By Fernando Diaz and Alvaro Garcia
With feed as a dairy’s largest expense, between 52 and 58 percent of the total cost of producing milk, feed conversion efficiency has been a valuable benchmark to assess profitability. In addition to milk production and dry matter intake (DMI), other parameters that have been associated with efficiency are genetics, breed, age, lactation number, pregnancy status, body weight (BW), BW change and body size.
Cornell University scientists note that improvements in feed efficiency can occur as a result of changes in digestion and nutrient absorption, maintenance requirements, utilization of metabolizable energy for production or nutrient partitioning. Recent reports have suggested Jersey cows present some anatomic or physiological advantages compared to Holsteins. At the same time, research from Washington State University (WSU) using computer modeling reported that, when kept within their thermoneutral zone, a Jersey population would require 20 percent less feed to yield the same amount of cheese as Holsteins. The WSU researchers emphasized Jerseys are more efficient than Holsteins due to their lower BW and higher milkfat and protein content.
According to USDA reports, Holsteins continue to be the predominant dairy breed in the U.S. with no significant population changes between 1996 and 2007. The breed represented 94.4 percent and 92.2 percent of the cows in 1996 and 2007, respectively. Jerseys were the primary breed on only 3.5 percent of farms.
Does a difference between Jerseys and Hosteins exist?
Research that compares the energetic efficiency of Jersey and Holstein cows evaluated by respiration calorimetry is unfortunately scarce. This process measures oxygen consumption, carbon dioxide release and energy given off in the form of heat. Energy balances of multiparous cows fed a total mixed ration (50 percent forage: 50 percent concentrate) throughout one lactation were evaluated using respiration chambers at the Natural Resources Institute at Beltsville, Md.
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