25 Effects of dietary standardized ileal digestible lysine on growth performance, carcass characteristics, and economics of pigs from 100 to 130 kg

Abstract A total of 1,570 finishing pigs (337 × 1050, PIC; initially 103.4 ± 0.85 kg) were used in a 28-d trial to determine the effects of feeding increasing standardized ileal digestible (SID) Lys to pigs between 100 to 130 kg on growth performance, carcass characteristics, and economics. Before the beginning of the study, the 3 heaviest pigs per pen were removed and marketed with all remaining pigs marketed 28-d later at the end of the study. Pigs were housed in mixed sex pens, with 20 pigs per pen and 20 pens per treatment. The experiment was a randomized complete block design with four dietary treatments: 0.63, 0.68, 0.75, and 0.82% SID Lys. Diets were corn-soybean meal-based and fed in meal form. Dietary treatments were similar in NE and increasing SID Lys was achieved by increasing soybean meal and feed grade amino acids. For the first 14 d from 100 to approximately 118 kg, there was a linear tendency for increased (P = 0.074) average daily gain (ADG), a linear improvement (P 0.05) in gain to feed ratio (G:F), and increase (P 0.001) in SID lysine intake per kg of gain as SID Lys increased (Table). For the second 14 d from 118 to 128 kg, SID Lys intake per kg of gain increased (P 0.001) as SID Lys increased, however; there was no evidence for difference (P 0.10) for any growth performance traits. Overall, there was a linear increase (P = 0.018) in G:F and increase (P 0.001) in SID lysine intake per kg of gain as SID Lys increased. Increasing SID Lys also linearly increased (P 0.05) percentage lean and decreased (P 0.05) backfat depth with no evidence for differences (P 0.10) in other carcass criteria. For economics, feed cost and feed cost per kg of gain linearly increased (P 0.05) as SID Lys increased in both low and high-price scenarios. Income over feed cost linearly decreased (P 0.05) as dietary SID Lys increased in a low-price scenario, but there was no difference between treatments in a high-price scenario (P 0.10). In conclusion, increasing dietary SID lysine in the last 28-d of the finisher period linearly increased G:F and SID Lys intake per kg of gain without significantly influencing other growth performance traits. Feed cost per kg of gain was linearly increased for both low and high-price scenarios with a detriment for IOFC with increasing SID Lys in the low-price scenario.