Genetic Improvement of Carcase Value in Livestock

Abstract

<p>Carcase value is predominantly based on hot carcase weight and fat depth without considering price variation in different primal cuts. This research aimed to develop selection strategies to improve carcase value by including valuable primal cuts into existing breeding objectives of pigs and beef. Therefore, this thesis focused on the fundamental requirements, i.e. estimation of genetic parameters for primal cuts and linear or area measurements of live pigs as selection criteria for primal cuts. Further economic values for different primal cuts were derived and predicted genetic responses to evaluate different selection strategies in breeding objectives. Primal cuts were expressed as both weight and percentage traits. Significant exploitable genetic variability in individual primal cuts or groups of primal cuts at a fixed carcass weight was evident for pigs and beef. Heritabilities for primal cuts of pigs were low to moderate. The strongest negative genetic correlation was found between leg and belly primal cuts. Linear and area measurements of pigs were lowly to moderately heritable. Genetic correlations between linear or area measurements and primal cuts indicated that the area measurements were significant selection criteria for all primal cuts in pigs. Beef primal cuts were moderate to highly heritable. Two different primal groups were also derived in beef including high-valued cuts (HVC) and low-valued cuts (LVC), where HVC was highly heritable. Primal cut traits were included in the breeding objectives as a percentage trait rather than weight trait to keep the traits independent of carcase weight. An approach was derived to estimate economic values directly for primal cut traits based on an independent model relevant for primal cuts. In pig breeding objectives, primal cuts were included based on two approaches, either as loin and belly primals separately or as a middle primal. Inclusion of middle primal only was considered better because of the higher response than the inclusion of loin and belly separately in breeding objective. In beef breeding objectives, HVC was included as a breeding objective trait based on two different production systems representing the domestic and Japanese markets. There was a higher response to selection for the Japanese index than the domestic market as the production system for the Japanese market was based on higher carcase values and feed prices. Additional responses were generated for both pig and beef breeding objectives by including valued primal cuts as breeding objective traits. Therefore, expanding knowledge of primal cut traits and including them in breeding programs for both pigs and beef offers new opportunities to improve carcase value in the livestock industry.</p>