Does a calf's motivation to ingest colostrum depend on time since birth, calf vigor, or provision of heat?

Dairy producers often complain that calves have difficulty consuming the recommended amount of colostrum. A better understanding of factors affecting calves' motivation to ingest colostrum could help develop better management. Thirty-six Holstein calves were tested to evaluate effects of time since birth (2 vs. 6 h) and provision of a heat lamp on motivation to ingest colostrum in a 2 x 2 factorial model. Calves were randomly assigned to treatments balancing for birth weight and sex. Calves were provided colostrum (>68 g of Ig/L) ad libitum from a teat-bottle. We tested the calf's suckling reflex by examining the response to orofacial stimulation and assessed the calf's vigor from the duration of time spent standing or attempting to stand in the hour after birth and standing during colostrum feeding. During the first meal, 42% of calves consumed 4 L or more of colostrum, 25% consumed 3 to 4 L, 11% consumed 2 to 3 L, and 22% consumed <2 L. There were no significant effects of heat supply or time since birth on consumption. The quantity of colostrum ingested was best predicted (r(2) = 0.61) by a combination of birth weight, vigor during colostrum feeding, and vigor during the first hour of life, whereas meal duration was predicted (r(2) = 0.34) jointly by room temperature and having suckled the dam. Colostrum intake was lower for small calves and calves with a low degree of vigor. Differences among calves in the strength of the sucking reflex were not related to colostrum intake.