福岡県農業総合試験場研究報告14（1995） pp 177 - 180
交雑種去勢牛（ＢＤ）の肥育後期飼料のＴＤＮ水準及び
濃厚飼料中の糟糠類と穀類の割合が良質牛肉生産に及ぼす影響
後藤治・中島啓介・福田憲和
交雑種去勢牛（ＢＤ）を用いて，肥育後期飼料の乾物中ＴＤＮ水準と糟糠類と穀類の割合の違いが良質牛肉生産に及ぼす影響を明らかにするために，肥育飼料乾物中のＴＤＮ水準を，肥育前期（１０〜１３カ月齢）は７５％とし，肥育後期（１４〜２５カ月齢）は８０％と８４％の２水準を設定した。さらに，肥育後期飼料の乾物中ＴＤＮ水準８０％では，濃厚飼料中の糟糠類と穀類の割合を３０：７０及び５０：５０の２処理とした。@肥育後期飼料の乾物中ＴＤＮ水準を８０％から８４％に高めると，肥育後期の後半に当たる２１〜２５カ月齢の１ｋｇ増体に要するＴＤＮ量（８．６ｋｇ，９．５ｋｇ）は増加した。歩留基準値が劣り，ロース芯面積（５１．０ｃｍ2，４５．２ｃｍ2）は小さくなり，脂肪交雑（ＢＭＳ ＮＯ：５．５，４．０）は低下した。A濃厚飼料中の糟糠類と穀類の割合を３０：７０から５０：５０に変えると，肥育後期の後半に当たる２１〜２５カ月齢の飼料乾物摂取量（８．３ｋｇ／日，７．６ｋｇ／日）及び，日増体量（０．７６ｋｇ／日，０．６５ｋｇ／日）は低下した。脂肪の融点（２５．７℃，２８．４℃）は高くなり，脂肪の色沢と質等級（４．２，５．０）は優れ
たが，枝肉中の脂肪割合が多くなり，脂肪交雑（ＢＭＳ ＮＯ５．５，３．８）や肉締まり等級（３．３，２．８）は劣った。以上のことより，肥育前期の飼料乾物中ＴＤＮ水準は７５％，肥育後期は８０％とし，濃厚飼料中の糟糠類と穀類の割合は３０：７０とすると，良質牛肉生産の向上につながると思われる。
［キーワード：交雑種去勢牛，後期飼料，ＴＤＮ水準，糟糠類］
Effect of Dietary TDN Levels in the Later Fattening Stage on Fattening Performance of Cross-Bred Steers (Japanease Black x Holstein). GOTO Osamu, Keisuke NAKAJIMA and Norikazu FUKUDA (Fukuoka Agric. Res. Cent. , Chiknshino, Fukuoka 818, Japan) Bull. Fukuoka Agric. Res. Cent. 14 : 177-180 (1995)
Sixteen cross-bred steers (Japanese Black x Holstein) were assigned into three groups based on the diet: 80 % TDN level and wheat bran to cereal grain ratio of 30:70 which belongs to group A, the diet of group B contains 84 % TDN level and wheat bran to cereal grain ratio of 30:70 and finally, the diet of group C contains 80 % TDN level and wheat bran to cereal grain ratio of 50:50. Ten months-old steers were fed with the diet of 75 % TDN level for 112 days in the first fattening stage, and then experimental fattening periods were 336 days in the later fattening stage. The results are summarized as follows; Group A had bigger ribeye area and finer marbring than group B. On the other hand, group C had thicker subcutaneos fat and higher melting-point of fat in the carcass than group A. These results suggest that the diet contains 80 % TDN level and wheat bran to cereal grain ratio of 30:70 in the later fattening stage might produce fine carcass characteristics.
[Key wards : Cross-breds steer, Fattening, TDN level, Wheat bran]
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