Pair housing and enhanced milk allowance increase play behavior and improve performance in dairy calves

To investigate the effects of social housing and milk feeding on play behavior and performance, 48 Holstein-Friesian male and female calves were either individually or pair housed in straw-bedded pens (3.0 m x 4.5 m). Half of the calves in each housing treatment were fed a standard milk allowance (5 L/d from d 3 to 42); the other calves were fed an enhanced milk allowance (9 L/d from d 3 to 28 and 5 L/d from d 29 to 42). All calves were abruptly weaned on d 43. Play behavior was recorded for 48 h beginning on d 15, 29, and 43. Variables were square root-transformed before analysis, but back-transformed values are given. On d 15 the duration of locomotor play behavior was greater among enhanced-than standard-fed calves [15.2 vs. 10.8 (+/- 1.0) corresponding to 231 vs. 117 s/24 h]; this behavior decreased when milk allowance in the enhanced treatment was reduced on d 29. Across ages, the duration of locomotor play behavior was greater among individually housed than pair-housed calves [10.9 vs. 8.2 (+/- 0.6) corresponding to 119 vs. 67 s/24 h], but the total duration of play did not differ between individual and pair-housed calves [130 (45-295) s/24 h; median and interquartile range]. Only pair-housed calves could perform social play behavior (play fighting), and the duration of this was greater on d 15 and 29 than on d 43 [8.3, 10.7 and 3.5 (+/- 1.3) corresponding to 69, 115 and 12 s/24 h for d 15, 29, and 43]. Among calves on enhanced milk, pair-housed animals had a greater concentrate intake than individually housed calves (840 vs. 530 +/- 110 g/d); for calves on standard milk, we detected no effect of housing [990 and 1,090 (+/- 110) g/d]. Among calves on enhanced milk, pair-housed calves had greater body weight gain than individually housed calves [990 vs. 850 (+/- 40) g/d]. For calves on standard milk, we observed no effect of pair versus individual housing [810 and 840 (+/- 40) g/d]. In conclusion, greater durations of play behavior in enhanced-fed calves suggest an animal welfare benefit of this feeding method. Enhanced-fed calves consumed less concentrate, but pair housing stimulated concentrate intake in these calves, suggesting that pair housing and enhanced feeding should be used together.