Improved soybean protein sources for early-weaned pigs: I. Effects on performance and total tract amino acid digestibility.

Seventy-two Yorkshire pigs weaned at 21 d of age were allotted to one of seven treatments with different protein sources serving as the primary lysine source at the expense of dried skim milk. Protein sources were dried skim milk (DSM), two isolated soybean proteins (ISP), three soybean protein concentrates (SPC), and 48.5% soybean meal (SBM). Average daily gain (ADG) and feed efficiency (G:F) were greater (P < .05) for pigs fed the DSM diet, the two ISP diets, or the three SPC diets during the first 2-wk period than for pigs fed the SBM diet. Average daily feed intake (ADFI) during the 1st wk was lowest in pigs fed the SBM diet. During the 2nd wk on trial and for the first 2-wk period, ADFI among the dietary treatments was similar. Performance of pigs fed either the ISP diets or the SPC diets as the supplemental protein source was equal to the performance of those fed the DSM diet. Average daily gain, G:F, and ADFI during a subsequent 3-wk period were not affected by treatment. Dry matter (DM) and nitrogen (N) digestibilities were greater (P < .01) in pigs fed DSM, ISP, and SPC diets than in those fed the SBM diet. Apparent digestibility of DM, N, and amino acids (AA) improved from wk 1 to wk 2 postweaning in pigs fed SBM but not in those fed DSM. However, digestibilities of these nutrients were similar among pigs fed the DSM, ISP, and SPC diets.(ABSTRACT TRUNCATED AT 250 WORDS)