Effects of fasting duration and body weight on fasting heat production in growing pigs

Abstract

Two experiments were conducted to determine the effects of fasting duration and body weight on the fasting heat production of Duroc × Large White × Landrace crossbred barrows. In exp. 1, 6 pigs were fasted for 96 h. Heat production was measured every 12 h and the experiment was repeated at 3 separate body weights (31.1±1.1, 50.3±0.8 and 89.7±1.2 kg) to investigate the effects of different fasting durations on heat production and substrate oxidation. In Exp. 2, 12 Duroc × Large White × Landrace crossbred barrows were used to determine the effect of different body weights on fasting heat production. Fasting heat production was measured at 35.6±2.4, 44.7±3.1, 53.4±2.8, 63.9±2.7, 73.4±2.4, 83.3±3.0 and 95.6±2.0 kg following a fast of 48 h for the 35.6 as well as 44.7 pigs and a fast of 72 h for pigs at the remaining body weights. Before fasting, pigs were fed twice daily at 09:00 and 17:00. Fasting heat production was measured using indirect calorimetry after pigs were deprived of feed and the temperature was controlled at 24±1°C for pigs weighing 35.6 and 44.7 kg and22±l°C for pigs weighing 53.4-95.6 kg. The results of exp. 1 showed that the heat production decreased rapidly in the first 48 (31.1 kg) and 60 h (50.3 and 89.7 kg) of fasting (p<0.05) and then reached a stable period (p>0.05) between 48-96 (31.1 kg) and 60-96 h (50.3 and 89.7 kg) of fasting, respectively. In Exp. 2, with an increase in body weights (35.6-95.6 kg) the fasting heat production of pigs went up from 1577-2683 kcal day-1. In conclusion, the fasting heat production was 220 kcal/kg BW0.55/day (R2 = 0.97, p = 0.01) in pigs with body weights from 35.6-95.6 kg. © Medwell Journals, 2012.