Omnivores versus carnivores: Can higher levels of pulse starch be tolerated in a wider range of species than corn?

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Carbohydrates are poorly tolerated in carnivorous species, while omnivores tend to tolerate higher dietary levels. However, since protein is often the costliest portion of an animal feed, maximizing the amount of carbohydrate produces a more economical feed. In order to balance these contradictory needs, this proposal aims to explore the use of slowly digestible pulse starches (pea, lentil, faba bean) compared to a more standard carbohydrate source such as corn starch. The slower digestibility of pulse starches are hypothesized to produce lower glycemic index, lower insulin levels and fewer adverse health effects compared to the rapid digestibility and higher glycemic index of corn starch. We predict that the health benefits of using pulse starches will be particularly pronounced in carnivorous species compared to omnivorous species. This prediction is based on the fact that carnivorous species tend to have lower amylase and are predicted to transport glucose to a lesser extent, both from the intestine and disposal into liver or muscle from the bloodstream. Carnivorous species are also predicted to produce higher levels of the reactive glucose metabolite, methylglyoxal, due to lower levels of key glycolytic enzymes which will in turn lead to higher levels of oxidative stress and inflammation compared to omnivores. In order to investigate these hypotheses, we will compare the carnivorous species, cat and rainbow trout, to omnivorous species, dog and tilapia in their ability to digest carbohydrate, glycemic responses to single feedings and health effects in longer-term feeding trials. Furthermore, since feeds for all of these species, both pet and aquaculture, are usually sold in a dry pelleted form, further understanding of how extrusion conditions affect starch structure and digestibility is needed before the full marketing potential of pulses can be realized. With this new, scientifically-supported information for the marketing of pulses, our industry partners will be able open new aquaculture markets and expand existing pet food markets, not only in North America, but also in Europe and Asia.