Effects of Plane of Nutrition on Organ Size and Fasting Heat Production in Genetically Obese and Lean Pigs

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Abstract
Fifteen obese and 15 lean pigs with an initial weight of 27 kg, three from each of five litters, were randomly assigned within litter to three treatments. The first treatment 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 treatment group (MM) was fed to gain 7 kg during both periods 1 and 2. The third treatment 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, all pigs 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 intestines, liver, pancreas, spleen, kidneys and heart were measured. Although all animals had the same final body weight, both obese and lean pigs on the higher plane of nutrition during period 2 had significantly higher FHP and higher weights for stomach, small and large intestines, pancreas, liver and kidneys. Lean pigs had significantly higher weights for stomach, large intestine, pancreas, heart, and spleen than their obese counterparts with no significant difference detected for small intestine, liver and kidneys. Statistical analyses did not reveal any difference between lean and obese pigs for FHP even though lean pigs on MM and LH treatments had 17 and 15% higher FHP values than obese pigs from the same treatment groups. Significant and 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 for both genetically obese and lean pigs.