Effect of durations of microwave irradiation (3 and 5 min) on truly absorbable nutrient supply of newly developed hulless barley varieties (Hordeum vulgare L.) in comparison with conventional hulled barley variety

Abstract

The objective of this research was to investigate effects of microwave irradiation on truly nutrients supply of newly developed hulless barley varieties in comparison with conventional hulled barley. The barley samples were irradiated with microwave at 900 W with a frequency of 2450 MHz for zero, three and five minutes. The results showed that five-minute microwave irradiation decreased (P < 0.05) the digestibility of rumen bypass or undegraded carbohydrates (dBCHO) and total digestible carbohydrates (TDCHO), increased (P < 0.05) intestinal degradable protein (IDP), and total digestible protein (TDP). In addition, microwave irradiation treatments increased the digestibility of rumen bypass starch (dBST) and intestinal digestible rumen bypass starch (P < 0.05). In contrast to hulled barley, hulless barley had higher (P < 0.01) levels of IDP, TDP, dBCHO, intestinal digestible rumen bypass carbohydrate (IDBCHO), and lower (P < 0.05) TDCHO, dBST and total digestible starch content. Five-minute microwave irradiation increased (P < 0.01) undegradable protein, intestinal truly absorbed undegradable protein, and metabolizable protein (MPNRC), decreased (P < 0.01) intestinal truly absorbed microbial protein (AMCPNRC) and degraded protein balance (OEBNRC). The correlation results showed that the amylose level was positively correlated with IDBCHO (P < 0.05) and negatively correlated with OEBNRC (P < 0.01), AMCPNRC (P < 0.05) and MPNRC (P < 0.10). In conclusion, microwave irradiation could increase the levels of intestinal degradable protein, total digestible protein, intestinal digestible rumen bypass carbohydrates and starch in barley. The predicted truly absorbed protein supply to dairy cattle from barley was improved by microwave treatment and better results were observed with the 5 min treatment duration. In general, hulless barley provided higher truly absorbable nutrient supply to dairy cattle than hulled barley.