The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Wednesday, January 30, 2008
17
Effect of Corn or High-Quality Hay Supplementation on Performance of Beef Heifers Grazing Annual Ryegrass Pastures from the Argentinean Flooding Pampa Range
P. Gregorini, Pasture Systems & Watershed Management Research Unit, USDA-ARS, Building 3702 Curtin Road, University Park, PA 16802 and Mariano Eirin, Producccion Animal II, Universidad Nacional de La Plata, Avenida 60 y 119, La Plata, Argentina.
Annual ryegrass (Lolium multiflorum Lam.) is widespread in the Flooding Pampa range, where the control of warm-season grasses growth in late summer ‘promotes’ annual ryegrass-dominated swards (>75% DM basis) in fall winter, and spring. As in every winter-annual grazing environment, lush conditions of herbage restrict animal performance, leading to energy supplementation regimens. While corn supplementation is an effective and common practice, its price keeps increasing. Consequently, high-quality hay is being reconsidered to substitute corn. This fact stimulated a direct comparison between these supplements. This experiment aimed to assess the effect of corn or high-quality hay supplementation on average daily gain (ADG) of beef heifers grazing annual ryegrass-promoted pastures. This experiment was conducted during fall and winter at La Plata National University , Argentina . Thirty two Angus heifers (360.30 ± 47.27 lb.) were randomly allocated to the two treatments, corn (CS) or high-quality hay (HS, 89% DM, 60% IVDMD, 12% CP) supplementation. The supplementation level of both treatments was 0.5% (DM basis) of BW/d. Supplement intake was estimated daily by difference between offer and refusal. Both groups of animals were rotationally grazed. Herbage allowance was 6% (DM basis) of BW/d. Heifers were weighed every 21 days. The ADG was analyzed using a statistical model that included the effect of time as a repeated measurement using PROC MIXED of SAS. Supplement intake was evaluated using the t-test, which did not differ (P > 0.05) and averaged 1.9 ± 0.15 lb. across both treatments. The HS tended to increase (P = 0.055) ADG (1.88 ± 0.25 and 2.06 ± 0.24 lb. for CS and HS, respectively), which is speculatively explained by a better ruminal function generated by a more even nutrient release from the supplement.