
Ian John LeanThe University of Sydney · Faculty of Veterinary Science
Ian John Lean
BVSc, PhD, DVSc, MANZCVS
About
267
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Introduction
Pathobiology of the high producing dairy cow
Ruminal acidosis
The geriatric cow
Meat quality - Meat Standards Australia
Additional affiliations
Scibus Australia
Position
- Managing Director
June 1986 - June 1990
Publications
Publications (267)
In Australia, dystocia is responsible for 53% of lamb mortalities, and calcium deficiencies may be a contributing factor. A negative dietary cation anion difference (DCAD) diet can increase calcium concentrations in sheep. Therefore, this study aimed to investigate the effects of a negative DCAD diet on metabolic state, mineral status and parturiti...
Each year in Australia, 53% of lamb mortalities are attributed to dystocia, with subclinical maternal calcium deficiencies likely contributing to dystocia rates. A negative dietary cation and anion difference (DCAD) diet has increased circulating calcium in sheep. Therefore, this study aimed to investigate the effects of supplementing twin-bearing,...
Simple Summary
Mineral metabolism is altered with the onset of lactation, and a reduction in concentrations of calcium (Ca) in blood, particularly when it persists for days, is associated with increased risk of peripartum diseases. Hypocalcemia affects immune function, which seems to underlie the susceptibility to other diseases. Hypocalcemia is no...
Objective: Our objective was to evaluate model structure choice on estimates of efficiency, based on residual feed intake, and thereby cattle profitability. Materials and Methods: Efficiencies were compared for 2 models using data from 7 studies (509 cattle). Model 1 DMI were estimated using ordinary least squares as f(ADG and BW 0.750). Model 2 wa...
Diets that provide a negative dietary anion cation difference (DCAD) and supplement with a vitamin D metabolite 25-OH-D3, (calcidiol) may increase calcium availability at parturition, enhance piglet survival and performance. This factorial study assessed effects of DCAD, calcidiol (50 µg/kg), and parity (parity 1 or >1) and their interactions. Larg...
Background
Milk provides a readily available diagnostic fluid collected daily or more frequently on an individual animal or herd basis. Milk, as an aggregated sample in bulk tank milk (BTM) represents the status of a herd instead of a single animal. In this review, we examine the potential for milk to predict risks to efficient production, reproduc...
Introduction
Early-lactation Holstein cows ( n = 261) from 32 herds in three regions (Australia, California, and Canada) were previously categorized using a discriminant analysis model as being at a high (26.1% of cows), medium (26.8% of cows), or low risk (47.1% of cows) of ruminal acidosis. We aimed to investigate if (1) risk of acidosis would be...
The objective of this study was to improve understandings of the rumen microbial ecosystem during ruminal acidosis and responses to feed additives to improve prudent use strategies for ruminal acidosis control. Rumen bacterial and archaeal community composition (BCC) and its associations with rumen fermentation measures were examined in Holstein he...
Design and management of dairy feedpads and housing
While mineral requirements do not differ with the production systems, the forage bases of the different dairy production systems influence the risk of mineral deficiency. Testing representative pastures on a farm is a key to understanding the potential for risk of mineral deficiency and should be combined with blood or tissue samples, clinical obse...
It is clear that the societal role of meat is being challenged with ideological and simplified logic without substantiation from robust data-driven science. With this background, the international summit titled ‘The societal role of meat – what the science says’ was held in Dublin, Ireland, during October 2022, to provide evidence-based evaluations...
Three hundred and two parity 3 and 4 sows were allocated to one of three treatment groups: A (n=106): Control group fed the standard lactation diet; B (n=94): Lactation diet supplemented with 10 kg BioChlor/T; C (n=102): Lactation diet supplemented with 20 kg BioChlor/T. The sows were randomly allocated to treatment on entry to the farrowing shed a...
A multicenter observational study to evaluate genome-wide association was conducted in early-lactation Holstein cows (n = 293) from 36 herds in Canada, the USA, and Australia. Phenotypic observations included rumen metabolome, acidosis risk, ruminal bacterial taxa, and milk composition and yield measures. Diets ranged from pasture supplemented with...
A multicenter observational study was conducted on early lactation Holstein cows (n = 261) from 32 herds from 3 regions (Australia, AU; California, CA; and Canada, CAN) to characterize their risk of acidosis into 3 groups (high, medium, or low) using a discriminant analysis model previously developed. Diets ranged from pasture supplemented with con...
We conducted a retrospective meta-analysis based on individual cow data to assess the associations of parity, level of production, and pasture-based or intensively fed systems with fertility. Our goal was to provide understandings of the role of parity in risks for removal and reproductive failure. Multilevel models were used to evaluate the fixed...
We conducted a retrospective meta-analysis based on individual cow data to assess the associations of parity, level of production, and pasture-based or intensively fed systems with fertility. Our goal was to provide understandings of the role of parity in risks for removal and reproductive failure. Multilevel models were used to evaluate the fixed...
Data were obtained from studies in Australia, Canada, and the United States using individual cow data from 28,230 Holstein cows to evaluate associations between parity and disease. Our goal was to develop understanding of disease risks for cows of differing parity. We hypothesized that there would be increased risks of disease and changes in metabo...
Body condition scoring (BCS) and body weight (BW) are observations associated with labile tissue reserves, health, and reproduction efficiency of dairy cows. The effect of parity (1 through to ≥5) and feeding system (pasture-based and TMR) on BCS and BW were evaluated utilizing raw data sets from 16 retrospective studies that totaled 24,807 Holstei...
Probiotics are widely used in commercial shrimp aquaculture, but responses are variable. The objectives of this study were to quantitatively review using meta-analysis the production, survival, and immune responses of Macrobrachium rosenbergii to probiotics and to identify sources of residual variation. A total of 58 comparisons from 16 experiments...
Objectives of analyses conducted were to quantitatively review using meta-analysis the production, survival, and immune responses of shrimp to probiotics, and to identify sources of residual variation. A total of 277 comparisons from 89 experiments were included in the final meta-analyses. Data were analysed as 3 databases on interventions with: (1...
There has been considerable interest in the use of red seaweed, and in particular Asparagopsis taxiformis, to increase production of cattle and to reduce greenhouse gas emissions. We hypothesized that feeding seaweed or seaweed derived products would increase beef or dairy cattle performance as indicated by average daily gain (ADG), feed efficiency...
Background
Marked increases in atmospheric CO2 concentrations are largely associated with the release of sequestered carbon in fossil fuels. While emissions of green‐house gasses (GHG) from cattle have significant global warming potential, these are biogenic sources and substantially involve carbon in natural cycles, rather than fossil fuel. Cattle...
This study assessed the capacity of magnesium supplementation to reduce muscle glycogen loss, ultimate pH and increase plasma magnesium in pasture fed slaughter cattle. Beef cattle (n = 1075) from 14 farms were supplemented with or without magnesium pellets for 7–14 days prior to slaughter. Magnesium was allocated at 9.83 g of elemental magnesium p...
The objective of this clinical trial was to evaluate the effectiveness of probiotic, prebiotic, and synbiotic supplementation on average daily weight gain (ADG), duration of diarrhea, age at incidence of diarrhea, fecal shedding of Cryptosporidium oocysts, enteric pathogens, and the odds of pneumonia in preweaning dairy heifer calves on a commercia...
There has been considerable interest in the use of red seaweed, and in particular Asparagopsis taxiformis, to increase production of cattle and to reduce greenhouse gas emissions. We hypothesized that feeding seaweed or seaweed derived products would increase beef or dairy cattle performance as indicated by average daily gain (ADG), feed efficiency...
We hypothesized that feeding 25-hydroxyvitamin D3 [25-(OH)D3] during lactation and prepartum in conjunction with negative dietary cation-anion difference diets would improve milk production, increase the probability of pregnancy, and reduce the incidence of postcalving diseases. Cows from 4 dairies with prepartum transition diets negative in dietar...
The Chapter describes the beef market in Australia
The objective of this clinical trial was to evaluate the effectiveness of pro, pre and symbiotic supplementation on average daily weight gain (ADG), diarrhea length, age at incidence of diarrhea, shedding of Cryptosporidium oocysts, enteric pathogens, and the odds of pneumonia in pre-weaned dairy heifer calves on a commercial dairy
Objective
Our objectives were to evaluate milk production and constituent responses to changes in the diet for pens of cows over time and whether differences in response were attributable to fibrolytic enzymes and dairy.
Materials and Methods
A multiherd trial used 7,507 cows in 8 control and enzyme-treated (750 mL/t of DM feed) replicates (16 pen...
This paper examines the roles of the food retail sector acting as regulators of food production methods. It highlights the risks of allowing the food supply to be influenced by decisions made on the basis of marketing rather than good policy or efficiency of production and animal well-being.
Acidosis is a continuum of conditions of varying severity reflecting the challenge of safely sequestering hydrogen that accumulates from carbohydrate fermentation. Laminitis is aseptic inflammation, ischemia, and degeneration of laminae of the hooves. Laminitis may be caused directly and indirectly by acidosis or occur independently. Proper and reg...
Ketosis presents as clinical disease in which cattle typically have lower milk production, marked weight loss and low dry matter intake. Subclinical ketosis is characterized by increased ketone concentrations in blood, urine or milk and can be related to increased risks of health and reproductive disorders. Clinical and subclinical ketosis reflect...
The need for accurate and practically applicable nutrient requirements for ruminants is critical to the ability to produce food and fiber from healthy, productive and fertile animals. This article reviews currently used systems for describing nutritional requirements of dairy cattle used in a number of countries. Historical perspectives regarding t...
Pregnancy toxemia is a disorder of cattle, sheep, and goats that is characterized by high mortality rates, especially in recumbent animals. The disorder can also be one is also associated with high morbidity rates, especially in sheep. The condition reflects an imbalance between the a priori demands of the fetus and adnexa for nutrients, especially...
We provide an overview of methods used to analyze reproductive records in different production systems, highlighting the similarities and differences in approach needed. Implicit to our approach is a deep understanding of the epidemiology of reproductive management. The essential data, challenges of temporal effects, herd size and calving distribut...
Acidosis is a much more complex condition than simply reflected in a drop in ruminal pH. Acidosis is increased by diets higher in starch and sugars and lower in fiber and is reflected in increases in propionate and valerate concentrations and reduced ammonia concentrations and rumen pH. While the clinical expression of acidosis may be influenced by...
The study evaluated the relationship between pre-slaughter stress, plasma biomarkers and consumer-evaluated eating quality of pasture raised beef cattle (n = 488). The design tested steer only, heifer only and mixed sex cattle with a comparison of direct kill versus a 14 day rest period in abattoir holding paddocks prior to slaughter. Experiment On...
This study considered the relationship between pre-slaughter stressors and plasma biomarkers in 488 pasture-raised cattle across two experiments. The design aimed to test groups consisting of steer only, heifer only, and mixed sex cattle under direct kill versus rested (14 days in abattoir holding paddocks) protocols. In Experiment One, cattle were...
Our objectives were to characterize responses in the field to a mix of fibrolytic enzymes using large commercial dairy herds and sufficient study power to evaluate milk production and reproductive responses to an enzyme treatment started during the precalving period. We hypothesized that the use of the enzyme treatment would increase milk productio...
The onset of lactation results in a large and sudden increase in calcium (Ca) demand by the mammary gland to synthesize milk. The ensuing drop in circulating Ca plays a factor in the cow’s metabolic adaptation to lactation. When Ca maintenance fails, cow health and productivity is affected. Negative dietary cation-anion difference (DCAD) diets have...
Net energy systems, such as the
California Net Energy System (CNES), are useful
for prediction of input:output relationships
not because of fidelity to the laws of thermodynamics,
but because they were designed to predict
well. Unless model descriptions of input:output
relationships are consistent with the laws of thermodynamics,
conclusions regard...
The objectives were to use meta-analytic methods to determine the effects of changes in dietary cation-anion difference (DCAD) prepartum on productive performance and health of dairy cows. The literature was systematically reviewed, searching randomized experiments with transition cows that manipulated the prepartum DCAD or experiments with acidoge...
Prepartum diets influence cow performance for weeks to months postpartum. This observation leads to questions about milk yield and physiological and health responses to diets with negative dietary cation-anion difference (DCAD). Further, responses to increased intake of a diet with lower DCAD (Eq/d) have not been explored using meta-analysis. Our o...
Prepartum diets influence cow performance for weeks to months postpartum. This observation leads to questions about milk yield and physiological and health responses to diets with negative dietary cation-anion difference (DCAD). Further, responses to increased intake of a diet with lower DCAD (Eq/d) have not been explored using meta-analysis. Our o...
Due to their high energy requirements, high-yielding dairy cows receive high-grain diets. This commonly jeopardises their gastrointestinal health by causing subacute ruminal acidosis (SARA) and hindgut acidosis. These disorders can disrupt nutrient utilisations, impair the functionalities of gastrointestinal microbiota, and reduce the absorptive an...
Models of energy utilization used in livestock production predict input:output relationships well, for all the wrong reasons. Predictive accuracy in such models is not due to fidelity to biochemistry and laws of thermodynamics, but because they were developed to predict accurately, often with little regard to biochemical consistency. Relatively sta...
This represents discussion and analysis of the current dairy situation in Australia
Background
Benefits of hormonal growth promotants (HGP) include production efficiency, profit, and reduced environmental effects for beef cattle. Questions remain about effects of HGP on beef quality, particularly on measures of toughness such as Warner-Bratzler shear force (WBSF), tenderness, and other taste-panel attributes of beef.
Objective
To...
Bone-derived hormones play an important role in metabolism. This study examined the hypothesis that interactions between bone and energy metabolism, particularly those involving osteocalcin, are present in dairy cattle and have feedback mechanisms over time. Associations between metabolites in blood were examined in 32 Holstein cows blocked by pari...
This meta-analysis of 39 experiments containing 118 treatments explored the effects of diet interventions in early lactation on the proportion of dairy cows pregnant to artificial insemination (AI; pregnancy to AI) and on calving to pregnancy interval. It also identified factors that may explain variation in these responses. The objectives were to...
Dairy heifers were subjected to a non-life-threatening challenge designed to induce ruminal acidosis by feeding grain and sugar. Large among animal variation in clinical signs of acidosis, rumen metabolite concentrations, and the rumen microbiome occurred. This exploratory study investigates sources of the variation by examining associations betwee...
The study of vitamin D in cattle has often focussed on its role in calcium and mineral metabolism. However, there is evidence of a wider role for vitamin D in bone and energy metabolism. Two studies were conducted to explore relationships between calcidiol supplementation, blood minerals and metabolites in mid-lactation dairy cows. In Experiment 1,...
Pregnant Holstein cows, 28 nulliparous and 51 parous, were blocked by parity and milk yield and randomly allocated to receive diets that differed in dietary cation-anion difference (DCAD), +130 or -130 mEq/kg, and supplemented with either calcidiol or cholecalciferol at 3 mg/11 kg of dry matter from 255 d of gestation until parturition. Blood was s...
The objectives of the experiment were to evaluate the effects of feeding diets with distinct dietary cation-anion difference (DCAD) levels and supplemented with 2 sources of vitamin D during the prepartum transition period on postpartum health and reproduction in dairy cows. The hypotheses were that feeding acidogenic diets prepartum would reduce t...
The objectives of this experiment were to evaluate the effects of feeding diets with 2 dietary cation-anion difference (DCAD) levels and supplemented with either cholecalciferol (CH) or calcidiol (CA) during late gestation on lactation performance and energetic metabolism in dairy cows. The hypothesis was that combining a prepartum acidogenic diet...
Meta-analytic methods were used to determine statistical relationships between metabolizable AA supplies and milk protein yield, milk protein percentage, and milk yield in lactating dairy cows. Sixty-three research publications (258 treatment means) were identified through a search of published literature using 3 search engines and met the criteria...
King Island grass fed cattle (n=3,185) processed at a mainland Tasmanian abattoir in groups (n=66) between March-June 2015 were evaluated to determine which on farm factors impacted the incidence of dark cutting. Survey of mycotoxin prevalence revealed a high level of potentially toxic agents across all farms sampled. Total Ergot Alkaloids and Fumo...
http://m.adsa.org/2017/abs/t/69261
This meta-analysis of 39 studies containing 118 individual diets explored the effects of early lactation diets on the proportion of cows pregnant (PP) to service and calving to pregnancy interval. It was hypothesized that diet, intake of nutrients, and production after calving would affect these reproductive meas...
http://m.adsa.org/2017/abs/t/71101
There are beneficial effects of vitamin D and DCAD interventions in the pre-calving period on production, health and reproduction of cattle. How interventions during this time can have extended effects in the following lactation is not yet clear. Time series analysis was used to examine responses between metaboli...
[This corrects the article DOI: 10.1186/s13620-017-0092-y.].
Background:
Milk fat is important in terms of economic value and in its potential to provide information concerning cow diet and health. Under current milk payment schemes in Ireland farmer income is directly linked to milk fat production.
Methods:
A descriptive analysis of milk fat depression (MFD) as calculated from test day milk recording dat...
The aim of this study was to use meta-analytical methods to estimate effects of adding exogenous fibrolytic enzymes (EFE) to dairy cow diets on their performance and to determine which factors affect the response. Fifteen studies with 17 experiments and 36 observations met the study selection criteria for inclusion in the meta-analysis. The effects...