ABSTRACT
This chapter focuses on the efficiency of milk production by dairy cattle related to nutrition and genetics focusing on how improving FCE can decrease the greenhouse gas burden of milk production and how FCE can be improved. A key metric of this system efficiency is feed conversion efficiency (FCE), which for milk production is usually defined as energy-corrected milk divided by feed dry matter intake (DMI) and for meat production is live weight gain divided by feed DMI. Relative to the reduction of greenhouse gases and contaminants of water, the simple concept is that the more carbon and nitrogen in feedstuffs captured in the product, the less carbon and N are available for conversion into waste products. The rich and extensive microbiota in the rumen constantly degrades complex carbohydrates in the diet and metabolizes the constituent monosaccharides to the principal shortchain or volatile fatty acids, which are acetate, propionate, and butyrate.
