The effect of feeding monensin, with or without dry hay plus wilted forage, on ruminal formation of 3-methylindole (3MI) was investigated in pastured cattle. Eighty-two cows were allotted to 3 groups. Cows of group-1 served as controls and were given a daily energy supplement (1 kg/head) without monensin for 1 day before and for 7 days after being allowed access to lush pasture. Cows of groups 2 and 3 were given the same daily energy supplement, which also contained monensin (200 mg/kg of supplement). Cows of group 3 also were fed dry hay for 5 days before the start of the study and continued to be given supplemental hay for 4 days after being allowed access to lush pasture containing a layer of wilted forage. Ruminal 3MI and indole concentrations increased on day 1 after all groups were allowed access to lush pasture. By day 7, 3MI concentration in all cows had decreased to pregrazing concentration. Indole concentration did not reach pregrazing concentration until day 10 for cows of groups 1 and 2. Group-3 cows had pregrazing indole concentration on day 7. Ruminal indole concentration did not differ (P > 0.05) between groups 1 and 2. Ruminal indole concentration was lower (P < 0.01) in group-3 cows on all sample collection days, except day 10, compared with that in the other groups. Monensin reduced (P < 0.01) 3MI formation on days 1 and 7 in group-2 cows, compared with group-1 cows. Group-3 cows had lower 3MI concentration than did group-1 cows (P < 0.01) on days -1, 1, 4, and 7. Monensin, when fed with dry hay and wilted forage, reduced (P < 0.01) 3MI formation on days 4 and 7 in group-3 cows, compared with cows that were only given monensin (group 2). Group-3 cows also had lower (P < 0.05) 3MI concentration, compared with group-2 cows on day 1. Results indicated that monensin reduced ruminal formation of 3MI. Feeding dry hay and wilted forage to cattle during the change to lush pasture resulted in further reduction in the amount of 3MI formed by ruminal microorganisms. To maximize the effectiveness of monensin in reducing 3MI formation, dry hay plus wilted forage should be fed to pastured cattle for at least 4 days after they are allowed access to lush pasture.

Investigation of stress reaction response and productivity of poultry by means of stimulation of natural resistance by biologically active substances was realized in the conditions of the Republic of Belarus by an example of 4 experimental group of broiler chickens of Kobb-500 cross. The first group was a control one. Chickens of the second group were administrated preparation Vigozin twofold in dose of 1 ml/l with water in course of the first three days in 2 cycles and with interval of 8 days. Chickens of the third group were given the preparation with water in dose of 1 ml/1 in course of the first 3 days. The fourth group was given the preparation with water in dose of 1 ml/1 in course of the first 5 days. In course of observation over chickens there was analyzed their clinical state, mortality rate, weight gain, and meat yield. In course of study in chickens of experimental group the daily average weight gain was 37,8 g against 34,1 in control; average live weight – 1099,6 +/- 7,57 g against 95,98 +/- 0,50 g in control. In 46-day old broiler chickens the average daily weight gain was 46,2 g against 43,1 g in control, average live weight – 2166,94 +/- 0,49 g against 2021,08 +/- 1,05 g in control. Forage expenses per 1 kg of weight gain were 2,01 kg against 2,18 kg in control. Forage conversion was 7,8%. Research results proved the efficiency of application of Vigozin preparation: viability of chickens in the second group on increased 3,5%; the third group - on 1,7% ; in the fourth group - on 2,5%

Investigation of influence of probiotic Dialact and immunostimulant Alveozan on digesting of nutritive substances by broiler chickens of Kobb-500 cross, as well as control over their individual development were realized in the conditions of the Republic of Belarus. The first (control) group of chicken was given standard well-balanced ration. Chickens of the second group were administrated immunostimulant Alveozan in dose of 10 mkg/kg of live weight with drinking water once a day in course of 5 days, with 10 days interval till the end of the growing period. Chickens of the third group were administrated preparation Dialact in dose of 0,1-0,2 ml with drinking water once a day in course of 3 days, with 14 days interval till the end of growing period. Chickens of the fourth group were given Alveozan in dose of 10 microgram/kg of live weight once a day in course of 5 days with 10 days interval, and Dialact in dose 0,1-0,2 ml once a day in course of 3 days, with 6 and 14 days interval. Research results showed that complex application of probiotic Dialact and immunostimulant Alveozan increased the viability of chickens on 100%, average live weight - on 5,1%, average daily weight gain - on 5,1%. Administration of Dialact and Alveozan, both separately and in complex, increased the digestibility of nutritive substances of mixed fodders: application of nitrogen increased on 1,93-6,38%, application of calcium decreased on 10,41-12,54%, phosphorus use increased on 2,38%