Criteria Verification of Adaptability in Dairy Cattle of Iran's Industrial Holstein Mega-Farms

One of the main tools of genetic improvement in developing countries is the importation of semen from elite bulls for special characteristics. As the biggest challenge is the adaptability of the semen progeny to new environmental conditions, this study was designed and carried out to investigate the effects of the envi-ronment on the productive life of dairy cows at industrial mega-dairy farms in Iran. Data of 113584 culled cows from 20 industrial Holstein mega dairy farms located in 14 provinces of Iran (March 2006 to February 2022) were collected and analyzed using the chi-square method in SAS 9.4. The results showed that the true productive life (TPL) was significantly affected by the amount of milk production (305/Day/3x) and the peak of milk production (kg/day) and a high degree of positive regression was observed. Ranchers seem to be more careful in keeping highly productive cows because this is a cost-effective measure. To verify the performance of the imported semen, 70 sires with the highest number of daughters were selected. These sires had 23,222 daughters (20.44% of the data) in their covered herds. It is concluded that whatever is mentioned in sire catalogues for the PL and the TPL in the daughters' performance is different based on climate and functional conditions. Thus, it is recommended that a reference population for PL and milk production be created based on the local farm conditions to get optimum adaptability.