2022-23 Rapid Ag: Prolonging Fertility in Turkey Breeders as a Sustainable Model for Poultry Production: The Role of the Immune System
Kahina Ghanem, Department of Animal Science
- Kent Reed, Department of Veterinary and Biomedical Sciences
- Sally Noll, Department of Animal Science
As the world’s population is estimated to reach 12.5 billion by 21001, and availability of natural resources for agriculture is shrinking, there is an urgent need to increase sustainable food production. Poultry meat is among the most affordable sources of high-quality animal protein. As a result, the demand has been increasing by 2.2 % each year, worldwide2. To meet the demand, the poultry industry has to increase production, while preserving resources, and remaining profitable. One model for increasing production in a sustainable fashion is to decrease the high turnover of breeder flocks by improving and extending their fertility. Minnesota is the #1 turkey producer in the U.S., and is home to the largest poultry hatchery in the world. As such, it is important for the University of Minnesota and the Minnesota turkey industry to collaborate and lead the efforts in solving late lay fertility problems in turkey breeders. Here, the objectives are to determine the mechanisms leading to the decline in fertility of aging turkey breeders, and if reducing inflammation will reduce this decline. We hypothesize that improved fertility will result in more turkeys hatched per hen at a lower cost allowing for fewer hens while conserving local resources.
Objectives and Goals
- Determine the age related changes in steroid receptor expression in turkey hens
- Determine the age-related changes in gene expression of the vagina and the uterovaginal junction of turkey hens
- Determine if reducing inflammation leads to increase sperm retention
The turkey industry relies on parent breeders to lay fertile eggs that will be hatched and raised for meat. In 2018 alone, 466 million meat turkeys were produced globally. This requires a large number of hens as each hen only produces up to 60 poults. Further, turkey hens do not start laying until they reach 32 to 35 weeks of age. By this age, a flock of 1000 hens would have consumed approximately 8,275 gallons of water, 121,600 pounds of feed, and required up to 6,018 Kwh of electricity3. After only 10 to 14 weeks of lay (WOL), the fertility of the breeders declines by up to 1% each week. By week 26-28 WOL, the flock is turned over. Determining ways to improve turkey fertility and extend laying time, offers an opportunity to increase production while conserving resources, and reducing the number of breeders needed to produce the same number of progeny. Even a 1% increase in fertility will lead to 1000 more poults per 1000 breeder flock.
Avian species have the capacity to store sperm for several weeks in small structures in their reproductive tract called sperm storage tubules (SSTs). Artificial insemination is used to achieve egg fertility. After each insemination, turkeys can lay fertile eggs for as long as 15 weeks4. However, studies have shown that as they age, their ability to store sperm declines, leading to lower fertility5. Increasing the frequency of insemination and number of sperm inseminated, produce minimal improvements in fertility678. The role of the immune system in the selection of sperm upon insemination has been extensively studies. Classes of immunocompetent cells including macrophages, antigen-presenting cells expressing MHC class II, CD4+ and CD8+ T cells, premature B cells, and plasma cells as well as marker associated with acquired and innate immunity have all been detected in the mucosa of the oviduct, particularly the vagina9. Studies have reported that this decline is associated with significant increases in the number antigen-presenting cells expressing MHC class I and II , and CD4+ and CD8+ T cells in the stroma of UVJ in low-fertility hens, junction10611. The presence of these lymphocyte may mount an attack on sperm and reduce its chances of survival in the reproductive tract. Steroids hormones such as estrogen, progesterone, and testosterone are known to modulate the immune system, by working either sequentially or synergistically on various tissues and immune cells121314. In aging chickens, there is evidence of a negative correlation between steroid plasma concentrations and receptor expression with egg production and activity of the ovary151614. Unlike chickens, virtually nothing is known about the changes in expression of steroid receptors in the turkey hen. Additionally, a definite causative relationship between the inflammation that occurs during impaired steroid signaling and infertility has not been established in any avian species, nor is there any established mechanism. In this study we aim to determine the age-related changes in steroid receptor expression in turkey hens and if increasing plasma steroids, or reducing inflammation will lead to increased sperm retention and fertility. We hypothesize as turkey hens age, there is an increase inflammatory response to the presence of sperm due to an age related decrease to steroid sensitivity.
Although, there is strong evidence that changes in the immune profile of the reproductive tract may be responsible for the decline in fertility in hens, the molecular changes that allow for this and/ or that are affected by these changes are not known. Further, there may be other factors that play a role in decreased fertility in hens that compound with inflammation. It is important to look at changes in gene expression as a first step to investigate these factors. Although, some studies have examined changes in global gene expression in response to insemination in laying hens, confirming that insemination induces changes in immune and pH regulatory genes171819, studies of changes in gene expression in the reproductive tract of breeders hens are lacking. Conducting a transcriptomic study will help us gain insight in changes that occur in gene expression as the breeder hens age and the gene pathways affected as fertility declines. Furthermore, a more comprehensive approach to look at global changes in gene and protein expression would potentially uncover more factors that contribute to the decline in. In this study we aim to determine the age-related changes in the gene expression of the vagina and the uterovaginal junction of turkey hens. We hypothesize that there are age-related changes in genes expression that drive the decline of fertility in turkey breeders.
Findings and data collected from the proposed studies will serve as preliminary data for a USDA-AFRI grant in the Animal Reproduction area of the Foundational and Applied Science Program. Experiments will be conducted by a research scientist and undergraduate students in my laboratory. K.
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