ASSOCIATION OF NUMBER OF ARTIFICIAL INSEMINATIONS PER PREGNANCY IN HOLSTEIN DAIRY COWS WITH POLYMORPHISM IN LUTEINIZING HORMONE RECEPTOR AND FOLLICLE STIMULATING HORMONE RECEPTOR GENES

Abstract

Failure to become pregnant is the primary reason for a dairy cow to be culled from the production herd. A cow that is cycling normally, with no reproductive abnormalities, but has failed to conceive after at least three successive inseminations may cause economic losses in dairy farms. The present study aimed to examine the association between follicle-stimulating hormone receptor (FSHR) and luteinizing hormone receptor (LHCGR) genes polymorphisms and number of artificial inseminations in the Holstein cattle breed, raised in Turkey. A total of 264 Holstein cows were included in this study, consisting of 222 cows which had undergone a low number of artificial inseminations (two or less inseminations; LI) and 42 cows with a high number of artificial inseminations (three or more inseminations; HI). The polymerase chain reaction followed by restriction fragment length polymorphism method was used to determine the FSHR-AluI and LHCGR-HhaI DNA variants. Three genotypes (CC, CG and GG) were observed for the FSHR gene in LI and HI cows. No statistical difference was found among LI and HI animals for the FSHR genotypes (P=0.934). However, only the CC genotype was detected in LI cows whereas the CC, CT and TT genotypes were detected in HI cows for the LHCGR gene. The genotype frequency of CC was found to be highest (93%) in the HI animals and an association between LHCGR genotypes and the number of artificial inseminations per pregnancy was identified (P<0.001). This is the first report to describes an association between FSHR and LHCGR polymorphisms and number of artificial inseminations in cows. Key words: candidate genes; pregnancy; cow; number of artificial inseminations; polymorphism POVEZAVA MED ŠTEVILOM UMETNIH OSEMENITEV IN POLIMORFIZMOM GENOV ZA RECEPTOR ZA LUTEINIZIRAJOČI HORMON IN RECEPTOR ZA FOLIKLE STIMULIRAJOČI HORMON PRI KRAVAH MOLZNICAH PASME HOLSTEIN Težave z obrejitvijo so glavni razlog za izločitev krav molznic iz proizvodne črede. Krave z normalnim ciklusom, brez reproduktivnih motenj, ki se ne obrejijo po vsaj treh zaporednih osemenitvah, so vzrok za velike ekonomske izgube na mlečnih farmah. V opisani raziskavi smo proučevali povezavo med genskimi polimorfizmi v genih za receptorje za folikle stimulirajoči hormon (FSH-R), genih za receptorje za luteinizirajoči hormon (LH-R) ter številom umetnih osemenitev pri kravah pasme hlstein, vzrejenih v Turčiji. V raziskavo je bilo vključeno skupno 264 krav holstein, od katerih jih je bilo 22, osemenjenih največ dvakrat do obrejitve (skupina LI), in 42 krav, ki so bile osemenjene trikrat ali večkrat (skupina HI). Preiskovane gene smo pomnožili v verižni reakciji s polimerazo in nato izvedli pregled dolžine razrezanih odsekov DNK ( metoda RFLP) z namenom, da bi določili prisotnost različic genov FSHR-AluI in LHR-HhaI pri preiskovanih živalih. Tri različice genotipa (CC, CG in GG) so bile ugotovljene pri genu za FHSR pri kravah v skupinah LI in HI, med skupinama pa ni bilo statistično značilnih razlik v pogostnosti posameznih genotipov (p = 0,934). Pri genu za LHR je bil ugotovljen genotip CC le pri kravah iz skupine LI, ostale tri variante genotipa (CC, CT in TT) pa so bile ugotovljene pri kravah iz skupine HI. Pogostnost genotipa CC je bila najvišja (93 %) pri živalih iz skupine HI, pri statistični analizi pa smo ugotovili povezavo med genotipi LH-R in številom umetnih osemenitev (p <0,001). Ključne besede: FSH-R, LH-R; obrejitev; krava; število umetnih osemenitev; polimorfizem