Effects of plane of nutrition on organ size and fasting heat production in pigs.

Twenty-seven 12-week-old barrows with average initial weight of 27 kg were randomly assigned to three treatments. The first group (HL) was fed to gain 19 kg body weight during the first 35 days (period 1) and to lose 5 kg during the second 35 days (period 2). The second group (MM) was fed to gain 7 kg during both periods 1 and 2. The third group (LH) was fed to lose 5 kg during period 1 and to gain 19 kg during period 2. At the end of the 70-day period, 7 pigs from each treatment were fasted for 30 hours and fasting heat production (FHP) was measured by indirect calorimetry. The animals were slaughtered and weights of stomach, small and large intestine, liver, pancreas, spleen, kidneys and heart were measured. Although all animals had the same final body weight, animals on the higher plane of nutrition during period 2 had significantly higher FHP and higher weights for stomach, small and large intestine, pancreas, liver and kidneys. FHP and the weights of small intestine, pancreas and liver from animals receiving the higher plane of nutrition during period 2 (LH) were 50% heavier than that from animals on low plane (HL). Positive correlations exist between FHP and weights of stomach, small intestine, large intestine, pancreas, liver and kidneys. These results indicate that prior nutritional history significantly influences FHP, which is highly correlated to weights of metabolically active organs.