Effects of Dietary Standardized Ileal Digestible Ile:Lys Ratio on Growth Performance of 6 to 11 Kg Pigs

Two experiments evaluated standardized ileal digestible (SID) Ile:Lys on nursery pig growth performance. In Exp. 1, 280 pigs (PIC 327×1050, 6.7 kg BW) were fed experimental diets for 12 d with 8 replications and 5 pigs/pen. In Exp. 2, 280 pigs (DNA 600×241, 6.0 kg BW) were fed experimental diets for 18 d with 8 replications and 5 pigs/pen. Pens were allotted in a randomized complete block design to 1 of 7 treatments containing 40, 44, 48, 52, 54, 58, or 63% SID Ile:Lys. Dietary SID Lys was 1.28 and 1.24% for Exp. 1 and 2, respectively. Diets contained 1.5% spray dried blood cells and 10% field peas. Responses were evaluated with base models and dose response best fitting models. In Exp. 1, ADG increased linearly and ADFI and G:F had quadratic responses as SID Ile:Lys increased. For ADG, quadratic (QP), broken-line linear (BLL), and broken-line quadratic (BLQ) dose response models had similar fit reporting maximum ADG at 64.7, 52.0, and 52.0% SID Ile:Lys, respectively. For ADFI, BLL breakpoint occurred at 50.6% and QP maximum at 56.2% SID Ile:Lys. In Exp. 2, ADG and ADFI increased quadratically as SID Ile:Lys increased. For ADG, BLL and QP had similar fit with maximums at 51.8% and 58.3% SID Ile:Lys, respectively. For ADFI, QP maximum was 57.2% SID Ile:Lys and BLQ breakpoint at 52.0% SID Ile:Lys. In summary, the SID Ile:Lys requirement for 6 to 11 kg pigs ranges from 52% for ADG and ADFI using broken line models to as high as 64% using quadratic models.

	SID Ile:Lys, %							Probability, P <
Item:	40	44	48	52	54	58	63	Linear	Quadratic
Exp. 1
ADG, g1	330	344	342	388	344	358	375	0.005	0.418
ADFI, g2	495	524	546	601	522	574	555	0.002	0.017
G:F3	0.669	0.657	0.628	0.648	0.658	0.625	0.676	0.904	0.043
Exp. 2
ADG, g4	229	247	266	306	263	286	282	0.001	0.016
ADFI, g5	331	370	393	453	395	421	410	0.001	0.003
G:F2	0.690	0.671	0.679	0.677	0.666	0.682	0.687	0.935	0.228
1SEM=8.8 for 40, 48, 52, and 54 % and 14.0 for 44, 58, and 63% SID Ile:Lys.
2SEM=16.6 for ADFI, Exp. 1 and 0.0146 for G:F, Exp. 2
3SEM=0.0096 for 54% SID Ile:Lys and 0.0160 for other treatments.
4SEM=3.5 for 48% SID Ile:Lys and 11.5 for other treatments.
5SEM=7.9 for 48% SID Ile:Lys and 17.3 for another treatments.