Effects of Protein Source and Level, and Lysine and Methionine Supplementation on Rate and Efficiency of Gain of Pigs Weaned at an Early Age

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Abstract
Eight hundred eighteen pigs weaned at 3 weeks of age and averaging 12.2 to 13.5 lb. in separate experiments were used in six experiments to determine the influence of source of supplemental protein, level of dietary protein, and lysine and methionine supplementation on rate and efficiency of gain. Inclusion of 3% tankage or fish meal or 10% dried skimmilk in an 18% protein diet based on soybean meal as the major source of supplemental protein did not affect significantly the 9-week weights or daily gains of the pigs. However, inclusion of 3% tankage significantly depressed feed efficiency, and diets containing 3% fish meal or 10% dried skimmilk supported more efficient gains than did the mixtures containing soybean meal alone, or the combination of 3% each of tankage and fish meal. The inclusion of 3% fish meal and 10% dried whole sweet whey, alone and in combination, in a basic 18% protein corn-soybean meal diet did not affect significantly the average 8-week weights or daily gains of the pigs. Corn-soybean meal diets containing 18% protein supported as rapid and efficient gains over a 6-week period in pigs weighing 13.4 lb. initially as did mixtures of similar composition providing greater amounts of protein at all stages of the study. Pigs fed diets containing less than 16% protein during one or more of the successive 2-week periods of the study were significantly less efficient in feed conversion. Intakes of protein, and of isoleucine, lysine and threonine, were quite similar among the several protein level sequences, except for that providing 22% protein continuously, indicating that the pigs tended to consume the diets in amounts necessary to meet their needs for essential amino acids. A 16.7% protein diet based on corn, soybean meal, fish meal and dried whey was significantly improved as measured by both rate and efficiency of gain only when the starter was supplemented with 0.2% L-lysine and 0.1% DL-methionine. The addition of 0.15 or 0.20% L-lysine and 0.05% DL-methionine to a 16% protein corn-soybean meal starter significantly improved feed conversion and made the starter equivalent to an 18% protein diet, but was without effect on final weights or average daily gains. Methionine alone was without significant effect on either rate or efficiency of gain, while the lysine addition tended to improve efficiency of gain without significantly influencing final weights or daily gains. Copyright © 1965. American Society of Animal Science . Copyright 1965 by American Society of Animal Science