Aims:The aim was to isolate, identify and characterize yeasts present in rumen fluid and to select strains showing potential as probiotics. Methods and Results: Rumen fluid was sampled from 4 herds of dairy and beef cattle and 77 yeast isolates were identified. Initial screening was based on the capacity to maintain viability in a medium with different ruminal conditions. A second screening in fresh rumen fluid to assess the growth of inoculated yeasts and evaluate in vitro neutral detergent fibre digestibility (NDF-D), pH and acid accumulation was conducted. The yeast population ranged from 3Á84 to 6Á76 log 10 CFU per ml. The main species of yeast found were Pichia kudriavzevii, Candida rugosa, C. pararugosa, C. ethanolica and Magnusiomyces capitatus. Strains CCMA 933 (C. rugosa) and CCMA 970 (C. pararugosa) showed greater ability to survive in ruminal fluid and stimulated the production of acids. Isolate CCMA 967 (C. ethanolica) survived and improved the NDF-D. Conclusion: Pichia kudriavzevii was the dominant yeast found in the cattle herds. Strains CCMA 933, CCMA 970 and CCMA 967 showed properties that could be useful as potential probiotics for cattle. Significance and Impact of the Study: This study was the first to select yeasts from the rumen fluid, with the potential to be used as probiotic, based on the ruminal conditions. the contact of the cell wall with the intestinal lumen triggers an immune response (Dhama et al. 2015).Yeasts also appear to stimulate the growth and activity of fibrolytic ruminal bacteria by providing vitamins and growth factors (Moya et al. 2017). However, contradictory results are reported regarding interactions of diets, animals and environment (Chung et al. 2011). There are reports in the literature that the presence of some species Journal of Applied Microbiology 127, 845--855

The supplementation of dairy cows with yeast culture may increase diet digestibility, plasma niacin concentration, heat dissipation, and lactation performance. Our objective was to evaluate the response of Holstein cows in late lactation (234 ± 131 d in milk) to dead yeast culture (YC, 15 g/d, Factor SC, GRASP, Saccharomyces cerevisiae) during Brazilian summer (temperature-humidity index >68 for 92.2% of the time). Thirty-two cows were individually fed a standard total mixed ration for 14 d and control (CTL) or YC treatments for 35 d, in a covariate adjusted complete randomized block design. Response was evaluated in wk 5 or as repeated measures over time. Cows were milked 3 times per day and treatments (YC or placebo) were orally dosed to each cow before each milking. Plasma niacin was 1.50 for CTL and 1.66 µg/mL for YC. The YC reduced rectal temperature, respiration rate, and skin temperature, whereas it tended to increase sweating rate. The proportion of cows with rectal temperature ≥39.2°C on CTL and YC was, respectively, 8 and 0% at 0730 h, 52 and 25% at 1500 h, and 35 and 26% at 2200 h. Plasma glucose was increased by YC. The total-tract apparent digestibility of nutrients, plasma urea N concentration, molar proportion of ruminal VFA, and urinary allantoin excretion were not affected by YC. Cows fed YC were less selective against feed particles>19 mm in the morning, in the afternoon were more selective against long feed particles and in favor of particles <8 mm, and refused short particles at night. Milk yield was not different (30.5 kg/d for CTL and 30.2 kg/d for YC). Feeding YC reduced dry matter intake (20.3 vs. 19.4 kg/d) and the digestible organic matter intake (15.6 vs. 13.9 kg/d). The inclusion of YC increased the ratios of milk to dry matter intake (1.50 vs. 1.64) and energy-corrected milk to dry matter intake (1.81 vs. 1.98). The covariate adjusted body weight (648 kg) and body condition score (3.0) did not differ. Milk solids yields and concentrations, linear somatic cell count, and milk urea N were also similar. The supplementation of YC increased plasma niacin concentration, body heat loss, and feed efficiency of late lactation dairy cows by reducing intake at similar milk yield.

The objective of this study was to evaluate the effect of rehydrating and ensiling dry ground corn (DGC) with varying concentrations of wet brewers grain (WBG) on fermentation profile and ruminal in vitro starch digestibility (ivSD; 7-h incubations on dried and 4-mm ground samples). Samples of DGC and WBG were weighed separately and mixed into 100% WBG (WBG); mixture of DGC and WBG targeting 60 (RC60), 65 (RC65), or 70% (RC70) of dry matter (DM); and DGC rehydrated with distilled water targeting for 70% of DM (REH). Samples were ensiled in vacuum-sealed bags and allowed to ferment for 0, 1, 3, 7, 14, and 28 d. The experiment consisted of 30 treatments (5 mixtures of DGC and WGB × 6 ensiling time points) and 120 mini-silos (4 silos per treatment). All samples were analyzed for fermentation profile and water-soluble carbohydrates. Except for WBG, samples from 0 and 28 d were analyzed for ivSD. Content of DM was greater for REH (70.0%), followed by RC70 (69.2%), RC65 (63.9%), RC60 (58.4%), and WBG (17.5%) on d 0, with a slight decrease (1 to 2 percentage units) observed for all treatments until 28 d. Measurements of pH were highest for REH (6.19) and lowest for WBG (4.68) on 0 d, but all other treatments were lower than WBG on 14 and 28 d (3.83 vs. 4.14, on average). Except for WBG, all treatments had a gradual increase in lactic acid concentration from 0 to 28 d. In contrast, butyric acid gradually increased from 0 (0.25%) to 28 d (2.16% of DM) in WBG but not the other treatments. Fermentation patterns were related to water-soluble carbohydrates concentration, which was greater for all treatments except WBG from 0 (1.41% on average vs. 0.38% of DM, respectively) to 28 d (0.37% on average vs. 0.19% of DM, respectively). Except for RC60, greater ivSD was observed for all treatments on 28 than 0 d, but magnitude of the difference was greater for REH and RC70 (14.5 percentage units on average). Rehydration and ensiling of DGC with WBG resulted in adequate fermentation and enhanced starch digestibility.

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