Approaches for Mitigating Woody Breast in Commercial Broilers through Nutritional and Management Strategies

Breast myopathies have caused significant economic losses to the poultry industry over the last decade. The induction of woody breast (WB), white striping (WS), and spaghetti meat (SM) have caused textural issues, functional issues, and a decline in consumer acceptance. Of these three myopathies, WB causes the most pronounced effects on product quality and reduces functional use. Woody breast is also commonly associated with expansive breast meat growth/high performing broilers. However, progress in reducing these myopathies has been limited without hindering other aspects of poultry rearing. Generally, production performance reduces as myopathy occurrence or incidence reduces. This response is primarily driven by a reduction in final body weight rather than in a net myopathy reduction. For this reason, novel strategies for reducing myopathies are still being investigated. Therefore, this dissertation aimed to assess new technologies in these sectors to reduce or prevent the occurrence of breast myopathies in commercial broilers. Chapter 2 assessed the supplementation of guanidinoacetic acid (GAA) in poultry diets for reducing the occurrence of WB in commercial broilers. Supplementation of GAA was achieved through on-top additions of 0.06% and 0.12% of the diet. Results suggest that GAA can be used as a dietary source of breast myopathy reduction without suppressing body weight or broiler growth. The use of GAA in the diet also improved FCR in broilers at both supplied levels compared to the control diet. Data indicate that supplementation levels may be beneficial above those utilized in this experiment and optimizing levels should be investigated. Chapter 3 also assessed the use of GAA, but in formulation as a potential energy sparing ingredient while maintaining a reduction in breast myopathies. Supplementation was formulated as a 55 kcal/kg and a 110 kcal/kg reduction in energy. Results suggest that a 110 kcal/kg reduction of energy produced no differences in final body weight or body weight gain over the 49 day rearing period. Broilers also expressed no differences in carcass or part yields with or without the presence of GAA. In addition, meat quality differences were not present among treatments. However, GAA inclusion provided an improvement in feed conversion ratio and had a numeric shift in WB occurrence in broilers. The need to assess ingredient pricing and availability should be considered for GAA use as an energy sparing ingredient. Chapter 4 evaluated the use of a novel 0.9% in ovo feeding of nicotinamide riboside (NR), a vitamin B3 analog, to reduce the occurrence of WB in broilers. Three concentrations of NR were utilized in this experiment including: 250 mmol, 500 mmol, and 1000 mmol of the vitamin B3 analog. Results suggest that NR had little effect on performance or meat quality parameters yet improved final bird weight compared to the control. Optimizing the dosing level for WB reduction may not have been met in this study and should be further investigated for conformation. Changing to other forms of WB reduction, Chapter 5 evaluated the use of broiler stocking density as a combative measure. Three research accepted stocking densities were assessed to determine effects on meat quality. Results indicate that WB is reduced when stocking density is increased, but performance characteristics are reduced alongside a reduction in final body weight. Results also suggest that investigation into welfare limits and financial gain may be necessary to determine the most beneficial stocking density. Finally, Chapter 6 was conducted to understand statistical sampling needs to assess myopathies (specifically WB) for common broiler rearing experiments. There is a growing trend to include meat quality analysis in studies designed for nutritional, management, or physiological aspects. These types of studies typically use a low sample selection size per pen which have typically been adequate for analysis, such as yield. In opposition, myopathy occurrence in populations can vary and may require a larger sample size. Some studies conducted on performance characteristics have started assessing meat quality traits with limited samples and drawing conclusions that do not seem to match common practice. Meat quality based studies typically utilize a substantially larger sample size than those of performance-based experiments as variability is generally higher. Results indicated that sampling a larger proportion of the pen (up to 75%) would greatly reduce the variance present between samples and lead to a more accurate description of myopathies among treatments. Overall, this dissertation provided three new avenues for assessing WB in commercial broilers and potential ways to reduce occurrences. Limited results were present in WB reduction, but results indicate that differences in body weight were not as apparent as seen in previous studies. Suppressed growth comes at a significant price to the industry so finding nutritional or managerial strategies to reduce myopathies is very important. The need to better understand the relationship between each of the assessed strategies and WB are still necessary to improve breast product quality