Chemical composition of body compartments and plasma parameters after protein-free feeding and realimentation in growing pigs

Changes in the fat and protein contents in the body compartments of growing pigs were studied during a protein-free feeding period and a subsequent re alimentation period. Out of 54 crossbred castrated male pigs (35 kg on day 0), six were slaughtered on day 0 for reference purposes and 48 were random ly divided between six treatments. During the 14 day-protein-free feeding p eriod three different isocaloric diets were offered: control (C), protein-f ree, carbohydrate-rich (PF/CHO), and protein-free, fat-rich (PF/FAT). On da y 14, eight pigs per treatment were slaughtered. During the realimentation period all of the remaining pigs received the control diet and formed the o ther three treatments (C-C, PF/CHO-C, and PF/FAT-C). They were slaughtered on day 21. After slaughter, the right side of the carcass, the liver, and b oth large and small intestines were weighed and analysed for ash, fat, dry matter and nitrogen contents. Feeding either one of the protein-free diets increased the fat content (g/kg body weight) of the carcass and intestines but not of the liver. Protein-free feeding induced proportionally a greater decrease of protein disposition in the river and intestines than in the ca rcass, resulting in a significant decrease of the protein contents of the l iver and intestines. This impaired protein status was also reflected in dec reased plasma urea and creatine levels. After realimentation, the protein c ontent of the carcass did not reach the control values, nor did the plasma creatine. The protein contents in both liver and intestines did not differ between treatments. The results of the present study suggest that the prote in metabolism in the liver and intestines responds rapidly to dietary chang es, whereas the carcass composition changes more slowly.