Fecundity genes in sheep.

Area of Science:

• Animal Genetics
• Reproductive Biology
• Sheep Breeding

Background:

• Increasing interest since 1980 in identifying and utilizing major genes for prolificacy in sheep.
• Mutations in BMPR-1B, BMP15, and GDF9 genes are known to increase ovulation rates.
• Other prolificacy genes exist, indicated by inheritance patterns, but their mutations are not yet located.

Purpose of the Study:

• To review identified major genes influencing prolificacy in sheep.
• To describe the inheritance patterns and effects of these prolificacy genes.
• To highlight the role of DNA testing in sheep genetic improvement.

Main Methods:

• Literature review of identified prolificacy genes in sheep.
• Analysis of inheritance patterns (autosomal dominant, over-dominant, X-linked).
• Examination of mutation effects on ovulation rate and associated phenotypes.

Main Results:

• Mutations in BMPR-1B, BMP15, and GDF9 increase ovulation rates.
• BMP15 has four identified mutations, all yielding the same phenotype.
• Inheritance modes vary: autosomal dominant (BMPR-1B), autosomal over-dominant (GDF9), X-linked over-dominant (BMP15), X-linked maternally imprinted (FecX2).
• Mutation effects range from 0.4 (FecX2) to 1.5 (BMPR-1B) extra ovulations per oestrus.

Conclusions:

• Several major genes significantly impact sheep prolificacy.
• Understanding gene inheritance and effects is crucial for breeding programs.
• DNA tests facilitate marker-assisted selection for genetic improvement of prolificacy in sheep.