Interview: How nutritional strategies could mitigate woody breast syndrome

Woody breast remains a condition about which we have more questions than answers. The syndrome affects an uncounted number of birds per year and results in meat which is unpleasantly chewy, stiff, and rubbery. It has increasingly come to preoccupy actors at various levels of the poultry production process, from breeders to processors, as the industry seeks causes and solutions.

While the reasons behind woody symptom are imperfectly understood and are believed to be tied to the accelerated growth rate of modern broilers, researchers are in many cases examining nutritional strategies which can mitigate the effects of the condition, in the hopes of finding a solution to reconcile the competing needs for high quality and fast growth. To learn more about these solutions, we spoke to Dr. Tara York, AB Vista’s Technical Manager for the US & Canada, and Dr. Casey Owens of the University of Arkansas’s Center of Excellence for Poultry Science, who elaborated on studies they have conducted on this subject and weighed in on the prospect of managing this syndrome through nutritional strategies. 

You have conducted research on nutritional strategies to mitigate woody breast syndrome in broiler chickens. Can you give a bit of background about these studies?  

[Dr. York] Some of the initial publications on woody breast pointed us towards looking at ways to combat the problem from an oxidative stress angle, as they suggested a lack of blood supply and nutrients was leading to tissue damage at the cellular level.

Because woody breast is having a big impact on the US broiler industry, AB Vista wanted to look at this from a different angle. When feeding higher levels of phytase (for example 2500 FTU/kg of Quantum Blue) in catfish, we found higher levels of iron (Fe) in the blood and liver, resulting in higher hematocrit, red blood cell counts and hemoglobin levels. We also found elevated levels of other key minerals such as zinc and copper in the liver, which supports antioxidant enzymes.

From our work in broilers, we also knew that when feeding higher levels of phytase we increase the production of inositol from the breakdown of phytate, which is reported to play an antioxidant role in humans. Therefore, we combined the idea of feeding higher levels of Quantum Blue in broilers (1500 FTU/kg), along with the use of other ingredients which support the antioxidant capacity of the animal, as a means of trying to assist the bird in reducing the severity and incidence of woody breast.

This research was recently presented at the International Phytate Summit and published in the summit's proceedings, “Phytate Destruction: consequences for precision animal nutrition”.

Some have suggested that the syndrome may be related to oxidative stress due to genetic selection and fast growth rate of the breast muscle. Have there been any new studies to support this line of thinking? Is treating it a question of simply increasing the feeding of antioxidants?

[Dr. York] Essentially yes, oxidative stress due to fast growth rates has been reported as the underlying cause. Recently, however, researchers at the University of Delaware have confirmed that localized hypoxia is occurring in the tissues, which may be due to the lack of antioxidants.

I do not believe anyone has found a simple fix for woody breast, unfortunately. Yet, it would appear that supporting the antioxidant capacity of the animal using a nutritional approach is helping to reduce the severity. This makes sense if woody breast syndrome is occurring due to a lack of antioxidants, as suggested recently by the work at the University of Delaware. 

According to your experiments, the feeding of certain supplements can “minimize” the condition. Can you quantify the results you have seen in experiments? How is the severity of woody breast measured?

[Dr. York] We have been working closely with Dr Owens at the University of Arkansas. She and her colleagues have created a scoring system, which range from 0 to 3 based on tactile evaluation, which we use to score the various forms of woody breast. According to this work, meat quality decreases significantly in breast meat with a score of 2 or 3, showing increased hardness, decreased fillet flexibility, reduced water holding capacity and changes in texture.

Therefore, in our work, our goal has been to determine if we can reduce the most severe form when feeding higher levels of phytase along with other feed additives which support the antioxidant capacity of the animal, such as Zn and ethoxyquin.   

 We have run three studies looking at the combination of these components, and in all three we have been able to reduce the most severe form by almost 50% without slowing down the growth rate of the animal, which is very interesting in itself. Previously all suggestions to help reduce the severity of woody breast revolve around slowing down growth rate. In these studies, the combination of products, such as Zn and ethoxyquin, in conjunction with higher phytase levels, led to the highest average daily gains yet the least severe woody breast scores.

What is more interesting is that in one of the studies, we dosed higher levels of Fe in combination with higher phytase (Superdosing at 1500 FTU/kg) and the results showed a decrease in the most severe forms of woody breast. This suggests Fe plays a key role and warrants further investigation.

Feeding superdosing levels of an enhanced E. coli phytase in combination with nutrients involved in supporting the antioxidant pathway of the animal appears to allow for maximum average daily gain while aiding in the reduction of the more severe forms of woody breast. 

How sophisticated is our ability to detect woody breast syndrome in living birds? Will any eventual intervention be targeted at affected birds, or will it be applied across whole flocks?

[Dr. Owens] Woody breast can be detected in live birds by palpation, and the correlation is high between scoring live birds and the processed breast fillets. Other novel detection methods may also be under investigation for more objective means of identifying the condition in the live bird, but are not widely available to date. 

Regardless of the method of detection, identifying woody breast in the live birds can be a useful tool in research (i.e., genetics, nutrition, management strategies). However, it is likely to be labor intensive and thus would not be practical for use in the field. Therefore, if interventions involved nutrition or management of the birds, it would need to be applied across the whole flock. It would be impractical to sort birds on the farm and apply an intervention to only those affected. With this said, woody breast incidence can be high in some flocks (e.g., high breast yielding and faster growing broilers), although with varying levels of severity, so application of an intervention to the whole flock could serve to increase the percentage of normal fillets overall by reducing severity across the board. 

It is argued that the syndrome is connected to genetics and to the stresses put on birds by rapid growth rates. Do you believe that improved nutrition alone will be able to address woody breast syndrome?

[Dr. Owens] In my opinion, improving the nutrition of the bird is one strategy for addressing the woody breast syndrome. While improvements in the woody breast condition may be observed with some nutritional strategies, this is not the overall answer to the problem. However, it is important because these nutritional programs can help manage the issue until the underlying problems can be resolved. There is also a balance between production goals (size of broilers, feed conversion, etc.) and meat quality that needs to be found. 

What do you see as the key questions to be addressed by further research into the causes of and potential nutritional solutions for woody breast syndrome?

[Dr. York] Investigative research is occurring around the globe; from what causes woody breast to how to reduce it. Geneticists are also working diligently to hopefully reduce the traits that may be causing it. For AB Vista, we are working with various groups to find ways to help alleviate the issue through innovative nutritional concepts.

[Dr. Owens] University researchers will continue to investigate the potential triggers of the development of this condition, along with evaluation of production practices that will help reduce the severity of woody breast. Ongoing research also includes evaluation of genes associated with the condition, developing biomarkers to predict the condition when animals are young. Other work includes developing remediation strategies for use of woody breast meat in processed products.