PROTEIN-ENERGY RELATIONSHIPS IN RATIONS OF EARLY WEANED PIGS

Three experiments involving 134 pigs weaned at 3 weeks of age were conducted to study protein-energy relationships. A cornsoybean oil meal ration was employed in Experiment I, while a ration composed of purified ingredients was used in Experiments II and III. A marked increase in growth rate was obtained when the protein level was increased from 10% to 15% in Experiments I and II. Further increasing the protein content of the ration to 20% resulted in slightly faster gains in Experiment I, but not in Experiment II. A linear decrease in the quantity of feed required to produce a unit of gain was obtained as the protein level of the rations was progressively increased. Increasing the energy density of the ration by the addition of corn oil resulted in an increase in rate of gain with a corresponding improvement in efficiency of feed utilization at both the 10% and 15% protein levels on the purified ration. Under the conditions imposed in Experiments I and II, it appears that a calorie-protein ratio, expressed as productive energy of between 50:1 to 55:1, produced maximum performance. Isocaloric rations containing c/p ratios of 70:1 and 51:1 in Experiment III produced no difference in growth rate although the 51:1 ratio resulted in an apparent improvement in feed efficiency.