Mechanical rejuvenation to dampen seasonal variation in chemical composition of browse

Abstract

Nutritional quality of range plants eaten by white-tailed deer (Odocoileus virginianus Raf.) in southern Texas is lowest during summer and fall. Nutritional quality of shrub regrowth is typically elevated for several months following top growth removal. We tested a strategy to temper the summer-fall decline in nutritional quality of guajillo (Acacia berlandieri Benth.) and blackbrush acacia (A. rigidula Benth.) by roller chopping separate, adjacent portions of the habitat each year during early July. Parallel strips of brush 40-m wide and about 1.6 km-long were roller chopped during 1986-87 in a pattern of alternating roller-chopped and nontreated strips. Leaves and twig tips of nontreated plants and of regrowth from roller-chopped plants were collected bimonthly and analyzed for crude protein (CP) and in vitro organic matter digestibility (IVOMD). Crude protein of guajillo leaves and stems was higher for regrowth than for nontreated plants for 6 and 8 months, respectively, after roller chopping in 1987, and IVOMD of leaves increased for 2 months. The CP of blackbrush leaves from regrowth was higher than CP of leaves from nontreated plants for 6 months after roller chopping in 1987 but IVOMD temporarily decreased. Roller chopping in early July may temporarily increase CP of guajillo browse during the late summer and early fall nutritional stress period, but it is not a promising method for rejuvenation of blackbrush browse.