Characterization of the productive performance of Highlander sheep in Southern Chile. II. Male reproductive traits

Abstract

Basic information on the reproductive potential of animals is required to establish sound reproductive procedures including the application of assisted reproductive technology. The study aimed to characterize the reproductive performance of rams of the Highlander breed during the breeding season. With this purpose 53 rams were allocated to two experiments: in the first one, 8 Highlander rams were compared against 8 Suffolk rams used as reference in terms of scrotal circumference, ejaculate traits and service capacity test; and in the second experiment, 37 rams and 506 ewes in a male to female ratio ranging between 1:8–24, were used to assess male fertility in terms of conception and prolificacy rates of ewes exposed. Compared to Suffolk rams, results showed that Highlander rams exhibited larger scrotal circumference (P=0.003), tended to have both larger sperm concentration (P=0.08) and lower volume (P=0.098), and have similar sperm normal morphology (P=0.63) in their ejaculates; their spermatozoa moved at lower speed (VCL, P<0.001; VAP, P=0.02) but more linearly (LIN, P=0.006; ALH, P<0.001), and rams displayed less sexual activity (effective mounts, P=0.028; false mounts, P<0.001). When rams were exposed for natural breeding, their average reproductive performance was consistent with the conventional targets demanded for high productivity. Although significant differences in performances were found between rams, no correlation was found between conception rate neither with male to female ratio (P=0.82) nor with prolificacy (P=0.95) or between male to female ratio and prolificacy (P=0.58). Cumulative results suggest that Highlander rams exhibit an adequate potential for reproduction. However, for meeting high standards of productivity, Highlander rams need to be selected by potential fertility of their ejaculates and service capacity in addition to the conventional breeding soundness evaluation.