GENETICS OF LITTER SIZE COMPONENTS

Researchers: A. BLASCO, N. IBAÑEZ, M. A. SANTACREU (Universitat Politècnica de València) and M.J. ARGENTE,  M.L. GARCIA (Universidad Miguel Hernández)

Response to selection for litter size in pigs and rabbits has been lower than predicted in all programs or experiments. This has lead to research about genetics of litter size components with the final objective of increasing litter size by indirect selection. In this research line we focus on the genetic determination of ovulation rate, pre- and post- implantation survival,  uterine capacity and embryo development. We also investigate the genetics of litter size environmental variance, a new field in prolific species. Experiments use rabbit as a livestock production itself, but also as an experimental model useful for other species.

1. Genetics of uterine capacity: Two lines were divergently selected on uterine capacity for ten generations, and they were crossed to produce a F2 population. We studied the genetic determination of litter size components and embryo development. Three SNPs explaining a large part of the between lines differences in litter size and embryo survival  were found. A GWAS detected a genomic region on chromosome 17 with important effect on litter size traits.

2. Genetics of ovulation rate: A line was selected for ovulation rate for ten generations. Response to selection was obtained for ovulation rate, but not for litter size.

3. Selection for ovulation rate and litter size: A line was selected by independent levels for ovulation rate and litter size. Response to selection was obtained for ovulation rate, and also for litter size, although similar to the one obtained in other lines for direct selection for litter size.

4. Divergent selection for litter size variability: We have modified the environmental variability of litter size by selection. The homogeneous line has less stress susceptibility and better resistance to disease, and consequently a better welfare.

5.Genomics, metabolomics, metagenomics and meta-metabolomics of litter size variability :  We analyse all these -OMICS in the divergent lines selected for litter size variability, with the objective of a better understanding of the metabolic routes driving stress and disease resistance related to litter size variability, and the genes implied on them. The -OMICS integration is also a challenge that will lead to a better knowledge of all processes implied.