Effect of pen size on behavioral, endocrine, and immune responses of waterbuffalo (Bubalus bubalis) calves

Female water buffalo (Bubalus bubalis) calves (n = 28) aged 7 to 10 d were divided into four; groups of seven animals each to examine the effects of s pace allowance (Group A: 2.6 indoor m(2) + 2.0 outdoor m(2)/calf; Group B: 2.6 indoor m(2)/calf; Group C: 1.5 indoor m(2)/calf; Group D: 1.0 indoor m( 2)/calf) on behavioral, endocrine, and immune variables for a period of 60 d. Animals were offered 7 L/d of a commercial acidified milk substitute. Th e calves averaged 45.9 kg initially and 92.4 kg finally. The behavior obser vations were conducted 7 d after grouping and fortnightly thereafter. At wk 4 and 8, the phytohemagglutinin (PHA) skin test was performed to induce as pecific delayed hypersensitivity. At wk 1 and 3, calves were injected i.m. with keyhole limpet hemocyanin. Antibody titers were determined at weekly i ntervals for 7 wk. Calves in pens with greater space allowance (Groups A an d B) were less active than Groups C and D (P < .001). The latter groups wer e also observed feeding more often at wk 7 (P < .01). Calves provided with an outdoor paddock spent less time standing than Groups C and D (P < .01), and lay with a greater number of outstretched legs (P < .001). Groups C and D showed a lower reaction to PHA in both skin tests than did Groups A and B (P <.001 and P < .05, respectively). Group A showed an antibody response consistently higher than groups B, C, and D (P < .01, P < .05, and P < .05, respectively). At the end of the experimental period, the calves were subj ected to an isolation test lasting 10 min. Group D showed a longer duration of movement with respect to Groups A and B (P < .01); animals from Group C walked more than did Group A (P < .05). Cortisol concentration evaluated 0 , 10, 45, 90, 150, and 225 min after separation from the group was higher i n Groups C and D than in Groups A and B (P < .01). For all animals, the hig hest cortisol level was observed immediately after the isolation test (P < .001). Space restriction resulted in evidence of stress in the animals as s hown by alterations in a number of physiological responses. However, the us e of small groups of only seven animals per pen may have affected their rea ctions to space restriction. It is possible that using larger groups could change these conclusions.