Ruminal acidosis and its definition: A critical review

Ruminal acidosis occurs as a continuum of disorders, stemming from ruminal dysbiosis and disorders of metabolism, of varying severity. The condition has a marked temporal dynamic expression resulting in cases expressing quite different rumen concentrations of VFA, lactic acid, ammonia, and rumen pH over time. Clinical ruminal acidosis is an important condition of cattle and subclinical ruminal acidosis (SRA) is very prevalent in many dairy populations with estimates between 10 to 26% of cows in early lactation. Estimates of the duration of a case suggest the lactational incidence of the condition may be as high as 500 cases per 100 cows in the first 100 d of lactation. Historical confusion about the etiology and pathogenesis of ruminal acidosis led to definitions that are not fit for purpose as acidic ruminal conditions solely characterized by ruminal pH determination at a single point fail to reflect the complexity of the condition. Use of a model, based on integrated ruminal measures including VFA, ammonia, lactic acid, and pH, for evaluating ruminal acidosis is fit for purpose, as indicated by meeting postulates for assessing metabolic disease, but requires a method to simplify application in the field. While it is likely that this model, that we have termed the Bramley Acidosis Model (BAM), will be refined, the critical value in the model is that it demonstrates that ruminal acidosis is much more than ruminal pH. Disease, milk yield and milk composition are more associated with the BAM than rumen pH alone. Two single VFA, propionate and valerate are sensitive and specific for SRA, especially when compared with rumen pH. Even with the use of such a model, astute evaluations of the condition whether in experimental or field circumstances will be aided by ancillary measures that can be used in parallel or in series to enhance diagnosis and interpretation. Sensing methods including rumination detection, behavior, milk analysis, and passive analysis of rumen function have the potential to improve the detection of SRA; however, these may advance more rapidly if SRA is defined more broadly than by ruminal pH alone.

Mechanistic insights into rumen function promotion through yeast culture (Saccharomyces cerevisiae) metabolites using in vitro and in vivo models

Introduction

Yeast culture (YC) enhances ruminant performance, but its functional mechanism remains unclear because of the complex composition of YC and the uncertain substances affecting rumen fermentation. The objective of this study was to determine the composition of effective metabolites in YC by exploring its effects on rumen fermentation in vitro, growth and slaughter performance, serum index, rumen fermentation parameters, rumen microorganisms, and metabolites in lambs.

Methods

In Trial 1, various YCs were successfully produced, providing raw materials for identifying effective metabolites. The experiment was divided into 5 treatment groups with 5 replicates in each group: the control group (basal diet without additives) and YC groups were supplemented with 0.625‰ of four different yeast cultures, respectively (groups A, B, C, and D). Rumen fermentation parameters were determined at 3, 6, 12, and 24 h in vitro. A univariate regression model multiple factor associative effects index (MFAEI; y) was established to correlate the most influential factors on in vitro rumen fermentation with YC metabolites (x). This identified the metabolites promoting rumen fermentation and optimal YC substance levels. In Trial 2, metabolites in YC not positively correlated with MFAEI were excluded, and effective substances were combined with pure chemicals (M group). This experiment validated the effectiveness of YC metabolites in lamb production based on their impact on growth, slaughter performance, serum indices, rumen parameters, microorganisms, and metabolites. Thirty cross-generation rams (Small tail Han-yang ♀ × Australian white sheep ♂) with good body condition and similar body weight were divided into three treatment groups with 10 replicates in each group: control group, YC group, pure chemicals combination group (M group).

Results

Growth performance and serum index were measured on days 30 and 60, and slaughter performance, rumen fermentation parameters, microorganisms, and metabolites were measured on day 60. The M group significantly increased the dressing percentage, and significantly decreased the GR values of lambs (p  < 0.05). The concentration of growth hormone (GH), Cortisol, insulin (INS), and rumen VFA in the M group significantly increased (p < 0.05).

Discussion

These experiments confirmed that YC or its screened effective metabolites positively impact lamb slaughter performance, rumen fermentation, and microbial metabolism.

Dietary supplementation with live or autolyzed yeast: Effects on performance, nutrient digestibility, and ruminal fermentation in dairy cows

This study was conducted to evaluate the effects of live or autolyzed yeast supplementation on dairy cow performance and ruminal fermentation. Two experiments were conducted to evaluate performance, feed sorting, total-tract apparent digestibility of nutrients, purine derivatives excretion, N utilization, ruminal fermentation, and the abundance of specific bacterial groups in the rumen. In experiment 1, 39 Holstein cows (171 ± 40 DIM and 32.6 ± 5.4 kg/d milk yield) were blocked according to parity, DIM, and milk yield and randomly assigned to the following treatments: control (CON); autolyzed yeast fed at 0.625 g/kg DM (AY; Levabon, DSM-Firmenich); or live yeast fed at 0.125 g/kg DM (LY; Vistacell, AB Vista). Cows were submitted to a 2-wk adaptation period followed by a 9-wk trial. In experiment 2, 8 ruminal cannulated Holstein cows (28.4 ± 4.0 kg/d milk yield and 216 ± 30 DIM), of which 4 were multiparous and 4 were primiparous, were blocked according to parity and enrolled into a 4 × 4 Latin square experiment with 21-d periods (the last 7 d for sampling). Cows within blocks were randomly assigned to treatment sequences: control (CON), LY (using the same product and dietary concentration as described in experiment 1), AY, or autolyzed yeast fed at 0.834 g/kg DM (AY2). In experiments 1 and 2, nutrient intake and total-tract apparent digestibility were not affected by treatments. Sorting for long feed particles (>19 mm) tended to be greater in cows fed yeast supplements than CON in experiment 1. Efficiency of N conversion into milk N was increased when feeding yeast supplements in experiment 1, and 3.5% FCM yield tended to be greater in cows fed yeast supplements than CON. Feed efficiency was increased when yeast supplements were fed to cows in relation to CON in experiment 1. In experiment 2, yield of FCM and fat were greater in cows fed yeast supplements compared with CON. Uric acid concentration and output in urine were increased when feeding yeast supplements when compared with CON. Neither ruminal pH nor total VFA were influenced by treatments. The current study did not reveal treatment differences in ruminal abundance of Anaerovibrio lipolytica, the genus Butyrivibrio, Fibrobacter succinogenes, Butyrivibrio proteoclasticus, or Streptococcus bovis. Yeast supplementation can increase feed efficiency without affecting nutrient intake and digestibility, ruminal VFA concentration, or ruminal abundance of specific bacterial groups. Supplementing live or autolyzed yeast, regardless of the dose, resulted in similar performance.

Feeding live yeast (Saccharomyces cerevisiae) improved performance of mid-lactation dairy cows by altering ruminal bacterial communities and functions of serum antioxidation and immune responses

BACKGROUND

The utilization of live yeast (Saccharomyces cerevisiae, YE) in dairy cows is gaining traction in dairy production as a potential strategy to improve feed efficiency and milk yield. However, the effects of YE on dairy cow performance remain inconsistent across studies, leaving the underlying mechanisms unclear. Hence, the primary aim of this study was to investigate the impact of YE supplementation on lactation performance, ruminal microbiota composition and fermentation patterns, as well as serum antioxidant capacity and immune functions in dairy cows.

RESULTS

Supplementation with YE (20 g/d/head) resulted in enhancements in dairy cow's dry matter intake (DMI) (P = 0.016), as well as increased yields of milk (P = 0.002) and its components, including solids (P = 0.003), fat (P = 0.014), protein (P = 0.002), and lactose (P = 0.001) yields. The addition of YE led to significant increases in the concentrations of ammonia nitrogen (NH3-N) (P = 0.023), acetate (P = 0.005), propionate (P = 0.025), valerate (P = 0.003), and total volatile fatty acids (VFAs) (P < 0.001) in rumen fermentation parameters. The analysis of 16s rRNA gene sequencing data revealed that the administration of YE resulted in a rise in the relative abundances of three primary genera including Ruminococcus_2 (P = 0.010), Rikenellaceae_RC9_gut_group (P = 0.009), and Ruminococcaceae_NK4A214_group (P = 0.054) at the genus level. Furthermore, this increase was accompanied with an enriched pathway related to amino acid metabolism. Additionally, enhanced serum antioxidative (P < 0.05) and immune functionalities (P < 0.05) were also observed in the YE group.

CONCLUSIONS

In addition to improving milk performance, YE supplementation also induced changes in ruminal bacterial community composition and fermentation, while enhancing serum antioxidative and immunological responses during the mid-lactation stage. These findings suggest that YE may exert beneficial effects on both rumen and blood metabolism in mid-lactation dairy cows.

Molecular detection of ruminal micro-flora and micro-fauna in Saudi Arabian camels: Effects of season and region

This study investigated and explored the availability of micro-flora and micro-fauna in the ruminal contents of Arabian camel (Camelus dromedarius) from three different regions in Saudi Arabia along with two seasons. Samples were prepared and tested by conventional polymerase chain reaction (PCR). This study confirmed that the bacterial flora were dominating over other microbes. Different results of the availability of each microbe in each region and season were statistically analyzed and discussed. There was no significant effect of season on the micro-flora or micro-fauna however, the location revealed a positive effect with Ruminococcus flavefaciens (p < 0 0.03) in the eastern region. This study was the first to investigate the abundance of micro-flora and micro-fauna in the ruminal contents of camels of Saudi Arabia. This study underscores the significance of camel ruminal micro-flora and micro-fauna abundance, highlighting their correlation with both seasonality and geographic location. This exploration enhances our comprehension of camel rumination and digestion processes. The initial identification of these microbial communities serves as a foundational step, laying the groundwork for future in-depth investigations into camel digestibility and nutritional requirements.

Invited review: "Probiotic" approaches to improving dairy production: Reassessing "magic foo-foo dust"

The gastrointestinal microbial consortium in dairy cattle is critical to determining the energetic status of the dairy cow from birth through her final lactation. The ruminant's microbial community can degrade a wide variety of feedstuffs, which can affect growth, as well as production rate and efficiency on the farm, but can also affect food safety, animal health, and environmental impacts of dairy production. Gut microbial diversity and density are powerful tools that can be harnessed to benefit both producers and consumers. The incentives in the United States to develop Alternatives to Antibiotics for use in food-animal production have been largely driven by the Veterinary Feed Directive and have led to an increased use of probiotic approaches to alter the gastrointestinal microbial community composition, resulting in improved heifer growth, milk production and efficiency, and animal health. However, the efficacy of direct-fed microbials or probiotics in dairy cattle has been highly variable due to specific microbial ecological factors within the host gut and its native microflora. Interactions (both synergistic and antagonistic) between the microbial ecosystem and the host animal physiology (including epithelial cells, immune system, hormones, enzyme activities, and epigenetics) are critical to understanding why some probiotics work but others do not. Increasing availability of next-generation sequencing approaches provides novel insights into how probiotic approaches change the microbial community composition in the gut that can potentially affect animal health (e.g., diarrhea or scours, gut integrity, foodborne pathogens), as well as animal performance (e.g., growth, reproduction, productivity) and fermentation parameters (e.g., pH, short-chain fatty acids, methane production, and microbial profiles) of cattle. However, it remains clear that all direct-fed microbials are not created equal and their efficacy remains highly variable and dependent on stage of production and farm environment. Collectively, data have demonstrated that probiotic effects are not limited to the simple mechanisms that have been traditionally hypothesized, but instead are part of a complex cascade of microbial ecological and host animal physiological effects that ultimately impact dairy production and profitability.

Characteristic of the components and the metabolism mechanism of goat colostrum: a review

Colostrum contains large number of nutrients that promote the growth, differentiation, and biological functions for goat kids early somatic cells, which is crucial to meet the nutritional demands, immune function, and the health of goat kids later growth. Great attention has been given not only to nutritional ingredient differences between colostrum and normal milk, but also to function differences, and their effect on the physical and sensory properties of goat kid's growth performance and health status. This paper reviews the research progress of goat colostrum in recent years, mainly including the colostrum yield, components, i.e., proteins, lactose, and immunoglobulin, as well as the influence factor, i.e., number of lactation and littler size, nutrition during the gestation, and breeding environment. In addition, this review aims to summarize the synthesis and secretion mechanisms, and the digestion and absorption mechanism of goat colostrum. We conclude that even though the composition and physicochemical properties of goat colostrum are highly dynamic and variable, and the digestion and absorption mechanism has not been made fully clear until now, direct feed microbial (DFM) may be a promising alternative for improving the quality of colostrum that should be further explored for their practical usage.

Megasphaera elsdenii and Saccharomyces cerevisiae as direct fed microbials and their impact on ruminal microbiome during an acute acidosis challenge in continuous culture

Our objective was to evaluate the effects of combinations of Saccharomyces cerevisiae and Megasphaera elsdenii as direct-fed microbials (DFM) on ruminal microbiome during an acute acidosis challenge in a continuous culture system. Treatments provided a DFM dose of 1 × 108 colony-forming unit (CFU)/mL, as follows: control (no DFM), YM1 (S. cerevisiae and M. elsdenii strain 1), YM2 (S. cerevisiae and M. elsdenii strain 2), and YMM (S. cerevisiae and half of the doses of M. elsdenii strains 1 and 2). We conducted four experimental periods of 11 d, which consisted of non-acidotic days (1 to 8) and acidotic challenge days (9 to 11) to establish acute ruminal acidosis conditions with a common basal diet containing 12% neutral detergent fiber and 58% starch. Treatments were applied from days 8 to 11, and samples of liquid and solid-associated bacteria were collected on days 9 to 11. Overall, 128 samples were analyzed by amplification of the V4 region of bacterial 16S rRNA, and data were analyzed with R and SAS for alpha and beta diversity, taxa relative abundance, and correlation of taxa abundance with propionate molar proportion. We observed a lower bacterial diversity (Shannon index, P = 0.02) when YM1 was added to the diet in comparison to the three other treatments. Moreover, compared to control, addition of YM1 to the diet increased relative abundance of phylum Proteobacteria (P = 0.05) and family Succinivibrioceae (P = 0.05) in the solid fraction and tended to increase abundance of family Succinivibrioceae (P = 0.10) and genus Succinivibrio (P = 0.09) in the liquid fraction. Correlation analysis indicated a positive association between propionate molar proportion and relative abundance of Proteobacteria (r = 0.36, P = 0.04) and Succinivibrioceae (r = 0.36, P = 0.05) in the solid fraction. The inclusion of YM1 in high-grain diets with a high starch content resulted in greater abundance of bacteria involved in succinate synthesis which may have provided the substrate for the greater propionate synthesis observed.

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.

Microbial Fermented Liquid Supplementation Improves Nutrient Digestibility, Feed Intake, and Milk Production in Lactating Dairy Cows Fed Total Mixed Ration

The purpose of this experiment was to examine the effects of MFL supplementation on feed intake, nutrient digestibility, milk yield, and milk composition in early lactating dairy cows. Twelve, Thai crossbred Holstein Friesian cows in early lactation, 500 ± 30 kg of body weight (BW), were randomly assigned according to a completely randomized design (CRD). MFL supplementation levels of 0, 100, 200, and 300 mL/d were used as treatments. Experimental animals were fed a total mixed ration (TMR) with a roughage to concentrate ratio (R:C ratio) of 40:60, which contains 12% crude protein (CP) and 70% total digestible nutrient (TDN). Rice straw was a roughage source. MFL supplementation levels had no effect (p > 0.05) on body weight change and dry matter intake (DMI) expressed as %BW, whereas DMI expressed as metabolic body weight (BW^0.75) was linearly (p < 0.05) increased, with the highest at 200 mL/d in the YFL supplementation group (147.5 g/kg BW^0.75), whereas feed intake of organic matter (OM), CP, ether extract (EE), neutral detergent fiber (NDF) and acid detergent fiber (ADF) did not significant (p > 0.05) difference among treatments. Related to apparent digestibility, MFL levels did not affect (p > 0.05) on DM, OM, and EE digestibility, while apparent digestibility of CP, NDF, and ADF were linearly increased (p < 0.05) when increasing MFL supplementation levels, and the highest (p < 0.05) were the 200 and 300 mL/d FML supplemented groups. BUN at 0 h post feeding did not show a significant difference (p > 0.05) between treatments, while at 4 h after feeding, BUN was linearly (p < 0.05) increased from 0, 100, 200, and 300 (mL/day) MFL supplementation, the values were 12.9, 13.1, 19.7, and 18.4 mg/dL, respectively and the highest was 200 mL/head/day for the MFL supplemented group. MFL supplementation did not affect (p > 0.05) milk fat, lactose, solid not fat (SNF), and specific gravity of milk, while MFL supplementation at 200 mL/day caused a linear increase (p < 0.01) in BUN, MUN, milk yield, milk protein, total solids (TS) and 3.5% FCM when supplement levels were increased. In conclusion, MFL supplementation in early lactating dairy cows could improve feed 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.

Effects of Autolyzed Yeast Supplementation in a High-Starch Diet on Rumen Health, Apparent Digestibility, and Production Variables of Lactating Holstein Cows

Fifteen multiparous rumen-cannulated Holstein cows were assigned to one of five treatments in a replicated 5 × 5 Latin square design. The treatments were low-starch (LS) (22.8 ± 1% of dry matter; DM) without autolyzed yeast (AY; LS0, control), high-starch (HS) (31.2 ± 4% of DM) without AY (HS0), and HS with either 15 g (HS15), 30 g (HS30), or 45 g (HS45) of AY supplementation. Cows in HS0 had increased (p < 0.03) dry matter intake (DMI; 24.9 kg/d) and energy-corrected milk (ECM; 34.4 kg/d) compared to cows in LS0 (19.9 and 31.3 kg/d, respectively). There was a tendency for a quadratic treatment effect for feed efficiency (ECM/DMI, p = 0.07) and crude protein (CP) apparent digestibility (AD) (p = 0.09). Cows in HS45 tended (p = 0.09) to have increased DMI (25.6 kg/d) compared to cows in HS0 (24.9 kg/d). Cows in HS0 had greater (p < 0.04) milk protein nitrogen (N; 166 g/d) and microbial N production (161 g/d) than those in LS0 (140 and 138 g/d, respectively). In conclusion, the addition of AY tended to improve DMI, feed efficiency, and CP AD when cows were fed the HS diet.

Active Dry Yeast and Thiamine in Synergistic Mode Can Mitigate Adverse Effects of In Vitro Ruminal Acidosis Model of Goats

Ruminal acidosis is a type of metabolic disorder of high-yielding ruminants which is associated with the consumption of a high-grain diet. It not only harms the productive efficiency, health and wellbeing of the animals but also has detrimental effects on the economy of the farmers. Various strategies have been adapted to control ruminal acidosis. However, none of them have produced the desired results. This research was carried out to investigate the potential of active dry yeast (ADY) and thiamine in a synergistic mode to mitigate in vitro-induced ruminal acidosis. The purpose of this study was to determine how active dry yeast alone and in combination with thiamine affected the ruminal pH, lactate, volatile fatty acids, lipopolysaccharides (LPS) and microbial community in in vitro-induced ruminal acidosis. The experiment comprises three treatment groups, (1) SARA/control, (2) ADY and (3) ADYT (ADY + thiamine). In vitro batch fermentation was conducted for 24 h. The results indicated that ruminal induced successfully and both additives improved the final pH (p < 0.01) and decreased the LPS and lactate (p < 0.01) level as compared to the SARA group. However, the ADYT group decreased the level of lactate below 0.5 mmol/L. Concomitant to fermentation indicators, both the treatment groups decreased (p < 0.05) the abundance of lactate-producing bacteria while enhancing (p < 0.01) the abundance of lactate-utilizing bacteria. However, ADYT also increased (p < 0.05) the abundance of protozoa compared to the SARA and ADY group. Therefore, it can be concluded that ADY and thiamine in synergistic mode could be a better strategy in combating the adverse effects of subacute ruminal acidosis.

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.

Food systems at a watershed: Unlocking the benefits of technology and ecosystem symbioses

The current food systems require change to improve sustainability resilience. Humans need food and food requires natural resources which have been consistently reduced, destroyed, or eliminated during human development, and excessive during the last 50-70 years. Though essential, there has been less of a focus on the inter-relations and inter-dependences of our food supply with and on the world's eco-system and organisms. Integrating evidence for the importance of plants, the microbiota in plants, animals and humans and their reciprocal effects of their interactions on food systems is essential for creating more inclusive strategies for future food systems. This review examines the role of plants, microorganisms, plant-microbial, animal-microbial, and human-microbial interactions, their co-evolution on the food supply and human and eco-systems well-being. It also recognizes the contribution of indigenous knowledge for lasting protection of the land, managing resources and biodiversity and the usefulness of food processing for producing safe, tasty, and nutritious food sustainably. We demonstrate that new targets and priorities for harnessing science and technology for improving food and nutritional security and avoiding environmental degradation and biodiversity loss are urgently needed. For improved long-term sustainability, the benefits of technology and ecosystem interactions must be unlocked.

Performance and microbiota of the digestive tract of Nellore calves supplemented with fungi isolated from bovine rumen

Background and Aim

In tropical semiarid regions, supplementation with fungi could contribute to rumen modulation, promoting greater production of fibrolytic enzymes and degradation of forage. The objective of this study was to analyze the effect of supplementation with fungi, isolated from the bovine rumen, on the performance and microbiota of the digestive tract of Nellore calves.

Materials and Methods

The experiment was conducted in randomized blocks evaluating eight Nellore calves that were daily supplemented with isolates of Aspergillus terreus and Trichoderma longibrachiatum, along with eight calves that were not supplemented. After 55 days, the animals were weighed, and samples of rumen fluid and feces were collected for analysis. The characteristics that showed normal distribution were subjected to analysis of variance and compared using Tukey's test. Whereas, the variables that did not show normal distribution were subjected to the Kruskal-Wallis test, and the frequencies of the bacterial and fungal genera were compared using the Chi-square test.

Results

Supplementation with fungi promoted the reduction in ruminal pH (p<0.05). However, the final live weight; average daily weight gain; total weight gain; rumen protozoa; and the count of Enterobacteriaceae, mycelial fungi, and yeasts of ruminal fluid and feces were not influenced by supplementation (p>0.05). Moreover, the protozoa Eodinium spp. was identified only in supplemented calves (p<0.05).

Conclusion

Supplementation with the fungi presented the potential for use as possible additives because it did not alter the physiological parameters of the facultative anaerobic microbiota composition in the rumen and feces. In addition, it favored the presence of the ciliate genus Eodinium. However, further studies should be performed to better define suitable dosages for supplementation.

Poultry gut health - microbiome functions, environmental impacts, microbiome engineering and advancements in characterization technologies

The gastrointestinal tract (GIT) health impacts animal productivity. The poultry microbiome has functions which range from protection against pathogens and nutrients production, to host immune system maturation. Fluctuations in the microbiome have also been linked to prevailing environmental conditions. Healthy poultry birds possess a natural resistance to infection. However, the exploration of environmental impacts and other relevant factors on poultry growth and health have been underplayed. Since good performance and growth rate are central to animal production, the host-microbiome relationship remains integral. Prior to the emergence of metagenomic techniques, conventional methods for poultry microbiome studies were used and were low-throughput and associated with insufficient genomic data and high cost of sequencing. Fortunately, the advent of high-throughput sequencing platforms have circumvented some of these shortfalls and paved the way for increased studies on the poultry gut microbiome diversity and functions. Here, we give an up-to-date review on the impact of varied environments on microbiome profile, as well as microbiome engineering and microbiome technology advancements. It is hoped that this paper will provide invaluable information that could guide and inspire further studies on the lingering pertinent questions about the poultry microbiome.

Safety, environmental and technological characterization of beneficial autochthonous lactic bacteria, and their vaginal administration to pregnant cows for the design of homologous multi-strain probiotic formulas

In recent years, veterinary probiotic formulations constitute an interesting alternative to the use of antibiotics in animals for human consumption, but beneficial microorganisms must meet certain requirements to be included in these products. The objective of this work was to evaluate the safety and innocuity of beneficial autochthonous lactic bacteria (BALB) as well as to determine their beneficial, environmental, and technological characterization. Antibiotic resistance was assayed using phenotypic and genotypic methodology. A bovine vaginal fluid simulated medium (MSBVF) was designed where growth, pH changes, and expression of beneficial characteristics of lactic bacteria were evaluated; additionally, the optimal culture conditions in commercial media were determined in order to obtain the highest biomass production of the strains. Finally, the best strains were lyophilized and administered intravaginally to pregnant cows and their permanence in the vagina and adverse effects were evaluated. The results show that most of the strains were resistant to vancomycin, tetracycline, and streptomycin, with a high sensitivity to ampicillin, gentamicin, and clindamycin. The strains evaluated did not show gelatinase or hyaluronidase activity; however, 11 strains produced α-type hemolysis. The optimal growth of the microorganism was obtained in MRS broth, under slight agitation and without pH control. The strains grown in the MSBVF grew well and maintained the probiotic properties. Animals treated with probiotics bacteria did not show systemic or local inflammation. These strains can be included in a probiotic veterinary product to be applied to different bovine mucosa.

Implication and challenges of direct-fed microbial supplementation to improve ruminant production and health

Direct-fed microbials (DFMs) are feed additives containing live naturally existing microbes that can benefit animals' health and production performance. Due to the banned or strictly limited prophylactic and growth promoting usage of antibiotics, DFMs have been considered as one of antimicrobial alternatives in livestock industry. Microorganisms used as DFMs for ruminants usually consist of bacteria including lactic acid producing bacteria, lactic acid utilizing bacteria and other bacterial groups, and fungi containing Saccharomyces and Aspergillus. To date, the available DFMs for ruminants have been largely based on their effects on improving the feed efficiency and ruminant productivity through enhancing the rumen function such as stabilizing ruminal pH, promoting ruminal fermentation and feed digestion. Recent research has shown emerging evidence that the DFMs may improve performance and health in young ruminants, however, these positive outcomes were not consistent among studies and the modes of action have not been clearly defined. This review summarizes the DFM studies conducted in ruminants in the last decade, aiming to provide the new knowledge on DFM supplementation strategies for various ruminant production stages, and to identify what are the potential barriers and challenges for current ruminant industry to adopt the DFMs. Overall literature research indicates that DFMs have the potential to mitigate ruminal acidosis, improve immune response and gut health, increase productivity (growth and milk production), and reduce methane emissions or fecal shedding of pathogens. More research is needed to explore the mode of action of specific DFMs in the gut of ruminants, and the optimal supplementation strategies to promote the development and efficiency of DFM products for ruminants.

The impacts of a fibrolytic enzyme additive on digestibility and performance in the grower and early finisher period, and supplemental Saccharomyces cerevisiae on performance and rumen health in the late finisher period for feedlot cattle

Two experiments were conducted to determine the effects of a fibrolytic enzyme pretreatment on growth performance, apparent total tract digestibility, and ruminal pH throughout the grower and early finisher period (exp. 1), and to examine the impact of Saccharomyces cerevisiae supplementation on intake, performance, and indicators of gut health in the late finisher period (exp. 2). A total of 54 steers were randomly assigned to a subgroup determining experimental treatment groups. In exp. 1, steers were randomized to control (CON1; no enzyme) or enzyme [ENZ; 0.75 mL·kg−1 dry matter (DM) of feed] dietary treatments. Digestibility was improved (P ≤ 0.05) in ENZ steers for DM, crude protein, net energy for gain, and sugars but did not affect (P ≥ 0.12) dry matter intake (DMI), average daily gain (ADG), or reticulo-ruminal pH. In exp. 2, the treatments were control (CON2; no yeast) or yeast (YST; 3.0 g·animal−1 daily) supplemented diets. Rumen papillae were collected for mRNA expression of gut barrier function (OCLN, CLDN, ZO1, and ZO2) and immune response (TLR2, TLR4, and FCAR) genes and histological measurements. Yeast supplementation decreased (P < 0.001) DMI by 31%, reduced variation in DMI, and improved feed conversion ratios but did not impact rumen health mRNA expression or histology measures (P ≥ 0.07). Overall, enzyme supplementation improved the digestibility of some nutrients in the grower period, and yeast supplementation improved feed efficiency, without impacting growth performance or gut health.

Effects of peripartal yeast culture supplementation on lactation performance, blood biomarkers, rumen fermentation, and rumen bacteria species in dairy cows

Feeding yeast culture fermentation products has been associated with improved feed intake and milk yield in transition dairy cows. These improvements in performance have been further described in terms of rumen characteristics, metabolic profile, and immune response. The objective of this study was to evaluate the effects of a commercial yeast culture product (YC; Culture Classic HD, Phibro Animal Health) on performance, blood biomarkers, rumen fermentation, and rumen bacterial population in dairy cows from -30 to 50 d in milk (DIM). Forty Holstein dairy cows were enrolled in a randomized complete block design from -30 to 50 DIM and blocked according to expected calving day, parity, previous milk yield, and genetic merit. At -30 DIM, cows were assigned to either a basal diet plus 114 g/d of ground corn (control; n = 20) or a basal diet plus 100 g/d of ground corn and 14 g/d of YC (n = 20), fed as a top-dress. Cows received the same close-up diet from 30 d prepartum until calving [1.39 Mcal/kg of dry matter (DM) and 12.3% crude protein (CP)] and lactation diet from calving to 50 DIM (1.60 Mcal/kg of DM and 15.6% CP). Blood samples and rumen fluid were collected at various time points from -30 to 50 d relative to calving. Cows fed YC compared with control showed a trend for increased energy-corrected milk (+3.2 kg/d). Lower somatic cell counts were observed in YC cows than in control. We detected a treatment × time interaction in nonesterified fatty acids (NEFA) that could be attributed to a trend for greater NEFA in YC cows than control at 7 DIM, followed by lower NEFA in YC cows than control at 14 and 30 DIM. In the rumen, YC contributed to mild changes in rumen fermentation, mainly increasing postpartal valerate while decreasing prepartal isovalerate. This was accompanied by alterations in rumen microbiota, including a greater abundance of cellulolytic (Fibrobacter succinogenes) and lactate-utilizing bacteria (Megasphaera elsdenii). These results describe the potential benefits of supplementing yeast culture during the late pregnancy through early lactation, at least in terms of rumen environment and performance.

Influence of Yeast Products on Modulating Metabolism and Immunity in Cattle and Swine

Nutritional supplementation has been used by livestock producers for many years in order to increase animal performance, improve animal health, and reduce negative effects associated with enteric and/or respiratory pathogens. Supplements such as yeast and yeast-based products have broad applications across many livestock production systems, including poultry, aquaculture, cattle, and swine and have been shown to benefit animal production at various stages. These benefits include improvement in milk production, weight gain and feed conversion, as well as immune function. Initial research into the mode of action for these effects has focused on stimulation of the immune system by the β-glucan fractions of yeast. However, emerging studies have revealed that some of the beneficial effects of yeast products may stem from altering metabolism, including the availability of glucose and fatty acids. These changes in metabolism, and potentially energy availability, may partially explain differences in immune function observed in yeast-supplemented livestock, as the energy demands of an activated immune system are extremely high. Thus, this paper explores the influence of yeast products on metabolism in cattle and swine, and how changes in metabolism and energy availability may contribute to improvements in immune function in supplemented animals.

Sodium butyrate attenuated iE-DAP induced inflammatory response in the mammary glands of dairy goats fed high-concentrate diet

BACKGROUND

Long-term high-concentrate (HC) diet feeding increased bacterial endotoxins, which translocated into the mammary glands of dairy goats and induced inflammatory response. γ-d-Glutamyl-meso-diaminopimelic acid (iE-DAP), bacterial peptidoglycan component, triggered inflammatory response through activating nucleotide oligomerization domain protein 1 (NOD1) signaling pathway. While dietary supplemented with sodium butyrate (SB) relieved inflammatory response and improved animal health and production. To investigate the effects and the mechanisms of action of SB on the inflammatory response in the mammary glands of dairy goats fed HC diet, 12 Saanen dairy goats were randomly assigned into HC group and SB regulated (BHC) group.

RESULTS

The results showed that SB supplementation attenuated ruminal pH decrease caused by HC diet in dairy goats resulting in a decrease of proinflammatory cytokines and iE-DAP plasma concentration and the mRNA expression of NOD1 and other inflammation-related genes. The protein levels of NOD1, NF-κB p65 and NF-κB pp65 were decreased by the SB supplementation. The expression of histone deacetylase 3 (HDAC3) was also inhibited by the SB supplementation. Meanwhile, the chromatin compaction ratios and DNA methylation levels of NOD1 and receptor-interacting protein 2 (RIP2) of BHC group were upregulated.

CONCLUSION

Collectively, the SB supplementation mitigated the inflammatory response in the mammary glands of dairy goats during HC-induced subacute ruminal acidosis (SARA) by inhibiting the activation of the NOD1/NF-κB signaling pathway through the decrease of the iE-DAP concentration in the rumen fluid and plasma and HDAC3 expression. DNA methylation and chromatin remodeling also contributed to the anti-inflammatory effect of SB. © 2020 Society of Chemical Industry.

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the transition period on rumen fermentation of dairy cows fed fresh diets differing in starch content

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the transition period (d -28 ± 3 to 23 ± 3 relative to calving) on rumen fermentation and mRNA abundance of genes in the rumen epithelium of fresh cows (d 1 to 23 ± 3 after calving) fed diets differing in starch content. Eighteen ruminally cannulated multiparous Holstein cows were fed diets with SCFP (n = 9) or without (CON; n = 9) throughout the experiment. All cows were fed a common basal controlled-energy close-up diet (1.43 Mcal/kg, net energy for lactation; 13.8% starch) before calving. Cows within each treatment (CON or SCFP) were fed either a low-starch (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet during the fresh period. Cows were assigned to treatment after balancing for parity, body condition score, and expected calving date. Rumen pH was measured continuously for 72 h starting on d -10, -3, 1, 7, and 21 relative to calving date. Rumen papillae were collected on d -10 and 21 relative to calving. Supplementation of SCFP had no effect on rumen pH during d -10 to -8, but mean rumen pH tended to be higher (6.64 vs. 6.49) for SCFP cows than for CON cows during d -3 to -1. Feeding SCFP decreased the range of rumen pH variation compared with CON within the HS group during both d 7 to 9 (1.08 vs. 1.38) and d 21 to 23 (1.03 vs. 1.30) after calving. In addition, nadir rumen pH tended to be higher (5.64 vs. 5.44) and duration of pH below 5.8 tended to be shorter (116 vs. 323 min/d) for the SCFP group than for the CON group during d 21 to 23 after calving. Supplementation of SCFP increased the mRNA abundance of insulin-like growth factor-6 (1.10 vs. 0.69) before calving and decreased the mRNA abundance of putative anion transporter isoform 1 (1.12 vs. 2.27) after calving. Nadir rumen pH tended to be higher during d 1 to 3 (5.63 vs. 5.41) for LS cows than for HS cows, but rumen pH was not affected by dietary starch content during other time periods. Dietary starch content had no effect on mRNA abundance of genes in the rumen epithelium after calving. These results suggest that supplementation of SCFP may reduce the range of variation in rumen pH in fresh cows fed HS diets and the duration of subacute ruminal acidosis by the end of the fresh period regardless of dietary starch content and that decreasing dietary starch content during the fresh period may reduce the decrease in rumen pH immediately after parturition.

Potential roles of nitrate and live yeast culture in suppressing methane emission and influencing ruminal fermentation, digestibility, and milk production in lactating Jersey cows

Concern over the carbon footprint of the dairy industry has led to various dietary approaches to mitigate enteric CH₄ production. One approach is feeding the electron acceptor NO₃^-, thus outcompeting methanogens for aqueous H₂. We hypothesized that a live yeast culture (LYC; Saccharomyces cerevisiae from Yea-Sacc 1026, Alltech Inc., Nicholasville, KY) would stimulate the complete reduction of NO₃^- to NH₃ by selenomonads, thus decreasing the quantity of CH₄ emissions per unit of energy-corrected milk production while decreasing blood methemoglobin concentration resulting from the absorbed intermediate, NO₂^-. Twelve lactating Jersey cows (8 multiparous and noncannulated; 4 primiparous and ruminally cannulated) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Cattle were fed diets containing 1.5% NO₃^- (from calcium ammonium nitrate) or an isonitrogenous control diet (containing additional urea) and given a top-dress of ground corn without or with LYC, with the fourth week used for data collection. Noncannulated cows were spot measured for CH₄ emission by mouth using GreenFeed (C-Lock Inc., Rapid City, SD). The main effect of NO₃^- decreased CH₄ by 17% but decreased dry matter intake by 10% (from 19.8 to 17.8 kg/d) such that CH₄:dry matter intake numerically decreased by 8% and CH₄:milk net energy for lactation production was unaffected by treatment. Milk and milk fat production were not affected, but NO₃^- decreased milk protein from 758 to 689 g/d. Ruminal pH decreased more sharply after feeding for cows fed diets without NO₃^-. Acetate:propionate was greater for cows fed NO₃^-, particularly when combined with LYC (interaction effect). Blood methemoglobin was higher for cattle fed NO₃^- than for those fed the control diet but was low for both treatments (1.5 vs. 0.5%, respectively; only one measurement exceeded 5%), indicating minimal risk for NO₂^- accumulation at our feeding level of NO₃^-. Although neither apparent organic matter nor neutral detergent fiber digestibilities were affected, apparent N digestibility had an interaction for NO₃^- × LYC such that apparent N digestibility was numerically lowest for diets containing both NO₃^- and LYC compared with the other 3 diets. Under the conditions of this study, NO₃^- mitigated ruminal methanogenesis but also depressed dry matter intake and milk protein yield. Based on the fact that few interactions were detected, LYC had a minimal role in attenuating negative cow responses to NO₃^- supplementation.

Effects of active dried Saccharomyces cerevisiae on ruminal fermentation and bacterial community during the short-term ruminal acidosis challenge model in Holstein calves

We investigated the effects of active dried Saccharomyces cerevisiae (ADSC) on ruminal pH, fermentation, and the fluid bacterial community during the short-term ruminal acidosis challenge. Five rumen-fistulated male Holstein calves (147.0 ± 5.8 kg of body weight; 3.6 ± 0.2 mo of age) were used in a crossover design, and 0 g (control group, n = 5) or 2 g (SC group, n = 5) of ADSC (1 × 10¹⁰ cfu/g) was administered twice daily for 21 consecutive days. Calves were fed a high-forage diet during the first 15 d (d -14 to d 0; prechallenge), a high-grain diet for 2 d (d 1 and 2; ruminal acidosis challenge), and a high-forage diet for 4 d (d 3 to 6; postchallenge). Ruminal pH was measured continuously. Rumen fluid samples were collected once daily (0800 h) on d 0, 3, 4, and 6 and twice daily (0800 and 1100 h) on d 1 and 2. Bacterial DNA was extracted from fluid samples collected on d 0 and 3. The 24-h and 1-h mean ruminal pH was significantly depressed during the ruminal acidosis challenge in each group, although the changes were more severe in the SC group, consistent with a significant increase in lactic acid on d 2 (1100 h) compared with d 0 and a significantly higher proportion of butyric acid on d 2 (1100 h) compared with the control group. Feeding a high-grain diet caused a decrease in bacterial diversity due to high acidity in both groups. The relative abundances of the genus Bifidobacterium and operational taxonomic unit (OTU) 3 (Bifidobacterium species) increased significantly in both groups but were higher in the SC group. Correlation analyses indicated that OTU3 (Bifidobacterium species) were positively correlated with lactic acid concentration and that OTU1 (Prevotella species) and OTU5 (Succinivibrio species) were correlated with the proportion of butyric acid. These results suggest that ADSC supplementation induced the intense decreases in ruminal pH by increased butyric and lactic acid production through a high-grain diet fermentation by rumen fluid bacterial species during the short-term ruminal acidosis challenge in Holstein calves after weaning.

Engineering the microbiome for animal health and conservation

IMPACT STATEMENT

Considering the clear effects of microbiota on important aspects of animal biology and development (including in humans), this topic is timely and broadly appealing, as it compels us to consider the possibilities of altering the microbiome (without antibiotics) to positively affect animal health. In this review, we highlight three general approaches to manipulating the microbiome that have demonstrated success and promise for use in animal health. We also point out knowledge gaps where further inquiry would most benefit the field. Our paper not only provides a short and digestible overview of the current state of application, but also calls for further exploration of the microbial diversity at hand to expand our toolkit, while also leveraging the diversity and flexibility of animal systems to better understand mechanisms of efficacy.

Symposium review: Technologies for improving fiber utilization

The forage lignocellulosic complex is one of the greatest limitations to utilization of the nutrients and energy in fiber. Consequently, several technologies have been developed to increase forage fiber utilization by dairy cows. Physical or mechanical processing techniques reduce forage particle size and gut fill and thereby increase intake. Such techniques increase the surface area for microbial colonization and may increase fiber utilization. Genetic technologies such as brown midrib mutants (BMR) with less lignin have been among the most repeatable and practical strategies to increase fiber utilization. Newer BMR corn hybrids are better yielding than the early hybrids and recent brachytic dwarf BMR sorghum hybrids avoid lodging problems of early hybrids. Several alkalis have been effective at increasing fiber digestibility. Among these, ammoniation has the added benefit of increasing the nitrogen concentration of the forage. However, few of these have been widely adopted due to the cost and the caustic nature of the chemicals. Urea treatment is more benign but requires sufficient urease and moisture for efficacy. Ammonia-fiber expansion technology uses high temperature, moisture, and pressure to degrade lignocellulose to a greater extent than ammoniation alone, but it occurs in reactors and is therefore not currently usable on farms. Biological technologies for increasing fiber utilization such as application of exogenous fibrolytic enzymes, live yeasts, and yeast culture have had equivocal effects on forage fiber digestion in individual studies, but recent meta-analyses indicate that their overall effects are positive. Nonhydrolytic expansin-like proteins act in synergy with fibrolytic enzymes to increase fiber digestion beyond that achieved by the enzyme alone due to their ability to expand cellulose microfibrils allowing greater enzyme penetration of the cell wall matrix. White-rot fungi are perhaps the biological agents with the greatest potential for lignocellulose deconstruction, but they require aerobic conditions and several strains degrade easily digestible carbohydrates. Less ruminant nutrition research has been conducted on brown rot fungi that deconstruct lignocellulose by generating highly destructive hydroxyl radicals via the Fenton reaction. More research is needed to increase the repeatability, efficacy, cost effectiveness, and on-farm applicability of technologies for increasing fiber utilization.

Nutritional Interventions Improved Rumen Functions and Promoted Compensatory Growth of Growth-Retarded Yaks as Revealed by Integrated Transcripts and Microbiome Analyses

Growth retardation reduces the incomes of livestock farming. However, effective nutritional interventions to promote compensatory growth and the mechanisms involving digestive tract microbiomes and transcripts have yet to be elucidated. In this study, Qinghai plateau yaks, which frequently suffer from growth retardation due to malnutrition, were used as an experimental model. Young growth-retarded yaks were pastured (GRP), fed basal ration (GRB), fed basal ration addition cysteamine hydrochloride (CSH; GRBC) or active dry yeast (ADY; GRBY). Another group of growth normal yak was pastured as a positive control (GNP). After 60-day nutritional interventions, the results showed that the average daily gain (ADG) of GRB was similar to the level of GNP, and the growth rates of GRBC and GRBY were significantly higher than the level of GNP (P < 0.05). Basal rations addition of CSH or ADY either improved the serum biochemical indexes, decreased serum LPS concentration, facilitated ruminal epithelium development and volatile fatty acids (VFA) fermentation of growth-retarded yaks. Comparative transcriptome in rumen epithelium between growth-retarded and normal yaks identified the differentially expressed genes mainly enriched in immune system, digestive system, extracellular matrix and cell adhesion pathways. CSH addition and ADY addition in basal rations upregulated ruminal VFA absorption (SLC26A3, PAT1, MCT1) and cell junction (CLDN1, CDH1, OCLN) gene expression, and downregulated complement system (C2, C7) gene expression in the growth-retarded yaks. 16S rDNA results showed that CSH addition and ADY addition in basal rations increased the rumen beneficial bacterial populations (Prevotella_1, Butyrivibrio_2, Fibrobacter) of growth-retarded yaks. The correlation analysis identified that ruminal VFAs and beneficial bacteria abundance were significantly positively correlated with cell junction and VFA absorption gene expressions and negatively correlated with complement system gene expressions on the ruminal epithelium. Therefore, CSH addition and ADY addition in basal rations promoted rumen health and body growth of growth-retarded yaks, of which basal ration addition of ADY had the optimal growth-promoting effects. These results suggested that improving nutrition and probiotics addition is a more effective method to improve growth retardation caused by gastrointestinal function deficiencies.

Metagenome sequencing to analyze the impacts of thiamine supplementation on ruminal fungi in dairy cows fed high-concentrate diets

Ruminal thiamine deficiencies occur when dairy cows are overfed with high-concentrate diet, and thiamine supplementation has been proved to attenuate high-concentrate diet induced SARA. However, there is limited knowledge of the relationship between thiamine supplementation in high-concentrate diets and ruminal fungi. In order to investigate the impacts of thiamine supplementation on ruminal fungi, twelve Chinese Holstein dairy cows were randomly assigned into three treatments: control diet (CON; 20% starch, dry matter basis), high-concentrate diet (HC; 33.2% starch, dry matter basis) and high-concentrate diet supplemented with 180 mg thiamine/kg dry matter intake. Dry matter intake and milk production were recorded during the experimental periods. On day 21, rumen fluid samples were collected at 3 h postfeeding and ruminal pH, thiamine concentration and volatile fatty acids were measured. Metagenome sequencing method was conducted to detect ruminal fungi composition. Feeding HC significantly decreased dry matter intake, milk production, ruminal pH, ruminal acetate and thiamine concentration, however, significantly increased propionate and isovalerate (P < 0.05). These changes were inversed by thiamine supplementation (P < 0.05). Totally, seven phyla and almost 1050 species of rumen fungi were identified across all samples in which especially, 3 genera and 10 species of strictly anaerobic fungi phylum Neocallimastigomycota was found. Principal coordinate analysis indicated that feeding HC and thiamine supplementation caused a significant inverse in ruminal fungi composition. Feeding HC significantly decreased the abundance of fungi compared with CON (P < 0.05) while thiamine supplementation significantly increased the abundance of ruminal fungi (P < 0.05). These results indicated that thiamine supplementation may effectively attenuate rumen metabolic disorder caused by HC diet through buffering the ruminal pH, shifting the rumen fermentation pattern and increasing the abundance of ruminal fungi. The findings in this study could therefore contribute to the further understanding of the mechanism of thiamine's function in dairy cows.

Effects of live yeast dietary supplementation on hormonal profile, ovarian follicular dynamics, and reproductive performance in dairy cows exposed to high ambient temperature

Two experiments were conducted to investigate the effects of dietary supplementation with live yeast culture on hormonal profile, ovarian follicular dynamics and reproductive performance of lactating dairy cows exposed to high ambient temperature. In Expt. 1, Holstein cows were fed a diet with (n = 6) or without (n = 6) 4 g yeast/h/d from 21 d before expected calving date until 8 weeks postpartum. Concentrations of glucose, insulin, insulin like growth factor-I (IGF-I), estradiol-17β (E-17β) and progesterone (P4) were determined in plasma, and transrectal ultrasonography was used to monitor ovarian follicular dynamics. In Expt. 2, 150 Holstein cows (75/dietary group) received same diets as Expt. 1 with the exception that diets were fed from d 1 to d 70 postpartum. The effect of dietary treatments on reproductive performance was examined. In Expt. 1, plasma IGF concentrations during dietary treatment were higher (P = 0.05) in cows fed diets supplemented with yeast. On d 60 postpartum, average plasma concentrations of glucose (48.3 vs. 41.0 mg/dL) and insulin (0.90 vs. 0.23 μU/mL), were also greater in cows fed diets supplemented with yeast compared to that in cow fed diets without supplementation. Similarly, plasma concentrations of E-17β at estrus (P = 0.016) and P4 on d 10 of the estrous cycle (P = 0.021) were greater in yeast-supplemented cows. Moreover, yeast supplementation resulted on average in an estrous cycle 2.6 d shorter (P = 0.05) and in the development of larger ovulatory follicles (18.4 vs. 17.2 mm in diameter; P < 0.01). In Expt. 2, days open were fewer and the proportion of pregnant cows at 120 and 150 d postpartum were greater (P < 0.01) in cows fed diets supplemented with yeast compared to those receiving diets without yeast. In summary, cows fed diets supplemented with yeast had greater plasma IGF-I, E-17β and P4 concentrations, larger ovulatory follicles, shorter estrous cycles, and improved reproductive performance. Therefore, live yeast dietary supplementation could enhance lactating dairy cow's fertility during heat stress through improvement in hormonal profile and development of larger ovulatory follicles.

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.

The impact of direct-fed microbials and enzymes on the health and performance of dairy cows with emphasis on colostrum quality and serum immunoglobulin concentrations in calves

Thirty‐six cows were blocked by calving date and randomly assigned to one of three treatments. Cows were on treatments 3 weeks prepartum through 8 weeks post‐partum. Treatments were as follows: (i) no direct‐fed microbial (DFM) or cellulase and amylase enzymes (C), (ii) 45.4 g/day of DFM (D) or (iii) 45.4 g/day of DFM and 18.2 g/day of enzyme (DE). Total mixed ration fed and refused were measured daily to determine dry matter intake (DMI). Blood samples were taken three times weekly and analysed for β‐hydroxybutyrate, glucose and non‐esterified fatty acids. Body weight (BW) was measured weekly. Colostrum was weighed and analysed for IgA and IgG concentration. Calves were fed 4 L of colostrum within 2 hr of birth. Calf blood samples were taken at 0 and 24 hr for analysis of IgA and IgG concentrations and apparent efficiency of absorption. Milk yield was measured daily and samples collected weekly. Initial BW was different among treatments with D being lesser than C or DE treatments. Body weight, weight gain, efficiency of gain, DMI and blood parameters were unaffected. Treatment did not affect colostrum yield. Ash percentage of colostrum tended to increase with D and DE, while IgA and total solids yield decreased with D. Colostrum fat yield was decreased in D and DE. Treatments did not impact BW, serum IgA and IgG concentrations or apparent efficiency of absorption of calves. Post‐partum BW, DMI, blood parameters, milk production and composition were unaffected by treatment. However, cows on D gained more BW and tended to have greater efficiency of gain compared to those on DE, but were similar to C. Somatic cell scores were greatest for D. Results indicate that DFM and enzyme supplementation did not improve health and performance of dairy cattle during the pre‐ and post‐partum periods under conditions of this study.

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.

Illumina Sequencing Approach to Characterize Thiamine Metabolism Related Bacteria and the Impacts of Thiamine Supplementation on Ruminal Microbiota in Dairy Cows Fed High-Grain Diets

The requirements of thiamine in adult ruminants are mainly met by ruminal bacterial synthesis, and thiamine deficiencies will occur when dairy cows overfed with high grain diet. However, there is limited knowledge with regard to the ruminal thiamine synthesis bacteria, and whether thiamine deficiency is related to the altered bacterial community by high grain diet is still unclear. To explore thiamine synthesis bacteria and the response of ruminal microbiota to high grain feeding and thiamine supplementation, six rumen-cannulated Holstein cows were randomly assigned into a replicated 3 × 3 Latin square design trial. Three treatments were control diet (CON, 20% dietary starch, DM basis), high grain diet (HG, 33.2% dietary starch, DM basis) and high grain diet supplemented with 180 mg thiamine/kg DMI (HG+T). On day 21 of each period, rumen content samples were collected at 3 h postfeeding. Ruminal thiamine concentration was detected by high performance liquid chromatography. The microbiota composition was determined using Illumina MiSeq sequencing of 16S rRNA gene. Cows receiving thiamine supplementation had greater ruminal pH value, acetate and thiamine content in the rumen. Principal coordinate analysis and similarity analysis indicated that HG feeding and thiamine supplementation caused a strong shift in bacterial composition and structure in the rumen. At the genus level, compared with CON group, the relative abundances of 19 genera were significantly changed by HG feeding. Thiamine supplementation increased the abundance of cellulolytic bacteria including Bacteroides, Ruminococcus 1, Pyramidobacter, Succinivibrio, and Ruminobacter, and their increases enhanced the fiber degradation and ruminal acetate production in HG+T group. Christensenellaceae R7, Lachnospira, Succiniclasticum, and Ruminococcaceae NK4A214 exhibited a negative response to thiamine supplementation. Moreover, correlation analysis revealed that ruminal thiamine concentration was positively correlated with Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter. Taken together, we concluded that Bacteroides, Ruminococcus 1, Ruminobacter, Pyramidobacter, and Fibrobacter in rumen content may be associated with thiamine synthesis or thiamine is required for their growth and metabolism. In addition, thiamine supplementation can potentially improve rumen function, as indicated by greater numbers of cellulolytic bacteria within the rumen. These findings facilitate understanding of bacterial thiamine synthesis within rumen and thiamine's function in dairy cows.

Factors influencing ruminal bacterial community diversity and composition and microbial fibrolytic enzyme abundance in lactating dairy cows with a focus on the role of active dry yeast

The objective of the current study was to employ a DNA-based sequencing technology to study the effect of active dry yeast (ADY) supplementation, diet type, and sample location within the rumen on rumen bacterial community diversity and composition, and to use an RNA-based method to study the effect of ADY supplementation on rumen microbial metabolism during high-grain feeding (HG). Our previous report demonstrated that the supplementation of lactating dairy cows with ADY attenuated the effect of subacute ruminal acidosis. Therefore, we used samples from that study, where 16 multiparous, rumen-cannulated lactating Holstein cows were randomly assigned to 1 of 2 dietary treatments: ADY (Saccharomyces cerevisiae strain Y1242, 80 billion cfu/animal per day) or control (carrier only). Cows received a high-forage diet (77:23, forage:concentrate), then were abruptly switched to HG (49:51, forage:concentrate). Rumen bacterial community diversity and structure were highly influenced by diet and sampling location (fluid, solids, epimural). The transition to HG reduced bacterial diversity, but epimural bacteria maintained a greater diversity than fluid and solids. Analysis of molecular variance indicated a significant separation due to diet × sampling location, but not due to treatment. Across all samples, the analysis yielded 6,254 nonsingleton operational taxonomic units (OTU), which were classified into several phyla: mainly Firmicutes, Bacteroidetes, Fibrobacteres, Tenericutes, and Proteobacteria. High forage and solids were dominated by OTU from Fibrobacter, whereas HG and fluid were dominated by OTU from Prevotella. Epimural samples, however, were dominated in part by Campylobacter. Active dry yeast had no effect on bacterial community diversity or structure. The phylum SR1 was more abundant in all ADY samples regardless of diet or sampling location. Furthermore, on HG, OTU2 and OTU3 (both classified into Fibrobacter succinogenes) were more abundant with ADY in fluid and solids than control samples. This increase with ADY was paralleled by a reduction in prominent Prevotella OTU. Metatranscriptomic profiling of rumen microbiome conducted on random samples from the HG phase showed that ADY increased the abundance of the cellulase endo-β-1,4-glucanase and had a tendency to increase the hemicellulase α-glucuronidase. In conclusion, the shift from high forage to HG and sampling location had a more significant influence on ruminal bacterial community abundance and structure compared with ADY. However, evidence suggested that ADY can increase the abundance of some dominant anaerobic OTU belonging to F. succinogenes and phylum SR1. Further, microbial mRNA-based evidence suggested that ADY can increase the abundance of a specific microbial fibrolytic enzymes.

Live Yeast and Yeast Cell Wall Supplements Enhance Immune Function and Performance in Food-Producing Livestock: A Review (†,)(‡)

More livestock producers are seeking natural alternatives to antibiotics and antimicrobials, and searching for supplements to enhance growth performance, and general animal health and well-being. Some of the compounds currently being utilized and studied are live yeast and yeast-based products derived from the strain Saccharomyces cerevisiae. These products have been reported to have positive effects both directly and indirectly on the immune system and its subsequent biomarkers, thereby mitigating negative effects associated with stress and disease. These yeast-based products have also been reported to simultaneously enhance growth and performance by enhancing dry matter intake (DMI) and average daily gain (ADG) perhaps through the establishment of a healthy gastrointestinal tract. These products may be especially useful in times of potential stress such as during birth, weaning, early lactation, and during the receiving period at the feedlot. Overall, yeast supplements appear to possess the ability to improve animal health and metabolism while decreasing morbidity, thereby enhancing profitability of these animals.