Abstract
A total of 149 dairy cows was used to explain physiological influences of the number of mastitis infections (NMI). The relationship between NMI and some productive and reproductive traits was studied. These traits were daily milk yield (DY), lactation period (LP), days open (DO) and number of services per conception (NOS). Data of this experiment were divided into two groups. The first group included cows with clinical mastitis infection during different lactating seasons and the second included non-infected cows. Results of this experiment showed that mastitis infection had deleterious effects on both productive and reproductive traits. DY of the second group was higher by 54.7% than in the first. NOS of the second group was lower than that of the first. There were negative correlations between mastitis infection and productive traits especially with DY (-0.39). Repeatability of the high NOS within the first group was 0.35 and it was higher than that of the other traits of the same group. It could be concluded that mastitis infection had a correlation with bad conditions of housing systems and high milk production 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 reproductive traits especially NOS which increases the calving interval and reduces the productivity of infected cows.