Can We Improve Cow Efficiency or Manipulate Feeding Strategies to Reduce Inputs?
In most temporal environments, nutrient availability does not match the nutrient requirement of the cow, and for part of the year, nutrient availability is less than what is required to keep a cow at maintenance. Intensively managed agriculture production systems use mechanically harvested feed to fill the deficit between nutrient availability and nutrients required to maintain cow weight. These harvested feeds are often expensive. In open and pregnant cows, the energetic efficiency of allowing cows to lose and gain body energy does not differ from holding cows at constant body energy. This common energetic efficiency allows for the development of management strategies that allow cows to decrease BW during periods of low nutrient availability and subsequently gain BW when grazed forages are available. However, these strategies do not decrease the total energy required by a cow in a production cycle. Production efficiency does not differ between cows that lose BW in the second trimester and regain the BW in the third trimester, and cows managed to maintain maternal BW throughout pregnancy. The nutrient management strategy chosen for the pregnant cow may influence the productivity of the subsequent generation through developmental programing. The timing of nutrient restriction during pregnancy may be a trigger that alters the lifetime productivity of heifers that have experienced a restricted nutrient environment in utero. Nutrient restriction in early pregnancy has been associated with reduced fertility in daughters; however, heifers born to cows that receive elevated nutrients in the third trimester breed earlier than heifers born to cows fed to maintain maternal BW. Recent emphasis on the development of tools to select for feed efficiency in the growing animal may impact subsequent performance of the cow. Residual feed intake (RFI) is a popular measure of feed efficiency in growing and lactating cattle, and EPD are being developed to allow for its selection. One of the outcomes of selecting for lower RFI is a decrease in feed intake. The consequence of selecting for low RFI in growing cattle in the cow herd needs to be explored. USDA is an equal opportunity provider and employer.
Keywords: Beef, Cow, Nutrition