Antioxidant Defense in Granulosa Cells: The Secret to Sustained High Production in Laying Hens?

The reproductive performance of laying hens is closely linked to the healthy development of ovarian follicles. During the rearing period, primordial follicles begin to develop; as the oocyte grows, the surrounding cells become cuboidal and, because their cytoplasm contains granules, they are called granulosa cells. The cumulus granulosa cells surround the oocyte and form gap junctions through the extracellular matrix between them, “communicating” with the oocyte to deliver nutrients that promote its growth, maturation, and ovulation. In the early stages of follicular development, granulosa cells secrete various growth factors and hormones to stimulate the proliferation and differentiation of follicular cells; in the mid-to-late stages, they assume a greater role in regulating the follicular microenvironment and maintaining follicular stability (Figure 1).

Oxidative stress in granulosa cells triggers apoptosis, ferroptosis, and other forms of programmed cell death, directly affecting laying hens’ egg production rate and egg quality. Consequently, research on high‑producing layers cannot overlook the role of granulosa cells. When these cells are damaged by oxidative stress or other adverse factors, their normal functions are impaired, leading to abnormal follicular development, reduced oocyte quality, and ultimately diminished reproductive performance. Therefore, granulosa cells represent a key target for improving reproductive performance in laying hens, and elucidating their underlying mechanisms can guide strategies to enhance egg production and prolong peak laying periods. But how do nutritional factors regulate granulosa cells to mitigate the impact of various rearing‑environmental challenges that negatively affect egg production?

On February 11, 2025, at nuacid Company’s New Year celebration and charging conference, Chief Scientist Hu Youjun publicly presented research findings on “the core mechanism by which flavonoids (Lewis acids) with antioxidant activity regulate high-yielding laying hens,” offering an effective approach to sustaining peak production and optimizing egg quality in high-producing layers.

Figure 1. Structure and function of ovarian granulosa cells

NIC (2023, 2024), in collaboration with Guizhou University and the Guangdong Academy of Agricultural Sciences, found that oxidative stress profoundly affects granulosa cells, triggering a surge in ROS levels that damages cell membranes, proteins, and DNA, leading to structural impairment and functional abnormalities. Although granulosa cells activate antioxidant defenses, intense or prolonged stress can overwhelm these defenses, resulting in severe disruption of physiological functions and even apoptosis. Such aberrant apoptosis impedes follicular development, reduces oocyte quality and quantity, and poses a threat to reproductive capacity. These findings are consistent with Wang Weiwei’s observations regarding age-related changes in production performance, egg quality, and antioxidant capacity in laying hens across different weeks of age (Figure 2).

Figure 2. Changes in antioxidant capacity of the uterine oviduct in laying hens at different stages

A joint study by nuacid NIC, Guizhou University, and the Guangdong Academy of Agricultural Sciences has found that “qimei su” can enhance the antioxidant capacity of ovarian granulosa cells through multiple pathways.

In vitro cell assays revealed that chimericin significantly reduced intracellular free radicals and reactive oxygen species (ROS) in ovarian granulosa cells. This property markedly mitigated oxidative stress–induced cellular damage and effectively preserved the integrity of granulosa cell mitochondria (Fig. 3, 4). 。 Qimei Su effectively maintains the normal physiological function of ovarian granulosa cells by scavenging free radicals, thereby ensuring the smooth development of follicles and the normal synthesis of hormones. This capability stems from Qimei Su’s efficient preservation of granulosa cell mitochondrial integrity via an as-yet-undefined mechanism. So what is the mechanism of action?

Further research revealed that the mechanism underlying the efficient protection of mitochondria involves bifidin’s regulation of relevant signaling pathways in ovarian granulosa cells—such as the Nrf2–Keap1 pathway and the nuclear transcription factor Nrf2—which modulates the expression levels of antioxidant genes in layer granulosa cells. Nrf2 is a key regulator of antioxidant gene transcription, promoting the expression of antioxidant genes. Qimei su may activate the Nrf2 signaling pathway, thereby upregulating the expression of antioxidant factors. , there is great potential to protect granulosa cells from apoptosis and other forms of damage, thereby maintaining their normal function; our research has confirmed this (Figure 5), but can these results be translated into clinical practice?

Figure 5. Effect of Qimeisu on GCs-related antioxidant genes in laying hens

Finally, NIC (2024), in collaboration with Guizhou University, found that the addition of qimei su significantly activated the antioxidant enzyme system in ovarian granulosa cells within an oxidative stress model, including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px). These antioxidant enzymes catalyze the decomposition of free radicals, thereby reducing intracellular free radical concentrations and further mitigating oxidative stress–induced cellular damage. This indicates that qimei su, via specific signaling pathways, indeed upregulates the expression of the antioxidant enzyme system, thus preserving the full functional integrity of granulosa cells and playing a crucial role in normal follicular development. The underlying mechanism is illustrated in Figure 6.

Figure 6. Signaling pathways by which schizandrin enhances the expression of antioxidant enzyme genes

Experiment 1: In the feed of Jingfen No. 6 laying hens aged 23 to 60 weeks, the addition of Qimei Su increased the egg-laying rate from 91.4% to 93.7%, which was significantly higher than that of the control group and other antioxidant groups. Qimei Su significantly enhanced the T-AOC, SOD, and GSH-Px activities in the serum of laying hens while reducing the MDA content (Figure 7).

Figure 7. Effects of Qimei Su on the laying rate and antioxidant enzymes in Jingfen No. 6 laying hens aged 23–60 weeks.

Experiment 2: Trial at a commercial layer farm in North China housing 45,000 hens: From day 346 to 369 of age, the flock’s egg production rate was 87.36%. At day 370, Qimei Su was added; during days 1–14 post‑addition, the flock’s production rate rose to 88.21%, and from days 15–30 it further increased to 88.33%. Typically, within two months between days 340 and 400, standard egg production rates for JF6 lines decline by 3–4 percentage points. However, the data show that after adding Qimei Su, not only did the expected downward trend fail to materialize, but a robust increase occurred instead (an absolute gain of 1%), once again demonstrating a powerful synergistic effect between in vivo antioxidant activity and basic nutritional support.

Figure 8: The elevating effect of Qimei Su on the declining peak in the mid-to-late laying period of Jingfen No. 6 laying hens

Experiment 3: In the diet of Jingfen No. 6 laying hens at 76 weeks of age, addition of Qimei Su increased the egg production rate from 77.81% to 80.17% and reduced the feed-to-egg ratio. The Qimei Su group significantly enhanced total antioxidant capacity (T-AOC) in hen serum and decreased malondialdehyde (MDA) levels. Furthermore, the Qimei Su group markedly increased the numbers of graded follicles and large white follicles.

Summary

 

Based on the above, greater attention is needed for granulosa cells, as their condition is critical to reproductive efficiency and the development of the poultry industry. In practical production, schizandrin, an effective antioxidant, exhibits significant protective effects against oxidative stress in ovarian granulosa cells of laying hens. It primarily achieves this by activating endogenous antioxidant systems, scavenging excess ROS, and preserving mitochondrial membrane potential, thereby effectively reducing oxidative stress–induced damage to these cells. This antioxidant action not only enhances the stability of ovarian granulosa cells but also helps maintain normal ovarian function, ultimately improving reproductive performance in laying hens. Furthermore, enhanced antioxidant capacity contributes to improved immune function, increasing disease resistance and reducing morbidity risk, which indirectly boosts overall productive performance.

 

Written by: E Xiaodi

Review: Hu Youjun