The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Tuesday, January 29, 2008
5
Effect of Four Cool-Season Grass Species on Bite Mass by Cattle Foraging An Artificial Sward
P. Gregorini, Pasture Systems & Watershed Management Research Unit, USDA-ARS, Building 3702 Curtin Road, University Park, PA 16802
Herbage intake rate is primarily driven by bite mass. A considerable body of literature exists in Europe and Australia on sward factors affecting cattle bite mass. However, information is still lacking in related to specific grass species of northeastern United States pastures. Four grass species commonly found in the northeastern United States (meadow fescue [MF], Festuca pratensis Hud.; orchardgrass [OG], Dactylis glomerata, L.; quack grass [QG], Elytrigia repens; and red canarygrass [RG], Phalaris arundinacea) were equally established in micro-sward boxes (78 cm x 48 cm x 13 cm) and foraged in a replicated 4 x 4 Latin square design, by non-pregnant, non-lactating Holstein cows in short-term foraging sessions. Cows were allowed to take at maximum 50 bites. Boxes were weighed (± 0.1 g) before and after each foraging session. An ungrazed control box of the same species as that being tested was weighed before and after each test in order to correct for evapo-transpiration losses during the test period. Herbage mass, sward surface height, bite mass and grazing depth data were collected. Dependent variables were analyzed by ANOVA utilizing PROC GLM of SAS. Herbage mass and sward surface height were greatest (P < 0.05) for RC (200 g/m2, 20.6 cm) and OG (150 g/m2, 21 cm), followed by MF (112 g/m2, 15.2 cm) and least for QK (70 g/m2, 11.2 cm). These differences did not affect (P > 0.05) bite mass, which averaged 0.53 g DM/bite across all treatments. Despite this lack of effect, grazing depth differed (P < 0.05), averaging 37, 27, 25 and 18% of sward surface height for OG, RC, MF and QG respectively. These results imply that under the conditions of this experiment the grass species affected other short-term foraging tactics than bite mass. Implications on longer-term and natural conditions warrant further research.