Effect of feeding yeast culture on ruminal fermentation and blood indicators of Holstein dairy cows

The experiment was conducted to evaluate the effect of yeast culture (Saccharomyces cerevisiae) supplementation on ruminal fermentation in 20 Holstein dairy cows divided into control and experimental groups, each group of 10 cows. The animals received a diet based on maize silage (19 kg), alfalfa silage (15 kg), meadow hay (1.5 kg), extracted rapeseed meal (1 kg) and concentrate mixture (9.5 kg). The diets were fed as a total mixed ration. The supplement of yeast culture Levucell® SC 20 (Saccharomyces cerevisiae – CNCM I-1077; min. content 2 × 1010 CFU·g-1) was added to the concentrate mixture in the ration fed to the experimental group of animals. The addition of yeast culture significantly (P < 0.01) increased ruminal pH but had no positive effects on the increased production of volatile fatty acids. The supplementation of yeast culture significantly (P < 0.01) increased numbers of protozoa in the rumen of dairy cows of the experimental group (361.3 ± 18.315) compared to the control group (308.3 ± 37.505). The addition of yeast culture significantly (P < 0.01) increased concentration of serum glucose, calcium, phosphorus, copper, zinc, magnesium and AST (P < 0.05). As compared to the control group (4.948 ± 0.0384 mmol·l-1), the level of urea in the blood serum was significantly decreased (P < 0.01) in the experimental group of cows. Our results show that the supplementation of Saccharomyces cerevisiae culture at recommended doses enhances ruminal fermentation which may have a positive effect on milk production and health status of Holstein dairy cows. Saccharomyces cerevisiae, cows, rumen fluid, blood serum indicators Yeasts and yeast cultures are frequently used as additives in diets of dairy cows at present. They have a positive influence on fermentation in the rumen, which helps to improve production health and productivity of animals. Results from previous studies on the effect of yeasts on ruminal fermentation and productivity of dairy cows are often ambiguous. The most cited benefit of yeast cultures on ruminal digestion is support of the growth and activity of anaerobic, namely cellulolytic bacteria. Yeasts would utilize residual oxygen introduced into the rumen with feeds, thus contributing to maintain anaerobic environment (Calsamiglia et al. 2006). Moreover, by degrading lyotropic carbohydrates in the rumen, yeast cultures regulate the rate of fermentation, and also by stimulation of lactate-utilizing bacteria yeasts facilitate stabilization of the rumen pH and mitigate its frequent oscillations during the day (Williams et al. 1991). Stable rumen environment is a key factor for achieving optimum milk yields and a good health of animals. However, some authors did not observe any beneficial effects of yeast cultures on dry matter intake or on the milk production and its composition in dairy cows (Cooke et al. 2007). Neither the positive influence of yeast on the digestibility of feeds in the rumen was unambiguously corroborated. Recent studies indicate that yeasts produce also certain low-molecular peptides that simulate the activity of some bacteria species in the rumen (Denev et al. 2007). However, to achieve a positive effect of yeasts on the production efficiency of dairy ACTA VET. BRNO 2011, 80: 139–145; doi:10.2754/avb201180020139 Address for correspondence: prof. MVDr. Ing. Petr Doležal, CSc. Mendel University Brno Zemědělská 1-3, 613 00 Brno, Czech Republic Phone +420 54513 3163 E-mail: [email protected] http://www.vfu.cz/acta-vet/actavet.htm cows, it is necessary to choose an adequate preparation because not all yeast strains can stimulate digestion in the rumen (Pinos-Rodríguez et al. 2008). The efficiency of yeast cultures depends among other factors also on the conditions of cultivation, on the concentration of live yeast cells (CFU) as well as on the dose of the culture used (Doležal et al. 2006). Strusinska et al. (2003) found a positive influence of added yeast cultures, mineral and vitamin supplements on selected biochemical indicators in the blood of dairy cows. Similarly, Nursoy and Baytok (2003) observed a beneficial influence of yeast culture on ruminal digestion, and production efficiency of cows, whereas the concentrations of analyzed blood metabolites were similar for cows that consumed diets. Nevertheless, none of the published studies demonstrated a negative effect of yeast culture on ruminal digestion or animal health. The aim of this study was to assess the effects of the yeast culture supplement in a total mixed ration (TMR) on some biochemical indicators of ruminal fermentation and selected blood indicators of highly producing dairy cows. Materials and Methods The experiment included 20 dairy cows of Holstein breed which were divided by ten into two equal groups with respect to productivity, number of lactations and live weight. The experimental period lasted 150 days. Cows were housed in a free-stall barn and fed 3 × daily the same TMR with the experimental group receiving addition of the yeast culture Levucell® SC 20 (Saccharomyces cerevisiae – CNCM I–1077) in diet at a dose of 1 g per animal and day. The yeast preparation contained 80% of live dried organisms of Saccharomyces cerevisiae) and 14% of devitalized cells with the minimal guaranteed concentration of 2 × 1010 CFU·g-1. The control group of cows did not receive any yeast supplement. The components, chemical composition and nutritional value of diets/feeding rations are presented in Table 1. Feed leftovers were removed before each feeding. Cows were milked in a milking parlour 2-times daily. Samples of rumen fluid were taken from the cows of both groups by oesophageal probe using a method described by Dvořák (1994) within 3 h after feeding, during the 4th month of the experiment. The rumen fluid was analyzed for the total content of volatile fatty acids (VFA), relative % ratio of acetic, propionic and butyric acids, pH value, abundance of infusorians and ammonia content. Volatile fatty acids were measured by the gas chromatography method and the ammonia content was ascertained by the AOAC method (1980). The total content of infusorians was established according to a method described by Dvořák (1994). Blood was sampled by tapping from vena caudalis mediana into single-use test tubes without addition of anticoagulants to obtain blood serum from which serum urea, asparate aminotransferase (AST) and lactate dehydrogenase (LDH) were subsequently established. The biochemical indicators were established on an automated analyzer Model Reflovet Plus by using standard procedures in the laboratory of the Mendel University Brno. For analysis of glucose in a blood the heparin and sodium chloride were added to the test tubes. The concentrations of macroelements calcium (Ca), phosphorus (P), magnesium (Mg) and trace elements – copper (Cu), zinc (Zn), manganese (Mn) and selenium (Se) were analyzed from the EDTA’s plasma in the laboratory of the Mendel University Brno. Results were statistically analyzed using the multi-factor analysis of variance (Snedecor and Cochran 1989) and by a subsequent verification based on Tukey Test. Results and Discussion Chemical composition and nutritional value of TMR are presented in Table 1. The concentration of crude fibre in 1 kg of dry matter was 16.80%, which corresponds to the physiological requirement and production efficiency of dairy cows. With higher fibre contents in feeding rations, or at the introduction of low-quality feeds, intestinal digestion is reduced, rumen motoric activity is slowed down. The soluble form of N constituted 27.13% of total N-substances. The degradability of crude protein in the rumen was lower (57.09%) and apparently connected with higher content of protected nitrogen. The advantage of TMR is a favourable proportion of degradable fibre (28.10%). The content of fat (4.99%) and the total content of starch (27.87%) are in line with the recommendations. Somewhat higher is the value of starch degradability (72.55%), which apparently results from the higher proportion of production mixture in the feeding ration (9.5 kg) and hence a higher amount of starch. Long-term feeding of this diet entails a possible risk of rumen 140