A sheep with glowing DNA, symbolizing genetic breakthroughs in sheep breeding.

Decoding Sheep Fertility: Can Genes Unlock Better Lambing?

Samir D’Costa in Science & Nature September 2025 • 4 min read.

"Scientists explore the roles of BMPR1B, BMP15, and GDF9 in ewes to improve breeding and prolificacy, offering new hope for farmers."

For meat sheep farmers, maximizing the number of lambs born per ewe is a top priority. The ability to increase litter size can significantly improve the economic efficiency of sheep production. For years, scientists have been trying to unravel the genetic factors that influence fertility in sheep, with the goal of identifying ways to naturally enhance prolificacy through selective breeding.

Recent studies have focused on three key genes: BMPR1B, BMP15, and GDF9. These genes play crucial roles in the complex processes of ovulation and follicular development. By understanding how these genes function and interact, researchers hope to unlock new strategies for improving sheep fertility.

A groundbreaking study examined the expression of these three genes in Small Tail Han (STH) ewes, a breed known for its high fertility. The research looked at different genotypes of the FecB gene, which is closely linked to prolificacy, to see how it affects the activity of BMPR1B, BMP15, and GDF9. The findings offer valuable insights into the molecular mechanisms that drive fertility in sheep and pave the way for innovative breeding approaches.

The Genetic Trio: How BMPR1B, BMP15, and GDF9 Influence Sheep Fertility

A sheep with glowing DNA, symbolizing genetic breakthroughs in sheep breeding.

The study targeted Small Tail Han (STH) ewes, separating them into groups based on their FecB genotypes: FecB BB, FecB B+, and FecB ++. Scientists then analyzed gene expression in various tissues, including major organs and the hypothalamic-pituitary-gonadal (HPG) axis, which controls reproductive functions. This comprehensive approach allowed researchers to pinpoint where and how these genes exert their influence.

Here’s a breakdown of the key findings:

BMPR1B: Found in all tested tissues of FecB BB ewes, with high expression in the brain, cerebellum, hypothalamus, pituitary, ovaries, uterus, and adrenal glands of FecB B+ and FecB ++ ewes.
BMP15: Primarily expressed in the ovaries of all three FecB genotypes.
GDF9: Present in all 14 tissues across all sheep, highlighting its widespread role.

Further analysis revealed that while BMPR1B expression remained consistent across the different FecB genotypes, GDF9 and BMP15 showed higher expression in FecB B+ ewes. This suggests that the FecB B+ genotype, which is associated with increased prolificacy, may benefit from enhanced activity of GDF9 and BMP15 in the ovaries.

Future Implications: Breeding for Better Fertility

This study provides a detailed look at the expression patterns of BMPR1B, BMP15, and GDF9 genes in STH sheep with different FecB genotypes, and contributes to the understanding of the molecular mechanisms that regulate fertility in sheep. By identifying the key genes and genotypes associated with increased prolificacy, breeders can make informed decisions to improve lamb production.

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This article is based on research published under:

DOI-LINK: 10.3390/ani8100166, Alternate LINK

Title: Expression Analysis Of The Prolific Candidate Genes, Bmpr1B, Bmp15, And Gdf9 In Small Tail Han Ewes With Three Fecundity (Fecb Gene) Genotypes

Subject: General Veterinary

Journal: Animals

Publisher: MDPI AG

Authors: Jishun Tang, Wenping Hu, Ran Di, Qiuyue Liu, Xiangyu Wang, Xiaosheng Zhang, Jinlong Zhang, Mingxing Chu

Published: 2018-09-28

Everything You Need To Know

What roles do the BMPR1B, BMP15, and GDF9 genes play in sheep fertility, and why are they important for farmers?

BMPR1B, BMP15, and GDF9 genes are crucial in the ovulation and follicular development processes in ewes. Understanding the function and interaction of these genes can lead to strategies to enhance sheep fertility through selective breeding. This is important for farmers because increasing the number of lambs born per ewe can significantly improve the economic efficiency of sheep production. Further research into other genes affecting litter size could lead to even more effective breeding programs.

How was the expression of BMPR1B, BMP15, and GDF9 genes studied in Small Tail Han (STH) ewes, and what were the different groups?

The expression of BMPR1B, BMP15, and GDF9 genes was studied in Small Tail Han (STH) ewes by separating them into groups based on their FecB genotypes: FecB BB, FecB B+, and FecB ++. Scientists then analyzed gene expression in various tissues, including major organs and the hypothalamic-pituitary-gonadal (HPG) axis, which controls reproductive functions. This allowed researchers to pinpoint where and how these genes exert their influence. Other breeds were not covered in this study but it is useful to understand the genetic variation across breeds.

What do the expression patterns of BMPR1B, BMP15, and GDF9 genes reveal about the FecB genotypes in STH sheep?

The study revealed that BMPR1B was found in all tested tissues of FecB BB ewes, with high expression in the brain, cerebellum, hypothalamus, pituitary, ovaries, uterus, and adrenal glands of FecB B+ and FecB ++ ewes. BMP15 was primarily expressed in the ovaries of all three FecB genotypes, and GDF9 was present in all 14 tissues across all sheep. GDF9 and BMP15 showed higher expression in FecB B+ ewes, suggesting that the FecB B+ genotype may benefit from enhanced activity of GDF9 and BMP15 in the ovaries. The study did not discuss the implications of different levels of expression of these genes in other tissues.

How can breeders use the findings about BMPR1B, BMP15, and GDF9 genes to improve lamb production?

By identifying the key genes (BMPR1B, BMP15, and GDF9) and genotypes (particularly the FecB B+ genotype) associated with increased prolificacy, breeders can make informed decisions to improve lamb production through selective breeding. This involves selecting ewes with the FecB B+ genotype to enhance the activity of GDF9 and BMP15 in the ovaries, potentially increasing the number of lambs born per ewe. However, the long-term effects of selectively breeding for these specific genotypes needs to be considered. For instance, the possible negative impacts on genetic diversity or overall health. These aspects are not addressed.

What is the significance of the hypothalamic-pituitary-gonadal (HPG) axis in the context of sheep fertility and the expression of BMPR1B, BMP15, and GDF9?

The hypothalamic-pituitary-gonadal (HPG) axis plays a central role in controlling reproductive functions in sheep. By analyzing gene expression in the HPG axis, researchers can understand how BMPR1B, BMP15, and GDF9 influence the hormonal regulation of ovulation and follicular development. Specifically, the HPG axis involves the hypothalamus releasing GnRH (gonadotropin-releasing hormone), which stimulates the pituitary gland to release LH (luteinizing hormone) and FSH (follicle-stimulating hormone). These hormones then act on the ovaries to regulate follicular development and ovulation, where BMP15 and GDF9 are critical. The study's comprehensive approach of examining gene expression within the HPG axis provides valuable insights into the molecular mechanisms regulating fertility. The HPG axis interacts with other systems and hormones that the article does not directly address, such as the role of nutrition and environmental factors in modulating its function and therefore, fertility.