Protein and lipid deposition rates in growing pigs following a period of excess fattening

The objective of this experiment was to test the proposition that fatter pigs, when fed a high crude protein (CP) diet, would attempt to correct the effects of excess fattening on body composition by returning to a state that is consistent with pigs grown under non-limiting nutritional conditions. The experiment was divided into two phases: Phase 1 was from 15 to 30 kg in which 72 of the 96 Large White x Landrace x Duroc pigs (equal male and female) were made fatter by consuming a low CP food (LP1) (181 g/kg (as fed)). The remaining 24 pigs were fed a high CP food (HP1) (223 g/kg (as fed)) to provide the rate and composition of growth associated with unrestricted or normal growth. Phase 2 was the rehabilitation phase and was divided into two periods: 30 to 45 kg and 45 to 60 kg. Pigs that were fed LP1 were randomly allocated to one of a high CP (HP2) (204 g/kg (as fed)), low CP (LP2) (159 g/kg (as fed)) or medium CP (MP2) (181 g/kg (as fed)) food, respectively. Pigs fed HP1 in Phase 1 continued to be fed HP2 in Phase 2. During Phase 1, pigs fed HP1 consumed less food but grew at a similar rate to pigs fed LP1. Pigs fed LP1 were significantly fatter, had less body water and had a higher lipid:protein ratio (0.86±0.04 vs. 0.67±0.09 g/g, respectively) at the end of Phase 1. Between 30 and 45 kg, pigs fed HP2 and previously fed LP1, retained significantly less lipid and had the lowest lipid growth:protein growth ratio (0.38±0.05) than all other treatments. By 45 and 60 kg, there were no significant differences in the lipid content and lipid:protein ratio of pigs across all treatments. It can be concluded that nutritionally induced, fat pigs will attempt to restore their body lipid contents, to those levels in animals not previously nutritionally deprived, by reducing their rate of lipid retention when fed a higher crude protein food. _________________________________________________________________________________________