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112.乳牛初產月齡提早趨勢

吳明哲(1)、林秀蓮(1)、賴永裕(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)、周文玲(3)、王忠恕(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

本研究依泌乳牛分娩年統計各初產月齡之頭數百分比，作為選育初產月齡早的耐熱型乳牛。本研究自www.angrin.tlri.gov.tw資料庫選取2001年1月至2013年9月間DHI乳牛產犢月齡記錄，進行乳牛初產月齡及其乳量乳質研究。於2002年有5,900頭初產母牛，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%；於2012年有4,969頭初產母牛，初產月齡為24、27或30月齡以內的頭數百分比分別有25%、60%或81%；近十年來，兩歲齡前產犢的初產母牛頭數百分比已增加2.5倍。2012年有180,957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23.36Kg、3.82%、3.24%、4.79%、34萬細胞/mL、11.0mg/dL、191mg/dL、以及0.87。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，顯示已能選育適應濕熱環境且初產月齡提早到24月齡以內之乳牛品系。

關鍵語：乳牛、選育、乳質

TREND IN AGE AT FIRST CALVING BY YEAR FOR DAIRY CATTLE

M. C. Wu(1), H. L. Lin(1), Y. Y. Lai(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), W. L. Chou(3) and C. S. Wang(3)

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

Lactation records from the national dairy database at www.angrin.tlri.gov.tw were used to determine calving ages across time. Data were used to study on trend in age at first calving from January of 2001 to September of 2013. Cows calving in 2002, their age of first calving within 24, 27 or 30 months were 10%, 34% or 69% of 5,900 cows, respectively; as calving in 2012, there were 25%, 60% or 81% of 4,969 cows. There were 2.5 times of increase on percentage of first calving within 24 months in last 10 years. In 2012, daily milk yield, milk fat (F), protein (P), lactose, somatic cell counts, urea nitrogen, citric acid and P/F ratio from 180,957 milk samples had yearly mean of 23.36Kg, 3.82%, 3.24%, 4.79%, 340x103/mL, 11.0mg/dL, 191mg/dL, and 0.87, 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, trend in age at first calving with 24 months old was observed and a line of heat-tolerance of dairy cattle was selected.

Key Words: Dairy cattle, Selection, Milk quality