Maternal and lamb carrier effects of the Booroola gene on food intake, growth and carcass quality of male lambs

Possible correlated or pleiotropic effects on food intake, growth rate and carcass traits (meat quality and carcass composition traits) were investiga ted for the prolificacy related Booroola gene (Fec(B)). This gene was intro gressed in a Texel sheep population by systematic backcrossing with sires c arrying the Booroola gene. In a 3-year experiment 273 spring-born male lamb s were offered concentrates ad libitum, after weaning. Lamb carrier effects and dam carrier effects for the Fec(B) gene were estimated, accounting for year backcross generation, slaughter weight, weaning age, concentrate type , rearing code, age of the dam and litter size as fixed effects. Carriers o f the Fec(B) had a higher dressing percentage (+1.15%), longissimus muscle depth (+0.26 mm to +0.75 mm) and cross-sectional area (+0.98 cm(2)). Howeve r the gene also had a positive effect on subcutaneous fatness (+0.12 points ), KKCF (+30 g) and a substantial positive lamb carrier effect on carcass f at tissue content (+3.09%), which reflects a relative increase in fatness o f 11.9%. The Fec(B) gene had also very small, significant effects on some m eat colour traits. The dam carrier effects of the Booroola gene were negati vely associated with food efficiency and with longissimus muscle depth (-1. 38 to -2.25 mm). The increased fatness of lambs could imply that for optima l use of Fec(B), non-carrier terminal sires should be used on heterozygous dams.