Prior exposure of maiden ewes to rams enhances their behavioural interactions with rams but is not a pre-requisite to their endocrine response to the ram effect

摘要

In this study, we tested whether prior experience with rams would modify the behavioural and endocrine responses of maiden ewes to rams. During mid-anoestrus, sexually nacve, maiden ewes were exposed to rams for 7 days (ram experienced, RE; n =61) or isolated from rams (ram nacve, RN; n =63). All ewes were subsequently isolated from rams. In Experiment 1, RE (n =55) and RN (n =57) ewes were introduced to rams during late anoestrus. RE ewes had more total and positive interactions with rams than RN ewes (P <0.001). RE ewes showed more ram seeking behaviour and spent more time in proximity of rams than RN ewes (at least; P <0.05). In Experiment 2, RE (n =6) and RN (n =6) ewes were introduced to rams midway through a frequent blood sampling regime in late anoestrus. Ram introduction stimulated an increase in LH pulse frequency and basal LH in both RE and RN ewes (at least P <0.05). RE ewes had an increase in mean LH concentrations (P <0.01) that failed to reach significance in RN ewes (P <0.1). There was no significant effect of prior experience with rams on LH pulse frequency, amplitude or whether ewes had an LH surge. In conclusion, prior experience with rams is important in developing appropriate ewe-ram interactions but is not a pre-requisite to the endocrine response to the ram effect.