第三十卷(2001)
高乳量牛群乳質性狀選拔
吳明哲 張菊犁 李素珍 曾青雲 陳志毅 李世昌 黃鈺嘉 張秀鑾
行政院農業委員會畜產試驗所
乳量與乳質是泌乳牛群改良的重要經濟性狀。乳質性狀有脂肪率、蛋白質率、乳糖率和體細胞數。乳品工廠逐漸注重生乳體細胞數，並要求酪農生產高品質的生乳，因此，乳質性狀選拔是牛群育種的重要項目。在2001年1月至10月期間，參加個別牛隻乳樣品質檢測戶有290戶，生乳乳樣計有148251頭次。在不矯正個別乳量時，每日乳量平均21.4㎏，脂肪率平均3.82%，蛋白質率平均3.27%，蛋白質脂肪比平均0.90，乳糖率平均4.66%，總固形物(%)平均12.45%，體細胞數平均41.5萬／毫升。體細胞數的場平均在30萬／毫升以內者，有93戶，進一步比較總固形物含量的場平均，在12.45﹪以上者，有42戶。當以夏季7月份乳量為基準，把超出族群平均者，視為乳量高的牛群，並就個別牛予以計算乳質選拔指數，篩選後的母牛群可登錄為耐熱品系。在2001年7月參加乳質檢測的泌乳牛有16384頭，其305-2X-ME乳量之平均為6336㎏，場平均超過6336㎏者有48戶，最高者有7751㎏，這些場分佈於苗栗、彰化、雲林、嘉義、台南、高雄和屏東地區，佔當月DHI參測牛群22%。脂肪率、蛋白質率、乳糖率和體細胞數等乳質性狀選拔牛群是以總固形物含量、蛋白質脂肪比和體細胞數所組成的選拔指數，母牛依選拔指數配與進口的冷凍精液，改進目標每日乳量平均28.8㎏，總固形物(%)平均13.44%，體細胞數平均26.6萬／毫升。
關鍵語：乳牛、乳質、選拔。
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.
  
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