genetic and trend evaluation of productive and reproductive traits of dairy cattle in razavi khorasan province by using multivariate analysis

in this study, data comprising 10479 production and reproduction records of razavi khorasan province's dairy cattle, were collected by animal breeding center of iran during 1986 to 2006, were used. genetic parameters were estimated by restricted maximum likelihood procedure using wombat software. genetic and phonotype trends were estimated via linear regression as means genetic and phonotype value on year of calving. estimates of heritability for age at first calving (afc), calving interval1 (ci1), calving interval2 (ci2), dry period (dp), milk yield (milk305) and fat yield(fat305) were 0.07±0.02, 0.03±0.01, 0.06±0.02, 0.04± 0.02, 0.31 ± 0.01 and 0.18 ± 0.02 respectively. genetic correlations of milk305 and fat305 with afc, ci1, ci2 and dp were -0.38, 0.89, 0.55, 0.02, -0.39, 0.82, 0.52 and 0.04 respectively. regression coefficient for genetic trend of milk305, fat305, dp, afc, ci1 and ci2 were 8.68±2.5, 0.11±0.07 (kg/year), 0.01±0.001, -0.23±0.15, 0.13±0.04 and 0.1±0.06 (days/year) respectively and phonotypic regression coefficients for these traits were 147.51±12.14, 6.71±0.36 (kg/year), -0.1± 0.001, -5.85±3.2, 0.7± 0.06 and 1.29± 0.9 (days/year), respectively.