SUPPLEMENTAL PROTEIN AND ENERGY FOR BEEF-COWS CONSUMING ENDOPHYTE-INFECTED TALL FESCUE

Effects of energy and protein supplementation of endophyte (Acremonium coenophialum)-infected (E+) and noninfected (E-) tall fescue (Festuca arundinacea Schreb.) on forage intake, digestibility, N now to the sm all intestine, and cow-calf productivity was evaluated in two experime nts. In Exp. 1, 10 ruminally and duodenally cannulated steers were fed either E- or E+ hay with four supplements or E- or E+ hay unsupplemen ted. Four supplements formulated with either cracked corn or soybean h ulls with 100 or 200 g/d of ruminally undegraded intake protein (UIP) were compared. Levels of UIP were varied by adding soybean meal or blo od meal. Hay OM intake was not affected(P >.20) by source of energy or level of UIP; however, intake of. E- was greater (P <.05) than that o f E+. True ruminal OM digestion tended to be greater (P <.12) for stee rs fed 200 g/d of UIP than for steers fed 100 g/ d. Steers receiving 2 00 g/d of UIP had increased (P < .10) total N flow to the duodenum com pared with steers receiving 100 g/d but similar (P >.20) microbial eff iciencies. In Exp. 2, 30 cows (average initial BW 459 +/- 26 kg) and t heir calves (average initial BW 74 +/- 5 kg and 74 +/- 5 d of age) gra zed an 8.1-ha E+ pasture from late May to late July. Cows were individ ually fed supplements used in Exp. 1 each day. Cows that received crac ked corn lost.10 kg/d when fed 100 g/d of UIP but gained.33 kg/d when fed 200 g/d. Cows fed soybean hulls and 100 g/d of UIP gained.07 kg/d, whereas cows provided 200 gld lost .10 kg/d. Calves nursing cows supp lemented with 100 g/d of UIP gained more (P <.08) BW because of increa sed (P <.07) milk consumption and slightly greater (P <.19) forage int ake than calves nursing cows supplemented with 200 g/d of UIP.