FUNCTIONAL AND METABOLIC CHANGES IN RABBITS UNDERGOING CONTINUOUS HEAT-STRESS FOR 24 DAYS

Intensively reared rabbits are particularly sensitive to heat stress. For this reason if is useful to identify reliable stress indicators to evaluate peculiar stress conditions of the breeding environment. In o rder to recognize which changes in biochemical and functional measurem ents can be utilized as stress indicators, three groups of eight New Z ealand White rabbits, of 2.8 kg body weight and 11 weeks of age, were kept in individual cages and submitted to different environmental cond itions. Group 1 was located in a climatic chamber at 33.5 (s.e. 0.5)de grees C and relative humidity 0.62 (s.d. 0.05) and groups 2 and 3 (con trol) at 18.0 (s.d. 0.5)degrees C. Group 1 was given ad libitum a comm ercially pelleted diet, group 2 was pair-fed with group 1, and group 3 was given food ad libitum. For all the groups, at days 0, 1, 6, 12 an d 24, the following measurements were made: body weight, rectal temper ature, food consumption and plasma glucose, cholesterol, urea, triglyc erides, uric acid, and glutamate oxalacetate transaminase, glutamate p yruvate transaminase, thiobarbituric acid-reactive substances, vitamin A and vitamin E, SH-groups and total (peroxil) radical-frapping antio xidant parameter (TRAP). Food consumption of animals exposed to 33.5 d egrees C was strongly reduced in the 1st day (13.6 v. 161.6 g/day); a gradual increase until the end of the trial was then observed (98.8 v. 177.3 g/day). Rectal temperature rapidly increased and remained stabl e and higher than in the control groups all through the trial (P < 0.0 1). The major changes in the measurements of the heat stressed animals were a significant increase of the plasma level of vitamin E at days 6, 12, 24 (P < 0.05), and a significant reduction of the plasma concen tration of SH-groups and TRAP (P < 0.05). The results suggest all impa irment or overload of antioxidant systems after thermal stress, indica ting a reduced resistance to biological and environmental stress facto rs. The results also indicate that some parameters of antioxidant syst ems can be used to select a significant stress indicator.