Dietary soyabean oil depresses the apparent digestibility of fibre in trotters when substituted for an iso-energetic amount of corn starch or glucose.

The research study investigates the impact of soyabean oil, corn starch, and glucose on the digestion of fibre in trotters, finding that a high intake of soyabean oil led to a marked decrease in fibre utilisation.

Research Objective

• The study aimed to determine whether previous research on the negative effects of high fat intake on fibre digestion has been underestimated due to the replacement of fat with corn starch. This concern arises from the inability to separate the specific effects of fat and nonstructural carbohydrates, like starch, on fibre digestibility.

Methodology

• The study involved the comparing of iso-energetic amounts of soyabean oil, corn starch, and glucose in terms of their impact on fibre digestibility. It was noted that glucose, unlike starch, is typically fully absorbed by the small intestine and thus would not affect fibre fermentation in the caecum and colon.
• Six trotters were fed rations high in soyabean oil, corn starch, or glucose. These rations followed a 3 x 3 Latin Square design.

Findings

• The results revealed that corn starch and glucose had similar apparent crude fibre digestibility. However, the addition of fat (soyabean oil) markedly decreased fibre digestibility. This effect was consistent for apparent digestibilities of neutral and acid detergent fibre, as well as cellulose.
• These findings led to the conclusion that fat addition to horse feed specifically reduces fibre utilisation, which in turn diminishes the energy provided by dietary fibre.

Implications

• The research findings have critical implications for dietary plans of horses. Incorporating too much fat in the form of soyabean oil could decrease fibre digestibility and subsequently the energy derived from dietary fibre. It encourages a reassessment of the balance between fats and starches in horse diets, suggesting that starch might not have the same constraining impact on fibre digestibility that fat does.