Initial Body Condition Score at the Fattening Affects on the Behavioural and Physiological Responses of Holstein Friesian Steers under Heat Stress

The objective of this study was to determine the effect of initial Body Condition Scores (BCS) on fattening performance, behavioural and physiological responses of dairy fattening steers as a thermal insulator under heat stress. Thirty six Holstein Friesian steers were allocated to three groups. For a period of 5 weeks, twice a week, the behaviour of each steer was registered for 4 h (07:00, 12:00, 18:00 and 22:00 h), recording of eating, lying, fighting, ruminating, standing, grooming and other behaviours. Steers having higher body condition score decreased feed intake (p = 0.007) and daily weight gain with poorer feed efficiency (p<0.001). The frequencies of eating, drinking, ruminating, standing, lying, grooming, fighting and other behaviours for low, moderate and high body condition scored (LBCS, MBCS and HBCS, respectively) of steers were 12.53, 11.58, 8.93 (p<0.001); 2.22, 3.31, 3.17 (p = 0.428); 11.73, 9.85, 9.20 (p = 0.023); 17.17, 16.07, 14.20 (p = 0.025); 10.77, 12.73, 17.77 (p<0.001); 3.41, 3.20, 1.71 (p = 0.003); 1.16, 2.40, 4.51 (p<0.001) and 1.01, 0.86, 0.51 (p = 0.023) min h(-1), respectively. The frequencies of heart rate, respiration rates, rectal temperatures and skin temperatures were 58.82, 62.40 and 63.87 pulses min(-1) (p<0.001), 42.30, 44.30 and 47.10 breaths min(-1) (p<0.001), 38.10,. 38.30 and 38.40 degrees C (p = 0.246) and 32.89, 32.92 and 32.97 degrees C (p = 0.432), respectively. In conclusion, initial body condition at fattening affects on the fattening performance, behavioural and physiological responses of steers, suggesting that (LBCS) animals were more adaptive and productive in fattening under heat stress.