Causes and Consequences of Change in the Mature Size of the Domestic Pig

Abstract

Size at maturity is relatively easily manipulated by genetic selection, and selection for increased growth rate, efficiency and leanness in pigs appears to have resulted in an increase of some 30% in mature size over 20 years. A relatively weak association between size maturity and age maturity has meant that selection for rapid protein growth has resulted in the creation of bigger animals. The Gompertz function is chosen as the preferred descriptor for animal growth, and its use allows demonstration of the link between growth rate and size at maturity. Increased mature size is associated with greater costs of maintenance for breeding populations, but also greater productivity and appetite in growing pigs and an improved (leaner) meat at the point of slaughter. Increasing mature size has consequences for, amongst other things, building design, optimum slaughter weight, determination of nutrient requirement, and the efficient production management of breeding sows which must now grow and breed simultaneously.