Álvaro García
Lameness in dairy cows has been associated with disruptions in estrus behavior attributed to changes in reproductive hormone levels and stress-induced hormonal imbalances, often resulting in lower progesterone concentrations. While lameness can restrict certain behaviors such as mounting, chin resting, and sniffing, it does not necessarily impair overall physical activity during estrus. Some cows are still capable of exhibiting estrus despite lameness, which may mitigate the perceived severity of the issue.
Maintaining optimal energy balance is crucial for cows to better manage the negative impacts of lameness on reproductive efficiency and estrus expression. Adequate body condition plays a vital role in reducing intervals to the first postpartum estrus and facilitating optimal gonadotropin secretion and ovarian steroid synthesis.
Lame cows typically spend more time lying down and less time standing compared to non-lame counterparts, and they may display reduced expression of estrus behavior, particularly in the early morning. Furthermore, lameness alters social order dynamics among cows, highlighting its multifaceted nature and underscoring the importance of addressing lameness as a welfare concern in dairy farming practices.
What does the research suggest?
A study conducted by the University of Guelph and published in 2023 explored the relationship between postpartum health, estrus detection, and pregnancy outcomes in dairy cows. The study involved 1,743 Holstein cows from two commercial dairy herds in Ontario, Canada, which were enrolled three weeks before expected calving and monitored for health variables until nine weeks post-calving. Various parameters were assessed, including body condition score (BCS), lameness, and blood metabolites. Cows were also examined for purulent vaginal discharge and endometritis via endometrial cytology, and the time to onset of cyclicity was determined through biweekly serum progesterone measurements. Reproductive management for the first artificial insemination was primarily based on estrus detection using activity monitors until at least 75 days in milk.
The study found that estrus was detected in 77% of primiparous and 66% of multiparous cows between 55 and 75 days in milk. Various risk factors, including retained placenta, endometritis, purulent discharge, delayed cyclicity, or a BCS loss of greater than 0.5 points, were associated with a lower probability of estrus detection. Furthermore, the probability of pregnancy at first artificial insemination was lower in cows with endometritis or purulent discharge. Among cows detected in estrus by 75 DIM, risk factors for reduced pregnancy rate by 250 days in milk included difficult calving, metritis, purulent discharge, or lameness.
This study suggested that monitoring postpartum health can help identify cows more or less likely to be detected in estrus and to become pregnant in a timely manner. This could support a selective reproductive management program with targeted interventions based on individual cow health status where close monitoring of each cow becomes crucial.
Additionally, the study reported that estrus was detected in 77% of primiparous cows and 66% of multiparous cows between 50 or 55 days in milk (DIM) and 75 DIM. This suggests that while both primiparous and multiparous cows were capable of exhibiting estrus regardless of lameness status, a higher proportion of primiparous lame cows could still show estrus compared to multiparous cows.
While lameness may affect aspects of estrus detection and reproductive performance, such as delaying onset or reducing the probability of detection, it does not eliminate the cows’ ability to exhibit estrus behavior. Can a lame cow exhibiting estrus still produce milk up to her genetic potential, or are these outcomes independent of each other?
A farm case
Cow 690, a primiparous cow on a European farm, did not undergo drying off, a common practice for first calvers on this farm. About a month before calving, she began experiencing locomotion issues and her score had decreased – 1 point (1-5 scale) by calving. Upon examination of her locomotion score over time, it’s evident she never fully healed, consistently scoring between 0 and -1 on the locomotion scale. This likely impaired her milk production, as she never reached her full potential.
During her peak on day 34 post-calving, she produced 86 pounds of milk, approximately 10 pounds below expectations, and her milk production consistently fell short of expectations until day 144 of lactation. Despite these hurdles, she displayed her first heat on day 72 post-calving and was inseminated, repeating the process in two subsequent heats. Assuming optimum semen quality and proficient artificial insemination (AI) techniques, why did she not become pregnant?
Firstly, suboptimal timing of insemination relative to ovulation can impair successful fertilization. Secondly, underlying reproductive health issues like uterine infections or hormonal imbalances may impact fertility despite heat detection. Moreover, stress induced by lameness can disrupt hormonal balance and interfere with reproductive processes. Compromised uterine health in lame cows may further impede embryo implantation and pregnancy maintenance. Therefore, while a lame cow exhibiting signs of heat may undergo insemination, multiple factors related to timing, reproductive health, semen quality, stress, uterine environment, and overall health can influence the success of conception and pregnancy.
When overlaying the locomotion score graph with the graphs of body condition score (BCS) and milk production, there are clear inconsistencies in BCS. Notably, starting at around 40 days in milk (highlighted by the circle), her locomotion score worsened progressively, coinciding with erratic BCS, and milk production.
Research conducted by Tadich et al. from the Department of Veterinary Clinical Sciences at the University Austral of Chile suggests that as cows become lamer, they become more sensitive to pain, meaning their pain threshold decreases as lameness worsens. This indicates that the original lesion causing discomfort may still be a factor in Cow 690’s ongoing issues.
Several conclusions can be drawn from this farm case:
- Effect of Non-Drying: The decision not to dry off this primiparous cow may have contributed to her locomotion problems and suboptimal milk production.
- Persistent Locomotion Issues: Despite showing heat she continued to experience locomotion issues which suggests an underlying discomfort not adequately addressed.
- Impact on Milk Production: Her persistent discomfort likely impacted on her milk production. This underscores the importance of addressing health issues promptly to optimize productivity.
- Inconsistencies in BCS: While she was able to maintain an overall adequate average BCS, it was quite erratic indicating her overall health and well-being were compromised.
- Pain Sensitivity and Lameness: As cows become lamer, the threshold to pain decreases, and they become more sensitive which likely explains Cow 690’s ongoing discomfort.
- Need for Ongoing Monitoring and Treatment: This case highlights the importance of ongoing monitoring and treatment for cows experiencing health issues.
The example of cow 690 underscore the complex interaction between post-calving health, locomotion issues, and milk production in dairy production. It underscores the need for ongoing monitoring and treatment for cows facing health challenges. By integrating these lessons into dairy management practices, farmers can enhance both cow well-being and farm productivity.
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