Dietary oil rich in polyunsaturated fatty acids for ruminants: Post-ruminal digesta characteristics and their implications on production

Abstract

Maximizing the production of ruminants requires high intakes of feeds that are energy dense, therefore feeds that are usually high in starch. Under these conditions there can be significant passage of partially digested feed starch and fibre to the small intestine. These digesta components interact in a manner that can diminish post-ruminal digestion and absorption. However, in ruminants, the effects of digesta composition on causing physical constraints to digestion and absorption, via increased digesta viscosity have not been given adequate consideration. While elevation of digesta viscosity as a means of reducing rate of nutrient absorption and re-absorption of compounds detrimental to health is a valid approach in humans, digesta viscosity may reduce the production potential of livestock. Thus, there is merit in reviewing the feeding strategies that lead to increased viscosity and how its mitigation can be managed through inclusion of oil in ruminant diets. The interactions between digesta composition and the resultant viscosity with digestive physiology and production factors are examined. This review also highlights the associated benefits of dietary oil for ruminants, such as enhancement of bio-active lipids in ruminant products, health benefits directly to the animal, through decreasing incidence of liver abscesses and effects on production and possibly on the environment (reduction of enteropathogenic bacterial shedding and methane emissions). Key words: Ruminant, starch, digesta characteristics, viscosity, cholecystokinin