Levels of Protein in Practical Rations for the Pig

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Abstract
The protein requirement of the pig at two stages of growth was determined primarily by the equalized feeding technic with practical-type rations containing an antibiotic. Under the conditions of these tests, the pig from 40 to 100 lb. live weight required a minimum of 14 percent protein in a corn-soybean oil meal ration and a minimum of 16 percent protein in a corn-menhaden fish meal ration. From 100 to 200 lb. live weight, the pig needed a minimum of 12 percent protein when either soybean oil meal or menhaden fish meal was used as the source of supplementary protein with yellow corn. For the pig from 40 to 100 lb., menhaden fish meal was less satisfactory than soybean oil meal when fed in 10 percent protein rations, although these two supplements were of equal value in rations containing 18 percent protein. In addition to the effect of the supplementary protein, the distribution of certain essential amino acids in the rations and the corresponding observed performance of the pigs, particularly on low protein rations from 100 to 200 lb., emphasize the importance of the protein level in the corn used in protein requirement studies. Lysine, tryptophan, and methionine content of the rations which supported satisfactory performance was 0.63, 0.13 and 0.23 percent, respectively, from 40 to 100 lb.; and 0.52, 0.10 and 0.21 percent, respectively, from 100 to 200 lb.