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Fifteen cross-bred male lambs (Dorset × Small Tail Han), aged 7 weeks, with average liveweight of 13.8±0.8 kg, were used to study effects of feeding mixed volatile fatty acid (VFA) sodium salt on insulin-like growth factor-I (IGF-I), insulin-like growth factor-binding protein-3 (IGFBP-3) in plasma and rumen tissue and rumen epithelium development. The lambs were randomly divided into 5 groups with 3 lambs in each group. Graded levels of mixed VFA sodium salt (the molar proportion of acetate, propionate, and butyrate was 65:25:10), i.e. 0, 5, 15, 30 and 60g/d was added into milk replacer as experimental treatments I, II, III, IV and V, respectively. The trial lasted 24 days. No differences were found in plasma IGF-I and IGFBP-3 between different treatments (P>0.05), or in IGF-I and IGFBP-3 in rumen dorsal sac and in IGF-I in ventral sac between different treatments (P>0.05), while IGFBP- 3 of treatments IV and V was higher than other treatments in ventral sac (P<0.05). In rumen dorsal sac, the length and density of rumen papillae of treatments III, IV and V were higher than treatment I (P<0.05) while no differences were found in the width and surface area of rumen papillae between different treatments or in length, width, density and surface area of rumen papillae in ventral sac between different treatments (P>0.05). It was concluded that feeding mixed VFA sodium salt up to 60 g/d per lamb in milk replacer had no significant effect on development of rumen epithelium.
Key words: volatile fatty acid sodium salt; insulin-like growth factor-I (IGF-I); insulin-like growth factor-binding protein-3 (IGFBP-3); rumen epithelium; lambs.