Intensively processed silage using Bio-extruder : effects on gas production and forage digestibility

Sammanfattning: The dairy cow requires a high feed intake to maintain a high milk production and forage is a crucial component in dairy cows diet. Forage stimulates chewing activity and rumination which contributes to a normal and effective rumen function. However, the forage intake is limited due to a high fibre content and large particle size, compared to concentrate. A reduced particle size of the forage has been shown to increase the forage digestibility and enable an increased forage intake. The objective of this study was to investigate if intensive physical treatment of forage can increase the in vitro digestibility. Primary growth of timothy and red clover silage, harvested at two maturity stages (early and late), were processed using a Bio-extruder. A study was conducted using a gas in vitro system with liquid displacement to continuously measure the gas production from the silage, as indicative of digestibility. The gas production was measured during four incubations, two with timothy and two with red clover. The incubations included triplicates of each sample, hence in total six repli-cates of each forage and treatment combination were incubated. Each incubation lasted for 72 hours and the gas production was evaluated for the main effects, extrusion, crop and maturity as well as for their interactions. After the incubation, the fer-mented residues were treated with neutral detergent solution to estimate the digestion of neutral detergent fibre. The result showed a significantly higher gas production for processed timothy and red clover compared to control silage where the largest difference occurred between 6 – 24 hours incubation. The NDF residue from processed silage was significantly lower compared to control silage for late harvested timothy and early harvested red clover. It was concluded that, there are possibilities to increase the forage digestibility by intensive physical treatment using a Bio-extruder. How the forage intake and milk production are affected by feeding dairy cows intensively processed forage need to be investigated further.