Abstract: The main objective of animal breeding is to improve genetic merit of the animals to produce more efficiently in the later generations. Production traits (milk, fat and protein yields) are the most important traits which affect the economic efficiency of dairy cows. Connectedness is a statistical approach that could help breeder, under specific animal breeding situations in better deciding for animal selection from different environment. The accuracy of the comparison between EBV’s from different herds depends upon the degree of connectedness between them. Connectedness can be defined as a measure of the relationships between herds or contemporary groups as they affect the accuracy of comparing the genetic values of animals from one herd or group to the other. Data of Holstein cattle of Ardabil from 1990 to 2010 were obtained from the National Animal Breeding Center of Iran. Data included first lactation records of milk, fat and protein yields. Records were adjusted for milking times (2x) and 305 days in milk. Genetic trend was estimated as the linear regression of average estimated breeding values of animals on the birth year. The objective of this study was to estimate the genetic trends for production traits in two cases lack and unlack Genetic Connectedness (GC) between herd (s) of Holstein cattle by using a multitrait animal model and Matvec program.