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.
School of Veterinary Medicine, University of Nevada, Reno 89557-0104.
B A
BA
McCracken
L J
LJ
Krysl
K K
KK
Park
D W
DW
Holcombe
M B
MB
Judkins
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