ARS | Publication request: Can the Heat of Ruminal Fermentation be Manipulated to Decrease Heat Stress?

Submitted to: Proceedings of the Southwest Nutrition Conference
Publication Type: Proceedings/Symposium
Publication Acceptance Date: January 23, 2007
Publication Date: February 22, 2007
Citation: Russell, J.B. 2007. Can the Heat of Ruminal Fermentation be Manipulated to Decrease Heat Stress?. Proceedings of the Southwest Nutrition Conference. 22:109-115.

Technical Abstract: The most straightforward way of decreasing the heat of fermentation is to bypass ruminal fermentation altogether. This strategy can be achieved by using feed materials not degradable the rumen or treating feeds so there is a greater escape or by-pass to the lower gut. Fatty acids arising from triglycerides or phospholipids hydrolysis can be biohydrogenated by ruminal bacteria, but the fatty acids are not degraded or fermented per se. Fatty acids can be protected from the rumen by treating them with calcium and magnesium, and some starch sources are encapsulated by proteins (e.g. zein) that are not readily hydrolyzed unless heat is provided as a feed treatment. By using starch sources that are not heat treated, it is possible to increase ruminal escape, but ruminants have a limited capacity to digest starch in intestines. Post ruminal starch fermentation can also cause a variety of problems that include diarrhea, laminitis and an over-growth of Escherichia coli. Another avenue of enhancing the flow of feed to the lower gut is particle size reduction, but this approach may also decrease fiber digestibility. Because maintenance, energy spilling and even growth are all heat generating processes, the ability of nutritionists to manipulate the heat production of ruminal microorganisms is very limited. Given these constraints, the most effect means of decreasing the heat of ruminal fermentation is to decrease food intake.