Changing the Proportions of Grass and Grain in Feed Substrate Impacts the Efficacy of <i>Asparagopsis taxiformis</i> to Inhibit Methane Production <i>in Vitro</i>

Abstract

Benefits of the red seaweed Asparagopsis taxiformis as an ingredient to manage methane (CH 4 ) emissions from the red meat and dairy industries continue to evolve. Asparagopsis has been demonstrated to eliminate enteric CH 4 emissions in vitro and reduce it greater than 80% in animals. Variability in animal studies is suspected to be associated with variable inclusion and proportions of grass and grain in the diet. This in vitro study aimed to elucidate effects of gradient grass to grain proportions in the fermentation using five steps from 100% Rhodes grass (RG) to 100% barley grain (BG). Gradient inclusion of Asparagopsis was in six steps of Control with no inclusion (C), Low (L), Low-Medium (LM), Medium (M), Medium-High (MH), and High (H) levels tested in three fermentation durations (24 h, 48 h, 72 h). There was significant effect of RG/BG and inclusion of Asparagopsis such that CH 4 production decreased with increasing Asparagopsis independent of RG/BG; however, there was enhanced reduction at greater proportions of BG. Thus, the level of Asparagopsis required to completely inhibit CH 4 production in vitro was decreased with decreasing RG/BG. Increasing the duration of fermentation had greatest effect on CH 4 at C, L, and LM levels of Asparagopsis independent of RG/BG, although magnitude of CH 4 production was greater for higher proportions of BG for the C and L levels. Digestibility of in vitro substrate increased with fermentation duration and increasing BG; however, there was no change associated with inclusion levels of Asparagopsis.

Exploration of Methane Mitigation Efficacy Using <i>Asparagopsis</i>-Derived Bioactives Stabilized in Edible Oil Compared to Freeze-Dried <i>Asparagopsis in Vitro</i>

“…Increased production of butyrate, on the other hand, was not expected to increase with Asparagopsis inclusion. This study shows significant increases in butyrate production and is consistent with previous studies using FD-Asp at different inclusion rates in vitro [18] [19]. It has been suggested that when [H] increases in the rumen, some bacterial populations can incorporate [H] when forming butyrate from pyruvate, thus would provide an additional [H] sink in the rumen [38].…”

“…To that end, this study demonstrated that both FD-Asp and Asp-Oil have no negative impacts on IVDDM with complete inhibition of CH 4 . In addition, decreases in acetate with concomitant increases in propionate and subsequent reduction in acetate:propionate have been consistently demonstrated with FD-Asp in vitro [18] [19] [20] and now with Asp-Oil. The phenomena were also observed with FD-Asp in vivo [3] [25] and consistency between FD-Asp and Asp-Oil in this study is a strong indicator that Asp-Oil will behave in the same way as FD-Asp in vivo.…”

“…Total gas production (TGP) and CH 4 production were determined using Ankom-RF gas production technology (Macedon, NY, USA) with protocols and parameters as described by reference [18]. The Ankom in vitro system measures TGP by recording cumulative gas pressure and pressure release at the maximum pressure set point of 3 psi, and recorded as cumulative pressure every 20 minutes, for the duration of the experiment.…”

“…Alternatively, FD-Asp was also tested in vitro using Rhodes grass substrate with decisive results [8] [9] and subsequently, FD-Asp demonstrated excellent efficacy in vivo in high grain TMRs [3] [4]. It has been demonstrated that changing the proportion of grass to grain in feed formulations has significant impact on the in vitro antimethanogenic efficacy in favor of increasing the grain content, however complete CH 4 inhibition was demonstrated independent of diet formulation [18]. The preceding studies provide confidence that Asp-Oil antimethanogenic efficacy can be translated to all diet formulations albeit with variability in the MEIL influenced by grass and grain proportions.…”

“…It has been hypothesized that large reductions in enteric CH 4 emissions can negatively impact digestibility, mainly due to a buildup of metabolic hydrogen ([H]), in the rumen which in turn has a negative impact on acetate production, the main VFA resulting from fiber digestion [36] [37]. Conversely, previous research has consistently shown that the addition of FD-Asp has no effect on IVDDM [8] [9] [18]. However, an objective of the current study was to determine the comparative impacts of Asp-Oil on IVDDM since the oil carrier itself can impact digestibility and fermentation of substrates in the rumen [28].…”