Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2013
Publication Date: 4/15/2013
Citation: Kokko, C., Soder, K.J., Brito, A.F., Hovey, R.C., Berthiaume, R. 2013. Effect of time of cutting and maceration on forage composition, nutrient flow, microbial protein synthesis, and digestibility in dual-flow continuous culture. Journal of Animal Science. 91:1765-1774. Interpretive Summary: Maceration and evening-cutting are two forage management strategies that have independently improved forage quality and nutrient utilization in ruminants. However, the effects of these combined management techniques have not been evaluated. This study evaluated the combined effects of time of cutting and maceration of a grass-legume hay on ruminal digestion and metabolism in continuous culture. The independent use of evening-cutting improved fiber digestibility and tended to improve dry matter digestibility. Additionally, the tendency for enhanced bacterial-N flows provide in vitro verification that evening-cutting improves N metabolism. Maceration had no effect on nutrient digestibility or N metabolism in vitro. However, significant shifts in the molar proportions of volatile fatty acids were recorded in response to maceration, indicating a shift towards glucose-producing fermentation. The combined use of these management techniques under the conditions of this study afforded no improvement for in vitro digestibility or metabolism when applied to morning-cut hay, but reduced fiber and dry matter digestibilities when applied to evening-cut hay. These findings suggest that while these forage management techniques individually have the potential to increase nutrient utilization and environmental efficiency; there was no benefit in combining them to improve ruminal fermentation.
Technical Abstract: Maceration and evening-cutting are two forage management techniques that have improved forage quality and nutrient utilization in ruminants independently, but have not been evaluated in combination. Using a dual-flow continuous culture fermenter system, this study evaluated the individual and combined effects of both time of cutting and maceration on hay composition, ruminal digestion, nutrient flows, and microbial protein synthesis. Forages were harvested as hay from a mixed timothy-birdsfoot trefoil field at the late bud stage either in the morning (AM) or evening (PM). Half of each morning- and evening-cut treatment was macerated (AM-M, PM-M). Forages were ground to 2 mm and allocated to separate fermenters at 60 g of dry matter (DM)/d in a 4 x 4 Latin square design. Fermenters were operated over 4, 10-d periods with the first 7 d for adaptation followed by 3 d of sampling. Evening-cutting significantly enhanced the apparent digestibility of neutral detergent fiber and acid detergent fiber, and significantly increased total volatile fatty acids (VFA) concentration. Molar proportions of individual VFA were not affected by time of cutting. When expressed as percentage of total N flows, a tendency for increased bacterial N flow and decreased dietary N flow was recorded in evening-cut treatments. Maceration had no effect on nutrient digestibility, however, maceration significantly reduced total VFA concentration and the acetate:propionate ratio. Maceration had no effect on N flows or microbial protein synthesis. A significant time of cutting by maceration interaction was observed where maceration decreased true DM and organic matter digestibilities in evening-cut treatments, but had no effect in morning-cut treatments. Similarly, maceration reduced total N supply and molar proportions of acetate in evening-cut treatments with no effect on morning-cut treatments, while the opposite was found for molar proportions of propionate. These results indicate that independent use of evening-cutting increased fiber digestibility and total VFA concentration, and independent use of maceration shifted molar proportions of VFA towards glucogenic fermentation. The combined use of these management techniques afforded no improvement for in vitro digestibility or metabolism when applied to morning-cut hay and decreased nutrient digestibility when applied to evening-cut hay.