Changes in forage quality, ingestive mastication, and digesta kinetics resulting from switchgrass maturity.
Five maturities of switchgrass hay harvested at 14-d intervals (vegetative through 20% heading) were fed to Hereford steers (297 kg) in a 5 x 5 Latin square. Relationships with switchgrass maturity were negative and quadratic (P < .05) for DMI and cubic (P < .05) for digestible DMI. Declines in apparent digestibilities of DM, ADF, and cellulose were cubic (P < .05), whereas these were quadratic (P < .05) for NDF, hemicellulose, and CP. Whole masticates from the least, mid, and most mature hays showed linear (P < .05) declines in DM concentration and IVDMD with increasing maturity, whereas NDF concentrations increased linearly (P < .05). Mean retention time of gastrointestinal DM increased linearly (P < .01) from 64 to 94 h from the least to the most mature hay, and the associated rate of passage declined linearly (P < .01) from 3.3 to 2.1%/h. Sieving of masticate DM showed a reduced proportion of large particles (> or = 2.8 mm) and an increased proportion of small particles (< or = .5 mm) with advancing forage maturity. More than 94% of the sieved fecal DM passed a 1.0-mm sieve, but particle sizes showed the same relationship with forage maturity as noted for masticate DM. This occurred despite the comminution from the rumination and digestive processes.
Burns
J C
JC
USDA-ARS, Crop Science Department, North Carolina State University, Raleigh 27695, USA.
Pond
K R
KR
Fisher
D S
DS
Luginbuhl
J M
JM
D000821:Animal Feed / Q000592:standards*; D000818:Animals; D015415:Biomarkers; D002417:Cattle / Q000502:physiology*; D002482:Cellulose / Q000378:metabolism; D002857:Chromium / Q000032:analysis; D004043:Dietary Fiber / Q000378:metabolism / Q000592:standards; D004063:Digestion / Q000502:physiology*; D004068:Digestive System Physiological Phenomena; D005285:Fermentation; D008297:Male; D008409:Mastication / Q000502:physiology*; D009753:Nutritive Value; D010316:Particle Size; D006109:Poaceae / Q000378:metabolism*; D011134:Polysaccharides / Q000378:metabolism; D013997:Time Factors; D015018:Ytterbium / Q000032:analysis
D015415:Biomarkers; D004043:Dietary Fiber; D011134:Polysaccharides; D002857:Chromium; C007916:hemicellulose; D002482:Cellulose; D015018:Ytterbium