Genetic selection and advanced management practices have significantly increased the milk yield of dairy cows over the past decades. However, this improvement has often come at the cost of fertility, with negative energy balance (NEB) being one of the primary factors responsible. NEB occurs when the energy demands for milk production exceed the energy intake, particularly during the postpartum period. After parturition, energy demands increase dramatically to support milk production, while feed intake remains limited due to calving stress and reduced rumen capacity. This imbalance delays ovarian activity, prolongs the interval to first insemination, and reduces conception rates. To address this challenge, a recent study explored the effects of shortening the dry period (SDP) to 30 days and supplementing prepartum diets with fat on energy balance, reproductive performance, and milk production in dairy cows.
The study was designed to evaluate two main strategies for mitigating NEB. The first experiment investigated the impact of a short dry period on postpartum energy balance and reproduction, while the second experiment examined how combining a short dry period with prepartum fat supplementation influenced energy balance, milk yield, and uterine health. Holstein cows were randomly assigned to one of three treatment groups: a traditional dry period (TDP) of 60 days, a short dry period (SDP) of 30 days, or a short dry period with prepartum fat supplementation (SDP-F). The cows’ energy balance, milk yield, and reproductive parameters were measured throughout the transition period, and data were analyzed using advanced statistical models.
The findings revealed that shortening the dry period to 30 days improved postpartum energy balance by reducing milk production during early lactation. This reduction in milk yield eased the energy demands on the cows, allowing them to recover more quickly from NEB. As a result, cows in the SDP group resumed ovarian activity faster than those in the TDP group, with median days to first artificial insemination (AI) significantly lower in SDP cows (66 days) compared to TDP cows (89 days). Furthermore, the 21-day cycle pregnancy rate tended to be higher in SDP cows, and median days to pregnancy were shorter (85 days versus 125 days in TDP cows). These improvements suggest that a shorter dry period supports faster reproductive recovery and increases the likelihood of successful conception within a shorter timeframe.
In the second experiment, the addition of prepartum fat supplementation in SDP cows further improved outcomes. Cows in the SDP-F group showed higher prepartum body condition scores (BCS) compared to SDP cows, likely due to the additional energy provided by fat in their diet. This higher BCS appeared to mitigate the initial milk loss observed in SDP cows. While milk yield in the first six weeks postpartum was lower in SDP cows compared to TDP cows, the SDPF group produced milk comparable to TDP cows over a 105-day period. This indicates that prepartum fat supplementation can help offset the effects of a shorter dry period on milk production, ensuring that energy balance improvements do not come at the cost of productivity.
Improved energy balance in SDP and SDP-F cows also had positive effects on uterine health. Vaginal mucus scores, an indicator of uterine recovery, were significantly better in cows subjected to SDP and SDP-F treatments compared to TDP cows at 21 days postpartum. While the incidence of metritis was unaffected by treatment, the improved mucus scores suggest faster uterine recovery, which may further enhance reproductive performance. The ability of these strategies to support better uterine health and recovery highlights their potential to address postpartum reproductive challenges.
The study demonstrated that a shortened dry period of 30 days, particularly when combined
with prepartum fat supplementation, can significantly improve energy balance and reproductive
performance in dairy cows without compromising milk production over the long term. By
addressing NEB and its associated challenges, these strategies help ensure faster resumption of
ovarian activity, reduced days open, and improved overall fertility. For dairy producers,
implementing a short dry period and prepartum fat supplementation offers a practical approach to
balancing high milk yield with optimal reproductive efficiency, ultimately contributing to the
health, productivity, and profitability of dairy herds. The writers are PhD scholar and Professor at
Department of Theriogenology, University of veterinary and Animal Sciences, Lahore