The Effect of Growing Season on the Nutrient Composition and in Vitro True Digestibility of Browse and Forb Species Commonly Consumed by Goats in the Southeastern United States

The goal of the study was to determine the nutritive values and in vitro true digestibility (IVTD) of browse and forb species consumed by goats at the Tuskegee University Atkins site. The site can be described as unmanaged long leaf pine plantation site approximately 10 years of age in the east, gulf coast region of Macon County, Alabama. The latitude of the Tuskegee site is 32.4230N and longitude is 85.6910W. The landscape is characterized by gently sloping topography (5–10 percent) and consist of many encroaching browse/forb species. The predominant grass cover is primarily of Andropogon virginicus (broom sedge) and other bunch grasses. These browse/forb species encompass much of the woodland vegetation in the Southeastern United States. Thirty different species were selected for analysis based on previous observations of goat preferences. Samples consisted of the leaves and tender tips collected three different times throughout the duration of the growing season (i.e. April (Spring), July (Summer), and November (Fall)). Samples were analyzed for crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), crude fat, and in vitro true digestibility (IVTD). The total digestible nutrients (TDN) values were estimated from ADF values. The average CP values were 19.0, 16.9, and 11.5% for spring, summer and fall collections, respectively. There were significant differences (P<0.001) between the spring values compared with summer and fall values, however, there were no differences (P>0.05) between the summer and the fall values. Similar trends were observed for ADF, NDF, TDN, and IVTD values, except the fat values were similar between the spring and the fall collections while being significantly different from the summer values (P<0.01). The results provided valuable information about the nutritive values and IVTD value of browse and forb species commonly consumed by meat goats in the woodland areas of Alabama. The experiment will be continued for two additional years to overcome the seasonal differences so meaningful results can be obtained.

Keywords:Browse; Forbs; Nutritive values; In vitro true digestibility

Abbreviations:CP= Crude Protein; ADF= Acid Detergent Fiber; NDF= Neutral Detergent Fiber; TDN= Total Digestible Nutrients; IVTD= In Vitro True Digestibility; CT= Condensed Tannins