Energy Balance and Follicular Profiles Detected by Ultrasonography in Early Postpartum Dairy Cows

Abstract

Early establishment of cyclical ovarian activity following parturition is essential to attain 365-day calving interval. The importance of postpartum energy balance on the resumption of normal ovarian cycles in dairy cows has been recognized in several studies (1). Energy balance is the net result of associations among yield of milk, diet, intake, and use of nutrients by cows. Dairy cattle undergo an energy deficit in early lactation because maximum milk production is attained prior to maximum feed consumption (2). More than 80% of dairy cows experience negative energy balance during early lactation, but magnitude and duration of negative energy balance are variable among cows (8). An extremely negative energy balance will dampen pulsatile secretion of LH (4) and delay ovulation, which contributes to on-farm inefficiency through economic losses associated with postpartum anestrus. Ultrasonic examination of the ovary has been shown to be an accurate and reliable method quantitating ovarian follicle populations (6).The objective of this study was to determine the effects of energy balance on the follicular profiles using ultrasonography in postpartum dairy cows.