INDOOR SPACE ALLOWANCE - EFFECTS ON GROWTH, BEHAVIOR, ADRENAL AND IMMUNE-RESPONSES OF FINISHING BEEF HEIFERS

The objective was to determine the daily live-weight gain, behaviour, adrenal and immune responses of finishing beef heifers housed at two d ifferent space allowances. Heifers (no. = 32) with a mean live weight of 466 (s.e. 3.6) kg were assigned to either 1.5 or 3.0 m(2) average i ndividual space allowance in four slatted-floor pens (two per treatmen t)for a period of 104 days. On days 5, 40, 68 and 96, heifers (no. = e ight per treatment, four per pen) were challenged with 1.98 i.u. ACTH per kg M(0.75), and serial blood samples were analysed for plasma cort isol concentrations. The other 16 heifers were immunized against keyho le limpet haemocyanin (KLH) on day 28, and blood samples collected on days 28, 42, 56, 70, 84 and 98 were analysed for anti-KLH immunoglobul in (Ig) concentrations. All heifers were blood sampled on days 0, 14, 56 and 98, and red and white blood cell numbers, packed cell volume (P CV) and plasma concentrations of creatine kinase (CK), non-esterified fatty acids (NEFA) and urea were determined. Behavioural observations were conducted on days 8, 43, 71 and 99 by scan sampling for 24 h (10- min intervals), and continuous 4-h observations were conducted on days 100 and 101. Heifers at 1.5 m(2) space allowance had a lower daily li ve-weight gain compared with those nt 3.0 m(2) (0.60 v. 0.87 (s.e. 0.0 4) kg; P < 0.001). Heifers at 1.5 m(2) and lower pre-ACTH baseline cor tisol concentrations (P < 0.05) and lower post-ACTH peak cortisol conc entrations (P < 0.05). There were no effects of treatment on serum ant i-KLH IgG(1) or IgG(2) responses (P > 0.05). Heifers at 1.5 m(2) had l ower plasma NEFA concentrations (P < 0.05). Red and white blood cell n umbers, PCV, CK and urea were not affected by treatment (P > 0.05). Th e time spent lying down was lower for heifers at 1.5 m(2) (10.0 v. 11. 1 h/day; P < 0.05). Social interactions were fewer (P < 0.05), and inc idence of head-resting behaviour was higher (P < 0.05) among heifers a t 1.5 m(2) compared with 3.0 m(2) space allowance. In conclusion, the restricted space allowance resulted in a substantial decrease in daily live-weight gain, and changes in adrenal response and behaviour.