Impact of Genomic Selection on Inbreeding and Coancestry in Nordic Dairy Cattle

Saija Riitta Tenhunen*, Peer Berg, Morten Kargo, Lars Peter Sørensen, Jørn Rind Thomasen

*Corresponding author for this work

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Abstract

In recent years, Genomic Selection (GS) has accelerated genetic gain in dairy cattle breeds worldwide. Despite the evident genetic progress, several dairy populations have also encountered challenges such as heightened inbreeding rates and reduced effective population sizes. The challenge in dairy cattle breeding is to find a balance between achieving genetic gain and managing genetic diversity within the population, thereby mitigating the negative effects of inbreeding depression. This study aims to elucidate the impact of GS on genomic rates of inbreeding (∆F) and coancestry (∆C) in Nordic Jersey (NJ) and Holstein (NH) cattle populations. Furthermore, key genetic metrics including the generation interval (L), effective population size (Ne), and future effective population size (FNe) were assessed across distinct animal cohorts in both breeds: females, bulls, and approved semen-producing bulls (AI-sires). Two time-periods were studied: before and after GS. Analysis of ∆F and ∆C revealed distinct trends across the studied periods and animal groups. Notably, there was a consistent increase in yearly ∆F for most animal groups in both breeds. An exception was observed in NH AI-sires, which demonstrated a slight decrease in yearly ∆F. Moreover, NJ displayed minimal changes in yearly ∆C between the timeframes, whereas NH exhibited elevated ∆C values across all animal groups. The substantial increase in yearly ∆C within the NH female population was particularly striking, surging from 0.0002 to 0.0039. Implementation of GS has reduced the generation interval across all animal cohorts in both NJ and NH breeds. However, the extent of reduction was more pronounced in males compared to females. This reduction in generation interval influenced generational changes in ∆F and ∆C. Bulls and AI-sires of both breeds exhibited reduced generational ∆F between periods, in contrast to females that demonstrated an opposing pattern. Between the periods, NJ maintained a relatively stable Ne, 29.4 before and 30.3 after GS, while NH experienced a notable decline from 54.3 to 42.8. Female groups in both breeds displayed a negative Ne trend, while males demonstrated either neutral or positive Ne developments. Regarding FNe, NJ exhibited positive FNe development with an increase from 40.7 to 57.2. The opposite was observed in NH, where FNe decreased from 198.8 to 42.7. In summary, GS implementation yielded positive outcomes within the NJ population. Moreover, analysis of coancestry hints at potential avenues to mitigate future ∆F through informed mating strategies. Conversely, the NH population faces more pressing concerns with rapid increase of inbreeding and coancestry, even though ∆F remains comparatively modest in contrast to what has been observed in other Holstein populations. This underscores the urgency for strategic interventions within the Nordic breeding scheme to ensure the long-term sustainability of the Nordic dairy populations in the forthcoming years.
Original languageEnglish
Title of host publicationMaataloustieteen Päivät 2024 10.–11.1.2024 Viikki, Helsinki : ESITELMÄ- JA POSTERI-TIIVISTELMÄT
EditorsTuula Puhakainen, Venla Jokela
Publication date2024
Pages43
ISBN (Electronic)978-951-9041-69—8
Publication statusPublished - 2024
EventAgricultural Science Days 2024: Maataloustieteen Päivät 2024 - Viiki, Helsinki, Finland
Duration: 10 Jan 202411 Jan 2024
https://www.smts.fi/fi/MTP2024

Conference

ConferenceAgricultural Science Days 2024
LocationViiki
Country/TerritoryFinland
CityHelsinki
Period10/01/202411/01/2024
Internet address
SeriesSuomen Maataloustieteellisen Seuran Tiedote
Volume41
ISSN0358-5220

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