Effects of phase of restricting vitamin A on growth and carcass characteristics in different GH genotypes of Japanese Black steers
2009
Oka, A.(Hyogo-ken. Technology Center for Agriculture, Forestry and Fisheries, Kasai (Japan). Animal Husbandry Inst.) | Iwamoto, E. | Tatsuda, K.
We investigated the effects of phase of restricting vitamin A on growth and carcass characteristics in the different bovine growth hormone (GH) genotypes of Japanese Black steers. The GH genotypes of 18 Japanese Black steers used in the present study were AA (n=8) and BC (n=10). The steers in each genotype group were divided into two groups based on phase of restricting vitamin A (12-23 months of age; 16-27 months of age). All steers were injected with 1,000,000 IU of vitamin A intramuscularly every month except phase of restricting vitamin A. The animals in the 12-23 groups were injected with 200,000 IU of vitamin A similarly at the age of 22-23 month. The steers in the 16-27 groups were injected with vitamin A similarly at the age of 26-27 months. All steers were given vitamin A with the feed (400 IU/kg feed) at the age of 23-29 months. (1) The AA group had greater (P0.05) body weight, average daily gain, withers height, heart girth, feed intake, carcass weight, longissimus muscle area and rib thickness than did the BC group. There was no significant difference in marbling score between the AA and BC groups. (2) There was no significant difference in body weight, average daily gain, carcass weight, longissimus muscle area and rib thickness, beef color, or marbling score between the 12-23 and 16-27 groups. (3) In the AA steers, the 12-23 group had lower (P0.05) percentages of oleic acid and monounsaturated acids in intramuscular lipid than did the 16-27 group. (4) These results suggest that phase of restricting vitamin A dose not affect body weight and marbling score despite the GH genotypes, and early restricting vitamin A decreases percentages of monounsaturated acids of intramuscular lipid in the AA steers.
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