Capric and lauric acid mixture decreased rumen methane production, while combination with nitrate had no further benefit in methane reduction

Abstract

This study aimed to evaluate the methane-reducing potential of individual and combined treatments of low levels of nitrate (NIT) and a mixture of capric/lauric acid (CL) in dairy cows. Both in vitro and in vivo experiments were conducted. In the in vitro experiment, the anti-methanogenic effects of NIT (1.825 mmol/l) and CL (250 mg/l; capric acid, 125 mg/l + lauric acid, 125 mg/l) were evaluated in a 2 × 2 factorial design using consecutive batch incubations with rumen fluid. The NIT and CL reduced (P<0.05) methane production by 9.2% and by 21.3%, respectively. However, combining NIT with CL did not show (P>0.05) any benefit in methane reduction compared to the use of CL alone. In in vivo experiment, eight multiparous dry Holstein cows were fed two diets in a crossover design for two 21-day periods (14 days of adaptation and 7 days of sampling). The treatments were: 1) silage-based basal diet + 100 g stearic acid per cow/d (CON) and 2) silage-based basal diet + 50 g capric acid + 50 g lauric acid per cow/d (CL). Gas emissions were measured using open-circuit respiration chambers. Methane production (g/d) was reduced (by 11.5%; P = 0.012) when the diet was supplemented with CL. However, supplementation with CL increased ruminal ammonia-N concentration (by 28.5%; P = 0.015) and gas ammonia production (g/d; by 37.2%; P = 0.005). Ruminal pH, protozoa count, and total and individual volatile fatty acid concentrations (VFA) did not differ (P>0.05) between the treatments. Treatment did not affect the intake and total tract apparent digestibility (P>0.05). In conclusion, our results suggest that low CL levels have anti-methanogenic potential. However, low levels of CL may compromise nitrogen use efficiency.

Insights into Effects of Combined Capric and Lauric Acid on Rumen Bacterial Composition

“…At the kingdom level, the relative abundances of bacteria and archaea ( Table 1 , Figure 4 ) were not altered by the treatment, which is in line with other studies on MCFA in the rumen [ 8 , 23 ]. The lack of an effect on the relative abundance does not align with our previously reported decrease in methanogenesis (−11.5%) from these animals [ 14 ]. However, there have been reports of reduced methanogenesis (and methanogen activity) with no change in the methanogen number [ 24 ].…”

“…A greater abundance of Firmicutes indicates a more feed-efficient animal [21,31] with improved structural polysaccharide degradation [32]. Changes in this ratio did not affect digestibility, and we could not assess its effect on production parameters, because the animals in our study were dry cows [14]. The dominant bacterial phyla in both the control and treatment groups were Bacteroidota and Firmicutes (Figure 2A), which is consistent with most ruminant studies [20,27].…”

“…In a previous study, we reported the effects of C10 + C12 on gas production and rumen fermentation characteristics [ 14 ]. In summary, the supplementation of C10 + C12 in vivo decreased CH 4 production by 11.5% but increased rumen ammonia-N (NH 3 -N) concentrations (+28.5%) and ammonia gas emissions (+37.2%).…”

“…Detailed information about the cows and their feeding was reported in our previous study [ 14 ]. Briefly, eight multiparous dry Holstein cows were randomly assigned to two groups with two dietary treatments in a cross-over design and allowed to acclimate for 17 d before rumen sample collection.…”

“…The exact effect of the combination of C10 + C12 on ruminal bacteria has not been described and, to the best of our knowledge, has not been fully confirmed. In our previous study, with Joch et al [ 14 ], we described the effects of C10 + C12 on rumen fermentation, gas production, and protozoa counts in vivo. The present study aimed to expand upon these findings and used next-generation sequencing to evaluate the effects of C10 + C12 on ruminal bacteria.…”