03332naa a2200313 a 450000100080000000500110000800800410001902400430006010000190010324501210012226000090024350006720025252018160092465000110274065300140275165300150276565300160278065300180279665300100281465300160282470000150284070000170285570000160287270000190288870000170290770000170292470000180294177300590295910500842020-02-04       2010    bl uuuu     u00u1 u    #d7 a10.1016/j.anireprosci.2010.02.0032DOI1 aCHANVALLON, A.  aSexual experience and temperament affect the response of Merino ewes to the ram effect during the anoestrous season.  c2010  aArticle history: Received 26 October 2009 // Received in revised form 11 January 2010 // Accepted 4 February 2010 // Available online 11 February 2010. Corresponding author at: : Audrey.Chanvallon@tours.inra.fr // Acknowledgments: This research was supported by the Australian Research Council (Project DP0558952) and by Meat & Livestock Australia (Project MS027 ?LambMax?). We thank Steve Gray for his assistance in the care and management of the  animals, and Margaret Blackberry for her assistance with the hormone assays. This work was a part of Audrey Chanvallon?s PhD project and was supported by CIFRE Convention and the ANRT. We thank also the Région Centre.  aAbstract: In seasonally anoestrous ewes of many breeds, the introduction of rams triggers an increase in gonadotrophin secretion that induces ovulation, a phenomenon known as the ram effect. The ram effect is a practical method for mating ewes outside the natural breeding season, and also can provide synchronised lambing, but the variability of the response, especially in young animals, reduces its potential for widespread application. The aim of our study was to assess two factors that are thought to contribute to the variability in young ewes: temperament and sexual experience. We used anovulatory ewes from a flock that had been genetically selected for calm or nervous temperament and compared the endocrine and ovarian responses to the ram effect in four groups (each n = 15): calm and parous (3-6 years old); calm and nulliparous (2 years old); nervous and parous; and nervous and nulliparous. Parous ewes, independently of their temperament, exhibited a faster endocrine response and a higher proportion of females cycling after ram introduction than nulliparous ewes. Nervous ewes exhibited a higher proportion of females cycling after ram introduction than calm ewes, but only in the nulliparous group. We conclude that temperament exerts little influence on the response to the ram effect in sexually experienced ewes, and that females of nervous temperament appear to respond better when sexually naive. Both sexual experience and temperament need to be taken into consideration when flock management involves the ram effect. Finally, some ewes were cyclic at ram introduction, yet exhibited an increase in LH secretion even in the presence of high concentrations of progesterone. The mechanism by which the inhibitory effect of progesterone on LH secretion was bypassed needs to be clarified.  aOVINOS  aCYCLICITY  aEXPERIENCE  aMALE EFFECT  aREPRODUCCIÓN  aSHEEP  aTEMPERAMENT1 aBLACHE, D.1 aCHADWICK, A.1 aESMAILI, T.1 aHAWKEN, P.A.R.1 aMARTIN, G.B.1 aVIÑOLES, C.1 aFABRE-NYS, C.  tAnimal Reproduction Science, 2010gv. 119, p. 205-211.