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Is a Dry Period Really Necessary?

机译:确实需要干旱时期吗?

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A dry period of approximately 60 d has been considered the optimal length since the early 1900s (Bachman and Schairer, 2003). The standard of a 305-d lactation and 60-d dry period was adopted during World War II in the United Kingdom and later in theU.S. (Knight, 1998). This management strategy provided the best balance for optimizing milk yield and genetic progress. Today more than 70% of U.S. dairies are managing for a 60-d dry period (NAHMS, 1996). However, several changes have occurred since theadoption of the 60-d dry period. They include improved milk production of 5,000 kg per lactation per cow, greater emphasis on profit, use of artificial insemination and embryo transfer, total mixed rations (TMR), increased milking frequency, altered photoperiod, and bovine somatotropin (bST). Despite these changes, research on a dry period requirement has received little attention.
机译:自1900年代初以来,大约60 d的干旱时期被认为是最佳长度(Bachman和Schairer,2003年)。英国在第二次世界大战期间采用了305天哺乳期和60天干燥期的标准,后来在美国采用。 (奈特,1998年)。这种管理策略为优化牛奶产量和遗传进展提供了最佳平衡。如今,超过70%的美国奶牛场要进行60天的干旱期管理(NAHMS,1996年)。但是,自采用60天干燥期以来,发生了一些变化。这些措施包括提高每头母牛每次泌乳5000公斤的产奶量,更加强调利润,使用人工授精和胚胎移植,总混合日粮(TMR),增加挤奶频率,改变光周期和牛生长激素(bST)。尽管有这些变化,但对干旱期要求的研究很少受到关注。

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