Reproduction in Domestic Animals

12 D Blache, GB Martin and SK MaloneyVoluntary feedintakeMetabolic fuelEnergy reserveEmotional reactivityHPA axisMetabolicHormones:leptin, orexinsinsulin,IGF-1, GH,T3, T4ThermogenesisImmune functionCellular maintenanceGrowth, locomotionReproductionFig. 3. Central role of metabolic hormones in the interactions amongemotion, reproductive function, immune function, metabolic status,thermogenesis and other bodily functions. The sympathetic pathwayshave been omitted for clarityand limit the risk of conflicting results since, bydefinition, a group of animals showing a homogenousresponse to any stimulus will have less variability in anyparameter associated with that response.As described previously, the amount of availablemetabolic fuel needs to be ‘assessed’ by a control systemand then expenditure ‘directed’ towards reproductivefunction if and when required. For all systems, theassessment of energy levels and their partitioning isunder the control of metabolic hormones (Fig. 3).Thyroid concentrations were higher in a sub-populationof ‘calm’ than in a sub-population of ‘nervous’ animalsin our selection lines (Blache et al. 2002). We have alsoshown that the cortisol response to a novel object ishigher in nervous ewes than in calm ewes (Bickell et al.2008). These considerations apply equally to stressassociated with experimental protocols (Martin et al.1981; Adams et al. 1993). The effects of stress andcortisol on the reproductive axis are numerous anddiverse – in the female, they can either inhibit orstimulate ovulation (Dobson and Smith 2000). Theeffect of temperament genetics on reproductive processeslikely involves hormonal pathways. These linksare still to be demonstrated experimentally, but temperamentaffects the hormonal systems involved in thecontrol of energy partitioning and this may be how itinfluences the outcomes of experimentation targeting therelationship between nutrition and reproduction.Aside from improving the experimental design andoutcomes, the welfare of experimental animals could beimproved by selection for temperament. Less reactiveanimals will have an improved freedom from fear anddistress since animals that are less reactive to novelty willpresent reduced physiological and behavioural reactionsto novel experiences (Korte 2001), including exposure toa research environment.ConclusionIn inference science, hypothesis testing involves manipulatingone or a few parameters, while other factors thatcould influence the dependent parameters are controlled.In this paper, we have shown that multiplefactors that affect and control reproduction could affectthe outcomes of animal experimentation because theyaffect reproductive physiology, over both short and longtime scales, and even across generations. These factorsneed to be controlled. In addition, emotional reactivityhas the potential to alter experimental outcomes, just asgenotype can affect the outcomes of experimentation inwhich photoperiod or nutrition is manipulated. Byconsidering the nutritional history and emotional characteristicsof the individual subjects, the variabilitywithin experimental groups can be reduced and two ofthe 3Rs (reduction, refinement) would be applied,leading to more ethical experimentation. This creates awin–win situation for researchers and experimentalanimals because more ethical science results in betterscience.AcknowledgementsWe would like to thank the generous assistance of the students andstaff of Animal Science (University of WA). Funding was supplied bythe National Health and Medical Research Council, the AustralianResearch Council, the Ada Bartholomew Medical Research Trust, andthe University of Western Australia.ReferencesAdams NR, Atkinson S, Martin GB, Briegel JR, Boukhliq R,Sanders MR, 1993: Frequent blood sampling changes theplasma concentration of LH and FSH and the ovulationrate in Merino ewes. 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