Determination of responses of growing pigs to dietary energy concentration

The responses in growing pigs to balanced diets at different dietary energy levels are estimated from published data after recalculation of digestible energy (DE) levels using standard tables. Although responses in live weigh t gain (ADG), food intake (FI), digestible energy intake (DEI) and food con version effciency (FCE) are calculated it was not the purpose of this paper to quantify the absolute relationship between these variables and dietary energy levels but rather to apply the general responses to formulate feeds to optimize profit margins. Linear regressions of ADG, Fl, DEI and FCE on D E accounted for 82, 97, 97 and 93%, respectively, of the variation amongst the 15 estimates of the responses. Most of this variation was accounted for by difference amongst the constant term of the various experiments, which implies small differences amongst the slopes. The genotype of pig and live weight were found to be important in influencing the rate of response in so me characteristics. The optimum nutrient density of the feed chosen will de pend upon the efficiency of feed utilization, the cost of the feed and the income derived from the end product. The energy level at which margin over feed costs are maximised will be the optimum nutrient density.