Influence of quality of dietary protein supplement and anabolic steroids on muscular and skeletal growth of foals

Abstract

AbstractTwenty-two weanling foals, about 7 months (215 days) old, were allotted to two groups. One group received high-quality protein (HP; milk powder) and the other received poor-quality protein (PP; barley protein). In addition, six foals in each group were injected intramuscularly (1 mg/kg body weight) with an anabolic steroid (Nandrolon lauras, Laurabolin vet®) at intervals of 3 weeks from weaning to 12 months (362 days) of age. Skeletal and muscular measurements from foals were also made at intervals of 3 weeks. Closure of the right distal growth plate was assessed radiographically in 13 colts in their 2nd and 3rd years of life. Blood samples were taken to investigate the blood chemistry. The HP-group foals gained weight faster from weaning to 12 months of age and were heavier at the age of 12 months than the PP-group foals. The growth of longissimus dorsi muscle and cannon bone circumference were also significantly greater in the HP-group foals. The high-quality dietary protein supplement also increased serum amino acid concentrations and haemoglobin and packed cell volume values. The foals treated with the anabolic steroid increased in body length more slowly from weaning to 12 months of age than the untreated foals. Growth plates closed about 1·5 months later in the horses treated with anabolic steroid than in the untreated horses. Weanling foals seem to require a protein supplement rich in lysine for their optimal growth. More than 31 g/day (0·46 g/MJ metabolizable energy) lysine can be recommended up to 10 months of age.