Direct and maternal effects on calving ease in heifers and second parity Piemontese cows

Transcription

1 Dirct and atrnal ffcts on calving as in hifrs and scond parity Pionts cows Paolo Carnir 1, Riccardo Dal Zotto 1, Andra Albra, and Marco Bona 1 Dpartnt of Anial Scinc, Univrsity of Padua, Agripolis, 35 Lgnaro (PD), Italy. Eail:carnir@agripolis.unipd.it Associazion Nazional Allvatori Bovini Razza Pionts, Strada Trinità 3/A, 161 Carrù (CN), Italy. Eail:anaborapi@araco.it Abstract Gntic paratrs wr stiatd for dirct and atrnal ffcts on calving as scors of calvs born fro first and scond parity Pionts cows. Th data consistd of 97,493 and 76,478 calving rcords of first and scond parity cows, rspctivly. Du to coputing liitations, stiation of (co)varianc coponnts was carrid out on sapls xtractd fro th availabl data fils. Fiv sapls of approxiatly, first calving rcords wr obtaind using a rando sapling procdur on hrds. Scond calving rcords of sapld hifrs wr usd to crat sapls of scond parity data. (Co)varianc coponnts wr stiatd using a REML anial odl procdur considring all known rlationships. Calving as obsrvations consistd of subjctiv scors into fiv catgoris: noral dlivry (unassistd), dlivry assistd by th farr, hard pull or vtrinary aid, casarian and ftotoy. Th linar odl includd th fixd ffct of hrd, ag of th da-sx of th calf, yar-sason of calving and two rando ffcts: th additiv gntic ffct of th calf (dirct ffct) and th additiv gntic ffct of th da (atrnal ffct). Dpnding upon th sapl, stiats of hritability for th dirct gntic ffct in first parity cows rangd fro.1 to.19. Estiats of hritability for th atrnal ffct in hifrs wr lowr (.7-.11) than thos for th dirct ffct. For scond calving data, stiatd hritabilitis for dirct and atrnal gntic ffcts wr siilar (.7 and.8, rspctivly). Gntic corrlation btwn dirct and atrnal ffcts was highly ngativ (-.4) in both hifrs and scond parity cows. 1. Introduction Calving as is an conoic iportant trait in bf cattl and its iportanc is strssd furthr by currnt brding progras usd in bf cattl aid to iprov traits that, as daily wight gain and carcass flshinss, xhibit antagonistic gntic rlationships with as of calving. Evn though dystocia, dfind as a dlayd and difficult parturition, is not ncssarily associatd to loss of th calf or of th da, incrasd costs, du to additional farr labour, vtrinary fs, subsqunt halth and frtility probls, and ngativ ffcts on production traits, ar gnrally xpctd whn difficult births occur. Fro a biological point of viw, calving prforancs ar affctd by two coponnts (Mijring, 1986): th ability of th da to giv births asily (atrnal ffct) and th ability of th calf to b born asily (dirct or ftal ffct). Litratur stiats of hritability for dirct and atrnal ffcts on calving as ar gnrally low and a nubr of studis rportd antagonistic gntic rlationships btwn dirct and atrnal ffcts. Thus, slction for rducing calving probls du to dirct ffcts (siz of th calf) only, is xpctd to xrt ngativ ffct on th atrnal coponnt. An additional probl rlatd to calving prforanc is th diffrnt gntic natur of dystocia in hifrs copard to ultiparous cows. In th Pionts brd, slction of young bulls for bf traits is basd on rsults of th prforanc tsting progra. Gntic valuation for th dirct ffct on calving as of slctd bulls is basd on calving rcords of th progny originatd by atings with cows whras us of young bulls on hifrs is avoidd. Hnc, slction for th dirct ffct rlis ostly on calving rcords fro cows. Most studis on calving as in dairy cattl hav found corrlations btwn calving prforanc and production traits clos to zro. Convrsly, in bf cattl, traits, lik daily gain and uscularity, xhibit unfavourabl gntic associations with calving as (Mijring, 1986). As a consqunc, a ngativ corrlatd rspons in calving prforanc is xpctd whn slction progras aid to iprov such traits ar applid. This study was aid to invstigat th gntic aspcts of calving prforanc in th Pionts brd and to stiat gntic paratrs for dirct and atrnal ffcts on this trait sparatly in hifrs and cows. 1

2 . Matrials and thods.1 Data and diting procdurs Th data usd in this study consistd of 97,493 and 76,478 calving rcords of first and scond parity Pionts cows, rspctivly. Calving rcords wr collctd in 1,993 hrds btwn 1989 and Calving rcords wr rovd whn gstation lngth or sx of th calf was unknown and whn calving scor was issing. Prissibl rang of ag at calving was fro 1 to 37 onths in hifrs and fro 31 to 65 onths in scond parity cows. Rcords fro twin births wr xcludd fro th data usd in th following analyss. Calvs wr rquird to hav both th sir and th da known. Calving prforanc was scord into fiv catgoris: noral dlivry (unassistd), dlivry assistd by th farr, hard pull or vtrinary aid, casarian and ftotoy. Basd on prliinary analyss, two sasons of calving (Novbr-April and May-Octobr), and four gstation lngth classs (6-8, 81-9, 91-3, and 31-3 d) wr dfind. Ag at calving data wr groupd in 8 and 15 classs for hifrs and cows, rspctivly.. Statistical thods Prliinary analyss wr carrid out using gnral linar odl procdur of SAS and all availabl calving rcords. Ths analyss wr prford sparatly on hifrs and scond parity cows data. Diffrnt linar odls wr fittd aiing to idntify fixd ffcts that affctd variation of s. Th ultiat odl includd th fixd ffct of hrd, yar-sason of calving, ag of th da-sx of th calf and gstation lngth. Ths ffcts wr includd in th ixd odl that was usd latr to stiat (co)varianc coponnts. Estiation of (co)varianc coponnts was prford through a REML procdur using th VCE packag ( Gronvld, 1996). Th ixd odl was as follows y = Xb+ Z d + Z + d whr: y is vctor of s b is a vctor of fixd ffcts d is a vctor of rando dirct additiv gntic ffcts on s (calf ffct) is a vctor of rando atrnal additiv gntic ffcts on s (da ffct) is a vctor of rando rsiduals X, Z d, and Z ar known incidnc atrics that link ffcts to s Th (co)varianc structur assud for th rando trs of th odl was V d = d d d Iσ whr: A is a atrix of additiv gntic rlationships aong anials I is an idntity atrix σ d is th additiv gntic varianc coponnt of dirct ffcts on s σ is th additiv gntic varianc coponnt of atrnal ffcts on s σ d is th additiv gntic covarianc coponnt btwn dirct and atrnal ffcts is th rsidual varianc coponnt σ Du to coputing liitations, stiation of (co)varianc coponnts using all availabl rcords was unfasibl. Thrfor, sapls wr drawn fro th data fil applying a rando sapling procdur on hrds. Hrds wr sapld by gnrating rando nubrs fro a unifor distribution and picking up all calving rcords prtaining to th hrd locatd, in th list of hrds, at th position corrsponding to th gnratd rando nubr. This sapling was rpatd as any tis as ndd to gt a iniu nubr of, first calving rcords in th sapl. Fiv diffrnt sapls of first calving rcords wr drawn using th aforntiond procdur. Scond calving rcords of sapld hifrs wr usd to crat fiv sapls of scond parity data.. For ach sapl, a fil including all known rlationships aong anials was xtractd fro th pdigr fil of th Italian Association of Pionts Brdrs (Anaborapi). No gntic grouping was usd in th REML stiation analyss. 3. Rsults and discussion 3.1 Calving scors and non gntic ffcts Frquncis of s in hifrs and scond parity cows data ar rportd in Figur 1. Most calvings wr scord as assistd by th farr both in hifrs and in scond parity cows and frquncy of noral dlivris (unassistd) was rlativly low. Howvr, it can b hardly statd that assistanc during th parturition was a rsult of or difficult births. Instad, it can b argud that assistanc during th parturition is givn by th farr vn in calvings that ight nd with a noral dlivry. 13

3 Incidnc of or difficult births (hard pull, casarian and ftotoy) was as xpctd highr in hifrs than in scond parity cows. Estiatd last squars ans of gstation lngth, ag-sx and yar-sason of calving ffcts obtaind in th prliinary analysis of all availabl calving rcords ar rportd in figurs, 3 and 4, rspctivly. Incrass in gstation lngth rsultd in or difficult calvings in both hifrs and cows (figur ). Philipsson (1976) rportd that th rlationship btwn gstation lngth and calving as xhibits thrshold proprtis. Howvr, thr is no vidnc of a non-linar rlationship fro th rsults of th prsnt study. Th sx of th calf xrtd a ajor ffct on calving prforanc (figur 3). Mal calvs had or difficult births than fal calvs. Diffrnc in s du to th sx of calf ffct was uch highr in hifrs than in scond parity cows. Ths rsults ar in agrnt with rsults fro othr studis (Mijring, 1986). Ag at parturition of hifrs had significant ffcts on s. Calving scors wr highr whn hifrs calvd at a young ag (figur 3). Th agnitud of th ag ffct in scond parity cows was sall. With rspct to yar-sason of calving, both hifrs and cows that calvd in sason 1 (Novbr-April) had slightly highr s than das calving in May-Octobr. 3. Gntic paratrs and ffct of data sapling Charactristics of sapld data sts ar rportd in tabl 1. Avrag nubr of first calving rcords pr yar and pr hrd was.7. Du to th sall avrag hrd siz and to avoid us of hrd classs, th hrd-yar ffct was not includd in th odl of analysis and a choic of fitting hrd and yar-sason as sparat ffcts was ad. Narly 78% of hifrs had th opportunity of a scond calving. Total nubr of anials considrd in th analysis rangd fro 53,381 and 66,13. Estiats of (co)varianc coponnts obtaind in th analysis of hifrs calving prforanc ar rportd in tabl. Estiats of additiv gntic varianc coponnts for dirct ffcts wr highr than thos for atrnal ffcts in all th fiv sapls. Hritability stiats for dirct ffcts on s rangd fro.1 to.19. Variation of hritability stiats for atrnal ffcts du to sapling of data was lowr. Th stiatd gntic corrlation btwn dirct and atrnal ffcts on s was ngativ in all th fiv sapls but th siz of th corrlation was gratly influncd by th sapling of data. Th agnitud of th stiat rangd fro -.55 to -.7. Avrag hritability for dirct ffcts was narly two tis highr than that for atrnal ffcts. Gntic paratrs rcovrd in th analysis of scond parity cows data ar in tabl 3. Th ffct of sapling of data on stiatd paratrs was lowr than that obsrvd for hifrs s. Valus of hritability stiats for th dirct ffct on s in cows wr narly half th valus obtaind with hifrs data. Ths stiats fit wll in th litratur rangs (Thopson t al., 1981; Gron t al., 1995, Gron t al. 1998). Changs in atrnal ffct hritability wr sall. Again, th corrlation btwn dirct and atrnal gntic ffcts was ngativ and its agnitud was siilar to that obtaind in analyss of hifrs calving data. 4. Conclusions This study stiatd gntic paratrs for calving scors in Pionts hifrs and scond parity cows. Gntic variation of dirct ffcts on calving prforanc in hifrs was uch highr than that obsrvd in scond parity cows. No vidnc of diffrncs in gntic variation of atrnal ffcts btwn Pionts hifrs and cows was found. Th gntic corrlation btwn dirct and atrnal ffcts on as of calving was ngativ. Furthr invstigations on th gntic rlationship btwn calving prforanc of hifrs and of cows ar ndd. Acknowldgnt Apprciation is xprssd to Eildrt Gronvld for th us of th VCE packag. Rfrncs Gron, A.F., Brandts, A.G.B.M, Jansn, H.H., and Kanis, E Econoic valu and gntic paratrs for calving prforanc in Dutch dairy cattl brding. Intrbull bullttin no. 11. Gron, A.F., Van Aubl, J.P.J.M., and Hulzbosch A.A Calving prforanc in dairy cattl - Influnc of aturity of da on th corrlation btwn dirct and indirct ffcts. Proc. 6th WCGALP, Aridal, Australia. Gronvld, E REML VCE: a ultivariat ulti-odl rstrictd axiu liklihood (co)varianc coponnt stiation packag. Vrsion 3.. Usr s guid. 5 pp. Mijring, A Dystocia in dairy cattl brding with spcial attntion to sir valuation for catgorical traits. Ph.D. Diss., Wagningn Agric. Univ., Wagningn, Th Nthrlands. Philipsson, J Studis on calving difficultis, stillbirth and associatd factors in Swdish cattl brds. III. Gntic paratrs. Acta Agricultura Scandinavica 6:

4 Thopson, J.R., Fran A.E., and Brgr P.J Ag of da and atrnal ffcts for dystocia in Holstins. Journal of Dairy Scinc 64: Tabl 1. Charactristics of sapld data sts hifrs cows sapl Rcords,31,7,1,9,1 15,547 15,417 15,996 15,7 15,967 Anials (*) 65,15 66,13 65,35 64,95 65,48 53,831 54,34 54,933 54,7 55,9 Hrds (*) Including anials without rcords Tabl. Estiats of gntic paratrs for dirct and atrnal ffcts on s in first parity cows Sapl Avrag Dirct varianc Matrnal varianc Dirct - atrnal covarianc Rsidual varianc h dirct h atrnal r g dirct-atrnal Tabl 3. Estiats of gntic paratrs for dirct and atrnal ffcts on s in scond parity cows Sapl Avrag Dirct varianc Matrnal varianc Dirct - atrnal covarianc Rsidual varianc h dirct h atrnal r g dirct-atrnal % asy assistd hard pull casarian ftotoy Figur 1. Frquncy of s 15

5 days Figur. Effct of gstation lngth on s < >63 ag class of th da < >35 ag class of th da Figur 3. Effct of ag at parturition and sx of th calf ( al calf fal calf) yar yar Figur 4. Effct of yar-sason of calving ( Novbr-April May-Octobr) 16