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.