Presence of an older weaned companion influences feeding behavior and improves performance of dairy calves before and after weaning from milk.

In commercial dairy production, calves are typically separated from the dam at a young age. This practice may interfere with developmental processes mediated by social interactions that occur between the calf, her dam, and older social partners. The aim of this study was to test the prediction that calves housed with an older weaned companion would show earlier intake of solid feed before weaning and higher growth rates during and after weaning compared with calves housed with calves of their own age. Forty-five dairy calves were separated from their dams and housed individually for approximately 7 d. Afterward, calves were assigned to pens composed of groups of either 3 young calves or 2 young calves and an older weaned calf. Group pens were equipped with automatic milk, water, starter, hay feeders, and scales. Weaning was by gradual reduction of milk volume over 5 d, from d 36 to d 40. During the preweaning period (d 1 to d 35), the number (8.8 vs. 5.1 ± 0.5 visits/d per calf) and duration (13.2 vs. 8.2 ± 1.1 min/d per calf) of visits to the hay feeder was higher for calves housed with an older companion, and calves in this treatment consumed more hay (57.9 vs. 25.6 ± 4.7 g/d) than did calves housed in groups of similar age. Starter intake did not differ between treatments before weaning, but the number of visits (15.2 vs. 9.4 ± 0.6 visits/d) and the time spent at the starter feeder (6.5 vs. 3.4 ± 0.5 min/d) were higher for calves housed with an older weaned companion. During the weaning period (d 36 to d 40), calves housed with an older companion spent more time at the starter feeder (22.1 vs. 12.9 ± 1.9 min/d) and made fewer unrewarded visits to the milk feeder (17.0 vs. 26.1 ± 1.9 visits/d) than did calves housed in groups of similar age. During the postweaning period (d 41 to d 55), calves housed with an older weaned companion spent less time at the hay feeder (32.5 vs. 58.5 ± 5 .5 min/d) and more time at the starter feeder (41.4 vs. 28.2 ± 3.7 min/d), and consumed more starter (1.8 vs. 1.3 ± 0.1 kg/d). Calves housed with an older weaned companion gained more weight during the preweaning (0.89 vs. 0.76 ± 0.03 kg/d) and postweaning (1.4 vs. 1.1 ± 0.05 kg/d) periods. We conclude that housing young calves with an older weaned companion stimulates feeding behavior and growth before and after weaning from milk.