Evaluation of standardized ileal digestible lysine requirement of nursery pigs from seven to fourteen kilograms.
Four experiments were conducted to determine the standardized ileal digestible (SID) Lys requirement of pigs (Sus scrofa) from 7 to 14 kg. In Exp. 1, 294 pigs (6.8 kg BW) were used in a 28-d growth trial with 7 pigs per pen and 7 pens per treatment. Treatment diets were fed from d 0 to 14, and a common diet was fed from d 14 to 28. The 6 SID Lys levels tested were 1.15, 1.23, 1.30, 1.38, 1.45, and 1.53%. The diets were corn- and soybean-meal [Zea mays L. and Glycine max (L.) Merr.] based, with 10% spray-dried whey, 4.5% fish meal, and contained 3.37 Mcal of ME/kg. From d 0 to 14, ADG increased (quadratic, P < 0.001) as SID Lys increased from 1.15 to 1.30% with no further increase at greater levels. Gain:feed increased (linear, P < 0.001) with increasing SID Lys. Experiments 2 to 4 were 14-d growth trials with diets containing 1.22, 1.32, 1.42, 1.52, or 1.62% SID Lys. Diets were corn- and soybean-meal based with 3.45 Mcal of ME/kg. Soybean meal and lactose were constant in all diets at 30 and 7% of the diet, respectively. In Exp. 2, 840 pigs (7.6 kg BW) were used, with 24 pigs per pen and 7 pens per treatment. Increasing SID Lys from 1.22 to 1.42% increased (quadratic, P < 0.01) ADG and G:F with no further improvement observed in pigs fed the 1.52 or 1.62% SID Lys diets during d 0 to 14. In Exp. 3, 1,260 pigs (8.5 kg BW) were used with 42 pigs per feeder (2 pens per feeder) and 6 feeders per treatment. Increasing dietary Lys increased (quadratic, P < 0.02) ADG and G:F with the greatest response observed as SID Lys increased from 1.22 to 1.32% and, then, slight improvements with 1.42 and 1.52% during d 0 to 14. In Exp. 4, 770 pigs (7.4 kg BW) were used with 22 pigs per pen and 7 pens per treatment. Increasing SID Lys increased (quadratic, P = 0.05) ADG with pigs fed 1.32 and 1.42% SID Lys diets having the greatest BW gains during d 0 to 14. Increased SID Lys decreased (linear, P < 0.001) ADFI and increased (linear, P < 0.001; quadratic, P = 0.02) G:F. In conclusion, results of these experiments indicate that the 1998 NRC Lys recommendations (e.g., 1.19% SID Lys for 5 to 10 kg pigs) are less than required for optimal growth for 7 to 14 kg pigs. One-slope straight broken-line analysis indicated that the SID Lys requirement for optimal growth was at least 1.30% for ADG and 1.37% for G:F, or at least 3.86 and 4.18 g SID Lys/Mcal ME, respectively. Quadratic broken-line analysis indicated that the SID Lys requirement for optimal growth was at least 1.37% for ADG and 1.54% for G:F, or at least 4.19 and 4.92 g SID Lys/Mcal ME, respectively.