HEATING RAW VELVET BEANS (Mucuna pruriens) REVERSES SOME ANTI-NUTRITIONAL EFFECTS ON ORGAN GROWTH, BLOOD CHEMISTRY, AND ORGAN HISTOLOGY IN GROWING CHICKENS

Abstract

"Velvet beans (Mucuna pruriens) represent an interesting food and feed commodity because of the presence of harmful, but also potentially beneficial components that have been poorly studied. We developed a joint research project between the University of Vermont in the USA and the Escuela Agricola Panamericana (Zamorano) in Honduras to study the role of velvet beans (VB) in chicken nutrition and to determine methods for improving their usefulness and safety. The results of these studies, using the chicken as a research model, have application to all monogastric animals including humans with whom such research cannot be done. The two experiments described herein measured the effects of raw VB on the anatomy and blood chemistry of the chick, and the role that heating the velvet beans has on reversing any harmful effects inherent in the beans themselves. Consumption of unprocessed, raw velvet beans by broiler chickens reduced body weight gain. Weights (relative to body weight) of the pancreas, gizzard, and proventriculus (stomach), as well as lengths of the small and large intestines, and ceca, increased in birds fed raw VB. Most of these changes were partially or wholly reversed by dry heating (i.e. toasting) the beans. It is likely that the effects of heating reflect, to some degree, partial destruction of anti-nutritional factors. Effects of VB on liver and heart weights were inconclusive. Significant changes were also found in blood components. Plasma creatinine was reduced to a similar degree in chicks fed both raw and heated VB, and most likely reflects changes in muscle mass or metabolism concurrent with feeding either form of VB. Plasma cholesterol levels were also consistently reduced in chicks fed raw VB compared to their pairfed controls. These findings agree with our previous results and work done by others in a rat model. However, heating VB caused an even further reduction in plasma cholesterol. This may indicate the presence of a cholesterol-lowering substance in VB. Some antinutritional factors in VB may be heat-resistant and may explain such effects, although the effect of dietary fiber cannot be ruled out. Alanine aminotransferase was elevated in chicks fed both raw and heated VB compared to their pair-fed controls, and this is often an indication of liver damage. Intake of raw VB had inconsistent effects on plasma thyroxine and triiodothyronine, and little effect on the plasma content of sodium, glucose and alkaline phosphatase. The microanatomy of the pancreas, liver, smallintestine and kidney was altered in chickens fed raw VB. Increases in pancreatic necrosis, hepatic cellular degeneration and thinning of the mucosal muscular layer of the small intestine appeared to be at least partially a consequence of the reduced growth rate, as shown by pair feeding comparisons, and not to the VB themselves. However, kidney damage, as shown by invasion of blood into the renal tubules, was directly a result of feeding raw VB. Heating"