Effect of protein restriction on compensatory growth regulation in pigs

A period of protein restriction has a positive influence on subsequent growth in pigs because it triggers a compensatory or “catch up” growth, which is a physiological and ecological adaptive behaviour in mammals. 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 in order to determine whether protein restriction could serve as a replacement for antibiotic use. A total of 64 piglets were randomly divided into 4 treatment groups. The dietary treatments consisted of 2 protein levels (14% and 20%) and 2 antibiotic levels (none and 20 mg/kg colistin sulfate with 50 mg/kg kitasamycin) in a 2 × 2 factorial arrangement. The trial period totalled 104 d, 30 d for the restriction stage (4 treatment diet) and 74 d for the realimentation stage. The 4 groups were fed the same diet in the realimentation phase. Growth performance, serum hormones, and messenger RNA (mRNA) levels of hormones and their receptors in growth axis tissues were recorded for analyses.

As a result, protein restriction decreased BW, average daily feed intake, and ADG in weaning pigs and induced compensatory growth after feeding a normal diet during the growth of finishing pigs. Average daily gain increased during the last phase of compensatory growth. Protein restriction increased serum GH and leptin and the mRNA levels of liver IGF-1 receptor (IGF-1-R) but decreased serum IGF-1 and the mRNA levels of liver GH receptor (GH-R) and IGF-1 in weaning piglets. Antibiotics increased the mRNA levels of GHRH and decreased somatostatin in the hypothalamus of weaning pigs. Protein restriction and antibiotics had no interactions across the entire trial.

In conclusion, the slowing of growth caused by early protein restriction may be compensated for in the later stages of pig raising, and the mechanism of compensation is related to the regulation of GH, IGF-1, GH-R, and IGF-1-R.

Ju D, Teng T, Bai G, Fu H, Qiu S, Zhao X, Sun Y, Shi B. The role of protein restriction and interaction with antibiotics in the regulation of compensatory growth in pigs: growth performance, serum hormone concentrations, and messenger RNA levels in component tissues of the endocrine growth axis. Domestic Animal Endocrinology. 2021; 74: 106524. https://doi.org/10.1016/j.domaniend.2020.106524