Little association between birth weight and health of preweaned dairy calves

Effect of neonatal immunoglobulin status on the outcomes of spring-born suckler calves

BACKGROUND

Successfully rearing beef calves to weaning and beyond determines the economic performance of a beef farm. As such, it is important to understand the factors influencing performance outcomes.

METHODS

This study recorded the health events, mortality and growth rates of 674 calves born on 50 commercial beef farms in Great Britain using a postsampling questionnaire. All calves had a known postcolostral serum IgG status.

RESULTS

Preweaning mortality in the study population was 1.5% (10/674 calves), while the treatment rate was 6.4% (43/674 calves). Serum IgG, calf sex and dystocia were significant predictors of whether a calf died and/or required treatment. Average daily liveweight gain was calculated for calves where weaning weights were provided (n = 513). Serum IgG and calf sex were consistent predictors of calf growth rates, while birthweight and whether the calf was born to a cow or heifer were predictive in a model where average daily liveweight gain was converted to a binary response variable using the mean average daily liveweight gain on the calf's farm of origin.

LIMITATIONS

Morbidity and mortality were lower than comparable studies, potentially due to limitations in the study design.

CONCLUSION

Serum IgG and calf sex were significant explanatory variables that affected beef calf average daily liveweight gain. For every 5 g/L increase in serum IgG, the odds ratio of dying and/or requiring treatment decreased by 0.86.

Developmental Programming of Fertility in Cattle-Is It a Cause for Concern?

Cattle fertility remains sub-optimal despite recent improvements in genetic selection. The extent to which an individual heifer fulfils her genetic potential can be influenced by fetal programming during pregnancy. This paper reviews the evidence that a dam's age, milk yield, health, nutrition and environment during pregnancy may programme permanent structural and physiological modifications in the fetus. These can alter the morphology and body composition of the calf, postnatal growth rates, organ structure, metabolic function, endocrine function and immunity. Potentially important organs which can be affected include the ovaries, liver, pancreas, lungs, spleen and thymus. Insulin/glucose homeostasis, the somatotropic axis and the hypothalamo-pituitary-adrenal axis can all be permanently reprogrammed by the pre-natal environment. These changes may act directly at the level of the ovary to influence fertility, but most actions are indirect. For example, calf health, the timing of puberty, the age and body structure at first calving, and the ability to balance milk production with metabolic health and fertility after calving can all have an impact on reproductive potential. Definitive experiments to quantify the extent to which any of these effects do alter fertility are particularly challenging in cattle, as individual animals and their management are both very variable and lifetime fertility takes many years to assess. Nevertheless, the evidence is compelling that the fertility of some animals is compromised by events happening before they are born. Calf phenotype at birth and their conception data as a nulliparous heifer should therefore both be assessed to avoid such animals being used as herd replacements.

Genes and regulatory mechanisms associated with experimentally-induced bovine respiratory disease identified using supervised machine learning methodology

Bovine respiratory disease (BRD) is a multifactorial disease involving complex host immune interactions shaped by pathogenic agents and environmental factors. Advancements in RNA sequencing and associated analytical methods are improving our understanding of host response related to BRD pathophysiology. Supervised machine learning (ML) approaches present one such method for analyzing new and previously published transcriptome data to identify novel disease-associated genes and mechanisms. Our objective was to apply ML models to lung and immunological tissue datasets acquired from previous clinical BRD experiments to identify genes that classify disease with high accuracy. Raw mRNA sequencing reads from 151 bovine datasets (n = 123 BRD, n = 28 control) were downloaded from NCBI-GEO. Quality filtered reads were assembled in a HISAT2/Stringtie2 pipeline. Raw gene counts for ML analysis were normalized, transformed, and analyzed with MLSeq, utilizing six ML models. Cross-validation parameters (fivefold, repeated 10 times) were applied to 70% of the compiled datasets for ML model training and parameter tuning; optimized ML models were tested with the remaining 30%. Downstream analysis of significant genes identified by the top ML models, based on classification accuracy for each etiological association, was performed within WebGestalt and Reactome (FDR ≤ 0.05). Nearest shrunken centroid and Poisson linear discriminant analysis with power transformation models identified 154 and 195 significant genes for IBR and BRSV, respectively; from these genes, the two ML models discriminated IBR and BRSV with 100% accuracy compared to sham controls. Significant genes classified by the top ML models in IBR (154) and BRSV (195), but not BVDV (74), were related to type I interferon production and IL-8 secretion, specifically in lymphoid tissue and not homogenized lung tissue. Genes identified in Mannheimia haemolytica infections (97) were involved in activating classical and alternative pathways of complement. Novel findings, including expression of genes related to reduced mitochondrial oxygenation and ATP synthesis in consolidated lung tissue, were discovered. Genes identified in each analysis represent distinct genomic events relevant to understanding and predicting clinical BRD. Our analysis demonstrates the utility of ML with published datasets for discovering functional information to support the prediction and understanding of clinical BRD.

Passive immunity and colostrum management practices on Ontario dairy farms and auction facilities: A cross-sectional study

Failed transfer of passive immunity (FTPI) in dairy calves has substantial health consequences, but there have been no recently published estimates of the prevalence of FTPI on Ontario dairy farms. The major objectives of this cross-sectional study were to determine the level of FTPI in dairy calves across the province of Ontario and to determine colostrum management practices used. A convenience sample of 109 dairy farms in Ontario were visited from June to August 2019, along with 4 auction facilities from January to February 2019. At the single visit to each dairy farm, an in-person questionnaire was administered, and all calves between 24 h and 9 d of age had a blood sample collected to determine the levels of serum total protein (STP). At the auction facility, a blood sample was collected on all calves that arrived on the day of the visit. The dairy farms were distributed throughout Ontario, and the farms milked on average 151 dairy cows. Of the 444 calves sampled on Ontario dairy farms, 46% were male, 54% were female, and the mean weight and age at sampling were 46.3 kg and 4.4 d, respectively. The mean STP of calves sampled on the dairy farm was 5.69 g/dL (standard deviation = 0.78), and 107 calves (24%) had FTPI. The likelihood of FTPI was not associated with sex (female vs. male, risk ratio = 0.89, 95% confidence interval = 0.64-1.24), age (per day, risk ratio = 1.02, 95% confidence interval = 0.94-1.11), or weight (per kg, risk ratio = 0.98, 95% confidence interval = 0.96-1.01). In contrast, at the auction facilities, 386 male dairy calves were sampled and had a mean STP of 5.79 g/dL (standard deviation = 0.83). Using a cut point of ≥5.2 g/dL, 91 calves (24%) had FTPI. From the in-person questionnaire administered on the dairy farms, it was reported that the median time to first feeding of colostrum was 2.5 h (range = 0-12 h). The farms reported providing a mean of 3.3, 2.9, and 3.4 L of colostrum from 0 to 6 h after birth, 6 to 12 h after birth, and 12 to 24 h after birth, respectively. Ninety-one farms (83%) fed colostrum from the dam of the calf as their predominant source of colostrum. The most common method used to deliver the first feeding of colostrum was a nipple bottle (89 farms, 82%). Twenty-seven farms (25%) reported managing colostrum differently for male calves, which included a different colostrum source, use of poorer quality colostrum, a smaller quantity of colostrum, a longer time from birth to feeding, and generally having a lower focus on colostrum management for male calves. The prevalence of FTPI on Ontario dairy farms appears to have decreased since previous estimates, and substantial room for improvement remains. Although no overall differences were found in FTPI between male and female calves, differential reported colostrum management by sex indicates this may be a risk for male calves on a proportion of Ontario dairy farms.