EFFECT OF VIABLE SACCHAROMYCES-CEREVISIAE ON THE RUMINAL FERMENTATION, ACID-BASE METABOLISM AND MILK-PRODUCTION OF DAIRY-COWS

In the recent years, the use of feed additives containing yeast cultur es has been increasing. These supplements have been tested under a var iety of feeding and management situation and improved milk production in dairy herds and a higher body-mass gain in beef cattle was reported in many cases. The aim of this study was to measure the influence of Live-Sacc (Saccharomyces cerevisiae - viable cells 5x10(9)/g - and a g rowth medium produced by Dr. Bata Ltd, Budapest, Hungary) on the rumin al fermentation, acid-base metabolism and also on the milk production of dairy cows. The experiment was conducted on a dairy farm with 1000 Holstein-Friesian head of cows. The age and milk production of the cow s in this unit was 3.8 years und 8000 kg/year, respectively, on an ave rage. 60 clinically healthy cows were randomly selected from the herd and were divided into two equal groups (experimental and control group s). Age and milk production of the cows were comparable during the pre vious lactation period. Prior to calving, the ration of the control gr oup consisted of maize silage, meadow-hay and mineral premix. After ca lving, the daily ration consisted of maize-silage, grass, alfalfa hayl age and hay. Stepwise increasing amount of concentrates (starting with 2 kg/cow/day, gradually increasing up to 11 kg/day) was also provided . The animals in the experimental group had the same ration except for that these cows received 20 g/day of Live-Sacc supplement starting fr om the second week prior to the expected parturition up to the 100th d ay of lactation. The ration met the demand of cows in both groups (NRC , updated in 1989). Ruminal fluid, blood and urine samples were collec ted in different periods of reproduction and production from randomly selected, healthy cows, 3 to 5 hours after the morning feeding. Determ ination of acetate, propionate and butyrate in the ruminal fluid, pH a nd net acid-base excretion in urine was performed. Daily milk producti on of cows was also recorded. The volatile fatty acid (VFA) content of ruminal fluid corresponded of the physiological status of animals in both groups two weeks before the expected calving (basal samples) and suggested an equilibrated protein supply. However, the acetate content of the ruminal fluid was about 14.3% higher in the experimental group 2-3 weeks after calving, in the period of increasing milk production as compared to; the control group. The difference was significant at t he p<0.05 level. The propionate and butyrate levels were comparable in both groups. The total VFA concentration levels were about 7.2% highe r in the experimental group than in the control one. The difference wa s highly significant (p < 0.001). Much lower lactate levels were found in the experimental group, the concentration was 47.05 % lower than t hat measured in the animals of the control group. A highly significant difference was found in respect of the acetate content of the ruminal fluid between the two groups in favour of the experimental group. In the period of peak of the lactation, the concentration of acetate, pro pionate and butyrate in the ruminal fluid of the experimental cows was superior to the values found in the control group. In the experimenta l group, the VFA content was higher by 12.5% indicating a more favoura ble, well balanced energy metabolism. The difference was highly signif icant (p<0.001). The acetate-propionate ratio measured in the experime ntal group was the nearest to the optimal 3 : 1 ration in all period t ested, indicating the beneficial effect of Live-Sacc on the ruminal fe rmentation. Well balanced energy metabolism was indicated by the resul ts of laboratory examinations of blood samples concerning the energy m etabolism two weeks prior to the expected parturition. The FFA level w as lower by 22.9% in the experimental group than in the control group in recently calved cows, indicating a better balanced energy metabolis m. The AST level was also lower by 7.3% in experimental animals than i n controls. At the peak of lactation, FFA value was lower by 52.9% in the experimental animals than in the controls, indicating a more favou rable energy metabolism. There were no significant differences between the mean acid-base values of blood samples of the two groups. pH and net acid-base excretion (NAPE) levels of urine samples indicated a sat isfactory metabolism in both groups in all periods on the experiment. NABE increased steadily in the experimental group after calving. This indicated that although a high ration of concentrates (11 kg/cow/day) was provided in this group, the acid loading expressively decreased du ring the period after calving. The increase of NAPE value was signific ant at a level of p<0.001. The daily milk production of the two groups was measured at every milking during 12 weeks of lactation and the da ta of milk yield were recorded in a computer. The daily milk productio n of cows in the experimental group was significantly higher during th e first 12 weeks of lactation (1.77 kg/day, on an average) than in the control group. The difference was highly significant (p<0.001). Summa rizing the results of the study, it could be pointed out that suppleme ntation of the diet with 200 g Live-Sacc/day/cow starting 2 weeks prio r to calving and continuing during the first 100 days of lactation fav ourably influenced the ruminal fermentation. Parameters of the ruminal fluid indicated a more balanced energy metabolism in the experimental group. After calving, in spite of the provision with a high amount of concentrates (11 kg/cow/day), the acid-load decreased. Thus, Live-Sac c favourably influenced also the acid-base metabolism. The more balanc ed energy and acid-base metabolism resulted in a significantly higher milk production (1.77 kg/cow/day).