Influence of Dry Roasting of Whole Faba Beans (Vicia faba) on Rumen Degradation Characteristics in Dairy Cows, II: Starch

Abstract

Whole faba beans (WFB) were dry roasted at different temperatures of 110, 130 and 150°C for 15, 30 and 45 minutes (min) to determine the optimal heating conditions to increase bypass starch as glucose source which may be a limiting nutrient in high producing dairy cattle. Ruminant degradation characteristics of starch (St) of WFB were determined using in sacco method in 6 dairy cows fed 60% hay and 40% concentrate. Measured characteristics of St were soluble (washable) fraction (S), potentially degradation fraction (D) and the rate of degradation (Kd) of the insoluble but degradable St fraction. Based on measurement of these characteristics, percentage bypass starch (%BSt) and bypass starch (BSt) were calculated. Degradability of starch in the rumen was reduced by dry roasting at temperature of 130 and 150°C and increased at 100°C. S varied from 50.0% in the raw whole faba beans (RWFB) and 53.7% in 100°C/15 min to 18.2% in 150°C/45 min. D varied from 49.9% in RWFB and 46.3% in 100°C/15 min to 81.8 % in 150°C/45 min. Kd varied from 9.8% in RWFB and 11.0% in the 110°C/ 30 min to 4.2 in 150°C/45 min. All these effects resulted in increasing %BSt from 22.1% in the 110°C/45 min and 23.9% in RWFB to 49.9% in the 150°C/45 min. Therefore BSt increased from 91.4 g/kg and 98.4 g/kg to 199.9 g/kg respectively. Dry roasting at 110°C increased the starch rumen degradation. Treatment at higher temperature (130 and 150°C) decreased rumen degradation of starch and seemed to be linear up to highest values tested. No optimal dry roasting conditions of treatment could be determined at this stage. It may be concluded that dry roasting at temperatures of 130 and 15°C was effective in shifting starch degradation from rumen to intestine to increase bypass starch.