A growing body of research is uncovering new uses for existing medications across species. One such example is metformin, a drug primarily used to manage type 2 diabetes and polycystic ovary syndrome (PCOS) in humans, which has now been shown to significantly improve reproductive health and productivity in broiler breeder hens.
Broiler breeder hens are selected for their ability to produce fast-growing meat chickens. However, the intensive genetic selection for rapid growth has resulted in unintended reproductive challenges. These hens often develop ovarian dysfunction characterized by excessive follicular recruitment, disrupted hormone levels, and a decline in egg production and fertility—problems that closely mirror PCOS symptoms in women.
To investigate the potential role of metformin in alleviating these reproductive problems, researchers conducted a comprehensive 40-week study involving 180 hens. The hens were divided into four groups and fed diets supplemented with 0, 25, 50, or 75 mg/kg body weight of metformin.
Major Outcomes
The findings were compelling and multifaceted, pointing to a range of physiological improvements in the metformin-treated groups:
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Body Weight and Fat Reduction: Hens receiving the highest metformin dose (75 mg/kg) showed significantly reduced body weight and abdominal fat pad mass. These changes suggest that metformin may help control excessive weight gain in broiler breeders, which is known to negatively affect reproductive health.
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Restoration of Normal Ovarian Function: In untreated hens, ovarian dysfunction was marked by an abnormal number of large yellow follicles (LYFs), indicating an over-recruitment of follicles. Metformin supplementation, particularly at higher doses, restored a more natural follicular hierarchy. This adjustment is important because the presence of too many dominant follicles can interfere with regular ovulation and egg laying.
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Improved Egg Production and Hatchability: Hens treated with 50 or 75 mg/kg of metformin laid significantly more eggs and demonstrated higher fertility and hatchability rates, particularly at 65 weeks of age—a time when reproductive performance typically declines.
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Hormonal Balance: Metformin altered circulating reproductive hormone levels, notably reducing plasma testosterone and the testosterone-to-androstenedione ratio. Elevated testosterone is associated with reproductive dysfunction, so this hormonal shift likely played a central role in restoring ovarian activity.
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Upregulation of Key Ovarian Genes: The treatment enhanced the expression of genes involved in steroidogenesis, such as STAR, CYP11A1, HSD3B1, and CYP17A1, in theca cells. These genes are essential for the production of sex steroids and overall ovarian function.
Why It Matters
The implications of this study are significant for the poultry industry. Subfertility in broiler breeder hens leads to lower egg production and hatchability, directly affecting commercial efficiency. Introducing metformin into feed regimens could offer a simple, non-invasive way to enhance reproductive performance without compromising animal welfare.
Moreover, the study adds to the growing evidence of physiological similarities in reproductive disorders across species. The hen model provides a unique platform for studying PCOS-like conditions, and metformin’s success in this context opens avenues for both agricultural and biomedical research.
Looking Ahead
Further studies are needed to optimize dosing, assess long-term safety, and understand the underlying molecular mechanisms in more detail. Nonetheless, this research highlights the potential of repurposing well-known human medications to solve complex problems in animal agriculture.
By leveraging cross-species insights, metformin may become a valuable tool not just in managing chronic conditions in humans but also in improving the health and productivity of important food-producing animals.
Source: National Library of Medicine
