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.

The main goal of this paper was to investigate the influence of some additives included into high yielding dairy cows rations to overcome the problems in early lactation. These substances directly affect the productive performances of dairy cows as well as udder health. The commercial name of investigated preparation is 'YEASTURE' and it is composed of live yeast cultures selected from three strains Saccharomyces cerevisisiae in combination with probiotic bacteria and enzymes (Lactobacillus casei, Streptococcus faecium, Aspergillus oryzae, Lactobacillus acidophilus, 1,3-b and 1,6 D-Glucan, hemicellulase, Protease, Cellulase, Alpha amylase) which have the ability to modify the fermentation in rumen stimulating the development of ruminal bacteria and increasing the fibre digestion. Effects of this preparation have been investigated on 60 Holstein-Friesian cows divided into two groups. The diets were identical, and trial group received also 10 g of preparation Yeasture daily. Application of Yeasture started 15 days prior to calving and lasted until 60th day of lactation As a research result improved in vitro disappearance of diet dry matter from roughage (alfalfa hay, maize silage and ensiled sugar beet pulp) was established. Preparation Yeasture influenced quantity and composition of the milk. The difference between trial and control group was 2.57 kg 4%FCM or 8.70% (P<0.01) and 7.16% milk fat (P<0.05).Trial group supplemented with Yeasture showed lower somatic cells count by 7.3 percent points what indicated better health of cow's udder. Based on the presented results it can be concluded that inclusion of preparation Yeasture into diets for dairy cows in transition period can be recommended.

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.

Causes for cow culling in a tie stall system were investigated on a sample of 3060 cows culled in 2011, on seven large dairy farms in the Belgrade region. The total level of culling was 34.58% of the average number of cows. The number of cows culled decreased with lactation order (from 981 cows in the first to 294 cows in the sixth and later lactations). The most dominant cause for culling were diseases of the legs and hooves (28.4%), as was expected, having in mind the tie stall system. If selection (low production) is abstracted as the reason for culling, what stands out by importance are metabolic diseases (15.7%) and problems of reproduction (reproductive diseases-8.6%, and difficult calvings and abortions 5.7%). With the increase of duration of the lactation during which cows were culled, reproductive diseases gained importance as the reason for culling, while the importance of metabolic diseases and diseases of the legs and hooves in this context decreased. When culled, on the average, cows were 5.2 years old, having on the average spent 1112 days in production, of which 978 days in milking. Their average milk production per day of milking was 22.00 kg, per day of life 10.6 kg, and per day of production 19.8 kg.

Content: Results of production traits obtained from first calving cows and evaluation of the breeding value of bull sires of Simmental breed in Serbia. Data was analyzed using the method of least squares and for evaluation of bulls' breeding value mixed model of random sire effect (BLUP method). Based on obtained results it was established in statistical analysis that breeding region had highly significantly affected (P<0.01) the deviation of production traits from the general average. Considerable deviation from the general average was caused by the year and season of calving (P<0.05), and interaction of breeding region and calving season contributed to high variation in yield of milk and milk fat (P<0.01).

Life of modern people in urban conditions is characterized by lack of movement, which is main condition for maintenance of health, presence of large amount of additives and pesticide residua in food of plant and animal origin and polluted air and water. If the presence of oxidative stress is added as part of normal metabolism occurring during degradation of nutritive substances, when great quantity of free radicals is released, which organism in these conditions often is not capable of neutralizing, the homeostatic mechanisms are disturbed and this leads to health disturbances and even severe illnesses. In such complex living conditions, science is facing the challenge of finding out the way to prevent diseases and slow the aging process using food, primarily basic food stuffs - milk and meat, enriching them with certain substances which are of vital importance to our health. One of the ways is use of functional food which should contain not only its main nutritive value but also such ingredients which have impact on improvement of general health condition, i.e. they have preventive and therapy effect. In this paper, a review of the significance of omega-3 fatty acids in human nutrition is presented. As essential substances they cannot be synthesized in the organism, but have to be introduced through diet. Also, the significance of some essential omega-6 fatty acids as well as their mutual relation, are presented. The role of omega-3 fatty acids in animal nutrition is also pointed out in this paper, introduced or consumed by animals either by grazing or as diet supplement, which influence improvement of their production, reproduction and health performances.

**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).

In this paper are described the most important stressors in intensive sheep production on farms and pastures. Stressors on farms and pastures mostly originate from adverse housing conditions, improper zootechnical procedures, veterinary procedures (treatment, vaccinations, blood tests, surgery), animal husbandry procedures (labeling, weaning, grouping, shearing, shortening the tail, hoof care), unsuitable weather conditions (extreme heat and cold) and insufficient nutrition. The paper puts out special emphasis on the consideration of period of life in which sheep were subjected to additional loads and susceptible to effects of these stressors, such as birth, juvenile period, puberty, oestrus, advanced pregnancy, parturition and the puerperal period. [Projekat Ministarstva nauke Republike Srbije, br. TR 31086 i br. TR 31053]