Genetic improvement of lean meat growth and feed efficiency in pigs

Optimising selection procedures for feed efficiency and lean meat growth in pigs is important because feed costs form a high cost component of production. In this paper a number of breeding objectives used in pig industries are reviewed and the concept of the linear-plateau growth model is outlined. This concept allows optimisation of selection for feed intake of the growing pig taking the pigs potential for protein deposition into account. This is a first step towards further collaboration between geneticists and scientists from other disciplines in order to gain a better understanding of physiological consequences of selection. The necessity of recording individual feed intake in group housed pigs has led to the development of electronic feeders. These computerised systems provide additional data including repeated weight and feed intake records as well as feeding pattern traits. How to make best use of this extra information in breeding programmes needs to be explored further. Implications of testing pigs under ad libitum and restricted feeding are outlined and results from selection experiments and commercial group house environments are summarised. The comparison of testing procedures shows that restricted feeding benefits selection for lean meat growth. However, in commercial environments the benefits depend on how well variation in feed intake can be controlled. Testing procedures should be expanded to explain a larger part of variation in daily feed intake, as is currently the case. This unexplained variation may be related to the animal's activity, social interactions between animals and response to various stressors that occur in commercial group housed environments.