Impact of clover additions to toxic or nontoxic endophyte-infected tall fescue on animal performance and economics of stocker programs

During the autumn and spring grazing periods of 4 yr, performance of growing steers grazing six 0.8-ha toxic-endophyte-infected (TE) tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbysh. = Festuca arundinacea Schreb., cv. Kentucky 31; KY31] was compared with the nontoxic-endophyte-infected (NE) tall fescue cultivars Jesup MaxQ (Pennington Seed, Madison, GA; n=6) and Texoma MaxQII (Pennington Seed; n=6) either with N applied in autumn and spring (n = 3 pastures per cultivar) or grown in combination with white clover (CL, Trifolium repens L.; cv. Regal Graze, Producer's Choice, Woodland, CA; n=3 pastures per cultivar). Growing steers (n = 252, BW=228 ± 4.2 kg in the autumn and n=343, BW 229 ± 4.8 kg in the spring) were stocked to pastures at 3.7 steers/ ha in the autumn, whereas initial stocking rates were adjusted to match forage mass each spring. Enterprise budgeting was used to compute net returns. Data in this 3 × 2 factorial arrangement were analyzed as a randomized complete block design using year as the random blocking factor. Performance of steers grazing NE was increased (P < 0.01) by 0.21 kg/d in the autumn and 0.57 kg/d in the spring compared with TE. Clovers did not affect (P = 0.46) ADG in the autumn but increased (P < 0.01) ADG in the spring by 0.2 kg/d; however, stocking rates and grazing days per hectare were decreased (P < 0.01) with CL regardless of season. Interseeding CL into KY31 pastures had no effect (P ≥ 0.41) on BW gain per hectare. Body weight gain per hectare for NE was 79% greater (P < 0.01) than KY31, and NE tall fescue with N produced 17% more (P < 0.01) BW gain per hectare than CL. Neither N nor CL affected (P = 0.41) BW gain per hectare of KY31 pastures. Although CL pastures were not as productive, net returns were increased (P < 0.01) because of reduced costs of production. Using CL resulted in similar improvements in ADG for both TE and NE pastures. Profitability of NE-based stocker programs was at a minimum 3 times greater than TE-based stocker programs in any scenario.