LAUSR

The recent shift of the U.S. swine industry toward improved pork quality, such as color, marbling, and firmness, has led to increased use of Duroc-sired pigs in the marketplace. Our objective was to determine the standardized ileal digestible (SID) Lys requirement estimates for Duroc-sired (600 × 241, DNA, Columbus, NE) pigs from 18 to 128 kg BW. We conducted a series of experiments using corn-soybean meal-based diets with pigs allotted to 6 or 7 treatments in randomized complete block designs. In all experiments an equal number of barrows and gilts were used within a pen. In experiment 1, 300 pigs (initially 18.4 ± 0.50 kg) were used with 5 pigs per pen and 10 pens per treatment with 6 SID Lys levels from 1.00% to 1.50%. Increasing SID Lys increased (linear, P < 0.040) final BW, ADG, G:F, and Lys intake/kg of gain, and decreased (linear, P = 0.012) ADFI. In experiment 2, 608 pigs (initially 36.3 ± 0.91 kg) were used with 7 to 9 pigs per pen and 12 pens per treatment with 6 SID Lys levels from 0.80% to 1.20%. Increasing SID Lys increased (linear, P ≤ 0.036) ADG, G:F, and Lys intake/kg of gain. In experiment 3, 700 pigs (initially 53.2 ± 0.86 kg) were used with 8 to 10 pigs per pen and 12 pens per treatment with 6 SID Lys levels from 0.65% to 1.00%. Increasing SID Lys increased (linear, P < 0.001) final BW, ADG, and Lys intake/kg of gain, decreased (quadratic, P = 0.004) ADFI, and improved (quadratic, P < 0.001) G:F. In experiment 4, 616 pigs (initially 76.4 ± 1.25 kg) were used with 8 to 10 pigs per pen and 5, 6, or 11 pens per treatment with 7 SID Lys levels from 0.58% to 1.00%. Increasing SID Lys increased (linear, P ≤ 0.022) ADG, Lys intake per kilogram of gain, and G:F. In experiment 5, 679 pigs (initially 103.8 ± 1.32 kg) were used with 8 to 10 pigs per pen and 11 or 12 pens per treatment with 6 SID Lys levels from 0.43% to 0.78%. Increasing SID Lys increased (linear, P ≤ 0.043) final BW, ADG, and Lys intake per kilogram of gain, and improved (quadratic, P ≤ 0.032) G:F. Using results from all experiments, the quadratic equation of Lys:calorie ratio, g of SID Lys/Mcal of NE = 0.0002611 × BW2 - 0.0711037 × BW + 7.284 was developed to reflect the requirement for maximal growth performance from 18 to 128 kg BW. Maximal income over feed cost (IOFC) is best described by the quadratic equation: Lys:calorie ratio, g of SID Lys/Mcal of NE = 0.0001558 × BW2 - 0.04030769 × BW + 5.410. These data provide updated SID Lys estimates for Duroc-sired grow-finish pigs.