Effect of an increasing the somatic cells on milk yield and its composition in Holstein dairy cows

Breeding the dairy cattle for milk and meat products play an important role in the nutrition of human societies and their economies. Effective performance of this sector, it is necessary to continue operating. The final quality of dairy products is dependent on the quality of raw ingredients. Milk processing depends on physical, chemical properties of milk from the farms. Optimum and maximum daily milk yield will be achieved if properly mastitis control programs and health environment is desirable. Mastitis is one of the most important diseases in the dairy industry that causes widespread losses due to reduced milk production and milk quality, and increased health care costs. Mastitis can be controlled through proper hygiene. In addition, genetic selection can be used to prevent mastitis of cows either directly or indirectly. This study was conducted to investigate the effect of parity, season of calving, months and days in milk recorded on the level of somatic cells also the effect of increasing number of somatic cells on quantity and composition of milk were studied in dairy cows.
The information of 1250 Holstein cows was used from 2010 to 2012. The information was including registration numbers of cows, record date, date of birth, parity, record number of somatic cells, fat and protein percentage. After collecting data, the necessary corrections were made on the data. After correction of 13250 data records of milk production and somatic cell count, 10189 records remained. Fat and protein data contained 7110 records. Outliers in this study contained data from outside the domain of δμ ± 3. To delete outlier data and determine the minimum and maximum of acceptable values for data SAS version 1.9 (2003) and univariate procedure were used.
Based on the results obtained during the study, the average milk yield, average fat and protein production were calculated 37.1, 2.77 and 3.28kg, respectively. The results showed that a high percentage of fat in milk samples of cows with low milk production. With increasing parity, animals are susceptible to the subclinical mastitis disease. The results have indicated a significant effect of season of calving (P In overall, the survey results indicate a significant negative relationship between somatic cell score, with milk yield (P