Influence of Pressure Toasting on Starch Ruminal Degradative Kinetics and Fermentation Characteristics and Gelatinization of Whole Horse Beans (Vicia faba) in Lactating Dairy Cows

Abstract

Whole horse beans (Vicia faba cv. Alfred) (WHB) were pressure toasted at different temperatures of 100, 118 and 136°C for 3, 7, 15 and 30 minutes in order to determine an optimal heating conditions to increase bypass starch (BPSt) as glucose source which is usually limiting nutrient in highly producing dairy cows in the Netherlands. Starch (St) Ruminal Degradative Kinetics and Fermentation Characteristics of (SRDC) of WHB were determined using in sacco technique in 4 lactating dairy cows fed 47% hay and 53% concentrate according to Dutch dairy cow requirements. Measured characteristics of St were soluble fraction (S), potentially degradable fraction (D) and rate of degradation (Kd) of insoluble but degradable fraction. Based on measured characteristics, percentage bypass starch (BPSt) was calculated according to the Dutch new feed evaluation system: the DVE/OEB system. Pressure toasting temperatures significantly affected starch gelatinization (p<0.01). Degradability of Starch in the rumen was highly reduced by pressure toasting (p<0.01). S varied from 58.2% in the raw WHB (RWHB as a control) to 19.6% in 136°C/15 min. S was reduced rapidly with increasing time and temperature (p<0.01). D varied from 41.8% in RWHB to 80.5% in 136°C/15 min. D fraction was enormously increased with increasing time and temperature (p<0.01). Kd varied from 4.9%/h in RWHB to 3.4%/h in 136°C/15 min. All these effects resulted in increasing %BPSt from 29.0% in RWHB to 53.1% in 136°C/15 min. Therefore BPSt increased from 93.5 g/kg in RWHB to 173.5 g/kg in 136°C/15 min. The effects of pressure toasting on %BPSt and BPSt seemed to be linear up to the highest values tested. Therefore no optimal pressure toasting conditions could be determined at this stage. But among 10 treatments, The treatment of 136°C/15 min was the best with the highest BPSt content. It was concluded that pressure toasting was effective in shifting starch degradation from rumen to small intestine to increase bypass starch.