Influence of Dry Roasting on Rumen Protein Degradation Characteristics of Whole Faba Bean (Vicia fada) in Dairy Cows

Abstract

Whole faba beans (WFB) were dry roasted at different temperatures (110, 130, 150°C) for 15, 30, 45 minutes to determine the optimal heating conditions of time and temperature to increase nutritional value. Ruminant degradation characteristics of crude protein (CP) of WFB were determined by the nylon bag incubation technique in dairy cows fed 60% hay and 40% concentrate. Measured characteristics of crude protein (CP) were soluble (washable) fraction (S), undegradable fraction (U), lag time (T0), potentially degradable fraction (D) and the rate of degradation (Kd) of insoluble but degradable fraction. Based on measured characteristics, percentage bypass crude protein (%BCP) and bypass crude protein (BCP in g/kg) were calculated. Degradability of CP was reduced by dry roasting (p < 0.01). S was reduced rapidly with increasing time and temperature, from 49.0% in the raw WFB (RWFB) to 26.3% in 150°C/45 min. D varied from 50.7% in RWFB to 73.7 % in 150°C/45′. U varied from 0% in 130°C/45′, 150°/30′ and 150°/457prime; to 0.66% in 110°/45′ (0.24% for the RWFB). Lag time (T0) varied from 1.58 h in 130°C/ 30′ to 2.40h in 150°C/45′ (1.87 h for RWFB). Kd varied from 24.2% in the 110°C/30′ to 4.3% in 150°C/45′ (21.4% for the RWFB). Kd was significantly reduced with time and temperature. All these effects resulted in increasing % BCP from 8.9% in the 110°C/15′, 11.3% in the RWFB to 43.1% in the 150°C/45. Therefore BCP increased from 31.3 and 39.9 to 148.4 g/kg respectively. Both %BCP and BCP at 150°C/45 increased nearly 4 times over the raw faba beans. The effects of dry roasting temperature and time on %BCP and BCP seemed to be linear up to the highest values tested. Therefore no optimal dry roasting conditions of time and temperature could be determined at this stage. It was concluded that dry roasting was effective in shifting crude protein degradation from rumen to intestine to reduce unnecessary nitrogen (N) loss in the rumen. To determine the optimal treatment, the digestibility of each treatment should be measured in the next trial using mobile bags technique.