Advantages of Increasing Histidine to Lysine Ratios on Growth Performance, Blood Parameters and Histidine-Containing Dipeptides for Weaning Piglets

A total of 192 weaned piglets (Topigs TN70), 26 days of age, with an initial body weight of 7.2 ± 0.5 kg, were used to determine the standardized ileal digestible (SID) histidine (His) to lysine (Lys) ratio required to maximize growth performance. Six dietary treatments with graded SID His to Lys ratios ranging from 0.2 to 0.38 were generated with the supplementation of L-His to a grain-based basal diet deficient in His. At the end of the trial (day 41 post weaning), 72 male piglets were euthanized for the analysis of histidine-containing dipeptides, particularly carnosine, in the M. longissimus dorsi. In addition, blood samples were collected from 72 piglets to determine plasma urea-nitrogen and hematological parameters. Piglets fed low dietary His (SID His to Lys < 0.27) exhibited hemoglobin concentrations below the reference value, indicating anemia. Muscle carnosine content increased linearly with increasing dietary His and did not reach a plateau within the tested range. Based on growth performance responses, the SID His to Lys ratio required to achieve maximum growth performance in fast-growing piglets is 0.34. These findings emphasize the importance of supervising the SID His to Lys ratio, particularly in practical piglet feed formulations.