Daily rumen pH pattern of loose-housed dairy cattle as affected by feeding pattern and live yeast supplementation

Effects of Saccharomyces cerevisiae and Bacillus subtilis on in vitro fermentation in the rumen of Hu sheep

BACKGROUND

The demand for animal products is increasing in developing countries due to population growth. However, livestock production contributes significantly to global warming, accounting for 25%. Probiotics can help improve livestock efficiency by enhancing gut microbes and fat metabolism. They can modify rumen populations, enhance fermentation, reduce methane emissions and improve feed digestion. In this study, the goal was to determine the most effective method of reducing methane emissions in the rumen of sheep in vitro by adding different concentrations of Saccharomyces cerevisiae and Bacillus subtilis.

RESULTS

Adding 8 × 106 CFU g-1 S. cerevisiae during fermentation reduced pH levels after 48 h. This also increased the concentrations of NH3-N, microbial protein and total gas production. At the same time, it decreased methane emissions. Furthermore, adding 20 × 106 CFU g-1 B. subtilis to the mixture increased total gas production (TGP) and methane production, with the highest production observed after 48 h. However, it did not affect pH levels after 48 h.

CONCLUSION

It can be concluded that S. cerevisiae had significantly increased microbial protein and NH3-N concentrations after fermentation without altering pH. Additionally, the addition of S. cerevisiae enhanced TGP and reduced methane emissions. It is worth noting that TGP increased because B. subtilis was added at a concentration of 20 × 106 CFU g-1, with no significant differences between concentrations. Therefore, we recommend adding S. cerevisiae and B. subtilis to the diet at doses of 8 and 20 × 106 CFU g-1, as it resulted in higher TGP and reduced methane emissions. © 2024 Society of Chemical Industry.

Dietary fiber source and direct-fed microbial supplementation effects on lactation performance and feeding behavior of high-producing dairy cows

The objective of this study was to evaluate the effects of dietary fiber source and direct-fed microbial supplementation on lactation performance and feeding behavior of high-producing dairy cows. Sixty-four multiparous Holstein cows (3.5 ± 1.6 lactations; 76 ± 22 DIM and 735 ± 67 kg of BW at covariate period initiation) and 32 gate feeders were enrolled in a study with a completely randomized design and a 2 × 2 factorial arrangement. Cows and gate feeders were randomly assigned to treatments (16 cows and 8 gate feeds per treatment). Cows were allowed 1 week to acclimate to feeding gates followed by a 2-week covariate period. During the acclimation and covariate periods, all cows were fed the same diet to meet or exceed the nutrient requirements. Following the covariate period, cows were enrolled in a 8-week treatment period during which cows were randomly assigned to 1 of 4 treatments consisting of forage inclusion in the diet, either 45.8% (LF) or 56.7% (HF) of DM, and the supplementation of 75 mL/hd/d of a direct-fed microbial (DFM) containing herbal extracts (mallow, mint, and sage), L. plantarum, L. buchneri, Saccharomyces cerevisiae, and sugar cane molasses (Valibiom Mix, Valibiotics, Traiskirchen, Austria) or without supplementation (CON). The average covariate period value of each variable was used as a covariate. Three-way interactions were observed for DMI and feed efficiency. Dry matter intake was 2 to 3 kg greater for LF-DFM than HF-CON and HF-DFM during wk 2, 3, 5, and 8 of the treatment period. Milk production was 2.1 kg/d greater for LF than HF diets. Both milk fat and MUN concentrations were greater for HF than LF diets. Conversely, milk protein concentration was lower for HF than LF diets. The respiration rate measured in the morning was lower with DFM supplementation than CON. Rectal temperature measured in the morning and averaged for the day were greater for LF than HF diets. Under the conditions of the present study, feeding high-forage diets may be an alternative for producers to reduce feeding costs depending on the price of purchased feeds. However, non-forage fiber sources (i.e., soy hulls) must be considered when producers are challenged by either forage shortages or forage with a lower nutritive value. Additionally, DFM supplementation reduced respiration rate in the morning and affected meal behavior of lactating cows.

Effects of Live Saccharomyces cerevisiae Yeast Administration in Periparturient Dairy Cows

Dairy cows face several challenges during the transition period, and the administration of live yeast might be useful to mitigate this stressful condition. In the current study, the effects of live yeast administration on milk production, feed intake, and metabolic and inflammatory conditions were evaluated. Multiparous Holstein cows were enrolled in this randomized controlled trial and received either a control diet (CTR, n = 14) or the control diet plus 4 g/d of live Saccharomyces cerevisiae yeast (LSC, n = 14) from -21 to 56 days relative to calving. Dry matter intake, milk yield and composition, and rumination time were monitored daily. Blood samples were collected at -21, -7, 3, 14, 28, 42, and 56 days relative to calving to evaluate the metabolic profile. Fecal samples were collected at 56 days relative to calving to measure volatile fatty acids and feed digestibility. No differences between groups were observed in dry matter intake. Compared with CTR, rumination time was lower in LSC in after calving. Although there were no differences in milk components between groups, LSC had greater milk yield in the last three weeks of the study than CTR. No differences were observed in inflammatory markers or other plasma metabolites, except for β-hydroxybutyrate, which was higher in LSC, and reactive oxygen metabolites (ROMs), which were lower in LSC. Overall, these outcomes suggest that live yeast supplementation had some positive effects on milk yield and oxidative status.

Effects of Sophora alopecuroides in a High-Concentrate Diet on the Liver Immunity and Antioxidant Function of Lambs According to Transcriptome Analysis

The purpose of this study was to determine the effects of Sophora alopecuroides (SA) on liver function, liver inflammatory factor levels, antioxidant indexes and transcriptome in sheep. Twenty-four 3-month-old healthy Dumont hybrid lambs weighing 25.73 ± 2.17 kg were randomly divided into three groups: C1 (the control group), fed a concentrate-to-forage ratio of 50:50; H2 (the high-concentration group), fed a concentrate-to-forage ratio of 70:30; and S3 (the SA group), fed a concentrate-to-forage ratio of 70:30 + 0.1% SA. The results showed that the rumen pH values of the C1 and S3 groups were significant or significantly higher than that of the H2 group (p < 0.05 or p < 0.01). The serum ALT, AST and LDH activities and the LPS and LBP concentrations in the sheep serum and liver in the H2 group were significantly or extremely significantly higher than those in the C1 and S3 groups (p < 0.01), and the IL-10 content and SOD, GPX-PX and T-AOC activities showed the opposite trend (p < 0.05 or p < 0.01). KEGG enrichment analysis showed that the differentially expressed genes were significantly enriched in the ECM-receptor interaction and focal adhesion pathways, which are closely related to immune and antioxidant functions (p-adjust < 0.1). In summary, SA could improve the immune and antioxidant functions of lamb livers under high-concentrate conditions and regulate the mechanism of damage on sheep livers, which is caused by high-concentrate diets and through the expression of related genes in the ECM/FAs pathway.

Effects of adding Sophora alopecuroides to high concentrate diet on rumen fermentation parameters and microbial diversity of sheep

Objective

The purpose of this study was to investigate the effects of different doses of Sophora alopecuroides (SA) on the rumen fermentation and microbial diversity of sheep.

Methods

A total of 32 healthy Dumont crossbred male lambs weighing 25.73 ± 2.17 kg were randomly assigned to 4 treatment groups with 8 replicates each: a control group (CG) fed a basal diet with a concentrate-to-forage ratio of 7:3 and three experimental groups - the 0.1% group(TG1), 0.3% group (TG2), and 0.5% group (TG3), which were fed the same basal diet but supplemented with increasing doses of SA.

Results

(1) Increasing the SA dose led to a significant linear increase (p-< 0.05) in acetate, propionate, butyrate, and total volatile fatty acid (TVFA) concentrations in the rumen, as well as a significant quadratic effect (p-< 0.05) on the propionate concentration. In contrast, there was a significant linear decrease (p-< 0.05) in the NH3-N concentration in the rumen. (2) At the level of rumen bacterial phyla, the abundance of Bacteroidetes in the rumen increased, and that of Firmicutes decreased (p = 0.08). At the genus level, the rumen abundances of Ruminococcus and Phocaeicola of sheep in the three experimental groups were significantly higher than in the control group (p-< 0.05), and the abundances of Clostridiales and Candidatus-Hepatincola were significantly increased in the 0.1% and 0.3% groups (p < 0.05). (3) Regarding rumen anaerobic fungi, the differences between the control group and experimental groups at the phylum level and genus level were not significant (p > 0.05), but the relative abundances of Neocallimastigomycota and Piromyces in the 0.1% group were significantly higher than that in the control group.

Conclusion

SA addition to a high grain diet could increase the VFA concentration and pH in the sheep rumen, reduce the NH3-N concentration in the rumen and improve rumen fermentation function. Although there was no significant change in rumen bacterial or fungal diversity, SA addition increased the rumen abundances of Bacteroidetes, Ruminococcus, Phocaeicola, Clostridiales, Neocallimastigomycota and Piromyces, decreased the rumen abundance of Firmicutes, and had a positive effect on the rumen microbiota to improve sheep health.

Effect of supplementing live Saccharomyces cerevisiae yeast on performance, rumen function, and metabolism during the transition period in Holstein dairy cows

Dairy cows have to face several nutritional challenges during the transition period, and live yeast supplementation appears to be beneficial in modulating rumen activity. In this study, we evaluated the effects of live yeast supplementation on rumen function, milk production, and metabolic and inflammatory conditions. Ten Holstein multiparous cows received either live Saccharomyces cerevisiae (strain Sc47; SCY) supplementation from -21 to 21 d from calving (DFC) or a control diet without yeast supplementation. Feed intake, milk yield, and rumination time were monitored until 35 DFC, and rumen fluid, feces, milk, and blood samples were collected at different time points. Compared with the control diet, SCY had increased dry matter intake (16.7 vs. 19.1 ± 0.8 kg/d in wk 2 and 3) and rumination time postpartum (449 vs. 504 ± 19.9 min/d in wk 5). Milk yield tended to be greater in SCY (40.1 vs. 45.2 ± 1.7 kg/d in wk 5), protein content tended to be higher, and somatic cell count was lower. In rumen fluid, acetate molar proportion was higher and that of propionate lower at 21 DFC, resulting in increased acetate:propionate and (acetate + butyrate):propionate ratios. Cows in the SCY group had lower fecal dry matter but higher acetate and lower propionate proportions on total volatile fatty acids at 3 DFC. Plasma analysis revealed a lower degree of inflammation after calving in SCY (i.e., lower haptoglobin concentration at 1 and 3 DFC) and a likely better liver function, as suggested by the lower γ-glutamyl transferase, even though paraoxonase was lower at 28 DFC. Plasma IL-1β concentration tended to be higher in SCY, as well as Mg and P. Overall, SCY supplementation improved rumen and hindgut fermentation profiles, also resulting in higher dry matter intake and rumination time postpartum. Moreover, the postcalving inflammatory response was milder and liver function appeared to be better. Altogether, these effects also led to greater milk yield and reduced the risk of metabolic diseases.

Effect of Saccharomyces cerevisiae supplementation during the suckling period on performance of Awassi ewes

This study aimed to investigate the impact of supplementing two levels of Saccharomyces cerevisiae (SC) during suckling period on performance and serum metabolites of Awassi ewes. The study comprised two experimental periods, for experimental period 1, 30 nursing Awassi ewes with their single lambs were randomly assigned to one of three equal treatment groups: a control diet (CON; n=10), low SC (LSC) diet (0.4 g SC/head/day; n=10), and high SC (HSC) diet (0.8 g SC/head/day; n=10) with 9-week experimental periods including 1 week for dietary and pen adaptation and 8 weeks for data and sample collection. For experimental period 2, 4 ewes from each group were randomly selected and were individually housed in metabolism crates with 7-day experimental periods including 3 days for crate adaptation and 4 days for data and sample collection. The results showed that the supplementation of SC improved dry matter (DM) intake of ewes (P = 0.03). Digestibility of DM was higher (P < 0.05) for SC treatment groups. The SC treatment groups had a tendency improvement in digestibility of crude protein, neutral detergent fiber, and acid detergent fiber. Addition of SC improved (P < 0.05) N balance parameters of ewes. A significant increase was observed for the rumen fluid pH of lactating ewe supplemented with SC. No difference was detected in the live weight change of lactating ewes in all treatment groups. The final body weight of the lambs tended to be greater for SC treatment groups vs CON group but average daily gain and total weight gain were significantly higher (P = 0.05) for SC treatment groups. Lactating ewes in the SC treatment groups produced more milk per day (P ≤ 0.05) than those in the CON diet. Milk fat % and yield in the SC treatment groups were also greater (P = 0.05). No differences were found in % of milk protein, lactose, and solid-not-fat (SNF) between all groups (P > 0.05) while lactose and SNF yields were greater (P < 0.05) for SC treatment groups. However, % of the total solids (TS) of milk was higher for HSC diet compared to LSC and CON diets (P < 0.05) while TS yields were significantly higher for SC treatment groups. Energy-corrected milk values were greater (P < 0.05) in HSC diet compared to LSC and CON diets. With the exception of aspartate aminotransferase and alkaline phosphatase, no differences were detected in all other serum metabolite concentrations of lactating ewes in between treatment groups. In conclusion, this study indicates that SC supplementation with varying levels in the diet had a similar positive effect on some performance and physiological parameters of lactating Awassi ewes and their lambs.

Yeast-fermented cassava as a protein source in cattle feed: systematic review and meta-analysis

The present study evaluated the effect of the inclusion of cassava fermented with Saccharomyces cerevisiae yeasts on performance, feed intake, nutrient digestibility, rumen microorganisms and ruminal fermentation of cattle through a systematic review and meta-analysis. The effects of yeast-fermented cassava (YFC) in the diet of cattle were evaluated using the mean difference as a measure of the effect size, considering a confidence interval of 95%. Subgroup and meta-regression analysis were performed to investigate the origin of heterogeneity. The database included eight experiments. Three studies were related to dairy heifers, three related to dairy cow and the remaining two studies were associated to beef heifers. The inclusion of YFC in the bovine diet increased the dry matter intake %BW (P < 0.01) and nutrient digestibility (P < 0.05). We observed an increase in mean ruminal pH (P < 0.01), volatile fatty acid (P < 0.01) and propionic acid concentration (P < 0.01). There was a significant increase in the population of bacteria (P < 0.01) and fungi (P < 0.01), and a reduction in the protozoan count in the rumen fluid (P < 0.01) in the animals fed with YFC. Lactating cows fed YFC produced 1.02 kg/day more (P < 0.01) milk than non-supplemented cows. In addition, there was an increase of 7.4% in the fat (P = 0.03), 6.3% in the protein (P < 0.01) and 2.8% in lactose (P = 0.02) of milk of cows supplemented with YFC. The results of the present meta-analysis showed that the total or partial inclusion of YFC in cattle concentrate improves fermentation and rumen efficiency, dry matter intake, nutrient digestibility, milk yield, and milk composition.

Active dry yeast supplementation benefits ruminal fermentation, bacterial community, blood immunoglobulins, and growth performance in young dairy goats, but not for intermittent supplementation

This study evaluated the effects of active dry yeast (ADY) supplementation and supplementation strategies on ruminal fermentation, bacterial community, blood metabolites, and growth performance in young dairy goats. Sixty young female Guanzhong dairy goats of similar age (4.00 ± 0.50 months) and BW (19.65 ± 0.41 kg) were randomly divided into 3 groups (n = 20): (1) basal diet group (CON); (2) basal diet continuously supplemented with 3.0 g/goat per day commercial ADY (a proprietary strain of Saccharomyces cerevisiae with 5.0 × 10⁹ cfu/g) group (CSY); (3) basal diet with intermittently supplemented ADY group (ISY; 5 d supplementation with ADY at 4.5 g/goat per day following 5 d of no supplementation). The experiment lasted 67 d with the first 7 d as an adaptive period. Rumen fluid and blood samples were collected bi-weekly. Data were analyzed using the MIXED procedure combined with the SLICE option in SAS. Specific orthogonal contrasts of ADY vs. CON and CSY vs. ISY were also analyzed. During the experimental period, ADY supplementation resulted in greater DMI (P = 0.03), ruminal acetate proportion (P < 0.01) and acetylesterase activity (P = 0.01), and blood contents of glucose (P = 0.01) and IgM (P = 0.02) and tended to have greater ADG (P = 0.05) and paunch girth (P = 0.06) than the CON, despite the propionate proportion (P = 0.03) and contents of total protein (P = 0.04) and IgA (P = 0.03) being lower. The lower ruminal NH₃-N (P < 0.01) and blood urea nitrogen (P = 0.07) contents indicated greater nitrogen utilization with ADY supplementation. ADY supplementation showed persistent effects after it was stopped because the BW at 12 months of age (P = 0.03) and birth weight of lambs (P = 0.02) were greater than the CON. However, the ISY did not show those benefits and had significantly lower relative abundances of fiber-degrading related bacteria than the CSY. In conclusion, ADY supplementation, especially continuously supplemented, may enhance ADG and ADG:DMI ratio by improving DMI, ruminal cellulolytic bacteria abundance and enzyme activity, nitrogen utilization, and immune status. These findings provide a theoretical basis for the rational application of ADY and have important practical implications for the design of nutritional strategies in growing dairy goats.

The Mixture of Saccharomyces cerevisiae and Clostridium butyricum Could Promote Rumen Fermentation and Improve the Growth Performance of Goats in Hot Summer

This study aimed to investigate the effects of multiple mixing ratio pairs of Saccharomyces cerevisiae (SC) and Clostridium butyricum (CB) on rumen fermentation and growth performance of goats in hot summer. Thirty goats were divided into five groups: 0.00% probiotics (control), 0.30% SC and 0.05% CB (P1), 0.30% SC and 0.10% CB (P2), 0.60% SC and 0.05% CB (P3), and 0.60% SC and 0.10% CB (P4) of the dry matter (DM) weight of the basal diet and were assigned to a 5 × 5 Latin square experimental design. The results showed the pH values, the activities of ruminal cellulolytic enzymes, and the concentrations of ammonia nitrogen, acetic acid, propionic acid, total volatile fatty acids, vitamins B1 and B2, and niacin were significantly increased (p < 0.05) by probiotics. Moreover, the DM intake, average daily gain, the digestibilities of DM, neutral detergent fiber, and acid detergent fiber were significantly increased (p < 0.05) in probiotic-supplemented groups. Additionally, among all probiotic supplementation groups, the P3 group had the most beneficial effect on rumen fermentation parameters and the growth performance of goats. These results suggested that the mixture of 0.60% Saccharomyces cerevisiae and 0.05% Clostridium butyricum of the DM concentration was beneficial to improve rumen fermentation and promote the growth of goats in hot summer.

Effects of a novel direct-fed microbial on growth performance, carcass characteristics, nutrient digestibility, and ruminal morphology of beef feedlot steers

The effects of a novel direct-fed microbial (DFM) on feedlot performance, carcass characteristics, digestibility, ruminal morphology, and volatile fatty acid (VFA) profile of finishing steers were evaluated. Single-source Angus-crossbred yearling steers (n = 144; initial body weight (BW) = 371 ± 19 kg) were used in a randomized complete block design. Steers were blocked by initial BW and randomly assigned to treatments (12 pens/treatment; 4 steers/pen). Treatments included (A) CONTROL (no DFM, tylosin, or monensin, (B) MONTY (monensin sodium [330 mg/animal-daily] and tylosin phosphate [90 mg/animal-daily]), and (C) MONPRO (monensin sodium [same as previous] and Lactobacillus salivarius L28 [1 × 106 CFU/animal-daily]). Treatments were included in a steam-flaked corn-based finisher diet offered once daily using a clean-bunk management for ~149 d. The digestibility assessment was performed from days 70 to 74. Ruminal fluid and rumen tissue samples were collected at the slaughter for VFA profile and papillae morphology analyses, respectively. Data were analyzed using the GLIMMIX procedure of SAS with pen serving as the experimental unit, treatment as fixed effect, and BW block as random effect. Steers offered MONPRO had on average 5.3% less (P < 0.01) dry matter intake (9.56 kg/d) compared with either CONTROL (10.16 kg/d) or MONTY (9.96 kg/d). The carcass-adjusted final BW (613 kg; P = 0.23), overall average daily gain (1.64 kg/d; P = 0.23), and gain-efficiency (0.165; P = 0.61) were not affected by treatments. Steers offered CONTROL had greater (P < 0.01) marbling score and tended (P = 0.06) to have less carcasses grading Select and tended (P = 0.10) to have more carcasses grading Upper-Choice, while other carcass characteristics and liver-abscesses were not affected (P ≥ 0.23) by treatments. The digestibility of nutrients (P ≥ 0.13) and the ruminal VFA profile (P ≥ 0.12) were not affected by treatments. Steers offered MONPRO tended (P = 0.09) to have 16% greater average papillae number compared to other treatments. Yearlings offered finishing diets containing L. salivarius L28 plus monensin did not affect growth performance, digestibility, or ruminal VFA, but reduced feed intake. Carcass quality was negatively affected by treatments, while animals consuming L. salivarius L28 and monensin tended to improve ruminal morphology. Current findings in ruminal morphology and feed intake may warrant further assessment of diets containing L. salivarius L28 on beef cattle food safety aspects.

Effectiveness of Probiotic and Combinations of Probiotic with Prebiotics and Probiotic with Rumenotorics in Experimentally Induced Ruminal Acidosis Sheep

Background

Acidosis is one of the most common rumen diseases characterized by changes in the rumen environment and the circulatory system. Recent alternative trends in rearing small ruminants have led to the use of probiotics, rumenotorics and prebiotics to treat acidosis in animals.

Purpose

This study aimed to evaluate the efficacy of probiotics and the combination of probiotics with prebiotics and probiotics with rumenotorics for the treatment of acidosis in sheep.

Methods

This experimental study was conducted from September 2018 to May 2019. For the therapeutic study, 25 sheep were randomly divided into 5 equal groups. Acidosis was induced by an oral dose of 50 g/kg with wheat flour after a 24 hour fast. Four regimens of therapy were employed: PT probiotics, PPT probiotics with prebiotics; PRT probiotics with rumenotorics and standard ST treatment were adopted. Before and after therapy, laboratory analyses on rumen fluid, serum analysis, physical signs, and hematological changes were conducted.

Results

When probiotics were combined with rumenotorics (PRT), the mean standard deviation of rumen pH at day zero was 4.96±0.837 (PRT). Rumen pH improved from day one today three to 5.92±0.54, 6.30±041 and 6.75±0.34, respectively. The change in rumen pH was statistically significant after treatment on day 3 (p=0.002). The therapeutic regimens of PRT had improved heart rate and respiratory rate after treatment and the change was statistically significant (p=0.006 and p=0.000) compared to the control group. The PCV of the PRT treated sheep was also improved.

Conclusion

Probiotics with rumenotorics were the most successful therapeutic regimen for the treatment of ruminal acidosis in sheep. Therefore, the use of probiotics with rumenotorics is the promising alternative for the treatment of acidosis.

The effects of a nutritional packet (live yeast, vitamins C and B1, and electrolytes) offered to steers in a calf-fed system on growth performance, nutrient digestion, feeding behavior, carcass characteristics, and ruminal variables

Effects of a nutritional packet strategically offered to calf-fed system steers on growth performance, nutrient digestibility, feeding behavior, ruminal variables, and carcass characteristics were evaluated. Angus crossbred steer-calves (N = 60; body weight [BW] = 234 ± 4 kg) were used in a randomized complete block design (block = BW) and stratified into two treatments: 1) control; and 2) 30 g/steer-daily (dry matter [DM] basis) of a nutritional packet containing (steer-daily basis): Live yeast (Saccharomyces cerevisiae; 1.7 × 10¹⁰ CFU), vitamin C (Ascorbic acid, 162 mg), vitamin B1 (thiamin hydrochloride, 400 mg), sodium chloride (2.4 g), and potassium chloride (2.4 g). Animals were offered (electronic feed-bunks [SmartFeed, C-Lock Inc., Rapid City, SD]), a steam-flaked corn-based finishing diet to ad libitum (individual intake), once daily for 233 d. Treatments were offered during the first and last 60 days on feed (DOF). The GLIMMIX procedure of SAS was used, with steer as the experimental unit, treatment and phase (for feeding behavior and digestibility) as fixed effects, and BW-block as a random effect. Steers offered the nutritional packet had 14% less (P < 0.01) intake and 18% greater (P = 0.01) feed efficiency during the initial 30 DOF. Intake (days 0 to 233) was 6% greater (P = 0.02) for steers offered the nutritional packet, while BW gain was not different (P ≥ 0.44). Greater (P = 0.02) dressing percent (61.1% vs. 62%) for steers offered the packet was observed, while other carcass variables were not different (P ≥ 0.33). Digestibility of DM, organic matter, and fiber were greater (P < 0.01) for steers offered the packet. Steers offered the packet spent 13% less time eating during the first 60 DOF, while during the last 60 DOF a 14% greater meal frequency and 12.3% smaller mean meal size (treatment × phase interaction, P < 0.02) were observed. Steers offered the packet had a reduced (P ≤ 0.01) mean meal duration during both phases. Regardless of treatment, a decreased rumination (P ≤ 0.03) and chewing (P ≤ 0.01) activities were observed for the last 60 DOF compared to the first 60 DOF. Ruminal papillae area was 30% greater (P = 0.02) and the total volatile fatty acid (VFA) tended (P = 0.09) to be greater for steers offered the nutritional packet. The nutritional packet offered to calf-fed steers improved feed efficiency during the initial 30 d after arrival, while inducing superior overall intake, nutrient digestibility, dressing percentage, ruminal papillae area, and total ruminal VFA.

Defatted silkworm pupae meal as an alternative protein source for cattle

Silkworm pupae meal (SWP) is a protein-rich by-product of the silk reeling industry, available in a significant quantity. However, there has been little and insignificant research into the use of SWP in ruminants to date. In this view, the present study was conducted in two phases to evaluate the effect of different inclusion levels of defatted silkworm pupae meal (DSWP) on rumen fermentation, microbial protein synthesis and nutrient utilisation in cattle fed on finger millet straw (FMS)-based diet. Four isonitrogenous concentrate mixtures (CM) were prepared with DSWP replacing soybean meal (SBM) protein at 0 (T0), 10 (T1), 20 (T2) and 30% (T3). In phase I, a rumen fermentation experiment was conducted in a 4 × 4 Latin square design using four crossbred steers to study the effect of different levels of DSWP on rumen fermentation. No significant difference (P > 0.05) was observed in rumen fermentation parameters such as pH, ammonia nitrogen (NH₃-N) and total volatile fatty acids (VFA) among the experimental groups. In phase II, the digestibility trial was conducted in 20 crossbred cattle (311.2 ± 4.81 kg), which were divided into four experimental groups of five animals each in a completely randomised design to study the effect of different rations (T0, T1, T2, T3) on microbial protein synthesis and nutrient utilisation. The intake and digestibility of nutrients, excretion of urinary purine derivatives and microbial protein synthesis were not significantly different among the experimental groups. In addition, feeding DSWP revealed no significant (P > 0.05) change in the blood biochemical parameters of animals. Furthermore, at the same price as SBM, DSWP provides two units more crude protein. Therefore, the results of the present study indicated that DSWP can be incorporated into the ration of cattle up to 30% by replacing SBM without affecting rumen fermentation pattern and nutrient utilisation.

The Low Dose of Saccharomyces cerevisiae Is Beneficial for Rumen Fermentation (Both In Vivo and In Vitro) and the Growth Performance of Heat-Stressed Goats

This study aimed to investigate the effects of Saccharomyces cerevisiae on rumen fermentation and the growth performance of heat-stressed goats. The fermentation experiment was conducted using Saccharomyces cerevisiae added at 0‰ (HS1), 0.30‰ (SC1), 0.60‰ (SC2), and 1.20‰ (SC3) of the dry matter (DM) weight of the basal diet. The results showed that supplementing with 0.60‰ (SC2) could increase the pH, acetic acid to propionic acid ratio, the concentrations of ammonia nitrogen, total volatile fatty acids, acetic acid, propionic acid, butyric acid, and the degradability of DM, neutral detergent fiber, and acid detergent fiber in rumen fluids of heat-stressed goats. In the feeding experiment, twelve heat-stressed goats were assigned to a 4 × 4 Latin square experimental design, and the Saccharomyces cerevisiae supplement levels are similar to the fermentation experiment above. Similar effects on rumen fermentation and digestibility parameters were obtained with a supplement with 0.60‰ of Saccharomyces cerevisiae (SC2A) compared to the fermentation trial. Moreover, in the SC2A group, the DM intake and average daily gain also increased significantly compared with other groups. These results suggested that a low dose of Saccharomyces cerevisiae can still effectively improve the rumen fermentation and growth performance of heat-stressed goats.

Prophylactic Feeding of Clostridium butyricum and Saccharomyces cerevisiae Were Advantageous in Resisting the Adverse Effects of Heat Stress on Rumen Fermentation and Growth Performance in Goats

This study aimed to investigate the effect of the prophylactic feeding of Clostridium butyricum (CB), Saccharomyces cerevisiae (SC), and their mixture before the onset of heat stress on the rumen fermentation and growth performance of goats, and subsequently, on heat stress status. Forty-eight male Macheng Black × Boer crossed goats (22.25 ± 4.26 kg) were divided into four groups—the control group (fed the basal diet), and the CB (0.05% CB added to the basal diet), SC (0.60% SC added to the basal diet), and Mix (0.05% CB and 0.60% SC added to the basal diet) groups—and fed for fourteen days. Then, these goats were kept in a heat stress environment (with a temperature−humidity index of 87.04) for fourteen days. Then, the parameters of rumen fermentation and growth performance were measured. The results showed that the pH values, the activities of cellulolytic enzymes (avicelase, CMCaes, cellobiase, and xylanase), and the concentrations of ammonia-N, total volatile fatty acid, acetic acid, propionic acid, and butyric acid were significantly increased (p < 0.05) in the rumens of the CB, SC, and Mix groups compared to those of the control group. Moreover, the average daily gain and the digestibility of dry matter, neutral detergent fiber, and acid detergent fiber were significantly increased (p < 0.05) in the CB, SC, and Mix groups compared to those of the control group. These results suggest that these two probiotics and their mixture effectively alleviate the adverse effects of heat stress on rumen fermentation and growth performance via prophylactic feeding.

Influence of feeding Saccharomyces cerevisiae on the heat load responses of lactating dairy cows during summer

The objective of this study was to evaluate the influence of supplementing lactating dairy cows with Saccharomyces cerevisiae on milk production and composition, cow behavior, and physiological responses during summer. Twenty primiparous cows were used and two treatments were imposed: (1) control (CON); and (2) probiotic supplementation (PRO; S. cerevisiae, providing 10¹⁰ colony forming units (CFU) per day). Rumen temperature (T_RUM, °C) and pH were obtained via rumen boluses. Rumen temperatures were obtained from all cows (n = 20) at 10-min intervals and ruminal pH were obtained from five cow pairs (n = 10) at 10-min intervals. Ambient temperature (T_A; °C), relative humidity (RH; %), wind speed (WS; m/s), and solar radiation (SR; W/m²) were recorded at 10-min intervals. The temperature humidity index (THI) was calculated using T_A and RH. Cows were milked twice daily. Milk fat (%), protein (%), lactose (%), and somatic cell count (SCC, '000) were evaluated on 16 occasions. Cows were observed three times (0800 h; 1200 h; and 1400 h) daily for panting score (PS); respiration rate (RR); posture (standing/lying); shade utilization; and cow activity (eating/drinking/ruminating). Individual PS were used to calculate a mean panting score (MPS) for CON and PRO treatments for each observation. S. cerevisiae did not influence milk yield (P = 0.87), fat (P = 0.82), protein (P = 0.26) or SCC (P = 0.19), although there was a tendency for PRO cows to have higher lactose (P = 0.06). Probiotics did not influence the proportion of cows utilizing shade (P = 0.42); standing (P = 0.41); ruminating (P = 0.72); or drinking (P = 0.40). All cows exhibited an increase in RR (> 24 bpm) at 1200 h and RR showed a steady increase as THI increased (P < 0.0001), regardless of treatment (P = 0.96). Both CON (35.8%) and PRO (40.2%) exhibited an increase in MPS as THI increased from thermoneutral (THI ≤ 74) to very hot (THI ≥ 84.1; P < 0.001). However, PRO cows had lower (2.19 ± 0.09; P < 0.0001) MPS compared with CON (2.54 ± 0.22) cows when THI was categorized as very hot (THI ≥ 84.1). Rumen pH were not influenced by treatment (P = 0.38), however T_RUM of PRO cows were 0.2 °C lower across days (P < 0.0001) and hours (P < 0.0001). These results suggest that supplementing cows with S. cerevisiae may support thermoregulation via decreased T_RUM and MPS; however, further studies are required.

Effects of a blend of live yeast and organic minerals or monensin on performance of dairy cows during the hot season

The objective of this study was to evaluate the effects of feed additives on intake and digestibility of nutrients, milk yield and composition, feeding behavior, and physiological parameters of dairy cows during the hot season. Forty Holstein cows were assigned to a randomized block design experiment with a 2 × 2 factorial treatment arrangement to evaluate (1) control diet without inclusion of additives; (2) monensin (MON), 20 mg/kg diet dry matter sodium monensin (Rumensin; Elanco); (3) Milk Sacc+ (MS+), inclusion of 40 g/cow per d of Milk Sacc+ (a blend of live yeast and organic minerals, Alltech); and (4) combination of MON and MS+. The average temperature-humidity index throughout the experimental period was 73 ± 2.84 (standard deviation). The experiment lasted 11 wk, including 2 preliminary weeks for covariate adjustments. Cows fed MS+ increased dry matter intake (% body weight), milk yield, 3.5% fat-corrected milk, and solids yield, and cows fed MON had greater milk urea nitrogen content in comparison with counterparts. Feeding MS+ increased the intake of feed particles with size between 8 and 19 mm and decreased the intake of particles shorter than 4 mm compared with other treatments. Rumination time (min/d) and chewing time (min/kg of neutral detergent fiber) were lower for cows fed MS+. Physiologic parameters (i.e., heart and respiratory rates, and body temperature) were not affected by the treatments. Overall, the use of monensin did not differ from control, and Milk Sacc+ improved performance of cows.

Effects of yeast culture supplementation on lactation performance and rumen fermentation profile and microbial abundance in mid-lactation Holstein dairy cows

The continuous trend for a narrowing margin between feed cost and milk prices across dairy farms in the United States highlights the need to improve and maintain feed efficiency. Yeast culture products are alternative supplements that have been evaluated in terms of milk performance and feed efficiency; however, less is known about their potential effects on altering rumen microbial populations and consequently rumen fermentation. Therefore, the objective of this study was to evaluate the effect of yeast culture supplementation on lactation performance, rumen fermentation profile, and abundance of major species of ruminal bacteria in lactating dairy cows. Forty mid-lactation Holstein dairy cows (121 ± 43 days in milk; mean ± standard deviation; 32 multiparous and 8 primiparous) were used in a randomized complete block design with a 7-d adaptation period followed by a 60-d treatment period. Cows were blocked by parity, days in milk, and previous lactation milk yield and assigned to a basal total mixed ration (TMR; 1.6 Mcal/kg of dry matter, 14.6% crude protein, 21.5% starch, and 38.4% neutral detergent fiber) plus 114 g/d of ground corn (CON; n = 20) or basal TMR plus 100 g/d of ground corn and 14 g/d of yeast culture (YC; n = 20; Culture Classic HD, Cellerate Yeast Solutions, Phibro Animal Health Corp.). Treatments were top-dressed over the TMR once a day. Cows were individually fed 1 × /d throughout the trial. Blood and rumen fluid samples were collected in a subset of cows (n = 10/treatment) at 0, 30, and 60 d of the treatment period. Rumen fluid sampled via esophageal tubing was analyzed for ammonia-N, volatile fatty acids (VFA), and ruminal bacteria populations via quantitative PCR amplification of 16S ribosomal DNA genes. Milk yield was not affected by treatment effects. Energy balance was lower in YC cows than CON, which was partially explain by the trend for lower dry matter intake as % body weight in YC cows than CON. Cows fed YC had greater overall ruminal pH and greater total VFA (mM) at 60 d of treatment period. There was a contrasting greater molar proportion of isovalerate and lower acetate proportion in YC-fed cows compared with CON cows. Although the ruminal abundance of specific fiber-digesting bacteria, including Eubacterium ruminantium and Ruminococcus flavefaciens, was increased in YC cows, others such as Fibrobacter succinogenes were decreased. The abundance of amylolytic bacteria such as Ruminobacter amylophilus and Succinimonas amylolytica were decreased in YC cows than CON. Our results indicate that the yeast culture supplementation seems to promote some specific fiber-digesting bacteria while decreasing amylolytic bacteria, which might have partially promoted more neutral rumen pH, greater total VFA, and isovalerate.

Dietary Supplementation with Saccharomyces cerevisiae, Clostridium butyricum and Their Combination Ameliorate Rumen Fermentation and Growth Performance of Heat-Stressed Goats

Simple Summary

Heat stress commonly happens to goats raised in the Jianghuai region of China during the summer and inevitably contributes to a loss of animal production. Dietary supplementation with probiotics is one of the practical approaches to improve animal production. By dietary supplementation with Saccharomyces cerevisiae, Clostridium butyricum, and their combination to the heat-stressed goats, the present study showed these probiotics effectively alleviate heat stress by improving the rumen fermentation function and growth performance. Therefore, this study provides a reference for the application of these two probiotics in ruminant production during heat stress.

Abstract

This study aimed to evaluate the effects of Saccharomyces cerevisiae, and their combination on rumen fermentation and growth performance of heat-stressed goats. Twelve heat-stressed goats (20.21 ± 2.30 kg) were divided equally into four groups: control group (CG, fed the basal diet, Saccharomyces cerevisiae supplemented group (SC, 0.60% Saccharomyces cerevisiae added to the basal diet), Clostridium butyricum supplemented group (CB, 0.05% Clostridium butyricum added to the basal diet), and their combination supplemented group (COM 0.60% Saccharomyces cerevisiae and 0.05% Clostridium butyricum added to the basal diet) and were assigned to a 4 × 3 incomplete Latin square design. The rumen fluid and feces were collected for fermentation parameters and feed digestibility analysis, and animal growth performance was also assessed during all the experiment periods. The results showed that rumen pH, rumen cellulolytic enzymes (avicelase, CMCaes, cellobiase, and xylanase) activities, and the concentrations of rumen total volatile fatty acid (TVFA), acetic acid, and propionic acid were significantly increased with Saccharomyces cerevisiae, Clostridium butyricum, and their combination supplementation (p < 0.05). Besides, the dry matter intake (DMI), average daily gain (ADG), and the digestibility of dry matter (DM), neutral detergent fiber (NDF), and acidic detergent fiber (ADF) were significantly increased (p < 0.05) with supplemented these probiotics. However, the ammonia nitrogen (NH₃-N) concentration only significantly increased in CB and A/P ratio (acetic acid to propionic acid ratio) only significantly increased in SC and CB. These results indicated that the supplementation with these probiotics could ameliorate rumen fermentation and growth performance of heat-stressed goats.

Influence of yeast on rumen fermentation, growth performance and quality of products in ruminants: A review

This review aims to give an overview of the efficacy of yeast supplementation on growth performance, rumen pH, rumen microbiota, and their relationship to meat and milk quality in ruminants. The practice of feeding high grain diets to ruminants in an effort to increase growth rate and weight gain usually results in excess deposition of saturated fatty acids in animal products and increased incidence of rumen acidosis. The supplementation of yeast at the right dose and viability level could counteract the acidotic effects of these high grain diets in the rumen and positively modify the fatty acid composition of animal products. Yeast exerts its actions by competing with lactate-producing (Streptococcus bovis and Lactobacillus) bacteria for available sugar and encouraging the growth of lactate-utilising bacteria (Megasphaera elsdenii). M. elsdenii is known to convert lactate into butyrate and propionate leading to a decrease in the accumulation of lactate thereby resulting in higher rumen pH. Interestingly, this creates a conducive environment for the proliferation of vaccenic acid-producing bacteria (Butyrivibrio fibrisolvens) and ciliate protozoa, both of which have been reported to increase the ruminal concentration of trans-11 and cis-9, trans-11-conjugated linoleic acid (CLA) at a pH range between 5.6 and 6.3. The addition of yeast into the diet of ruminants has also been reported to positively modify rumen biohydrogenation pathway to synthesise more of the beneficial biohydrogenation intermediates (trans -11 and cis -9, trans -11). This implies that more dietary sources of linoleic acid, linolenic acid, and oleic acid along with beneficial biohydrogenation intermediates (cis-9, trans-11-CLA, and trans-11) would escape complete biohydrogenation in the rumen to be absorbed into milk and meat. However, further studies are required to substantiate our claim. Therefore, techniques like transcriptomics should be employed to identify the mRNA transcript expression levels of genes like stearoyl-CoA desaturase, fatty acid synthase, and elongase of very long chain fatty acids 6 in the muscle. Different strains of yeast need to be tested at different doses and viability levels on the fatty acid profile of animal products as well as its vaccenic acid and rumenic acid composition.

The effects of supplementing yeast fermentation products on gut permeability, hormone concentration, and growth in newborn dairy calves

The objectives of this study were to evaluate the effect of the use of yeast fermentation products (YFP) on growth, hormone concentration, and gut permeability in dairy calves. One hundred and twenty heifers were randomly assigned to one of three treatments: control group with no YFP supplementation (C), Saccharomyces cerevisiae fermentation products (SCFP) supplementation (1 g/head/d of SmartCare [Diamond V] in the milk and 0.7% on dry matter basis of NutriTek [Diamond V] on the starter feed), or Aspergillus oryzae fermentation extracts (AOFE) supplementation (3 g/head/d of LXtract1224 [Biozyme Inc.] in the milk). All calves received 6 L/d of pasteurized milk and had ad libitum access to water and dry feed along the study. Body weight (BW) was recorded at birth and on days 14, 30, and 45 and at weaning. Dry feed (starter) offered was measured daily and refusals twice a week to obtain starter intake (SI). Diarrhea events were recorded daily and fecal scores were classified by using a four-point scale. Blood was sampled on days 7 and 14 for plasma glucose, nonesterified fatty acids (NEFA), insulin, and IL-1β concentrations. Lactulose and D-mannitol were included in the morning feeding of day 14 and blood samples were taken an hour after feeding for assessment of intestinal permeability. On day 14, blood samples were taken for plasma glucagon-like peptide 2 (GLP-2) concentration. On day 30, fecal samples were collected for measurements of Salmonella and Escherichia coli concentration on feces. No treatment differences (P ≥ 0.13) were found for BW or SI. There was a time by treatment difference (P = 0.01) in average daily gain (ADG) on day 45 where C animals had a greater ADG when compared with SCFP and AOFE. Diarrhea incidence did not change between treatments (P = 0.97) and Salmonella and E. coli were not found in feces. There were no differences (P > 0.60) between treatments for plasma GLP-2, glucose, insulin, lactulose, nor D-mannitol concentrations. There was a time by treatment tendency (P = 0.06) for NEFA concentration which tended to be greater on day 7 for C and AOFE when compared with day 14. Plasma IL-1β concentration showed a treatment tendency which tended (P = 0.06) to be greater for SCFP when compared with C. Under the current conditions, supplementation with YFP did not improve performance parameters. Plasma GLP-2 concentration, intestinal permeability, and plasma metabolites did not differ after yeast fermentation products supplementation.

Effect of temperature on single- and mixed-strain fermentation of ruminant feeds

Use of raw feedstuffs for livestock is limited by low digestibility. Recently, fermentation of feedstuffs has been highlighted as a new way to improve nutrient absorption through the production of organic acids using inoculated microorganisms, which can also play a probiotic role. However, standard procedures for feedstuff fermentation have not been clearly defined because the process is influenced by climatic variation, and an analytical standard for fermented feedstuffs is lacking. This study aimed to evaluate the microbiological and biochemical changes of feedstuffs during fermentation at temperatures corresponding to different seasons (10°C, 20°C, 30°C, and 40°C). We also investigated the effects of yeast, lactic acid bacteria (LAB), and Bacillus spp. on fermentation and determined the results of their interactions during fermentation. The viable cells were observed within 8 days in single-strain fermentation. However, when feedstuffs were inoculated with a culture of mixed strains, LAB were predominant at low temperatures (10°C and 20°C), while Bacillus spp. was predominant at high temperatures (30°C and 40°C). A significant drop in pH from 6.5 to 4.3 was observed when LAB was the dominant strain in the culture, which correlated with the concentrations of lactic acid. Slight ethanol production was detected above 20°C regardless of the incubation temperature, suggesting active metabolism of yeast, despite this organism making up a marginal portion of the microbes in the mixed culture. These results suggested that fermentation temperature significantly affects microbiological profiles and biochemical parameters, such as pH and the lactic acid concentration, of fermented feedstuffs. Our data provide valuable information for the determination of industrial standards for fermented feedstuffs.

Evaluation of different inclusion levels of dry live yeast impacts on various rumen parameters and in situ digestibilities of dry matter and neutral detergent fiber in growing and finishing beef cattle

This study evaluated the effects of supplementing dry live yeast (LY; Saccharomyces cerevisiae) on in vitro gas production (IVGP) fermentation dynamics, pH, and CH4 concentration at 48 h, and in situ rumen parameters and digestibility of DM (DMD) and NDF (NDFD) of growing cattle during 3 feeding phases: grower (GRW) for 17 d (38% steamed-flaked corn; SFC), transition (TRANS) for 15 d (55.5% SFC: 1.2 Mcal/kg NEg), and finisher (FIN) for 13 d (73% SFC: 1.23 Mcal/kg NEg). Twenty British-crossbred, ruminally cannulated steers (183 kg ± 44 kg) 6 mo of age were blocked by weight into 5 pens containing Calan gate feeders and received a control (CON) diet (17.2% CP, 35.8% NDF, 86.7% DM) without LY on days -12 to 0. After that, animals were randomly assigned to treatments (TRT), 5 animals per TRT: CON or LY at inclusion rates of 5 g/d (LY1), 10 g/d (LY2), or 15 g/d (LY3) top dressed every morning at 0800 for 45 d. The DMD and NDFD were assessed during 7 separate collection days using in situ nylon bags containing 5 g of GRW, TRANS, or FIN diets, incubated at 1200 for 48 h. Protozoa counts (PC) were determined during 5 collection periods. Data were analyzed as a repeated measure within a randomized complete block design, assuming a random effect of the pen. For GRW, TRT altered the total gas production of the nonfiber carbohydrate (NFC; P = 0.045) and the fractional rate of degradation (kd) of the fiber carbohydrate (FC) pool (P = 0.001) in a cubic pattern (P ≤ 0.05): LY2 had the most gas production and fastest kd. TRT also influenced DMD (P = 0.035) and NDFD (P = 0.012) with LY2 providing the greatest digestibility. For TRANS, TRT tended to affect the NFC kd (P = 0.078) and influenced pH (P = 0.04) and DMD (P < 0.001) in which LY2 yielded the fastest kd, highest pH, and greatest DMD. For FIN, there was an effect of TRT on total gas production (P < 0.001) and kd (P = 0.004) of the NFC pool, FC kd (P = 0.012), in vitro CH4 concentration (P < 0.001), PC (P < 0.001), DMD (P = 0.039), and NDFD (P = 0.008). LY1 had the highest PC and provided the greatest DMD and NDFD. LY2 had the fastest kd of both the NFC and FC pools and had the least CH4 concentration. LY3 had the greatest NFC gas production. No specific dose-response pattern was observed, but 10 g/d provided the most beneficial result for all diets. We concluded that supplementation with LY affected IVGP as well as ruminal parameters and digestibilities.

DI/LC-MS/MS-Based Metabolome Analysis of Plasma Reveals the Effects of Sequestering Agents on the Metabolic Status of Dairy Cows Challenged with Aflatoxin B1

The study applied a targeted metabolomics approach that uses a direct injection and tandem mass spectrometry (DI–MS/MS) coupled with a liquid chromatography–tandem mass spectrometry (LC–MS/MS)-based metabolomics of plasma to evaluate the effects of supplementing clay with or without Saccharomyces cerevisiae fermentation product (SCFP) on the metabolic status of dairy cows challenged with aflatoxin B₁. Eight healthy, lactating, multiparous Holstein cows in early lactation (64 ± 11 DIM) were randomly assigned to one of four treatments in a balanced 4 × 4 duplicated Latin square design with four 33 d periods. Treatments were control, toxin (T; 1725 µg aflatoxin B₁ (AFB₁)/head/day), T with clay (CL; 200 g/head/day), and CL with SCFP (YEA; 35 g of SCFP/head/day). Cows in T, CL, and YEA were dosed with aflatoxin B₁ (AFB₁) from days 26 to 30. The sequestering agents were top-dressed from day 1 to 33. On day 30 of each period, 15 mL of blood was taken from the coccygeal vessels and plasma samples were obtained from blood by centrifugation and analyzed for metabolites using a kit that combines DI–MS/MS with LC–MS/MS-based metabolomics. The data were analyzed using the GLIMMIX procedure of SAS. The model included the effects of treatment, period, and random effects of cow and square. Significance was declared at p ≤ 0.05. Biomarker profiles for aflatoxin ingestion in dairy cows fed no sequestering agents were determined using receiver–operator characteristic (ROC) curves, as calculated by the ROCCET web server. A total of 127 metabolites such as amino acids, biogenic amines, acylcarnitines, glycerophospholipids, and organic acids were quantified. Compared with the control, T decreased (p < 0.05) plasma concentrations of alanine, leucine, and arginine and tended to decrease that of citrulline. Treatment with CL had no effects on any of the metabolites relative to the control but increased (p ≤ 0.05) concentrations of alanine, leucine, arginine, and that of citrulline (p = 0.07) relative to T. Treatment with YEA resulted in greater (p ≤ 0.05) concentrations of aspartic acid and lysine relative to the control and the highest (p ≤ 0.05) plasma concentrations of alanine, valine, proline, threonine, leucine, isoleucine, glutamic acid, phenylalanine, and arginine compared with other treatments. The results of ROC analysis between C and T groups revealed that the combination of arginine, alanine, methylhistidine, and citrulline had sufficient specificity and sensitivity (area under the curve = 0.986) to be excellent potential biomarkers of aflatoxin ingestion in dairy cows fed no sequestering agents. This study confirmed the protective effects of sequestering agents in dairy cows challenged with aflatoxin B₁.

Effects of feeding live yeast at 2 dosages on performance and feeding behavior of dairy cows under heat stress

The objectives were to evaluate the effects of feeding different amounts of supplemental live yeast (LY) on performance and digestion of cows under heat stress. Sixty Holstein cows, 27 multiparous and 33 primiparous, were blocked by parity and milk yield in the first 20 d in milk (DIM) and randomly assigned to receive 0, 0.5, or 1.0 g/d of LY, resulting in daily intakes of 0, 14.2, and 37.6 billion cells, respectively, of Saccharomyces cerevisiae strain CNCM I-1077 from 30 to 107 DIM. Cows were milked twice daily, dry matter intake (DMI) and milk yield were measured daily, and milk components, body weight, and body condition were measured weekly. Blood was sampled weekly and plasma analyzed for concentrations of glucose, fatty acids, urea N, haptoglobin, serum amyloid A, and acid-soluble protein. Digestibility of nutrients was measured in the last 2 wk of the experiment. Ruminal fluid was collected on 2 consecutive days 6 h after the morning feeding for measurements of pH, concentrations of short chain fatty acids, and NH₃-N. Feeding behavior was observed for 48 h on experiment d 21 and 63. The mean ambient temperature was 26.8°C, humidity was 83.2%, and the temperature and humidity index ranged from 73 to 81. Treatment did not affect rectal temperature (38.9 ± 0.04°C) or DMI but increased yield of energy-corrected milk (ECM; 35.2 vs. 36.1 vs. 37.2 kg/d for 0, 0.5, and 1.0 g/d, respectively) and efficiency of conversion of DM into ECM (1.70, 1.79, and 1.83 for 0, 0.5, and 1 g/d, respectively). Feeding LY increased digestibility of crude protein (65.1 vs. 68.8 vs. 70.4%) and neutral detergent fiber (NDF; 47.5 vs. 49.2 vs. 55.2%), and concentration of acetate (64.7 vs. 69.1 vs. 72.2 mM), which resulted in increased concentration of total short chain fatty acids in ruminal fluid (110.3 vs. 117.7 vs. 121.4 mM). Mean ruminal pH increased (5.99 vs. 6.03 vs. 6.26), and proportion of cows with pH <5.8 decreased linearly (42.9 vs. 34.9 vs. 7.7%) with increasing inclusion of LY. Concentrations of acute-phase proteins decreased with increasing amount of LY. Some aspects of feeding behavior were altered by LY, and meal size reduced quadratically (3.2, 3.5, and 2.9 kg of DM, respectively), whereas interval between rumination bouts tended to reduce linearly (122, 96.5, and 90.7 min, respectively) with increasing dose of LY. Chewing time per kilogram of NDF tended to increase linearly (71.6, 71.3, and 81.6 min/kg, respectively) with increasing dose of LY. The estimated net energy for lactation of the diet increased 5.2%, from 1.72 Mcal/kg of DM for 0 g of LY to 1.81 Mcal/kg for 1 g of LY. Feeding 1 g of LY/d to cows under heat stress increased yield of ECM and efficiency of feed conversion into ECM, improved diet digestibility, and increased ruminal fluid pH; these responses might be related either to direct effects of LY on ruminal microbial activity or to changes in feeding behavior that improved digestion of cows in heat stress.

Effect of Saccharomyces cerevisiae fermentation product on feed intake parameters, lactation performance, and metabolism of transition dairy cattle

The transition period in dairy cattle is characterized by many stressors, including an abrupt diet change, but yeast product supplementation can alter the rumen environment to increase dairy cattle productivity. Saccharomyces cerevisiae fermentation product (SCFP) was fed from -29 ± 5 to 42 d relative to calving (RTC) to evaluate the effects on feed intake, milk production, and metabolism. Treatments were control (n = 30) or SCFP (n = 34) incorporated into a total mixed ration. Cows were individually fed 3×/d prepartum and 2×/d postpartum. Blood samples were collected once during each of the following time points RTC: d -28 to -24 (wk -4), d -14 to -10 (wk -2), d 3 to 7 (wk 1), d 12 to 16 (wk 2), and d 31 to 35 (wk 5). Liver biopsies were taken once between d -19 and d -12 (wk -3) and at 14 d in milk. Cows were milked 2×/d, and samples were taken 2 d/wk for composition analysis. Dry matter intake did not differ by treatment, but SCFP increased meals per day and decreased time between meals. Body weight (measured at enrollment, d 0, and d 42 RTC) and body condition score (scored weekly) were not affected by treatment. Milk, energy-corrected milk, and fat-corrected milk yields did not differ by treatment. Milk fat concentration was greater for SCFP, with significant differences in wk 4 and 5. Milk lactose concentration tended to be greater for the control and milk urea nitrogen tended to be lesser for the control, but there were no treatment effects on milk protein concentration or somatic cell count. Assuming equal digestibility, energy balance deficit was greater for SCFP than for the control (-6.15 vs. -4.34 ± 0.74 Mcal/d), with significant differences in wk 4 and 5. Plasma concentrations of free fatty acids, β-hydroxybutyrate, glucose, and insulin did not differ with treatment, but cholesterol was greater for SCFP. Liver triglyceride increased and liver cholesterol decreased with time. Liver triglyceride did not differ by treatment, but liver cholesterol tended to be lesser in SCFP. Relative mRNA abundance of cholesterol-related genes (SREBF2, HMGCS1, HMGCR, MTTP, SPOB100, APOA1), FGF21, and CPT1A did not differ by treatment, but PCK1 tended to be greater for SCFP. The ketogenic transcript HMGCS2 was greater for SCFP, which aligns with SCFP increasing incidence of subclinical ketosis; however, BDH did not differ between treatments. In conclusion, SCFP supplementation increased meals per day with less time between meals, increased milk fat concentration, altered cholesterol metabolism, and increased incidence of subclinical ketosis, but early-lactation milk yield and metabolism were generally unaffected.

Effect of yeast products supplementation during transition period on metabolic profile and milk production in dairy cows

The aim of the current study was to assess the effect that supplementation with yeast culture plus enzymatically hydrolyzed yeast (YC-EHY) during the transition period and lactation had on the performance, somatic cell count (SCC), and metabolic profile of dairy cows. Thirty multiparous Holstein dairy cows were divided into two groups. The treatments were 0 supplementation (control) and supplementation with 28 g/cow/day of YC-EHY. The supplementation began 35 ± 5 days before the expected calving date. The cows were kept in their respective treatments for 50 days after the calving date. Body condition score (BCS), body weight, milk composition, SCC, and milk yield were assessed on a 2-weekly basis. Plasma samples were collected on days - 21st, - 7th, 0, 3rd, 7th, and weekly thereafter until 42 days postpartum and analyzed for albumin, β-hydroxybutyrate (BHBA), urea, and non-esterified fatty acids (NEFA). There was an effect of treatment on milk yield in the supplemented animals in comparison to the control group (27.88 ± 0.98 vs 24.58 ± 0.99 kg/days, P = 0.03). There was no effect of treatment (P > 0.05) on variables like 3.5% fat-corrected milk (FCM) and energy-corrected milk (ECM), milk component (%), milk composition yield (kg/day), and SCC. There was an interaction between group × days on ECM (P = 0.04) and protein (P = 0.008). The supplementation had no effect on the analyzed metabolites and on body weight and BCS. The supplementation with YC-EHY during the transition period and lactation improved milk yield without altering the metabolic profile.

Changes in the rumen and colon microbiota and effects of live yeast dietary supplementation during the transition from the dry period to lactation of dairy cows

The first objective of this study was to evaluate the dynamics and their potential association with animal performance of the microbiota in both the rumen and colon of dairy cows as they move from a nonlactation to a lactation ration. The second objective was to assess the potential effects on the microbiota of live yeast supplementation. Twenty-one Holstein cows were split in 2 treatments consisting of 1 × 10¹⁰ cfu/d of live yeast (LY; n = 10) or no supplementation (control; n = 11) starting 21 d before until 21 d after calving. At 14 d before and 7 and 21 d after calving, samples of rumen and colon digesta were obtained from each cow using an endoscope. Total DNA was extracted and submitted to high-throughput sequencing. Shannon diversity index, in both the rumen and colon, was unaffected by LY; however, in the rumen it was lowest 7 d after calving and returned to precalving values at 21 d in milk, whereas in the colon it was greatest 14 d before calving but decreased after calving. In the rumen, LY supplementation increased the relative abundance (RA) of Bacteroidales (group UCG-001), Lachnospiracea (groups UCG-002 and UCG-006), and Flexilinea 14 d before calving, and increased RA of Streptococcus 21 d after calving compared with control cows. However, changes in the ruminal microbiota were more drastic across days relative to calving than as influenced by the dietary treatment, and the effect of LY in the colon was milder than in the rumen. The ruminal RA of several genera was associated with postcalving DMI, and that of Gastranaerophilales was the only order positively associated with milk yield. Several genera were positively correlated with feed efficiency, with Clostridiales (unclassified) being the only genus negatively associated with feed efficiency. In the colon, Prevotellaceae (group Ga6A1) was the only genus positively associated with feed efficiency. The ruminal RA of Prevotella 7 and Ruminobacter 14 d precalving was negatively correlated with dry matter intake and milk yield postcalving. The RA of Parabacteroides in the colon 14 d before calving was negatively correlated with milk yield, whereas the RA of Eggerthellaceae (unclassified) and Erysipelotrichaceae (groups c and unclassified) were positively correlated with feed efficiency. Interestingly, LY supplementation doubled the RA of Eggerthellaceae (unclassified) in the colon. It is concluded that microbial diversity in the rumen experiences a transient reduction after calving, whereas in the colon, the reduction is maintained at least until 21 d in milk. Most of the effects of LY on rumen microbiota were observed before calving, whereas in the colon, LY effects were more moderate but consistent and independent of the stage of production. The microbial community of the rumen after calving is more associated with feed intake, milk yield, and feed efficiency than that of the colon. However, the colon microbiota before calving is more associated with feed efficiency after calving than that of the rumen.

Use of live yeast and mannan-oligosaccharides in grain-based diets for cattle: Ruminal parameters, nutrient digestibility, and inflammatory response

The objective of this study was to evaluate the effects of diet supplementation with live yeast (Saccharomyces cerevisiae) and mannan-oligosaccharides (MOS) on ruminal parameters, nutrient digestibility, and the inflammatory response in cattle fed grain-based diets. Three Holstein steers (body weight of 497±3 kg) with ruminal and duodenal cannulas were assigned to a 3 × 3 Latin square design. The animals were kept in individual pens and fed a diet containing 5% sugarcane bagasse and 95% concentrate (906.5 g/kg ground corn). Diet treatments were Control (without additive), Yeast (1.5 g/kg DM live yeast Saccharomyces cerevisiae, NCYC 996) and MOS (1.5 g/kg DM MOS, β-glucans and mannan). Dry matter intake, ruminal, intestinal, and total digestibility of nutrients were not affected by the treatments. The ruminal concentration of isobutyric acid increased in animals fed on diets supplemented with Yeast and MOS, whereas isovaleric acid increased with Yeast and decreased with MOS supplementation. Dietary supplementation with Yeast and MOS increased pH and decreased ammonia concentration in the rumen. Lipopolysaccharide (LPS) concentrations in the rumen and duodenal fluid were not influenced by the additives. However, both Yeast and MOS decreased the plasma levels of LPS and serum amyloid A (SAA). In conclusion, when high-concentrate diets fed to beef cattle are supplemented with either Yeast or MOS, ruminal pH is increased, LPS translocation into the blood stream is decreased, and blood SAA concentration is decreased. These factors reduce the inflammation caused by consumption of grain-based diets, and either supplement could be used to improve the rumen environment in beef cattle susceptible to ruminal subacute acidosis.

Use of probiotics and botanical extracts to improve ruminant production in the tropics: A review

Ruminant production, especially in the tropics and developing countries suffers a setback when compared with the temperate and developed countries, which is attributable to the kinds of available feed resources in the region of production. In the tropics, ruminants are restricted to grazing on low-quality forages, crop residues and agro-industrial by-products with very little or no concentrate diets, which adversely affect the animals in exhibiting their full production potential. Considering this fact, there is an increasing interest in improving the digestibility of these feed resources. In recent years, researchers have explored several methods to enhance the functions of rumen microflora, improve digestion and fermentation processes, as well as increase bioavailability and utilization of nutrients through feed supplementation. This review aims to explore the positive effects of supplementation of ruminant diets with probiotics or botanical extracts and their metabolites on the productivity of the animals. Moreover, the functions of these non-pathogenic and non-toxic live microorganisms (probiotics) and plant biologically active compounds (botanical extract) are explored because of the ban on non-therapeutic use of antibiotics as growth promoters coupled with the critical preference of consumers to high quality and safe animal products. It has been reported that these alternative supplemental products have a beneficial impact on both animal health and productivity, which is affecting stabilization of rumen environment, inhibition of pathogenic bacteria proliferation in gastro-intestinal tract, modulation of immune response, increase in fibre degradation and fermentation, nutrients availability and utilization, animal growth performance and milk production, among others. However, long-term in vivo studies are still required to determine the synergetic effects of these 2 safe supplemental products.

Inclusion of live yeast and mannan-oligosaccharides in high grain-based diets for sheep: Ruminal parameters, inflammatory response and rumen morphology

The objective of this study was to evaluate the effects of dietary supplementation with live yeast (Saccharomyces cerevisiae), mannan-oligosaccharides and the combination of these additives on the inflammatory response, ruminal parameters and rumen morphology of sheep fed a high grain-based diet. Thirty-Two Dorper x Santa Ines crossbred lambs with an average weight of 24±2 kg were distributed in a completely randomized design. The animals were housed in individual stalls and fed ad libitum. Diet treatments were: Control (without additive); LY (2 g/kg DM of live yeast, Saccharomyces cerevisiae), MOS (2 g/kg DM of mannan-oligosaccharides) and LY+MOS (2 g/kg DM of LY + 2 g/kg DM of MOS). The experiment lasted 42 days. The supplementation with MOS alone and the additives combination resulted in increased ruminal pH (P<0.01), while the total concentrations of short chain fatty acids (SCFA) in the rumen were higher (P<0.05) only in the diets with LY and MOS. Ammonia (NH3) concentration in the rumen decreased (P<0.04) with the additives usage. Diets with LY, MOS and with additives combination reduced (P<0.01) the levels of lipopolysaccharides (LPS) in the plasma with values of 0.46; 0.44 and 0.04 EU/mL, respectively when compared to the control (0.93 EU/mL). MOS and LY+MOS treatments had reduced stratum corneum thickness (P<0.01) in comparison to the control treatment. The total thickness of ruminal epithelium was lower with the addition of MOS in the diet (P<0.03) than with LY additive. The incidence and severity of hepatic abscesses in animals whose diet was supplemented with LY and LY+MOS was lower (P<0.05) than in animals fed the control diet. The use of LY, MOS and LY+MOS in the high-concentrate diets for sheep reduced NH3 concentrations and LPS translocation into the bloodstream. Diets containing MOS and LY+MOS enhanced the health of the ruminal epithelium by reducing the thickness of the stratum corneum, and diets containing LY and LY+MOS decreased the incidence and severity of hepatic abscesses.

Changes in gene expression in the rumen and colon epithelia during the dry period through lactation of dairy cows and effects of live yeast supplementation

The objectives of this study were (1) to use endoscopy to collect biopsies from the rumen and colon epithelia to describe changes in gene expression in these 2 tissues as cows move from a dry to a lactation ration and (2) to evaluate the potential influence that supplementation of live yeast could exert on these 2 epithelia. Twenty-one Holstein cows were split into 2 treatments and received either 300 g/d of corn containing 1 × 10¹⁰ cfu/d of live yeast (LY; n = 10) or 300 g/d of corn with no supplementation (control; n = 11) starting 21 ± 2.6 d (average ± SD) before until 21 d after calving. At 14 ± 2.6 d before the expected calving date, and exactly at 7 and 21 d after calving, rumen and colon biopsies were obtained from each cow using an endoscope. Total RNA was extracted from rumen and colon tissues, and the expression of IL10, TNFA, TLR4, IL1B, PCNA, MKI67, SGLT1, BAX, CASP3, OCLN, CLDN4, HSPA1A, HSPB1, DEFB1, and MCT1 (the latter only in rumen samples) was quantified by quantitative PCR. Overall, fluctuations in expression of the selected genes in the colon between the 2 stages of production and the 2 treatments were smaller than those found in the rumen. In the rumen epithelium, expression of TLR4 and DEFB1 was greatest before calving, with LY cows having a greater expression of TLR4 than control cows. Similarly, expression of IL10 was greatest in LY cows before calving. Expression of TNFA in the rumen epithelium of control cows was lowest at 21 DIM but in LY cows was kept steady among production stages. The expression of PCNA and MKI67 in the rumen epithelium was greatest at 7 DIM, indicating a high proliferation rate of this epithelium after calving. In the colon mucosa, expression of TLR4 and DEFB1 was greater than in the rumen, and DEFB1 expression was greater in LY cows than in control cows. The use of an endoscope allowed us to study the dynamics of rumen epithelium adaptation to increased supply of concentrate after calving, consisting of increased epithelia remodeling, reduction of the TLR4, and increased IL10 expression. Furthermore, the rumen epithelium of dry cows responded rapidly to live yeast, with changes in the expression of genes involved in the immune response becoming evident after 7 d of exposure to yeast. The expression of genes related to the immune response (mainly TLR4 and DEFB1) in the colon mucosa was greater than in the rumen, and the expression of DEFB1 was further stimulated by live yeast. It is concluded that the use of an endoscope allows the study of gene expression patterns in the rumen and hindgut epithelia. We report marked changes in the rumen wall and more modest changes in the colon when transitioning from a dry to a lactation ration. Furthermore, supplementation of live yeast fostered and increased expression of genes regulating inflammation and epithelial barrier in the rumen, and in the colon it increased the expression of DFEB1 coding for an antimicrobial peptide.

Effects of supplementing yeast culture to diets differing in starch content on performance and feeding behavior of dairy cows

The objectives were to evaluate the effects of a culture of Saccharomyces cerevisiae (YC) on lactation performance of cows fed diets differing in starch content. Fifty-six Holstein cows at 42 d postpartum were blocked by parity and milk production and randomly assigned to 1 of 4 treatments, low starch (23% diet DM) and no YC (LS-control), low starch and 15 g/d of YC (LS-YC), high starch (29% diet DM) and no YC (HS-control), and high starch and 15 g/d of YC (HS-YC). The experiment lasted 14 wk. Blood was sampled twice weekly during the first 5 wk in the experiment. Feeding behavior was evaluated in 2 consecutive days when cows were 33 d in the experiment. On d 92 in the experiment, cows were challenged with 3 kg of corn grain DM immediately before the morning feeding. Blood was sampled in the first 12 h after the challenge. Rumen fluid was collected 5 h after the challenge, and pH, ammonia N, short-chain fatty acids, and lactate concentrations were quantified. Lactation performance was measured daily before and after the challenge. Supplementation with YC increased yields of 3.5% fat-corrected milk and energy-corrected milk by 2.2 and 2.0 kg/d, and the increments were observed in both low- and high-starch diets. Feeding HS tended to decrease milk fat content (LS = 3.88 vs. HS = 3.73%), but increased concentration (LS = 2.87 vs. HS = 3.00%) and yield (LS = 1.11 vs. HS = 1.20 kg/d) of milk true protein. Feeding YC increased yields of fat and true protein in milk by 100 and 60 g/d. Energy balance, body weight, and feed efficiency did not differ with treatments. Feeding HS reduced eating time (LS = 177 vs. HS = 159 min/12 h) and intermeal interval (LS = 103 vs. HS = 82 min), but tended to increase eating rate (LS = 139 vs. HS = 150 g/min). Interactions were detected between level of starch and YC for ruminating time, meal duration, and meal size because within LS, feeding YC increased ruminating time 23 min/12 h, but reduced meal duration 6 min/meal and meal size 0.7 kg/meal. Concentrations of glucose in plasma increased (LS = 62.1 vs. HS = 63.8 mg/dL), whereas those of urea N decreased (LS = 10.1 vs. HS = 9.4 mg/dL) with feeding HS compared with LS in the first 5 wk in the experiment, and the same responses were observed after the challenge with corn grain. After the challenge, rumen pH was less and short-chain fatty acid concentrations were greater in cows fed HS compared with those fed LS; however, supplementing YC to high-starch diets increased rumen pH (HS-control = 5.72 vs. HS-YC = 6.12) and reduced concentrations of lactate in rumen fluid (HS-control = 7.72 vs. HS-YC = 1.33 mM) and haptoglobin in plasma 28%. Feeding YC improved lactation performance irrespective of the level of dietary starch and reduced the risk of subacute rumen acidosis induced by a grain challenge when cows were fed a high-starch ration.

An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation

Sub-acute ruminal acidosis (SARA) is a gastrointestinal functional disorder in livestock characterized by low rumen pH, which reduces rumen function, microbial diversity, host performance, and host immune function. Dietary management is used to prevent SARA, often with yeast supplementation as a pH buffer. Almost nothing is known about the effect of SARA or yeast supplementation on ruminal protozoal and fungal diversity, despite their roles in fiber degradation. Dairy cows were switched from a high-fiber to high-grain diet abruptly to induce SARA, with and without active dry yeast (ADY, Saccharomyces cerevisiae) supplementation, and sampled from the rumen fluid, solids, and epimural fractions to determine microbial diversity using the protozoal 18S rRNA and the fungal ITS1 genes via Illumina MiSeq sequencing. Diet-induced SARA dramatically increased the number and abundance of rare fungal taxa, even in fluid fractions where total reads were very low, and reduced protozoal diversity. SARA selected for more lactic-acid utilizing taxa, and fewer fiber-degrading taxa. ADY treatment increased fungal richness (OTUs) but not diversity (Inverse Simpson, Shannon), but increased protozoal richness and diversity in some fractions. ADY treatment itself significantly (P < 0.05) affected the abundance of numerous fungal genera as seen in the high-fiber diet: Lewia, Neocallimastix, and Phoma were increased, while Alternaria, Candida Orpinomyces, and Piromyces spp. were decreased. Likewise, for protozoa, ADY itself increased Isotricha intestinalis but decreased Entodinium furca spp. Multivariate analyses showed diet type was most significant in driving diversity, followed by yeast treatment, for AMOVA, ANOSIM, and weighted UniFrac. Diet, ADY, and location were all significant factors for fungi (PERMANOVA, P = 0.0001, P = 0.0452, P = 0.0068, Monte Carlo correction, respectively, and location was a significant factor (P = 0.001, Monte Carlo correction) for protozoa. Diet-induced SARA shifts diversity of rumen fungi and protozoa and selects against fiber-degrading species. Supplementation with ADY mitigated this reduction in protozoa, presumptively by triggering microbial diversity shifts (as seen even in the high-fiber diet) that resulted in pH stabilization. ADY did not recover the initial community structure that was seen in pre-SARA conditions.

The effect of Saccharomyces cerevisiae on in vitro growth and fermentation of Selenomonas ruminantium and Megasphaera elsdenii

Stimulation of lactate utilization by Selenomonas ruminantium and Megasphaera elsdenii may help in reducing problems associated with rumen acidosis. The objective of this study was to determine the effect of a Saccharomyces cerevisiae live culture and Saccharomyces cerevisiae fermentation products on in vitro growth and fermentation of lactate-utilizing ruminal bacteria, S. ruminantium (ATCC 19205) and M. elsdenii (ATCC 25940). The cultures were run for 0, 6, 12, 24 and 48 h under anaerobic conditions on a growth medium supplemented with a yeast live culture (SC) or with yeast fermentation products (SCFP) and, as reference, on the same medium without supplementation (CON). Neither SC nor SCFP had a significant effect on the growth of S. ruminantium after 6, 12 and 24 h of incubation, but the live yeast culture significantly (P≤0.05) improved the growth of these bacteria after 48 h of incubation. The yeast fermentation products significantly (P≤0.05) decreased pH and increased lactate synthesis by S. ruminantium. The Saccharomyces cerevisiae live culture significantly improved the growth of M. elsdenii after 12 and 24 h of incubation, and the S. cerevisiae fermentation products increased its growth after 48 h. The After 24 and 48 h of incubation the Saccharomyces cerevisiae live culture reduced the concentration of total volatile fatty acids (VFA), while caproate was the main product of in vitro fermentation of M. elsdenii (P≤0.05). Saccharomyces cerevisiae live cultures may improve microbial fibre fermentation in the rumen by maintaining optimal pH conditions.

Generation and Characterization of Acid Tolerant Fibrobacter succinogenes S85

Microorganisms are key components for plant biomass breakdown within rumen environments. Fibrobacter succinogenes have been identified as being active and dominant cellulolytic members of the rumen. In this study, F. succinogenes type strain S85 was adapted for steady state growth in continuous culture at pH 5.75 and confirmed to grow in the range of pH 5.60–5.65, which is lower than has been reported previously. Wild type and acid tolerant strains digested corn stover with equal efficiency in batch culture at low pH. RNA-seq analysis revealed 268 and 829 genes were differentially expressed at pH 6.10 and 5.65 compared to pH 6.70, respectively. Resequencing analysis identified seven single nucleotide polymorphisms (SNPs) in the sufD, yidE, xylE, rlmM, mscL and dosC genes of acid tolerant strains. Due to the absence of a F. succinogenes genetic system, homologues in Escherichia coli were mutated and complemented and the resulting strains were assayed for acid survival. Complementation with wild-type or acid tolerant F. succinogenes sufD restored E. coli wild-type levels of acid tolerance, suggesting a possible role in acid homeostasis. Recent genetic engineering developments need to be adapted and applied in F. succinogenes to further our understanding of this bacterium.