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.

: During puerperium phase in cows, uterus goes through involution process, while ovaries restore supressed cyclicity as a result of gestation. After 10-20 days postpartum (PP) luteinizing hormone (LH) levels begin to raise and renewal of cyclicity after parturition is probably most important factor for cows to successfuly conceive again. observed in right ovaries of cows in both groups, while corpora lutea were bigger in multiparous cows. Numbers and sizes of corpora lutea, may give an insight in quality of restoration of ovarian cyclicity and a solid base for prediction on future reproductive performances.

Clinical and subclinical disorders and diseases cause reproductive failures and decline in milk production. Etiology of disorders is mainly because of pathological effect of microorganisms, lapses in nutrition and lodging, as well as in management. After partrition, body is under stress and milk yield is highest, which favors appearance of metabolic and infective diseases. Status of puerperium, number of lactation, body condition score and season of parturition, have highest effect to cyclic ovarian activity. Regular development of dominant follicles, ovulation, formation of corpus luteum and luteolysis is necessary for establishment of regular cyclic ovarian activity, which leads to better fertility. Experiment had included 50 cows during first 52 days of lactation. Cows were separated in two main groups, those with normal puerperium NP (n=32) and abnormal puerperium AP (n=18). Examinations have been performed during period of 6 to 52 days postpartum. Ovarian dominant follicles have been observed using diagnostic ultrasound linear scanner. The highest number of dominant follicles are present during first two examinations, then their number declines and later in last two examinations rise again. Decrease in number of dominant follicles in both groups is most expressed in period of 14-30 days. During first examination, left ovaries have more dominant follicles, compared with right ovaries, while during later examinations, it is changed in favor of right ovaries. Increased number of vital dominant follicles from period 38-45 days postpartum and absence of abnormal uterine content in lumen in same period postpartum is sign of upcoming fertile estrus. Benjamin Čengić et al. 182

– Detection of subclinical mastitis in five different breeds of cows were done on the territory of a municipality Ključ, through all four year seasons by using the California mastitis test, at the level of the udder’s quarter with a certificate of bacteriological findings in order to justify their application in the diagnosis of mastitis. In total, 2150 cows of different breed composition: Simmental 1090, red Holstein 322, Holstein-Friesian 340, montafon 108 and various crossbreeds of 290 in total. After 1978 tested cows, 56.02% of cases had positive reactions to the California mastitis test. The most common positive reaction we found in the milk was in one or two quarters with the intensity of the reaction of one and two plus. The most common causes of mastitis were staphylococci, streptococci and mixed infections. Continuing use of these methods it is possible to timely detect the presence of subclinical mastitis and get satisfactory results in the prevention and treatment of mastitis as well as increasing the quantity and improving the quality of milk.

Success in cattle breeding is one of the most important goals in livestock farming and it requires particular attention when it is about securing unobstructed reproduction. Final goal in cattle breeding is to produce one live calf per year, which will likewise enhance milk production through successful pregnancy. The aim of our research was to monitor uterine involution speed with aid of ultrasound device and make records when cows are ready to be inseminated again, which cows need more time to complete involution and how many cows will have uterine disorders and require therapy. The experiment was carried out from October 2009 until the end of January 2010. In our experiment 50 cows were included and 412 transrectal ultrasound examinations were performed. Cows were transrectally examined, starting from 6th day postpartum until 52 days postpartum. Speed of uterine involution has been monitored through decrease of uterine horn diameter and wall thickness. Cows with normal puerperium have completed involution in the period from 38 - 45 days postpartum, while those with abnormal puerperium needed more time to complete it or required therapy of disturbed uterine status. In total 48% of cows had normal uterine involution, 52% of cows had some abnormalities in involution and 10% of cows in experiment required therapy. With continuous monitoring of reproductive tract in cattle with ultrasound it is possible to timely detect right time for first insemination postpartum, decrease period of open days or to detect abnormalities in uterine health status and treat it.