The variability in the prevalence of subclinical and clinical mastitis and its impact on milk yield of Holstein and Simmental cows as a result of parity

This study analysed over 10 million test -day records collected between January 2005 and December 2022, to determine the prevalence of subclinical and clinical mastitis in Holstein and Simmental cows, and its impact on subsequent milk production. The daily somatic cell count (SCC) served as an indicator of subclinical (200,000/ml to 400,000/ml) and clinical (>400,000/ml) mastitis. The study found that mastitis -related problems increased with parity, and were more frequent in Holstein cows than in Simmental cows. The study identified factors affecting daily milk yield, including lactation stage, age at first calving, farm size, recording season, and breeding region. It was also found that subclinical and clinical mastitis significantly impacted milk production. The day when subclinical/clinical mastitis was detected (D-0) had the lowest milk yield, followed by an increase in milk production in the subsequent recordings. The increase in production varied depending on the form of mastitis, cow's breed (Holstein or Simmental), and cow's parity. The first successive milk recording (A-1) showed the greatest increase in daily milk yield across both breeds and all parities. The increase in daily milk yield was higher following clinical than subclinical mastitis, and was more pronounced in Holstein than in the Simmental breed. After the initial increase in milk production, almost all cows had a decline in milk yield in the subsequent period after subclinical mastitis. Further, a continued increase was observed in all cows after clinical mastitis. The analysis of monthly and total differences in milk production indicated that cows had the highest monthly increase in milk production in the first month after subclinical/clinical mastitis. The highest total increase in milk production was observed in Holstein primiparous cows, which amounted to 44.91 kg after clinical mastitis. In comparison to the Holstein breed, Simmental cows had a lower increase in milk production. Generally, Holstein cows had a better production increase or recovery potential than Simmental cows, particularly after clinical mastitis. Primiparous Holsteins and Simmentals exhibited the highest total production increase in the second parity. The analysis of the animal's recovery capability after the occurrence of a mastitis -related problem revealed that primiparous cows had the lowest initial increase in milk production, but they were able to regenerate more in the total period compared to the older cows with higher initial but lower total increase.