A myopathy affecting the pectoralis major muscle of the commercial broiler has emerged creating remarkable economic losses as well as a potential welfare problem of the birds. We here describe the macroscopic and histologic lesions of this myopathy within 10 pectoralis major muscles of 5- to 6-week-old broilers in Finland. Following macroscopic evaluation and palpation of the muscles, a tissue sample of each was fixed in formalin, processed for histology, and histologically evaluated. The muscles that were macroscopically hard, outbulging, pale, and often accompanied with white striping histologically exhibited moderate to severe polyphasic myodegeneration with regeneration as well as a variable amount of interstitial connective tissue accumulation or fibrosis. All affected cases also exhibited perivenular lymphocyte accumulation. The etiology of this myodegenerative lesion remains yet open. Polyphasic myodegeneration is associated with several previously known etiologies, but palpatory hardness focusing on the pectoralis major, together with perivenular lymphocytes, has not been described in relation to them. The results of this study provide the pathological basis for further studies concerning the etiology of the currently described myopathy.

Sodium intake exceeds the nutritional recommendations in many industrialized countries. Excessive intake of sodium has been linked to hypertension and consequently to increased risk of stroke and premature death from cardiovascular diseases. The main source of sodium in the diet is sodium chloride. It has been established that the consumption of more than 6 g NaCl/day/person is associated with an age-increase in blood pressure. Therefore, it has been recommended that the total amount of dietary salt be maintained at about 5-6 g/day. Genetically salt susceptible individuals and hypertensives would particularly benefit from low-sodium diets, the salt content of which should range between 1 and 3g/day. In industrialized countries, meat products and meat meals at home and in catering comprise one of the major sources of sodium, in the form of sodium chloride .Sodium chloride affects the flavour, texture and shelf life of meat products. The salt intake derived from meat dishes can be lowered by, whenever possible, adding the salt, not during preparation, at the table. In most cases salt contents of over 2% can be markedly lowered without substantial sensory deterioration or technological problems causing economical losses. Salt contents down to 1.4% NaCl in cooked sausages and 1.75% in lean meat products are enough to produce a heat stable gel with acceptable perceived saltiness as well as firmness, water-binding and fat retention. A particular problem with low-salt meat products is, however, that not only the perceived saltiness, but also the intensity of the characteristic flavour decreases. Increased meat protein content in meat products reduces perceived saltiness. The required salt content for acceptable gel strength depends on the formulation of the product. When phosphates are added or the fat content is high, lower salt additions provide a stable gel than in non-phosphate and in low-fat products. Small differences in salt content at the 2% level do not have marked effects on shelf life of the products. By using salt mixtures, usually NaCl/KCl, the intake of sodium (NaCl) can be further reduced.

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Wooden breast (WB) myopathy of broiler chickens is a myodegenerative disease of an unknown etiology and is macroscopically characterized by a hardened consistency of the pectoralis major muscle. Our aim was to describe the development and morphology of WB over the growth period in broilers. Additionally, the effect of restricted dietary selenium on the occurrence of WB was examined by allocating the birds in 2 dietary groups: restricted and conventional level of selenium. The experiment included 240 male broilers that were euthanized at ages of 10, 18, 24, 35, 38, or 42 days and evaluated for WB based on abnormal hardness of the pectoralis major muscle. The severity and the distribution of the lesion and presence of white striping were recorded. The first WB cases were seen at 18 days; 13/47 birds (28%) were affected and the majority exhibited a mild focal lesion. In subsequent age groups the WB prevalence varied between 48% and 73% and the lesion was usually diffuse and markedly firm. White striping often coexisted with WB. Histological evaluation performed on 111 cases revealed a significant association of myodegeneration and lymphocytic vasculitis with WB. Vasculitis and perivascular cell infiltration were restricted to the veins. Restricted dietary selenium did not affect the occurrence of WB ( P = .44). Our results indicate that WB starts focally and spreads to form a diffuse and more severe lesion.

The basic contractile unit of muscle, the sarcomere, will contract as the muscle goes into rigor post-mortem. Depending on the conditions, such as the rate of pH decline, the cooling rate and the mechanical restraints on the muscles, this longitudinal shortening will result in various post-mortem sarcomere lengths as well as lateral differences in the distances between the myosin and actin filaments. This shortening is underlying the phenomena described as rigor contraction, thaw rigor, cold shortening and heat shortening. The shortening in combination with the molecular architecture of the sarcomere as defined by the myosin filaments and their S-1 and S-2 units, the interaction with the actin filaments, and the boundaries formed by the Z-disks will subsequently influence basic meat quality traits including tenderness and water-holding capacity. Biochemical reactions from proteolysis and glycogen metabolism interrelate with the sarcomere length in a complex manner. The sarcomere length is also influencing the eating quality of cooked meat and the water-holding in meat products.