Effects of different processing methods of flaxseed on ruminal degradability and in vitro post-ruminal nutrient disappearance.

The aim of the study was to determine the effects of different heat-processing methods of flaxseed on thein situeffective dry matter degradability (EDMD) and thein situeffective crude protein degradability (ECPD). The treatments included roasting, steep roasting, rolled roasting, rolled steep roasting, microwave irradiation and extrusion. Three rumen-fistulated sheep were used forin situincubations. Furthermore, the effects of heat-processing methods on post-ruminalin vitronutrient disappearance and total tract disappearance were measured by a three-stepin vitrotechnique. The seeds were roasted and extruded at 140°C to 145°C. One lot of roasted seeds was gradually cooled for about 1 h (roasting) and another lot was held in temperature isolated barrels for 45 min (steep roasting). Moreover, roasted and steep roasted flaxseed was rolled in a roller mill. The lowest and highest EDMD was observed for unheated and extruded flaxseed, respectively (p < 0.05). The highest ECPD was observed for extruded flaxseed (p < 0.05). Roasting and microwave irradiation reduced ECPD of flaxseed (p < 0.05).In vitropost-ruminal disappearance of crude nutrients including fibre fractions was highest for rolled-roasted and rolled steep-roasted flaxseed (p < 0.05). The lowest and highest total tract disappearance rates of crude nutrients and fibre fractions were estimated for unheated and extruded flaxseed, respectively (p < 0.05). The post-ruminal disappearance of crude nutrients was also increased by roasting, in which rolling enhanced this effect. In conclusion, all investigated heat treatments had significant effects onin situandin vitrodegradability of nutrients. As well, rolling of roasted flaxseed enhanced the respective effects. Therefore, different methods of heat processing can be used to modify the feed value of flaxseed for specific purposes. [ABSTRACT FROM AUTHOR]