Consequences of elimination of the Rendement Napole allele from Danish Hampshire

An elimination programme was carried out to remove the dominant Rendement Napole mutation (RN⁻) from Danish Hampshire pigs. We reasoned that during and after the elimination of the RN⁻ allele, genetic gain of production traits decreased while rate of inbreeding in the population increased compared to the period prior to elimination. The hypothesis was tested by estimating the genetic gain in seven production traits and measuring the rate of inbreeding in the population prior to and during the elimination period. Genetic gain was reduced for quantitative traits daily gain₃₀₋₁₀₀ kg and feed conversion ratio, while gain for ultimate-pH, lean meat percentage and slaughter loss were increased slightly. There were no changes in genetic gain for daily gainbirth₋₃₀ kg and conformation. RN polymorphism affected several of the quantitative traits. The RN⁻ mutation had a dominant effect on the traits daily gainbirth₋₃₀ kg, daily gain₃₀−₁₀₀ kg, slaughter loss, lean meat percentage and ultimate-pH. It exhibited overdominance for feed conversion ratio and additive effect for conformation. Rate of inbreeding decreased during the elimination of RN⁻. Our findings indicate that the consequences of the elimination programme were not as serious as were feared and that a carefully designed preselection strategy may avoid unacceptable loss of genetic gain and excessive loss of genetic variation.