Effect of different liquid cultures of live yeast strains on performance, ruminal fermentation and microbial protein synthesis in lambs.

Three yeast strains, Kluyveromyces marximanus NRRL-3234 (KM), Saccharomyces cerevisiae NCDC-42 (SC) and Saccharomyces uvarum ATCC-9080 (SU), and a mixed culture (1:1:1 ratio) were evaluated for their value as probiotics in lamb feeding in two experiment. In experiment I and II, 20 and 30 pre-weaner lambs were fed for 63 and 60 days in two and three equal groups respectively. All lambs were offered ad libitum a creep mixture and Zizyphus nummularia leaves, and yeasts were dosed orally. In experiment I, one group received no yeast, the other of the mixed culture (1.5-2 x 10(10) live cells/ml). In experiment II, yeast cultivation was modified yielding 1.5-2 x 10(13) live cells/ml. Lambs of the three experimental groups received 1 ml/kg live weight of one of the individual yeasts. Feed intake did not differ among groups of both experiments with the exception of SC-supplemented lambs in experiment II which showed a trend to higher intakes per kg metabolic body weight and in percentage of body weight when compared with KM- and SU-supplemented lambs. Supplementation of the mixed yeast culture had no effect on intakes of digestible crude protein and metabolisable energy, nutrient digestibility, nitrogen balance and rumen fermentation characteristics (pH, ammonia, volatile fatty acid concentration, protozoa count) and urinary allantoin as an indicator of microbial protein synthesis. The same was true for comparisons in experiment II except ciliate protozoa counts, which showed a trend to be the highest with SU and the lowest with SC. The results of present study show that the response of lambs to supplemented live yeast cultures is inconsistent, as it lacked to have an effect in the present study, and that differences among strains were small, even when supplemented at a much higher live cell count.