By: Dr. Turki Saraqbi 

Who among us doesn't enjoy pasta (spaghetti, or thin strings) cooked in various ways (with tomato sauce, yogurt, eggs, cheese, etc.)? However, none of us likes to see these strings or tough white lines in broiler chicken meat (especially in the breast), which often leads to the rejection of such chickens for human consumption in slaughterhouses, causing significant moral losses to the poultry industry, farmers, slaughterhouses, and their associated companies.

In fact, global attention has focused on understanding the increasing incidence of muscle disorders (myopathies) in broiler chickens, a topic that has gained prominence in the early 21st century.

The interest has particularly increased in the primary causes of these disorders, as they affect the breast muscle fibers, making them unattractive or undesirable to consumers. They reduce the protein quality and nutritional value of chicken meat products. Notable conditions include:

1. White Striping (white-striped muscle fibers) or Spaghetti Meat
2. Woody Breast
3. Green Deep Pectoral Muscle
4. Soft, Pale, and Exudative Meat

Due to the economic importance of breast muscles (fillets), which make up a quarter of a broiler's live weight, a third of its carcass weight, and half of its total consumable protein, this muscle disorder and commercial defect lead to significant losses for the broiler product.

In some slaughterhouses, the incidence of such defects has been recorded at about 0.7% of breast meat. For a slaughterhouse processing a million broilers, with an average live weight of 3.2 to 3.6 kg, this amounts to a loss of approximately one ton of affected parts and an equal amount of fillet cuts weekly. This results in economic losses of around $7,000 per week, or $350,000 annually.

This article will focus on spaghetti meat, which is currently one of the common muscle disorders found in most broiler breeds. It is characterized by fat deposition in the fast-growing breast muscles of broilers. The increased growth rate and size are driven by multiple biochemical processes that lead to oxygen deficiency (hypoxia) and inflammation, resulting in the formation of foam cells (large macrophages). Fat accumulates as white lines along the muscle tissue, with negative impacts including higher fat content, increased calorie count, reduced protein levels, decreased palatability, and increased drip loss. Additionally, leakage from muscle fibers leads to the loss of water, iron, and proteins, resulting in reduced meat quality. Strategies need to be developed to eliminate this issue.

Research on this syndrome has involved genetic, histological, pathological, and biochemical studies, along with molecular biology insights. Researchers have identified specific cells, genetic markers, and molecular factors that contribute to the development of these white lines, with no cure currently available. The studies have covered:

• How poultry production has changed over the years, leading to the creation of larger birds with faster growth rates.
• The physiology of muscle growth.
• The pathological processes involved in the formation of white striping.
• The causes of white striping.
• How to identify, detect, and measure white striping.
• The effects of white striping on meat quality and production.
• Strategies to mitigate the occurrence of white striping and their implementation results.

It is important to note that dietary strategies should include nutrients and substances that either reduce inflammation or prevent fat accumulation in the breast, or provide antioxidant properties. Additionally, there are studies on slowing down the growth rate of fast-growing broilers, a type that is currently raised in Europe, where slower-growing broilers are slaughtered around 55 days of age, thus increasing administrative costs. Moreover, genetic selection of broiler breeds without muscle disorders or the introduction of breeds with fewer white stripes are potential solutions. Ultimately, a review of the nutrition and genetics of fast-growing broilers is necessary to reduce the mentioned muscle disorders.

Some tested strategies to avoid this syndrome in broilers and its negative effects on growth and meat quality include using certain feed additives, such as increasing digestible arginine (which helps expand blood vessels and provides better oxygen delivery to muscles), adding Vitamin C (which works against oxidative radicals to prevent cellular damage), increasing vitamin premixes, and reducing the density of amino acids in the growing diet (believed to slow down muscle growth, thus allowing more blood flow to the muscles and potentially reducing the occurrence of white stripes). A combination of these strategies has been effective.

Some have suggested reducing lysine levels in the diet to lessen the occurrence of white striping, as lysine regulates protein synthesis and also affects growth. Observations have shown that feeding broilers 85% of the required lysine reduced the occurrence of white striping and minimized tissue damage. Similar results were seen in another study where reducing lysine (between 75% and 85%) during certain growth stages (from 18 to 26 days and from 28 to 40 days) decreased the severity of white striping at 48 and 61 days of age. Adding methionine as a substitute, along with roasted soybean and sunflower meal, has also been shown to reverse the components (PPARG, PTGS2, and CD36) involved in white striping development through gene expression.

Overall, there is no single solution to eliminate the phenomenon of white striping, as there are several factors contributing to its development.

Additionally, Vitamin D plays an essential role in muscle repair processes by supporting satellite cells that form new muscle cells instead of connective tissue. The plant Solanum glaucophyllum may support mitochondrial function and enable them to provide sufficient energy to cells and efficiently overcome oxidative stress generated during cellular energy production.

The key takeaway is that poultry producers must remain vigilant and ensure the production of high-quality chicken meat free from muscle disorders—meat that is tasty, visually appealing, rich in protein, and low in fat.