|Horn, G - OKLAHOMA AGRICULTURAL EXP|
Submitted to: American Society of Animal Science Southern Section Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 6, 2007
Publication Date: February 4, 2008
Citation: Phillips, W.A., Northup, B.K., Venuto, B.C., Horn, G.W. 2008. Impact of substituting perennial cool-season grasses for winter wheat on stocker performance [abstract]. American Society of Animal Science Southern Section Meeting. 86(1):15. Interpretive Summary: Abstract only
Technical Abstract: Winter wheat pasture is the primary forage resource for grazing stocker calves in the southern Great Plains. However, wheat (Triticum aestivum L.) is an annual and must be established each fall. The objective of this experiment was to compare the productivity of grazing systems based on a combination of wheat and perennial cool-season grasses (PCSG) with a system based on wheat pasture only. A total of thirty six 2-ha plots of tall wheatgrass (Elytrigia pontica var. ‘Jose’), smooth brome (Bromus inermis var. ‘Lincoln’), intermediate wheatgrass (Thinopyrum intermedium var. ‘Manska’) and winter wheat (var. Pioneer 2174) were grazed each fall (N=3). Plots received 45 kg of N/ha each fall and were used as the experimental unit. Grazing was initiated on Nov. 15 ± 3 d. Plots of PCSG were grazed for 37 ± 6.5 d at a stocking rate of 0.5 ha/calf. Wheat plots were gazed for 40 ± 6.5 d at a stocking rate of 0.3 ha/calf. To complete the 123-d winter grazing season, all stockers were moved from the plots to a single wheat pasture. Stocking rate was 0.3 ha/calf and the grazing period was 86 ± 14.6 d. Data were analyzed by mixed model with grass cultivars as the main effect and year as random effect. Least squares means were used to test differences. Daily gains were less (P =0.03) for calves grazing PCGS plots than for calves grazing winter wheat plots (0.84 vs. 1.01 kg/d). Daily gain (0.84 ±0.05 kg/d) during the 86-d period when calves were grazing a common wheat pasture was similar (P =0.22) among stocker calves from PCGS and wheat plots. We concluded that a previous diet of PCSG would not affect BW gain on wheat pasture. However, the combination of less (P < 0.01) ADG and stocking rate of PCSG plots in comparison to wheat plots reduced (P< 0.01) the amount of BW gain/ha of land resource from 187 kg/ha for an all wheat pasture system to 124 kg/ha. When total ha of pasture are finite and a combination of PCSG and wheat is used, the distribution of land resources needed to provide enough forage for a 123-d grazing season was 62% PCSG and 38% wheat. Based on these data, we conclude that substituting wheat with PCSG will lessen the amount of BW gain produced per ha.