Effect of early and late exposure to estrual ewes on ram sexual performance classifications

Abstract

This study was conducted to determine whether exposure of ram lambs to estrual ewes during their first autumn and again as adults just before serving capacity tests (SCT) affected the outcome of the sexual performance tests. Treatments were either early exposure of Polypay ram lambs (i.e., 7–8-mo-old rams with ewes for 17 d [ n = 30] or no early exposure [ n = 30]), and late exposure (i.e., 16–19-mo-old rams with estrual ewes for 3 d) or no exposure to estrual ewes in a 2 × 2 factorial arrangement. Three serving capacity tests were conducted immediately after the early exposure period for individual ram lambs that were exposed to ewes early. Three sham sexual performance tests (i.e., four ram lambs placed in test pens for 30-min without ewes) were conducted with ram lambs that were not exposed to ewes early. All rams were evaluated during nine 30-min serving capacity tests over a 2-mo period at 16–19 mo of age to determine sexual performance. Prior to serving capacity tests, one half of the rams from each early exposure treatment were exposed to estrual-induced ewes for 3 d. Specific sexual behaviors (e.g., sniffs, flehmens, foreleg kicks, vocalizations, mount attempts, mounts, and ejaculations) were recorded during serving capacity tests. Number of sniffs, flehmens, foreleg kicks, vocalizations, and mount attempts were summed without estimating the value of importance and analyzed as courtship behaviors. Sexual performance data were analyzed with Mixed model procedures for repeated measures. During serving capacity tests, the early exposed rams exhibited more courtships (40.3 ± 8.0 versus 23.4 ± 4.6; P < 0.05; LSM ± estimated SE), mounts (11.3 ± 1.0 versus 7.7 ± 0.9; P < 0.01), and ejaculations (3.3 ± 0.2 or 2.4 ± 0.2; P < 0.01) than rams not exposed to ewes as ram lambs, respectively. We conclude that early exposure of 7–8-mo-old ram lambs to estrual ewes improves sexual performance in serving capacity tests at 16–19 mo of age in most rams whereas, late exposure to estrual ewes for 3 d prior to serving capacity tests did not improve sexual performance scores.