Head and tail morphology of pelibuey, katahdin and blackbelly rams in Colima, México

Abstract

A study was conducted with the objective of characterizing, comparing and analyzing the cephalic and caudal morphologies of Pelibuey, Katahdin and Blackbelly rams in the state of Colima, Mexico. A total of 53 rams, up to 2 years of age were scored for the following12 cephalic and caudal measurements: cranial width, cranial length, head width, head length, head depth, face width, face length, ear width, ear length, tail length, tail width at the joint and tail width at the tip. Katahdin rams had a significantly greater cranial width, head width and tail at the tip width than Pelibuey and Blackbelly rams (P ≤ 0.02). The tail width at the joint was greater in Katahdin rams than in Pelibuey rams (P = 0.01), and Blackbelly rams have intermediate values. Canonical analysis identified two significant canonical variables, CAN1 and CAN2, which accounted for 92% and 8% of the total variation, respectively. Katahdin rams were separated from Pelibuey and Blackbelly rams by the tail width the tip, while the head length and tail width at the joint differentiated the Pelibuey and Blackbelly rams. All Katahdin rams were correctly assigned within their breed group, while most Pelibuey rams (58.60%) were erroneously grouped as Blackbelly. Likewise, a significant proportion of the Blackbelly rams (40%) were misclassified as Pelibuey. Although Pelibuey, Blackbelly and Katahdin rams meet the standards of their respective breeds, phenotypic characterization using canonical discriminant analysis demonstrated the existence of a high degree of crossbreeding among these breeds and showed that the head length, tail width at the tip and tail width at the joint were the most discriminating variables for identifying and separating the three sheep breeds.