A Rumen Bioreactor for In-vitro Evaluation of Bloat Mitigation Agent
Year: 2024
Type: dissertation
Abstract: Frothy bloat is a common problem in ruminants grazing lush leguminous pasture, promoting rapid fermentation and forming frothy foam, resulting in gas trapping in the rumen. Uncontrolled bloat may lead to the death of the affected animals as it puts internal pressure on the vital organs lying close to the rumen. In New Zealand, bloat is a common problem, costing farmers millions of dollars annually in animal deaths, lost production and additional labour costs. Current practices in bloat management, including pasture control and anti-foaming agents, are not completely effective. Anecdotal evidence and unpublished research suggest that supplementing ruminant animals with low-moisture feed lick blocks (LMFLs) made of cooked molasses improves animal productivity and reduces bloat risk. However, this has not been systematically evaluated before, and the mechanism by which supplementation mitigates ruminal bloat and its effect on metabolic products of rumen fermentation and gas production are unknown. This thesis studied the anti-bloating properties of two formulations of Crystalyx® LMFLs (Cattle Booster™, CB and Extra High Energy™, EHE) in an in-vitro setting. An instrumented bioreactor was constructed to mimic anaerobic rumen fermentation with real-time monitoring of pressure and gas composition (carbon dioxide and methane). Rumen fluid from fistulated cows was incubated in the bioreactor for 24 hours with either alfalfa, white clover, ryegrass or 65 % alfalfa pellet (65 % AP) in the presence and absence of CB and EHE. Following this, froth was induced in the bioreactor contents by bubbling carbon dioxide using an in-house froth induction apparatus. Foam height, strength and stability were measured. The leguminous substrates had higher mean crude protein (CP) and soluble protein contents than ryegrass (P <0.001) and, consequently, higher foam volume and strength. Furthermore, the Polysaccharide slime content in these leguminous substrates was higher than in ryegrass. However, LMFLs- Crystalyx® addition to incubate mixtures reduced the in vitro foam volume (P = 0.001; n =3) and increased the foam instability (P = 0.028 for EHE, n =3) in white clover. Biofilm complexes in alfalfa (P <0.001) and white clover incubates were also reduced (P < 0.015 for CB; P < 0.025 for EHE). The surface tension of the LMFL products was measured using a tensiometer, and it was found that both CB and EHE reduced the surface tension of the rumen fluid by about 60 % (p < 0.001; n =3). The presence of sugar esters of fatty acids that have surfactant properties was tested using the ferric hydroxamate test, and it was found that both LMFLs contain millimolar concentrations of the esters (1.02 ± 0.01 mM CB, 1.24 ± 0.03 mM EHE; n =3). These results provide a mechanistic explanation for the reduction in foam volume and strength caused by the LMFLs. Gas production and the chemical composition of fermentation products were profiled. It was found that the addition of Crystalyx® products increased gas production at 24 hours by 18 % (p = 0.035, n= 3) and 19 % (p = 0.002, n= 3) in alfalfa and 65 % AP, respectively. However, the proportion of carbon dioxide and methane was not altered. The total VFA concentrations in all substrate feeds ranged between 0.46 ± 0.03 - 4.46 ± 0.1 mmol/ 0.5 g DM under control conditions. Crystalyx® addition increased (P < 0.001; n =3) the concentrations to 2.87 ± 0.04 - 10.92 ± 0.32 (CB) and 6.32 ± 0.24 - 12.0 ± 1.0 (EHE). Crystalyx® EHE significantly (P < 0.001; n =3) reduced the acetate:propionate (A/P) ratio in alfalfa (4.10 ± 0.12 to 2.12 ± 0.15 mmol/ 0.5 g DM) and 65 % AP (P = 0.034, n = 3, 4.16 ± 1.7 to 1.32 ± 0.02 mmol/ 0.5 g DM). In white clover, however, both Crystalyx® types increased (P < 0.001; n =3) the A/P ratio (1.51 ± 0.11 to 2.06 ±0.11 mmol/ 0.5 g DM for CB, 1.51 ± 0.11 to 5.2 ± 0.79 mmol/ 0.5 g DM for EHE). The increase in the A/P ratio in ryegrass was observed due to Crystalyx® CB addition (1.0 ± 1.02 to 2.20 ± 0.17). Crystalyx® LMFLs also reduced NH3-N levels in alfalfa by 57% (p < 0.001; n = 4) and 65 % AP by 15% (p < 0.001; n = 4) and pH levels in alfalfa (7.15 to 6.15; n = 3), white clover (7.45 to 6.27; n = 3), ryegrass (7.3 to 6.3; n = 3) and 65 % AP (6.9 to 6; n = 3). The studies reported here confirm that in an in vitro setting, Crystalyx® LMFLs have an anti-bloating effect. The mechanism is the reduction in surface tension due to the surfactant activity of sugar esters of fatty acids. The results also suggest that Crystalyx® LMFLs alter microbial activity and biomass to enhance fermentation. Microbiome and animal studies are needed to understand the results better and confirm their applicability on-farm.
Author: Woju, Chernet W.
Language: English
Subfield: Animal Science and Zoology
Domain: Life Sciences
SDG: Zero hunger
Open Access status: green
OpenAlex ID: W7061809996