Intake of Cattle Offered Normal and Lodged Tall Fescue Swards

Abstract

Grazing behavior of livestock may be altered when grass swards are lodged by trampling or wind and rain. We used a balanced change-over design to investigate the effects of lodging on the ingestive behavior of Angus cows (Bos taurus L.)(mass (M): 344 kg) grazing swards of vegetative endophytefree ‘Kenhy’ tall fescue ( Festuca arundinacea Schreb.). Animals were offered normal swards (T1), lodged swards (T2), or swards with one half of their area lodged (T 3 ). To simulate lodging, swards were covered overnight with weighted plywood sheets that compressed sward surface height (SSH) from 34 to 14 cm and elevated sward dry matter (DM) density from 151 to 499 kg ha -1 cm -1 for herbage > 5 cm. Mean herbage DM intake per bite was 561 mg for T1, 713 mg for T2 and 792 mg for T 3 . Cattle grazed at 28 bites min -1 for T 1 , and 25 bites min 1 for both T 2 and T3. Herbage DM intake rates were 0.27, 0.31, and 0.33 kg 100 kg -1 (M) hour -1 for T 1 , T 2 , and T 3 , respectively. In another experiment, cattle were offered equal areas of normal swards (SSH: 27 cm) and lodged swards (SSH: 16 cm), normal and partially defoliated swards (SSH: 20 cm) swards, or lodged and partially defoliated swards. When offered normal and lodged swards, 64% of DM intake came from normal swards. When offered normal and partially defoliated swards about 60% of DM intake came from normal swards. Cattle grazed equally on lodged and partially defoliated sward segments when offered that choice.