Blood system response of chickens to changes in environmental temperature

Abstract

Hemodynamic changes were studied in broiler chickens during exposure to constant temperatures (10 to 35 C) or diurnal temperature cycles (10:30 C and 15:35 C), and during acute heat or cold. Packed cell volume (PCV) was significantly high at low constant temperatures (10 and 15 C), whereas at high temperatures (30 and 35 C) plasma volume (PV) was significantly high. A linear relationship between hematocrit and heart weight was observed and indicates an adaptation of heart mass to changes in cardiac output and hematocrit to meet the demands of increased basal metabolic rate. Only during the diurnal temperature cycle of 15:35 C did a significant increase in PV occur when ambient temperature (Ta) was raised form 15 to 35 C. Acute exposure of chickens to high temperature did not affect PV or PCV, but resulted in hyperthermia (44.7 +/- 0.4 C). Changes in PCV are probably related to modulation of the supply of oxygen to accommodate changes in heat production. The significant hypervolemia observed at high temperatures could occur to provide the fluid needed for heat dissipation by panting. The lack of response of the blood system to acute temperature changes may be at least partially responsible for the chickens' failure to control body temperature.

Effect of early feed restriction on physiological responses, performance and ascites incidence in broiler chickens raised in normal or cold environment

“…Compared with NT chickens, CT chicks had significantly higher hematocrit which is in agreement with previous findings (Yahav et al, 1997;Ipek and Sahan, 2006), and can be a sign of enhanced erythropoiesis in CT. Thermoneutral zone of chickens is too narrow and exposure to suboptimal temperatures increases their oxygen demand (Julian et al, 1989), which stimulates erythropoiesis (Luger et al, 2003) leading to elevated red blood cells number and hematocrit. In the current study, CT birds showed higher levels of T 3 (Table 5) which is an indication of raised metabolic rate and increased oxygen demand in these chickens.…”

“…Pulmonary hypertension triggers series of events, which finally lead to the ascites syndrome (Julian, 2000 and2007). During cold stress several studies have reported important physiological changes, including classic hematological changes and increased right ventricle weight per total ventricle weight (RV : TV) ratio (Yahav et al, 1997;Luger et al, 2003;Ipek and Sahan, 2006), but there is only very little or no information on the other physiological responses such as blood chemical alterations.…”

Effect of increased incubation temperature onHsp90 and 60 gene expressions in coloured broiler chickens

“…The response of cellular mechanisms to the long-term effect of thermal conditioning is complex and contradicting observations were reported in earlier studies. One school of thought suggesting the high Hsp expression is associated with better heat tolerance (Wang & Edens 1993, 1998) while the other is low level of expression (Yahav et al 1997). The present findings were in accordance with Yahav et al (1997) wherein thermal conditioning during early age induced thermotolerance by adaptation and subsequent low level of Hsp expression.…”

“…One school of thought suggesting the high Hsp expression is associated with better heat tolerance (Wang & Edens 1993, 1998) while the other is low level of expression (Yahav et al 1997). The present findings were in accordance with Yahav et al (1997) wherein thermal conditioning during early age induced thermotolerance by adaptation and subsequent low level of Hsp expression. The mechanism to combat heat stress in the present study involves reducing hyperthermia by protecting the body tissues from being exposed to stress, which might be partly due to the stability of tissues to hyperthermia due to earlier conditioning.…”

The Effects of Different Eggshell Temperatures Between Embryonic Day 10 and 18 on Broiler Performance and Susceptibility to Ascites

“…environmental (e.g., high eggshell temperatures during incubation, altitude, low ambient temperatures, etc.) (Yahav et al, 1997), and management (e.g., ventilation, disease status) factors Sahan et al, 2006). Although the peak incidence of ascites occurs in the 5 th or 6 th week of the growing period, the etiology of the disease may be initiated much earlier, even during the embryonic stage (Coleman & Coleman, 1991).…”