BROWSING ABILITY AND UTILIZATION BY SHEEP AND GOATS OF ATRIPLEX-HALIMUS L SHRUBS

A study was conducted in the Ebro valley in Spain to evaluate the util ization and intake of Atriplex halimus grazed by ewes and goats, as we ll as bush regrowth after 12 months of grazing. Ten Rasa Aragonesa ewe s and ten Blanca Celtiberica goats were allowed to browse an identical number (587) of A. halimus bushes for 5 weeks at a stocking density o f 20 heads ha(-1). Measurements were made of height (h) and width (d) of every bush before and after grazing and 12 months later to evaluate regrowth next season. Forage DM of bushes (y) was related to its volu me (x = pi[1/2d/(2)h) by the equation y(g) = 337.5 X (m(3)) + 162.37 ( r = 0.92**) that was used to estimate forage availability. Patterns o f forage utilization were similar for goats and ewes, being 61% and 59 % the level of utilization, respectively, after 4 weeks grazing. Diffe rences in level of DM intake of goats ( 1430 g day(-1)) and ewes (1310 g day(-1)) were not significant. Reduction in volume of hushes consum ed by goats (0.563 m(3)) was higher (P < 0.001) than by ewes (0.271 m( 3)). The values appear to be associated with mean size of twigs eaten (4.58 vs 2.72 mm), used as a parameter to estimate differences in brow sing ability between goats acid sheep. Pregrazing plant dimensions wer e recovered 12 months after grazing, suggesting that A. halimus is tol erant to high grazing pressures in autumn. Browsing appeared to be mai nly of annual regrowth, allowing the animals access again to the forag e produced in the following season. Lack of effect on BW gain suggests that a sole diet of A. halimus may be used to maintain sheep and goat s without an energy supplement until animal requirements are higher du e to pregnancy and milk production.