Structure of Tall Fescue Swards and Intake of Grazing Cattle
1990
Arias, J. E. | Dougherty, C. T. | Bradley, N. W. | Cornelius, P. L. | Lauriault, Leonard M.
Models of grazing systems need logic that estimate herbage intake of livestock from physical and chemical properties of the sward. Changeover designs were used to study the effects of sward structure of tall fescue (Festuca arundinacea Schreb. cv. Kenhy) on ingestive behavior of grazing cattle. Fourteen (Tl), 21 (T2), and 28 (T3) days of growth established sward surface heights of 16, 20, and 22 cm, with herbage dry matter (DM) masses (>5 cm) of 0.84, 1.43, and 2.16 Mg ha−¹. When each of 12 2-yr-old Angus heifers (Bos taurus L.) (liveweight, 381 kg) were allocated the same grazing area (26 m²), with DM allowances (>5 cm) of 2.2,3.7, and 5.6 kg for 90 min of grazing, heifers ingested DM at 1.07, 1.65, and 2.03 kg h−¹, with herbage DM intakes per bite of 0.45, 0.65, and 0.82 g and consumption of 75, 69, and 57% of allowance for T1, T2, and T3, respectively. Rates of biting were not flected by sward treatments and averaged 42 bites min−¹. The grazing horizon of the vegetative tall fescue tillers was limited to a plane above the tops of pseudostems and ingestive behavior reflected the properties of herbage in that horizon. Permanent address of J.E. Arias is C.C. 31, INTA. 2700, Pergamino, Buenos Aires, Argentina. Kentucky Agric. Exp. Stn. Journal Paper 88-3-5-233.
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