DIETARY AND PLASMA BRANCHED-CHAIN AMINO-ACIDS IN TRYPTOPHAN - EFFECT ON VOLUNTARY FEED-INTAKE AND METABOLISM IN THE PRIMIPAROUS SOW

Seventy-six gravid gilts of different genotypes, Yorkshire x Duroc (YD ) and Pig Improvement Company (PIG), were used in two trials to test t he effect of decreasing the dietary ratio of tryptophan: branched-chai n amino acids (BCAA) on feed intake, plasma metabolites, and body weig ht change during a 4-wk lactation period. The dietary ratio of tryptop han: BCAA was .063 in the Control and .041 in the experimental diet (B C). Gilts were fed 1.8 kg/d from d 107 of gestation until farrowing an d given ad libitum access to feed during lactation. Feed consumption w as measured daily. Body weights and preprandial blood samples were tak en on d 107 of gestation and on d 1, 7, 14, and 21 postpartum. Plasma glucose, NEFA, urea nitrogen, ammonia, N-tau-methylhistidine, and alph a-amino nitrogen were measured. The plasma tryptophan:BCAA ratio was h igher (P <.05) on d 1 postpartum than on d 107 of gestation and d 7 po stpartum in the Control group. Dietary addition of BCAA(BC) reduced (P <.06) the plasma tryptophan: BCAA ratio during the early postpartum p eriod compared with the Control group but did not affect the other pla sma metabolites measured. Feed intake was lower (P <.08) between d 6 a nd 12 of lactation in sows fed the BC diet. Regression of d-1 plasma N EFA concentration on d-1 postpartum feed intake was significant (r(2) = .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). Exposure to a low plasma tryptoph an:BCAA ratio during the early postpartum period, through dietary addi tion of BCAA, resulted in a significant decrease in feed intake.