Effect of phase feeding and valine-to-lysine ratio during lactation on sow and piglet performance.

The potential of piglets to grow before weaning is greater than the sow can support, and as such, improving the performance of the lactating sow is a key driver of whole-farm efficiency. This study aimed to investigate the impact of 1) adopting a phased feeding approach during lactation and 2) the ratio of Val to Lys on sow and piglet performance. Multiparious sows ( = 109) were assigned to treatment at 108 d of gestation. Dietary treatments were arranged in a 2 × 2 + 1 factorial design. Dietary treatments included 2 dietary regimes: "Flat" (14.4 MJ/kg DE diet offered for 28 d of lactation) or "Phased" (14.4 MJ/kg DE diet offered until d 14 of lactation followed by a second diet containing 15 MJ/kg DE offered from d 15 to 28 of lactation) and 2 Val:Lys ratios representing "Normal" (0.68:1) or "High" (1.1:1) ratios. A control diet was also offered that contained 13.5 MJ DE/kg, 8.8 g/kg total Lys, and 6.6 g/kg total Val. Treatment had no effect on sow backfat depth, BCS, or weight change during lactation. Compared with control sows, sows offered either the Flat or Phased dietary regime at both levels of Val:Lys ratio weaned, on average, 9 kg extra in litter weight at 28 d ( = 0.006). Dietary regime or Val:Lys ratio had no effect on sow blood urea nitrogen levels at 21 d. A Val:Lys ratio of 1.1:1 increased milk fat at 7, 21, and 28 d ( < 0.05) but increased backfat loss at weaning ( = 0.03). In conclusion, a diet containing 14.4 MJ/kg DE and 0.92 g Lys/kg (the Flat Val:Lys ratio) at an average feed intake of 7.7 kg/d enabled sows to wean 13 piglets to an average weight of 8.6 kg at 28 d.