The paper presents the results of a research on the impact of products based on natural zeolite on the production results of fattening lambs. The experiment involved two groups of lambs (the control-C and experimental-E groups), each consisting of 15 heads, for a period of 90 days. The meal was made from sheep milk, feed mixtures for fattening lambs and meadow hay. The test group lambs, unlike the ones from the control group, were given mixtures based on natural zeolite. Min-a-Zel S mixture (in the form of 25% composite) was fed to lambs from birth till their 14th day of life, directly into the mouth, once a day (before the morning feed), in the amount of 10 ml. Min-a-Zel Plus was given to them from their 15th day of life, together with the feed mixture (0.5%). Feeding was at will. The average weight of lambs at the end of the experiment, in accordance with the sequence of treatments (C:E) was 24.40:26.94 kg (P <0.01). Daily weight gain of lambs, during the experiment, was 229:256 g and in the experimental group it was by 27g or 11.79% higher (P <0.01). The test group lambs had a better utilization of dry matter, protein and energy, which justifies the use of products based on natural zeolite in fattening lambs.

Milk yield and milk chemical composition are largely affected by diet quality. Natural zeolite has been successfully used in livestock production as a feed supplement for some types and categories of domestic animals. This experiment was conducted over a period of 15 months involving Domestic Spotted dairy cattle. The test animals were assigned to three groups, each receiving different levels of supplemental zeolite. The control group comprised cows that received no zeolite supplement. Experimental groups I and II were fed compound feeds supplemented with 4% and 2% zeolite, respectively. The production traits studied included the following milk performance traits: whole lactation length, milk and fat yields over whole lactations, milk and fat yields over standard lactations. The results obtained suggest that zeolite supplementation affects some production traits, depending on the zeolite level present in livestock feed.

Šarplaninska (20.45 kg) genotype, while the highest average weight in first age group was found in Svrljiška (24.38 kg) and Sjeniĉka (23.76 kg) strain of Pramenka sheep. The variability in body weight of lambs at birth, as well at different stages of growth after weaning at early growth stages is influenced by direct maternal genotype, strains of Pramenka sheep and age of ewes.

On the basis of genetic variability of economically important traits we orientate ourselves toward specific methods development and use in genetic improvement of a population. However, the heritability (h2) is important for giving the answer, which traits can be included in the breeding value evaluation of a population. For determining the heritability 1502 black white breed cows were used: 751 mothers and 751 daughters (together 6393 lactations). The heritability coefficient of investigated traits in cows was calculated using three methods: regression of daughters to mothers, intraclass correlation according to bulls-sires and, for those features for which recurrence exists during the life we used method of repeatability (R). For average milk yield, milk fat and fat edited milk during standard lactations by the method of regression and repeatability intermediate coefficients of heredity were determined (from 0,291 to 0,323), while by the interclass correlation were determined high coefficients (from 0,461 to 0,543).The heritability coefficients for average content of milk fat were low (from 0,029 to 0,192), thus further improvement of this quantitative trait in the population would be possible mainly via bulls sires with the higher genetic potential. [Projekat Ministarstva nauke Republike Srbije, br. TR-31001

Estrus synchronization methods was use to control the reproductive traits of sheep, as well as bringing more females at the same stage of estrus and ovulation. According to the points mentioned above, the aim of the present study was to investigate and compare mating method and influence of fixed factors on birth and weaning weight of lambs. Statistical analysis showed that exist difference in the body weights between genotypes of lambs. In the first group, the difference in weight of lambs at birth, regardless of mating method was not significant (P> 0.05), while in the second group, the difference was slightly significant (P <0.05). As for the birth type, sex and within the same genotype, there was a statistical significance (P <0.05) between singles obtained naturally, between the triplets obtained naturally and between triplets received hormonal method. All the differences between body weight at 30 days (mating method, sex and birth type under the same genotype) were statistically significant (P <0.05).The determined differences in the body weights at 60 days (sex, mating method and type of birth under the same genotype) were statistically significant (P <0.05). The results showed that the differences (mating method, sex and type of birth under the same genotype) were statistically significant (P <0.05), except in between body weight at 90 days in twins among two genotypes obtained by natural method, which were not statistically significant (P> 0.05). [Projekat Ministarstva nauke Republike Srbije, br. TR31001 i br. TR31053]