Adverse effects of tropical climate on voluntary feed intake and performance of growing pigs

Four replicates were conducted to determine the effects of tropical climate and season on voluntary feed intake and performance of pigs and their carcass characteristics at 90 kg, as compared to a control environment (CE). CE was characterized by ambient temperature of 20 degreesC and relative humidity (RH) of 75%. Under tropical climate, ambient temperature averaged 24.6 degreesC and RH 84% during the cool season (CTC) and 27.3 degreesC and 82% during the warm season (WTC) respectively. Ninety-six Large White pigs were used between 15 and 35 kg live weight (P1) and, as 36 of them were slaughtered at 35 kg, the remaining pigs were used from 35 to 90 kg (P2). In the CTC, neither voluntary feed intake, nor average daily gain, Feed:gain ratio or carcass characteristics significantly differed from CE in P1 and P2 pigs. In the WTC, the 13% decline in feed intake of P2 pigs (P < 0.001) induced a 13% diminution in growth rate (P < 0.05). In the WTC, fat percentage of the carcass was reduced by 3.2 units (P < 0.001), whereas less fat was deposited in backfat (P < 0.001) and more fat retained in leaf fat (P < 0.001), as compared to the CTC. Also in the WTC, the reduction in the weight of internal organs led to a 1.8 unit improvement in killing-out percentage (P<0.001). Data indicated that in the tropics, growth performance varied with the season and that during the warm season feed intake was a major limiting factor to growth rate. (C) 2000 Elsevier Science B.V. All rights reserved.