Reproduction in Domestic Animals

134 RJ Scaramuzzi and GB Martincondition. There is no obvious explanation for thedifferences in outcomes among these various studies.Nutritional studies are difficult because they requirestrict control of previous nutritional history. The mechanismbehind the reproductive response to nutritionalsupplementation is still problematic because we do nothave experimental models to explain the variability inthe response to a nutritional supplementation, the maleeffect and their interaction.Overall, it is clear that the efficacy of the ‘male effect’is influenced by nutritional and metabolic factors in thefemales. Thus, optimization of the efficacy of the ‘maleeffect’ for CGE management requires a very clearunderstanding of how nutrition influences the responsivenessof females to socio-sexual signals.ConclusionsThis brief review of nutritional interactions with seasonalrhythms and the ‘male effect’ draws attention tothe importance of nutrition as a major factor influencingreproductive outcomes and points to critical areas offuture research. There are some reports, often onlydescriptively documenting the nature of these interactionsbut there has been very little research exploring theunderlying processes. We need molecular genetic explanationsof the reproductive, metabolic, behavioural andphysiological processes that underpin, for example, theinfluence of nutritional inputs on the melatonin-drivenseasonal rhythms of ovarian cyclicity, and on femaleresponsiveness to the ‘male effect’ at both brain andovarian levels. By working towards a holistic perspectiveof the physiology, nutrition, genetics and behaviour ofour animals, we will be able to formulate ways tomanipulate their environment that will improve management,productivity and profitability and, simultaneously,promote a CGE industry.AcknowledgementsRJ Scaramuzzi is the recipient of a Marie Curie Chair of Excellencefrom the European Union (SUSTREPRO: FP6-2005-Mobility-10 ⁄ 42499) and their support is gratefully acknowledged. GB Martinwas funded by Meat and Livestock Australia (Project MS.027;‘LambMax’). Thanks are due to Dr B Malpaux and Dr D Guillaumefor their constructive comments on the manuscript.ReferencesBlache D, Adam CL, Martin GB, 2002: The mature malesheep: a model to study the effects of nutrition on thereproductive axis. Reprod Suppl 59, 219–233.Blache D, Chagas LM, Martin GB, 2007: Nutritional inputsinto the reproductive neuroendocrine control system – amultidimensional perspective. 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