Several factors affect the development of broodiness in poultry, including its genetic makeup. For example, genes associated with breast milk production and the production of the first egg are less common in certain breeds. Furthermore, these changes are not necessarily reflected in egg production, as there may be an interspecific variation in the expression of these genes. Here is a summary of the main findings from this research. The data obtained are preliminary.
There are three major groups of genes that regulate broodiness in poultry. The first group of genes is located on the Z chromosome, which is one of the largest chromosomes in humans. The second set of genes are called a dominant autosomal gene (DAG) and is characterized by a unique sequence. These two groups of genes are invariable, but they influence broodiness equally.
Among the genes upregulated in the hypothalamus of ducks, the transthyretin and type 2 deiodinase gene pairs were prominently downregulated. These two proteins provide a rhythmic gating mechanism for the thyroid hormone. Moreover, transcription factors c-FOS and c-Jun were identified to be significantly regulated in broodiness. In addition, there were 34 DEGs that were shared between all three reproductive stages of poultry.
While the endocrine-endocrine system of chickens coordinates behavior in different stages of reproduction, the transition from egg-laying to broodiness is an intricate process. The termination of ovulation decreases egg production. These hormones are altered in many domestic species, including poultry. The effects of these hormonal changes are believed to be responsible for the emergence of broodiness.
Some breeds of chickens are known for broody behavior. Silkies and Cochins are famous for their excellent mothering of newly hatched chicks. Besides, some breeding flocks have a genetic predisposition to broodiness. But even in these breeds, genetically modified eggs are able to be produced. However, the production of broody eggs depends on the availability of fresh and healthy feed.
Molecular genetics has identified three hundred and forty-seven genes associated with broodiness. The results of these studies revealed that the pituitary gland is involved in the regulation of the hormones, whereas the hypothalamus regulates reproductive behavior and gonads are responsible for egg-laying and incubation. These findings suggest that these genes may be related to the hypothalamus.
The genes responsible for broodiness in poultry are important for the reproduction of young chicks. It is also a significant factor in commercial breeding. In many flocks, these genes are correlated to the reproductive stage. The timing of the reproductive activity in a particular species is important for a successful breeding program. When it is too late, the timing of the onset of broodiness can be disrupted.
Previous studies have shown that RLN3 is downregulated in brooding Muscovy ducks, and Xu Shen and colleagues found that this gene also inhibits AP-1. These findings point to the role of the hormone Relaxin in egg-laying, as it has multiple reproductive roles in many species. The concentration of the hormone relaxin in the maternal blood has also been positively correlated with the duration of gestation.
A study of the expression of genes in poultry has shown that there is a strong association between dopamine D1 receptors and the prolactin gene. Dopamine D1 receptors are involved in regulating the reproductive behaviors in chickens. Although the findings of this research are preliminary, they are significant. The findings suggest that there are other genes involved in the regulation of broodiness. The findings will help farmers improve their breeding practices by improving egg production.
Other studies have demonstrated that hormones are important in the regulation of broodiness in poultry. This study has revealed that recombinant-derived prolactin inhibits egg laying and reduces broodiness in Muscovy ducks. The data in this study show that this protein has no impact on the development of the phenotype. This finding indicates that the hormone is necessary for the proper functioning of the reproductive system of Muscovy ducks.