胎次、泌乳期與季節對牛乳尿素氮濃度之影響

本研究目的為探討乳牛之胎次、泌乳期及季節對牛乳尿素氮（MUN）濃度之影響，及個別牛MUN濃度平均值與該牛群總乳尿素氮濃度之相關，供為牛群飼養管理及營養餵飼調整的依據。自2004年1月至2007年12月，每月1次採取DHI計畫酪農戶個別牛乳分析乳成分與體細胞數，其中含11個參加DHI計畫且常年全量餵飼同一營養配方TMR之酪農戶，於採取個別牛乳當時，同時採取該酪農戶之總乳，分析其乳成分與體細胞數。另自2004年3月至2007年3月，每月1次採取光泉、統一及味全公司所轄酪農戶之總乳，供分析其乳成分與體細胞數。研究結果顯示：於DHI個別牛方面，2004年至2007年每年5月至7月之乳蛋白質率較其他月份者為低，然而除2004年7月及8月之MUN濃度較其他月份低外，2005年、2006年及2007年都無熱季較低的情形；2004年至2007年四年間之月平均，都具有MUN濃度較低時乳蛋白質率較高，而MUN濃度較高時乳蛋白質率較低的趨勢；個別牛於泌乳期產乳量高峰時MUN濃度較高，而胎次對MUN濃度無顯著影響。酪農總乳方面，2004年4月至7月蛋白質率月平均較當年其他月份者為低，2005年3月至2007年3月兩年蛋白質率的變化平穩且相近；2004年至2007年都具MUN濃度較低時乳蛋白質率較高，而MUN濃度較高時乳蛋白質較低的趨勢。以上結果顯示，個別牛於泌乳期產乳量高峰時MUN濃度較高，胎次及季節則對MUN濃度無顯著影響，而季節對總乳尿素氮濃度也無顯著影響，於正常作業下，總乳尿素氮濃度與該牛群個別牛乳尿素氮濃度平均相近者佔73%。建議未參加DHI計畫酪農戶，以其總乳乳尿素氮濃度變化供飼糧調整用時，若泌乳牛未分群飼養者，宜連續數次資料建立牛群總乳乳尿素氮濃度基礎資料，才能穩定顯示牛群狀況，不可以單一個別乳資料來判定牛群狀況，而泌乳牛以乳產量高、中、低分群飼養者，牛群總乳之單一資料無法充分反應分群飼養之狀態，此時仍需依賴分群個別牛隻之平均較為恰當。

關鍵字

乳尿素氮；胎次；泌乳期；季節

並列摘要

This experiment was conducted to investigate the effect of lactation number, stage of lactation and seasons on cow milk urea nitrogen (MUN) concentration, and the correlation of MUN concentration between individual cow's milk and bulk milk, so as to form a managerial reference tool to monitor feeding cows. The study period ranged from Jan. of 2004 to Dec. of 2007. Individual cow's milk was collected monthly from 11 DHI-participating farms that fed their cows with the same TMR year round for tests of milk components and somatic cell counts. While individual cow's milk was taken, its bulk milk was also sampled for tests of milk components and somatic cell counts. Also, bulk milk were taken from satellite dairy farms upon Kuang Chuan, Uni-president and Wei Chuan dairy plants for tests of milk components and somatic cell counts during Mar. of 2004 to Mar. of 2007. The result showed that milk protein% was lowered for DHI individual cow during every May to July from 2004 to 2007. However, MUN concentration was lower only in July and August of 2004. There was no decline in hot seasons in 2005, 2006 and 2007. During 2004 to 2007, there was a trend that monthly average of MUN concentration went down, while milk protein percentage increased, and vice versa. Individual cows had higher MUN concentration during peak of lactation, and number of lactation had no statistical influence on MUN concentration. As regards the bulk milk, the monthly average of milk protein percentage was lower during April to July in 2004. From March 2005 to March 2007, the variations of monthly milk protein% were little and close to each other between those two years. Seasons also excerted no effect on bulk MUN concentration. Under normal procedure, it was 73% of the investigated farms in which the MUN concentration in bulk milk was approximate to that of individual cow's milk average on the same farm. For those who haven't participated in DHI program, they were advised to have their bulk milk sequentially sampled to be referenced as a basis for future improvement in operation.

並列關鍵字

Milk urea nitrogen ； Lactation number ； Stage of lactation ； Season

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