Antibiotic resistance is an increasingly important environmental pollutant with direct consequences for human health. Identification of environmental sources of antibiotic resistance genes (ARGs) makes it possible to follow their evolution and prevent their entry into the clinical setting. ARGs have been found in environmental sources exogenous to the original source and previous studies have shown that these genes are capable of being transferred from livestock to humans. Due to the nature of farming and the slaughter of ruminants for food, humans interact with these animals in close proximity, and for this reason it is important to consider the risks to human health. In this study, we characterised the ARG populations in the ovine rumen, termed the resistome. This was done using the Comprehensive Antibiotic Resistance Database (CARD) to identify the presence of genes conferring resistance to antibiotics within the rumen. Genes were successfully mapped to those that confer resistance to a total of 30 different antibiotics. Daptomycin was identified as the most common antibiotic for which resistance is present, suggesting that ruminants may be a source of daptomycin ARGs. Colistin resistance, conferred by the gene pmrE, was also found to be present within all samples, with an average abundance of 800 counts. Due to the high abundance of some ARGs (against daptomycin) and the presence of rare ARGs (against colistin), we suggest further study and monitoring of the rumen resistome as a possible source of clinically relevant ARGs.

Rumen liquid can effectively degrade lignocellulosic biomass, in which rumen microorganisms play an important role. In this study, transformation of bacterial community structure in rumen liquid anaerobic digestion of rice straw was explored. Results showed that rice straw was efficiently hydrolyzed and acidified, and the degradation efficiency of cellulose, hemicellulose and lignin reached 46.2%, 60.4%, and 12.9%, respectively. The concentration of soluble chemical oxygen demand (SCOD) and total volatile fatty acid (VFA) reached 12.9 and 8.04 g L⁻¹. The high-throughput sequencing results showed that structure of rumen bacterial community significantly changed in anaerobic digestion. The Shannon diversity index showed that rumen bacterial diversity decreased by 32.8% on the 5th day of anaerobic digestion. The relative abundance of Prevotella and Fibrobacter significantly increased, while Ruminococcus significantly decreased at the genus level. The Spearman correlation heatmap showed that pH and VFA were the critical factors affecting the rumen bacterial community structure. The function prediction found that rumen bacteria mainly functioned in carbohydrate transport and metabolism, which might contain a large number of lignocellulose degrading enzyme genes. These studies are conducive to the better application of rumen microorganisms in the degradation of lignocellulosic biomass.

Muscle, liver and kidney of 21 Barbary sheep (Ammotragus lervia) from Mosor Mountain, Croatia, were sampled to quantify the activity of caesium and potassium radionuclides and five toxic and ten essential stabile elements in order to establish reference values for this species and to evaluate the potential of Barbary sheep tissues to reflect environmental pollution. We also assessed seasonal diet (botanical composition and dry matter content) of Barbary sheep based on analyses of a rumen content of culled animals. None of the 19 plant species (mostly grasses) identified as part of the Barbary sheep diet is known as a stabile element or radionuclide hyperaccumulator. Measured levels reflected low environmental pollution with arsenic, cadmium, mercury and lead, with levels generally less than those reported for wild herbivorous ungulates. Methodological differences (detection limit of elements in muscle) were shown to hamper interpretation and comparison of the Toxic Contamination Index (TCI) values with those published for other species. There was no homeostasis disturbance of trace elements in Barbary sheep, either due to inadequate intake via food or as an adverse effect due to a high toxic metal(loid) burden. Consumption of the muscle and liver of wild Barbary sheep can be considered safe for the health of adult consumers regarding toxic metal(loid)s and radioactive caesium, though the liver should be avoided as a food item in vulnerable population groups due to the possible adverse effects of cadmium and lead. Otherwise, muscle and liver are a rich source of copper, iron, selenium and zinc for consumers and, as such, can benefit the overall dietary intake of essential elements.

The effects of patchouli essential oil (PEO) as an alternative to antibiotics on ruminal methanogenesis, feed degradability, and enzyme activities were evaluated. The basal substrate was incubated without additives (control, CTL) and with monensin (MON, 6 μM/g DM) or patchouli essential oil (PEO, 90 μg/g DM) for 24 h. In three different runs, the gas production (GP) was recorded at 2, 4, 8, 12, and 24 h of incubation using a semi-automatic system. The results revealed that MON had decreased (P < 0.05) the net GP and CH₄ production and digestible and metabolizable energy relative to PEO supplementation. The in vitro truly degraded organic matter was not influenced by PEO application, while was reduced (P = 0.027) with MON. Both PEO and MON had similar reducing effect on the activity of carboxymethylcellulase (P = 0.030), in vitro truly degraded neutral detergent fiber (P = 0.010), NH₃-N concentrations (P = 0.012), acetate proportion (C2, P = 0.046), C2 to C3 ratio (P = 0.023), and total protozoal count (P = 0.017). Both additives recorded similar elevating potential on the α-amylase activity (P = 0.012), propionate (C3) proportion (P = 0.011), and microbial protein (P = 0.034) compared with CTL. Effects of MON and PEO on ruminal feed degradability, microbial enzyme activities, and total protozoa counts may be responsible for modifying rumen fermentation ecology. Addition of PEO may act as a desirable alternative rumen modifier for MON in ruminant diets.

Twenty Awassi lambs were used to find the effects of direct-fed microbials (DFM) and long-acting trace minerals rumen bolus (TMB) supplements on performance, blood biochemical variables, and antioxidant status of the lambs under grazing conditions. The lambs were randomly distributed into four groups as follows: (1) untreated, (2) oral dose of 5 mL DFM, (3) TMB, or (4) oral dose of 5 mL DFM and TMB. The treatments were carried out for 90 days. Supplementation with TMB significantly increased (P < 0.05) average daily gain (ADG) and feed efficiency compared with the control. A significant (P < 0.05) increase in blood albumin in the DFM and a significant (P < 0.05) decrease in aspartate aminotrasferase were found in the lambs supplemented with TMB alone or in combination with DFM. Supplementing lambs with TMB resulted in higher glutathione peroxidase, total antioxidant capacity (P < 0.001) and activity of superoxide dismutase (P < 0.05) compared with no supplementation and supplementation with DFM only. In conclusion, TMB supplementation had a positive impact on performance traits and the antioxidant system of the lambs under grazing condition.

By-products of raw artichoke (RA) (Cynara scolymus L.) and boiled broccoli (BB) (Brassica oleracea, var. italica) were ensiled in plastic bags for 24 days. Then, chemical composition, nutritive characteristics, in vitro rumen degradability, in vivo digestibility and phytosanitary residue contents of the silages were evaluated. The fermentative parameters studied indicated that plastic bags were a suitable method to silage RA and BB by-products. Both silages had a high in vitro rumen DM disappearance at 72 h, although it was higher in the BB silage (96.8 vs. 82.1%). In vivo digestibility of DM was similar and high in both silages (78.5 and 80.0% in RA and BB), but crude protein and NDF digestibilities were higher in the BB silage (83.0 and 88.3% vs. 55.1 and 78.8%). No residues of analysed phytosanitary were found. In conclusion, silages of wastes from the processing of artichoke and broccoli were free from the analysed several phytosanitary residues, their nutritive value made them adequate for feeding ruminant animals and are an environmentally friendly way of disposal of such residues.

Protein quality plays a key role than quantity in growth, production, and reproduction of ruminants. Application of high concentration of dietary crude protein (CP) did not balance the proportion of these limiting amino acids (AA) at duodenal digesta of high producing dairy cow. Thus, dietary supplementation of rumen-protected AA is recommended to sustain the physiological, productive, and reproductive performance of ruminants. Poor metabolism of high CP diets in rumen excretes excessive nitrogen (N) through urine and feces in the environment. This excretion is usually in the form of nitrous oxide, nitric oxide, nitrate, and ammonia. In addition to producing gases like methane, hydrogen carbon dioxide pollutes and has a potentially negative impact on air, soil, and water quality. Data specify that supplementation of top-limiting AA methionine and lysine (Met + Lys) in ruminants’ ration is one of the best approaches to enhance the utilization of feed protein and alleviate negative biohazards of CP in ruminants’ ration. In conclusion, many in vivo and in vitro studies were reviewed and reported that low dietary CP with supplemental rumen-protected AA (Met + Lys) showed a good ability to reduce N losses or NH₃. Also, it helps in declining gases emission and decreasing soil or water contamination without negative impacts on animal performance. Finally, further studies are needed on genetic and molecular basis to explain the impact of Met + Lys supplementation on co-occurrence patterns of microbiome of rumen which shine new light on bacteria, methanogen, and protozoal interaction in ruminants.

This study aimed to evaluate the effect of calcium lignosulfonate associated with whole cottonseed in high-concentrate diets for sheep. Eight Dorper crossbred sheep with an average live weight of 42.5 ± 1.70 kg were assigned to two 4 × 4 Latin squares. The following experimental diets were evaluated: control diet (without calcium lignosulfonate) and diets with inclusion of 50, 100, and 150 g of calcium lignosulfonate/kg fresh matter. Diets were composed of soybean meal, ground corn, and whole cottonseed. Feed intake, digestibility, metabolic characteristics, and feeding behavior were evaluated. The intake of nutritional components did not show significant differences as a function of the lignosulfonate levels in the diet; however, the increase in calcium lignosulfonate levels linearly decreased the dry matter digestibility. Rumen ammonia nitrogen concentrations decreased linearly as the lignosulfonate levels in the diets were increased. There was no effect of lignosulfonate levels on blood parameters or feeding behavior of the animals. The use of lignosulfonate associated with cottonseed decreases the digestibility of dry matter and the concentration of rumen ammonia nitrogen, but does not change the intake of nutritional components, the blood parameters, or the feeding behavior of sheep.

The objective of the present study is to examine the effect of yeast (Saccharomyces cerevisiae) on reduction of methane (CH₄) production in dairy and beef cattle using meta-analytic methods. After compilation of relevant scientific publications available from the literature between 1990 and 2016, and applying exclusion and inclusion criteria, meta-analyses of data from dairy and beef cattle were applied for the pooled dataset or for each animal category (dairy or beef). The results of meta-analysis of all three datasets (all cattle, dairy cattle, or beef cattle) suggested that effect size of yeast either on daily CH₄ production or on CH₄ production per dry matter intake (CH₄/DMI) was not significant. The results of Q test and I² statistic suggest that there is no heterogeneity between different studies on CH₄ production and CH₄/DMI. The results of meta-analysis suggest that use of yeast (Saccharomyces cerevisiae) as feed additive does not offer significant results in terms of reduction of CH₄ production in dairy and beef cattle. Further research on the effects of different doses of yeast, use of yeast products, different strains, and experimental designs is warranted to elucidate the effects of yeasts on methane production in the rumen.