GROWTH,PHYSIOLOGICAL FUNCTION AND MEAT PRODUCTION IN CROSSBRED F_1 OF LIMOUSIN (*) *JAPANESE SHOPTHORN (*) CATTLES

本研究旨在探讨引进利木赞（L）品种种质对提高日本短角牛（N）的生长潜力、饲料利用率、生理机能和产肉性能是否有效。(1)测定了LN、NN和日本黑犊牛的体重、日增重和饲料利用率。从出生到12月龄，LN在BW和DG中显著大于NN和BB，但以后两者之间没有差异。在8月龄和16月龄时，LN和NN之间的饲料利用率没有差异。(2)测定了放牧和舍饲条件下LN、NN和BB犊牛的血液成分和循环激素（GH、IGF-1、Insulin）水平，并分析了其性状的遗传差异。饲喂精料后，8月龄时LN的胆固醇、甘油三酯、葡萄糖、GH和胰岛素水平高于NN，8月龄以后，两者之间仅在胆固醇和葡萄糖方面存在差异。(3)皮下脂肪厚度的超声测量在育肥初期LN组与NN组无显著差异，但3个月后LN组显著大于NN组。(4)胴体性状LN与NN无显著差异，但LN的胴体重、眼肌重和肋厚均大于NN，而肋厚小于NN。(5)在四个部位脂肪组织的脂肪酸组成（%）中，LN在C18：0中较大，在C18：0中较小。结果表明，利木赞 * 对NN * 的交配效果主要表现在生长前期的DG、血液成分和激素水平上，但在日本多精料饲养的育肥制度下，对饲料利用率和产肉率影响不大。

This study was carried out to examine whether an introduction of the germ plasm of Limousin (L) breed was effective or not for improving the growth potential, feed utilization, physiological function and meat production of Japanese Shorthorn (N) cattle.(1) Body weight (BW), daily gain (DG), feed utilization were evaluated for calves of LN,NN and Japanese Black (BB). LN was significantly larger in BW and DG than NN and BB from birth to 12 month of age, but later, there was no difference between them. There were no differences in feed utilizationin between LN and NN at both age of 8 and 16 months.(2) Blood components and circulating levels of hormones (GH,IGF-1, Insulin) were evaluated for calves of LN,NN and BB in the term of grazing and housing, and genetic differences in their traits were determined. In response after feeding of concentrate, LN was higher in levels of cholesterol, trigriceride, glucose, GH and insulin than NN in age of 8 month, but later, there were differences between them only in cholesterol, and glucose.(3) Ultrasonic mesurements of subcutaneous fat thickness were no differences between LN and NN in start of fattening, but after three months, LN was signifficantly larger than NN.(4) Carcass traits were no signifficant differences between LN and NN,but LN tended to be larger in caracass weight and eye muscle and smaller in rib thickness than NN.(5) In fat acid components (%) of four position fat tissues, LN was larger in C18 : 0, and smaller in C18 : 1 than NN,and percentage of saturated fat acid to total fat acid were larger in LN than NN.These results demonstrated that the mating effectiveness of Limousin * to NN * were shown in DG,blood components and hormone levels in earlier growth stage, but there were not effective in the feed utilization and meat production under the Japanese fattening system of much concentrate feeding.