ntributestothesupplyofglucosetothecow.大部分丙酸在肝脏中被转化成葡萄糖。此外,肝脏可利用氨基酸合成葡萄糖。这是一个重要的生糖途径。因为通常没有葡萄糖从消化道中吸收,而奶牛中所含的全部糖(20公斤牛奶含900克糖)必须由肝脏合成。一个例外的情况是当奶牛摄入大量富含淀粉的精饲料或一种抗瘤胃发酵的淀粉源,没有发酵的淀粉进入小肠并在小肠消化成葡萄糖,经小肠壁吸收后转运至肝脏,为奶牛提供葡萄糖源。5、ADDEDLIPIDSINDAIRYRATionS奶牛日粮中脂的补充Lipidscontainabout2.25timesmoreenergythancarbohydrates. Also,lipidsaresometimesreferredtoasa"cold"nutrientsbecauseduringdigestionandutilizationbythebodytheyproducelessheatthancarbohydratesandproteins. Thus,increasinglipidsindairycowrationsmayhaveseveralpotentialbenefits:?Increasethecaloric(energy)densityoftheration,especiallywhenintakemaybelimitedasinhighForagediet;?Limittheneedforcarbohydrate-richconcentrateswhichareusuallyrequiredinearlylactationwhenacowisinnegativeenergybalance;?Inhotweather,lipidsmayhelptoreducetheheatstressofalactatingcow.
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