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HESTEFORSK FeNomen: Fertility in national Norwegian horse breeds R-21-47-575

Alternative title: FeNomen: Fertilitet hos nasjonale norske hesteraser.

Awarded: NOK 3.0 mill.

The three national Norwegian horse breeds, the Dole horse, the Fjord horse, and the Nordland/Lyngen horse are all listed on the FAOs list of endangered breeds. Decreasing population sizes and risk of rapid accumulation of inbreeding is a concern. The number of covered mares has decreased by 37% to 45% in the past decade compared to the one preceding it. Foaling rates in the Nordland/Lyngen is satisfactory, whereas for the Dole and the Fjord rates are suboptimal. The overall aim of this project is to obtain knowledge on how to improve reproductive health in these breeds. The first part we have used registry data to investigate factors that limit reproductive performance. Preliminary results show that increasing age of the mare negatively influence reproductive performance. Also, fertility status after the previous cover affects reproductive performance. Compared to mares with foal at foot, barren mares and mares covered for the first time were less likely to have a live-born foal. Part 2 deals with genetic analysis. In small populations genetic causes of reduced fertility must be considered. To identify genes which negatively impact on reproductive performance we need to collect DNA for a large population, therefore this investigation will be performed only for Fjord horses. For genotyping we have retrieved 60% of the samples needed. Reproduction involves more than simply genetic components; breeding management is important and therefore part 3 will be a small-scale pilot study on reproductive disorders. The mares included will receive ultrasonographic examination of uterus and the ovaries, and bacteriological, cytological, and endometrial (biopsy) evaluation. So far, we have had 7 mares submitted to a full examination, based on the caseloads it is too early to conclude. We also aim to examine a few stallions. Low concentration of motile spermatozoa, and high percentages of morphologically abnormal spermatozoa has been shown to affect stallion fertility negatively. Part 3 will be reserved for Dole mares and stallions. Part 4 consists of communicating results from the project out to horse owners, breeders and the horse sector in general. The Norwegian Horse Association, the Norwegian Fjord Horse Center, the National Center for Nordland/Lyngen horse and the breeding organizations are central partners. We have presented the project to stakeholders at the joint meeting for national breeders and at 1 webinar. We have presented preliminary results at one international conference, and at stakeholder meetings for “Norges Fjordhestlag” and “Landslaget for Dølahest”, respectively. We have written 7 articles in breed periodicals, 5 articles for online webpages and participated in 2 news pieces.

Decreasing population sizes and risk of accumulation of inbreeding is a challenge for the national Norwegian horse breeds; the Dole, the Fjord and the Nordland/Lyngen. The average breed-specific reduction in covered mares is between 37% and 45%, when comparing the years 2000 to 2009 to the years 2010 to 2018. Foaling rates in the Nordland/Lyngen is satisfactory, whereas for the Dole and the Fjord rates are suboptimal. The aim of this project is to obtain science-based knowledge on how to improve reproductive health in these breeds with particular focus on epidemiological factors, management of inbreeding and identification of recessive mutations causing embryonic death. Reasons for reproductive failure will be addressed combing use of registry data, genomic analysis, and a pilot field study. Breeding recommendations that account for identified mutations may increase fertility and prevent these mutations from drifting to higher frequencies. By communicating results to horse owners, breeders and the breed organizations, the project will contribute to sustainable populations of national Norwegian horses.

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