Dietary and plasma branched-chain amino acids in relation to tryptophan: effect on voluntary feed intake and lactation metabolism in the primiparous sow.

Seventy-six gravid gilts of different genotypes, Yorkshire x Duroc (YD) and Pig Improvement Company (PIC), were used in two trials to test the effect of decreasing the dietary ratio of tryptophan: branched-chain amino acids (BCAA) on feed intake, plasma metabolites, and body weight change during a 4-wk lactation period. The dietary ratio of tryptophan: BCAA was .063 in the Control and .041 in the experimental diet (BC). Gilts were fed 1.8 kg/d from d 107 of gestation until farrowing and given ad libitum access to feed during lactation. Feed consumption was measured daily. Body weights and preprandial blood samples were taken on d 107 of gestation and on d 1, 7, 14, and 21 postpartum. Plasma glucose, NEFA, urea nitrogen, ammonia, N tau-methylhistidine, and alpha-amino nitrogen were measured. The plasma tryptophan:BCAA ratio was higher (P < .05) on d 1 postpartum than on d 107 of gestation and d 7 postpartum in the Control group. Dietary addition of BCAA (BC) reduced (P < .06) the plasma tryptophan: BCAA ratio during the early postpartum period compared with the Control group but did not affect the other plasma metabolites measured. Feed intake was lower (P < .08) between d 6 and 12 of lactation in sows fed the BC diet. Regression of d-1 plasma NEFA concentration on d-1 postpartum feed intake was significant (r2 = .41; P < .05). The PIC sows showed a tendency for positive lactation body weight response to the BC diet (P = .2), whereas the response of YD sows was not significant (P < .8).(ABSTRACT TRUNCATED AT 250 WORDS)