Dominique Rinaldo

Assessment of optimal temperature for performance and chemical body composition of growing pigs

Sixty-four individually penned pigs were used between 9 and 30 kg live weight to determine the effects of environmental temperatures of 12.0, 18.5, 25.0 and 31.5°C on performance, energy metabolism and body composition in order to assess the optimal temperature. Pigs were fed ad libitum a diet providing 12.4 MJ ME and 10.8 g total lysine/kg. Heat production was minimal within the 25.0 to 31.5°C temperature range. Below the lower critical temperature (LCT), i.e., between 25.0°C and 12.0°C, growth rate, energy retention and empty body weight gain (EBWG) composition did not vary significantly, while feed intake was increased by 16% (P < 0.05). Above the LCT, i.e., between 25.0 and 31.5°C, feed intake was decreased by 18% (P < 0.05), energy retention by 19% (P < 0.01) and fat content of EBWG by 13% (P < 0.05). Growth rate was reduced by 15% between 25.0 and 31.5°C (P < 0.001) while feed-to-gain ratio remained constant and minimal. Increasing environmental temperature involved a decline (P < 0.05) in the weights of heart, liver, kidneys and empty digestive tract and an improvement (P < 0.05) in killing-out percentage. Above the LCT, less fat was deposited in backfat (P < 0.10) and more fat retained in leaf fat and viscera (P < 0.05). On the basis of reduced fatness and feed to gain ratio, the overall data suggest that the optimal temperature for growing pigs fed ad libitum is higher than LCT and therefore does not correspond to a maximal rate of energy retention.

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 208C and relative humidity (RH) of 75%. Under tropical climate, ambient temperature averaged 24.68C and RH 84% during the cool season (CTC) and 27.38C 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.

Effects of warm exposure on adipose tissue and muscle metabolism in growing pigs.

1. Forty-eight pigs weaned at 3 weeks old and acclimated to the experimental temperatures for 2 weeks before the start of the experiment, were fed ad lib and used between 9 and 33 kg live weight to determine the effects of warm exposure (31.5 vs 18.5 degrees C) on adipose tissue and muscle metabolism. 2. Warm exposure induced a decline in the lipid content (P less than 0.01) of backfat whereas degree of saturation (P less than 0.05) and adipocytes size were increased (P less than 0.05). 3. At 31.5 degrees C, as compared to 18.5 degrees C, activities of malic enzyme and glucose-6-phosphate dehydrogenase were depressed by an average 33% in backfat (P less than 0.01) and 23% in leaf fat (P less than 0.05) while lipoprotein-lipase activity was stimulated by 60% (P less than 0.01) in leaf fat. 4. In warm conditions, the activities of the enzymes indicative of oxidative and glycolytic metabolism in muscle, i.e. lactate dehydrogenase, beta-hydroxyacyl coenzyme-A dehydrogenase, citrate synthase and cytochrome oxidase, were reduced in the longissimus dorsi muscle (P less than 0.05) and to a lesser extent in the trapezius muscle. 5. At 31.5 degrees C, pigs exhibit lower average plasma levels of insulin, T3 and T4 than those maintained at 18.5 degrees C.