吳明哲 張菊犁 李素珍 曾青雲 陳志毅 李世昌 黃鈺嘉 張秀鑾
SELECTION ON MILK QUALITY IN HIGH YIELDING DAIRY COWS
M.C. Wu, C.L. Chang, S.J. Lee, C.Y. Tseng, J.Y. Chen, S.C. Lee, Y.C. Huang and H.L. Chang
Taiwan Livestock Research Institute, Council of Agriculture
Milk yield and quality are major economic traits of dairy herd improvement. Milk quality traits are fat%, protein%, lactose%, and somatic cell counts (SCC). In order to meet the requirements of modern dairy factory with an upper limit of 300,000 cells/ml on SCC, selection on milk quality is a major concern in dairy herd improvement program at present. In analysis of 148251 milk samples from January to October of 2001on 290 farms, means for daily yield of milk was 21.4 Kg with 3.82% of fat, 3.27% of protein, 4.66% of lactose, 12.45% of total solid content, and 415,000 cells/ml of SCC. There were 93 farms with their SCC values were less than 300, 00cells/ml, furthermore, 42 farms with the total solid content greater than 12.45%. Therefore, selection index will be formed with total solid content, protein to fat ratio and SCC after mid-term lactation. In July of 2001, the population mean of 305-2X-ME milk yield was 6336 Kg from 16384 milking cows. High yielding dairy herd was defined as herd with milking yield mean greater than population mean, 6336kg. A total of 48 herds were classified as high yielding herds with mean of top one herd being 7751Kg. Farms of 48 high yielding herds were scattered along western region of Taiwan, which accounted for 22% of total testing herds concurrently. Quota of frozen semen with high breeding value will be distributed by selection index. The selection goals of the high yielding population are 28.8 Kg daily yield, total solid content 13.44% and SCC 266,000 cells/ml.
Key words: Cow, Milk quality, Selection.