Monocyte immune cell response and copper status in beef steers that grazed endophyte-infected tall fescue.
A 3-yr study was conducted to evaluate immune response and Cu status of yearling beef steers as a consequence of grazing tall fescue (Festuca arundinacea Schreb.) infected (E+) with the endophyte fungus Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). During a preliminary study in 1994, 24 weanling Angus and Angus x Hereford steers were blocked by breed and weight (initial BW 271 kg; SD 25) and were randomized to E+ and low endophyte (E-) fescue in pastures at Glade Spring, VA. Grazing began in April and was discontinued in July. In 1995 and 1996, 24 weanling Angus and Angus x Hereford steers (initial BW 249 kg, SD 20 and 240 kg, SD 15, respectively) were randomized to the E+ and E- pastures at Glade Spring during each year. Grazing began in April and continued until September in 1995 and October in 1996. In 1994, steers that grazed E+ fescue exhibited lower (P < .05) phagocytic activity, major histocompatibility complex (MHC) class II expression, ceruloplasmin, and serum Cu than steers that grazed E- tall fescue. During 1995, steers grazing E+ fescue had lower (P < .05) phagocytic activity and MHC class II expression than steers that grazed E- fescue. In 1996, one-half of the steers within each paddock received a Cu oxide bolus at the beginning of the grazing season. During 1996, phagocytic activity was lower (P < .01) and MHC class II expression tended (P < .07) to be lower in steers that grazed E+ tall fescue than in steers that grazed E- tall fescue. Copper supplementation increased (P < .05) MHC class II expression in July regardless of endophyte status over nonsupplemented steers. Steers that grazed E- tall fescue had higher (P < .05) plasma or serum Cu concentrations than steers that grazed E+ tall fescue in each year of the study. These data indicate that the endophyte compromised the immune function of grazing steers, and the data suggest a relationship with depressed Cu status.
Saker
K E
KE
Department of Large Animal Clinical Sciences, Virginia-Maryland Regional College of Veterinary Medicine, Blacksburg 24061-0442, USA.
Allen
V G
VG
Kalnitsky
J
J
Thatcher
C D
CD
Swecker
W S
WS
Fontenot
J P
JP
D000164:Acremonium / Q000502:physiology*; D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000097:blood / Q000276:immunology*; D002570:Ceruloplasmin / Q000032:analysis; D003300:Copper / Q000097:blood*; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis; D008297:Male; D009000:Monocytes / Q000276:immunology*; D010587:Phagocytosis; D006109:Poaceae / Q000382:microbiology*; D011897:Random Allocation
D000949:Histocompatibility Antigens Class II; D003300:Copper; D002570:Ceruloplasmin