Few studies have examined the effects of feeding total mixed ration (TMR) versus roughage and concentrate separately (SF) on ruminant methane production. Therefore, this study compared differences in methane production, ruminal characteristics, total tract digestibility of nutrients, and rumen microbiome between the two feeding methods in Holstein steers. A total six Holstein steers of initial bodyweights 540 ± 34 kg were divided into two groups and assigned to a same experimental diet with two different feeding systems (TMR or SF) in a crossover design with 21 d periods. The experimental diet contained 73% concentrate and 27% forage and were fed twice a day. The total tract digestibility of crude protein, neutral detergent fibre, and organic matter were not affected by the two different feeding systems. Steers fed TMR emitted more methane (138.5 vs. 118.2 L/d; P < 0.05) and lost more gross energy as methane energy (4.0 vs. 3.5% gross energy intake; P = 0.005) compared to those fed SF. Steers fed TMR had greater (P < 0.05) total volatile fatty acid (VFA), ammonia-N concentrations and propionate proportion of total VFA at 1.5 h, whereas lower after that compared to steers fed SF. The greater (P < 0.05) acetate: propionate ratio at 4.5 h for steers fed TMR reflected the shift of H2 sink from propionate towards acetate synthesis. The lower (P < 0.05) isobutyrate and isovalerate proportions of total VFA observed in steers fed TMR implies decrease in net consumption of H2 for microbial protein synthesis compared to SF. There were no differences in both major bacterial and archaeal diversity between TMR and SF, unlike several minor bacterial abundances. The minor groups such as Coprococcus, Succiniclasticum, Butyrivibrio, and Succinivibrio were associated with the changes in ruminal VFA profiles or methanogenesis indirectly. Overall, these results indicate that SF reduces methane emissions from ruminants and increases propionate proportion of total VFA without affecting total tract digestion compared to TMR. There were no evidences that the response differed due to different major underlying microbial population.

ABSTRACT. This study determined the appropriate biochemical assay for measuring plasma tartrate-resistant acid phosphatase isoform 5b (TRAP5b) activity; this information is important to clarify the relationship between plasma TRAP5b and known biochemical bone markers in cattle. When plasma TRAP5b was measured using fluorometric and spectrophotometric methods, hemolysis products in plasma did not affect the former method. In plasma from healthy cattle, there was a good correlation (r=0.66) between the 2 methods. In agerelated profiles, plasma TRAP5b (r=-0.53), hydroxyproline (HYP, r=-0.56) and bone-specific alkaline phosphatase (BALP, r=-0.44) showed significant negative correlations with age; these three parameters decreased until 4 or 5 years of age and then remained constant. There were significant correlations between TRAP5b and HYP (r=0.83) or BALP (r=0.83). Our results show that the fluorometric assay can be performed with a high degree of precision and reproducibility without interference from hemolysis, and that the age-related changes in plasma TRAP5b, HYP, and BALP constitute additional background values for clinical guidance in bovine medicine.KEY WORDS: biochemical bone marker, cattle, fluorometry, plasma, tartrate-resistant acid phosphatase isoform 5b (TRAP5b).

ABSTRACT. We examined fluctuations in plasma tartrate-resistant acid phosphatase isoform 5b (TRAP5b) measured using fluorometry in conjunction with those in calcium (Ca) and other bone metabolic markers from 2 weeks prepartum to 2 weeks postpartum in 7 primiparous and 18 multiparous pregnant cows. The plasma Ca concentration decreased temporarily on the day of calving in multiparous cows only. Plasma TRAP5b peaked on the day of calving in primiparous and multiparous cows and was significantly lower in multiparous cows than in primiparous cows 2 weeks before and after parturition. Plasma hydroxyproline increased 1 week postpartum in multiparous cows. Bone-specific alkaline phosphatase and osteocalcin tended to decrease after parturition in primiparous and multiparous cows. These results suggest that bone resorption increases around parturition in healthy parturient cows from the viewpoint of the TRAP5b activity.KEY WORDS: bone metabolic marker, bone resorption, dairy cow, parturition, tartrate-resistant acid phosphatase isoform 5b (TRAP5b).

BackgroundAs a primary source of Shiga-toxin-producing Escherichia coli (STEC) infection, cattle are often targeted to develop strategies for reducing STEC contamination. Monitoring the virulence potentials of STEC isolates from cattle is important for tracing contamination sources, managing outbreaks or sporadic cases, and reducing the risks for human infection. This study aimed to investigate the prevalence of STEC in cattle farm samples in South Korea and to assess their virulence potentials.ResultsIn total, 63 STEC were isolated from 496 cattle farm samples, and temperature and rainfall affected STEC prevalence (p < 0.001). The O157 serogroup was most prevalent, followed by O108, O8, O84, O15, and O119. In the stx variant test, high prevalence of stx2a and stx2c (known to be associated with high STEC virulence) were observed, and stx2g, a bovine STEC variant, was detected in STEC O15 and O109. Additionally, stx1c was detected in eae-positive STEC, suggesting genetic dynamics among the virulence genes in the STEC isolates. STEC non-O157 strains were resistant to tetracycline (17.9%), ampicillin (14.3%), and cefotaxime (3.6%), while STEC O157 was susceptible to all tested antimicrobials, except cefotaxime. The antimicrobial resistance genes, bla TEM (17.5%), tetB (6.3%), and tetC (4.8%), were only detected in STEC non-O157, whereas tetE (54.0%) was detected in STEC O157. AmpC was detected in all STEC isolates. Clustering was performed based on the virulence gene profiles, which grouped STEC O84, O108, O111, and O157 together as potentially pathogenic STEC strains. Finally, PFGE suggested the presence of a prototype STEC that continues to evolve by genetic mutation and causes within- and between-farm transmission within the Gyeonggi province.ConclusionsConsiderable numbers of STEC non-O157 were isolated from cattle farms, and the virulence and antimicrobial resistance features were different between the STEC O157 and non-O157 strains. STEC from cattle with virulence or antimicrobial resistance genes might represent a threat to public health and therefore, continual surveillance of both STEC O157 and non-O157 would be beneficial for controlling and preventing STEC-related illness.

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