The effects of sire, roughage feeding condition and concentrate composition on the growth rate and carcass composition of the Japanese Black steers

Mitsuhashi, T.; Mitsumoto, M.; Ozawa, S.

Animal Science and Technology 68(4): 403-413

1997


Accession: 009572949

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Abstract
Thirty three Japanese Black steers were used to determine the effect of sire, roughage feeding condition in the first half of fattening period and the composition of the concentrate in the latter half of fattening period on the growth rate, carcass composition and fat content of longissimus muscle. Steers from two sires (Kumokawa 19: n = 17, Hatsuyo 14: n = 16) were allocated in high and low roughage feeding groups (steers fed roughage 55% of their TDN requirement (R): n = 17, steers fed concentrate and roughage ad libitum (C): n = 16) in the first half of fattening period from 9 to 17 months of age. In the latter half of fattening period from 17 months of age to the age obtaining three target body weights (550 kg: n = 9, 600 kg: n = 12, 650 kg: n = 12), animals were fed at two concentrate compositions (mainly flaked barley: n = 17, mainly flaked corn:n=16). The sire group differed significantly in the amount of muscle (P lt 0.05), the weight of kidney fat (P lt 0.001) and the fat content of longissimus muscle (P lt 0.001). The sire group containing more muscle, had a lower weight of kidney fat and a lower fat content in the longissimus muscle. Cumulative TDN intake (P lt 0.001) and the body weight at 17 months of age (P lt 0.001) for R group were smaller than those for C group in the former half of fattening period, whereas the cumulative TDN intake for R group were larger than those for C group (P lt 0.01) and the growth rate for the two groups did not differ in the latter half of fattening period. It was highly significant (P lt 0.001) that the animals of heavier body weight at the start of fattening period (age 9 months) reached their target body weight earlier. Carcass muscle weight and bone weight for C group were significantly (P lt 0.001) heavier than those for R group, whereas carcass fat weight and fat content of longissimus muscle did not differ between the groups. The concentrate fed in the latter half of fattening period tended to cause differences in the amounts of muscle and bone. The animals in the barley fed group tended to have larger amount of muscle (P = 0.08) and bone (P = 0.06) than those in the corn fed group. Significant interactions between sire and concentrate composition on the growth rate was observed. In the leaner sire group, the growth rate of those fed barley was significantly higher than those fed corn (P lt 0.01). Conversely in the fatter sire group, the growth rate of those fed corn was significantly larger than those fed barley (P lt 0.01). Although fat content of longissimus muscle differed at three different target body weights, correlation coefficient between the fat content and the body weight was not significant on a constant age. Correlation coefficient between the fat content of longissimus muscle and the age of steer was significant (P lt 0.05) even on a constant body weight.