The effect of increasing the dietary valine-to-lysine ratio on sow metabolism, milk production, and litter growth

A study was conducted to investigate the effect of increasing the dietary valine-to-lysine ratio (Val:Lys) for lactating sows weaning more than 12 piglets. Five hundred fifty-eight sows (parity 1 to 4) were allotted to 6 dietary treatments from 2 d post-partum, when litters were standardized to 14 piglets. Diets were analyzed to have a total dietary Val: Lys of 0.84, 0.86, 0.88, 0.90, 0.95, or 0.99: 1. On all 558 sows, BW, back fat thickness (BF), and litter weight were registered at d 108 of gestation and d 2 and 25 (weaning) postpartum. On a subsample of 72 sows, additional measurements were made: sow BW and BF were measured on d 17 and litter weight was measured on d 10 and 17, and blood and urine samples were collected weekly. The litter size at weaning was not affected by the dietary Val: Lys (P = 0.23) and, on average, the sows weaned 13.0 +/- 1.1 piglets. Average daily gain of the litter (2.93 +/- 0.53 kg/d; P = 0.84), litter weight at weaning (P = 0.67), the average milk yield (11.3 +/- 1.4 kg/d; P = 0.49), and milk contents of fat (P = 0.57), protein (P = 0.18), and lactose (P = 0.20) were not affected by the dietary Val:Lys. Increasing the dietary Val:Lys increased the milk concentration of Val (P < 0.05) and Ile (P < 0.01). The change in sow BW and BF were similar for all sows from d 2 to 17, d 17 to 25, and d 2 to 25 (P > 0.05). During lactation, sows, on average, had a BW and back fat loss of 22.1 +/- 12.7 kg and 2.9 +/- 1.7 mm, respectively. Plasma concentrations of glucose (P = 0.26), lactate (P = 0.95), urea N (P = 0.84), NEFA (P = 0.24), and creatinine (P = 0.42); urine concentration of creatinine (P = 0.57); and concentrations of AA in whole blood (P > 0.05) were not affected by the dietary Val:Lys. In conclusion, there was no effect of increasing the total dietary Val:Lys above 0.84:1 on sow metabolism and litter performance during lactation.