Undernutrition of the Merino sheep and its sequelae. II. The influence of finite periods of arrested growth on the subsequent wool growth, fleece development, and utilization of feed for wool production of lambs

Abstract

Five groups of Merino lambs were subjected to contrasting nutritional regimes during a preparatory period of 400 days. All animals were then restored to a normal diet and during the subsequent 27 months the sequelae to the experimental treatments were measured in terms of wool growth, fleece development, and the utilization of feed for wool production. The most rigorous treatment (growth arrested for 400 days at 15 kg weight) had as its sequel a less dense wool follicle population (adjusted to a standard body weight) and a reduced growth rate of wool during the early recovery period. Total fibre numbers and wool growth per unit of feed intake were also depressed but not significantly so. Fibre diameter, fibre weight, and the ratio of secondary to primary follicles were not affected. The less severe treatments (growth restrictions for 200 days (a) at 15 kg and (b) at 30 kg) influenced none of the parameters under study once a normal diet had been restored. It is concluded that only with extreme under nutrition from early in post-natal life is the wool-producing potential of young sheep likely to be impaired.