Abstract
Several studies carried out on humans and other mammals show that the temporal organisation of haematological parameters in the blood exhibit daily rhythms; however, such studies have been rare in poultry reared under a natural photoperiod. The present study investigated the occurrence of daily rhythms in blood parameters of broiler chickens kept under tropical climatic conditions. Ten 6–7-week-old broiler chickens served as subjects of the study. They were kept in standard individual cages under natural light-dark cycle and given access to feed and water ad libitum. Two milliliters of blood was collected from each bird via intravenous cannulae inserted into the wing vein. The blood samples were collected every 4 h over a 24-h period, starting from 09:00 h on the first day and completed at 09:00 h on the second day. The blood samples were analysed for erythrocyte, total and differential leucocyte counts. A trigonometric statistical model according to the single cosinor procedure was used to describe the periodic parameters and their acrophases, and ANOVA was used to determine significant differences. The results demonstrated the existence of daily rhythms in packed cell volume, haemoglobin, white blood cell, red blood cell, heterophil, lymphocyte, eosinophil and monocyte counts, while total protein displayed no rhythm. The characteristics of the haematological parameters showed that the acrophases were restricted to the light phase of the light/dark cycle, precisely at 09:00 h, except for eosinophil and heterophil counts, which had acrophases at 21:00 h. The amplitudes of the blood parameters varied, with packed cell volume having the greatest amplitude of 4.2 ± 0.5, closely followed by lymphocyte (3.4 ± 0.5) and heterophil (2.3 ± 0.2) counts. In conclusion, the results of the study demonstrated the existence of daily rhythms with diurnal acrophases in blood parameters of broiler chickens kept under natural photoperiods and tropical conditions.
Highlights
Circadian rhythms, which are about-24-hour oscillations in behaviour and physiology, are reflected in all cells of the body, aimed at optimising cellular functions and meeting environmental challenges associated with the solar day [1]
The present study investigated the existence of daily rhythms in blood parameters and their characteristics in broiler chickens reared under natural tropical conditions
Mean, maximum and minimum values of blood parameters of broiler chickens housed under a natural photoperiod and thermal environmental data inside the pen Table 1 shows the mean, maximum and minimum values of blood parameters of broiler chickens, and the thermal environmental data inside the pen
Summary
Circadian rhythms, which are about-24-hour oscillations in behaviour and physiology, are reflected in all cells of the body, aimed at optimising cellular functions and meeting environmental challenges associated with the solar day [1]. The multi-oscillatory network in all levels of cell line is coordinated by the master pacemaker clock located in the suprachiasmatic nucleus (SCN) of the hypothalamus, which directs an animal’s rhythmic expression of physiological functions and behaviour via a hierarchical system [1, 2, 3]. The avian circadian system is more complex than that of mammals. Birds have extraocular photoreceptors; and, correspondingly, they have independently-regulated pacemakers, which are lacking in mammals [6]. The study of chronophysiology in avian species may require more attention
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