福岡県農業総合試験場研究報告

肥育前中期における給与飼料中の酸性デタージェント含量の違いが交雑種去勢牛の肉質に及ぼす影響

［摘要］交雑種去勢牛（黒毛和種♂×ホルスタイン種♀）18頭を用いて、給与混合飼料中の繊維成分が産肉性に及ぼす影響を検討した。肥育前期・中期の酸性デタージェント繊維（以下、ＡＤＦ）含量を16％－14％とした増給区と14％－12％とした対照区の２水準を設けて、試験した。その結果、①飼料摂取量・増体ともに両区に差はなく、②枝肉成績は枝肉重量やロース芯面積等に差はなかったが、脂肪交雑や肉色等は増給区が有意に優れていた、③血液中のインスリン濃度は14～18ヵ月齢時に増給区が低く推移した。④胸最長筋断面の画像解析では脂肪交雑粒子の形状係数は増給区が大きく、粗脂肪含量も増給区26.7％と有意に高かった。以上により、交雑種去勢牛の給与飼料中ＡＤＦ含量を前期16％、中期14％にすると肉質が向上し高品質牛肉の効率的安定生産につながると考えられた。

［キーワード：交雑種去勢牛、ＡＤＦ、脂肪交雑、インスリン］

　Effect of Acid Detergent Fiber Content in Feed on Carcass Characteristics of Crossbred Steers. KOGA Tetsuya, Yoshinori HIRASHIMA and Shigeru TOKUMITSU (Fukuoka Agric. Res. Cent., Chikushino, Fukuoka 818-8549, Japan)Bull. Fukuoka Agric. Res. Cent. 19: 81 - 84 (2000)

　Eighteen crossbred steers (Japanese Black × Holstein) were fed from 10 months old to 25 months old (the first fattening period from 10 to 14 months old, middle fattening period from 15 to 19 months old, last fattening period from 20 to 25 months old.) with a differentiated acid detergent fiber (ADF) content in the feed. They were divided into two groups based on the feed. Group A was given feed with a high ADF ratio in the first and middle fattening periods (first period : 16% ADF, middle period : 14% ADF) , group B was fed the control feed (first period : 14% ADF, middle period : 12% ADF).

　With regard to the dry matter intake of the feed, there was no difference between group A and B in body weight gain and final body weight. Their carcass weights and rib-eye areas were equivalent. But, on the carcass characteristics, group A was significantly superior to those of group B. According to a digital computer analysis of marbling, the excellence of group A was definite. The insulin concentration in the blood changed with time. The change in group A was lower for the first and middle fattening periods, and increased during the last fattening period.

　These results suggest that carcass characteristics of crossbred steer would be improved by application of feed with an ADF concentration adjusted to 16% for the first fattening period, and one adjusted to 14% ADF for the middle fattening period.