Jenkins Thomas C, Harvatine Kevin J
Department of Animal & Veterinary Sciences, Clemson University, 117 Poole Agricultural Center, Clemson, SC 29634, USA.
Department of Animal Sciences, Penn State University, 301 Henning Building, University Park, State College, PA 16802, USA.
Vet Clin North Am Food Anim Pract. 2014 Nov;30(3):623-42. doi: 10.1016/j.cvfa.2014.07.006. Epub 2014 Sep 16.
Diets fed to cattle contain mostly unsaturated fatty acids supplied in grains and forages, by-products, and fat supplements. Lipid intake by dairy cattle must be restricted to prevent alterations of microbial populations in the rumen that can negatively affect milk yield. Unsaturated fatty acids consumed by cattle are extensively metabolized through biohydrogenation, intermediates of which include conjugated linoleic acid (CLA) and trans-monoenoic acid isomers. Three specific CLA intermediates of biohydrogenation have been shown to cause milk fat depression in dairy cattle through coordinated suppression of mammary lipogenic genes by a transcription factor that is a central regulator of lipid synthesis.
喂给牛的日粮大多包含谷物、草料、副产品和脂肪补充剂中提供的不饱和脂肪酸。必须限制奶牛的脂质摄入量，以防止瘤胃中微生物种群发生变化，从而对产奶量产生负面影响。牛摄入的不饱和脂肪酸会通过生物氢化作用被广泛代谢，其中间产物包括共轭亚油酸（CLA）和反式单烯酸异构体。生物氢化作用的三种特定CLA中间产物已被证明会通过一种转录因子协同抑制乳腺脂肪生成基因，从而导致奶牛乳脂率下降，该转录因子是脂质合成的核心调节因子。
