Why consider dry cow treatment?
Dry period mastitis linked to lower reproductive performance.

By Dr. Tiago Tomazi, DVM, Ph.D., Dairy Technical Services, Merck Animal Health

It is not surprising that reproductive performance is a major driver of dairy farm profitability. Producers often devote time to improving reproductive management to gain extra points of pregnancy rate. However, they may overlook the impact of mastitis infections on fertility.

Mastitis is often thought of in terms of milk quality – but it can also wreak havoc on reproductive performance. The dry period is a high-risk time for dairy cows, and it’s when mastitis can gain a grip.

During the last three decades, several published studies have investigated how clinical or subclinical mastitis post-calving affects reproductive performance.^1,2,3 A meta-analysis in 2019 combined data from 29 separate studies conducted by The Ohio State University. The analysis set out to document the effects of mastitis on the reproductive performance of dairy cows.³ Comparing cows with mastitis to cows with no mastitis, the authors discovered differences in the following reproductive measures⁴ among cows with mastitis:

Increased days to first service
Increased days open
Differences in pregnancy per artificial insemination
Greater pregnancy loss

Why is the dry period important for udder health?

This data clearly demonstrates that dry period mastitis post-calving has detrimental effects on reproduction, providing even more incentive for dairy farms to reduce new intramammary infections (IMIs) during the dry cow period.

Cows’ greatest susceptibility for mastitis occurs during the first two weeks and the last two weeks of the dry period.² Cows are susceptible during the first two weeks of the dry period due to the following factors:

Discontinuation of teat dipping leads to increased numbers of bacteria at the teat ends
Termination of milking halts the natural flushing effect milking has on pathogen removal from teat canals
Many quarters have a delay or fail to form an adequate keratin plug which helps seal teat ends from bacterial penetration
Leukocytes in the mammary gland are busier removing milk components than protecting it against pathogenic microorganisms

Collectively, these risk factors are reasons that dry cow therapy and internal teat sealants are recommended at dry-off to help reduce new IMI infection risk. During the later risk period, management practices designed to maximize and supplement the cow’s immune defenses and minimize bacterial challenge from the environment are essential.

Prevention is key

IMI infections during the dry period can have a dramatic impact on the incidence and distribution of mastitis in the next lactation. Subsequent mastitis events that occur during the breeding risk period have been shown to have a profound negative effect on fertility.^1,2,3

Consult with your herd health veterinarian to create a comprehensive dry cow program to prevent new IMIs during this critical time and review dry cow mastitis treatment options. With a prevention plan in place, dry cows can be positioned for a strong lactation and have a better chance of reproductive success.

For more information visit this page. 

References

Fuenzalida MJ et al. The association between occurrence and severity of subclinical and clinical mastitis on pregnancies per artificial insemination at first service of Holstein cows. J. Dairy Sci. 2015;98(6):3791-3805. 
Dahl MO et al. Epidemiologic and economic analyses of pregnancy loss attributable to mastitis in primiparous Holstein cows. J. Dairy Sci. 2018;101(11):10142-10150. 
Dolecheck A et al. Quantifying the effects of mastitis on the reproductive performance of dairy cows: A meta-analysis. J. Dairy Sci. 2019;102(9):8454-8477. 
Abuelo, A., Cullens, F., Brester, J.L. Effect of Preweaning Disease on the Reproductive Performance and First-Lactation Milk Production of Heifers in a Large Dairy Herd. J. Dairy Sci. 2021. 104:7008-7017

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