The Role of Incubation Conditions in the Onset of Avian Myopathies.

White striping, wooden breast, and spaghetti muscle have become common myopathies in broilers worldwide. Several research reports have indicated that the origin of these lesions is metabolic disorders. These failures in normal metabolism can start very early in life, and suboptimal incubation conditions may trigger some of the key alterations on muscle metabolism. Incubation conditions affect the development of muscle and can be associated with the onset of myopathies. A series of experiments conducted with broilers, turkeys, and ducks are discussed to overview primary information showing the main changes in breast muscle histomorphology, metabolism, and physiology caused by suboptimal incubation conditions. These modifications may be associated with current myopathies. Those effects of incubation on myopathy occurrence and severity have also been confirmed at slaughter age. The impact of egg storage, temperature profiles, oxygen concentrations, and time of hatch have been evaluated. The effects have been observed in diverse species, genetic lines, and both genders. Histological and muscle evaluations have detected that myopathies could be induced by extended hypoxia and high temperatures, and those effects depend on the genetic line. Thus, these modifications in muscle metabolic responses may make hatchlings more susceptible to develop myopathies during grow out due to thermal stress, high-density diets, and fast growth rates.

Temporal characterization of wooden breast myopathy ("woody breast") severity and correlation with growth rate and lymphocytic phlebitis in three commercial broiler strains and a random-bred broiler strain.

Wooden breast myopathy (WBM), or "woody breast" or "wooden breast" affects modern, rapidly growing, high breast-yield broiler chickens. Decreased meat quality due to undesirable organoleptic properties and condemnation of affected breast meat cause economic losses. The pathogenesis of WBM remains unknown. In this study, WBM lesion development was determined in three modern broiler strains and Athens Canadian Random Bred (ACRB) broilers, a 1950s unselected broiler chicken. Correlations between WBM severity and incubation temperature profile, sex, strain, body weight, and lymphocytic phlebitis were also determined. At 2, 4, 6, and 8 weeks of age, samples of breast muscle from 10 male and 10 female birds from each strain, incubated under optimal or low-early, high-late temperatures, were scored histologically for severity of WBM and lymphocytic phlebitis. WBM lesions, identified as early as 2 weeks, became progressively more severe with age and growth in the three commercial broiler strains. WBM severity was significantly correlated with lymphocytic phlebitis and body weight. Lymphocytic phlebitis and minimal WBM were present in the ACRB broilers at all samplings, but did not progress in severity over time. There were no significant differences in severity of WBM among the commercial broiler strains, between sexes, or between incubation temperature profiles. The positive correlation between WBM severity and lymphocytic phlebitis indicates vascular injury is likely an important factor in the pathogenesis. Mild muscle lesions in ACRB birds without overt clinical signs indicate subclinical muscle disease may have been present in broilers prior to the description of WBM.

Selected blood chemistry values in mobility-impaired broiler breeder hens with suspected calcium tetany using the i-STAT handheld clinical analyzer.

Calcium tetany is a poorly defined disease of broiler breeder hens that results from acute hypocalcemia. It is characterized by impaired mobility, increased mortality, and absence of gross lesions that would explain the impaired mobility. To evaluate if hens with impaired mobility had calcium tetany or other abnormalities, blood values from normal and affected hens were determined using the i-STAT handheld clinical analyzer. Three flocks were evaluated weekly prior to peak production (range 25-30 wk of age) comparing normal hens to hens with clinically apparent calcium tetany. Calcium tetany suspect (CaTS) hens from four additional flocks were also evaluated. Significant hypocalcemia (P < 0.001) was observed in CaTS hens (average = 1.14 mmol/L ionized calcium [iCa]) compared to normal hens (average = 1.53 mmol/L iCa) in only one of three flocks sampled weekly. Clinically affected hens from one of the other four flocks also had hypocalcemia. Blood value abnormalities in mobility-impaired hens without hypocalcemia included hypernatremia. Findings in this study indicate calcium tetany is one cause of impaired mobility in breeder hens, but mobility impairment without hypocalcemia can also occur. Calcium tetany should be confirmed by finding significantly decreased levels of iCa in the blood, as diagnosis based on clinical presentation and necropsy results can be inaccurate. The i-STAT handheld clinical analyzer is an efficient, relatively low-cost method to determine iCa and other blood chemistry values that may be associated with impaired mobility in broiler breeder hens.

Selected blood chemistry and gas reference ranges for broiler breeders using the i-STAT handheld clinical analyzer.

Selected blood chemistry and gas reference ranges for clinically healthy broiler breeder hens were established using CG8+ cartridges in an i-STAT handheld point-of-care clinical analyzer. Samples from 165 hens (25-36 wk of age), representing three broiler breeder strains reared by four integrators, were evaluated. A standardized sampling technique was developed to minimize instrument error readings. The following reference ranges and means, respectively, were determined: sodium (141.6-152.6, 147.1 [mmol/L]), potassium (4.1-5.7, 4.9 [mmol/L]), ionized calcium (1.20-1.73, 1.47 [mmol/L]), glucose (207.2-260.7, 234.0 [mg/dl]), hematocrit (21.3-30.8, 26.1 [% packed cell volume]), hemoglobin (7.3-10.5, 8.9 [g/dl]), pH (7.28-7.57, 7.42), carbon dioxide partial pressure (25.9-49.5, 37.7 [mm Hg]), oxygen partial pressure (32.0-60.5, 46.2 [mm Hg]), bicarbonate (18.9-30.3, 24.6 [mmol/L]), total carbon dioxide (19.9-31.5, 25.7 [mmol/L]), base excess (-6.8 to 7.2, 0.2), and oxygen saturation (70.6-93.3, 82.0 [%]). Wide ranges in blood gases and base excess occurred in all strains. Cobb strain hens had significantly lower glucose and higher partial and saturated oxygen values compared with two Ross strains. Significant differences in several blood parameters were found among different integrators and in older postpeak production birds. The i-STAT handheld point-of-care clinical analyzer provides rapid, relatively low cost, blood chemistry values that are useful for investigating broiler breeder flock diseases of unknown or uncertain etiology, especially those suspected of having a metabolic cause.