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48.乳牛初產月齡提早後之乳量乳質研究

吳明哲(1)、林秀蓮(1)、賴永裕(1)、吳建興(1)、張菊犁(1)、李素珍(1)、陳志毅(1)、施意敏(1)、黃英豪(1)、 陳榮泰(2)、丁進來(2)、岳佩瑩(3)、陳中興(3)

(1)行政院農業委員會畜產試驗所 (2)中華民國乳業協會 (3)行政院農業委員會畜牧處

應用DHI資訊把乳牛初產月齡依分娩年統計各初產月齡之百分比，並檢視其乳量乳質性狀變化，作為乳量乳質與提早初產月齡兼顧的選拔依據。因此，本研究自2002年1月至2012年9月間DHI資料庫www.angrin.tlri.gov.tw選取乳牛初產月齡記錄，進行乳牛初產月齡及其乳量乳質研究。於2002年分娩的5,898頭，初產月齡為24、27或30月齡以內的頭數百分比分別有10%、34%或69%；2011年分娩的4,565頭，初產月齡為24、27或30月齡以內的頭數百分比分別有24%、57%或80%；2012年分娩的3,921頭，初產月齡為24、27或30月齡以內的頭數百分比分別有26%、61%或83%。2011年有187,698個乳樣記錄，年平均單日乳產量、乳脂肪率(F)、蛋白質率(P)、乳糖率、體細胞數、尿素氮、枸櫞酸、以及P/F比值分別有24.16Kg、3.70%、3.25%、4.81%、29萬細胞/mL、10.9mg/dL、191mg/dL、以及0.91。當與2002年的220,193乳樣之年平均單日乳產量(21.77Kg)、乳脂肪率(3.73%)、蛋白質率(3.22%)、P/F比(0.89)、乳糖率(4.78%)及體細胞數平均35萬細胞/mL來比較，提早初產月齡後之單日乳量也提高，而乳脂肪率及蛋白質率未受影響，但體細胞數有減少，顯示提早初產月齡後之乳牛產能也改進。因此，台灣乳牛育種策略上，乳量、乳質及繁殖性狀兼顧的選拔方向，也可培育具有適應濕熱環境特色且能在24月齡以內初產的台灣乳牛品種。

關鍵語：乳牛、選育、乳質

REDUCING THE AGE AT FIRST CALVING OF DAIRY COWS AND THEIR SUBSEQUENT MILK PERFORMANCE

M. C. Wu(1), H. L. Lin(1), Y. Y. Lai(1), C. H. Wu(1), C. L. Chang(1), S. J. Lee(1), J. Y. Chen(1), E. M. Shy(1), I. H. Hwang(1), L. T. Chen(2), J. L. Ding(2), P. Y. Yue(3) and C. S. Chen(3)

(1)Livestock Research Institute, Council of Agriculture, Executive Yuan; (2)Dairy Association of ROC; (3)Animal Industry Division, Council of Agriculture, Executive Yuan

Breeding scheme of dairy cattle, selection on milk yield and quality associated with reproductive performance is essential to the hot and humid weather, and therefore selected cows with reducing the age of first calving will become a heat-tolerance line in Taiwan. Data were used to study on reducing the age of first calving and their subsequent milk quality and daily milk yield from January of 2002 to September of 2012 based upon www.angrin.tlri.gov.tw. Cows calving in 2002, their age of first calving within 24, 27 or 30 months were 10%, 34% or 69% of 5,898 cows, respectively; as calving in 2011, there were 24%, 57% or 80% of 4,565 cows; and as calving in 2012, there were 26%, 61% or 83% of 3,921 cows. Daily milk yield, milk fat (F), protein (P), lactose, somatic cell counts, urea nitrogen, citric acid and P/F ratio from 187,698 milk samples had yearly mean of 24.16Kg, 3.70%, 3.25%, 4.81%, 290x103/mL, 10.9mg/dL, 191mg/dL, and 0.91, respectively, as comparison to the average of 220,193 milk samples in 2002 having 21.77Kg daily milk yield, 3.73% fat, 3.22% protein, 0.89 of P/F ratio, 4.78% lactose and 350x103/mL cell counts in 2002. It indicated that cows reducing the age of first calving did not had a significantly less fat% and protein% in milk along with a less somatic cell counts and a higher daily milk yield. In conclusion, selection on milk yield and quality trait in those of cows at first calving with 24 months old would be feasible under a breeding scheme for heat-tolerance and early mature dairy cattle in Taiwan.

Key Words: Dairy cattle, Selection, Milk quality