Compensatory growth in slaughter pigs-in vitro muscle protein turnover at slaughter, circulating IGF-I, performance and carcass quality

Nine litters, each of four female and four castrated male pigs (Duroc x Landrace x Large White), were allocated to four treatments according, to sex and weaning weight, from weaning at day 28 until slaughter at day 140. AA-pigs and RR-pigs were fed ad libitum or restrictively throughout the experiment, respectively. R(28-80)A- and R(28-80)A-pigs were fed restrictively from day 28 to day 80/90 and then fed ad libitum until day 140, respectively. At day 80, AA-pigs were 5-6 kg heavier than restrictively fed pigs. At slaughter, the weight of carcass and muscle tissue of RR-pigs was significantly lower than the other three treatment groups, which were similar. The latter finding was a result of a 7% higher daily gain of R(28- 80)A- and R(28 -90)A-pigs from day 80/90 until slaughter compared with AA-pigs. This compensatory growth response was due to a 5% improved feed efficiency. At slaughter, indicators of muscle protein synthesis and in vitro muscle protein degradation were the highest in R(28-80)A- and R(28-80)A-pigs and the lowest in RR-pigs. At day 90 and day 140, insulin-like growth factor I (IGF-I) was the lowest in restrictively fed pigs compared with pigs fed ad libitum at the time of measurement. Overall, the compensatory growth strategy was more efficient compared with the ad libitum strategy. Changes in muscle protein turnover accomplished compensatory growth, and perhaps the growth honnone-IGF-I axis plays a role in mediating this effect. (C) 2003 Elsevier B.V. All rights reserved.