Little association between birth weight and health of preweaned dairy calves.

Intrauterine growth retardation (IUGR) may result in reduced birthweight and detrimental physiological alterations in neonates. This prospective cohort study was designed to assess if there exists an association between birthweight of dairy calves and incidence of bovine respiratory disease (BRD), neonatal calf diarrhoea (NCD) or mortality during the pre-weaning period. Calves (n=476) on 3 farms in South West England were weighed at birth. Farmers kept records of treatments for NCD and BRD and calves were assessed weekly using clinical scoring systems (Wisconsin Calf Health Scores, California Calf Health Scores and Faeces Scores). Missing data were present in several variables. Multiple imputation coupled with generalised estimating equations (MI-GEE analysis) was employed to analyse associations between several calf factors, including birthweight, and probability of a case of BRD or NCD. Associations between calf factors and mortality were assessed using multiple logistic regression. Associations between birthweight and disease incidence were scarce. Birthweight was associated with odds of a positive Faeces Score on one farm only in the MI-GEE analysis (O.R. 1.03, 95% C.I. 1.0005-1.05, P=0.046). Birthweight was not associated with probability of mortality. This research suggests that birthweight, and therefore IUGR, is not associated with health of pre-weaned dairy calves. © British Veterinary Association 2019. No commercial re-use. See rights and permissions. Published by BMJ.