SUCCESS OF PROTOCOLS FOR SYNCHRONIZATION OF ESTRUS AND OVULATION IN DAIRY COWS IN SUMMER

Cattle farming, as one of the most important branches of livestock production, has longbeen confronted with the chronic problem of the decline in reproductive performances. In 2005, thenumber of cattle around the world amounted to about 1,370,000,000 heads of cattle, while in 2012this number was just over a billion, which indicates the importance of applying differentreproductive protocols in order to increase production. Heat stress leads to disorders of thephysiological and reproductive processes, as the rise in body temperature caused by heat stress hasdirect negative consequences on numerous cell functions. The study included a total of 54 Holstein-Friesian cows, 28 experimental and 26 control cows from PD Butmir farm with 5 lactations onaverage. Hormone protocols for estrus and ovulation were used in June and July 2013. Cows in theexperimental group were subjected to a Presynch + 5dCoS2 protocol. Cows that did not conceiveafter this protocol were immediately subjected to resynchronization with Cosynch -72 protocol. Thesuccess rate of the Presynch + 5dCoS2 protocol was 19%, while in the case of Cosynch 72 it was33%, which was statistically significant (p <0,05). The first presynchronization and synchronizationprotocol (5dCoS2) did not significantly help to improve the conception rate after the firstinsemination postpartum, but it is evident that they had a positive effect on another protocol (COS72)in the form of reduction in embryonic mortality in the summer months when embryonic loss is thegreatest.The COS72 protocol provides satisfactory results in the summer, but good fitness and healthmanagement, as well as heat stress reduction in accordance with the location and farm design arethe preconditions for a successful estrus and ovulation synchronization program prior to artificialinsemination.