Effects of annual rainfall and farm on lamb production after treatment with melatonin implants in Merino sheep: A 4-year study

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1 New Zeln Veterinry Journl 57(3), 4-45, 29 4 Sientifi Artile Effets of nnul rinfll n frm on lm proution fter tretment with meltonin implnts in Merino sheep: A 4-yer stuy FA Arreol, JA Aei, F For, A Gri, RA Mrtín n O Mes Astrt AIM: To etermine the effets of nnul rinfll n frm on the effiy of meltonin implnts in improving lm proution in Merino sheep in Spin. METHODS: A stuy ws onute on 3,87 Merino sheep on six frms over 4-yer perio (24 27). Meltonin implnts were inserte uring the seon hlf of Ferury or erly Mrh (winter) (Meltonin group) or not (Control group). Multinomil logisti regression ws use to etermine the effets of meltonin, frm n yer, n their intertions, on reproutive outomes. Regression nlysis ws use to exmine the reltionship etween nnul rinfll n the perentge of ewes lming, perentge of lms orn to ewes lming, n overll lming perentge, for eh yer n tretment group within frm. RESULTS: Annul rinfll, frm n tretment with meltonin, n their intertions, h signifint effet on the reproutive performne of ewes (p<.). Tretment with meltonin inrese the perentge of ewes lming (Meltonin group = 77 (SEM 4)%, Control group = 44 (SEM 7)%; p<.), n overll lming perentge (Meltonin group = 9 (SEM )%, Control group = 59 (SEM 2)%; p<.). Tretment ifferenes were espeilly pronoune in 25 n 26, when nnul rinfll ws exeptionlly low; ewes in the Control group h the lowest lming rtes those yers. Lming rtes n overll lming perentge were positively orrelte (p<.5) with the mount of nnul rinfll ut the orreltion oeffiients were higher in the Control thn Meltonin group. CONCLUSIONS: Meltonin implnts re n effetive mens of improving lm proution of Merino ewes, espeilly in hrsh environments where low nnul rinfll limits the vilility of foo. When meltonin tretment ws use, however, the responses of floks on iniviul frms were iffiult to preit euse within yer, responses i not our on ll frms. KEY WORDS: Sheep, meltonin, rinfll, etween-yer vrition, inter-frm vrition Introution Suutneous meltonin implnts hve een esigne to provie rtifiil ontrol of oestrus in sheep, n re use wiely to vne the reeing seson n to improve reproutive performne uring noestrus in highly sesonl (Hresign et l. 99) IFAPA Hinojos el Duque, Crreter el Viso, km 2, 427 Córo, Spin. Deprtment of Animl Proution n Foo Siene, Fulty of Veterinry Meiine, Miguel Servet 77, 53 Zrgoz, Spin. Author for orresponene. Emil: lf@unizr.es n Meiterrnen (Chemineu et l. 996) rees of sheep. The inrese in the finl numer of lms proue per ewe is ue to inrementl inreses in fertility n prolifiy (For et l. 995; Chemineu et l. 996; Aei et l. 27), whih re erive, in prt, from inrese survivl of emryos use y exogenous meltonin (Vázquez et l. 29). To vrying egrees the effets of exogenous meltonin on reproutive performne n e hieve on ommeril frms if n pproprite ssessment of the speifi onitions on eh frm is use when seleting suitle tretment time (Kouimtzis et l. 994). In n experiment esigne to evlute the effets of frm on the effiy of meltonin tretments in three rees of sheep (Aei et l. 27), the hormone inrese the overll numer of lms proue, lthough effiies ppere to iffer epening on the ree n time of tretment. In Merino ewes, reproutive performne inrese fter tretment in Ferury (winter) only. This suggests tht meltonin might e useful tool to improve lm proution ut within eh ree, effiy seeme to vry etween frms n sesons. Typilly, meltonin implnts re inserte roun the time of the summer solstie, to vne the reeing seson (Hresign et l. 99). Unlike the rees of sheep from northern Europe, those from the Meiterrnen hve short sesonl noestrus, espeilly when soil (rm effet) or nutritionl ftors re mnge ppropritely (Linsy 996). Compre with genotypes frther north, sheep rees from the Meiterrnen hve n erlier onset of reeing, even when oth re sujete to the sme photoperioi tretment (Mrtin et l. 999). Thus, t the ommeril level, sheep in Meiterrnen floks re ministere meltonin implnts t out the time of the spring equinox (Chemineu et l. 996). Merino n Merino-rossrees respone to meltonin tretments over muh of spring n erly summer t ltitue 38 S in Austrli n in New Zeln ut rees from the Unite Kingom (UK) only respone uring reltively short prt of the seson roun the time of the summer solstie (Willims et l. 992). Photoperio is not the only ftor responsile for sesonl reeing in ewes, espeilly in Meiterrnen rees. Other ftors suh s nutrition n possily reltive humiity, preipittion n temperture might hve n effet on perios of reue oestrous tivity (Glin et l. 996). Losses in liveweight n oy onition use y poor-qulity fee n inequte feeing uring the pre-mting n mting perios re etrimentl to the reproutive rte (For et l. 992; Aei et l. 26). Hypothetilly, unernutrition use y irregulr n insuffiient rinfll might ply n importnt role in the reproutive filure of sheep y prouing normlities of the ovum or the emryo, lutel inequy, n filure of the supply of progesterone to the uterus, or the mehnisms involve in the mternl reognition of pregnny (for review, see Aei et l. 26). The im of this stuy ws to etermine the effets of nnul rinfll n frm on the effiy of meltonin implnts to improve the reproutive performne of Merino floks in Spin.

2 42 New Zeln Veterinry Journl 57(3), 29 Arreol et l. Mterils n methos All proeures use in this stuy were pprove y the Ethis Committee for Animl Experimenttion of the University of Zrgoz, Zrgoz, Spin. Animls The stuy ws onute on six sheep frms within 5-km rius of the oopertive Dehess Coroess in Córo, Spin, over 4 yers (24 27). Memers of the oopertive in the Los Perohes region of southern Spin (~38 N) own >5, Merino sheep. Over the 4-yer perio of the stuy, 3,87 ewes from the six frms were selete for the stuy if they h t lest one lming the previous yer. The stuy ewes on eh frm were mintine uner tritionl pstorl mngement of the Dehes lnspe, whih is n open, prk-like, svnnh ok (Querus rotunifoli) forest, the most extensive grosilvopstorl system in the Meiterrnen Bsin (Eihhorn et l. 26), minly in the southwestern Ierin Peninsul. Sheep grze the nturl psture in fene poks, were provie with wter, n given no supplementry fee. Experimentl proeures Eh yer on the six frms, the stuy ewes were rnomly selete n then isolte from rms t lest 2 months efore mting. They reeive S/C implnt, t the se of the left er, ontining 8 mg meltonin (Melovine; CEVA Slu Animl, Brelon, Spin) (Meltonin group; n=2,98), or no implnt (Control group; n=89). The eletroni ruminl olus numers of the ewes were reore to ientify their experimentl group. Meltonin implnts were inserte uring the seon hlf of Ferury or erly Mrh (winter). On the y tht ewes were trete, ll the rms reeive three meltonin implnts, oring to the mnufturer s instrutions. To inue rm effet, rms (Merino ree; one rm per 2 ewes) were introue 45 ys fter meltonin tretments, n remine in the flok for further 45 ys. Trete n untrete ewes were kept prt in two isolte groups throughout the mting perio. After the rms were withrwn, the groups on eh frm were omine into single floks, until lming. As it ws not possile to use the sme group of rms in the experimentl groups on the six frms over the 4 yers of the stuy, efforts were me to lne their hrteristis ross groups, i.e. ge, previous sexul experiene, reeing sounness, et. The numer of lms orn per ewe ws etermine every morning from the onset of eh lming perio. In eh yer, rinfll (mm) ws reore from Septemer (utumn) to My (spring) ( griulturl yer ), using t from the losest meteorologil sttion to the six frms, lote t the IFAPA Reserh Centre (Hinojos el Duque, Córo, Spin). The reproutive prmeters ssesse were perentge of ewes lming (numer of ewes lming per ewes presente to rms), perentge of lms orn to ewes lming (numer of live n e lms orn per ewes lming), n overll lming perentge (numer of live n e lms orn per ewes presente to the rm). Sttistil nlysis To test for signifint ifferenes in the responses to meltonin tretment, the reproutive prmeters were nlyse using multinomil logisti regression with ewe s the unit of mesurement, oring to the following moel: Y=X+e, where Y is the n x vetor of reors, enotes the effets in the moel (tretment or not with meltonin, six frms, n four mesurements of rinfll) with the ssoite mtrix X, n e enotes the vetor for resiul effets. To quntify the effet of rinfll on reproutive performne of the experimentl groups, regression nlysis ws use to exmine the reltionship etween perentge of ewes lming, perentge of lms orn to ewes lming n overll lming perentge, n the mount of nnul rinfll. Regression equtions were lulte with group within frm for eh yer s the unit of mesurement (SPSS 4.; SPSS In, Chigo IL, USA). Results For vrious resons, t oul not e reore on 6 in 24 n 5 in 27. Annul rinfll, frm, tretment with meltonin, n their intertions, h signifint effet on the perentge of ewes lming n overll lming perentge (p<.). There ws lso signifint effet on perentge of lms orn per ewe lming (p<.), lthough there were no intertions etween ftors. The effet of meltonin tretment on perentge of ewes lming, perentge of lms orn per ewe lming, n overll lming perentge for eh frm, for the 4 yers of the stuy, re shown in Figures, 2 n 3, respetively. Overll (six frms n the 4 yers omine), tretment with meltonin h signifint effet on the perentge of ewes lming (Meltonin group = 77 (SEM 4)% vs Control group = 44 (SEM 7)%; p<.), perentge of lms orn to ewes lming (Meltonin group = 4 (SEM )% vs Control group = 34 (SEM 2)%; p<.5), n overll lming perentge (Meltonin group = 9 (SEM )% vs Control group = 59 (SEM 2)%; p<.). This stuy onfirme tht meltonin ws effetive t inresing the lming perentge of Merino ewes mte out of seson, n this response ws ssoite with signifint inrese in perentge of ewes lming ross ll yers of the stuy (Tle ). Totl rinfll for eh of the 4 yers of the stuy is shown in Tle. Tretment only improve the perentge of lms orn to ewes lming in 24. The perentge of ewes lming (R 2 =.47; p<.5) n overll lming perentge (R 2 =.49; p<.5) were positively orrelte with nnul rinfll. The orreltions were greter in the Control group ompre with the Meltonin group (R 2 =.69 n R 2 =.73; p<., n R 2 =.36 n R 2 =.44; p<. n p<.5, respetively). There ws only wek orreltion etween nnul rinfll n perentge of lms orn to ewes lming (R 2 =.2). The mount of vrition in reproutive prmeters expline y rinfll (R 2 vlues) ws higher in the Control group thn in the Meltonin group (48% vs 3% for perentge of ewes lming, n 54% vs 9% for overll lming perentge). Thus, the Control group exhiite more vrile lm proution in response to ifferenes in rinfll etween yers, s shown y the ifferent slopes of the regression lines (Figure 4). Disussion In this stuy, tretment of ewes with meltonin resulte in signifint inrese in lm proution. However, the stuy i not ifferentite etween lms orn live or e, n other ftors, suh s oy onition of the ewe, proution of olostrum,

3 Arreol et l. New Zeln Veterinry Journl 57(3), Lms orn/ewes (%) Lms orn/ewes (%) Lms orn/ewes (%) Figure. Men perentge (± SEM) of Merino ewes lming tht were trete ( ) or not t rete ( ) with meltonin in () 24, () 25, () 26, n () 27, on six frms in southwestern Spin. Implnts were given in Ferury-Mrh (winter), n rms introue 45 ys lter. Signifine of ifferene ue to meltonin: p<.5; p<.. Lms orn/ewes (%) Figure 2. Men (± SEM) perentge of lms orn to Merino ewes lming tht were trete ( ) or not trete ( ) with meltonin in () 24, () 25, () 26, n () 27, on six frms in southwestern Spin. Implnts were given in Ferury-Mrh (winter), n rms introue 45 ys lter. Signifine of ifferene ue to meltonin: p<.5; p<.. Tle. Men (± SEM) perentge of ewes lming (numer of ewes lming per ewes presente to the rm), perentge of lms orn to ewes lming (numer of lms orn per ewes lming), n overll lming perentge (numer of lms orn per ewes presente to the rm) of meltonin-trete (M) n untrete (C) Merino sheep on six frms in southwestern Spin over 4 yers (24 27). n % of Ewes lming % of Lms orn to ewes lming Yer Rinfll M C M C M C M C ± 4% x 78 ± 9% y 43 ± 9% x 27 ± % y 34 ± 3% x 8 ± 6% y ± 4% x 36 ± 6% y 35 ± 4% 26 ± 4% 97 ± 3% x 45 ± 4% y ± 4% x 3 ± 6% y 46 ± 8% 47 ± 7% ± 3% x 45 ± 4% y ± 3% x 56 ± 7% y 4 ± 8% 39 ± 6% 2 ± 2% x 78 ± 6% y Totl rinfll reore from Septemer to My of the next yer (mm) x,y Signifint ifferene p<.5

4 44 New Zeln Veterinry Journl 57(3), 29 Arreol et l Figure 3. Men (± SEM) overll lming perentge of Merino ewes tht were trete ( ) or not trete ( ) with meltonin in () 24, () 25, () 26, n () 27, on six frms in southwestern Spin. Implnts were given in Ferury-Mrh (winter), n rms introue 45 ys lter. Signifine of ifferene ue to meltonin: p<.5; p<.. n fee supply, ffet lm survivl. Nevertheless, the overll.5 extr lms/trete ewe reflete n 85% inrese in the overll lm proution on these frms. Aei et l. (27) oserve the sme effet in Merino ewes fter tretment t the sme time of the yer. In this stuy, nnul rinfll n frm lso h signifint effet on the response of Merino ewes trete with meltonin, similr to those oserve in Frne y Chemineu et l. (99), n in the UK y Hresign (992). The intertion etween frm n response to tretment oul e ssoite with rnge of ftors suh s the skill of frmers, onition of the ewes, stress, n Rinfll (mm) Rinfll (mm) 24 Figure 4. Liner orreltions etween () the perentge of Merino ewes lming, n () overll lming perentge, n rinfll over 4-yer perio (24 27) on six frms in southwestern Spin, where ewes were trete (, ) or not trete (, - - -) with meltonin. Implnts were given in Ferury-Mrh (winter), n rms introue 45 ys lter. () Meltonin group: Fertility = rinfll; R 2 =.3; p=.; Control group: Fertility = rinfll; R 2 =.48; p<.. () Meltonin group: Feunity =.9 +.rinfll; R 2 =.9; p<.5; Control group: Feunity =.72 +.rinfll; R 2 =.538; p<.. niml mngement. Ftors suh s reproutive lenr n niml hnling n hve n effet on fertility outomes (Anel et l. 25). Timing of oth tretment n introution of the rms n lso influene the response to tretment (Knight et l. 992). A possile explntion for the effet of nnul rinfll, n to some extent frm, ws ssoite with the nutritionl sttus of the ewes in the perio leing up to n uring mting. Nutrition n hve signifint effet on mny spets of reproution, e.g. seretion of hormones, fertilistion, n evelopment of emryos (Boln et l. 2). Ooytes erive from unerfe ewes yiele fewer lstoysts n h lower rtes of levge n formtion of lstoysts thn i ontrol ewes (Borowzyk et l. 26). This stuy showe the potentil vlue of treting ewes with meltonin when nutrition my e limiting ftor. Assuming tht the low nnul rinfll oserve in this stuy ws ssoite with low nutrition, tretment improve the numer of ewes lming per ewes put to the rm. This response oul hve een ue to more ewes resuming oestrous yles n eoming pregnnt, or more ewes eoming pregnnt fter mting, or omintion of oth; we i not oserve or reor ewes eing mte. However, meltonin ppere to e enefiil to survivl of the emryo (Aei et l. 22, 28; For et l. 26), n oul inrese survivl of the emryo n in-vitro rtes of fertilistion (Vlsi et l. 26). Possily, the effets of rinfll on livestok proution re mostly through the vilility of forge. For instne, the most signifint effet of rought on pstorl frms is the reution in livestok proution use y shortges of foer n reutions in fee qulity (MWillim et l. 24). In our stuy, the shortge

5 Arreol et l. New Zeln Veterinry Journl 57(3), of rin in 25 n 26, whih le to onsierle rought, might hve ontriute to some egree of unernutrition, whih ws reflete y the poor results of the ewes in the Control group in those yers. In ontrst, it oul e interprete tht the Control groups in the wet yers enjoye goo levels of oy onition, whih in turn proue n extension of the reeing seson (For et l. 992), resulting in stisftory fertility results tht my hve overshowe the positive effets of meltonin. In the Spnish Iex (Cpr iex), proution n survivl of offspring were signifintly positively orrelte with nnul preipittion (Esos n Alos 99). The unne of mny Meiterrnen grssln speies in the Dehes is positively orrelte with rinfll, whih oul explin up to 83% of the vrition etween yers (Figuero n Dvy 99). In our stuy, tretments with meltonin ontriute to stle lm proution regrless of the environmentl onitions, eing useful tool for improving lm proution in ry environments, when foo is limite n, possily, sheep re unernourishe. In onlusion, in the Meiterrnen limti region, reproutive mngement strtegy tht is se stritly on photoperioi ues might not e the most suitle, given the pronoune vrition in rinfll etween yers (Mrtin et l. 22). Tretment with meltonin implnts n improve lm proution in Merino ewes, espeilly in hrsh environments where foo is limite euse of low rinfll; however, when meltonin tretment ws use the responses of floks on iniviul frms were iffiult to preit euse within yer, responses i not our on ll frms. Aknowlegements This stuy ws supporte finnilly y RAEA Junt e Anluí, n grnts from Comisión Interministeril pr l Cieni y Tenologí n Diputión Generl e Argón, Spin. Referenes Aei JA, For F, Zuñig O. 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