Reproduction in Domestic Animals

44 P Chemineau, D Guillaume, M Migaud, JC Thie´ry, MT Pellicer-Rubio and B Malpauxproduction of semen doses, rams raised in open barnsare subjected to 2–3 months extra ‘LD’ (from Decemberto February) followed either by return to naturalphotoperiod, or by subcutaneous treatment with melatoninimplants which mimics SD (‘SD’) (Fig. 5). Thissuccession ‘LD’–‘SD’ stimulates semen output in quantityand quality in spring, thus mimicking the normalsexual season which itself normally lasts 2–3 months(Malpaux et al. 1995).In goat farms, (always in open barns), males andfemales are subjected to the second type of treatmentperformed in AI centres (succession ‘LD’–‘SD’). Thistreatment should be associated with a ‘buck effect’(introduction of treated bucks for 45 days, after 35–75‘SD’) in order to induce ovulations and oestrousbehaviour and to get high fertility rate. Under suchconditions, out-of-season fertility and prolificacy can bekept at high levels (>75% kidding rate with approximatelytwo kids per kidding) (Chemineau et al. 1996).This type of treatment could be satisfactorily associatedwith AI on fixed-time basis with fertility results equivalentto ‘classical’ hormonal treatment with FGAsponge and eCG (Pellicer-Rubio et al. 2007, 2008).For local breeds in subtropical conditions where seasonalityis less marked than those raised under temperatelatitudes, the treatment of females is not necessary.When the LD treatment is applied only in bucks usedfor the ‘buck-effect’, the percentages of ovulatingfemales and their fertility after natural mating are high(Delgadillo et al. 2002, 2004).In ewes, a majority of out-of-season lambings are stillobtained using ‘classical’ hormonal treatments (FGAsponges + eCG), but the frequency of utilization ofmelatonin implants to get out-of-season breeding isincreasing, especially in Mediterranean countries. Theuse of implants also increases fecundity: + 0.20lamb ⁄ ewe treated ⁄ year has been almost always observed,mainly due to increased proportions of twinsrather than triplets (Chemineau et al. 1996).Photoperiodic treatments are also applied in mares toadvance the annual breeding season and to provide foalswith a decisive age-related advance when competingwith their contemporaries born the same year (seeabove). This is generally performed by exposing maresto LD or pseudo LD during autumn and winter. Suchtreatments allow mares to be fertilized approximately2–3 months earlier than females kept under a naturalphotoperiod (Guillaume 1996).Thus, photoperiodic treatments are now used in bothsexes of nearly all farm species to control seasonalreproduction. Whatever the species, they use commonproperties of alternations between inhibitory and stimulatoryphotoperiods, where durations are adapted tothe species and sex. When using pure light treatments(without melatonin), especially when applied in openbarns, they could be considered as non-invasive whichfully respects animal welfare considerations. It is veryprobable that these photoperiodic treatments will beused more extensively in the future as livestock productionsystems strive to be more sustainable.(a)Light-proof buildings:17h 16DuskDawn16LProgressivedecrease8L0 60JanuaryMarch150 daysJune(b)17h 16(c)(d)DuskDawn0 60JanuaryMarch17h 16DuskDawn0 60JanuaryMarchOpen barns:2420"Long days"2nd period of suppl. lightShort daysMelatonin"Short days"Natural dusk150 daysJune150 daysJunehours16128401st period of suppl. lightJanuary February March April May June"Long days"Natural lightorMelatonin"Short days"Natural dawnFig. 5. Photoperiodic treatmentsto control sexual activity in smallruminants raised in closed (a–c) oropen (d) barns (adapted fromChemineau et al. 1996)Ó 2008 The Authors. Journal compilation Ó 2008 Blackwell Verlag