Steers grazing endophyte-free tall fescue: seasonal changes in nutrient quality, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites.
Six ruminally cannulated Holstein steers (average BW 514 kg) grazed a 33-ha, unirrigated, endophyte-free, tall fescue (Festuca arundinacea Schreb.) pasture from April 10 through December 7, 1989. Samples were collected in May, June, September, and November 1989. Total masticate N was relatively constant (P > .10) throughout the year. Masticate in vitro OM disappearance was less (P < .05) in September (48.4%) and November (50%) than in May (60.6%) and June (56%). Ruminal NH3N concentrations (milligrams/deciliter) were greater (P < .05) during May (20.5) and June (17.8) than during September (9.4) and November (5.9). Organic matter intake (grams/kilogram of BW) and particulate passage rate (percentage/hour) were least (P < .05) in November (15.3; 2.6) and not different (P > .10) during May (23.7; 3.1), June (20.7; 3.1), and September (21.0; 3.0). Extent and rate of NDF digestion and ruminal total VFA did not differ (P > .10) across sampling dates. Serum glucose concentrations were not affected (P > .10) by sampling date, but serum urea N was greater (P < .05) during May and November than during June and September. Nonesterified fatty acid concentrations increased (P < .05) with advancing plant maturity. Serum insulin concentrations were greater (P < .05) during May than during other sampling periods; however, growth hormone concentrations were not altered (P > .10) by advancing plant maturity. Unirrigated fescue pasture maintained a high nutrient level throughout the grazing season, and masticate samples did not display the decrease in nutrient content often noted with other types of pasture forage.
McCracken
B A
BA
School of Veterinary Medicine, University of Nevada, Reno 89557-0104.
Krysl
L J
LJ
Park
K K
KK
Holcombe
D W
DW
Judkins
M B
MB
D000641:Ammonia / Q000032:analysis; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D001806:Blood Urea Nitrogen; D002417:Cattle / Q000097:blood / Q000378:metabolism / Q000502:physiology*; D004043:Dietary Fiber / Q000378:metabolism; D004063:Digestion; D004435:Eating; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005232:Fatty Acids, Volatile / Q000032:analysis; D005285:Fermentation; D013006:Growth Hormone / Q000097:blood; D006854:Hydrocortisone / Q000097:blood; D006863:Hydrogen-Ion Concentration; D007328:Insulin / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D009753:Nutritive Value; D006109:Poaceae; D011897:Random Allocation; D012417:Rumen / Q000737:chemistry / Q000502:physiology*; D012621:Seasons
D001786:Blood Glucose; D004043:Dietary Fiber; D005230:Fatty Acids, Nonesterified; D005232:Fatty Acids, Volatile; D007328:Insulin; D007334:Insulin-Like Growth Factor I; D000641:Ammonia; D013006:Growth Hormone; D006854:Hydrocortisone