Effects of a Single Dose of Direct-Fed Microbials on Performance of Stocker Calves Grazing Annual Cool-Season Grasses1

Effect of species of cool-season annual grass interseeded into Bermudagrass sod on the performance of growing calves

Two experiments were conducted to evaluate the effect of species of cool-season annual grass on the growth of stocker cattle over 3 yr. In Exp. 1, the small grains (SG) oat (O), rye (R), and wheat (W), or combinations of SG and annual ryegrass (RG), were interseeded into Bermudagrass sod in a completely randomized design with a 3 x 2 factorial arrangement of treatments. In Exp. 2, RG was planted alone or with O, R, triticale (T), or W in a completely randomized design. Pastures were planted in late October of each year, and seeding rates were 134.4 and 22.4 kg/ha for SG and RG, respectively. In Exp. 1, grazing was initiated on December 18. In Exp. 2, grazing was initiated on December 23 for SG pastures and January 21 or February 16 for RG pastures in yr 1 and on December 8 for all pastures in yr 2. Grazing was managed using the put-and-take method, in which additional calves were added as needed to maintain equal grazing pressure among pastures. In Exp. 1, no interactions (P > or = 0.28) were detected, so the main effects of SG species and RG addition are discussed. From December 18 to March 12, there were no differences in ADG (P > or = 0.17), whereas during the spring (from March 12 to May 7), addition of RG increased (P = 0.05) ADG. Using RG increased (P < or = 0.01) animal grazing-days/hectare and BW gain/hectare. Wheat tended (P = 0.08) to increase BW gain/hectare compared with the other SG, and O tended (P = 0.09) to produce less BW gain/hectare than the other SG. The treatment x year interaction was significant (P < or = 0.05) in Exp. 2. In yr 1, no differences (P = 0.25) were observed for ADG from December 23 to March 8, but during the spring grazing period (from March 8 to May 5), ADG of calves grazing TRG was less (P < or = 0.04) than that of those grazing RG, RRG, or WRG. The RRG combination produced more (P < or = 0.03) BW gain/hectare than ORG, RG, or TRG and tended (P = 0.06) to produce more BW gain/hectare than WRG. The WRG combination produced more (P < or = 0.05) BW gain/hectare than TRG and RG, and ORG tended (P = 0.09) to produce more BW gain/hectare than RG alone. Pastures planted to R or W produced more (P < or = 0.05) BW gain/hectare than RG alone or T. During yr 2, there were no differences (P > or = 0.44) in ADG, BW gain/hectare, or grazing-days/hectare. In conclusion, the choice of cool-season annual to establish is highly weather-dependent, but R and W are generally superior to other small grains, and RG is a necessary complement to SG when interseeding cool-season annuals into Bermudagrass sod.