Fermented fava bean-based diets & dog cardiac health: does protein content or taurine matter?

The pet food industry has continued major growth for several decades, leading to novel ingredients gaining attention that requires scientific investigation. Fava bean is a pulse largely produced in Canada that, although not yet approved as a pet food ingredient, is a great source of protein, fiber, and starch. Various pulses and legumes are already being used to replace grains in dog diet composition with few issues. Nevertheless, in 2018 the Food and Drugs Administration stated that grain-free diets were linked to dilated cardiomyopathy (DCM) in dogs, but no robust evidence to date has proven this connection. Despite desirable agronomic and nutritional qualities, the fava bean has a fairly high concentration of anti-nutritional factors. In particular, vicine and convicine result in favism in susceptible humans which causes acute hemolytic anemia. Such a condition, however, has not been described in dogs. When processed through cooking, extrusion or fermentation, pulses and legumes can have anti-nutritional factors altered and most often reduced. \n The purpose of this study was to analyze the effects of yeast fermentation of two varieties of fava beans (low or high tannin variety), when used as a pet food ingredient, on dogs’ overall and cardiovascular health as well as nutrient digestibility. Moreover, two commercial diets, grain-free or grain-containing, with different protein levels (24.6% crude protein (CP) on dry matter (DM) basis versus 41.4% CP (DM) on the first study; 31.3% CP (DM) versus 41.4% CP (DM) on the second study), were used as a comparison and the same parameters were evaluated. The first study was a short-term period of seven days of feeding each diet. By the end of each period, blood analyses, cardiovascular testing, and digestibility protocols were performed. As a result, fava bean-based diets did not cause hemolytic anemia in dogs or cause adverse changes in blood chemistry or counts. Thus, fava bean was shown to be safe as a dog food ingredient, at least in the short term. In contrast, after seven days of feeding, the normal protein level, grain-containing commercial diet appeared to cause some cardiovascular alteration that could lead to undesirable cardiac changes in the long term. Also, fermentation of the fava bean flour with Candida utilis prior to use in dog foods presented positive results as a bioprocessing technique that reduced anti-nutritional factors. A 28-day feeding period was examined in the second study and analyzed the same parameters as the first study, with the addition of cardiovascular biomarkers and bile salt content in the feces. The results from the second study demonstrated that even after a longer period, fava bean-based diets did not cause adverse cardiac or vascular alterations. The beagles fed both of the commercial diets and all fava bean-based diets did not show any tendency to develop DCM. Moreover, the high protein, grain-free, commercial diet appeared instead to show improved cardiovascular functioning. Also, fermentation increased energy, nutrient digestibility and red blood cells which are positive effects of this bioprocessing technique. On the other hand, these benefits of fava bean-based diets were counteracted by impaired glucose handling. In conclusion, this thesis shows that yeast fermentation of fava bean flour prior to use in dog foods led to improved health parameters. Also,fava bean appears to be a safe pet food ingredient. Moreover, the commercial grain-free, high protein diet did not cause adverse effects on cardiovascular performance in the resistant beagle breed after a 7 or 28-day period.

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