Genetics of efficient lean meat growth under ad libitum and

The potential benefits of selection for efficient lean meat growth under restricted feeding have been indicated by selection experiments by McPhee et al. (1988) and Cameron and Curran (1995). The earlier selection experiment by McPhee et al. (1988) showed that scale feeding better exposed the genetic variation in partitioning of food into lean and fat deposition indicating that it might be the preferred method of selection for efficient lean meat growth. These results were confirmed by Cameron and Curran (1995) who showed that Large White pigs selected for high growth rate under restricted feeding grew significantly faster than pigs selected for high growth rate performance recorded under ad libitum feeding. Both studies tested pigs during their earlier growth stage. In addition, both selection experiments were undertaken in research herds. The manual labour required to restrict pigs is not feasible in commercial conditions. An alternative might be to use electronic feeders which also allow pigs to be restrictively fed. In addition, pigs can be group penned representing commercial conditions much more closely than single pens. Pigs are less efficient during their later part of the growth period and with the shift to heavier carcases it becomes more important to maintain high protein deposition rates in heavier carcasses. A PRDC funded project (UNE23P) was initiated to estimate genetic parameters for performance traits recorded under ad libitum and restricted feeding in boars and gilts. Results from this project obtained after approximately half of the animals have been performance recorded are summarised within this paper.