Swine Genetic Challenges of the Future: One man’s thoughts

Past improvement from selection: Genetic improvement of swine first began with domestication at least 5,000 years ago and perhaps as long as 10,000 years ago. Development of specific strains or so-called breeds occurred as individual small breeders applied the use of inbreeding and selection to fix or improve characteristics that would later help define lines and breeds. Such processes were confined to breeders at the end of the 1800s when Mendel’s discoveries initiated the field later be to be known as genetics. While small breeders were certainly the rule in the early 1990s the advent of corn breeding companies and the successful development of inbred lines and crosses paved the way for the development of breeding companies. In the beginning a large number of breeding companies and family breeding operations existed. Market pressures, adoption of modern production technology and business models relying on economies of scale have reduced those numbers greatly and have also reduced the number of individual breeders to a very small share of the marketplace. In the swine breeding business very few companies (less than five) now compete world-wide and in the US the market share of the top three companies’ likely makes up 65-70% of the market. In pigs, primary selection for the past nearly 60 years has been devoted to faster and leaner growth. Such selection has had clear and decisive outcomes. From the 1930s phenotypic measures of back fat have been reduced from 45 mm to 15 -16 mm, with growth rates increasing in some cases by well over 50%. This was achieved while increasing market weights from 80 kg to 125 kg. Feed conversion has also nearly halved with the best commercial herds having efficiency ratios of 2.5 -2.6 kg feed consumed to kg gained over the lifetime of the pig. Even in more recent years genetic improvement has continued with reductions in age to market weight of 0.4days/yr in genetic trend (Chen et al., 2002; 2003). Some industry analysts believe fat levels have now reached a minimum. Unfortunately these changes have been accompanied with reductions in marbling and pH causing meat quality to suffer. In terms of number born alive purebreds from smaller breeders have increased and in some breeding companies genetic rates of improvement of 0.2 pigs per litter per generation appear to be the norm.