A groundbreaking study by Dr. Takaoki Saneyasu of Kobe University provides valuable insights into the role of peptides, such as spexins, adipokines, and intracellular signaling mechanisms, influencing food intake in chicks. These findings hold promising potential for improving and enhancing poultry farming practices in both broiler and layer chickens.
The poultry industry plays a vital role in the global food supply and is a cornerstone in the agricultural sector. With poultry meat and eggs being the most efficient and widely consumed animal proteins, advancing research to increase poultry productivity is crucial. The productivity of meat and eggs in chickens is widely dependent on food intake, and it is therefore imperative to investigate how feeding mechanisms are regulated within chicks.
To explore this further, Dr. Takaoki Saneyasu, an Associate Professor at the Graduate School of Agricultural Science, Kobe University, conducted a comprehensive review of recent research on the physiological mechanisms governing food intake in poultry. This study was made available online on April 26, 2024, and published in Volume 61 of the Journal of Poultry Sciences.
“Broiler chickens are genetically selected for rapid growth and meat yield, yet their overconsumption of food leads to fat accumulation, which often results in poultry waste,” says Dr. Saneyasu. “Understanding the mechanisms of food intake is, therefore, crucial for improving feed efficiency and reducing waste.” The regulation of food intake in living beings is a complex process. Although there is a lot of research on the food intake regulations in humans, the mechanisms in chickens differ from those of mammals like humans in some factors.
“Many factors, such as hormones, nutrients, and neurological signaling, control food intake in living beings. Some of these factors differ between humans and poultry,” adds Dr. Saneyasu. He reviewed various factors, including neuropeptides, such as adipokines, neurosecretory proteins GL and GM, and cellular signaling, to determine how each of these factors impacts the food consumption in chicks.
Neuropeptides are protein-like molecules that are involved in neuronal communication. These function as signaling molecules and are important in regulating various physiological activities. One such category of neuropeptides studied for its role in regulating feeding mechanisms is spexin (SPX). There are two types of SPX: SPX1, found in humans, and SPX2, found in chickens. SPX is related to galanin, a neurotransmitter that impacts food intake via hypothalamic pathways and appetite regulation. SPX 1 and 2 act on the galanin receptor (GALR) and reduce food intake in chicks. They activate GALR2-like receptor (GALR2L) and GALR3. Additionally, they change the gene expression of neuropeptides that control hunger, such as agouti-related peptide (AgRP) and cocaine- and amphetamine-regulated transcript (CART). This suggests that SPXs control eating behavior via GAR2L and GALA3 in chicks.
Another important group of molecules that regulate food intake is adipokines. These are bioactive polypeptides secreted by adipose tissue and are crucial for regulating appetite, metabolism, and inflammation. Leptin and adiponectin are two major adipokines in mammals, but their roles in appetite regulation are different between mammals and chickens. Contrary to mammals, leptin has a minimal role in chickens. Plasma adiponectin levels are decreased by refeeding in mammals, whereas they are higher in refed chicks compared to fasted ones. Additionally, adiponectin enhances food intake in chicks, but the effects of adiponectin on food intake are conflicting in mammals.
In addition to adiponectin and leptin, there were some other under-researched adipokines, like chemerin and apelin, which were identified to reduce food intake in chicks. Dr. Saneyasu explains: “Understanding the variations in the regulation of feeding via adipokines can lead to species-specific strategies for optimizing poultry diets.”
Additionally, Dr. Saneyasu also discussed the role of neurosecretory proteins, including neurosecretory proteins GL and neurosecretory proteins GM, in food intake mechanisms. Besides these signaling molecules, the study also emphasizes the mechanism of cellular signaling. “In mammals, cellular signaling pathways in the hypothalamus like AMPK, JAK/STAT, and Akt greatly contribute to the regulation of food intake, suggesting the possibility of their role in food intake in chickens as well,” remarks Dr. Saneyasu.
Discussing the methods involved in most of the studies, Dr. Saneyasu explains: “Most of the studies explored the central feeding regulation in chicks through intracerebrovascular injections, which is a simple and reliable method.”
Dr. Saneyasu concludes by sharing his opinions regarding future research: “I believe that there should be more research on the peripheral adipokines and gut hormone production in neonatal chicks to support the findings. Furthermore, species-specific research could also lead to new strategies for enhancing production and promoting sustainable poultry farming worldwide.”
Reference
Title of original paper: Recent Research on Mechanisms of Feeding Regulation in Chicks
Journal: Journal of Poultry Science
DOI: 10.2141/jpsa.2024012
