Calculation of Inbreeding Depression Effects on Subclinical Mastitis Using Three Different Models

Pedigree information of 3972 Holstein cows and bulls, from 1961 to 2008, was used to calculate inbreeding coefficients and their effects on production traits and subclinical mastitis of dairy farm cows inAzerbaijan province,Iran. Inbreeding was included in a linear mixed model as a class variable. Data were analyzed using the PROC MIXED of SAS by MIVQUE method. Results showed that average inbreeding coefficients were inferior in total population and inbred cows (0.8 and 1.3% in total population and inbred cows, respectively). Although the rate of inbreeding coefficients was low, inbreeding had decreasing effects (P 0.01) on milk, fat, and protein yields, while increasing effects (P 0.01) on prevalence of subclinical mastitis. Furthermore, animals with inbreeding coefficients between 0.59 to 1.11%showed a reduction in milk, fat, and protein yields by 2.4, 2 and 2%, respectively; whereas, animals with inbreeding coefficients between 1.11 and 1.75% showed a reduction in milk, fat, and protein yields by 2, 3.7 and 2.7%, respectively.