Effect of group size on behavior, health, production, and welfare of veal calves

The objective of this study was to investigate the effect of group size on behavior, growth, health, and welfare of veal calves. Holstein-Friesian bull calves (n = 168; 44 ± 3 d of age) were assigned randomly to 1 of 3 treatments of group housing with 2, 4, or 8 calves per pen. The pens used for housing were 3 by 1.20 m (2 calves per pen), 3 by 2.40 m (4 calves per pen), and 3 by 4.80 m (8 calves per pen), supplying a total pen space allowance of 1.82 m2/calf, regardless of pen size. Behavior was recorded from video data throughout the day from 0700 to 1900 h during a single day each month for 5 mo using scan sampling every 5 min within 30-min observation sessions. On d 0, 1, 5, 14, 42, and 70 after grouping, continuous focal sampling around feeding time (30-min intervals before, during, and after feeding) focused on oral and aggressive behaviors. Calves housed in large groups (4 or 8 calves per pen) showed more (P ≤ 0.001) conspecific contact, walking, and standing and less (P < 0.001) manipulation of objects, self-licking, and lying when compared to calves housed in small groups (2 calves per pen). Group size had no effect on play behavior (P = 0.11) throughout the experiment. During feeding times group size had no (P ≥ 0.07) effect on any behavioral patterns except for duration of conspecific contact (P < 0.01). Aggression at feeding time was not (P > 0.23) affected by treatment. Group size treatments were similar for hip height change (P = 0.41) and heart girth change (P = 0.18) over the duration of the experiment; however, both hip height and heart girth increased (P = 0.001) with calf age. During mo 1, calves in groups of 8 or 4 coughed more than calves in groups of 2 whereas calves in groups of 8 coughed more than calves in groups of 4 or 2 in mo 2 (treatment × month, P = 0.03). Furthermore, during mo 4, calves in groups of 8 had less nasal discharge than calves in groups of 2 or 4 (treatment × month, P = 0.02). Ocular discharge, ears, and fecal scores did not differ (P ≥ 0.05) among treatments. Plasma cortisol was not (P ≥ 0.37) affected by group size. The number of veal calves in a group when given the same space did not affect production and physiological indicators of welfare but had a transient effect on health during the 5-mo finishing period. If increased play and social contact and decreased aggression are considered as primary indicators of welfare, group size did not alter calf welfare.