Methane, one of the important greenhouse gas, has a higher global warming potential than that of carbon dioxide. Agriculture, especially livestock, is considered as the biggest sector in producing anthropogenic methane. Among livestock, ruminants are the highest emitters of enteric methane. Methanogenesis, a continuous process in the rumen, carried out by archaea either with a hydrogenotrophic pathway that converts hydrogen and carbon dioxide to methane or with methylotrophic pathway, which the substrate for methanogenesis is methyl groups. For accurate estimation of methane from ruminants, three methods have been successfully used in various experiments under different environmental conditions such as respiration chamber, sulfur hexafluoride tracer technique, and the automated head-chamber or GreenFeed system. Methane production and emission from ruminants are increasing day by day with an increase of ruminants which help to meet up the nutrient demands of the increasing human population throughout the world. Several mitigation strategies have been taken separately for methane abatement from ruminant productions such as animal intervention, diet selection, dietary feed additives, probiotics, defaunation, supplementation of fats, oils, organic acids, plant secondary metabolites, etc. However, sustainable mitigation strategies are not established yet. A cumulative approach of accurate enteric methane measurement and existing mitigation strategies with more focusing on the biological reduction of methane emission by direct-fed microbials could be the sustainable methane mitigation approaches.

Seasonal effects on rumen microbiome and enteric methane (CH₄) emissions are poorly documented. In this study, 6 Holstein and 6 Jersey steers were fed the same total mixed ration diet during winter, spring, and summer seasons under a 2 × 3 factorial arrangement for 30 days per season. The dry matter intake (DMI), rumen fermentation characteristics, enteric CH₄ emissions and rumen microbiota were analyzed. Holstein had higher total DMI than Jersey steers regardless of season. However, Holstein steers had the lowest metabolic DMI during summer, while Jersey steers had the lowest total DMI during winter. Jersey steers had higher CH₄ yields and intensities than Holstein steers regardless of season. The pH was decreased, while ammonia nitrogen concentration was increased in summer regardless of breed. Total volatile fatty acids concentration and propionate proportions were the highest in winter, while acetate and butyrate proportion were the highest in spring and in summer, respectively, regardless of breed. Moreover, Holstein steers produced a higher proportion of propionate, while Jersey steers produced a higher proportion of butyrate regardless of season. Metataxonomic analysis of rumen microbiota showed that operational taxonomic units and Chao 1 estimates were lower and highly unstable during summer, while winter had the lowest Shannon diversity. Beta diversity analysis suggested that the overall rumen microbiota was shifted according to seasonal changes in both breeds. In winter, the rumen microbiota was dominated by Carnobacterium jeotgali and Ruminococcus bromii, while in summer, Paludibacter propionicigenes was predominant. In Jersey steers, Capnocytophaga cynodegmi, Barnesiella viscericola and Flintibacter butyricus were predominant, whereas in Holstein steers, Succinivibrio dextrinosolvens and Gilliamella bombicola were predominant. Overall results suggest that seasonal changes alter rumen microbiota and fermentation characteristics of both breeds; however, CH₄ emissions from steers were significantly influenced by breeds, not by seasons.

Background and Aim: Pigeon rearing has been gaining popularity for recent years. They are reared remarkably very close to the house of the owner. This activity, therefore, may pose potential threats for humans as well as other animals as pigeons may carry and spread different pathogens including drug-resistant bacteria. This study was conducted to explore the prevalence of Escherichia coli and Salmonella spp. as well as their antibiogram profile along with an association analysis. Materials and Methods: Forty swab samples were collected from 20 pigeons during the study. E. coli and Salmonella spp. were isolated and identified on various types of agars, including MacConkey, Eosin methylene blue, Brilliant green, and Salmonella-Shigella agar. Biochemical tests such as the carbohydrate fermentation test, the triple sugar iron agar slant reaction, the indole test, the methyl red test, the catalase test, as well as the Voges–Proskauer test were also performed. Besides, the presence of E. coli was further confirmed by polymerase chain reaction (PCR). Moreover, antimicrobial susceptibility testing of the isolates was performed against nine antibiotics from seven classes on the Mueller-Hinton agar based on the Kirby–Bauer disk diffusion method. Results: The overall prevalence of E. coli and Salmonella spp. was 52.5 and 27.5%, respectively. The prevalence of the pathogenic E. coli was 61.90%. The antibiogram profile of 21 E. coli as well as 11 Salmonella spp. revealed that all isolates, except one, were resistant to one to six antibiotics. Around 61.90%, 71.43%, 23.81%, 61.90%, 23.81%, 19.05%, and 52.38% of E. coli showed resistance against amoxicillin, ampicillin, azithromycin, erythromycin, nalidixic acid, gentamicin, and tetracycline, respectively. Furthermore, E. coli resistance was not observed in case of ciprofloxacin and levofloxacin. Similarly, around 36.36%, 27.27%, 27.27%, 45.45%, 81.82%, 100%, and 18.18% of the Salmonella spp. showed resistance against amoxicillin, ampicillin, azithromycin, erythromycin, nalidixic acid, tetracycline, and levofloxacin, respectively. However, all Salmonella spp. (100%) were found to show sensitivity against ciprofloxacin and gentamicin. Multidrug-resistant (MDR) E. coli (23.80%) and Salmonella spp. (54.54%) were also isolated. Furthermore, both positive (odds ratio [OR] >1) and negative (OR <1) drug resistance associations, with a higher frequency of positive associations, were found in E. coli. A significant positive association was observed between ampicillin and amoxicillin (OR: 81.67, 95% confidence interval: 2.73-2447.57, p=0.01). Conclusion: Pigeon carrying MDR E. coli and Salmonella spp. may contribute to the transmission and spread of these microorganisms. Therefore, strict hygienic measures should be taken during the farming of pigeons to decrease the potential transmission of E. coli and Salmonella spp. from pigeon to humans as well as other animals. So far, this is the first report of the PCR-based identification of pathogenic E. coli from pigeons in Bangladesh.

This study was designed to evaluate the in vitro and in vivo effects of reductive acetogens isolated from ruminants on methane mitigation, and milk performance, respectively. Four acetogens, Proteiniphilum acetatigenes DA02, P. acetatigenes GA01, Alkaliphilus crotonatoxidans GA02, and P. acetatigenes GA03 strains were isolated from ruminants and used in in vitro experiment. A control (without acetogen) and a positive group (with Eubacterium limosum ATCC 8486) were also included in in vitro experiment. Based on higher acetate as well as lower methane producing ability in in vitro trial, P. acetatigenes GA03 was used as inoculum for in vivo experiment. Holstein dairy cows (n = 14) were divided into two groups viz. control (without) and GA03 group (diet supplied with P. acetatigenes GA03 at a feed rate of 1% supplementation). Milk performance and blood parameters were checked for both groups. In in vitro, the total volatile fatty acids and acetate production were higher (p < 0.05) in all 4 isolated acetogens than the control and positive treatment. Also, all acetogens significantly lowered (p < 0.05) methane production in comparison to positive and control groups however, GA03 had the lowest (p < 0.05) methane production among 4 isolates. In in vivo, the rate of milk yield reduction was higher (p < 0.05) in the control than GA03 treated group (5.07 vs 2.4 kg). Similarly, the decrease in milk fat was also higher in control (0.14% vs 0.09%) than treatment. The somatic cell counts (SCC; ×103/mL) was decreased from 128.43 to 107.00 in acetogen treated group however, increased in control from 138.14 to 395.71. In addition, GA03 increased blood glucose and decreased non-esterified fatty acids. Our results suggest that the isolated acetogens have the potential for in vitro methane reduction and P. acetatigenes GA03 strain could be a candidate probiotic strain for improving milk yield and milk fat in lactating cows with lowering SCCs.

The effects of rumen buffer agents on ruminal fermentation parameters and bacterial community composition were determined using in vitro and in vivo experiments in three rumen-cannulated, high-concentrate fed Holstein Friesian dairy cows. Experiment 1 in vitro treatments included bentonite, calcium carbonate, calcium oxide, sodium bicarbonate, sodium sesquicarbonate, and processed coral, and unbuffered samples served as the control. Experiment 2 in vitro treatments were based on the formulation of various combinations of the buffer agents used in Experiment 1. Combinations were selected for the in vivo study based on their buffering ability. Calcium oxide, sodium bicarbonate, and sodium sesquicarbonate stabilized the ruminal pH and improved in vitro rumen fermentation. The combined buffer agents had a significant effect on pH, buffering capacity, total gas, and total volatile fatty acids. Firmicutes and Bacteroidetes were the dominant phyla in both treatments and the control. Ruminococcus and Prevotella were found to be the dominant genera. Ruminococcus bromii was predominant in the treatment group. Prevotella jejuni was more abundant in the control group compared to the treatment group, in which its abundance was very low. Ruminococcus flavefaciens and Intestinimonas butyriciproducens gradually increased in abundance as cows received treatment. Overall, a high-concentrate diet administered to cows induced adverse changes in ruminal pH; however, buffer supplementation enhanced ruminal fermentation characteristics and altered bacterial community, which could contribute to preventing ruminal acidosis.

The present study was carried out during the period of June 2016 to June 2017 to evaluate the antibiotic sensitivity and resistant pattern of bacteria isolated from table eggs of commercial layers considering food safety issue. A total of 200 egg samples (100 for egg shell surface and 100 for egg content) were collected from different retail markets of Dhaka city in sterile polythene bags in a view to prevent extraneous contamination and transported to the laboratory immediate after collection using icebox. The samples were inoculated onto nutrient broth and nutrient agar plates aerobically at 37°Cfor isolation. The isolated organisms were identified based on staining, motility, colony morphology and biochemical tests. The isolated bacteria were also subjected to characterize their antibiotic sensitivity. About 74% egg samples (148 out of 200 samples) were positive for microbial contamination. Among them 100 (100 %) samples had their shells contaminated with microbes of different genera; however, only 48 (48%) growths were observed from the egg contents. The major contaminants are Escherichia coli (34.64%), Coagulase positive Staphylococcus (24.29%), Salmonella spp. (20.71%) followed by Coagulase negative Staphylococcus (10%), Pseudomonas spp. (6.43%) and Bacillus spp. (3.93%). The isolated bacteria E. coli, Coagulase positive Staphylococcus, Salmonella spp. and Pseudomonas spp. showed their greatest sensitivity against ciprofloxacin, ceftriaxone and azithromycin whereas resistant against tetracycline, amoxicillin and ampicillin. There is potential for these antibiotic-resistant bacteria to be transferred to humans through contaminated eggs and are of public health concern from food safety point of view. Asian J. Med. Biol. Res. December 2018, 4(4): 323-329