Electrocardiographic Indices, Circulating Electrolytes and Cardiac Enzymes of Apparently Healthy Aged Layer Hens

BACKGROUND: Information regarding the effects of physiological situation (age and egg lying) on heart electrical activities and blood profile of layer hens can aid in better understanding the cardiovascular system healthiness and performance in these birds. OBJECTIVES: The present study was carried out to evaluate the electrocardiographic parameters and circulating levels of electrolytes and cardiac enzymes in apparently healthy 112 week-old Lohmann LSL-classic layer hens. METHODS: Fifty apparently healthy 112 week-old Lohmann LSL-classic layer hens were selected. The electrocardiograms were recorded and blood samplings were performed for all birds. Serum concentrations of sodium, chloride, phosphorus, calcium, potassium, magnesium, aspartate aminotransferase, alanine transaminase and lactate dehydrogenase were assayed. RESULTS: The mean±SD of heart rate was 333.5±28.6 beats/min. The P wave was seen in only 20% of birds and its duration and amplitude were 0.03±0.01 sec and 0.05±0.05 mV, respectively. PR, RR and QT intervals were 0.04±0.02, 0.18±0.02 and 0.13±0.01 sec., respectively. The circulating levels of calcium, phosphorous, and magnesium were 19.94±3.63, 5.02±1.15, 2.46±0.23 mg/dL and blood levels of sodium, chloride, and potassium were 146±2.5, 6.10±0.84 and 119.20±2.38 mEq/dL, respectively. Serum values of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase were 240.20±51.26, 6.20±2.28 and 1262.40±344.18 U/L, respectively. CONCLUSIONS: Based on the clinical healthiness of the studied birds, all of the electrocardiographic indices, circulating electrolytes and cardiac enzymes in aged layer hens were close to values in younger hens. So, increase of the laying period over 100 weeks had no harmful and adverse effect on the bird’s physiology and welfare.