The Effects of Weaning Age on the Welfare and Behavior of Dairy and Beef x Dairy Crossbred Calves

<p dir="ltr">Weaning non-replacement dairy calves early may save costs, labor, and time. However, this practice is likely to cause physiological and psychological stress, which can compromise calf welfare. Early weaning may differentially impact beef x dairy crossbred calves, a growing proportion of this calf population for which breed-specific requirements are lacking. The objective of this thesis is to determine the effects of weaning age (6 vs. 8 wk) on calf health, hematological parameters, growth, and metabolic status (Chapter 2), as well as salivary cortisol concentrations and behavior (Chapter 3) in dairy and beef x dairy crossbred calves. There was no evidence to suggest an effect of weaning age on the frequency of diarrhea or hematological outcomes. Calves weaned at 6 wk consumed less starter at weaning, which contributed to higher feed efficiency in the wk before step-down weaning, the wk of step-down weaning, and the first wk of complete weaning. Overall average daily gain tended to be greater in calves weaned at 6 wk, although there was no difference in body weight. Calves weaned at 8 wk exhibited signs of reduced physiological stress, as demonstrated by more gradual reductions in circulating glucose and insulin and lower, more steady salivary cortisol concentrations relative to calves weaned at 6 wk. Physiological breed differences were apparent: PB calves were 5.3 times more likely to have a “low” BCS, despite greater starter consumption and no evidence of differential adipose tissue mobilization. Calves weaned at 8 wk exhibited fewer behavioral transitions and were less active at complete weaning, potentially indicating less distress. Behavioral differences were observed between breeds; however, it is unclear if these differences are biologically relevant. Although there was marginal evidence for increased ADG and feed efficiency in calves weaned at 6 wk, enhanced productivity is not always reflective of good welfare. Therefore, the fewer behavioral and physiological signs of stress exhibited by calves weaned at 8 wk suggests increased welfare with delayed weaning.</p>