Oral morphology and dietary choices of goats on rangeland

The morphometrics of mandible and teeth of mixed-breed goats on rangeland were analyzed to investigate the association between the oral apparatus and diet type. Canonical relationship between sets of mandible measurements (7) and main plants ingested (17) indicated that, overall, oral characteristics tended to modify ingestive behavior (canonical correlation = 0.81). In general, incisor length had a greater effect (absolute value of standardized coefficient: AVSC = 0.56) on ingestion of Nolina cespitifera than did other mandible variables. Incisor width influenced the ingestion of Parthenium incanum (AVSC = 0.47) and Flourensia cernua (AVSC = 0.43). Distance between the bases of the last most lateral incisors (I4 or corners) was associated with the ingestion of Atriplex canescens (AVSC = 0.54) and Florensia cernua (AVSC = 0.69). Incisor breath was important for the consumption of Larrea tridentata (AVSC = 0.68) and Cowania plicata (AVSC = 0.50). The ingestion of Agave lechuguilla (AVSC = 0.51) and Sphaeralcea angustifolia (AVSC = 0.43) were influenced principally by muzzle width. Distance between first molars was the variable most closely associated to the ingestion of Buchloe dactyloides (AVSC = 0.51) and Croton dioicus (AVSC = 0.62). Mandible length had a greater effect on the ingestion of F. cernua and Atriplex canescens than did other oral traits. Variation in the oral apparatus did not affect percentage of grasses, forbs and shrubs of goat diets. Fecal nitrogen, fecal phosphorous and number of species consumed were not related to oral traits. These results suggest that different dimensions in the oral apparatus of grazing goats lead to divergent selection of range plants, without altering the quality of their diet.