Plantain (Plantago lanceolata) is an herb used to reduce the forage deficit of ryegrass-based pastures during the summer. The herb is being promoted for its reduced environmental impact in terms of nitrogen emissions, particularly reducing urinary nitrogen, but the impact will depend on the quality of the plantain crop which is a function of the growth stages in its production cycle. When plantain matures, the proportion of reproductive stems increase at the cost of green leaves, which changes the chemical composition and reduces feed quality. Additionally, some bioactive compounds (e.g. condensed tannin, aucubin and acteoside), which may have an effect on fermentability, and as a result CH4 production, are present in plantain. Their concentrations vary across seasons and maturity stages of the plant, and therefore, the maturity stage of plantain, in fact all forages, should be considered when the potential to reduce CH4 emissions is evaluated. Therefore, the objective of the study by Dr M.M. Della Rosa and colleagues was to evaluate CH4 emissions and rumen fermentation characteristics from non-lactating and non-pregnant cows fed plantain or ryegrass as a sole diet at two forage maturity stages. Their hypotheses: (1) feeding plantain to cows would result in a decrease in CH4 yield and an increase in reduced short chain fatty acids at the cost of acetate proportion, and (2) CH4 yield would be lower when cows are fed forages in a reproductive stage rather than in a vegetative stage. The results of the study were published in the Journal of Dairy Science, Volume 105 of 2022, page 6628 to 6638. The title of the paper is: Effect of feeding fresh forage plantain (Plantago lanceolata) or ryegrass-based pasture on methane emissions, total-tract digestibility, and rumen fermentation of non-lactating dairy cows.
Methane emissions and rumen fermentation characteristics of the dairy cows fed 100% plantain (PLT) or 100% perennial ryegrass (RG; Lolium perenne) were measured in two experiments (E1 and E2). The forages were in a vegetative growth stage in E1 and were in a reproductive growth stage in E2. The CH4 emissions from 16 cows in each experiment were measured in respiration chambers for two days.
Methane emissions per unit of dry matter intake (CH4 yield) were 15 and 28% less for cows fed PLT than those fed RG in E1 and E2, respectively. Dry matter digestibility of PLT was 7 and 27% less than that of RG in E1 and E2, respectively, and CH4 per unit of dry matter digested was similar for PLT and RG in both experiments. There were only minor (but some significant) differences in rumen fermentation characteristics between cows fed PLT and RG in both experiments.
In conclusion, the cows fed plantain forage as the sole diet reduced CH4 production and CH4 yield compared with ryegrass in the two experiments including forages in a vegetative and reproductive stage. Digestibility was less in the cows fed plantain compared with those fed ryegrass, which largely explained the differences in CH4 yield observed between the cows on the two forages. The reduction in CH4 yield of cows fed plantain was not associated with the lower rumen pH, greater production of hydrogen-accepting short chain fatty acids, or forage nitrate concentration, which was initially thought.