Effects of growth rate during the early fattening period on growth, carcass characteristics and circulating hormones in the different growth hormone genotypes of Japanese black steers
2007
Oka, A.(Hyogo-ken. Technology Center for Agriculture, Forestry and Fisheries, Kasai (Japan)) | Iwaki, F. | Iwamoto, E. | Tatsuda, K.
One of the bovine growth hormone (GH) genetic variants is a substitution of leucine (Leu) to valine (Val) at amino acid position 127 of the protein. The GH genotypes of 14 Japanese black steers used in the present study were Leu/Leu (A, n=7) and Val/Val (B, n=7). The steers in each genotype group were divided into two groups based on intended growth rate (high, 1.0 kg/day; low, 0.6 kg/day) during 10-17 months of age. The overall mean concentration of plasma GH was higher (P0.05) in the A group than in the B group. The serum concentration of insulin-like growth factor-I was higher (P0.05) in the B group than in the A group. The carcass weight of the A group was greater (P0.01) than that of the B group. However, there was no significant difference in carcass weights between the 1.0 kg/day and 0.6 kg/day groups (P0.05). The rib thickness of the 1.0 kg/day group was greater (P0.05) than that of the 0.6 kg/day group. The crude fat content of longissimus muscle was greater (P0.05) for the 0.6 kg/day group compared with the 1.0 kg/day group.
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