ELECTRONIC COMPUTATION OF GROWING AND FINISHING RATIONS FOR PIGS TO MEET U.S. N.R.C. (1959) NUTRIENT REQUIREMENTS WITH AND WITHOUT A MARGIN OF SAFETY

Abstract

Sixty-four castrate male pigs from four breeding groups were individually fed from 50 pounds to market weight of 195 pounds. From 50 to 110 pounds, comparison was made between linear programmed, least cost rations meeting minimum nutrient requirements and those with a 15 per cent margin of safety for protein, lysine, methionine, calcium, phosphorus, riboflavin, pantothenic acid, vitamins B12, A and D. From 110 to 195 pounds, each group was subdivided to compare rations meeting minimum nutrient requirements with those containing 16 per cent protein and corresponding increases in lysine and methionine.Feed intake was not influenced by ration or breeding. Rate of gain, nitrogen digestibility, and efficiency of feed and digestible energy utilization were improved by the margin of safety in nutrients during the growing period and by the higher protein level in the finishing period. Pigs previously receiving the ration with a margin of safety gained more slowly on the 16 per cent protein finisher than those previously receiving the minimum standard ration. Carcass measurements were not significantly changed by ration although area of longissimus dorsi muscle and total R.O.P. score tended to be increased for pigs finished on the 16 per cent protein ration. Breeding groups varied in rate of gain, energy digestibility, efficiency of feed utilization and carcass measurements. For rate of gain during the growing period there was an interaction between ration and breeding group.