Failure of dietary amino acid supplementation at weaning to influence reproductive traits of sows1

Primiparous and multiparous sows received a single dietary supplement of either L-tyrosine, L-phenylalanine, or L-glutamate in their feed on the day after weaning and effects on various reproductive traits were evaluated in three experiments. In Exp. 1 and 2, sows received either 0 (control; n = 22 and 64, respectively) or 100 mg of L-tyrosine/kg BW (n = 24 and 62, respectively) on the day after weaning. In Exp. 1, days from weaning to estrus (5.5 ± .3 vs 5.3 ± .3 d) and ovulation rate (15.6 ± .9 vs 15.6 ± 1) were similar in control and tyrosine-supplemented sows. In Exp. 2, interval from weaning to estrus was extended (P < .01) in tyrosine-supplemented sows (6.4 ± .5 d) compared with controls (4.5 + .5 d), but this was due to long return intervals in 7 of 62 tyrosine-supplemented sows. Total number of pigs born (10.2 ± .4 vs 10.0 ± .4) was similar in control and tyrosine-supplemented sows. In Exp. 3, sows received either no supplemental amino acids (n =31) or their diet was supplemented with 100 mg/kg BW of either L-tyrosine (n = 31), L-phenylalanine (n = 33), or L-glutamate (n = 32). Neither days from weaning to estrus nor subsequent farrowing traits were altered in sows that received supplemental amino acids on the day after weaning. In conclusion, a single dietary supplementation of either tyrosine, phenylalanine, or glutamate to sows on the day after weaning failed to improve interval from weaning to estrus, ovulation rate, or litter traits at subsequent farrowing.