By managing the flock for first grade broiler meat, the producer commits to meeting and exceeding animal welfare standards. This commitment is rewarded as the economics and return on investment is maximised. Anything less than first grade cannot be sold for premium prices or will be devalued which will mean an additional cost to the operation. From research at Cobb, as well as field experience, we have seen factors impacting first-grade meat output and what meat quality issues have the largest effect. Broiler nutrition, farm management, processing plant management and diseases are proven contributing factors to meat quality.
Nutrition
A balanced broiler diet with nutrient levels meeting the developmental requirements of each stage is essential for optimal development and growth. If growth is higher than recommended for the developmental stage, myopathies may occur with a negative outcome on the percentage of first grade quality meat. It is important to follow Cobb specifications for broiler dietary requirements that are being reared.
The starter diet must aim for a high early intake, so its physical form is important. In addition, digestible lysine and corresponding ratios of the other amino acids should be at the recommended levels to maximize satellite cell proliferation immediately after placement. A high early feed intake will stimulate yolk absorption so the energy from the feed will be available for early development. A delay in growth during the first 2 weeks post-hatch creates a risk factor for the development of wooden breast.
The grower diet should be aiming for a controlled growth. The growth rate should not be overstimulated and must remain in line with the breed standards. The rearing goal is to have a balance between muscle growth, organ development and oxygen supply. In some cases, feeding a lower amount of digestible lysine (e.g., 85 % of the recommendations) will reduce the risk for meat myopathies in flocks that are aiming for higher final weight.
Oxidative stress is a facilitator for myopathy development and the inclusion of antioxidants in the feed (Vitamin E and C and selenium) can reduce this risk. Current research indicates increasing phytase in broiler feed has a positive effect as related to wooden breast.
Management
On the broiler farm, as in the processing plant, good management practices will positively impact the first-grade meat percentage. Brooding, farm equipment, ventilation and temperature settings, stocking density, lighting program, feed withdrawal programs, catching procedures, cleaning and disinfection all need to create an optimal environment for broiler growth and development. At the processing plant, machine settings and operation evaluations should aim to produce first grade broiler meat from first grade broiler flocks. This will be discussed in more detail in the other articles featured in this issue.
Diseases
Almost all diseases have an impact on meat quality and organ function. As organs are affected, they do not perform as they should and limit growth and impact uniformity.
Marek’s disease is the most common infection impacting meat and organ quality directly with tumor formation inside organs, skin and muscles leading to rejects at the processing plant. The expression is age dependent. Slow growing broilers generally present more Marek’s related issues because they are older when processed.
Some diseases affect the inside layer of blood vessels which can create bleeding in organs, muscles and subcutaneous. The most prevalent diseases are highly pathogenic avian influenza, Newcastle disease and infectious bursal disease (Gumboro). At processing, Gumboro disease is probably the most visible with small bleeding into the breast and thigh muscles. Some diseases affect specific organs such as inclusion body hepatitis (Adeno). The livers of birds with Adeno appear mottled.
E.coli, Staphylococci, and Streptococci may be introduced on or under the skin if scratching or injury creates an open wound. These infections can also be visible on the surface or within organs, joints and in the digestive tract.
Almost every disease disturbs homeostasis of the bird. This can lead to a dehydration which is visible in the firmness and color of the meat (Dark, Firm and Dry (DFD)).
Some potential causes of DFD include:
- Acute heat stress PSE meat, muscle glycogenolysis leading to a lactic acid accumulation during rigor.
- Chronic heat stress and reduced muscle glycogen leading to DFD meat.
- Metabolic disorders such as lameness with difficulties drinking from a nipple.
Conclusion
When the live production chain delivers high quality broilers to the processing plant, the plant then must generate high quality broiler meat. Several factors can have an impact on the amount of rejected meat due to quality issues. Broiler farm management, nutrition and diseases are all a part of muscle quality. Understanding and managing the impact of each management factor on meat quality will maximize high quality meat output.