Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants

The rumen is an integrated dynamic microbial ecosystem composed of enormous populations of bacteria, protozoa, fungi, archaea, and bacteriophages. These microbes ferment feed organic matter consumed by ruminants to produce beneficial products such as microbial biomass and short-chain fatty acids, which form the major metabolic fuels for ruminants. The fermentation process also involves inefficient end product formation for both host animals and the environment, such as ammonia, methane, and carbon dioxide production. In typical conditions of ruminal fermentation, microbiota does not produce an optimal mixture of enzymes to maximize plant cell wall degradation or synthesize maximum microbial protein. Well-functioning rumen can be achieved through microbial manipulation by alteration of rumen microbiome composition to enhance specific beneficial fermentation pathways while minimizing or altering inefficient fermentation pathways. Therefore, manipulating ruminal fermentation is useful to improve feed conversion efficiency, animal productivity, and product quality. Understanding rumen microbial diversity and dynamics is crucial to maximize animal production efficiency and mitigate the emission of greenhouse gases from ruminants. This chapter discusses genetic and nongenetic rumen manipulation methods to achieve better rumen microbial fermentation including improvement of fibrolytic activity, inhibition of methanogenesis, prevention of acidosis, and balancing rumen ammonia concentration for optimal microbial protein synthesis.

Toxin Degradation by Rumen Microorganisms: A Review

Animal feeds may contain exogenous compounds that can induce toxicity when ruminants ingest them. These toxins are secondary metabolites originating from various sources including plants, bacteria, algae and fungi. Animal feed toxins are responsible for various animal poisonings which negatively impact the livestock industry. Poisoning is more frequently reported in newly exposed, naïve ruminants while ‘experienced’ ruminants are observed to better tolerate toxin-contaminated feed. Ruminants can possess detoxification ability through rumen microorganisms with the rumen microbiome able to adapt to utilise toxic secondary metabolites. The ability of rumen microorganisms to metabolise these toxins has been used as a basis for the development of preventative probiotics to confer resistance against the poisoning to naïve ruminants. In this review, detoxification of various toxins, which include plant toxins, cyanobacteria toxins and plant-associated fungal mycotoxins, by rumen microorganisms is discussed. The review will include clinical studies of the animal poisoning caused by these toxins, the toxin mechanism of action, toxin degradation by rumen microorganisms, reported and hypothesised detoxification mechanisms and identified toxin metabolites with their toxicity compared to their parent toxin. This review highlights the commercial potential of rumen inoculum derived probiotics as viable means of improving ruminant health and production.

Targeting the Hindgut to Improve Health and Performance in Cattle

An adequate gastrointestinal barrier function is essential to preserve animal health and well-being. Suboptimal gut health results in the translocation of contents from the gastrointestinal lumen across the epithelium, inducing local and systemic inflammatory responses. Inflammation is characterized by high energetic and nutrient requirements, which diverts resources away from production. Further, barrier function defects and inflammation have been both associated with several metabolic diseases in dairy cattle and liver abscesses in feedlots. The gastrointestinal tract is sensitive to several factors intrinsic to the productive cycles of dairy and beef cattle. Among them, high grain diets, commonly fed to support lactation and growth, are potentially detrimental for rumen health due to their increased fermentability, representing the main risk factor for the development of acidosis. Furthermore, the increase in dietary starch associated with such rations frequently results in an increase in the bypass fraction reaching distal sections of the intestine. The effects of high grain diets in the hindgut are comparable to those in the rumen and, thus, hindgut acidosis likely plays a role in grain overload syndrome. However, the relative contribution of the hindgut to this syndrome remains unknown. Nutritional strategies designed to support hindgut health might represent an opportunity to sustain health and performance in bovines.

Top-dressing of chelated phytogenic feed additives in the diet of lactating Friesian cows to enhance feed utilization and lactational performance

The present experiment evaluated the inclusion of chelated phytogenic feed additives mixture in the diet of lactating cows for the first 3 months of lactation. A week before calving, thirty multiparous Friesian cows were divided into three treatments in a complete randomized design and fed a basal diet without supplementation (Control treatment), or the control diet supplemented with chelated phytogenic additives at 3 g (PHY3 treatment), or at 6 g/cow/d (PHY6 treatment). Menthol, levomenthol, β-linaloolm, anethole, hexadecanoic acid and pmenthane were the principal compounds identified in the additives mixture. Milk production, total solid, protein, fat, and lactose were increased with PHY3, but decreased by PHY6 (P<0.01). Whereas the PHY3 treatment increased (P<0.05) milk contents of Ca and Zn, PHY3 and PHY6 treatments increased (P<0.05) milk Fe and Mn concentrations. Though the PHY3 treatment increased (P<0.05) nutrient digestibility, the PHY6 treatment decreased (P<0.05) the digestibility of organic matter, crude protein and neutral detergent fiber. The PHY3 treatment increased (P<0.05) ruminal volatile fatty acids (VFA) concentration and proportional acetate and propionate and decreased butyrate, while the PHY6 treatment decreased ruminal VFA concentration and proportional acetate. The PHY3 treatment increased (P<0.05) serum total protein, glucose, total antioxidant capacity, and the concentrations of Ca and Zn. Both PHY3 and PHY6 treatment decreased (P<0.05) the concentrations of serum triglycerides, and cholesterol. Daily inclusion of 3 g/cow of chelated feed additives mixture in diet of lactating cows improved milk production and ruminal fermentation, but additives dose of 6 g/cow/d had negative impact on cows’ performance.

Dietary mitigation of enteric methane emissions from ruminants: A review of plant tannin mitigation options

Methane gas from livestock production activities is a significant source of greenhouse gas (GHG) emissions which have been shown to influence climate change. New technologies offer a potential to manipulate the rumen biome through genetic selection reducing CH4 production. Methane production may also be mitigated to varying degrees by various dietary intervention strategies. Strategies to reduce GHG emissions need to be developed which increase ruminant production efficiency whereas reducing production of CH4 from cattle, sheep, and goats. Methane emissions may be efficiently mitigated by manipulation of natural ruminal microbiota with various dietary interventions and animal production efficiency improved. Although some CH4 abatement strategies have shown efficacy in vivo, more research is required to make any of these approaches pertinent to modern animal production systems. The objective of this review is to explain how anti-methanogenic compounds (e.g., plant tannins) affect ruminal microbiota, reduce CH4 emission, and the effects on host responses. Thus, this review provides information relevant to understanding the impact of tannins on methanogenesis, which may provide a cost-effective means to reduce enteric CH4 production and the influence of ruminant animals on global GHG emissions.

Herbal feed additives containing essential oil: 1. Impact on the nutritional worth of complete feed in vitro

This study was taken up to assess the impact of supplementing herbal feed additives [HFAs; fruit of Myristica fragrans (Jayphall), seeds of Anethum sowa (Suva), fruit of Apium graveolens (Ajmo), fruit of Cuminum cyminum (Jeera), bark of Cinnamonum zeylanicum (Dalchini), or whole plant of Eclipta alba (Bhangro)] containing essential oils as active component on the nutrient utilization and methane production using wheat straw-based total mixed ration (TMR) as a substrate by in vitro gas production technique. The essential oil content was the highest (P < 0.01) in M. fragrans followed by E. alba and A. sowa. In addition to essential oils, these HFAs also contained saponins, tannins, and antioxidants. The HFAs were supplemented at 1-3% of substrate dry matter (DM). The data were analyzed by 6 × 4 factorial design. Irrespective of level of HFA, the net gas production (NGP) and metabolizable energy (ME) availability was the highest (P < 0.01) in TMR supplemented with C. zeylanicum comparable with E. alba, but higher than TMR supplemented with other HFAs. Supplementation of TMR with different HFAs did not affect the digestibility of neutral detergent fiber (NDF) and true organic matter (TOM) and partitioning factor (PF). The total volatile fatty acids (VFAs), acetate, propionate (P < 0.01), and butyrate (P < 0.05) production was the highest in TMR supplemented with A. sowa, and the lowest was observed in TMR supplemented with C. cyminum. The isobutyrate and valerate production was also the highest (P < 0.01) in diet supplemented with A. sowa, but isovalerate production was the highest (P < 0.01) in diet supplemented with C. zeylanicum. The A:P ratio was the best in TMR supplemented with A. sowa. The efficiency of rumen fermentation was the highest, and efficiency of conversion of hexose to methane was the lowest in diet supplemented with A. sowa as compared to all other supplements. The in vitro methane production expressed as either percent of NGP, ml/100 mg DM of substrate/24 h, or as ml/100 mg of digestible OM/24 h was the lowest in TMR supplemented with A. sowa. The ammonia nitrogen production from TMR supplemented with M. fragrans and A. sowa was comparable, but significantly (P < 0.01) lower than TMR supplemented with other HFAs. Irrespective of the nature of HFA, the NGP and ME availability were significantly (P < 0.01) higher in TMR supplemented with HFAs at all levels as compared to un-supplemented TMR. As compared to control, the digestibility of NDF and that of TOM was depressed slightly in all the HFA-supplemented TMRs. The supplementation of HFAs at 2% of substrate DM improved (P < 0.01) the production of total VFAs, acetate, and propionate, and that of isovalerate in comparison to the un-supplemented TMR. The acetate to propionate ratio increased (P < 0.01) with the increase in the level of supplementation of HFAs containing essential oils. The methane and ammonia productions were depressed significantly when TMR was supplemented at 2% level of HFAs as compared to control TMR. It was concluded that supplementation of TMR with A. sowa at 2% of substrate was fermented better as indicated by the production of total and individual VFA, methane, and ammonia as compared to TMR supplemented with other HFA or un-supplemented TMR.

Synergetic action between the rumen microbiota and bovine health

Host-rumen-microbe interactions are essential components of many physiological processes, and therefore can affect ruminant health. Classical knowledge of rumen microbiology is based on culture-dependent methodologies, which only account for 10-20% of the rumen bacterial communities. While, the advancement in DNA sequencing and bioinformatics platforms provide novel approaches to investigate the composition and dynamics of the rumen microbiota. Recent studies demonstrated that the ruminal ecosystem is highly diverse and harbors numerous microbial communities. The composition of these microbial communities are affected by various environmental factors such as nutrition and different management strategies. Disturbance in the microbial ecology of the rumen is associated with the development of various diseases. Despite the flow of recent rumen-based studies, rumen microbiota is still not fully characterized. This review provides an overview of recent efforts to characterize rumen microbiota and its potential role in rumen health and disease. Moreover, the recent effects of dietary interventions and probiotics on rumen microbiota are discussed.

Short communication: Signs of host genetic regulation in the microbiome composition in 2 dairy breeds: Holstein and Brown Swiss

This study aimed to evaluate whether the host genotype exerts any genetic control on the microbiome composition of the rumen in cattle. Microbial DNA was extracted from 18 samples of ruminal content from 2 breeds (Holstein and Brown Swiss). Reads were processed using mothur (https://www.mothur.org/) in 16S and 18S rRNA gene-based analyses. Then, reads were classified at the genus clade, resulting in 3,579 operational taxonomic units (OTU) aligned against the 16S database and 184 OTU aligned against the 18S database. After filtering on relative abundance (>0.1%) and penetrance (95%), 25 OTU were selected for the analyses (17 bacteria, 1 archaea, and 7 ciliates). Association with the genetic background of the host animal based on the principal components of a genomic relationship matrix based on single nucleotide polymorphism markers was analyzed using Bayesian methods. Fifty percent of the bacteria and archaea genera were associated with the host genetic background, including Butyrivibrio, Prevotella, Paraprevotella, and Methanobrevibacter as main genera. Forty-three percent of the ciliates analyzed were also associated with the genetic background of the host. In total, 48% of microbes were associated with the host genetic background. The results in this study support the hypothesis and provide some evidence that there exists a host genetic component in cattle that can partially regulate the composition of the microbiome.

Effect of high and low roughage total mixed ration diets on rumen metabolites and enzymatic profiles in crossbred cattle and buffaloes

Aim::

A comparative study was conducted on crossbred cattle and buffaloes to investigate the effect of feeding high and low roughage total mixed ration (TMR) diets on rumen metabolites and enzymatic profiles.

Materials and Methods::

Three rumen-fistulated crossbred cattle and buffalo were randomly assigned as per 3×3 switch over design for 21-days. Three TMR diets consisting of concentrate mixture, wheat straw and green maize fodder in the ratios of (T₁) 60:20:20, (T₂) 40:30:30, and (T₃) 20:40:40, respectively, were fed to the animals ad libitum. Rumen liquor samples were collected at 0, 2, 4, 6, and 8 h post feeding for the estimation of rumen biochemical parameters on 2 consecutive days in each trial.

Results::

The lactic acid concentration and pH value were comparable in both species and treatments. Feed intake (99.77±2.51 g/kg body weight), ruminal ammonia nitrogen, and total nitrogen were significantly (p<0.05) higher in buffalo and in treatment group fed with high concentrate diet. Production of total volatile fatty acids (VFAs) was non-significant (p>0.05) among treatments and significantly (p<0.05) greater in crossbred cattle than buffaloes. Molar proportions of individual VFAs propionate (C3), propionate:butyrate (C3:C4), and (acetate+butyrate):propionate ([C2+C4]:C3) ratio in both crossbred cattle and buffalo were not affected by high or low roughage diet, but percentage of acetate and butyrate varied significantly (p<0.05) among treatment groups. Activities of microbial enzymes were comparable among species and different treatment groups. A total number of rumen protozoa were significantly (p<0.05) higher in crossbred cattle than buffaloes along with significantly (p<0.05) higher population in animal fed with high concentrate diet (T₁).

Conclusion::

Rumen microbial population and fermentation depend on constituents of the treatment diet. However, microbial enzyme activity remains similar among species and different treatments. High concentrate diet increases number of rumen protozoa, and the number is higher in crossbred cattle than buffaloes.