The Role of Protein Restriction and Interaction with Antibiotics in the Regulation of Compensatory Growth in Pigs: Growth Performance, Serum Hormone Concentrations and mRNA Levels in Component Tissues of the Endocrine Growth Axis

Abstract The present study investigated the effects of protein restriction and antibiotics on the hypothalamus-pituitary-liver growth axis during the compensatory growth of growing and finishing pigs. Growth performance, serum hormones, and mRNA levels of hormones and their receptors in growth axis tissues were recorded for analyses. A total of 64 piglets (Large White × Landrace × Duroc cross) with an initial weight of 10.07±0.14 kg were randomly divided into four treatment groups of 16 piglets per group. The dietary treatments consisted of two protein levels (14% and 20%) and two antibiotic levels (no antibiotics and 20 mg/kg colistin sulfate with 50 mg/kg kitasamycin) in a 2 × 2 factorial arrangement. The study was performed over 30 days for the first stage (S1, restriction phase) and 74 days for the second stage (S2, realimentation phase). The four treatment diets were maintained throughout the duration in the restriction phase. The four groups were fed the same diet in the realimentation phase. The trial period totaled 104 days. Protein restriction decreased body weight (BW), average daily food intake (ADFI) and average daily gain (ADG) in weaning pigs (P