Effects of partial or total replacement of corn cracked grain with high concentrations of crude glycerin on rumen metabolism of crossbred sheep

Abstract

Crude glycerin, a by-product of the biodiesel industry, has been used as a strategic ingredient in intensive ruminant production systems, mainly in substitution of starch-rich ingredients. The present study was performed to evaluate the effects of the inclusion of up to 30% of crude glycerin in diets for feedlot sheep, on ruminal parameters, such as pH, NH 3-N and volatile fatty acids concentrations, in situ degradability, as well as in vitro greenhouse gas production and in vitro digestibility. Eight ruminally-cannulated male Santa Inês × Dorper sheep (64.5 ± 8.5 kg) were distributed in a replicated 4 × 4 Latin square design. The experimental diets contained 0, 10, 20 or 30% of crude glycerin and were labeled as G0, G10, G20 and G30, respectively. The crude glycerin totally replaced the corn cracked grain in treatment G30. The inclusion of crude glycerin in the diets tended to promote a quadratic effect in DMI, with greater values observed for treatments G10 and G20. Crude glycerin tended to increase the ruminal pH and NH 3-N, but linearly reduced the total molar concentration of VFA, acetic, butyric, isobutyric and isovaleric acids. Treatments linearly increased in vitro DM digestibility of diets and linearly reduced NDF digestibility. The inclusion of crude glycerin in the diets linearly decreased the in vitro total gas and CO 2 production (mL/g degraded) and tented to reduce CH 4 (mL/g degraded). A linear increase of soluble fraction in water ("a") of the diets was observed with the increasing inclusion of crude glycerin. The insoluble but potentially degradable fraction ("b") of DM and NDF of the diets were linearly decreased and increased, respectively. The potential ruminal degradation of the diets was markedly and linearly increased with the increasing inclusion of the by-product. The replacement of corn cracked grain by crude glycerin (up to 30% DM) changes rumen fermentation parameters, decreasing VFA production, in vitro total gas production and CH 4. Additionally, the potential and effective degradation as well as in vitro DM digestibility of diets are improved while fiber digestibility is impaired.

Combining Crude Glycerin with Chitosan Can Manipulate In Vitro Ruminal Efficiency and Inhibit Methane Synthesis

“…In addition, Saleem et al [26] reported enhanced fiber digestion with supplemental glycerin. Furthermore, van Cleef et al [6] concluded that the effective degradation and the in vitro DM digestibility of diets were improved when crossbred sheep were fed a partial or total replacement of corn cracked grain with crude glycerin at high doses. However, Abu Ghazaleh et al [4] noted that glycerin addition decreased in vitro NDF digestion due to the decreasing bacterial counts associated with feed digestibility.…”

“…This likely occurred because crude glycerin, which is similar to a fermentable carbohydrate source, underwent ruminal fermentation to C3. Van Cleef et al [6] noted that the change in the relative C3 ratio was probably due to the fermentation properties of crude glycerin, which is fermented mainly by Selenomonas bacteria and mostly used by ruminants during the first 4-6 h after digestion. Almeida et al [29] found the higher ratio of crude glycerin (~43%) is quickly absorbed by the rumen wall, whereas 25% to 45% is converted to C2 and C3 by an alternative fermentative route (via succinate) and does not produce lactic acid, thus advancing the rumen's maturation and enhancing diet use.…”

“…Lee et al [5] indicated that supplemental glycerin reduced CH 4 formation in alfalfa and corn by 25.2% and 14.8%, respectively, thus reducing the methanogenic potential of forages, so the addition of glycerin might be an influential means of inhibiting ruminal CH 4 formation. Similarly, van Cleef et al [6] indicated the added possibility of glycerin decreasing CH 4 synthesis and negatively affecting microbial synthesis and feed digestion. However, the studied results differed in that they indicated no change in CH 4 production when supplemented with glycerin [7].…”

Inclusion of Crude Glycerin in Diets for Sheep

“…However, several in vivo and in situ studies have reported increases in total VFA production [34,[41][42][43]. Differently, other authors evaluating the increasing inclusions of crude glycerin in diets for crossbreed lambs (up to 30% DM, in [28,44]) and Nellore bulls (up to 30% DM, [36]) observed a linear decrease in total VFA with no changes in propionic acid concentration. However, a pronounced reduction in acetic acid concentration was observed.…”

“…Most of them are related to the end products of glycerol fermentation and its effects on ruminal microorganisms. However, promising results regarding growth performance and feed efficiency have been reported for inclusion up to 20% of crude glycerin in diets for feedlot lambs [26][27][28]. Therefore, this chapter discusses important aspects of different inclusions and associations of crude glycerin, including glycerol digestibility and metabolism and practical applications in sheep nutrition and production.…”