BOTANICAL COMPOSITION AND SEASONAL TRENDS OF CATTLE DIETS IN CENTRAL ARGENTINA

About 40,000 km(2) of the Caldenal in central semiarid Argentina are r angelands where the most important economic activity is cow-calf opera tions. Some information on forage species, mainly regarding taxonomy, ecophysiology, and nutritive value, is available, but detailed studies on composition of free-ranging cattle diets are lacking. The objectiv e of this work was to study the botanical composition and seasonal tre nds of cattle diets in the southern Caldenal. Diets were studied throu gh microscopic analysis of cattle feces collected monthly in a typical plant community during a 12-month period. Grasses were the bulk of th e diets, except in November when more than 50% of the diet was Medicag o minima (L.) Grufberp. Highest consumption among the grasses was of P iptochaetium napostaense (Speg.) Hack., one of the dominants in the gr ass layer. High consumption of Pappophorum mucronulatum Nees, one of t he few warm-season grasses in the region, was found during the summer. Calden (Prosopis caldenia Burk.) pods, consumed in late summer and fa n, were the only woody fragments found in appreciable amounts. Classif ication and ordination techniques were used to analyze seasonal trends . In spite of a relatively high homogeneity in the diets, 2 well-defin ed seasonal trends were detected, one in the fall-winter period and an other in the spring. Cattle diet diversity was minimum during the cold est months of the year.