Supplementation of ruminants with bromoform-containing red algae of the genus Asparagopsis or pure bromoform preparations is a potent strategy to mitigate enteric methane ( CH 4 ) emissions from ruminant livestock. The efficacy of Asparagopsis and bromoform to decrease CH 4 production is reduced with high-fibre diets, but the mechanisms explaining this interaction with diet composition are unknown. Bromoform and other halogenated CH 4 analogues inhibit CH 4 formation by reacting with reduced corrinoids involved in the transfer of a methyl group to coenzyme M in methanogenesis. Given that high-fibre diets promote vitamin B 12 synthesis in the rumen, it is possible that Asparagopsis and bromoform preparations are less efficacious with high-fibre diets because there is more vitamin B 12 to react with bromoform. In one serial culture and three batch culture experiments, we examined the hypothesis that vitamin B 12 can impair the efficacy of bromoform, other halogenated CH 4 analogues, and Asparagopsis at inhibiting ruminal methanogenesis. In Experiment 1, vitamin B 12 supplemented to ruminal cultures in serial transfers 1 to 4 at 8.86 mg/L or spiked at 422 mg/L in serial transfer 5 markedly reversed the inhibition of methanogenesis and the associated increase in the relative abundance of Methanobrevibacter spp. caused by bromoform supplemented at 0.50 µM. In Experiments 2 and 3, vitamin B 12 at a maximal concentration of 500 and 10.0 mg/L, respectively, did not impair the inhibition of methanogenesis by bromoform at 5.0 and 0.50 µM, respectively. In Experiment 4, vitamin B 12 at physiological concentrations did not affect the inhibition of methanogenesis by Asparagopsis biomass. The concentrations of added vitamin B 12 required to reverse in vitro the antimethanogenic effects of bromoform were considerably higher than the reported concentrations of vitamin B 12 and total cobamides in the rumen. Therefore, our results suggest that vitamin B 12 and total cobamides are unlikely to explain the lower efficacy of Asparagopsis and bromoform preparations at inhibiting methanogenesis in vivo with high-fibre diets. However, published results on the in vivo temporal dynamics of bromoform, dibromomethane, and bromomethane in the rumen of animals supplemented with Asparagopsis and bromoform preparations are still needed to fully rule out this possibility.
Canola meal ( CM ) is a valuable protein source with strong potential to partially replace conventional protein ingredients in swine diets. However, its application is limited by the presence of anti-nutritional factors ( ANFs ). This study investigated whether fermentation with two probiotic Bacillus subtilis strains, BS9 and L5, which our team recently isolated, could improve the nutritional quality of CM and confer functional benefits in nursery pigs. The CM was first fermented with each strain for 48 h and subsequently incorporated into a six-week feeding trial in weaning pigs. The trial has four groups: negative control, positive control with 0.03% ZnO (PC), 15% BS9-fermented CM ( BS9-FCM ), and L5-fermented CM ( L5-FCM ). Pigs were fed treatment diets for four weeks, followed by an additional two-week (weeks 5 and 6) trial in which all the pigs were fed the same diet without fermentation treatment to assess any residual effects. Individual BW and weekly feed intake were recorded throughout the study. CM fermentation increased temperature and pH and improved CM nutritional characteristics. Fermentation significantly reduced the ANFs such as phytic acid, NDF, and glucosinolates while improving CP, soluble protein, and mineral availability. In the in vivo trial, BS9-FCM maintained performance similar to the ZnO supplement positive control ( PC ) group during the treatment period. In week 6, BS9-FCM showed an enhanced feed conversion ratio compared to PC. In week 6, L5-FCM significantly reduced the E. coli counts in faecal samples. Fermented CM also reduced ileal gene expression of the pro-inflammatory chemokine IL8 in both BS9 and L5 groups, and downregulation of the innate immune receptor TLR4 was observed in BS9-FCM, indicating immunomodulatory effects. Overall, fermentation of CM effectively reduced ANFs and improved nutrient composition, with a later feed efficiency benefit for BS9 and changes in intestinal inflammatory gene expression. Our findings suggest that fermentation with selected probiotics can be an efficient approach to improve CM nutritional value.
