Estimation of genetic parameters for milk protein percentage in Iranian native buffaloes using random regression test-day model

In this research data of Iranian native buffaloes which were collected by the animal breeding center of Iran in 20 years from 1993 to 2013 were used. Data for first, second and third parities included 4339, 4439 and 4445 test-day records, respectively, which were distributed in 298 herds. The GLM procedure of SAS was used for determining the environmental effects affecting on milk protein percentage. The fixed effects of herd-test day, year-season and days in milk and age at calving as covariate were fitted in the model of analysis. Genetic parameters were estimated for milk protein percentage on different days in milk using single trait random regression model of the Wombat software. Heritability estimates for this trait in the first, second and third parities ranged from 0.005 to 0.14, 0.03 to 0.7 and 0.005 to 0.24, respectively. The highest heritability for milk protein percentage in the first, second and third parities were estimated in 300th, 300th and 5th days in milk as 0.14, 0.7 and 0.24, respectively. The means of genetic correlation in the first, second and third parities were estimated to be 0.09, 0.98 and 0.95, respectively. The heritability estimates of milk protein percentage were relatively high in this study. Therefore, optimal milk protein percentage can be obtained by selection in Iranian buffaloes.