The subject of this research was to determine the effect of the housing system on quality of welfare of dairy cattle in Serbia. Study was realized on six farms, capacity of 30 to 900 cows, with loose and tie housing system. Assessment of the welfare quality parameters was done by using the Welfare Quality ® Assessment Protocol for Cattle, 2009. Results of the research show that the welfare quality of dairy animals is under the significant effect of housing system, and that loose system has the advantage when it comes to comfort around resting, easy of movements and health condition of cows. Share of not lame cows (81%) and cows with no lesion (86%) was significantly higher (p<0.01) in loose system. Indicator values: duration of lying down movements (6.53 sec), lying down movements with collisions (18.7%) and lying outside lying area (28.4%) in tie system were significantly higher (p<0.01) compared to loose system indicating the inadequacy of the housing and lack of comfort. Analysis of indicators associated with cow hygiene (dirty legs and udder) and diseases (dystocia) points to significant gaps in management in both housing systems which represent significant threat to cow welfare quality.

Data concerning the effect of probiotics supplementation on many parameters concurrently at the same cows are lacking. Therefore, the objective of this experiment was to investigate the effects of Saccharomyces cerevisiae feeding on rumen, blood and milk parameters together in highproducing dairy cattle during the transition and early lactation period. Sixteen clinically healthy Holstein cows were divided into 2 groups: a control group of 6 cows and a probiotics-fed group of 10 cows. Rumen fluid and blood samples were collected 21 days before the expected calving as well as 7, 15, 30, 45 and 60 daysin- milk (DIM). Milk yield for each animal was recorded every 2 weeks. Individual milk samples were collected 15, 30, 45 and 60 DIM. Ruminal pH and rumen ammonia nitrogen were significantly lower, whereas total volatile fatty acids were significantly higher in yeast-fed animals compared with controls throughout the study. Serum concentrations of total proteins and globulins were higher, while albumins were lower in the yeast-treated group. Serum glucose levels were significantly higher in yeast-supplemented animals. Serum triglycerides, high density lipoproteins, and low density lipoproteins concentrations were lower, with cholesterol being significantly lower in the treated group. Milk production and milk fat percentage were higher, whereas milk protein percentage and somatic cell count were decreased in yeast-supplemented cows throughout the study. These results suggest that supplementation of S. cerevisiae to dairy cows rations during transition and early lactation period improve their health and milk production parameters.

This study covered 737 controlled first calving Simmental cows with, lactations concluded within one year. All first calving animals were on the farms of individual farmers in the municipalities of Kragujevac and Mladenovac. The research included the influence of bull sires, year and season of calving on milk yield and fertility. Least squares method was used to determine the average duration of lactation of 323.74 days. For a period of 305 days, heifers produced 3701.67 kg of milk, or 3644.58 kg of 4% FCM. The average production of milk fat was 144.26 kg and milk fat content was 3.88%. The interval from calving to first insemination lasted in average 124.19 days, and the animals were first calved at the age of 789.95 days. The bull sires had a highly significant effect (P<0.01) on the duration of lactation, milk yield and 4% FCM, milk fat yield and content and age of cows at first calving. The duration of service period was not under significant effect (P>0.05) of bull sires. Year of calving had a significant effect (P<0.01) on the duration of lactation, production of milk, milk fat and 4% FCM. Milk fat content, service period and age at first calving did not show significant variation due to the impact of different years of calving (P>0.05). Season of calving of cows demonstrated highly significant effect (P<0.01) on the production of milk and 4% FCM, and significant (P>0.05) on the production of milk fat, however it had no effect (P>0.05) on the milk fat content, duration of lactation and service period and age at calving.

This study was conducted in five dairy farms with different capacity (farms A with 47, B 12, C 10, D 14 and E 24 Simmental cows, aged between 4 and 5 years and body weight about 600 kg) in order to determine a relationship between rearing system, Animal Needs Index (ANI) and milk traits. Loose system of cow rearing was used in open stalls in farms A and C, while in other farms cows were tied in closed stalls. In two farms, there were outdoor pens, permanently available to cows on farm A, and during daytime on farm D. Rations for dairy cows were equal in all five farms and suitable for daily milk production about 20 kg with 4.0 % milk fat and 3.5 % milk protein. It was established that total ANI scores for farms were A 35.5, B 9.5, C 24.5, D 26.5 and E 10.5. The welfare levels in farms B and E were not sufficient, in farms C and D were very good, while in farm A it was excellent. A very significant influence of rearing system on cow welfare was found (p<0.001). A significant influence of rearing system (p<0.01) on average daily milk yield, milk yield in standard lactation, milk fat (kg), yield of 4 % fat corrected milk and yield of proteins (kg) were noticed. The influence of the rearing system on milk fat content (%), dry matter (%), protein (%) and lactose (%) was not statistically significant. Differences between ANI score, daily and standard lactation milk yield were very significant (p<0.001), as well as differences between ANI and the amount of milk fat (kg), protein (kg) and amount of 4 % fat corrected milk.

**Originalni nau ni rad-Original scientific paper Rad je finansiran od strane Ministarstva za nauku i zaštitu životne sredine, R. Srbije u okviru projekta TR-6858B Apstrakt: Ekonomi nost i uspeh u sto arskoj proizvodnji naj eš e zavise od više osobina. Iz tih razloga neophodno je vršiti takozvanu simultanu selekciju na nekoliko osobina. Fenotipska povezanost osobina u govedarstvu odnosi se na postojanje zajedni ke pozitivne ili negativne kovarijanse, koja nastaje kao rezultat delovanja genetskih i faktora spoljne sredine. Ovim istraživanjem je obuhva ena 3.461 kontrolisana prvotelka simentalske rase, sa laktacijama zaklju enim u toku jedne godine. Sve prvotelke su se nalazile na imanjima individualnih poljoprivrednih proizvo a a na podru ju Republike Srbije.U radu su ispitane fenotipske korelacije izme u slede ih osobina mle nosti i plodnosti: trajanje laktacije, prinos mleka, sadržaj mle ne masti, prinos mle ne masti, prinos 4% MKM, uzrast pri prvom telenju, trajanje servis perioda. Rezultati istraživanja fenotipskih korelacija dobijeni su koriš enjem mešovitih modela LSMLMW (Harvey, 1990). Ovaj metod omogu ava optimalno sagledavanje brojnih uticaja na ispitivane osobine (bikova-o eva, odgajiva kog podru ja, sezone telenja, godina telenja).