Relationship between subclinical hypocalcemia and negative energy balance on the return of ovarian function during the voluntary waiting period of dairy cows

Abstract

Early resumption of ovarian activity has been reported to be an important factor for the reproductive success of dairy cows because of improved uterine health and fertility. However, early lactation is characterized by a period of negative energy balance (NEB) and mobilization of fat reserves, which is highly associated with a longer postpartum anovulatory period. Moreover, the initiation of milk production and excessive utilization of calcium may lead to a subclinical hypocalcemic status that has been linked to deficient fatty acid metabolism in early lactation. Additionally, subclinical hypocalcemia (SCHP) can result in decreased progesterone (P4) and corpus luteum (CL) functionality, which further decreases reproductive performance in high-producing dairy cows. The objective of this study was to determine the influence of SCHP and NEB during the first 2 weeks in milk on the ovarian activity during the voluntary waiting period of dairy cows in herds with automatic milking systems (AMS).