The Effects Of Simultaneous Thermal And Nutrient Challenge On Broiler Muscle Growth Meat Quality And Underlying Cellular Mechanisms PDF Download

In recent years, a variety of muscle myopathies, specifically wooden breast, white striping, and deep pectoralis myopathy, have severely impacted the poultry industry. Although broilers have become more efficient at producing muscle mass, the rapid increase in growth has exceeded the structural limits of the muscle. As a result, myopathies such as wooden breast are commonly associated with fast-growing, heavy weight broilers. However, there is little genetic correlation with breast muscle yield, indicating that environmental factors likely play a vital role. Environmental factors such as nutrient restriction and thermal stress can alter satellite cell populations, which are a type of stem cell responsible for all post-hatch muscle growth. Changes in the satellite cells will have long-lasting impacts on muscle development and meat quality. Although there have been studies that have elucidated the independent effects of nutrient restriction and thermal stress, there is little information regarding the effect of a simultaneous temperature and nutritional restriction on satellite cells, specifically, immediately after hatch, when satellite cells are the most susceptible to environmental stressors. Since chicks are rarely exposed to a single stressor, it is important to understand how simultaneous environmental factors will impact long-term muscle growth. The effect of a simultaneous post-hatch feed restriction and thermal stress on skeletal muscle growth and meat quality was studied by applying a 20% feed restriction during the first week post-hatch. At the time of hatch broiler chicks were divided into either a 20% feed restriction group, or given ad libitum access to feed and held at an ambient temperature of 31°C, 35°C, or 39°C. Gene expression for satellite cell genes Paired Box Protein 7 (PAX7), Myogenic Factor 5 (MYF5), Myogenic Differentiation 1 (MYOD1), and Myogenin (MYOG), were measured at d 7, and no significant differences were detected (P > 0.25). Muscle fiber diameter, number, and histological scoring were also evaluated and there were no statistical differences observed (P > 0.20). There was also no statistical difference across treatments in meat quality characteristics or meat yield at d 42 (P > 0.05). Feed efficiency and body weight were also recorded from d 0 to d 42 of the trial. Although there was no difference in feed efficiency by the end of the trial, there were significant differences in broiler body weight from d 2 – d 28. Between d 0 – d 7 broilers held at any of the three ambient temperatures had significantly different body weights, with those held at a control temperature of 35°C having the heaviest weights, regardless of nutrient restriction. Birds given a 20% feed restriction had significantly lighter body weights between d 2 – d 28 compared to birds provided ad libitum access to feed regardless of environmental temperature. On d 2, d 3 and d 4, there was a significant interaction between both nutrient restriction and ambient temperature (P