Optimizing Transition Cow Diets

Diet formulation recommendations for transition cows vary widely due to conflicting experimental results, wide variation in feeding programs among well-managed herds, and lack of understanding of the effects of digestion characteristics of feeds on animal response. Physiological changes over the transition period greatly affect feed intake response to diet. Application of a new theory of feed intake control can be used to understand the effects of diet on feed intake of transition cows. The basic premise of the theory is that feeding behavior is controlled by the oxidation of fuels in the liver; increased oxidation results in a satiety signal decreasing meal size, and decreased oxidation results in a hunger signal causing an eating response. Fat mobilization in the transition period increases oxidation in the liver, likely suppressing feed intake. Considerations to control mobilization of fat reserves and increase feed intake of cows after calving are discussed. Also discussed is the importance of maintaining gut fill during this period to maintain buffering, prevent displaced abomasum, and to extend the supply of absorbed fuels when intake decreases at calving. Understanding the function of feeds beyond their energy and nutrient concentrations will help to optimize diets for transition cows. Introduction High incidence of metabolic disorders and infectious disease continues to impact animal wellbeing and dairy farm profitability. This is despite intense interest and considerable research over the last 20 years that has contributed greatly to our understanding of physiological changes during the transition from pregnancy to lactation. The suppression of appetite and the immune system during the transition period increases the risk for fatty liver, displaced abomasum, retained placenta, metabolic disorders such as ketosis and milk fever, and infectious disease such as mastitis and metritis. Sustained depression in feed intake decreases fertility and increases the risk of culling. The overall goal of transition cow management is to ease the transition from pregnancy to lactation by optimizing health and improving long-term milk yield, reproductive success, and farm profitability. The specific goal is to control fat mobilization throughout the transition period to decrease the depression of feed intake and immune-suppression from elevated nonesterified fatty acids (NEFA). The objective of this paper is to discuss the application of a new theory of feed intake control to formulate diets for transition cows. Consideration of the dramatic physiological changes occurring through the transition period and the physiological response to diets will help us to optimize diets to control fat mobilization and increase feed intake of fresh cows, improving animal health, and increase profitability of dairy farms.