Dairy cows

Identification of clinical mastitis by using daily cow behavior and production data

Nuria Garcia

Mastitis remains one of the most important diseases in dairy cattle due to its negative consequences on animal welfare and productivity. Cases of clinical mastitis are generally treated without knowing the underlying cause of the disease, because current diagnostic tools are based on culture or PCR techniques, the results of which take at least one day.

More than 130 bacterial species have been associated with bovine mastitis, only 10 species or groups of species, however, are responsible for 95% of the infections. Most of these pathogens can be classified, into gram-positive (G+) or gram-negative (G-) bacteria depending on the characteristics of their cell wall. This differentiation is important to properly focus treatment, as infections caused by G- bacteria should not be treated with broad-spectrum antibiotics.

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Milk collection for a Bengal rose test

Association between teat-end hyperkeratosis and mastitis

Lucas Pantaleon

What is the relationship between hyperkeratosis and mastitis in dairy cows? Teat-end hyperkeratosis (THK) is a highly prevalent teat pathology affecting dairy cows. It is characterized by a hyperplasia of the keratin layer of the teat orifice as a response to chronic stimuli. Using a severity score from 1 (less severe) to 4 (most severe), studies have found a prevalence between 21% and 46% for grade 3 and between 12% and 19% for grade 4.

Anatomical and physiological mechanisms at the teat orifice play a fundamental role in protecting the mammary gland from pathogens. The stratified squamous cell epithelium acts as a physical barrier, fatty acids have bacteriostatic effects and the muscular layer keeps the teat orifice closed in between milking.

Is hyperkeratosis a risk factor for clinical mastitis?

Different factors at the cow level such as teat shape and position, stage of lactation, parity, … have been associated with the development of THK. Factors at the herd level such as milking management and equipment settings, have also been linked to THK.

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Urine biomarkers of subclinical mastitis in dairy cows

Alvaro Garcia

Mastitis continues to be one of the top two health issues (lameness is the first) in US dairy farms, and one of the main culling reasons. Mastitis is the result of either contagious or environmental bacteria causing inflammation in the udder. Contagious bacteria are spread from a cow with an infected udder to a healthy cow. Environmental bacteria come from the cow’s environment (bedding, soil, manure, etc.) and thus are highly influenced by management practices.

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Risk factors associated with mastitis in automatic milking dairy herds

Lucas Pantaleon

The installation of automatic milking systems (AMS) is becoming more common around the world, as well as larger herd sizes. Risk factors for mastitis in farms using AMS may be different from farms using conventional milking systems (CMS). The reason behind this difference is the different management practices between CMS and AMS. On AMS farms mastitis detection is based on screening with sensors, whilst at CMS detection is done cow side during milking. Another dissimilarity is that udder preparation in AMS farm is done automatically, that is the process is always carried out with the same intensity.

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Importance of udder health during the dry period

Importance of udder health during the dry period

Nuria García-Fernández

Monitoring and optimizing udder health of dairy cows is vital for increasing dairy milk production, sustainability, and economic efficiency. A recent study from Ghent University’s Faculty of Veterinary Medicine analyzed intramammary infections during the dry period using somatic cell count (SCC) data. Milk SCC is often used to determine whether a lactating cow has an intramammary infection. Generally, a cell count above 200,000 cells per mL indicates presence of infection.

The researchers Lipkens et al. (2019) determined rates of mammary infection at dry-off, evaluated whether those infection rates changed across the dry period, and the effects of the infections in the subsequent lactation. The study monitored 739 cows from 33 commercial Holsteins herds located in Flanders (Belgium). Cows had one test-day record before drying off (maximum of 42 days before) and at least 2 test-day records after calving, the first one performed between 12 and 40 days after calving. At drying off, all producers applied a blanket dry-cow antimicrobial therapy and 85% of them additionally applied internal teat sealers.

The results of this study were published in Journal of Dairy Science. The investigators found that:

  • 57.4% of the cows remained healthy throughout the dry period (test-day SCC <200,000 cells/mL before and after the dry period).
  • 8.3% acquired a new infection during the dry period (test-day SCC <200,000 cells/mL before and ≥200,000 cells/mL after the dry period).
  • 23% cured from an existing infection during the dry period (test-day SCC ≥200,000 cells/mL before and <200,000 cells/mL after the dry period).
  • 11.4% remained chronically infected (test-day SCC ≥200,000 cells/mL before and after the dry period).

Therefore, combining these data, the researchers concluded that there was a 12.6 percent risk of getting a new mammary infection during the dry period while the chances of getting cured was 66.9 percent. The new infection risk was calculated by dividing the number of cows with a new infection by the total number of healthy cows at drying off. Similarly, the cured infection risk was calculated by dividing the number of cows with cured infections by the total number of infected cows at drying off. These findings suggest that applying blanket dry-cow therapy at dry-off is not enough to guarantee adequate udder health at calving.

Mammary infection status during the dry period affected the evolution of test-day SCC, clinical mastitis risk, and culling hazard in the subsequent lactation:

  • Test-day SCC after calving was higher in newly infected, cured, and chronically infected cows than in healthy cows.
  • While 7.6% of healthy cows had clinical mastitis during the study, 13.5% of the newly infected, 15.4% of the cured, and 22.7% of the chronically infected cows had mastitis cases.
  • Similarly, culling rate increased significantly from 3.5% in healthy cows to 4.9%, 6.5%, and 11.9% in newly infected, cured, and chronically infected cows, respectively. Therefore, chronic cows were 3.68 times more likely to be culled than healthy cows.
  • Surprisingly, cow milk production was not associated with mammary infections during the dry period.

Interestingly, despite of having low SCC in their first day-test, cows that cured from a mammary infection during the dry period had higher SCC and were more likely to develop clinical mastitis and to be culled than healthy cows. It may be that these cows did not cure bacteriologically during the dry period or that they were more susceptible to new mammary infection due to anatomical damage to their teat canal.

In conclusion, maintaining healthy udders is always important, but it is especially important before drying off and during the dry period as it impacts cow performance in the following lactation. A successful dry-cow program should protect against new infections and cure existing infections. Cows starting the dry period with a mammary infection have higher risk of future infections and are also more likely of leaving the herd during the following lactation.

Reference

Lipkens, Z., S. Piepers, J. Verbeke, and S. De Vliegher. 2019. Infection dynamics across the dry period using Dairy Herd Improvement somatic cell count data and its effect on cow performance in the subsequent lactation. J. Dairy Sci. 102:640–651.