
S.R.O. WilliamsDepartment of Energy, Environment and Climate Action
S.R.O. Williams
Bachelor of Engineering (Agric.), Master of Engineering Science
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Introduction
Skills and Expertise
Additional affiliations
August 1993 - December 1995
July 2013 - December 2014
Publications
Publications (101)
Dairy products are a key source of valuable proteins and fats for many millions of people worldwide. Dairy cattle are highly susceptible to heat-stress induced decline in milk production, and as the frequency and duration of heat-stress events increases, the long term security of nutrition from dairy products is threatened. Identification of dairy...
The methods for estimating methane emissions from cattle as used in the Australian national inventory are based on older data that have now been superseded by a large amount of more recent data. Recent data suggested that the current inventory emissions estimates can be improved. To address this issue, a total of 1034 individual animal records of d...
The sulphur hexafluoride (SF6) tracer technique enables determination of enteric methane emissions from large numbers of individual ruminant animals. The objective of this research was to identify and correct substantial errors within the SF6 technique. Six experiments were undertaken using respiration chamber, laboratory or SF6 techniques. Experim...
Automated measurements of the ratio of concentrations of methane and carbon dioxide, [CH4]:[CO2], in breath from individual animals (the so-called "Sniffer-technique") and estimated CO2 production can be used to estimate CH4 production, provided that CO2 production can be reliably calculated. This would allow CH4 production from individual cows to...
Short-chain fatty acids (SCFA) and lactate in ruminal fluid are products resulting from the microbial fermentation of substrates and can be used to reflect the composition and activity of the ruminal microbiome. Determination of SCFA and D-/L-lactate in ruminal fluid currently requires two separate protocols, which is time-consuming and costly. In...
Dry matter intake (DMI) is a primary determinant of milk production in grazing dairy cows and an ability to measure the DMI of individual cows would allow herd managers to formulate supplementary rations that consider the amount of nutrients ingested from grass. The 2 related aims of this experiment were to define the mean number of swallowed boli...
Using direct-fed microbials to mitigate enteric methane emissions could be sustainable and acceptable to both consumers and producers. Forty lactating, multiparous, Holstein-Friesian cows were randomly allocated one of two treatments: (1) a base of ad libitum vetch (Vicia sativa) hay and 7.0 kg DM/d of a grain mix, or (2) the basal diet plus 10 mL...
The frequency, duration, and intensity of heat waves in Australia are increasing. To reduce the impact of heat waves on milk production, novel management strategies are required. Altering the forage type and amount offered affect the heat load on dairy cows and offer potential strategies to ameliorate the effects of hot weather. Thirty-two multipar...
The production of methane by the rumen microbiota is a complex biological process. When tackling the modelling of methane production, the modeller decides what complexity is needed to answer the scientific question for which the model is intended. Such a choice results in a diversity of possible models spanning both empirical and mechanistic approa...
Cereal grains that differ in the rate and extent of ruminal fermentation differ in heat increment and may be used to improve thermoregulation during heat stress. This experiment investigated the responses of dairy cows in late lactation to a heat challenge when offered wheat-grain or corn-grain. Eighteen lactating cows, 220 ± 94 (mean ± standard de...
Fermentation of pasture grasses and grains in the rumen of dairy cows and other ruminants produces methane as a by-product, wasting energy and contributing to the atmospheric load of greenhouse gasses. Many feeding trials in farmed ruminants have tested the impact of dietary components on feed efficiency, productivity and methane yield (MeY). Such...
Ex ante economic analysis can be used to establish the production threshold for a proposed experimental diet to be as profitable as the control treatment. This study reports (1) a pre-experimental economic analysis to estimate the milk production thresholds for an experiment where dietary supplements were fed to dairy cows experiencing a heat chall...
Supplementing the diet of lactating cows with ingredients that increase energy density, or reduce internal heat production, may reduce some of the negative impacts of hot weather on milk yield. Thirty-two dairy cows were assigned either: (1) basal diet only, (2) basal diet plus canola oil, (3) basal diet plus betaine, or (4) basal diet plus canola...
The RumiWatch System (Itin+Hoch GmbH, Liestal, Switzerland) is a sensor system that enables quantification of ingestive behaviors of cattle that may be useful, amongst other things, for estimating dry matter intake. There are currently multiple versions of the RumiWatch Converter software used to convert the recorded data into specific animal behav...
Selecting for lower methane (CH4) emitting animals is one of the best approaches to reduce CH4 given that genetic progress is permanent and cumulative over generations. As genetic selection requires a large number of animals with records and few countries actively record CH4, combining data from different countries could help to expedite accurate g...
Despite the fact that the sulphur hexafluoride (SF6) tracer technique was developed over 25 years ago to measure methane production from grazing and non-housed animals, no studies have specifically investigated whether ambient wind speed, temperature, relative humidity and rainfall influence the accuracy of the method. The aim of this research was...
The natural behavior of animals can be disrupted by the techniques and materials of research methodologies. This study aimed to evaluate the effect of the equipment used in the SF6 tracer technique to estimate enteric methane emissions on the behavior of lactating dairy cows. The cows (n = 24) were allocated to one of two diets: CONTROL and experim...
Several methods have been developed for measurement or estimation of CH4 emissions from individual animals, including the SF6 (sulphur hexafluoride) tracer gas technique. With the SF6 technique, CH4 emissions can be continuously measured, as in respiration chambers, but the method can be used with free roaming animals (e.g. group-housed and grazing...
The winter diet of dairy cows in Mediterranean climate regions is usually a total mixed ration with a base of conserved summer crops such as corn silage and alfalfa hay. However, there is increased labor and financial cost related to this kind of feeding, which could be reduced if fresh forages were used in place of some of the conserved forage in...
Methane is a greenhouse gas of high interest to the dairy industry, with 57% of Australia's dairy emissions attributed to enteric methane. Enteric methane emissions also constitute a loss of approximately 6.5% of ingested energy. Genetic selection offers a unique mitigation strategy to decrease the methane emissions of dairy cattle, while simultane...
Globally, annual production of grape marc (GM), the residue of skins, seeds and stems remaining after making wine, has been estimated to be approximately nine million tonnes. No previous studies have compared effects on milk production and methane emissions when GM from either red or white grapes was fed to dairy cows. This experiment examines the...
Addition of fats to the diets of ruminants has long been known to result in a reduction in enteric methane emissions. Tannins have also been used to reduce methane emissions but with mixed success. However, the effect of feeding fat in combination with tannin is unknown. Eight ruminally cannulated Holstein-Friesian cows were fed four diets in a dou...
Wheat is the most common concentrate fed to grazing dairy cows in Australia, but no studies have examined the effects of wheat proportion in a pasture-based diet on milk production and methane emissions. In this 47-d experiment, 32 Holstein dairy cows were offered 1 of 4 diets during d 1 to 36. Cows in each of the dietary treatment groups were indi...
The dry matter intake (DMI) of forage-fed cattle can be used to predict their methane emissions. However, many cattle are fed concentrate-rich diets that decrease their methane yield. A range of equations predicting methane yield exist, but most use information that is generally unavailable when animals are fed in groups or grazing. The aim of this...
Enteric methane emitted by ruminants is a nutritional inefficiency that contributes to global warming. Feeding substantial quantities of wheat grain to dairy cows has been reported to decrease enteric methane emissions compared with other feeds. Feeding methane mitigating agents such as nitrate, fat and 3-nitrooxypropanol (3-NOP) to ruminants have...
Diets that contain high proportions of either wheat or supplementary fat have been individually reported to reduce enteric methane production. The objective of this research was to determine the effect of dietary fat supplementation on methane emissions and milk yield from cows fed diets containing either corn or wheat grains. It was hypothesized t...
BACKGROUND
Supplementation of ruminant diets with wheat and corn grains influences ruminal fermentation. In vitro fermentation is a methodology that can be used to screen feeds for their potential to produce enteric methane. However, there is evidence that the diet of the donor cows could impact the results of in vitro analysis. This research inves...
In previous studies using Ankom GP vented in vitro systems (Ankom Technology, Macedon, NY), methane production was estimated from gas production (GP) and a single gas sample from the incubation vessel's headspace at the end of the incubation. An accurate method requires measurement of methane in the incubation vessel's headspace and in the gases ve...
There has been little research that has quantified methane (CH4) yields when dairy cows consume diets containing wheat grain. Furthermore, although rumen-fistulated animals have been used in many experiments concerned with measuring CH4 emissions, no research has examined the effect of rumen fistulation on in vivo CH4 emissions and yield. This expe...
Short-term studies have shown that feeding dairy cows diets containing a high proportion (>40%) of wheat may result in reduced milk fat concentration and reduced CH4 emissions (g of CH4/cow per d), but no long-term studies have been done on these responses. This study compared the milk production and CH4 responses when 24 dairy cows were fed diets...
Almond hulls and citrus pulp have been fed to dairy cows with variable responses for milk production, but no information exists on their effect on enteric methane emissions. This experiment examined the effects of dietary supplementation with either almond hulls or ensiled citrus pulp on the milk yield, milk composition, and enteric methane emissio...
Wheat is the most common concentrate fed to dairy cows in Australia, but few studies have examined the effects of wheat feeding on enteric methane emissions, and no studies have compared the relative potencies of wheat, corn, and barley for their effects on enteric methane production. In this 35-d experiment, 32 Holstein dairy cows were offered 1 o...
There is a need to develop simple, accurate methods for predicting methane emissions, yields and intensities of dairy cows. Several studies have focussed on the relationship between the concentrations of trans-10 plus trans-11 C18:1 fatty acids in milk fat and methane yield. The aim of the present study was to perform a meta-analysis to quantify re...
Holstein–Friesian dairy cows managed in pasture-based systems are capable of lactating for considerably longer than the traditional 300 days. However, the partitioning of dietary nutrients in the second 300 days of an extended lactation has been shown to be different from that in the first 300 days. The partitioning of dietary nitrogen (N) was inve...
The objective of the present research was to describe the physiological and production responses of lactating dairy cows during and after sudden exposure to temperate-climate heat-wave conditions, compared with cows in thermoneutral conditions. Twelve lactating multiparous Holstein–Friesian dairy cows were housed in controlled-climate chambers for...
Residual feed intake (RFI) is the difference between an animal’s actual and expected feed intake. Two experiments were conducted comparing energy and nitrogen partitioning in mid-lactation, in Holstein–Friesian cows selected for high or low RFI measured previously as growing calves. Each experiment used 16 cows (8 high-RFI and 8 low-RFI); the first...
Scientific Reports 6 : Article number: 34114; 10.1038/srep34114 published online: 29 September 2016 ; updated: 19 January 2017 . The original version of this Article omitted an affiliation for J. B. Garner.
The objective of this study was to compare 2 commonly used techniques for measuring methane emissions from ruminant animals: the GreenFeed (GF) system and the sulfur hexafluoride (SF6) technique. The study was part of a larger experiment in which a methane inhibitor, 3-nitrooxypropanol, fed at 4 application rates (0, 40, 60, and 80 mg/kg of feed dr...
Powerpoint presentation available for download.
Forage brassica and chicory crops provide an alternative to perennial grass pastures as a forage supply for grazing dairy cows during summer, but there is little information about their effects on milk production and methane (CH4) emissions. Thirty-two Holstein–Friesian cows were fed for 10 days on a diet of lucerne cubes (750 g/kg DM) and grain (2...
This review examines research aimed at reducing enteric methane emissions from the Australian dairy industry. Calorimeter measurements of 220 forage-fed cows indicate an average methane yield of 21.1 g methane (CH4)/kg dry matter intake. Adoption of this empirical methane yield, rather than the equation currently used in the Australian greenhouse g...
Significance
Methane from enteric fermentation in the ruminant digestive system is a major contributor to anthropogenic greenhouse gas emissions in the United States and worldwide. Methane is also a net loss of feed energy to the animal. This study was undertaken to investigate the effect of a methane inhibitor on enteric methane emissions from lac...
This study investigated the effect of a CH4 inhibitor, 3-nitrooxypropanol (3NOP), on enteric CH4 emissions in lactating Holstein cows. The experiment was a randomized block design with 48 cows (DIM, 77 ± 3.9; lactations, 2.2 ± 0.15), with a 2-wk covariate and a 12-wk data collection periods. Treatments were: control (no additive) and 3NOP applied a...
The sulphur hexafluoride (SF6) technique used to estimate methane emissions from ruminants involves placement of a permeation tube into the reticulo-rumen of animals. The permeation tube releases a trace amount of SF6 across a polytetrafluoroethylene membrane. The animals emit in exhaled breath enteric methane along with a trace amount of the SF6 g...
Dairy products are the single largest commodity exported from south east Australia. However, dairy farming contributes 12% of Australia's national greenhouse gas emissions. During the last nine years, the Australian Federal Government and the Victorian State Government have funded considerable research towards mitigating greenhouse gas emissions fr...
Dairy cows in Australia commonly graze pastures dominant in perennial ryegrass (Lolium perenne) and, on average, are also fed 6.0 kg DM/day of concentrate feed supplement, much of which is cereal grains. However, there has been little research published on methane production from dairy cows when wheat grain is included in a pasture diet. Sixteen la...
Grape marc is the skins, seeds and stems remaining after grapes (Vitis vinifera) have been pressed to make wine and is increasingly being used as a source of nutrients (fibre and oil) for dairy cows. Grape marc has been shown to be a methane mitigant when consumed by dairy cows on a conserved forage diet in late summer. Thirty-two Holstein-Friesian...
Forage brassica and chicory are alternatives to summer pasture. However, there is little information available on the effect of diets containing forage brassica or chicory on milk production from dairy cows, especially under the hot and dry Australian conditions. Thirty-two Holstein Friesian cows were fed for 10 days on a diet dominant in lucerne h...
There has been growing interest in the inclusion of almond hulls and citrus pulp in the diet of Australian dairy cows during summer when pasture availability is limited and digestibility is low. However, there is little information on the resulting milk production response. Thirty-two Holstein Friesian cows were offered one of three diets (lucerne...
Methane (CH4) emissions from dairy cows are technically difficult and expensive to measure. Recently, some researchers have found correlations between the concentrations of specific fatty acids in milk fat and the CH4 emissions from cows that could obviate the need for direct measurement. In this research, data on individual cow CH4 emissions and c...
This study aimed to evaluate the effect of organic acids on in vitro fermentation characteristics. Four organic acids (tartaric, malic, fumaric and citric) and their enantiomers (L-tartaric, D-tartaric, DL-tartaric, L-malic and DL-malic) were analysed using in vitro batch culture incubations, at four concentrations (0, 5, 10 and 15 mM). Cumulative...
Grape marc (the skins, seeds, stalk, and stems remaining after grapes have been pressed to make wine) is currently a by-product used as a feed supplement by the dairy and beef industries. Grape marc contains condensed tannins and has high concentrations of crude fat; both these substances can reduce enteric methane (CH4) production when fed to rumi...
Predictable release of sulphur hexafluoride (SF6) tracer gas from permeation tubes into the reticulo-rumen is necessary to estimate methane emissions from ruminants using the SF6 tracer technique. Any discrepancy between the laboratory determined rate of SF6 release from permeation tubes and the actual rate of release in the reticulo-rumen would bi...
Ruminants produce large quantities of methane in their rumen as a by-product of microbial digestion of feed. Antibiotics are added to ruminant feed to reduce wasteful production of methane, however this practise has some downsides. A search for safer and natural feed additives with anti-methanogenic properties is underway. The objective of this res...
This experiment was conducted to determine the effects of diets supplemented with cottonseed oil, Acacia mearnsii-condensed tannin extract, and a combination of both on composition of bovine milk. Treatment diets included addition of cottonseed oil (800 g/d; CSO), condensed tannin from Acacia mearnsii (400 g/d; TAN) or a combination of cottonseed o...
Purpose
To consider whether feed supplements that reduce methane emissions from dairy cows result in a net reduction in greenhouse gas (GHG) intensity when productivity changes and emissions associated with extra manufacturing and management are included.
Methods
A life cycle assessment was undertaken using a model farm based on dairy farms in Vic...
Genetic selection has been proposed as a permanent and cumulative strategy to reduce the emissions of methane from domesticated ruminants. However, selecting for low methane could have undesirable effects on milk composition. To test for this, 120 multiparous Holstein-Friesian cows were offered a single mixed ration for 32 days and methane measured...
Predictable release of sulphur hexafluoride (SF6) from permeation tubes is critical for determination of enteric methane emissions from ruminants using the calibrated tracer technique. Experiments comparing respiration chambers and the SF6 technique indicate
that prolonged deployment of SF6 tubes causes overestimation of methane emissions. We repor...
Respiration chambers and the sulphur hexafluoride (SF6) tracer technique are commonly used to determine
methane (CH4) emissions from individual animals. Chambers provide an accurate CH4 measurement but are expensive to build and operate. The SF6 tracer technique provides an indirect method for estimating emissions from individual cows and can be us...