Determining the Impact of Increasing Standardized Ileal Digestible Lysine for Primiparous and Multiparous Sows during Lactation

Two experiments evaluated the effects of increasing standardized ileal digestible (SID) Lys in lactation on sow and litter performance. In Exp. 1, 111 primiparous sows (Line 241; DNA, Columbus, NE) were allotted to 1 of 4 dietary treatments on d 110 of gestation. Dietary treatments included increasing SID Lys (0.80, 0.95, 1.10, and 1.25%). During lactation, there was no evidence for differences in ADFI or sow BW at weaning (d 21), resulting in no evidence for differences in BW loss. However, backfat loss during lactation decreased (linear, P=0.046) as SID Lys increased. There was no evident for differences in litter weaning weight, litter gain from d 2 to weaning, percentage of females bred by d 7 after weaning, d 30 conception rate, farrowing rate, or subsequent litter performance. In Exp. 2, 710 mixed parity sows (Line 241; DNA, Columbus, NE) were allotted to 1 of 4 dietary treatments at d 112 of gestation. Dietary treatments included increasing SID Lys (0.75, 0.90, 1.05, and 1.20%). Sow BW at weaning increased (quadratic, P=0.046), and sow BW loss from d 112 to weaning decreased (quadratic, P=0.01) as SID Lys increased up to 1.05% SID Lys with no improvement thereafter. Sow backfat loss increased (linear, P=0.028) as SID Lys increased. Conversely, longissimus muscle depth loss decreased (linear, P=0.002) as SID Lys increased. Percentage of females bred by d 7 after weaning increased (linear, P=0.047) as SID Lys increased in parity 1 sows, with no evidence for differences in parity 2 or 3+ sows. Litter weight at d 17 and litter gain from d 2 to 17 increased (quadratic, P=0.01) up to 1.05% SID Lys with no improvement thereafter. For subsequent litter characteristics, there was no evidence for differences in total born, percentage born alive, stillborn, or mummies. In conclusion, results indicate that the optimal level of dietary SID Lys required by the sow may vary based on response criteria and parity.

	SID Lys, %
Exp. 1	0.80	0.95	1.10	1.25	SEM
BW change, kg	-5.1	-5.1	-3.8	-3.4	1.38
Backfat change, mm	-2.5	-2.5	-2.2	-1.7	0.33
Litter ADG d2 to wean, g	2,984	2,959	2,896	2,938	57.3
Exp. 2	0.75	0.90	1.05	1.20
BW change d112 to wean, kg	-35.7	-31.9	-28.5	-31.6	1.50
Backfat change, mm	-1.4	-2.6	-2.8	-2.6	0.44
Loin depth change, mm	-1.9	-1.0	-0.1	0.5	0.61
Litter ADG d2 to 17, g	2,695	2,704	2,887	2,619	43.4