Abstract Limited arginine (Arg) availability may impact growth performance in the immediate post-weaning period. In addition to its role as a building block for protein, Arg is a substrate for nitric oxide production, a small molecule with roles in immune response and vasodilation, which could have implications for gut functionality in nursery pigs. The objective of this study was to determine the impact of increasing the ratio of dietary standardized ileal digestible (SID) Arg to lysine (Lys) on nursery pig growth performance. A total of 192 pigs (initial body weight, 8.88 ± 1.15 kg) were weaned at 28 days and assigned to one of four dietary treatments (ME, 3,380 kcal/pig; CP, 22.7%; SID Lys, 1.34%; four mixed-sex pigs per pen): 1) R75 (SID Arg: Lys, 0.75; n = 12); 2) R90 (SID Arg: Lys, 0.90; n = 12); 3) R105 (SID Arg: Lys, 1.05; n = 12); and 4) R120 (SID Arg: Lys, 1.20; n = 12). Arginine, above that in the R75 diet, was supplied as crystalline L-Arg; diets were formulated with corn, soybean meal, corn distillers, and corn gluten meal and made isonitrogenous with L-Ala. Pigs had free access to diets for 14 d; body weight and pen feed disappearance were measured weekly, pen fecal samples were collected over the last 3 d of the study, and blood samples for plasma amino acid analysis were collected by jugular venipuncture on day 14. Average daily gain increased linearly from R75 (192 ± 22 g/d) to R120 (222 ± 22 g/d; P = 0.008). Final body weight increased linearly from R75 (11.45 ± 0.33 kg) to R120 (11.88 ± 0.33 kg; P = 0.011). Average daily feed intake was not different among groups, whereas gain-to-feed ratio increased linearly from R75 (0.489 ± 0.027) to R120 (0.530 ± 0.027; P = 0.016). On day 14, plasma Arg increased linearly from R75 (88 ± 10 µmol/L) to R120 (134 ± 11 µmol/L; P = 0.003). Plasma concentration of ornithine, an Arg-related metabolite, also increased linearly from R75 (88 ± 8 µmol/L) to R120 (125 ± 8 µmol/L; P = 0.005). However, plasma Lys concentration decreased linearly from R75 (80 ± 20 µmol/L) to R120 (44 ± 20 µmol/L; P = 0.024). Apparent total tract digestible gross energy and crude protein increased linearly (P 0.05) and quadratically (P 0.001) with increasing Arg intake. In summary, increasing SID Arg: Lys ratio in nursery diets increases nursery pig growth performance in the immediate post-weaning period, likely through increasing overall energy and protein digestibility and driving Lys utilization for body weight gain.
Outlaw et al. (Wed,) studied this question.
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