in those trials (Jayanegara et al., 2012). They also found that

dietary tannins tended to increase DMI but decrease total tract

digestibility, apparent CP digestibility, and neutral detergent ﬁber

digestibility. As with previous feed supplementation, these trials

did not quantify emission changes to waste sources. Additional

research into tannins in various diets as well as its eﬀect on milk

production and manure CH4emissions needs to be explored.

In addition to tannins, secondary plant compounds called

essential oils have been explored for their antimicrobial

properties. Essential oils are naturally occurring volatile

components in plants that provide the plant speciﬁc color

and ﬂavor characteristics (Benchaar et al., 2008). Essential

oils reduced CH4production through inhibiting growth and

energy metabolism of selected bacteria and archaea including

methanogens (Benchaar et al., 2008). Over 250 essential oils have

been identiﬁed and contain mixtures of terpenoids, a variety of

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Peterson and Mitloehner Sustainability of the Dairy Industry

low molecular weight aliphatic hydrocarbons, alcohols, acids,

aldehydes, acrylic esters, N, sulfur, coumarins, and homologs

of phenylpropanoids (Beauchemin et al., 2009). These essential

oils underwent in vitro screening for their potential to reduce

rumen CH4emissions and while 35 were found to be eﬀective

only six were found to have signiﬁcant decreases in emissions

without disrupting digestibility (Bodas et al., 2008). It is diﬃcult

to directly compare essential oils because of the number of

diﬀerent compounds as well as the diﬀerence in study design

and species studied. In addition, few essential oils have been

thoroughly evaluated in vivo.Benchaar and Greathead (2011)

performed additional in vitro testing and found decreased CH4

production following supplementation with oregano, rhubarb,

thyme, cinnamon, horse radish, frangula, and garlic. Tekippe

et al. (2011) fed oregano leaf at a rate of 500 g/d to lactating dairy

cattle and measured rumen CH4production 8 h after feeding.

They found a decrease in total CH4yield but did not see adverse

eﬀects on DMI or milk yield with the added beneﬁt of increased

milk fat content. In a follow up study by Hristov et al. (2013a)

they fed lactating dairy cows 250, 500, and 750 g of oregano leaf

per day and found a linear reduction in methane per unit of DMI

coupled with a linear decrease in DMI but no diﬀerences in any

milk production parameters. In addition to particular isolates

of essential oils, there are also commercial essential oil blends

being marketed for their potential to reduce enteric CH4. One

essential oil blend is Agolin SA created in Bière, Switzerland

that is comprised of coriander oil, geranyl acetate, and eugenol.

Agolin was tested in vitro and found a signiﬁcant initial decrease

in rumen CH4, but the eﬀect did not persist over time (Klop et al.,

2017b). Another Agolin in vitro trial found similar results where

there was an initial reduction in methane, but the eﬀect was not

constant over the total 72 h incubation period (Castro-Montoya

et al., 2015). These authors also conducted feeding trials with

the Agolin essential oil product. Castro-Montoya et al. (2015)

found a trend in reduction of daily emissions relative to intake

and (Klop et al., 2017a) found initial decrease in CH4/DMI

only for the ﬁrst 2 weeks of feeding Agolin, after which Agolin

did not impact CH4. In addition, Klop et al. (2017a) reported

a decrease in DMI over the second half of the supplementation

period. Hart et al. (2019) also supplemented lactating dairy cattle

with Agolin essential oils and measured a reduction in CH4

emissions per pen. Changes to DMI, milk production, or fat

composition after feeding of essential oils have also been reported

following Agolin supplementation. For example, Santos et al.,

2010 reported numerically lower DMI with an increase in milk

fat production, a 0.03 kg/day increase in fat production, from

Agolin supplemented cows, whereas Elcoso et al. (2019) saw an

increase in ECM supplemented animals without diﬀerences in

DMI. However, for Santos et al. (2010) the Agolin treatment was

applied to the pen and not the individual animal. Elcoso et al.

(2019) also estimated rumen CH4production from fermented

rumen ﬂuid and found supplemented animals to be lower,

but there was an interaction between the time and treatment.

Hart et al. (2019) also found a greater milk yield and ECM for

Agolin supplemented animals. Clearly the large discrepancy

in responses across research studies for Agolin emphasizes

the need for additional research to determine if the essential

oil product has application at the farm level to reduce enteric

CH4emissions.

Mitigation Strategies for Dairy Cow

Manure Gas Emissions

While there are many ways in which to alter manure emissions

depending on the desired outcome this literature search will focus

on methods to alter CH4emissions speciﬁcally, of which there

are quite a few promising strategies. One manure amendment

strategy includes the use of biochar. Biochar is a general term

applied to products produced by thermal decomposition from

a variety of biomass substrates for agricultural applications

including the added beneﬁt of optimizing the process of

composting (Godlewska et al., 2017). Biochar was shown to have

a multitude of beneﬁts including improving the overall process

of composting, improving N conservation, facilitating nutrient

transformation, and favoring oxygen supply (Vandecasteele et al.,

2016; Chen et al., 2018; Mao et al., 2018). Other studies

demonstrated that biochar improved soil physicochemical

properties, beneﬁted nutrient conservation as well as boosted

crop production (Li et al., 2015; Mao et al., 2017; Wu et al.,

2017). While the beneﬁts of biochar as amendments to poultry

and pig manure have been well-documented (Agyarko-Mintah

et al., 2017; Chen et al., 2017; He et al., 2019), its use in dairy

cattle manure management has been less thoroughly studied.

Jindo et al. (2012) added biochar to cattle manure to measure

microbial communities, causing a signiﬁcant increase in the C/N

ratio from the additional of high carbon biochar materials, but

they did not measure emissions from these systems. Duan et al.

(2019) applied wood or wheat straw biochar with and without

bacterial supplementation to cattle manure compost. While this

study did not measure CH4emissions speciﬁcally, they found

that biochar in addition to bacterial amendments enhanced the

compost overall and that Bacteroidales,Flavobacteriales, and

Bacilli were the communities with the highest abundance in

the samples. Awasthi et al. (2020) also tested biochar with and

without a bacterial inoculum applied to fresh cattle manure in

a reactor and found treatments with the inclusion of biochar

produced substantially less CH4as compared with the control.

Overall, the impact and mechanism of action of biochar on CH4

emissions from dairy waste speciﬁcally deserves further study.

Bacterial inoculums, as well as the supplementation of

bacterial produced enzymes, have been well-researched in the

literature for their potential to alter CH4emissions. Bacteria

are involved in many of the breakdown processes that occur in

manure management systems including reactions of hydrolysis,

acidogenesis, acetogenesis, and methanogenesis, the latter

of which has the potential to increase methane production

(Juodeikiene et al., 2017). While increased CH4may seem

in conﬂict with the present literature review, this manure

management strategy can be applied to systems where CH4can

be captured and transformed into biofuel or other renewable

resources. One such example is through anaerobic digestion in

which organic material is degraded by microbes in the absence

of oxygen (Rodriguez Chiang, 2011). A variety of bacterial

communities have been researched for their potential to change

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Peterson and Mitloehner Sustainability of the Dairy Industry

CH4emissions from various substrates. Juodeikiene et al. studied

Lactobacillus delbrüeckii, and found an increase in methane of

76% from dairy wastewater from milk processing, as compared

with 38% without the addition of bacteria (Juodeikiene et al.,

2017). Xu et al. pretreated corn straw with Bacillus subtilis, and

increased CH4production 17.35% above the untreated control

(Xu et al., 2018). He et al. also supplemented microalgal biomass

with Bacillus licheniformis, and bacterial supplementation

increased CH4production from 9.2 to 22.7% (He et al.,

2016). Commercial products have also been marketed for

their application in manure management systems, including

BiOWiSH products. BiOWiSH products contain a proprietary

mixture of Bacillus and Lactobacillus, including Bacillus subtilis,

Bacillus amyloliquefaciens, Bacillus licheniformis, Bacillus

pumilus, Pediococcus acidilactici, Pediococcus pentosaceus,

Lactobacillus plantarum, Bacillus meagerium, Bacillus coagulans,

and Paenibacillus polymyxia, a product covered by a patent

outlined by Carpenter et al. (2014). The process to create

BiOWiSH involves individually fermenting each organism,

followed by harvesting and then drying of each organism.

Finally, the dried organism ground to produce a powder with a

ﬁnal moisture content <5% and a ﬁnal bacterial concentration

between 105and 1011 colony forming units (CFU) per gram of

dried product. While these products have not been evaluated for

their eﬀect on CH4speciﬁcally, these products claim to digest

sludge, and reduce biological oxygen demand, total suspended

solids, total Kjeldahl N, and odor from manure lagoons. The

BiOWiSH product has been applied to dairy waste systems and

showed promise for manure mitigation including: a reduction in

total suspended solids and a degradation and removal of N(Lee,

2012; Pal, 2012; Holland, 2017). However, BiOWiSH has not

been studied with respect to its eﬀects on CH4emissions from

dairy wastewater systems.

Gypsum based products have been applied to dairy waste

systems for manure amendments. One of the more common

forms of gypsum used for manure amendment is ﬂue gas

desulphurization gypsum that is a by-product of wet gas

desulphurization from coal-ﬁred power stations (Febrisiantosa

et al., 2018). This gypsum has a low heavy metal content and

contains high concentrations of S, Si, and Ca that are essential

minerals nutrients required by plants (Guo et al., 2016). Gypsum

has been fairly well-characterized for its eﬀects on N containing

compounds. Tubail et al. found gypsum supplemented dairy

manure lost signiﬁcantly less N as compared with the control

dairy manure without supplementation (Tubail et al., 2008).

Li et al. applied gypsum to pig manure compost and found

signiﬁcant reductions in NH3and enhanced mineral and total

N contents (Li et al., 2018). Hao et al. applied gypsum to

beef cattle manure and found a signiﬁcant reduction in CH4

emissions from the medium and high doses of gypsum as

compared with the control (Hao et al., 2005). Yang et al. studied

kitchen waste compost and found the addition of gypsum to

dramatically reduce CH4emissions by 85.8% (Yang et al., 2015).

While these study designs don’t quite have the same application

as is intended in this literature review, the potential for use

of gypsum as a manure amendment is promising. There are

also commercial additives being marketed for their potential

to mitigate CH4emissions, including SOP Srl, a company that

makes the SOP Lagoon products. SOP Lagoon consists of calcium

sulfate dihydrate (agricultural gypsum) that is processed with

the company’s proprietary technology. The product’s claim is

to improve liquid manure management through inhibiting the

production and release of GHGs (e.g., CH4and N2O) and

criteria pollutants (e.g., NH3) while also reducing the odor

intensity from liquid manure. Borgonovo et al. ﬁrst tested

the gypsum-based commercial additive, “SOP LAGOON,” on

fresh dairy manure and found the additive to be eﬀective in

reducing direct NH3and GHG emissions, including a signiﬁcant

mitigation of CH4emissions (Borgonovo et al., 2019). Recent

literature by Peterson et al. applied SOP Lagoon to liquid

stored dairy cattle manure over a 2 week period and found

similar results including signiﬁcant reductions in NH3emissions

(22.7% for the supplemented systems as compared with an

unsupplemented control) (Peterson et al., 2020). With the strong

literature documenting the potential for gypsum to decrease CH4

emissions, this seems like a viable manure amendment strategy.

In addition to the previously described additives, a variety of

additional organic substrates have been applied as amendments

in diverse applications. These additional amendments include

lime and coal ﬂy ash (Fang et al., 1999; Wong et al., 2009),

zeolite (Awasthi et al., 2016; Chan et al., 2016), bentonite (Wang

et al., 2016), clay (Chen et al., 2018), and medical stone (Awasthi

et al., 2017; Wang et al., 2017), among others. These amendments

require further research to evaluate their potential use in dairy

manure speciﬁcally as well as the resulting CH4emissions after

their application.

CONCLUSIONS

There is an increasing amount of literature and research data

concerning strategies to further reduce livestock’s impact on the

environment. However, there is no one method of environmental

sustainability in these systems and even still there are many

unanswered questions. Future research needs to better quantify

full reduction potential and elucidate the mechanism of actions

of these compounds including 3-NOP, tannins, essential oils,

bacterial inoculums, and biochar, among others. Furthermore,

slight alterations to dairy cattle diets can cause major changes

in both enteric and waste emissions. Research on mitigating the

environmental impact of dairy cattle will allow dairy producers

to contribute to a more sustainable dairy production system.

DATA AVAILABILITY STATEMENT

The original contributions presented in the study are included

in the article/Supplementary Material, further inquiries can be

directed to the corresponding authors.

AUTHOR CONTRIBUTIONS

CP wrote the manuscript draft. All authors contributed to the

article and approved the submitted version.

Frontiers in Animal Science | www.frontiersin.org 7October 2021 | Volume 2 | Article 760310

Peterson and Mitloehner Sustainability of the Dairy Industry

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Chapter

Nov 2024

This study measures the sensitivity in total milk production (TMP) due to frequency of climate change in India. TMP of a respective state is considered as an output, while monthly average maximum and minimum temperature, precipitation, and annual actual rainfall are used as climatic factors in empirical investigation. Thereupon, specific agricultural inputs like fertilizer and credit facilities from the banking sector are employed as control variables in the empirical model. The coefficients of independent variables with TMP are observed using a log-linear regression equation. Thereupon, it estimates the predicted milk production of India in different climate change perceptions. Projected results indicate a declining trend in TMP in different climate change perspectives. Irrigated area, credit facilities, gross cropped area and fertilizer application showed a positive impact on TMP. Dairy farmers should adopt appropriate mitigation practices to abate negative impact of climate change on milk production.

Clusters as a tool for improving the efficiency of the dairy industry

Article

Feb 2024

Unbalanced relations between all participants of the food chain in the dairy business hinder the development of the livestock sector. Implementation of cluster policy in dairy cattle breeding enables the development of a competitive reference standard using benchmarking analysis. For the full and comprehensive development of the dairy cluster, it is necessary to observe organisational independence to meet the economic interests of all participants. The developed mechanism acts as the basis of a new area of economic analysis that measures synergetic results possible only within the framework of cluster system economic interaction in dairy cattle breeding.

Towards decarbonizing the supply chain of dairy industry: current practice and emerging strategies

Article

Full-text available

Mar 2025

The food supply chain is currently challenged by the imperative to sustainably feed the increasingly expanding population while simultaneously striving to meet global net-zero emission targets. The dairy sector is widely considered as a carbon-intensive industry, contributing to significant greenhouse gas (GHG) emissions thereby exacerbating global warming. Here, we first summarize recent studies on determining GHG emissions of various dairy products, which suggests that farms are the primary emission hotspots in the dairy supply chain. Next, the vital role of novel techniques and emerging strategies to reduce carbon emissions in the dairy industry is emphasized at both local- and systematic levels. The implementation of targeted techniques at each stage, along with policy initiatives such as carbon pricing, plant-based alternatives, international standards and clean air act, play a vital role in establishing global optimization to mitigate climate warming. Despite these progresses, standards and guidelines of emission reduction for the dairy industry are currently lacking, which calls for continuous efforts to fill the gap. Graphical Abstract

Organic versus Conventional Agriculture: Comparison of Economic and Environmental Sustainability

Article

Full-text available

Jan 2025

Reduction of the level of greenhouse gas emissions from agriculture is one of the most serious issues across the European Union. The dairy industry generates significant emissions from enteric fermentation, manure and long-term storage. The emissions produced depend greatly on factors such as livestock feeding, manure management systems, feed content, and quality. The research aims to evaluate the environmental and economic dimensions of conventional wheat production and dairy farming and compare them in terms of their environmental and economic sustainability. The core element of the sustainability assessment is the construction of the composite sustainability index using data from scientific literature, reports, and statistics. The comparison between organic dairy farming and conventional dairy farming based on sustainability indexes provides valuable insight into the strengths and weaknesses of each system. Organic farming systems present stronger environmental sustainability but require substantial financial support. Organic and traditional farming have their advantages and disadvantages. Policymakers, farmers, and consumers play crucial roles in shaping a future where farming systems can be both productive and sustainable.

Life-Stage Transitions Drive Distinct Gut Viral Communities in Dairy Cattle

Preprint

Full-text available

May 2025

Ruminant gut microbial communities profoundly influence host health and environmental impacts, yet their viral components remain poorly characterised across developmental transitions. Here, we analysed the dairy cow gut virome across four life stages calf, heifer, dry adult, and lactating adult. Using hybrid sequencing, we assembled 30,321 viral operational taxonomic units, including 1,338 complete genomes representing mostly novel lineages. Virome composition shifted dramatically with life stage, transitioning from low-diversity, temperate-dominated communities in calves to high-diversity, lytic-dominated communities in adults. Virome transitions paralleled but showed distinct dynamics from bacterial community development, with viral and bacterial diversity negatively correlated during drying-off. Dry cows exhibited elevated viral loads relative to their bacterial hosts. We identified 26 viral sequences targeting the methanogen Methanobrevibacter, absent in calves but present in adults. These findings reveal the dynamic nature of ruminant gut viral communities and highlight phages' potential regulatory role during critical life transitions.

Developing a tailored sustainable supply chain framework for dairy SMEs in Lithuania using Best-Worst Method

Article

Full-text available

Apr 2025

Sustainable Supply Chain Management (SSCM) plays a vital role in addressing environmental, economic, and social challenges within resource-intensive industries such as dairy production. Despite growing global interest in sustainability, the Baltic region—particularly Lithuania—remains underexplored in terms of localized SSCM frameworks. This study aims to fill this gap by identifying and prioritizing sustainability indicators relevant to Lithuanian dairy companies, using the Best-Worst Method (BWM), a multi-criteria decision-making (MCDM) approach. A total of 15 experts from top-level management positions in the Lithuanian dairy sector were engaged to assess key indicators across three dimensions: environmental, economic, and social. The results reveal that GHG Emissions, Cost Efficiency, and Labor Rights & Fair Conditions are the most critical indicators in their respective dimensions, reflecting both global sustainability priorities and local industry needs. The model also emphasizes the importance of renewable energy, return on investment, and health and safety standards. A sensitivity analysis confirmed the robustness of the BWM results by illustrating how small changes in the top-ranked indicators affect the prioritization of other factors. The study offers a practical decision-support tool for managers and policymakers, providing a clear framework for targeted sustainability strategies in the Lithuanian dairy sector. It also contributes to the academic literature by demonstrating the effectiveness of BWM in regional agri-food supply chains. Recommendations are provided for government support, and future research directions are suggested to expand stakeholder involvement and apply hybrid MCDM models.

From Cow to Climate—Tracing the Path of Dairy Sustainability: Unveiling the Impact on Sustainable Development Goals Through Bibliometric and Literature Analyses

Article

Full-text available

Mar 2025

Archeological evidence shows that dairy farming dates to the early Neolithic era in Europe, the Middle East, Asia, and Africa. Over time, it has evolved from domestication to intensive dairy farms with large, high-tech processing units. Dairy farming has contributed to economic growth, food production, employment, and processing industries. Nonetheless, it has been identified as a major contributor to climate change. This study explores the literature on dairy farming and sustainable development goals (SDGs) to identify current scholarly developments since the formulation and adoption of the SDGs in 2015 and themes for future research. This paper argues that sustainability shortfalls in dairy farming are primarily driven by human processes associated with commercialization and industrialization rather than the animals themselves, although biological emissions remain an inherent factor. Data were analyzed using R package, Excel, NVIVO, and VoS Viewer. A review of the literature showed that dairy farming and its contribution to sustainability has gained more scientific interest since 2015. Moreover, livestock management, feed production and management, stakeholder management, logistics and supply chain management, and waste management are the sources of environmental adversities associated with dairy farming. Notably, these are human processes developed from the commercialization of dairy farming and involve multiple stakeholders across the supply chain. While solutions are embedded within these processes, innovation emerges as a key driver of sustainability and a source of opportunities to strengthen sustainability in the dairy farming sector and achieve SDGs. Sustainability strategies, such as sustainable intensification, multifunctional agriculture, and agro-ecology should be implemented to improve sustainability in the dairy sector.

Enhancing Sustainability in Dairy Industry: Blockchain-Based Waste Reduction

Article

Mar 2025

In recent years, the global demand for dairy products has reached unprecedented levels in the food and beverage market. Despite being produced in large quantities to meet daily needs, high organic content in milk causes it to expire quickly, leading to food waste. Current dairy supply chain management systems lack traceability, auditability, and trust relationships, contributing to the problem. To address this issue, we propose a private Ethereum blockchain-based solution that holds all participants accountable and assesses their actions in a decentralized, auditable, traceable, secure, private, and trustworthy manner. Our system consists of various phases managed by four smart contracts that ensure all involved parties are accountable. We use an events-based approach to ensure traceability and data provenance, where all actions are stored on an immutable ledger in the form of events. By providing a transparent and traceable system, it encourages responsible resource utilization and supports a more sustainable approach to dairy production. We present the system architecture, sequence diagrams, entity-relationship diagrams, and algorithms to explain the working principles of our solution. We also validate the effectiveness of our developed smart contracts and make our smart contract code publicly available on GitHub.

Farm-gate greenhouse gas emission intensity for medium to large New York dairy farms

Article

Mar 2025

From: “It’s just how she walks …” to “… any lameness is a welfare issue” – UK stakeholders’ perspectives on chronic lameness in dairy cows

Article

Feb 2025
J APPL ANIM WELF SCI

Symposium review: Genomic selection for reducing environmental impact and adapting to climate change

Article

Full-text available

Apr 2020

The world has been warming as greenhouse gases accumulate. Worldwide from 1880 to 2012, the average surface temperature has increased by about 0.85°C and by 0.12°C per decade since 1951. The world's cattle population is a contributor to atmospheric methane, a potent greenhouse gas, in addition to suffering from high temperatures combined with humidity. This makes research into reducing the global footprint of dairy cows of importance on a long-term horizon, while improving tolerance to heat could alleviate the effects of rising temperatures. In December 2017, genomic estimated breeding values for heat tolerance in dairy cattle were released for the first time in Australia. Currently, heat tolerance is not included in the Balanced Performance Index (Australia's national selection index), and the correlation between heat tolerance breeding values and Balanced Performance Index is −0.20, so over time, heat tolerance has worsened due to lack of selection pressure. However, in contrast, sizable reductions in greenhouse gas emissions have been achieved as a favorable response to selecting for increased productivity, longevity, and efficiency, with opportunities for even greater gains through selecting for cow emissions directly. Internationally considerable research effort has been made to develop breeding values focused on reducing methane emissions using individual cow phenotypes. This requires (1) definition of breeding objectives and selection criteria and (2) assembling a sufficiently large data set for genomic prediction. Selecting for heat tolerance and reduced emissions directly may improve resilience to changing environments while reducing environmental impact.

Effects of SOP Lagoon Additive on Gaseous Emissions from Stored Liquid Dairy Manure

Article

Full-text available

Feb 2020

Animal manure is a source of greenhouse gas (GHG) emissions and other pollutants and nuisances such as ammonia and odors. There are several technologies to reduce emissions on animal farms including manure additives; however, few have been proven effective and easy to apply to dairy lagoon systems. The present research aimed at testing the ability of the commercial additive “SOP LAGOON” to reduce emissions of GHGs (i.e., carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)), as well as ammonia (NH3) and odors from lagoon stored liquid manure. Emissions of GHGs, NH3 and odors were measured in the laboratory from barrels filled with 65 L of manure treated with SOP LAGOON or left untreated as a control. Manure was collected from a commercial dairy that is located in Solano County, California. Emissions of GHGs and NH3 were continuously measured for one week using flux chambers placed on top of the barrels and connected to a mobile air emissions laboratory. The effects of the untreated control, versus the two respective treatment additive doses of 30.8 and 61.6 g/m³ of manure were compared to each other. The low dose was selected based on the manufacturer recommendation and the high dose was selected by doubling the low dose. Results showed that SOP LAGOON applied at the high dose (61.6 g of SOP LAGOON per m³ of manure) versus the control greatly reduced (p < 0.05) emissions of CO2, CH4, N2O and NH3 by 14.7%, 22.7%, 45.4% and 45.9%, respectively. Furthermore, the high dose of SOP LAGOON treated samples versus the control samples showed less odor intensity (p < 0.05). There was no significant effect of the low dose of SOP LAGOON on the emissions of different gases. The HIGH dose of SOP LAGOON might decrease the number of methanogens and hydrolytic microorganisms and their excreted enzymes during manure storage. Further studies are needed to investigate the mechanism of emission reduction using SOP LAGOON.

Greenhouse gas, water, and land footprint per unit of production of the California dairy industry over 50 years

Article

Full-text available

Feb 2020

Food production including dairy has been associated with environmental impacts and resource use that has been steadily improving when adjusted per unit of product. The objective of this study was to conduct a cradle-to-farm gate environmental impact analysis and resource inventory of the California dairy production system to estimate the change in greenhouse gas emissions and water and land use over the 50-yr period between 1964 and 2014. Using a life cycle assessment according to international standards and the Food and Agriculture Organization of the United Nations guidelines, we analyzed contributions from dairy production in California to global environmental change. Production of 1 kg of energy- and protein-corrected milk (ECM) in California emitted 1.12 to 1.16 kg of CO2 equivalents (CO2e) in 2014 compared with 2.11 kg of CO2e in 1964, a reduction of 45.0 to 46.9% over the last 50 yr, depending on the model used. Greater reductions in enteric methane intensity (i.e., methane production per kilogram of ECM) were observed (reduction of 54.1 to 55.7%) compared with manure GHG (reduction of 8.73 to 11.9%) in 2014 compared with 1964. This was mainly because manure management in the state relies on lagoons for storage, which has a greater methane conversion factor than solid manure storage. Water use intensity was reduced by 88.1 to 89.9%, with water reductions of 88.7 to 90.5% in crop production, 55.3 to 59.2% in housing and milking, and 52.4 to 54% in free water intake. Improved crop genetics and management have contributed to large efficiencies in water utilization. Land requirements for crop production were reduced by 89.4 to 89.7% in 2014 compared with 1964. This was mainly due to dramatic increases in crop yields in the last 50 yr. The increases in milk production per cow through genetic improvements and better nutrition and animal care have contributed to reductions in greenhouse gas emissions and land and water usage when calculated per unit of production (intensity) basis.

The effects of improved performance in the U.S. dairy cattle industry on environmental impacts between 2007 and 2017

Article

Full-text available

Oct 2019

The U.S. dairy industry considerably reduced environmental impacts between 1944 and 2007, primarily through improved dairy cow productivity. However, although milk yield per cow has increased over the past decade, whole-system environmental impact analyses have not been conducted over this time period, during which environmental modeling science has improved considerably. The objective of this study was to compare the environmental impact of U.S. dairy cattle production in 2007–2017. A deterministic model based on population demographics, metabolism, and nutrient requirements of dairy cattle was used to estimate resource inputs, nutrient excretion, and greenhouse gas (GHG) emissions per 1.0 × 106 t (one million metric t or MMT) of energy-corrected milk (ECM) produced in 2007 and 2017. System boundaries extended from the manufacture and transport of cropping inputs to milk at the farm gate. Milk transport, processing, and retail were not included. Dairy systems were modeled using typical management practices, herd population dynamics, and production data from U.S. dairy farms. Cropping data were sourced from national databases. The resources required to produce 1.0 MMT ECM in 2017 were considerably reduced relative to those required in 2007, with 2017 production systems using 74.8% of the cattle, 82.7% of the feedstuffs, 79.2% of the land, and 69.5% of the water as compared to 2007. Waste outputs were similarly reduced, with the 2017 U.S. dairy industry producing 79.4%, 82.5%, and 85.7% of the manure, N, and P excretion, respectively. Dairy production in 2017 emitted 80.9% of the CH4 and 81.5% of the N2O per 1.0 MMT ECM compared to 2007. Enteric and manure emissions contributed the major proportion (80%) of GHG emissions per unit of milk, with lesser contributions from cropping (7.6%) and fertilizer application (5.3%). The GHG emissions per 1.0 MMT ECM produced in 2017 were 80.8% of equivalent milk production in 2007. Consequently, although total U.S. ECM production increased by 24.9% between 2007 and 2017, total GHG emissions from this milk production increased by only 1.0%. In line with previous historical analyses, the U.S. dairy industry has made remarkable productivity gains and environmental progress over time. To maintain this culture of continuous improvement, the dairy industry must build on gains made to date and demonstrate its commitment to reducing environmental impacts while improving both economic viability and social acceptability.

Methanogenesis in animals with foregut and hindgut fermentation: a review

Article

Full-text available

Sep 2019

Methane is the main greenhouse-gas contributor to global warming in the livestock sector; it is generated by anaerobic fermentation in the different sections of the gut, and the methane concentration differs significantly among species. Methane is produced only by certain types of microorganisms called methanogens. The species composition of methanogenic archaea population is largely affected by the diet, geographical location, host and the section of the gut. Consequently, methane production, either measured as total grams emitted per day or per bodyweight mass, differs greatly among animal species. The main difference in methanogenic activity among different gut sections and animal species is the substrate fermented and the metabolic pathway to complete anaerobic fermentation of plant material. The three main substrates used by methanogens are CO2, acetate and compounds containing methyl groups. The three dominant orders of methanogens in gut environments are Methanomicrobiales, Methanobacteriales and Methanosarcinales. They normally are present in low numbers (below 3% of total microbiome). The present review will describe the main metabolic pathways and methanogens involved in CH4 production in the gut of different host-animal species, as well as discuss general trends that influence such emissions, such as geographical distribution, feed composition, section of the gut, host age and diurnal and season variation. Finally, the review will describe animal species (large and small domestic ruminants, wild ruminants, camelids, pigs, rabbits, horses, macropods, termites and humans) specificities in the methanogen diversity and their effects on methane emission.

Improving the Sustainability of Dairy Slurry by A Commercial Additive Treatment

Article

Full-text available

Sep 2019

Ammonia (NH3), methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) emissions from livestock farms contribute to negative environmental impacts such as acidification and climate change. A significant part of these emissions is produced from the decomposition of slurry in livestock facilities, during storage and treatment phases. This research aimed at evaluating the effectiveness of the additive “SOP LAGOON” (made of agricultural gypsum processed with proprietary technology) on (i) NH3 and Greenhouse Gas (GHG) emissions, (ii) slurry properties and N loss. Moreover, the Life Cycle Assessment (LCA) method was applied to assess the potential environmental impact associated with stored slurry treated with the additive. Six barrels were filled with 65 L of cattle slurry, of which three were used as a control while the additive was used in the other three. The results indicated that the use of the additive led to a reduction of total nitrogen, nitrates, and GHG emissions. LCA confirmed the higher environmental sustainability of the scenario with the additive for some environmental impact categories among which climate change. In conclusion, the additive has beneficial effects on both emissions and the environment, and the nitrogen present in the treated slurry could partially displace a mineral fertilizer, which can be considered an environmental credit.

Influence of diet and manure management on ammonia and greenhouse gas emissions from dairy barns

Article

Full-text available

Jun 2019

Dairy systems are a source of pollutant emissions, such as greenhouse gases ( GHG ) and NH 3 that are associated with impacts on the environment. Gas emissions in barns are related mainly to diet intake and chemical composition, N excretion and manure management. A reduction in dietary N is known to be an effective way to reduce N excretion and the resulting NH 3 emissions. However, most studies consider manure in liquid form with frequent removal from the barn. In deep litter systems, several processes can occur during the accumulation of solid manure that result in variable gas emissions. The objective of this experiment was to investigate the influence of the interaction between dietary CP (low or high) and manure management (liquid or solid) on gas emissions (NH 3 , N 2 O, CH 4 ) at the barn level. Dietary treatments provided either low ( LowN ; 12% CP) or high ( HighN ; 18% CP) degradable protein to modify the amount of total ammonia nitrogen ( TAN ) excreted. The cows were housed for two 8-week periods in two mechanically ventilated rooms equipped to manage manure either in liquid ( LM ; slurry) or solid form ( SM ; deep litter). In the LM treatment, N balance was measured for 4 days. As expected, animals fed the LowN diet ingested 35% less N and excreted 65% less N in their urine, with no reduction in faecal N excretion and N secretion in milk. On the LowN diet, excretion of urea-N and NH 3 -N emissions were reduced regardless of the manure management. On the HighN diet, urinary urea-N excretion was three times as high, while NH 3 -N emissions were 3.0 and 4.5 times as high in LM and SM, respectively. Manure management strongly influenced CH 4 -C emissions, which were 30% higher in SM than in LM, due to the accumulation of litter. Moreover, gas emissions from solid manure increased over the accumulation period, except for NH 3 on the LowN diet. Finally, our results suggest that methods used for national inventories would become more accurate by considering the variability in TAN excretion, which is the primary factor that influences NH 3 emissions.

Effects of a blend of essential oils on milk yield and feed efficiency of lactating dairy cows

Article

Full-text available

Jun 2019

Objective Our objective was to assess the effect on milk yield and feed efficiency of a combination of essential oils (eugenol, geranyl acetate, and coriander). Materials and Methods Forty-eight Holstein cows (621 ± 61.3 kg of BW and 167 ± 83.8 DIM, 15 primiparous and 33 multiparous) were allocated to 2 treatments for 8 consecutive weeks in a completely randomized design. Treatments consisted of no supplementation (CTRL) or supplementation (AGL) of 1 g/d of Agolin Ruminant (Agolin, Bière, Switzerland) in the TMR. All cows were fed a common TMR (just differing in the presence or absence of Agolin Ruminant) twice daily. Milk production, milk composition, and feed intake of individual cows were recorded daily, and feed efficiency was calculated. Rumen fluid samples were collected from all cows throughout the study to determine pH and VFA profile and estimate methane concentrations. Results and Discussion Compared with CTRL, cows fed AGL produced more ECM after 4 wk of exposure to treatments, and because DMI did not differ between treatments, feed efficiency increased over time. Estimated rumen methane concentrations of cows fed AGL were lower compared with those fed CTRL during wk 4 to 8. Implications and Applications It is concluded that Agolin Ruminant increased milk production and feed efficiency after 4 wk of feeding the additive. This improvement could be attributed to a marginal improvement of rumen fermentation as indicated by decreases in in vitro estimates in rumen methane production.

Introduction and Executive Summary of the Supplement, Role of Milk and Dairy Products in Health and Prevention of Noncommunicable Chronic Diseases: A Series of Systematic Reviews

Article

Full-text available

May 2018

Milk and dairy products contain multiple nutrients and contribute significantly to meet the nutritional requirements for protein, calcium, magnesium, phosphorus, potassium, zinc, selenium, vitamin A, riboflavin, vitamin B-12, and pantothenic acid. However, consumption of dairy is decreasing and moving away from the advised level in many countries and the potential benefits of milk and dairy products for health have come under question. This, in spite that numerous studies report health benefits associated with dairy consumption. The present supplement aims to assess and summarize scientific evidence regarding the impact of dairy intake on health and all-cause mortality, and on the prevention of diverse chronic diseases, mainly from meta-analyses of observational studies and randomized controlled trials (RCTs). There seem to positive associations between moderate maternal milk intake during pregnancy and infant birth weight, length and bone mineral content during childhood. Moreover, consumption of dairy products in older subjects may reduce the risk of frailty and decrease the risk for sarcopenia. The highest consumption of dairy products did not show a clear association with total osteoporotic fracture and hip fracture risk; however, a diminished risk of vertebral fracture was found. Analysis of the differences between high and low dairy consumption and for dose-response found no association between dairy product consumption and risk of all-cause mortality. Total and low-fat dairy consumption is associated with a reduced risk of developing metabolic syndrome and current evidence supports that consumption of dairy does not adversely affect the risk of cardiovascular outcomes and may even have a subtle protective effect. Moreover, evidence has been provided of an inverse association between the consumption of dairy products and ischemic heart disease and myocardial infarction. Also, the evidence suggests that dairy consumption, particularly low-fat dairy and yogurt is associated with a lower risk of type 2 diabetes. Likewise, moderate compared with medium consumption of dairy is associated lower risk for colorectal and bladder cancer and has no association with prostate cancer. Finally, consumption of milk or dairy products did not show a proinflammatory effect on healthy subjects, overweight/obese individuals, or individuals with other metabolic abnormalities, and fortification of dairy products with phytosterols and ω-3 fatty acids seems to be a good approach to improve cardiometabolic risk biomarkers. In conclusion, the systematic reviews and meta-analyses of the present supplement support adequate milk consumption at various stages of life and in the prevention/control of various noncommunicable chronic diseases.

Effect of biochar and bacterial inoculum additions on cow dung composting

Article

Nov 2019
BIORESOURCE TECHNOL

The present study evaluates the effectiveness of different types of biochar additives and bacterial inoculation on gaseous emission, nutrient preservation, and relevant functional bacterial community during cow manure composting. The result revealed that biochar and bacterial consortium inoculation effectively inhibited gaseous emission and improved carbon and nitrogen sequestration, remarkably enriching the abundance of the functional bacteria community. Notably, superior efficacy was found in 12% wheat straw biochar and bacterial consortium amendment composting of T6 with the lowest cumulative CO2-C and NH3-N (308.02 g and 12.71 g, respectively), minimal total C and N losses, and the highest bacterial population. Additionally, gaseous emission exhibited a strong correlation between physicochemical properties with intersection of 66.78% and a unique substrate utilizing bacterial communities. Consequently, the integrated application of biochar and bacterial consortium inoculation was suggested as an efficient method to adjust microbial activity and facilitate cellulose-rich waste degradation, enabling efficient management of organic waste from cow manure and wheat straw by composting.

Sustainability of the Dairy Industry: Emissions and Mitigation Opportunities

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