Nutrition and Genetics

The chapter discusses the historical changes in productivity of growing farm animals and presents some examples of interactive effects between animal type and nutritional regime on animal productivity. Animal growth is then described in the aspects of nutrient partitioning, which will allow for understanding of the varying responses to nutrient intake in different animal types. Potential implications of introducing novel traits into farm animals via modification of the animal's genome on nutrient utilization are discussed. Via genetic selection, substantial improvements have been made in growth potential and carcass characteristics of farm animals. Interactions between animal genotype and nutritional regime may be better understood when animal types are characterized in aspects of nutrient partitioning. The main aspects of nutrient partitioning for growth are (1) maintenance energy and nutrient needs, (2) whole-body nutrient retention, (3) nutrient retention support costs, and (4) voluntary feed intake. In terms of nutrient retention, special consideration should be given to whole body protein deposition and the partitioning of retained energy between whole-body protein and whole-body lipid. Quantification of the main aspects of nutrient partitioning is extremely useful for estimation of nutrient requirements, for assessing the economic impact of altering feeding strategies in commercial animal production, and for the development of effective animal breeding strategies.