Weaning age impacts growth, feed intake and behavioral indicators of stress in Holstein calves fed a high plane of nutrition
Recent research has revealed the short- and long-term advantages of feeding more nutrients pre-weaning. Unfortunately, calves that are fed more nutrients pre-weaning may be more susceptible to depressed growth and weaning stress during the transition from liquid to solid feed. The objective of this study was to investigate the relationship between age of weaning and feed intake, growth and behavioral indicators in dairy calves fed higher planes of nutrition. To meet this objective, a total of 20 Holstein female calves were randomly assigned at birth to be weaned at 6 or 8 wk. Milk replacer (mixed at 150g/L) was offered at 1.2kg/calf/d in two meals until a 1-wk step down where meals were reduced by 50% 1 wk before weaning. Measurements included daily starter, chopped straw, and water intake, as well as weekly bodyweights until d 70 of life. Behavioural indicators including ruminating, lying/standing, vocalizing and non-nutritive oral behavior were measured by visual observation each minute for 3h per week prior to the second feeding of the day. Data was analyzed using a repeated measures general linear mixed model; comparisons were made by week relative to weaning and week of life. The calves weaned at 8 wk compared to 6 wk had higher (P<0.01) ADG for the week pre weaning (0.79 ± 0.09 vs. 0.34 ± 0.10 kg/d) and post weaning (1.05 ± 0.09 vs. 0.35 ± 0.11 kg/day), and were heavier (P<0.01) at the end of the experiment (99.92 ± 1.81 vs. 91.01 ± 2.26 kg). Starter, straw and water intake was delayed in calves weaned at 8 wk of age. However, their overall starter intakes and growth rates were not different during the last week of the experiment. Furthermore, calves weaned at 8 wk compared to 6 wk had higher (P<0.01) starter intake for the week pre weaning (1.36 ± 0.13 vs. 0.40 ± 0.08 kg/d) and post weaning (2.51 ± 0.20 vs. 1.16 ± 0.15 kg/day). Treatment×week relative to weaning interactions indicated that several behaviors varied between early and later weaned calves during the week prior to weaning; 6 wk calves tended (P=0.07) to exhibit 75% more non-nutritive oral behavior, spent 55% less (P<0.01) time ruminating, and 36% less (P=0.01) time lying, than 8 wk calves. These results suggest that calves fed higher planes of nutrition pre-weaning benefit from extending weaning age from 6 to 8 wk of age.
Keywords: Calves, weaning, age