Technical review of the energy and protein requirements of growing pigs: food intake

Food intake in pigs is highly variable across different production circumstances. This report concludes from a critical review of published observations that it was unrealistic to expect from the scientific literature purporting to express nutrient requirement any reasonable prediction of the particular food intake of groups of pigs. None the less, such knowledge is essential for the practical purposes of their day-to-day nutrition. The literature does however yield general principles from which may be derived: (a) the likely forms (but not the parameter values) of intake functions relating food intake to pig live weight; and (b) the likely factors involved in the modulation of food intake at any given live weight. Using these principles two methods for determining on-farm food intake from the use of simple and available records were proposed. The first requires knowledge only of start and final weight, the time elapsed, and total food intake: it involves two steps, the determination of a suitable growth curve followed by the fitting of a suitable food intake curve. The second method is appropriate in the absence of information on total food intake, and requires a minimum number of spot measurements through the growth period. Different functions were tested for the curve of best fit. As a further benefit it appeared that models could be constructed from the information presented that would speculate for diagnostic purposes upon the likely modulators of food intake. Such models could explore the constraints of gut capacity, the energetic requirements of maintenance and potential growth, the influence of excessive or inadequate environmental temperature, the quality of housing and stocking density.