Ruminal microbiota composition associated with ruminal fermentation parameters and milk yield in lactating buffalo in Guangxi, China-A preliminary study

Comparative assessment of emulsifiers for in vitro ruminal gas production and fermentation measurements: Tween 80 is a suitable emulsifier

Emulsifiers are essential for achieving a homogenous distribution of lipophilic supplements in in vitro rumen fluid incubations. Since emulsifiers can alter rumen fermentation, it is crucial to select one that minimally impacts fermentation parameters to reduce potential biases. This study aimed to evaluate seven emulsifiers' impact on in vitro ruminal fermentation using the Hohenheim Gas Test in order to identify the most inert emulsifier. Rumen fluids were collected from three non-lactating Original Brown-Swiss cannulated cows before morning feeding and incubated for 24 h with a basal diet in triplicates. The emulsifiers tested were ethanol, ethyl acetate, propylene glycol, glycerol, ethylene glycol, soy lecithin, and Tween® 80, each in two dosages (0.5% or 1% v/v). The untreated basal diet served as control. Compared to control, in vitro organic matter digestibility was enhanced by ethyl acetate (by 36.9 and 48.2%), ethylene glycol (by 20.6 and 20.1%), glycerol (by 46.9 and 56.8%) and soy lecithin (by 19.7 and 26.8%) at 0.5 and 1% dosage, respectively. Additionally, the 24-h methane production increased for ethanol (by 41.9 and 46.2%), ethylene glycol (by 50.5 and 51.5%), and glycerol (by 63.1 and 65.4%) for the 0.5 and 1% dosage, respectively, and 0.5% dosage for ethyl acetate (by 31.6%). The acetate molar proportion was 17.2%pt higher for ethyl acetate, and 25.5%pt lower for glycerol at 1% dosage, compared to the control. The propionate concentration was 22.1%pt higher 1% glycerol, and 15.2%pt and 15.1%pt higher for 0.5 and 1% propylene glycol, respectively, compared to the control. In summary, Tween® 80 did not significantly affect in vitro rumen fermentation parameters, making it the most suitable choice for in vitro incubations involving lipophilic substances in rumen fluid. Ethanol may be considered as an alternative emulsifier if methane production is not the variable of interest.

Rumen-protected lysine supplementation improved amino acid balance, nitrogen utilization and altered hindgut microbiota of dairy cows

This study was conducted to evaluate the effects of dietary crude protein (CP) and rumen-protected lysine (RPL) supplementation on lactation performance, amino acid (AA) balance, nitrogen (N) utilization and hindgut microbiota in dairy cows. Treatments were in a 2 × 2 factorial arrangement, and the main effects were CP concentration (16% vs. 18%) and RPL supplementation (with or without RPL at 40 g/cow per day). Forty cows were randomly allocated to 4 groups: low-CP diet (LP), low-CP diet plus RPL (LPL), high-CP diet (HP), high-CP diet plus RPL (HPL). The experiment was conducted for 8 weeks. Results showed that RPL increased the dry matter intake (P < 0.01), milk protein yield (P = 0.04) and energy corrected milk (P = 0.04), and tended to increase milk fat yield (P = 0.06) and fat corrected milk (P = 0.05). Cows in the HP group tended to have higher milk urea N (P = 0.07). Plasma concentrations of Arg, Ile, Lys, Met, Pro, total essential AA and total nonessential AA were increased by RPL (P < 0.05). The total essential AA, total nonessential AA and most AA (except Ile, Phe, Gly and Pro) were increased in the HP group (P < 0.05). N excretion was increased in the HP group through an increase in urea N excretion (P < 0.01) and an upward trend in plasma urea N (P = 0.07). In addition, RPL tended to increase milk protein N secretion (P = 0.08), milk N (P = 0.07) and microbial protein synthesis (P = 0.06), and decreased plasma urea N (P < 0.001). In the hindgut, the bacterial community were different between the LP and LPL groups (P < 0.01). The probiotic abundances of Christensenellaceae_R-7_group and Acinetobacter were increased by RPL (P = 0.03 and 0.03, respectively). The pathogenic abundances of Clostridium_sensu_stricto_1 (P < 0.001) and Turicibacter (P < 0.01) were decreased by RPL. In conclusion, supplementing RPL with low dietary CP could balance AA supply and increase milk protein yield, resulting in an improvement in N utilization efficiency, and altered the composition of the hindgut microbiota to favor the lactation performance of dairy cows.

Relationship between rumen bacterial community and milk fat in dairy cows

Introduction

Milk fat is the most variable nutrient in milk, and recent studies have shown that rumen bacteria are closely related to milk fat. However, there is limited research on the relationship between rumen bacteria and milk fatty. Fatty acids (FAs) are an important component of milk fat and are associated with various potential benefits and risks to human health.

Methods

In this experiment, forty-five healthy Holstein dairy cows with alike physiological and productive conditions were selected from medium-sized dairy farms and raised under the same feeding and management conditions. The experimental period was two weeks. During the experiment, raw milk and rumen fluid were collected, and milk components were determined. In this study, 8 high milk fat percentage (HF) dairy cows and 8 low milk fat percentage (LF) dairy cows were selected for analysis.

Results

Results showed that the milk fat percentage in HF group was significantly greater than that of the dairy cows in the LF group. 16S rRNA gene sequencing showed that the rumen bacterial abundance of HF dairy cows was significantly higher than that in LF dairy cows; at the genus level, the bacterial abundances of Prevotellaceae_UCG-001, Candidatus_Saccharimonas, Prevotellaceae_UCG-003, Ruminococcus_1, Lachnospiraceae_XPB1014_group, Lachnospiraceae_AC2044_group, probable_genus_10 and U29-B03 in HF group were significantly higher than those in the LF group. Spearman rank correlation analysis indicated that milk fat percentage was positively related to Prevotellaceae_UCG-001, Candidatus_Saccharimonas, Prevotellaceae_UCG-003, Ruminococcus_1, Lachnospiraceae_XPB1014_group, Lachnospiraceae_AC2044_group, probable_genus_10 and U29-B03. Furthermore, Prevotellaceae_UCG-001 was positively related to C14:0 iso, C15:0 iso, C18:0, Ruminococcus_1 with C18:1 t9, Lachnospiraceae_AC2044_group with C18:1 t9 and C18:1 t11, U29-B03 with C15:0 iso.

Discussion

To sum up, rumen bacteria in dairy cows are related to the variation of milk fat, and some rumen bacteria have potential effects on the deposition of certain fatty acids in raw milk.

Effects of ensiling sugarcane tops with bacteria-enzyme inoculants on growth performance, nutrient digestibility, and the associated rumen microbiome in beef cattle

Major challenges when ensiling sugarcane tops include fermentation that results in high quantities of alcohol and decrease in nutrient digestibility due to the accumulation of fiber components. Increased efforts to apply bacteria-enzyme inoculants in silage have the potential to improve nutrient digestibility. This study aimed to evaluate the effects of ensiling sugarcane tops with bacteria-enzyme inoculants or mixed bacterial inoculants on growth performance, nutrient digestibility, and rumen microbiome in beef cattle. Chopped sugarcane tops were ensiled in plastic bags for 60 d after application of 1) no inoculant (control check, CK); 2) bacteria-enzyme inoculants containing Pediococcus acidilactici, Saccharomyces cerevisiae, cellulase, and xylanase (T1, viable colony-forming units of each bacterial strain ≥108 CFU/g; enzyme activity of each enzyme ≥200 U/g); or 3) mixed bacterial inoculants containing Lactobacillus plantarum, Bacillus subtilis, and Aspergillus oryzae (T2, viable colony-forming units of each bacterial strain ≥107 CFU/g). Silages were fed to eighteen Holstein bull calves (n = 6/treatment) weighing 163.83 ± 7.13 kg to determine intake in a 49-d experimental period. The results showed that beef cattle-fed T1 silage or T2 silage had a significantly higher (P < 0.05) average daily gain than those fed CK silage, but the difference in dry matter intake was not significant (P > 0.05). The apparent digestibility of crude protein (CP) and acid detergent fiber (ADF) were higher (P < 0.05) for beef cattle-fed T1 silage or T2 silage than for those fed CK silage. The rumen bacterial community of beef cattle-fed T1 silage or T2 silage had a tendency to increase (P > 0.05) abundance of Firmicutes and Rikenellaceae_RC9_gut_group than those fed CK silage. Rumen fungal communities of beef cattle-fed T1 or T2 silage had a tendency to increase (P > 0.05) abundance of Mortierellomycota and of Mortierella than those fed CK silage. Spearman's rank correlation coefficient showed that the apparent digestibility of ADF for beef cattle was positively correlated with unclassified_p_Ascomycota of the fungal genera (P < 0.05). Neocalimastigomycota of the fungal phyla was strongly positively correlated with the apparent digestibility of neutral detergent fiber (NDF) (P < 0.05). Ruminococcus was positively correlated with the apparent digestibility of CP (P < 0.05). It was concluded that both T1 and T2 improved the growth performance of beef cattle by improving the ruminal apparent digestibility of CP and ADF, and had no significant impact on major rumen microbial communities in beef cattle.

Prevotella: A Key Player in Ruminal Metabolism

Ruminants are foregut fermenters that have the remarkable ability of converting plant polymers that are indigestible to humans into assimilable comestibles like meat and milk, which are cornerstones of human nutrition. Ruminants establish a symbiotic relationship with their microbiome, and the latter is the workhorse of carbohydrate fermentation. On the other hand, during carbohydrate fermentation, synthesis of propionate sequesters H, thus reducing its availability for the ultimate production of methane (CH4) by methanogenic archaea. Biochemically, methane is the simplest alkane and represents a downturn in energetic efficiency in ruminants; environmentally, it constitutes a potent greenhouse gas that negatively affects climate change. Prevotella is a very versatile microbe capable of processing a wide range of proteins and polysaccharides, and one of its fermentation products is propionate, a trait that appears conspicuous in P. ruminicola strain 23. Since propionate, but not acetate or butyrate, constitutes an H sink, propionate-producing microbes have the potential to reduce methane production. Accordingly, numerous studies suggest that members of the genus Prevotella have the ability to divert the hydrogen flow in glycolysis away from methanogenesis and in favor of propionic acid production. Intended for a broad audience in microbiology, our review summarizes the biochemistry of carbohydrate fermentation and subsequently discusses the evidence supporting the essential role of Prevotella in lignocellulose processing and its association with reduced methane emissions. We hope this article will serve as an introduction to novice Prevotella researchers and as an update to others more conversant with the topic.

Effects of Barley Starch Level in Diet on Fermentation and Microflora in Rumen of Hu Sheep

This study aimed to explore the effects of different levels of barley starch instead of corn starch on the rumen fermentation and microflora when feeding a corn-based diet to Hu sheep. Thirty-two male Hu sheep equipped with permanent rumen fistulas were selected and fed in individual metabolic cages. All sheep were randomly divided into four groups (eight sheep in each group) and fed with four diets containing a similar starch content, but from different starch sources, including 100% of starch derived from corn (CS), 33% of starch derived from barley + 67% of starch derived from corn (33 BS), 67% of starch derived from barley + 33% of starch derived from corn (67 BS) and 100% of starch derived from barley (100 BS). The experimental period included a 14 d adaptation period and a 2 d continuous data collection period. The results showed that the molar proportions of acetate, isobutyrate, butyrate and isovalerate and the ratio of acetate to propionate in the 67 BS and 100 BS groups decreased compared with the CS and 33 BS groups (p < 0.001), while the molar proportions of propionate and valerate increased (p < 0.001). The combination of 33% barley starch and 67% corn starch in the diet improved the production of TVFAs (p = 0.007). The OTUs and Shannon indexes of the CS and 33 BS groups were higher than the 67 BS and 100 BS groups (p < 0.001), and the Chao1 and Ace indexes were higher than the 100 BS group (p < 0.05). In addition, the 33 BS group had increased the relative abundances of Bacteroidetes, Prevotella and Ruminococcus and the abundances of Fibrobacter succinogenes, Ruminococcus flavefaciens, Streptococcus bovis, Selenomonas ruminantium and Prevotella brevis relative to the CS group (p < 0.05). These results indicate that the substitution of 33% of the CS with BS did not change the rumen fermentation pattern relative to the CS group, and increased the richness and diversity of the rumen microbes in Hu sheep compared with other two starch substitute groups.

Ruminal bacterial community is associated with the variations of total milk solid content in Holstein lactating cows

Total milk solid (TMS) content directly reflects the quality of milk. Rumen bacteria ferment dietary components, the process of which generates the precursors for the synthesis of milk solid, therefore, the variation in rumen bacterial community could be associated with milk solid in dairy cows. In this study, 45 healthy mid-lactation Holstein dairy cows with the similar body weight, lactation stage, and milk yield were initially used for the selection of 10 cows with high TMS (HS) and 10 cows with low TMS (LS). All those animals were under the same feeding management, and the individual milk yield was recorded for 14 consecutive days before milk and rumen fluid were sampled. Rumen fluid was used to determine bacterial community by 16S rRNA gene sequencing technique. The HS cows had significantly greater feed intake and milk TMS, fat, protein content than LS cows (P < 0.05). Among the volatile fatty acids (VFA), propionic acid and valeric acid concentrations were significantly greater in HS cows than those in LS cows (P < 0.05). There was no significant difference in the concentrations of acetate, butyrate, isobutyrate, valerate, and the total VFA (P > 0.05), nor was the acetate-to-propionate ratio, pH value, ammonia nitrogen and microbial crude protein concentrations (P > 0.05). Significant differences in the relative abundances of some bacterial genera were found between HS and LS cows. Spearman’s rank correlation analysis revealed that TMS content was correlated positively with the abundances of Ruminococcaceae UCG-014, Ruminococcaceae NK4A214 group, Prevotellaceae UCG-001, Butyrivibrio 2, Prevotellaceae UCG-003, Candidatus Saccharimonas, Ruminococcus 2, Lachnospiraceae XPB1014 group, probable genus 10, Eubacterium ventriosum group, but negatively correlated with Pyramidobacte. In addition, Ruminococcaceae UCG-014, Ruminococcus 2, Ruminococcaceae UCG001, probable genus 10 and Eubacterium ventriosum group might boost the total VFA production in the rumen. In conclusion, the dry matter intake of dairy cows and some special bacteria in rumen were significantly associated with TMS content, which suggests the potential function of rumen bacteria contributing to TMS content in dairy cows.

Effects of Broussonetia papyrifera silage on rumen fermentation parameters and microbes of Holstein heifers

The structure and types of rumen microbes are closely related to host health. This study aimed to evaluate the effect of Broussonetia papyrifera silage (BPS) gradually replacing the whole crop maize silage (WCMS) on total tract digestibility, rumen fermentation parameters, serum biochemical indicators, and rumen microbes of Holstein heifers. The diet treatment consisted of four proportions of BPS (0%, 25%, 50% and 75%) as substitute for WCMS (designated as T0, T25, T50 and T75, respectively). Twenty heifers (body weight = 245 ± 24 kg) were randomly divided into four groups of five heifers, and randomly received one diet. The feeding adaption period was 7 days, and the experiment period was 30 days. Our findings suggested that the digestibility of neutral detergent fiber and crude protein increased linearly with the increased in BPS (P < 0.05). The concentrations of total protein and albumin increased quadratically with the increased in BPS (P < 0.05). The 16s high-throughput sequencing showed that feeding BPS did not change the diversity and structure of the rumen microbes of heifers. However, the relative abundances of Tenericutes and SR1-Absconditabacteria increased linearly with the increased in BPS (P < 0.05). The Weighted Correlation Network Analysis results suggested that ALT concentration was positively correlated with the abundance of Prevotella-1 (r = 0.73; P = 0.007). In general, Holstein heifers fed with BPS did not change the diversity and uniformity of rumen microbes, and enhanced the body protein metabolism.

Effects of Dietary Supplementation of Bovine Lactoferricin on Rumen Microbiota, Lactation, and Health in Dairy Goats

This study aimed to investigate the biological effects of supplementation of bovine lactoferricin (BLFc) at the rate of 100 mg/kg/day (LF-1) or 200 mg/kg/day (LF-2) in lactating dairy goats. Dietary BLFc supplementation increased the concentration of lactoferrin (LF) in the milk and serum (p < 0.05) without affecting the feed intake. In the LF-1 group, serum Fe, total antioxidant (T-AOC), and immunoglobulin A (IgA) were increased (p < 0.05), while malondialdehyde (MDA) was decreased (p < 0.05). In the LF-2 group, ruminal fluid pH value was decreased (p < 0.05), and the composition of ruminal microflora on day 42 was more diversified. Firmicutes phylum in the LF-2 group was the most abundant phyla. In contrast, Bacteroidetes phylum in the control group and the LF-1 group were the most abundant. Lower milk somatic cell count and higher IgA were observed in the LF-1 group and the LF-2 group than those in the control group (p < 0.05). These results suggested beneficial effects of supplementation of 100 mg/kg/day BLFc on reducing the oxidative stress and altering diversity of ruminal microflora.

Microbiome and fermentation parameters in the rumen of dairy buffalo in response to ingestion associated with a diet supplemented with cysteamine and hemp seed oil

In this study, high-throughput gene amplicon sequencing was used to investigate the effects of 6 treatments [2 levels of hemp seed oil (HSO) × 3 levels of cysteamine (CS)] on bacterial and fungal communities in the rumen of 30 crossbred dairy buffalo. Our results indicate that the total numbers of bacterial and fungal taxa were unaffected regardless of diet (p > 0.05), while the total number of archaea was affected (p < 0.05) by the interaction of HSO and CS. Compared with control treatment, microbial composition of archaea was strongly influenced by CS (p < 0.05), while the addition of HSO, CS or both had a weak effect on fungus and bacteria. In addition, there was a significant increase in the lactic acid content with the addition of HSO, and the addition of CS to the feed caused a significant decrease in the ratio of acetic acid to propionic acid, compared with control treatment (p < 0.05). Correlation analysis showed that Acetobacter was significantly positively correlated with the genera Pichia, Klebsiella and Acinetobacter. pH was found to have a significant effect on the methanogens, and total volatile fatty acids (VFA) had a strong correlation with Butyrivibrio. The strong influence of CS on some methanogens shows that it may have potential in the development of methane reduction interventions.

Metagenomics analysis revealed the distinctive ruminal microbiome and resistive profiles in dairy buffaloes

BACKGROUND

Antimicrobial resistance poses super challenges in both human health and livestock production. Rumen microbiota is a large reservoir of antibiotic resistance genes (ARGs), which show significant varations in different host species and lifestyles. To compare the microbiome and resistome between dairy cows and dairy buffaloes, the microbial composition, functions and harbored ARGs of rumen microbiota were explored between 16 dairy cows (3.93 ± 1.34 years old) and 15 dairy buffaloes (4.80 ± 3.49 years old) using metagenomics.

RESULTS

Dairy buffaloes showed significantly different bacterial species (LDA > 3.5 & P < 0.01), enriched KEGG pathways and CAZymes encoded genes (FDR < 0.01 & Fold Change > 2) in the rumen compared with dairy cows. Distinct resistive profiles were identified between dairy cows and dairy buffaloes. Among the total 505 ARGs discovered in the resistome of dairy cows and dairy buffaloes, 18 ARGs conferring resistance to 16 antibiotic classes were uniquely detected in dairy buffaloes. Gene tcmA (resistance to tetracenomycin C) presented high prevalence and age effect in dairy buffaloes, and was also highly positively correlated with 93 co-expressed ARGs in the rumen (R = 0.98 & P = 5E-11). In addition, 44 bacterial species under Lactobacillus genus were found to be associated with tcmA (R > 0.95 & P < 0.001). L. amylovorus and L. acidophilus showed greatest potential of harboring tcmA based on co-occurrence analysis and tcmA-containing contigs taxonomic alignment.

CONCLUSIONS

The current study revealed distinctive microbiome and unique ARGs in dairy buffaloes compared to dairy cattle. Our results provide novel understanding on the microbiome and resistome of dairy buffaloes, the unique ARGs and associated bacteria will help develop strategies to prevent the transmission of ARGs.

Different Non-Structural Carbohydrates/Crude Proteins (NCS/CP) Ratios in Diet Shape the Gastrointestinal Microbiota of Water Buffalo

The microbiota of the gastrointestinal tract (GIT) are crucial for host health and production efficiency in ruminants. Its microbial composition can be influenced by several endogenous and exogenous factors. In the beef and dairy industry, the possibility to manipulate gut microbiota by diet and management can have important health and economic implications. The aims of this study were to characterize the different GIT site microbiota in water buffalo and evaluate the influence of diet on GIT microbiota in this animal species. We characterized and compared the microbiota of the rumen, large intestine and feces of water buffaloes fed two different diets with different non-structural carbohydrates/crude proteins (NSC/CP) ratios. Our results indicated that Bacteroidetes, Firmicutes and Proteobacteria were the most abundant phyla in all the GIT sites, with significant differences in microbiota composition between body sites both within and between groups. This result was particularly evident in the large intestine, where beta diversity analysis displayed clear clustering of samples depending on the diet. Moreover, we found a difference in diet digestibility linked to microbiota modification at the GIT level conditioned by NSC/CP levels. Diet strongly influences GIT microbiota and can therefore modulate specific GIT microorganisms able to affect the health status and performance efficiency of adult animals.

Consequences of herbal mixture supplementation on milk performance, ruminal fermentation, and bacterial diversity in water buffaloes

This study was aimed to evaluate the potential of a herbal mixture (HM) to improve production performance, rumen fermentation, and milk fatty acid profile in water buffaloes. Sixteen Murrah buffaloes (in four groups) were fed for 10 weeks with the same basal diet supplemented with 0 (control); 20 (HM20), 30 (HM30), and 40 (HM40) g/buffalo per day. The herbal mixture contained an equal quantity of black pepper (fruit), ginger (tubers), cinnamon (bark), peppermint (leaves), ajwain (seeds) and garlic (bulbs). After two weeks of adaptation, daily milk yield, and weekly milk composition were recorded. On the last day of the experiment, rumen contents were collected to determine rumen fermentation parameters and bacterial diversity through 16S rRNA sequencing. Results revealed no effect of treatment on dry matter intake (DMI), rumen fermentation parameters, and daily milk yield. However, milk fat (%) showed a tendency to increase (p = 0.07) in HM20 as compared with the control group. A significant increase in mono and polyunsaturated fatty acids (C14:1, C16:1, C18:2n6 and C18:3) whereas a decrease in saturated fatty acids (C18:0) in milk was observed in HM20 as compared with the control group. No significant change in bacterial diversity parameters (alpha and beta diversity) was observed in response to the treatment. Despite the substantial variation observed in the relative abundance of bacteria among treatment groups, no significant effect of treatment was observed when compared with the control group. Correlation analysis revealed several positive and negative correlations of rumen bacteria with rumen volatile fatty acids (VFA) and milk yield traits. Bacterial genera including Succinivibrionaceae, Butyrivibrio, Pseudobutyrivibrio, and Lachnospiraceae showed a positive correlation with VFA and milk yield traits. Overall, we observed 52 positive and 10 negative correlations of rumen bacteria with milk fatty acid contents. Our study revealed the potential of the herbal mixture at a lower supplemental level (20 g/day) to increase milk fat (%) and unsaturated fatty acid content in buffalo.

Lower methane emissions were associated with higher abundance of ruminal Prevotella in a cohort of Colombian buffalos

Background

Ruminants burp massive amounts of methane into the atmosphere and significantly contribute to the deposition of greenhouse gases and the consequent global warming. It is therefore urgent to devise strategies to mitigate ruminant’s methane emissions to alleviate climate change. Ruminal methanogenesis is accomplished by a series of methanogen archaea in the phylum Euryarchaeota, which piggyback into carbohydrate fermentation by utilizing residual hydrogen to produce methane. Abundance of methanogens, therefore, is expected to affect methane production. Furthermore, availability of hydrogen produced by cellulolytic bacteria acting upstream of methanogens is a rate-limiting factor for methane production. The aim of our study was to identify microbes associated with the production of methane which would constitute the basis for the design of mitigation strategies.

Results

Moderate differences in the abundance of methanogens were observed between groups. In addition, we present three lines of evidence suggesting an apparent higher abundance of a consortium of Prevotella species in animals with lower methane emissions. First, taxonomic classification revealed increased abundance of at least 29 species of Prevotella. Second, metagenome assembly identified increased abundance of Prevotella ruminicola and another species of Prevotella. Third, metabolic profiling of predicted proteins uncovered 25 enzymes with homology to Prevotella proteins more abundant in the low methane emissions group.

Conclusions

We propose that higher abundance of ruminal Prevotella increases the production of propionic acid and, in doing so, reduces the amount of hydrogen available for methanogenesis. However, further experimentation is required to ascertain the role of Prevotella on methane production and its potential to act as a methane production mitigator.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-020-02037-6.

A Mixed Phytogenic Modulates the Rumen Bacteria Composition and Milk Fatty Acid Profile of Water Buffaloes

This study was aimed to evaluate the effect of a mixed phytogenic (MP) on rumen bacteria and their potential association with rumen fermentation and milk yield parameters in water buffaloes. Twenty Murrah buffaloes were fed a basal diet (consisting of maize silage, brewers' grains, and concentrate mixture) for 6 weeks supplemented with 0 (control), 15 (MP15), 25 (MP25), and 35 (MP35) g of mixed phytogenic/buffalo per d. The mixed phytogenic contained fennel (seeds), ajwain (seeds), ginger (tubers), Swertia chirata (leaves), Citrullus colocynthis (fruit), turmeric, fenugreek (seeds), Terminalia chebula (fruit), licorice (roots), and Phyllanthus emblica (fruit) in equal quantities. After 2 weeks of adaptation, daily milk yield, and weekly milk composition were recorded. On the last day of the experiment (d 42), rumen contents were collected to determine rumen fermentation parameters and bacterial diversity through 16S rRNA sequencing. Results revealed no change in dry matter intake, milk yield and rumen fermentation parameters except pH, which increased (P = 0.029) in response to MP supplementation. The mixed phytogenic increased (P < 0.01) milk fatty acids (C4 to C14:0) in MP15 only. The milk C16:1 content and its unsaturation index were higher (P < 0.05) in MP35 as compared to the control and other treatments. Furthermore, C18:3n3 was higher (P < 0.05) in the control, MP15, and MP25, as compared to MP35. Supplementation of MP tended to increase (P = 0.095) the Shannon index of bacterial alpha diversity and a difference (P < 0.05) among treatment groups was observed in beta diversity. Feeding MP increased the Firmicutes, Proteobacteria, and Spirochaetes but decreased Bacteroidetes numerically. In addition, the dominant genus Prevotella decreased in all treatment groups while Pseudobutyrivibrio, Butyrivibrio, and Succinivibrioanceae increased numerically in MP25 and MP35. The mixed phytogenic promoted groups of rumen bacteria positively associated with milk and fat yield. Overall, our study revealed 14 positive correlations of rumen bacteria with milk yield and eight with rumen fermentation parameters. Our findings reveal substantial changes in the rumen bacteriome composition and milk fatty acid content in response to MP but these results should be interpreted carefully, as the sample size of our study was relatively small.