Abstract

Research was conducted to determine subsequent feedlot performance and carcass quality of steers that grazed tall fescue [Lolium arundinaceum (Schreb.) Darbysh.; Schedonorus phoenix (Scop.)] pastures with different endophyte types. Three breed and gender groups of cattle grazed wild-type endophyte-infected (E+), novel endophyte-infected (MaxQ), or endophyte-free (E−) tall fescue pastures for about 100 days. Twenty-four animals (four head/paddock; two paddock replicates/endophyte type) from each of the three groups were transported to a feedlot in Stillwater, OK, after the completion of the grazing phase. At arrival to the feedlot, cattle within pasture replicate were maintained in pens and fed a high-concentrate diet for 112 days in Year 1 and 102 days in Year 2. Live weights of cattle off pasture were 59 kg greater for MaxQ than for E+, and similar to E−. Transit shrink on a percentage basis did not differ among MaxQ and E+ or E−. Rectal temperatures at feedlot arrival and processing were higher for E+ than for MaxQ. In the feedlot, overall average daily gain did not differ among MaxQ and E+ or E−, and averaged 1.99 ± 0.13 kg/day across all treatments. Overall feed efficiency was greater for E+ than for MaxQ. Hot carcass weight was 35 kg heavier for MaxQ than for E+. Other carcass traits did not differ among MaxQ and E+, or MaxQ and E−. Grazing E+ tall fescue decreased gains during the grazing phase that resulted in lighter cattle going into the feedlot, and this weight differential continued after finishing due to similar gains in the feedlot period.

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