title: In situ particle size reduction as affected by forage species and grinding mesh size.
abstract: Two ruminally cannulated heifers were used to evaluate effects of three forage species (gamagrass, orchardgrass, and red clover) ground through two mesh sizes (2 and 5 mm) in a 3 x 2 factorial arrangement on particle size reduction in situ. Residues in polyester bags incubated for 3, 6, 12, 24, 36, 48, 60, and 72 h were analyzed for mean particle size. Initially, gamagrass had a 10.2% greater (P < .05) proportion of DM as particles larger than 300 microns that did orchardgrass or red clover, whereas forages ground through a 5-mm mesh (5-mm forage) had a 7.5% greater (P < .05) proportion of DM as 300 microns or larger particles than forages ground through a 2-mm mesh (2-mm forage). Mean particle size decreased with incubation time, resulting in reductions of 44, 42, 53, and 49% of gamagrass, orchardgrass, and 2- and 5-mm forages, respectively, after 60 h. Mean particle size of red clover was reduced 67% after 36 h of incubation. Particle size reduction was initiated earlier (12 vs 36 h) and occurred at a 150% faster (P < .01) rate for red clover than for gamagrass or orchardgrass. Although there was no difference (P > .10) between grinding mesh size at the time at which particle size reduction was initiated (24 h), particle reduction occurred at a 136% faster (P < .05) rate for forages ground through a 5-mm screen than for forages ground through a 2-mm screen. A greater (P < .10) reduction (595 microns by 36 h) in mean particle size occurred in red clover than in gamagrass or orchardgrass (average 376 microns by 60 h) during ruminal incubation. In addition, 5-mm forages exhibited a greater (P < .10) reduction in mean particle size (527 microns) than did 2-mm forages (372 microns) after 60 h of incubation. Substantial particle size reduction occurred in situ due to microbial digestion. The faster particle size reduction found in red clover may contribute to the greater observed intake for legumes.
authors.affiliation: Department of Animal and Range Sciences, Montana State University, Bozeman 59717, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: Bowman
authors.forename: J L
authors.initials: JL
authors.lastname: Firkins
mesh_terms: D000821:Animal Feed / Q000592:standards*; D000818:Animals; D002417:Cattle / Q000382:microbiology / Q000502:physiology*; D004063:Digestion / Q000502:physiology; D007887:Fabaceae; D005260:Female; D005511:Food Handling / Q000379:methods*; D010316:Particle Size; D010946:Plants, Medicinal; D006109:Poaceae; D012621:Seasons