Research sheds light on how nutritional interventions can modulate gene expression of a key pathway in the poultry gut to increase the bird’s capacity to cope with stressors.
Stress-related decreases in productive and reproductive performance of poultry cause substantial economic losses. In poultry the gut is highly responsive to stressors from the feed and the environment. Under commercial conditions, birds are exposed to a variety of nutritional and environmental stressors. This will lead to stress reactions such as oxidative stress, inflammatory responses and reduced gut integrity on the cellular and gut level, which will increase maintenance energy requirements.
On top of that stressors may negatively affect feed intake, such that altogether performance and efficiency in birds can drop significantly. In laying hens oxidative stress can also accelerate the aging process of the ovaries and impair liver function, which can affect laying persistence and egg quality at the later stages of the laying cycle.
Methods developed to improve the measurement of the underlying mechanisms via molecular markers can lead to a better understanding of how the reactions can be manipulated to reduce the impact on bird performance.
Improving the adaptive ability of birds
By improving the adaptive ability of animals to stressors it is possible to substantially decrease negative consequences of various stresses in poultry production. Researchers consider changes in gene expression to be of great importance for adaptation to stressors, and hence key to the development of techniques for managing stress reactions in the animal. Certain molecular pathways responsible for the transcription of genes for enzymes involved in the protection from the effects of stressors on the cellular level play a vital role in the adaptive ability of birds. A better understanding of these pathways and the development of ways to track and measure changes in their key indicators is paving the way to support them by nutritional means for greater resilience in birds. Certain bioactive components derived from plants are promising candidates for nutritional solutions, because they also play key roles in similar pathways in plants to enhance the plant’s ability to cope with stressors threatening its survival.
Underlying mechanisms to adaptive capacity
Oxidative stress is one of the most common stress reactions on the cellular level in the animal. It is characterized by excess production of free radicals (ROS), which exceeds the ability of the bird’s antioxidant defence system to neutralise them.
In recent years great attention has been paid to the transcription factor Nrf2 and scientific data indicate that Nrf2 activation is one of the most important mechanism to prevent/decrease stress-related detrimental changes. Nrf2 is a transcription factor that responds to oxidative stress by binding to the antioxidant response element (ARE), which initiates the transcription of antioxidant enzymes.
These enzymes contribute to the improvement of the bird’s antioxidant defence system and reduce oxidative stress on the cellular level. They are also known to block Nf-kB resulting in protection against inflammation. However, when stress is too high, leading to a free radical concentration higher than the threshold for cells, other transcription factors including NF-kB become predominant, which increases inflammation. Research suggests, that the threshold could be increased by nutritional means making the pathway more robust under stress and reducing oxidative stress and inflammatory responses.
Recent evaluation of nutritional intervention
Research in broilers carried out by the Agricultural University of Athens, evaluated a gut agility activator as a new nutritional intervention to improve the adaptive capacity of birds for greater resilience to stressors. It contains a combination of bioactive substances derived from herbs and spices designed to reduce the negative impact of stressors on bird performance.
In this trial analyzing tissue samples from different segments of the bird’s gut was done to study the relative expression of genes related to antioxidative enzymes and inflammation. It was discovered that adding the gut agility activator to the diet up-regulated gene expression of antioxidative enzymes belonging to the NrF2/ARE pathway and down-regulated NF-kB1 expression. Additional analysis carried out in the same study demonstrated that this coincided with increased levels of total antioxidant capacity in the gut. However, the positive effect of the gut agility activator was dependent on the inclusion level and segment of the gut.
New and powerful analytical methods are catalysing the progress in our understanding of the mechanics of action of certain feed additives. The current research findings suggest, that it is possible to boost the bird’s capacity to adapt efficiently to stressors, by adding a gut agility activator to the feed. In combination with performance data from commercial trials in the presence of stressors (such as heat, high production level and mycotoxins), there is evidence that the gut agility activator offers a solution to help reduce the impact of stressors on performance under commercial conditions.
Producers looking for a more consistent performance in response to their feeding programs or to sustain longer production cycles e.g. in the laying hen by natural means could benefit economically from this. However, this research alongside previous research also demonstrates the importance of testing and optimizing inclusion levels of active substances derived from herbs and spices, for them to be part of commercially viable solutions in cost-effective diets.
by Gwendolyn Jones, published in Poultry World, 2019