Effect of Season and Regrazing on Diet Quality of Burned Florida Range

Abstract

Diet crude protein and in vitro organic matter digestibility (IVOMD) of diets of esophageally fistulated steers were compared for a pasture grazed June to September ("summer" pasture) and again in January to March ("winter-regraze") with a pasture grazed in "winter-only". The longevity of improvement in diet quality due to burning also was measured. Grass and forb yields were determined before and after grazing. Dietary crude protein and IVOMD were greater (P<0.05) on the summer (8.4% and 47%) as compared to the winter-only pasture (6.7% and 32%) in both years. Diet protein concentration of the winter-regraze pasture (7.6%) was not different (P>0.05) from summer or winter-only diets in both years. IVOMD in diets from the winter-regraze (36%) was intermediate and significantly different from the summer and winter-only pasture in the first year. Diet IVOMD in the second year was not different (P>0.05) on the winter-regraze (34%) and winter-only (32%) pastures. Diet quality was not different (P>0.05) in summer (8.2% protein, 46% IVOMD) beginning 4 months after a burn as compared to forage quality in summer 16 months after the burn (8.5%, 47%, respectively). Compared to grazing in winter only, grazing in summer may improve digestibility of forage from range when that range is regrazed the following winter, but protein and energy of the summer range will be deficient for lactating cows.