Oregano Essential Oils Promote Rumen Digestive Ability by Modulating Epithelial Development and Microbiota Composition in Beef Cattle

Castration alters the ileum microbiota of Holstein bulls and promotes beef flavor compounds

BACKGROUND

In the beef industry, bull calves are usually castrated to improve flavor and meat quality; however, this can reduce their growth and slaughter performance. The gut microbiota is known to exert a significant influence on growth and slaughter performance. However, there is a paucity of research investigating the impact of castration on gut microbiota composition and its subsequent effects on slaughter performance and meat flavor.

RESULT

The objective of this study was to examine the processes via which castration hinders slaughter productivity and enhances meat quality. Bull and castrated calves were maintained under the same management conditions, and at slaughter, meat quality was assessed, and ileum and epithelial tissue samples were obtained. The research employed metagenomic sequencing and non-targeted metabolomics techniques to investigate the makeup of the microbiota and identify differential metabolites. The findings of this study revealed the Carcass weight and eye muscle area /carcass weight in the bull group were significantly higher than those in the steer group. There were no significant differences in the length, width, and crypt depth of the ileum villi between the two groups. A total of 53 flavor compounds were identified in the two groups of beef, of which 16 were significantly higher in the steer group than in the bull group, and 5 were significantly higher in the bull group than in the steer group. In addition, bacteria, Eukaryota, and virus species were significantly separated between the two groups. The lipid metabolism pathways of α-linolenic acid, linoleic acid, and unsaturated fatty acids were significantly enriched in the Steers group. Compared with the steer group, the organic system pathway is significantly enriched in the bull group. The study also found that five metabolites (LPC (0:0/20:3), LPC (20:3/0:0), LPE (0:0/22:5), LPE (22:5/0:0), D-Mannosamine), and three species (s_Cloning_vector_Hsp70_LexA-HP1, s_Bacteroides_Coprophilus_CAG: 333, and s_Clostridium_nexile-CAG: 348) interfere with each other and collectively have a positive impact on the flavor compounds of beef.

CONCLUSIONS

These findings provide a basic understanding that under the same management conditions, castration does indeed reduce the slaughter performance of bulls and improve the flavor of beef. Microorganisms and metabolites contribute to these changes through interactions.

Do microbial-gut-muscle mediated by SCFAs, microbial-gut-brain axis mediated by insulin simultaneously regulate yak IMF deposition?

Ruminant rumen plays an important role in the digestibility of cellulose, hemicellulose, starch and fat. In this study, the yaks under graze and stall feeding were chosen as the models of different rumen bacteria and intramuscular fat (IMF). The characteristics of IMF deposition, serum indexes in yaks were detected; the bacteria, metabolites in rumen was explored by 16S rRNA sequencing technology, untargeted metabolomics based on liquid chromatography-mass spectrometer and gas chromatography, respectively; the transcriptome of longissimus thoracis was identified by RNA-Sequencing analysis. Based on above results, a hypothesis that yak IMF deposition is regulated by the combined action of microbiome-gut-brain and muscle axis was proposed. The short-chain fatty acids (SCFAs) and neurotransmitters precursors like acetylcholine produced in yak rumen promoted insulin secretion via central nervous system. These insulin resulted in the high expression of SREBF1 gene by gut-brain axis; SCFAs can directly arrive to muscular tissue via blood circulation system, then activated the expression of PPARγ gene by gut-muscle axis. The expression of lipogenesis gene SCD, FABP3, CPT1, FASN and ACC2 was accordingly up-regulated. This study firstly introduce the theory of microbiome-gut-brain/muscle axis into the study of ruminant, and comprehensively expounded the regulatory mechanism of yak IMF deposition.

Effects of Oregano Essential Oil on IgA+, IgG+, and IgM+ Cells in the Jejunum of Castrated Holstein Bulls

The aim of this study was to investigate the effect of oregano essential oil on IgA+, IgG+, and IgM+ cells in the jejunum of castrated Holstein bulls. Twelve castrated Holstein bulls were randomly divided into control (YCK) and oregano essential oil (YEO) groups. Pathological changes in the jejunum were observed by HE staining, and the expression levels of IgA, IgG, and IgM in the jejunum were detected by ELISA. The distributions of IgA+, IgG+, and IgM+ cells in the jejunum were analysed by multiplex immunofluorescence and immunohistochemistry. The results showed that the jejunal villi were detached in the YCK group, which may have been related to inflammation, while the intestinal epithelium was clear and intact in the YEO group. The expressions of IgA, IgG, and IgM were significantly reduced by 40.75%, 30.76%, and 50.87%. The IgA+, IgG+, and IgM+ cells were diffusely distributed in the lamina propria of the jejunum, and were reduced by 17.07%, 6.44%, and 6.15%, respectively. Oregano essential oil did not alter the distribution characteristics of IgA+, IgG+, or IgM+ cells in the jejunum, but it suppressed inflammatory response, decreased immunoglobulin content, and significantly enhanced the formation of an immune barrier in the gastrointestinal mucosa.

Oregano essential oil modulates colonic homeostasis and intestinal barrier function in fattening bulls

Oregano essential oil (OEO) primarily contains phenolic compounds and can serve as a dietary supplement for fattening bulls. However, the precise molecular mechanism underlying this phenomenon remains largely elusive. Therefore, this study investigated the impact of adding OEO to diet on the integrity of the intestinal barrier, composition of the colonic microbiome, and production of microbial metabolites in fattening bulls. Our goal was to provide insights into the utilization of plant essential oil products in promoting gastrointestinal health and welfare in animals. We employed amplicon sequencing and metabolome sequencing techniques to investigate how dietary supplementation with OEO impacted the intestinal barrier function in bulls. The inclusion of OEO in the diet resulted in several notable effects on the colon of fattening bulls. These effects included an increase in the muscle thickness of the colon, goblet cell number, short-chain fatty acid concentrations, digestive enzyme activity, relative mRNA expression of intestinal barrier-related genes, and relative expression of the anti-inflammatory factor IL-10. Additionally, α-amylase activity and the relative mRNA expression of proinflammatory cytokines decreased. Moreover, dietary OEO supplementation increased the abundance of intestinal Bacteroides, Coprobacillus, Lachnospiraceae_UCG_001, and Faecalitalea. Metabolomic analysis indicated that OEO primarily increased the levels of 5-aminovaleric acid, 3-methoxysalicylic acid, and creatinine. In contrast, the levels of maltose, lactulose, lactose, and D-trehalose decreased. Correlation analysis showed that altered colonic microbes and metabolites affected intestinal barrier function. Taken together, these results demonstrate that OEO facilitates internal intestinal environmental homeostasis by promoting the growth of beneficial bacteria while inhibiting harmful ones.

Dietary oregano essential oil supplementation alters meat quality, oxidative stability, and fatty acid profiles of beef cattle

This study was conducted to elucidate the effects of oregano essential oil (OEO) supplementation on the meat quality, antioxidant capacity, and nutritional value of the longissimus thoracis muscle in steers. Steers were divided into three groups (n = 9) and fed either a basal diet, or a basal diet supplemented with 130 mg/d OEO, or 230 mg/d OEO for 390 days. The results demonstrated that dietary OEO supplementation increased the total antioxidant capacity and activity of catalase, glutathione peroxidase, and superoxide dismutase, and decreased pH30min, pH24h, cooking loss, and malondialdehyde content. OEO increased the concentrations of polyunsaturated fatty acids and conjugated linoleic acid. In contrast, saturated fatty acids decreased, accompanied by increased essential amino acids, flavor amino acids, and total amino acids in the longissimus thoracis muscle. In summary, dietary OEO supplementation promotes the nutritional and meat quality of beef by maintaining its water-holding capacity and meat color, enhancing its antioxidative capacity, and preventing lipid oxidation.

Early life supplementation with a natural blend containing turmeric, thymol, and yeast cell wall components to optimize rumen anatomical and microbiological development and productivity in dairy goats

Ruminants are born with an anatomically, microbiologically, and metabolically immature rumen. Optimizing the rearing of young ruminants represent an important challenge in intensive dairy farms. Therefore, the objective of this study was to evaluate the effects of dietary supplementation of young ruminants with a plant extract blend containing turmeric, thymol, and yeast cell wall components such as mannan oligosaccharides and β-glucans. One hundred newborn female goat kids were randomly allocated to 2 experimental treatments, which were unsupplemented (CTL) or supplemented with the blend containing plant extracts and yeast cell wall components (PEY). All animas were fed with milk replacer, concentrate feed, and oat hay, and were weaned at 8 wk of age. Dietary treatments lasted from wk 1 to 22 and 10 animals from each treatment were randomly selected to monitor feed intake, digestibility, and health-related indicators. These latter animals were euthanized at wk 22 of age to study the rumen anatomical, papillary, and microbiological development, whereas the remaining animals were monitored for reproductive performance and milk yield during the first lactation. Results indicated that PEY supplementation did not lead to feed intake or health issues because PEY animals tended to have a higher concentrate intake and lower diarrheal incidence than CTL animals. No differences between treatments were noted in terms of feed digestibility, rumen microbial protein synthesis, health-related metabolites, or blood cell counts. Supplementation with PEY promoted a higher rumen empty weight, and rumen relative proportion to the total digestive tract weight, than CTL animals. This was accompanied with a higher rumen papillary development in terms of papillae length and surface area in the cranial ventral and caudal ventral sacs, respectively. The PEY animals also had higher expression of the MCT1 gene, which is related to volatile fatty acid absorption by the rumen epithelium, than CTL animals. The antimicrobial effects of the turmeric and thymol could explain the decreased the rumen absolute abundance of protozoa and anaerobic fungi. This antimicrobial modulation led to a change in the bacterial community structure, a decrease in the bacteria richness, and to the disappearance (i.e., Prevotellaceae_UCG-004, Bacteroidetes_BD2-2, Papillibacter, Schwartzia, and Absconditabacteriales_SR1) or decline of certain bacterial taxa (i.e., Prevotellaceae_NK3B31_group, and Clostridia_UCG-014). Supplementation with PEY also decreased the relative abundance of fibrolytic (i.e., Fibrobacter succinogenes and Eubacterium ruminantium) and increased amylolytic bacteria (Selenomonas ruminantium). Although these microbial changes were not accompanied with significant differences in the rumen fermentation, this supplementation led to increased body weight gain during the preweaning period, higher body weight during the postweaning period, and higher fertility rate during the first gestation. On the contrary, no residual effects of this nutritional intervention were noted on the milk yield and milk components during the first lactation. In conclusion, supplementation with this blend of plant extracts and yeast cell wall component in early life could be considered as a sustainable nutritional strategy to increase body weight gain and optimize the rumen anatomical and microbiological development in young ruminants, despite having minor productive implications later in life.

Effect of Cooking Method and Doneness Degree on Volatile Compounds and Taste Substance of Pingliang Red Beef

This study used gas chromatography-ion mobility spectrometry (GC-IMS) and high-performance liquid chromatography (HPLC) methods to examine the impact of cooking methods and doneness on volatile aroma compounds and non-volatile substances (fatty acids, nucleotides, and amino acids) in Pingliang red beef. The flavor substances' topographic fingerprints were established, and 45 compounds were traced to 71 distinct signal peaks. Pingliang red beef's fruity flavor was enhanced thanks to the increased concentration of hexanal, styrene, and 2-butanone that resulted from instant boiling. The levels of 3-methylbutanal, which contributes to the characteristic caramel-chocolate-cheese aroma, peaked at 90 min of boiling and 40 min of roasting. The FFA content was reduced by 28.34% and 27.42%, respectively, after the beef was roasted for 40 min and instantly boiled for 10 s (p > 0.05). The most distinctive feature after 30 min of boiling was the umami, as the highest levels of glutamate (Glu) (p < 0.05) and the highest equivalent umami concentration (EUC) values were obtained through this cooking method. Additionally, adenosine-5'-monophosphate (AMP) and inosine-5'-monophosphate (IMP) decreased with increasing doneness compared to higher doneness, indicating that lower doneness was favorable in enhancing the umami of the beef. In summary, different cooking methods and doneness levels can affect the flavor and taste of Pingliang red beef, but it is not suitable for high-doneness cooking.

Effects of fennel (Foeniculum vulgare) seed powder addition during early lactation on performance, milk fatty acid profile, and rumen fermentation parameters of Holstein cows

Introduction

Aromatic and herbal plants usage as feed additives have become a new tendency in dairy cows’ nutrition to enhance animal performance. This experiment was performed to study the effects of supplementing fennel seed powder (FSP) to diets during early lactation on performance, milk fatty acid (FA) profile, and rumen fermentation of Holstein dairy cows.

Methods

Twenty-four primiparous Holstein dairy cows (10 ± 3 d in milk, 30 ± 2.1 Kg of milk/d, 610 ± 31 Kg body weight; mean ± SE) were balanced for actual milk yield and calving date (n = 8 per treatment) in a complete randomized design. Animals were allocated randomly to diets containing 0 g/d (0FSP), 25 g/d (25FSP), or 50 g/d (50FSP) FSP, individually top-dressed over the total mixed ration. The experimental period was 45 d consisting of the first 15 d for adaptation and the final 30 d for data collection and sampling.

Results and discussion

Dry matter intake responded quadratically to FSP feeding, and cows fed 25FP treatment had greater DMI than 0FSP treatment. The average ruminal pH value decreased linearly as FSP increased in diets. Ruminal valerate and isovalerate proportion increased linearly as FSP inclusion in diets increased, while acetate proportion decreased and acetate:propionate ratio tended to decrease linearly. Increasing FSP in diets linearly increased serum glucose, globulin, and total protein concentrations. Milk yield increased linearly as FSP inclusion in diets increased, whereas milk composition was unaffected. Increasing FSP in diets linearly increased de novo and mixed FA and decreased preformed FA in milk. Dietary treatments did not affect saturated FA, whereas unsaturated FA, mono and poly unsaturated FA linearly decreased with increasing FSP inclusion in diets. Moreover, the content of C18:0 tended to decrease, and C18:1 cis-9 decreased linearly as FSP inclusion increased. Also, increasing the FSP level in diets decreased linearly non-esterified fatty acids and acetone concentrations in the milk. It could be concluded that FSP addition at 50 g/d could enhance performance of early lactating cows.

Castration alters the cecal microbiota and inhibits growth in Holstein cattle

To determine the effects of castration on growth performance, serum hormone levels, cecal microbiota composition, and metabolites in cattle. A total of 18 Holstein bulls and steers were divided into bull and steer groups and randomly assigned to 3 pens (3 cattle per pen, and each cattle were separated by a fence) to determine the average daily gain (ADG), daily dry matter intake (DMI), and feed efficiency (G/F). After the finishing trial, six cattle per group were randomly slaughtered. Serum was collected to measure the hormone concentration, and the cecal content was collected to measure the pH, short-chain fatty acids, and digestive enzyme activities. Metagenome sequencing and untargeted metabolomics were used to investigate the microbiota composition, functional profiles, and differential metabolites of the cecal contents. We found that castration significantly decreased ADG, DMI, and G/F in cattle (P < 0.05). The serum testosterone, thyroxine, growth hormone (P < 0.05), and triiodothyronine (P < 0.01) concentrations significantly decreased in the steer group when compared to those of the bull group. The activities of cellulase, xylanase, pectinase, and β-glucosidase (P < 0.05) significantly decreased in the steer group, whereas the activities of lipase and α-amylase significantly increased. Moreover, castration significantly decreased the relative abundance of Ruminococcaceae_bacterium, Treponema_porcinum, Oscillibacter_sp. (P < 0.05), and Alistipes_senegalensis (P < 0.01), whereas the relative abundance of Phocaeicola_plebeius (P < 0.05) was significantly increased. Also, the relative abundance of Phocaeicola_plebeius was negatively correlated with testosterone levels, and the function of the cecal microbiota was enriched in the GH29 and GH97 families in the steer group. Metabolomic analysis indicated that castration increased the levels of L-valine, L-phenylalanine, L-aspartic acid, L-isoleucine, L-lysine, methionine, L-glutamic acid, and L-leucine, while decreasing the levels of α-ketoglutaric acid through the 2-oxocarboxylic acid metabolism pathway. In addition, α-ketoglutaric acid was negatively correlated with Oscillibacter_sp. (P < 0.01). Overall, castration can inhibit cattle growth by altering the composition of the cecal microbiota. Therefore, this study provides a theoretical and practical basis for improving the growth performance of steers.

Yeast Products Mediated Ruminal Subenvironmental Microbiota, and Abnormal Metabolites and Digestive Enzymes Regulated Rumen Fermentation Function in Sheep

Yeast products (YP) are commonly used as rumen regulators, but their mechanisms of action are still unclear. Based on our previous studies, we questioned whether yeast products would have an impact on rumen solid-associated (SA) and liquid-associated (LA) microorganisms and alter rumen fermentation patterns. Thirty 3-month-old male sheep weighing 19.27 ± 0.45 kg were selected and randomized into three groups for 60 days: (1) basal diet group (CON group), (2) basal diet add 20 g YP per day (low YP, LYP group) and (3) basal diet add 40 g YP per day (high YP, HYP group). The results demonstrated that the addition of YP increased rumen cellulase activity, butyrate and total volatile fatty acid (TVFA) concentrations (p < 0.05), while it decreased rumen amylase activity and abnormal metabolites, such as lactate, lipopolysaccharides (LPS) and histamine (HIS) (p < 0.05). Metagenomic analysis of rumen microorganisms in three groups revealed that YP mainly influenced the microbial profiles of the SA system. YP increased the relative abundance of R. flavefaciens and decreased methanogens in the SA system (p < 0.05). With the addition of YP, the abundance of only a few lactate-producing bacteria increased in the SA system, including Streptococcus and Lactobacillus (p < 0.05). However, almost all lactate-utilizing bacteria increased in the LA system, including Megasphaera, Selenomonas, Fusobacterium and Veillonella (p < 0.05). In addition, YP increased the abundance of certain GHs family members, including GH43 and GH98 (p < 0.05), but decreased the abundance of some KEGG metabolic pathways involved in starch and sucrose metabolism, biosynthesis of antibiotics and purine metabolism, among others. In conclusion, the addition of YP to high-concentrate diets can change the abundance of major functional microbiota in the rumen, especially in the solid fraction, which in turn affects rumen fermentation patterns and improves rumen digestibility.

Cysteamine-supplemented diet for cashmere goats: A potential strategy to inhibit rumen biohydrogenation and enhance plasma antioxidant capacity

Cysteamine (CS), as a feed supplement, can increase the level of growth hormone (GH) in the blood, promote animal growth. However, little attention has been paid to the effects of CS on the rumen microbiome and metabolic profile in cashmere goats. This study aimed to assess the effects of rumen microbiota, metabolites, and plasma antioxidative capacity induced by CS supplementation in cashmere goats. We selected 30 Inner Mongolia white cashmere goat ewes (aged 18 months), and randomly separate the goats into three groups (n = 10 per group) to experiment for 40 days. Oral 0 (control group, CON), 60 (low CS, LCS), or 120 mg/kg BW^-1 (high CS, HCS) coated CS hydrochloride every day. Using 16S and internal transcribed spacer (ITS) rRNA gene amplicon sequencing, we identified 12 bacterial and 3 fungal genera with significant changes among the groups, respectively. We found a significant increase in rumen NH₃-N and total volatile fatty acid (TVFA) concentrations in the LCS and HCS groups compared with the CON. With untargeted LC-MS/MS metabolomics, we screened 59 rumen differential metabolites. Among the screened metabolites, many unsaturated and saturated fatty acids increased and decreased with CS treatment, respectively. CS supplementation increased the levels of plasma total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), superoxide dismutase (SOD), GH, and insulin-like growth factor-1(IGF-1). Spearman correlation analysis revealed that the abundance of U29-B03, Lactococcus, and Brochothrix were positively associated with the levels of δ2-THA, TVFA and antioxidant capacity. In conclusion, CS significantly affected rumen microbiota and fermentation parameters, and ultimately inhibited the biohydrogenation of rumen metabolites, enhanced plasma antioxidant capacity, and regulated some hormones of the GH-IGF-1 axis. This study provides an overall view into the CS application as a strategy to improve health production in cashmere goats.

Geraniol Treatment for Irritable Bowel Syndrome: A Double-Blind Randomized Clinical Trial

Geraniol is an acyclic monoterpene alcohol with well-known anti-inflammatory and antimicrobial properties which has shown eubiotic activity towards gut microbiota (GM) in patients with irritable bowel syndrome (IBS).

METHODS

Fifty-six IBS patients diagnosed according to Rome III criteria were enrolled in an interventional, prospective, multicentric, randomized, double-blinded, placebo-controlled trial. In the treatment arm, patients received a low-absorbable geraniol food supplement (LAGS) once daily for four weeks.

RESULTS

Patients treated with LAGS showed a significant reduction in their IBS symptoms severity score (IBS-SSS) compared to the placebo (195 vs. 265, p = 0.001). The rate of responders according to IBS-SSS (reduction ≥ 50 points) was significantly higher in the geraniol vs placebo group (52.0% vs. 16.7%, p = 0.009) mainly due to the IBS mixed subtype. There were notable differences in the microbiota composition after geraniol administration, particularly a significant decrease in a genus of Ruminococcaceae, Oscillospira (p = 0.01), a decreasing trend for the Erysipelotrichaceae and Clostridiaceae families (p = 0.1), and an increasing trend for other Ruminococcaceae taxa, specifically Faecalibacterium (p = 0.09). The main circulating proinflammatory cytokines showed no differences between placebo and geraniol arms.

CONCLUSION

LAGS was effective in treating overall IBS symptoms, together with an improvement in the gut microbiota profile, especially for the IBS mixed subtype.

A Meta-Analysis of Essential Oils Use for Beef Cattle Feed: Rumen Fermentation, Blood Metabolites, Meat Quality, Performance and, Environmental and Economic Impact

The objective of this study was to see how dietary supplementation with essential oils (EOs) affected rumen fermentation, blood metabolites, growth performance and meat quality of beef cattle through a meta-analysis. In addition, a simulation analysis was conducted to evaluate the effects of EOs on the economic and environmental impact of beef production. Data were extracted from 34 peer-reviewed studies and analyzed using random-effects statistical models to assess the weighted mean difference (WMD) between control and EOs treatments. Dietary supplementation of EOs increased (p < 0.01) dry matter intake (WMD = 0.209 kg/d), final body weight (WMD = 12.843 kg), daily weight gain (WMD = 0.087 kg/d), feed efficiency (WMD = 0.004 kg/kg), hot carcass weight (WMD = 5.45 kg), and Longissimus dorsi muscle area (WMD = 3.48 cm2). Lower (p < 0.05) ruminal concentration of ammonia nitrogen (WMD = −1.18 mg/dL), acetate (WMD = −4.37 mol/100 mol) and total protozoa (WMD = −2.17 × 105/mL), and higher concentration of propionate (WMD = 0.878 mol/100 mol, p < 0.001) were observed in response to EOs supplementation. Serum urea concentration (WMD = −1.35 mg/dL, p = 0.026) and haptoglobin (WMD = −39.67 μg/mL, p = 0.031) were lower in cattle supplemented with EOs. In meat, EOs supplementation reduced (p < 0.001) cooking loss (WMD = −61.765 g/kg), shear force (WMD = −0.211 kgf/cm2), and malondialdehyde content (WMD = −0.040 mg/kg), but did not affect pH, color (L* a* and b*), or chemical composition (p > 0.05). Simulation analysis showed that EOs increased economic income by 1.44% and reduced the environmental footprint by 0.83%. In conclusion, dietary supplementation of EOs improves productive performance and rumen fermentation, while increasing the economic profitability and reducing the environmental impact of beef cattle. In addition, supplementation with EOs improves beef tenderness and oxidative stability.

Effects of a Polyherbal Dietary Additive on Performance, Dietary Energetics, Carcass Traits, and Blood Metabolites of Finishing Lambs

The objective of this study was to evaluate the effects of dietary supplementation of a polyherbal additive (PA) containing hydrolyzable tannins, flavonoids, and essential oils on productive performance, dietary energetics, carcass and meat characteristics, and blood metabolites of lambs in their finishing phase. Twenty-eight Pelibuey × Katahdin lambs (20.52 ± 0.88 kg body weight (BW)) were housed in individual pens and assigned to four treatments (n = 7) with different doses of PA: 0 (CON), 1 (PA1), 2 (PA2), and 3 (PA3) g of PA kg−1 of DM for 56 days. Compared to the CON, lambs in PA1 treatment had higher average daily gain (p = 0.03), higher dietary energy utilization (p = 0.01), greater backfat thickness (p = 0.02), greater Longissimus dorsi muscle area (p = 0.01), and better feed conversion ratio (p = 0.02). PA supplementation did not affect (p > 0.05) dry matter intake, carcass yield, biometric measures, and meat chemical composition. All hematological and most of the blood biochemical parameters were similar in lambs of all treatments (p > 0.05). However, compared to the CON, lambs assigned to the PA3 treatment had lower serum urea concentration (p = 0.05) and higher serum albumin concentration (p = 0.03). In conclusion, low doses of PA could be used as a growth promoter in finishing lambs without affecting dry matter intake, carcass yield, meat chemical composition, and health status of the lambs. However, more in vivo research is needed to better understand the impact of bioactive compounds from PA used on productivity, metabolism, and health status of finishing lambs.

Essential Oils as In Vitro Ruminal Fermentation Manipulators to Mitigate Methane Emission by Beef Cattle Grazing Tropical Grasses

There is increasing pressure to identify natural feed additives to mitigate methane emissions from livestock systems. Our objective was to investigate the effects of essential oils (EO) extracts star anise (Illicium verum), citronella (Cymbopogon winterianus), clove bud (Eugenia caryophyllus), staigeriana eucalyptus (Eucalyptus staigeriana), globulus eucalyptus (Eucalyptus globulus), ginger (Zingiber officinale), ho wood (Cinnamomum camphora), melaleuca (Melaleuca alternifolia), oregano (Origanum vulgare) and white thyme (Thymus vulgaris) on in vitro methane emissions from four rumen-cannulated Nellore cattle grazing a tropical grass pasture as inoculum donors. The semi-automated gas production technique was used to assess total gas production, dry matter degradability, partitioning factor, ammoniacal nitrogen, short-chain fatty acids and methane production. All essential oils were tested in four doses (0, 50, 250 and 500 mg/L) in a randomized block design, arranged with four blocks, 10 treatments, four doses and two replicates. Within our study, oregano and white Thyme EO reduced net methane production at 250 mg/L, without affecting substrate degradation. Essential oils from oregano and white thyme have the potential to modify ruminal fermentation and suppress rumen methanogenesis without negative effects on feed digestibility, indicating promise as alternatives to ionophores for methane reduction in beef cattle.