Sheep and goats as tool to suppress juniper encroachment: Influence of stocking density and mixed grazing during summer

TitleSheep and goats as tool to suppress juniper encroachment: Influence of stocking density and mixed grazing during summer
Publication TypeConference Paper
Year of Publication2007
AuthorsUtsumi S.A., Cibils AF, Estell RE
Conference NameSociety for Range Management Annual Meeting
Date PublishedFebruary 9-16, 2
Conference LocationReno/Sparks, NV
ARIS Log Number210224
Keywordsgoats, grazing, one-seed juniper, sheep
AbstractGrazing trials were conducted to evaluate the use of prescribed grazing by sheep and goats to suppress one-seed juniper (Juniperus monosperma Englem. Sarg.) sapling reinvasion. A 2x2 factorial experiment was conducted with Goats (G) or Goats + Sheep (G+S) at high or low stocking densities (SD). Ten crossbreed Angora nannies (1.1 AU) or 5 nannies of the same breed mixed with 4 Ramboullet ewes (1.1 AU) grazed either 1 juniper invaded plot of 20 x 30 m for 6 days (LD) or 6 similar subplots of 10 x 10 m for 1 day (HD) in each of 2 blocks. Animals grazed from sunrise to sunset, were penned at night and received a protein supplement (45% CP) at a rate of 0.4% BW, daily. No effect of SD, herbivore (G, G+S), or their interaction was found on juniper utilization. Animals removed on average 38.3% of the length of marked juniper sapling branches. Understory grazing intensity differed between G or G+S (P=0.02) and SD (P=0.05) treatments. G+S removed 71.3 % of the available herbaceous biomass whereas G removed 64.7 %. Greater understory grazing intensity was observed under LD (70.4 %) compared to HD (65.0 %). Goats spent more time feeding on juniper compared to sheep (Goats: 24.5%, Sheep: 7.7%, P<0.01), whereas the opposite occurred with herbaceous vegetation (Goats: 76.0 %, Sheep: 92.3 %; P< 0.01). Stocking density did not influence time spent feeding juniper or herbaceous understory (P=0.08). Goats in HD and LD grazing treatments spent similar time feeding on juniper (P=0.09). Prescribed high density grazing with goats alone, rather than goats and sheep, could promote acceptable juniper sapling use along with lower damage on herbaceous vegetation. Juniper sapling responses to the treatments imposed in this study will be monitored through time.