The 2008 Joint Meeting of the Society for Range Management and the America Forage and Grassland Council. |
Monday, January 28, 2008
32
Herbage Production and Animal Performance Response to Grazing System in the Nebraska Sandhills
Walter H. Schacht1, Jerry D. Volesky2, and Paul R. Schroeder1. (1) Agronomy and Horticulture, University of Nebraska-Lincoln, P.O. Box 830915, Lincoln, NE 68583-0915, (2) West Central Research and Extension Center, University of Nebraska-Lincoln, North Platte, NE 69101
Grazing systems likely affect diet quality of cattle grazing rangeland vegetation. We tested the hypothesis that diet quality of cattle grazing a short duration grazing (SDG) system is generally higher through the growing season than diet quality of cattle grazing a deferred rotation (DR) system in the eastern Nebraska Sandhills, resulting in greater animal performance. The study was conducted at the University of Nebraska-Lincoln Barta Brothers Ranch in the northeastern Sandhills near Ainsworth. The systems study was initiated in 1999 when the upland range was divided into 24 pastures that averaged 53 ha each. The 24 pastures were divided into 2 blocks of 12 pastures each based on topography. Eight pastures in each block were allocated to a SDG system and 4 pastures were assigned to a DR system. Each system was grazed annually by cow-calf pairs and spayed heifers at 0.28 AUM/ha from15 May to 15 October. To test our hypothesis, we periodically collected diets of esophageally-fistulated cows grazing pastures in each system through the grazing seasons of 2005 and 2006. We also recorded weight gains of the 20 spayed heifers in each system. Over the 9 years of the study, herbage production ranged from 900 kg/ha in 2002 to about 2000 kg/ha in several years. Mean in vitro organic matter digestibility, neutral detergent fiber, and crude protein content of cattle diets did not differ between the 2 systems. In addition, the decline in diet quality through the grazing season generally followed a similar pattern for the 2 systems. Weight gains of the spayed heifers also did not differ between the 2 systems, and averaged about 0.78 kg/head/day in 2006. The lack of herbage production and animal performance responses to SDG indicate that the high input costs associated with SDG are not justified in the Nebraska Sandhills.