برآورد پارامترهاي ژنتيكي صفات تيپ، توليد شير و روزهاي باز در گاوهاي هلشتاين ايران

Genetic Relationships between Linear Type Traits, Milk Yield and Open Day in Holstein Cows of Iran

The objective of the present study was to estimate the relationship between genetic parameters for 13 linear type traits, and milk yield as well as open day in Holstein cattle of Iran. Three data sets of: 16502 (type traits), 16557 (milk yield) and 11631 (open days) records related to the first calving of the cows, and respectively taken from 1500, 1566, and 2000 herd-year-season groups, were taken into account. SAS software and Proc GLM were employed to fit the model. Genetic parameters were estimated using Restricted Maximum Likelihood along with an animal model and ASREML software. Genetic correlation among type traits and milk production ranged from 0.34 (rear udder width) to -0.31 (udder depth), and among type traits and fertility, it ranged from 0.62 (rear udder width) to -0.37 (udder depth). Most of the genetic correlations between milk production and fertility indicate that more production in cows was accompanied by a lower fertility, while cows with a lower production level benefitted from a more fertility rate.