• How Does Mastitis Affect Reproduction?

    How Does Mastitis Affect Reproduction?

    The detrimental effects that mastitis can have on fertility is one of the largest indirect costs of the disease. Mastitis (both clinical and subclinical) has been shown to affect conception rates, compromise embryo development and calf health, as well as increase the risk of calving complications. Poor fertility results in additional costs associated with veterinary services, culling, and low production. The impact of mastitis on fertility can be a significant contributor to your farm’s bottom line.


    Conception

    The metabolic stress associated with mastitis causes cows to be anovular (not cyclic) for prolonged periods of time. Follicular growth is inhibited, preventing ovulation and the inflammation caused by mastitis produces hormones called prostaglandins that are involved with regulating the oestrus cycle. Hormone levels too high or too low at the wrong point in the cycle will prevent regular oestrus and ovulation. A period of approximately 40 days after calving is normal and needed for the reproductive system to heal. This time frame can become longer due to infections and incur non-productivity costs to the farm.


    The disruption of the regular cycle results in increased calving to conception intervals and an increased number of services to pregnancy. Literature from the University of Minnesota states that cows without mastitis become pregnant 25% faster than cows with mastitis. As well, calving to conception intervals of cows with mastitis are 26 days longer. With an estimated cost per day of each open cow, that extended interval translates to a cost of $52 per case (Chebel, 2012). In the example used in the source, decreasing the number of mastitis cases from 35% to 25% in a 1000 lactating cow herd has the potential to save $5000 in reproductive costs.


    Embryo Development & Calf Health

    Once a cow is pregnant, mastitis can also increase the risk of abortion. Decreased metabolic health and efficiency makes it difficult to maintain pregnancy. Studies show that even cows that had mastitis and were successfully treated for the clinical infection have a higher risk of abortion than cows that have never had mastitis (Chebel, 2012). If pregnancy is maintained, fetal development may suffer, resulting in smaller, weaker calves with lower survival rates.


    Mastitis also alters the quality of the colostrum produced by the dam. Since calves are born with no immune system, it is essential that they receive colostrum within 6 hours of birth. Colostrum from mastitic cows has decreased levels of antibodies, vitamins, minerals and proteins, which compromise the calf’s immune system development, GI tract health, and overall growth. There is also some evidence that mastitis causing pathogens can be passed from the udder into the calf’s mouth through suckling, creating an infection reservoir within the herd (Hurley, 2009).


    Risk of Subsequent Diseases

    Mastitis increases the risks of calving complications and subsequent diseases. The increased resources required to fight an infection can lead to exhaustion during calving, increasing the risk of complications during delivery. Mastitis can also be responsible for ketosis and retained fetal membranes after calving. The compromised immune system due to a mastitis infection can increase the risk of uterine infections such as metritis, endometritis and pyometra (National Animal Disease Information Service, 2016).


    Costs of Poor Fertility

    There are many secondary costs associated with poor fertility. As well as the cost of feeding open cows already discussed, cows with poor fertility generally have lower milk yields and generate less income from calf sales. Veterinary service costs are increased due to the higher number of services required to achieve pregnancy and the potential calving complications and secondary health problems that mastitis can induce.


    Many producers choose to cull cows that show consistently poor fertility, but this too can have hidden costs. If large numbers of the herd are being culled because of fertility issues there are potentially cows with lower yields and higher Somatic Cell Counts that are staying in the herd to compensate for the yield loss of infertile cows. There are also costs related to an increase in the number of heifers reared as replacements.


    Conclusion

    Mastitis is a significant source of income loss for dairy farmers. While it is currently impossible to eliminate infections completely, effective control programs, early identification and treatment procedures can limit the effects, including the impact on reproductive health. It is important to closely monitor your herd’s reproductive health by detecting cows in heat, open cows and abortions as early as possible. Controlling mastitis and diligently monitoring your herd’s fertility will not only ensure that milk yield and quality stay high, but also protect the future health and profitability of your herd.


    References

    Chebel, R. C. (2012). Mastitis Effects on Reproduction. SCC Diagnostics Toolbox. United States of America: University of Minnesota.


    Hurley, W. L. (2009, June 15). Types of Mastitis/Modes of Transmission. Retrieved from University of Illinois: http://ansci.illinois.edu/static/ansc438/Mastitis/types.html


    National Animal Disease Information Service. (2016, June 15). Fertility in Dairy Herds Part 7- Uterine Infection. Retrieved from NADIS Animal Health Skills: http://www.nadis.org.uk/bulletins/fertility-in-dairy-herds/part-7-uterine-infection.aspx

     

     

    About the Author

    Anna Schwanke is an undergraduate student at the University of Guelph, Ontario. She is responsible for researching and writing about a wide variety of topics related to dairy cow welfare and management for Dairy Quality Inc. The 10 years she spent living in Australia, as well as her love of travelling, give her a firsthand viewpoint of issues facing the international dairy community. She plans to graduate from the University’s College of Physical & Engineering Science in 2019 and pursue a career in the Life Sciences or Agriculture industry.

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