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PRODUCTION PAPERS

Evaluation of Corn Hybrids at Two Stages of Development for Grazing Heifers

^a Dep. of Crop and Soil Sci., Pennsylvania State Univ., University Park, PA 16802
^b Dep. of Dairy and Anim. Sci., Pennsylvania State Univ., University Park, PA 16802

^* Corresponding author (hdk3{at}psu.edu)

Received for publication March 15, 2002. Grazing-based livestock producers in the northeastern USA most commonly grow corn (Zea mays L.) for silage. Corn could be grazed during dry periods when cool-season pasture is limited. To assess the value of grazing corn, we compared four hybrids [‘Baldridge grazing maize’; ‘Cargill F657’, a bm3 brown midrib hybrid (Bmr); ‘Pioneer brand 3335’; and a commercial silage blend] at silking and milk–dough stages of development under grazing with eight Holstein heifers (Bos taurus) for 3 yr in Pennsylvania. Yield, forage disappearance (pre- minus postgrazing dry matter), and forage quality were measured. Economic feed and economic yield values for all hybrids and stages of development were calculated. Differences among hybrids in yield, forage disappearance, and quality were minor, resulting in small differences in economic value except for Bmr, which had high seed cost. Delaying grazing from silking to milk–dough stage increased yield from 2.4 to 6 Mg ha^-1 and forage disappearance from 2.2 Mg ha^{- 1} at silking to 4.9 Mg ha^-1 at milk–dough (average of 3 yr). Crude protein and fiber content decreased from silking to milk–dough stage. Because of the higher yield at the milk–dough, economic yield values were $104 ha^-1 or $310 ha^-1 higher in 2 of 3 yr. Economic yield value of grazing corn at the milk–dough stage averaged $133 ha^-1 higher than the estimated economic yield of high quality corn silage, primarily due to harvesting and silo-filling costs. When grazing management promoted high utilization, grazing corn at the milk–dough stage offered a substitute to purchasing stored feed, particularly when inexpensive, high quality hybrids were grazed.

Abbreviations: ADF, acid detergent fiber • Bmr, ‘Cargill F657’ (a bm3 brown midrib hybrid) • Conventional, ‘Pioneer brand 3335’ • CP, crude protein • Grazing Maize, ‘Baldridge grazing maize’ • NDF, neutral detergent fiber • TDN, total digestible nutrients