Title: Influence of grazing deferments following summer fire on ewe performance and forage quality Authors
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 20, 2008
Publication Date: June 24, 2008
Citation: Waterman, R.C., Vermeire, L.T. 2008. Influence of grazing deferments following summer fire on ewe performance and forage quality. Journal of Animal Science 86(E-Suppl. 3):148. Abstract #61. Interpretive Summary: Abstract only
Technical Abstract: Complete rest or grazing deferment is a general recommendation following fire in the western U.S. to encourage vegetative recovery. However, effects of grazing deferments on animal performance have not been determined. Ewe performance and forage quality were evaluated for 70-d grazing trials with deferments until spring (May 17), early summer (June 21), or late summer (August 2) following summer fire in northern Great Plains. Within each deferment, three 1.5 ha plots were each grazed by 12 ewes (including two rumen-cannulated ewes). We weighed ewes on d 0, 35 and 70 to evaluate weight change to determine if length of time in a plot influenced performance. Meanwhile, forage quality was assessed by complete rumen evacuations, subsequent grazing and collection of rumen extrusa on days 15, 31, 51, and 68 of each grazing period. There was a significant interaction between deferment ' weigh d (P < 0.01) indicating ewe BW differed across deferments. However, BW gains for the initial 35 d in each 70-d grazing trial were similar. BW gains the last 35 d (P < 0.01 for deferment X period (1st and 2nd 35 d)) were similar to the initial 35 d for spring but remarkably lower for early summer and ewes actually lost BW the last 35 d in late summer deferment. Forage quality characteristics declined with later deferments and as time progressed within each grazing period. On an OM basis, forage CP concentrations were highest (P < 0.01) during spring grazing (9.7%) and decreased to similar concentrations of 6.7 and 6.3% for early and late summer grazing, respectively. No differences (P < 0.05) were observed for IVOMD or NDF disappearance for deferments. However, IVOMD was greater (P < 0.01) at d 15 and 31 into the grazing periods than at d 51 and 68 indicating a decline in forage quality as grazing period progressed. Results show that ewe BW decreases as post-fire grazing deferment extends thru summer and potential tradeoffs between livestock utilization and plant recovery should be evaluated.