How milk allowance affects milk and starter intake, behaviour and weight gain in dairy calves
While the conventional milk feeding rate of 10% of a calf’s birth weight (usually around 4L per day) is still used1 to stimulate solid feed intake, with these lower levels of milk rations, calves are more likely to experience hunger2 and lower growth rates.3 Dairy farms are increasingly choosing to feed calves higher planes of pre-weaning nutrition which support greater growth.4 These higher feeding planes do require additional management to increase starter intake prior to weaning, such as using gradual weaning methods5 and providing social housing.6 But, the results allow for improved weight gains and better calf welfare.7
In their research entitled, “The effect of milk allowance on behavior and weight gain in dairy calves,” Rosenberger, et al.8 sought to determine the short- and long-term effects of a variety of milk allowances on feed intake, behavioural signs of hunger, and body weight. They also wanted to determine the necessary calf management interventions when feeding higher planes of pre-weaning nutrition.
Design of the research
Fifty-six Holstein calves (32 females and 24 males) were randomly assigned to 1 of 4 feeding treatments (6, 8, 10 or 12 L/d) of whole pasteurized milk, at 1 week of age. At day 42, their milk allowance was reduced by half. It was then reduced by an additional 20% per day, beginning at day 50. All calves were fully weaned by day 55, and all had ad libitum access to both hay and starter feed throughout the study. Calves were housed in groups of 8, containing 2 calves from each of the 4 treatments.
Between 2 and 10 weeks of age, body weights were measured. Daily intakes of milk and starter were recorded, and unrewarded trips to the automated feeder were counted as well. ADG, feed ratio and body weight (BW) were recorded throughout the study and weekly health checks were performed.
What they found
- Milk consumption: In the study, milk intake did indeed increase with milk allowance, although none of the calves consumed to the limit of their allowance. For example, on average, 5.66L p/d was consumed by the 6L calves and 9.4L p/d was consumed by the 12L calves, prior to beginning step-down weaning.
- Rewarded and unrewarded visits to the feeder: Calves allowed less milk had more unrewarded visits to the feeder than those with a higher milk allowance (averaging 11.1 p/d for the 6L calves compared with 0.4 p/d for the 12L calves, pre-weaning). These unrewarded visits are indicative of hunger, which is a finding supported by previous studies.9 While unrewarded visits did increase during weaning for all treatments, calves with a higher milk allowance still had fewer unrewarded visits.
- Calf starter intakes: Prior to weaning, intake of calf starter was higher for calves fed less milk. For example, the 6L calves consumed 0.25 kg/d whereas the 12L calves consumed only 0.05 kg/d. While differences in starter consumption between the treatments continued during weaning (6L calves averaged 1.15 kg/d compared to the 12L calves at 0.54 kg/d), there was no difference in starter consumption after weaning, with all treatments consuming almost 3 kg/d. As consuming more starter prior to weaning can ease the transition from milk to solid feed, thereby decreasing weaning stress, when higher amounts of milk are fed prior to weaning, management is required to stimulate interest in solid feed. The present study utilised several techniques to do so including using a step-down weaning process, providing access to forage, and housing calves socially. Socially housed calves have less phobia of new foods10 and tend to have higher pre-weaning starter intakes.11
- Growth in the short- and long-term: ADG was higher for calves fed more milk, with the 6L calves averaging 0.77 kg/d compared to the 12L calves at 0.90 kg/d. The benefits of feeding more milk early on persisted so that over the course of the entire study, ADG was higher for calves fed more milk. This is consistent with previous studies.12 And, with appropriate weaning management, the body weight advantage of the 12L calves remained both during and after weaning. Additionally, feeding higher amounts of milk, pre-weaning, and the resulting higher body weights, may have positive effects on both long-term production and reproduction.13
Why what they found matters
This study confirms that calves given ad libitum access to milk can indeed consume very high quantities. And, the high number of unrewarded trips to the feeder for calves with lower milk rations shows that calves fed restricted amounts of milk experience hunger throughout both the pre-weaning and weaning periods—a situation with serious implications for calf welfare. To decrease stress at weaning for calves fed higher amounts of milk, management techniques to smooth the transition are important. And, higher ADGs resulting from a higher pre-weaning plane of nutrition can indeed persist long after weaning, if weaning is managed properly.