Effect of growth rate in wintering period on the performance for rearing stage of hereford calves grazed on pasture

In the rearing and fattening system with two grazing seasons, the rearing period of 12 months was divided into two such periods as wintering and grazing periods. The present study was to clarify the effect of growth rate in wintering period on weight grains in the next grazing period and to improve the performance for rearing stage of calves. Animals used were 3 groups of 38 steers and 3 groups of 46 heifers finished nursing stage at 7.3 months of age on average in the fall of 1985 to 1987 at the Livestock farm, Faculty of Agriculture, Hokkaido University. In wintering period steers and heifers born in the same year were fed and managed in one group. Feeds given were hay and silage, and formula feed for rearing calves wit daily allowance of 1.3 kg/head. Grass silage (GS) was given in 1985 and 1986, and corn silage (CS) in 1987. Animals were turned out on pasture in one group in the next spring and then heifers were separated to the other group for breeding in September. Average daily gains for steers in wintering period of each year ranged 0.57 to 0.65 kg and the group given CS showed significantly higher daily gain. Average daily gains in grazing period ranged 0.52 to 0.55 kg and a group with higher daily gain in wintering period tended to result in a higher performance for rearing stage. Thus, it is concluded that daily gain in wintering period should be about 0.65 kg to obtain a satisfactory performance of steers for rearing stage. Daily gains of heifers in wintering and grazing periods were about 8% lower than those of steers, but a higher daily gain in wintering period also gave tendency to be a higher performance of heifers for rearing stage. The daily gain of 0.50 kg in wintering period would give a satisfactory result for heifers considering live weight at the first breeding