The effect of clinical mastitis infection on productive and reproductive traits in Holstein-Friesian cows under Egyptian conditions

A total of 149 dairy cows was used to explain physiological influences of t he number of mastitis infections (NMI). The relationship between NMI and so me productive and reproductive traits was studied. These traits were daily milk yield (DY), lactation period (LP), days open (DO) and number of servic es per conception (NOS). Data of this experiment were divided into two grou ps. The first group included cows with clinical mastitis infection during d ifferent lactating seasons and the second included non-infected cows. Resul ts of this experiment showed that mastitis infection had deleterious effect s on both productive and reproductive traits. DY of the second group was hi gher by 54.7% than in the first. NOS of the second group was lower than tha t of the first. There were negative correlations between mastitis infection and productive traits especially with DY (-0.39). Repeatability of the hig h NOS within the first group was 0.35 and it was higher than that of the ot her traits of the same group. It could be concluded that mastitis infection had a correlation with bad conditions of housing systems and high milk pro duction of cows. The Egyptian environmental conditions, especially the high temperature and the bad quality of nutrition during the summer season, can also affect this correlation. NMI had an important role in reducing the re productive traits especially NOS which increases the calving interval and r educes the productivity of infected cows.