Timing of Grazing Termination in Dual-Purpose Winter Wheat Enterprises

Timing of grazing termination is a key management variable in maximizing income from dual-purpose winter wheat enterprises. The objective of this research was to determine the effect of grazing hard red winter wheat pasture past first hollow stem (FHS) on steer BW gain and subsequent grain yield, and to develop production functions relative to time of grazing termination. Grazing trials were initiated at the emergence of FHS on March 13 and 5 of 2003 and 2005, respectively. Angus steers (greater than 7/8 Angus) grazed 4 clean-tilled, dryland winter wheat pastures in 2003 (n = 52; 405 ± 30kg) and a single pasture in 2005 (n = 34; 357 ± 42kg). Forage allowance averaged 199kg DM/100kg BW during 2003 and 133kg DM/100kg BW during 2005. Beginning in early February, grazing exclosures were set at approximately weekly intervals. Body weight of growing steers increased linearly (P < 0.01; Y = 392.2 + 1.58x) following FHS at the rate of 1.58kg/d, and BW gain/ha averaged 147kg over the 2 years. Grain yield responded quadratically (P < 0.01; Y = 2041.8 − 8.28x − 0.51x2) relative to days grazing past FHS. Grain yield decreased 10% by grazing 2 weeks past FHS, and an additional 10% for each of the next two weeks. Although the steers used in this study were heavy, their BW gain was excellent during the post-FHS grazing period, and reductions in grain yield were less than previously reported in the literature. These production functions should aid development of an economic model for evaluating grazing termination decisions in dual-purpose winter wheat enterprises.