Thermoregulatory and blood osmolality consequences of salt loading in chicks (Gallus gallus)

All physiological variables and processes are either directly or indirectly influenced by body temperature (Tb). However, Tb does not only influence but can also be influenced by several physiological processes, such as osmolality of body fluids, especially because the most efficient thermolytic (i.e., heat loss) mechanisms are water-related effectors. If body water loss by evaporative cooling mechanisms is not replaced, dehydration ensues, the osmoregulatory system is stimulated and, consequently, effectors to restore body fluid loss will be activated, probably causing inhibition of those water dependent thermolytic effectors. As the influence of plasma osmolality in Tb in early life is less studied and constitutes an important issue for aviculture field, the aim of the present study was to investigate the effect of increase in plasma osmolality in Tb of 6 days old chikcs. Body temperature and plasma osmolality (PO) of animals were taken at 0, 60, 110 and 160 min after intraperitoneal injection of isotonic (0.9%) and hypertonic (10%) saline solutions. Ambient temperature was increased from 31 to 37^oC after time 60 min. Heat exposure increased Tb (39.8 versus 40.4^oC) and PO (317.0 versus 335.0.mM) at times 110' and 160' in both isotonic and hypertonic saline groups. No difference in PO was observed between groups at time 110', but hypertonic saline increased PO more than isotonic saline at time 160'. Tb for hypertonic saline treated animals showed higher values in comparison with those that received isotonic saline at time 110' and 160'. In addition, animals treated with isotonic and hypertonic saline had similar Tb at time 110' and 160'. Our preliminary results indicate that dehydrated mammals conserve body water by reducing thermoregulatory evaporative cooling responses eg, panting and sweating. Increased body temperature (Tb) may result. Thus increasing the trend of the powder can be due to the preservation of body water in heat stress occasion and increase PO.