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Inbreeding depression due to different age classes of inbreeding on production and fertility traits in Canadian Holsteins.

B. O. Makanjuola

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06-24-2020

Abstract:

298
Inbreeding depression due to different age classes of inbreeding on production and fertility traits in Canadian Holsteins.
B. O. Makanjuola*1, C. Maltecca2,1, F. Miglior3,1, F. S. Schenkel1, C. F. Baes1,4. 1Centre for Genomic Improvement of Livestock, Department of Animal Biosciences, University of Guelph Guelph, ON, Canada, 2Department of Animal Science and Genetics Program, North Carolina State University Raleigh, 3Ontario Genomics Toronto, ON, Canada, 4Institute of Genetics, Vetsuisse Faculty, University of Bern Bern, Switzerland.

The reduction in the mean phenotypic performances of livestock animals could be attributed to rising inbreeding levels. However, this observed decline may not be caused by the total number of inbreeding. Therefore, partitioning inbreeding into different age classes could help in assigning detrimental effects to different classes. The aim of this study seeks to investigate the effect of recent and ancient inbreeding on production and fertility traits in Canadian Holstein cattle. Phenotypic records of 46,430 cows with birth year ranging from 2007 to 2017 were available for production and fertility traits. These animals had 50K genotype data and pedigree records, which comprised of 259,871 individuals. Inbreeding coefficients were estimated using traditional pedigree measures (FPED) and genomic pedigree measures using segment-based (FROH) and marker-by-marker (FGRM) based approaches. Additionally, both pedigree and genomic inbreeding were partitioned into different classes by tracing the pedigree back to a specific generation and using the specific length of homozygous segments to represent different classes, respectively. Inbreeding depression was found for all production and most fertility traits, for example, every 1% increase in FPED, FROH and FGRM was observed to cause a −44.71, −40.48 and −48.72 kg reduction, respectively, in 305-d milk yield. Similarly, an extension in the first service to conception (FSTC) of 0.29, 0.24 and 0.31 d in heifers was found for every 1% increase in FPED, FROH and FGRM, respectively. Partitioning both pedigree and genomic inbreeding into age classes resulted in recent age classes showing more unfavorable inbreeding effects, while more distant age classes caused a more favorable effect. For example, we observed a −1.56 kg loss in 305-d protein yield for every 1% increase in the most recent pedigree age class, whereas 1.33 kg gain was found per 1% increase in the most distant pedigree age class. In this study, we found heterogeneous effect of inbreeding by partitioning inbreeding into different age classes.

Keywords: inbreeding depression, recent and ancient inbreeding, pedigree and genomic inbreeding.

Biography: Bayode is a Ph.D. student in the Department of Animal Biosciences at the University of Guelph under the supervision of Dr. Christine Baes. I have a keen interest in the genetic diversity of livestock animals and how this available diversity can be conserved to allow for further genetic progress.