Microbial profiles, in vitro gas production and dry matter digestibility based on various ratios of roughage to concentrate

Animal board invited review: The effect of diet on rumen microbial composition in dairy cows

Ruminants play an important part in the food supply chain, and manipulating rumen microbiota is important to maximising ruminants' production. Rumen microbiota through rumen fermentation produces as major end products volatile fatty acids that provide animal's energy requirements, and microbial CP. Diet is a key factor that can manipulate rumen microbiota, and each variation of the physical and chemical composition creates a specific niche that selects specific microbes. Alteration in the chemical composition of forage, the addition of concentrates in the diet, or the inclusion of plant extract and probiotics, can induce a change in rumen microbiota. High-throughput sequencing technologies are the approaches utilised to investigate the microbial system. Also, the application of omics technologies allows us to understand rumen microbiota composition and these approaches are useful to improve selection programmes. The aim of this review was to summarise the knowledge about rumen microbiota, its role in nutrient metabolism, and how diet can influence its composition.

Efficacy of Salvia officinalis Shrub as a Sustainable Feed Additive for Reducing Ruminal Methane Production and Enhancing Fermentation in Ruminants

The objective of this study was to evaluate the effects of the inclusion of dried Salvia officinalis (SO) shrub leaves on nutrient degradability, ruminal in vitro fermentation, gas production (GP), methane (CH4), and carbon dioxide (CO2) productions. Dried and ground SO shrub leaves were included at 0% (control), 0.5%, 1%, 1.5%, and 2% DM of a diet consisting of (per kg DM) 500 g concentrate feed mixture, 400 g berseem hay, and 100 g rice straw. The diet was incubated for 48 h. The asymptotic GP and the rate of GP changed linearly and quadratically (p < 0.01), with the highest GP observed at 1% inclusion of SO and then decreasing thereafter with greater inclusion (i.e., 1.5% and 2%), while CH4 production and its rate decreased linearly (p < 0.01) with all levels of SO inclusion. A linear increase in CO2 production and its rate was also found with an increasing level of SO inclusion in the diet (p < 0.05). Furthermore, the degradability of DM, NDF, and the concentration of total short-chain fatty acids and acetate changed linearly and quadratically, with the greatest being found at 1% SO inclusion and then steadily declining after (p < 0.01) with the 1.5% and 2% inclusion levels. Meanwhile, the propionate, NH3-N, and microbial crude protein levels showed similar trends, with the plateau found at 1% inclusion of SO, where there was no change in butyrate concentration. Moreover, the pH, metabolizable energy, and partitioning factor (PF24) also changed linearly and quadratically (p < 0.05), where the pH and PF24 were considerably reduced and ME increased with a 1% inclusion of SO (p < 0.05). In summary, SO at 1% inclusion in the diet showed the potential to improve gas production kinetics, nutrient degradability, and the ruminal fermentation profile, with a more significant reduction in ruminal CH4 production suggesting that SO at 1% could be included in the ruminant diet to reduce their carbon footprint and increase the production performance.

Responses of nutrient utilization, rumen fermentation and microorganisms to different roughage of dairy buffaloes

Dairy buffaloes are typically fed a high-forage, low-quality diet with high fiber. These conditions result in an inherent energy and protein inefficiency. In order to make full and rational use of feed resources and improve the production level and breeding efficiency of dairy buffaloes, the effects of various roughages on nutrient digestibility, ruminal fermentation parameters, and microorganisms in dairy buffaloes were studied in this experiment. Three ternary hybrid buffaloes, with an average body weight of 365 ± 22.1 kg, were selected and fitted with permanent rumen fistulas. They were fed six different diets, each consisting of 1 kg concentrate supplement and one of six types of roughage, including alfalfa hay (A diet), oat hay (O diet), whole corn silage (W diet), king grass (K diet), sugarcane shoot silage (S diet), and rice straw hay (R diet) according to an incomplete Latin square design of 3 × 6, respectively. The pre-feeding period of each period was 12 d. From day 13 to 15 was the official experimental period. During the prefeeding period, free feed intake for each roughage was determined, and during the experiment, the roughage was fed at 90% of the voluntary feed intake. Digestion and metabolism tests were carried out using the total manure collection method to determine the feed intake and fecal output of each buffalo, and to collect feed and fecal samples for chemical analysis. On day 15, rumen fluid samples were collected two hours after morning feeding to determine rumen fermentation parameters and bacterial 16 S rRNA high-throughput sequencing was performed. The results showed that DM and OM digestibility were greatest for the W diet and lowest for the S diet. The rumen pH of the O diet was significantly greater than that of the W diet. The concentration of rumen fluid NH3-N (mg/dL) increased with increased CP content. The concentration of total volatile fatty acids (mmol/L) in the rumen decreased with increased NDF content but increased with increased NFC content. The relative abundances of Bacteroidetes, Firmicutes, and Spirochaetes were 57.03-74.84%, 14.29-21.86%, and 0.44-1.43% in the different quality roughage groups. Bacteroidetes were mainly Prevotellaceae1 and Rikenellaceae RC_gut_group with relative abundances of 30.17-45.75% and 3.23-7.82%. The relative abundance of Patescibacteria and Spirochaetes decreased with increasing roughage quality. These results provide a theoretical and practical basis for evaluating the nutritional value of dairy buffalo feed, utilizing feed resources, matching rations, feeding scientifically, and protecting animal health.

Drinking Heated Water Improves Performance via Increasing Nutrient Digestibility and Ruminal Fermentation Function in Yak Calves

This study was conducted to investigate the effects of heated water intake on the growth performance, serum biochemical indexes, apparent total tract digestibility (ATTD) of nutrients and ruminal fermentation function of yak calves in winter. A total of 24 yaks (59.09 ± 3.181 kg) were randomly selected and divided into a cold water (fluctuated with the temperature of test sites at 0-10 °C) group (CW) (58.58 ± 3.592 kg) and a heated water (20 °C) group (HW) (59.61 ± 2.772 kg). After 2 months of the experiment, body weight, serum biochemical indexes, ruminal fermentation characteristics and ATTD were measured. The results showed that drinking heated water increased (p < 0.05) the total weight gain and average daily gain of yaks compared with those drinking cold water. Heated water increased (p < 0.05) the levels of immune globulin M, interleukin-6, triiodothyronine, tetraiodothyronine and growth hormone compared with cold water. In addition, yaks drinking heated water showed higher (p < 0.05) ATTD of crude protein and ether extract, as well as increased (p < 0.05) content of total protein, albumin and urea nitrogen in serum than those drinking cold water. Compared with cold water, heated water showed increased (p < 0.05) total volatile fatty acids, acetic acid and propionic acid, and a reduced (p < 0.05) acetic acid to propionic acid ratio (p < 0.05). In conclusion, drinking heated water at 20 °C could improve performance via increasing nutrient digestibility and ruminal fermentation function in yak calves.

The Effect of Combining Millet and Corn Straw as Source Forage for Beef Cattle Diets on Ruminal Degradability and Fungal Community

Three ruminal cannulated Simmental crossbreed bulls (approximately 3 years of age and with 380 ± 20 kg live weight at initiation of the experiment) were used in a 3 × 3 Latin square experiment in order to determine the effects of the treatments on ruminal pH and degradability of nutrients, as well as the rumen fungal community. The experimental periods were 21 d, with 18 d of adjustment to the respective dietary treatments and 3 d of sample collection. Treatments consisted of a basal diet containing a 47.11% composition of two sources of forage as follows: (1) 100% millet straw (MILLSTR), (2) 50:50 millet straw and corn straw (COMB), and (3) 100% corn straw (CORNSTR). Dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), and acid detergent fiber (ADF) were tested for ruminal degradability using the nylon bag method, which was incubated for 6, 12, 24, 36, 48, and 72 h, and rumen fungal community in rumen fluid was determined by high-throughput gene sequencing technology. Ruminal pH was not affected by treatments. At 72 h, compared to MILLSTR, DM degradability of CORNSTR was 4.8% greater (p < 0.05), but when corn was combined with millet straw, the difference in DM degradability was 9.4%. During the first 24 h, degradability of CP was lower for CORNSTR, intermediate for MILLSTR, and higher for COMB. However, at 72 h, MILLSTR and COMB had a similar CP degradability value, staying greater than the CP degradability value of the CORNSTR treatment. Compared to MILLSTR, the rumen degradability of NDF was greater for CORNSTR and intermediate for the COMB. There was a greater degradability for ADF in CORNSTR, intermediate for COMB, and lower for MILLSTR. In all treatments, Ascomycota and Basidiomycota were dominant flora. Abundance of Basidiomycota in the group COMB was higher (p < 0.05) than that in the group CORNSTR at 12 h. Relative to the fungal genus level, the Thelebolus, Cladosporium, and Meyerozyma were the dominant fungus, and the abundance of Meyerozyma in COMB and CORNSTR were greater (p < 0.05) than MILLSTR at 12, 24, and 36 h of incubation. In conclusion, it is suggested to feed beef cattle with different proportions of millet straw and corn straw combinations.

Cysteamine Supplementation In Vitro Remarkably Promoted Rumen Fermentation Efficiency towards Propionate Production via Prevotella Enrichment and Enhancing Antioxidant Capacity

Cysteamine (CS) is a vital antioxidant product and nutritional regulator that improves the productive performance of animals. A 2 × 4 factorial in vitro experiment was performed to determine the effect of the CS supplementation levels of 0, 20, 40, and 60 mg/g, based on substrate weight, on the ruminal fermentation, antioxidant capacity, and microorganisms of a high-forage substrate (HF, forage:corn meal = 7:3) in the Statistical Analysis System Institute. After 48 h of incubation, the in vitro dry matter disappearance and gas production in the LF group were higher when compared with a low-forage substrate (LF, forge hay:corn meal = 3:7), which was analyzed via the use of the MIXED procedure of the HF group, and these increased linearly with the increasing CS supplementation (p < 0.01). With regard to rumen fermentation, the pH and acetate were lower in the LF group compared to the HF group (p < 0.01). However, the ammonia N, microbial crude protein, total volatile fatty acids (VFA), and propionate in the LF group were greater than those in the HF group (p < 0.05). With the CS supplementation increasing, the pH, ammonia N, acetate, and A:P decreased linearly, while the microbial crude protein, total VFA, and propionate increased linearly (p < 0.01). Greater antioxidant capacity was observed in the LF group, and the increasing CS supplementation linearly increased the superoxide dismutase, catalase, glutathione peroxidase, total antioxidant capacity, glutathione, and glutathione reductase, while it decreased the malondialdehyde (p < 0.05). No difference occurred in the ruminal bacteria alpha diversity with the increasing CS supplementation, but it was higher in the LF group than in the HF group (p < 0.01). Based on the rumen bacterial community, a higher proportion of Bacteroidota, instead of Firmicutes, was in the LF group than in the HF group. Furthermore, increasing the CS supplementation linearly increased the relative abundance of Prevotella, norank_f_F082, and Prevotellaceae_UCG-001 under the two substrates (p < 0.05). Prevotella, norank_f_F082, and Prevotellaceae_UCG-001 were positively correlated with gas production, rumen fermentation, and antioxidant capacity in a Spearman correlation analysis (r > 0.31, p < 0.05). Overall, a CS supplementation of not less than 20 mg/g based on substrate weight enhanced the rumen fermentation and rumen antioxidant capacity of the fermentation system, and it guided the rumen fermentation towards glucogenic propionate by enriching the Prevotella in Bacteroidetes.

The primate gut mycobiome-bacteriome interface is impacted by environmental and subsistence factors

The gut microbiome of primates is known to be influenced by both host genetic background and subsistence strategy. However, these inferences have been made mainly based on adaptations in bacterial composition - the bacteriome and have commonly overlooked the fungal fraction - the mycobiome. To further understand the factors that shape the gut mycobiome of primates and mycobiome-bacteriome interactions, we sequenced 16 S rRNA and ITS2 markers in fecal samples of four different nonhuman primate species and three human groups under different subsistence patterns (n = 149). The results show that gut mycobiome composition in primates is still largely unknown but highly plastic and weakly structured by primate phylogeny, compared with the bacteriome. We find significant gut mycobiome overlap between captive apes and human populations living under industrialized subsistence contexts; this is in contrast with contemporary hunter-gatherers and agriculturalists, who share more mycobiome traits with diverse wild-ranging nonhuman primates. In addition, mycobiome-bacteriome interactions were specific to each population, revealing that individual, lifestyle and intrinsic ecological factors affect structural correspondence, number, and kind of interactions between gut bacteria and fungi in primates. Our findings indicate a dominant effect of ecological niche, environmental factors, and diet over the phylogenetic background of the host, in shaping gut mycobiome composition and mycobiome-bacteriome interactions in primates.

Effect of Oregano Oil and Cobalt Lactate on Sheep In Vitro Digestibility, Fermentation Characteristics and Rumen Microbial Community

Simple Summary

In the context of a shortage of feed resources and a complete ban on veterinary antibiotics, searching for green additives that can improve the production performance of ruminants has become a popular research topic. Oregano essential oil (EO) inhibits rumen gas production (GP) and regulates animal digestive metabolism, and cobalt lactate (Co) can improve feed digestibility. However, previous studies on EO of oregano and Co showed different results. Therefore, the present study aimed to investigate the effects of different EOC addition levels on rumen in vitro fermentation and rumen bacterial community composition, and the experimental data obtained showed that all five EOC (0.1425% cobalt lactate + 1.13% oregano essential oil + 98.7275% carrier) addition levels in this experiment had no significant effect on nutrient digestibility. However, the addition of 1500 mg·L⁻¹ EOC significantly improved rumen fermentation parameters and altered the microbiota composition. All presented data provide a theoretical basis for the application of oregano essential oil and cobalt in ruminant nutrition.

Abstract

The objective of this experiment was to evaluate the effect of different EOC (0.1425% cobalt lactate + 1.13% oregano essential oil + 98.7275% carrier) levels on in vitro rumen fermentation and microbial changes. Six EOC levels (treatments: 0 mg·L⁻¹, CON; 50 mg·L⁻¹, EOC1; 100 mg·L⁻¹, EOC2; 400 mg·L⁻¹, EOC3; 800 mg·L⁻¹, EOC4 and 1500 mg·L⁻¹, EOC5) were selected to be used to in vitro incubation. The in vitro dry matter digestibility (IVDMD), in vitro neutral detergent fiber digestibility (IVNDFD), in vitro acid detergent fiber digestibility (IVNDFD), pH, ammonia-nitrogen (NH₃-N) concentration, total volatile fatty acid (TVFA) concentration and microbial protein (MCP) concentration were measured after 48 h incubation, after which the groups with significant nutrient digestibility and fermentation parameters were subjected to 16S rRNA sequencing. The results showed that the total gas production (GP) of the EOC5 group was higher than that of the other groups after 12 h of in vitro incubation. TVFA, NH₃-N and MCP concentrations were also shown to be higher in group EOC5 than those in other groups (p < 0.05), while NH₃-N and MCP concentrations in the EOC2 group were lower than those in other groups significantly (p < 0.05). The molar ratio of acetic acid decreased while the molar ratio of propionic acid increased after the addition of EOC. 16S rRNA sequencing revealed that the rumen microbiota was altered in response to adding EOC, especially for the EOC5 treatment, with firmicutes shown to be the most abundant (43.1%). The relative abundance of Rikenellaceae_RC9_gut_group was significantly lower, while the relative abundance of uncultured_bacterium_f_Muribaculaceae and Succiniclasticum was significantly higher in the EOC5 group than those in other groups (p < 0.05). Comprehensive analysis showed that EOC (1500 mg·L⁻¹) could significantly increase gas production, alter sheep rumen fermentation parameters and microbiota composition.

Comparative digestibility and rumen fermentation of camels and sheep fed different forage sources

The present study evaluated the effects of forage sources on dry matter (DM) intake, digestibility, and fermentation parameters in camels vs. sheep. The study was arranged as a 2 × 3 factorial experiment in a completely randomized design by using two animal species (three ruminally cannulated female camels and three male sheep) and three forage sources. The forages were (1) alfalfa hay; 164 and 479 g/kg DM for crude protein (CP) and neutral detergent fiber (NDF), respectively, (2) berseem hay; 121 and 513 g/kg DM for CP and NDF, respectively, and (3) wheat straw (27.5 and 723 g/kg DM for CP and NDF, respectively). Higher DM intake [g/kg body weight (BW)] was noted in sheep compared to camel when alfalfa hay (p < 0.05) and berseem hay (p < 0.05) were fed but was similar between both species when they were fed wheat straw. Forage type rather than animal species had more effect on metabolic intake. Lower digestibility was noted in sheep with wheat straw (p < 0.05). Similar in situ degradability values for crude protein and DM were noted between camels and sheep. In situ degradability of NDF was higher (p < 0.05) in camel than sheep. Greater ruminal pH (p < 0.05) was noted in sheep vs. camels when berseem hay and wheat straw were fed. Lower ruminal passage rate (p < 0.05) was noted in camels and higher total mean retention time. It was concluded that sheep and camels had similar digestion capacities when fed berseem hay and alfalfa hay, however, camels are more efficient than sheep when fed wheat straw.

Comparative evaluation of in vitro techniques for predicting metabolizable energy content of total mixed ration for Murrah buffaloes

The present study was conducted to ascertain the sensitivity of in vitro techniques namely, in vitro gas production (IVGPT) and Cornell Net Carbohydrate and Protein System (CNCPS) fraction for predicting the metabolizable energy (ME) content of total mixed ration for Murrah buffaloes. The total mixed ration forming dietary treatment were TMR1, TMR2 and TMR3 having mixture of maize silage and concentrate in ratio of 30:70, 40:60 and 50:50, respectively. The diets formulated were isocaloric and isonitrogenous. The in vitro gas production was studied by incubation of diet with rumen liquor as inoculum to predict the metabolizable energy content of ruminant feeds. The CNCPS fraction analysing ME content of feed samples was carried out in laboratory. Lactating Murrah buffaloes (n = 18) having similar lactation yield (MY 9 kg±2.5) were allotted to three groups in a completely randomised design and fed TMR as per the dietary treatments. The feeding trial was carried out for 3 months and nutrient utilization was analysed. The efficiency of ME utilization in vivo were compared to in vitro gas production and CNCPS fraction. Correlation coefficient (r) between in vitro techniques and in vivo trial in evaluating ME content demonstrated a significantly (P<0.01) high correlation of 0.734 with IVGPT and 0.752 with CNCPS fraction indicating that both in vitro techniques were reliable in predicting metabolizable energy content of feedstuffs for ruminant feeding.

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.

Effects of Oat Hay Content in Diets on Nutrient Metabolism and the Rumen Microflora in Sheep

Oats have the characteristics of drought tolerance, cold resistance, strong adaptability, high forage yield, and high nutritional value. However, there are few reports on the most appropriate amount of oat hay in ruminant diets, the digestion and metabolism of ruminants, and the rumen microflora. To study the effects of oat hay content in diets on nutrient digestion and metabolism and the rumen microflora in sheep, 9 German Merino and Mongolian crossbred rams of similar body condition and weight with permanent fistulas were selected. The 3 × 3 Latin square design was used to randomly divide the rams into 3 groups, with 3 animals in each group. The three groups were fed different kinds of roughage: whole-plant corn silage only (corn silage group, CSG), oat hay mixed with whole-plant corn silage (1:1) (mixed group, MG), and oat hay only (oat hay group, OHG). The nutrient digestion and metabolism of each group were measured, and the pH and rumen microflora were examined after feeding for different durations. Dynamic changes in microbial communities were detected. The nutrient digestion and metabolism results showed that, with an increase in the content of oat hay in the diet, the intake and apparent digestibility of dry matter (DM) and organic matter (OM) showed an increasing trend, and the intake, digestion, and stability of acid detergent fiber (ADF) and neutral detergent fiber (NDF) increased in the OHG. The apparent digestibility, dietary nitrogen, deposited nitrogen, and nitrogen retention rate in this group were significantly higher than those in the CSG (p < 0.05). The rumen pH and sequencing results showed that the rumen fluid pH of the CSG was significantly lower than that of the OHG at 1 and 5 h (p < 0.05). The main microbial in the rumen of the three groups of sheep were Bacteroides, Sclerotium, and Proteus. The dominant taxon in the CSG was Prevotella, followed by Vibrio syringae, and the dominant taxon in the MG and OHG was Prevotella, followed by Rikenellaceae. Redundancy analysis showed that ADF and NDF in the feed had an effect on the abundance of Fibrobacteres, Ruminococcaceae, and Prevotella. Our findings indicate that the use of oat hay roughage in the diet significantly improves the apparent digestibility of NDF and ADF and helps maintain the stable state of the sheep's rumen internal environment and the growth of rumen microorganisms.

The Inclusion of Concentrate with Quebracho Is Advisable in Two Forage-Based Diets of Ewes According to the In Vitro Fermentation Parameters

Ewes receive hay or graze on fresh pastures supplemented with concentrates to fulfil their lactation requirements. Quebracho (Schinopsis balansae) can be added to change the ruminal fermentation. Fermentation parameters of forages alone and 70:30 forage:concentrate diets with control and quebracho concentrate were compared after 24 h of in vitro incubation. Fresh forage diets produced less gas (p < 0.05) and had greater IVOMD (p < 0.001), ammonia (NH₃-N) content, valeric acid, branched-chain volatile fatty acid proportions, and lower propionic acid proportion than the hay diets (p < 0.01). In the hay diets, methane production increased with control concentrate (p < 0.01) and tended to decrease with quebacho concentrate (p < 0.10). The inclusion of both concentrates increased the acetic:propionic ratio (p < 0.01), and only the inclusion of quebracho concentrate increased the IVOMD (p < 0.01). In the fresh forage diets, gas and methane production increased with the inclusion of the control concentrate (p < 0.05), but methane production decreased with quebracho concentrate (p < 0.01). The inclusion of quebracho concentrate reduced the NH₃-N content and valeric acid proportion (p < 0.05). In conclusion, the inclusion of quebracho concentrate would be advisable to reduce the CH₄ production and NH₃-N content in fresh forage diets and to increase the IVOMD in hay diets in comparison with the forages alone.

Effects of oregano essential oil on the ruminal pH and microbial population of sheep

Oregano essential oil (OEO), which has antimicrobial properties, may be used for altering the ruminal pH and microbial populations of sheep, as observed by the altered volatile fatty acid patterns. To further elucidate the effects of OEO on ruminal pH and microbial populations of sheep, 3 German merino sheep × local sheep crossbred rams with permanent ruminal fistulas were randomly assigned to a 3 × 3 Latin square design with 12-d periods. The treatments were as follows: control (CON); OEO4: OEO supplied at 4 g•d-1; and OEO7: OEO supplied at 7 g•d-1. Starting on day 11, rumen fluid was collected at 0 h, and at 4, 8, 12, 24 and 48 h after supplying OEO, and then pH values of rumen fluid were immediately measured. The abundance of microbial populations was determined by using qPCR. The ruminal pH values were similar among the sheep from all treatments. The abundance of ruminal fungi was higher for the sheep supplied OEO7 compared with the sheep supplied CON and OEO4, especially at 4 and 12 h. The abundance of ruminal protozoa decreased with supplied OEO, indicating that OEO could inhibit the protozoa. The abundance of the total ruminal bacteria was similar for the sheep from all treatments, but R. flavefaciens, R. albus and F. succinogenes increased in the sheep supplied OEO4 compared with those in the sheep supplied CON, however, the sheep supplied OEO7 had higher abundances of R. flavefaciens than the sheep supplied CON. These results demonstrated that supplying OEO to sheep did not affect the ruminal pH but could shift the rumen microbial population to one with less protozoa. Supplying OEO can preferentially enhance the growth of certain rumen microbial populations, but the shifts were influenced by the supply rate. Therefore, supplying low amount (i.e. 4 g•d-1) of OEO could have positive effects on ruminal microbial populations, whereas supplying elevated doses of OEO could be detrimental to those same ruminal microbial populations.

Comparative diversity analysis of ruminal methanogens in Murrah buffaloes (Bubalus bubalis) in four states of North India

We compared the community structure of methanogens in Murrah breed of buffaloes of four states of north India using 16S rRNA gene clone library method. The results revealed the dominance of methanogens related to Methanobrevibacter in three states, while Methanomicrobium-related methanogens were abundant in one state.

Sunflower Oil and Nannochloropsis oculata Microalgae as Sources of Unsaturated Fatty Acids for Mitigation of Methane Production and Enhancing Diets' Nutritive Value

The objective of this assay was to investigate the effect of adding sunflower oil, Nannochloropsis oculata microalgae and their mixture at 0, 1, 2, 3, 4, and 5% to three total mixed rations (TMRs) with different concentrate:forage ratios (40C:60F, 50C:50F, and 60C:40F) on in vitro gas production (GP), methane (CH₄) production, and nutrient degradability. Asymptotic GP, GP rate, CH₄ concentration/g acid detergent fiber (ADF), dry matter (DM) degradability (DMD), short chain fatty acids (SCFAs), and ruminal bacteria population increased, but neutral detergent fiber (NDF) degradability (NDFD), ADF degradability (ADFD), and protozoa count decreased with increasing concentrate level in the TMR. Methane production/g DM and NDF was higher for 50C:50F TMR. Sunflower oil reduced asymptotic GP, lag time, CH₄ production/g ADF, ammonia-N (NH₃-N), and SCFA. Compared to the control treatments, additives decreased GP rate, while sunflower oil/N. oculata mixture increased DMD and NDFD. All additives at 5% increased GP rate and lag time and decreased CH₄ production/g DM, ADF, and NDF, ruminal NH₃-N, and protozoa count. All additives at 2% increased DMD, NDFD and ADFD, SCFA, and bacteria population. Supplementation of TMR, containing different concentrate:forage ratios, with sunflower oil, N. oculata, and sunflower oil/N. oculata mixture at different doses modified in vitro GP, CH₄ production, and nutrient degradability.

Intake, digestibility, growth performance, and enteric methane emission of Brazilian semiarid non-descript breed goats fed diets with different forage to concentrate ratios

The aim of this study was to evaluate the intake, digestibility, growth performance, and enteric methane emissions of Brazilian semiarid non-descript breed goats (NDG) fed diets with different forage:concentrate ratios (100:0, 80:20, 60:40, 40:60, and 20:80) on a dry matter basis. Forty uncastrated male NDG with an average initial body weight of 13.3 kg ± 4.7 kg were distributed in a completely randomized design, with five treatments and eight replications. Ground Tifton-85 hay was used as forage and ground corn and soybean meal were used as concentrate. The sulfur hexafluoride tracer technique was used to measure methane emissions. The intake of dry matter, organic matter, crude protein, and ether extract increased linearly while the intake of neutral detergent fiber decreased linearly as the concentrate proportion increased (P < 0.05). The digestibility of dry matter and organic matter increased while the digestibility of neutral detergent fiber decreased as the concentrate level increased (P < 0.05). There were linear increases in final body weight, total weight gain, average daily gain, and feed efficiency (P < 0.0001). Methane emissions per unit of body weight (ranging from 1.9 to 0.5 g/kg), metabolic body weight (ranging from 3.9 to 1.2 g/kg), and dry matter intake (ranging from 58.8 to 21.9 g/kg) reduced linearly as the concentrate proportion increased (P < 0.01). Decreasing the forage to concentrate ratio in the diet decreased methane emission and increased growth performance of NDG. The 80:20 ratio could be considered more appropriate to reduce methane emissions from NDG, which did not change much at higher levels of concentrate.

Role of anaerobic fungi in wheat straw degradation and effects of plant feed additives on rumen fermentation parameters in vitro

In the present study, rumen microbial groups, i.e. total rumen microbes (TRM), total anaerobic fungi (TAF), avicel enriched bacteria (AEB) and neutral detergent fibre enriched bacteria (NEB) were evaluated for wheat straw (WS) degradability and different fermentation parameters in vitro. Highest WS degradation was shown for TRM, followed by TAF, NEB and least by AEB. Similar patterns were observed with total gas production and short chain fatty acid profiles. Overall, TAF emerged as the most potent individual microbial group. In order to enhance the fibrolytic and rumen fermentation potential of TAF, we evaluated 18 plant feed additives in vitro. Among these, six plant additives namely Albizia lebbeck, Alstonia scholaris, Bacopa monnieri, Lawsonia inermis, Psidium guajava and Terminalia arjuna considerably improved WS degradation by TAF. Further evaluation showed A. lebbeck as best feed additive. The study revealed that TAF plays a significant role in WS degradation and their fibrolytic activities can be improved by inclusion of A. lebbeck in fermentation medium. Further studies are warranted to elucidate its active constituents, effect on fungal population and in vivo potential in animal system.

Metagenomic assessment of the functional potential of the rumen microbiome in Holstein dairy cows

The microbial ecology of the rumen microbiome is influenced by the diet and the physiological status of the dairy cow and can have tremendous influence on the yield and components of milk. There are significant differences in milk yields between first and subsequent lactations of dairy cows, but information on how the rumen microbiome changes as the dairy cow gets older has received little attention. We characterized the rumen microbiome of the dairy cow for phylogeny and functional pathways by lactation group and stage of lactation using a metagenomics approach. Our findings revealed that the rumen microbiome was dominated by Bacteroidetes (70%), Firmicutes (15-20%) and Proteobacteria (7%). The abundance of Firmicutes and Proteobacteria were independently influenced by diet and lactation. Bacteroidetes contributed to a majority of the metabolic functions in first lactation dairy cows while the contribution from Firmicutes and Proteobacteria increased incrementally in second and third lactation dairy cows. We found that nearly 70% of the CAZymes were oligosaccharide breaking enzymes which reflect the higher starch and fermentable sugars in the diet. The results of this study suggest that the rumen microbiome continues to evolve as the dairy cow advances in lactations and these changes may have a significant role in milk production.

Associative patterns among anaerobic fungi, methanogenic archaea, and bacterial communities in response to changes in diet and age in the rumen of dairy cows

The rumen microbiome represents a complex microbial genetic web where bacteria, anaerobic rumen fungi (ARF), protozoa and archaea work in harmony contributing to the health and productivity of ruminants. We hypothesized that the rumen microbiome shifts as the dairy cow advances in lactations and these microbial changes may contribute to differences in productivity between primiparous (first lactation) and multiparous (≥second lactation) cows. To this end, we investigated shifts in the ruminal ARF and methanogenic communities in both primiparous (n = 5) and multiparous (n = 5) cows as they transitioned from a high forage to a high grain diet upon initiation of lactation. A total of 20 rumen samples were extracted for genomic DNA, amplified using archaeal and fungal specific primers, sequenced on a 454 platform and analyzed using QIIME. Community comparisons (Bray-Curtis index) revealed the effect of diet (P < 0.01) on ARF composition, while archaeal communities differed between primiparous and multiparous cows (P < 0.05). Among ARF, several lineages were unclassified, however, phylum Neocallimastigomycota showed the presence of three known genera. Abundance of Cyllamyces and Caecomyces shifted with diet, whereas Orpinomyces was influenced by both diet and age. Methanobrevibacter constituted the most dominant archaeal genus across all samples. Co-occurrence analysis incorporating taxa from bacteria, ARF and archaea revealed syntrophic interactions both within and between microbial domains in response to change in diet as well as age of dairy cows. Notably, these interactions were numerous and complex in multiparous cows, supporting our hypothesis that the rumen microbiome also matures with age to sustain the growing metabolic needs of the host. This study provides a broader picture of the ARF and methanogenic populations in the rumen of dairy cows and their co-occurrence implicates specific relationships between different microbial domains in response to diet and age.

In vitro and Lactation Responses in Mid-lactating Dairy Cows Fed Protected Amino Acids and Fat

The objective of this study was to evaluate the effect of ruminally protected amino acids (RPAAs) and ruminally protected fat (RPF) supplementation on ruminal fermentation characteristics (in vitro) and milk yield and milk composition (in vivo). Fourteen mid-lactating Holstein dairy cows (mean weight 653±62.59 kg) were divided into two groups according to mean milk yield and number of days of postpartum. The cows were then fed a basal diet during adaptation (2 wk) and experimental diets during the treatment period (6 wk). Dietary treatments were i) a basal diet (control) and ii) basal diet containing 50 g of RPAAs (lysine and methionine, 3:1 ratio) and 50 g of RPF. In rumen fermentation trail (in vitro), RPAAs and RPF supplementation had no influence on the ruminal pH, dry matter digestibility, total volatile fatty acid production and ammonia-N concentration. In feeding trial (in vivo), milk yield (p<0.001), 4% fat corrected milk (p<0.05), milk fat (p<0.05), milk protein (p<0.001), and milk urea nitrogen (p<0.05) were greater in cows fed RPAAs and RPF than the corresponding values in the control group. With an index against as 0%, the rates of decrease in milk yield and milk protein were lower in RPAAs and RPF treated diet than those of basal diet group (p<0.05). In conclusion, diet supplemented with RPAAs and RPF can improve milk yield and milk composition without negatively affecting ruminal functions in Holstein dairy cows at mid-lactating.

Data Build-up for the Construction of Korean Specific Greenhouse Gas Emission Inventory in Livestock Categories

Many studies on methane (CH₄) and nitrous oxide (N₂O) emissions from livestock industries have revealed that livestock production directly contributes to greenhouse gas (GHG) emissions through enteric fermentation and manure management, which causes negative impacts on animal environment sustainability. In the present study, three essential values for GHG emission were measured; i.e., i) maximum CH₄ producing capacity at mesophilic temperature (37°C) from anaerobically stored manure in livestock category (B_0,KM, Korean livestock manure for B₀), ii) EF_3(s) value representing an emission factor for direct N₂O emissions from manure management system S in the country, kg N₂O-N kg N⁻¹, at mesophilic (37°C) and thermophilic (55°C) temperatures, and iii) N_ex(T) emissions showing annual N excretion for livestock category T, kg N animal⁻¹ yr⁻¹, from different livestock manure. Static incubation with and without aeration was performed to obtain the N₂O and CH₄ emissions from each sample, respectively. Chemical compositions of pre- and post-incubated manure were analyzed. Contents of total solids (% TS) and volatile solid (% VS), and the ratio of carbon to nitrogen (C/N) decrease significantly in all the samples by C-containing biogas generation, whereas moisture content (%) and pH increased after incubation. A big difference of total nitrogen content was not observed in pre- and post-incubation during CH₄ and N₂O emissions. CH₄ emissions (g CH₄ kg VS⁻¹) from all the three manures (sows, layers and Korean cattle) were different and high C/N ratio resulted in high CH₄ emission. Similarly, N₂O emission was found to be affected by % VS, pH, and temperature. The B_0,KM values for sows, layers, and Korean cattle obtained at 37°C are 0.0579, 0.0006, and 0.0828 m³ CH₄ kg VS⁻¹, respectively, which are much less than the default values in IPCC guideline (GL) except the value from Korean cattle. For sows and Korean cattle, N_ex(T) values of 7.67 and 28.19 kg N yr⁻¹, respectively, are 2.5 fold less than those values in IPCC GL as well. However, N_ex(T) value of layers 0.63 kg N yr⁻¹ is very similar to the default value of 0.6 kg N yr⁻¹ in IPCC GLs for National greenhouse gas inventories for countries such as South Korea/Asia. The EF_3(s) value obtained at 37°C and 55°C were found to be far less than the default value.

Effect of Crude Protein Levels in Concentrate and Concentrate Levels in Diet on In vitro Fermentation

The effect of concentrate mixtures with crude protein (CP) levels 10%, 13%, 16%, and 19% and diets with roughage to concentrate ratios 80:20, 60:40, 40:60, and 20:80 (w/w) were determined on dry matter (DM) and organic matter (OM) digestibility, and fermentation metabolites using an in vitro fermentation technique. In vitro fermented attributes were measured after 4, 24, and 48 h of incubation respectively. The digestibility of DM and OM, and total volatile fatty acid (VFA) increased whereas pH decreased with the increased amount of concentrate in the diet (p<0.001), however CP levels of concentrate did not have any influence on these attributes. Gas production reduced with increased CP levels, while it increased with increasing concentrate levels. Ammonia nitrogen (NH3-N) concentration and microbial CP production increased significantly (p<0.05) by increasing CP levels and with increasing concentrate levels in diet as well, however, no significant difference was found between 16% and 19% CP levels. Therefore, 16% CP in concentrate and increasing proportion of concentrate up to 80% in diet all had improved digestibility of DM and organic matter, and higher microbial protein production, with improved fermentation characteristics.

Changes in methane emission, rumen fermentation in response to diet and microbial interactions

To evaluate relative contributions of different microbial groups in rumen, the mono-culture (i.e. bacteria, protozoa and fungi) and co-cultures (i.e. bacterial-protozoal, fungal-protozoal and bacterial-fungal) were tested in vitro using high and low roughage diets. Total gas and methane were higher in bacterial-fungal and bacterial-protozoal co-cultures, while lower in fungal-protozoal than controls (high and low roughage with complete rumen consortia; control 1 and 2, respectively). Digestibility and total volatile fatty acids were lower in bacterial-fungal co-culture with both high and low roughage diets. Methanogens decreased in bacterial-fungal co-culture with high roughage. With high roughage, counts were lower for bacteria with bacterial-protozoal, protozoa with fungal-protozoal, and fungi with the bacterial-fungal co-cultures. Total gas was higher in bacterial mono-culture with low roughage, but methane was not detected in any mono-culture. Digestibility and total volatile fatty acids were significantly lowered with protozoal mono-culture. Methanogens reduced significantly in mono-cultures with high roughage diet than control 1. Defaunation reduced methanogens without significantly affecting rumen fermentation.