EFFECT OF FEEDING ON EXCESS POST-EXERCISE OXYGEN CONSUMPTION IN JUVENILE CHINESE CATFISH (SILURUS ASOTUS LINNAEUS)

Feeding and exercise are normal, essential components of everyday lives of fish. Under natural conditions, animals often need to undertake these two activities simultaneously and it is important to study the interactions between these activities. Thus, to investigate the impact of feeding and subsequent nutrient digestion and absorption on the metabolic and respiratory recovery processes after exhaustive exercise (chasing) in juvenile Chinese catfish (Silurus asotus Linnaeus) (N=30, body mass: 54.51-86.89 g, body length: 19.51-24.59 cm), the excess post-exercise oxygen consumption (EPOC) of the experimental fish before feeding, 12h after feeding (8.740.40)% body mass and 60h after feeding (8.840.25)% body mass were studied at (25.01.0)℃. The light cycle was 12L:12D. Cutlets of freshly killed loach species (Misgurnus anguillicaudatus) without viscera, head and tail were used as the test meal, and oxygen consumption (MO2) was adjusted to a standard body mass of 1 kg using a mass exponent of 0.75. The ventilation frequency (Vf) was also documented before and during the recovery process after exhaustive exercise. No significant differences in either resting MO2 (MO2rest) or Vf (Vfrest) were found after three days of fasting among all experimental groups before the experiment. However, there was significant difference on the MO2 before the exhaustive exercise, i.e. pre-exercise MO2, among the three groups. Both the MO2 and the Vf increased immediately after exhaustive exercise and slowly returned to pre-exercise values in all three experimental groups. The peak MO2 (MO2peak) values were (180.536.79), (222.4710.14) and (181.6510.94) mgO2/(kgh) at 0h (before feeding), 12h and 60h after feeding and the EPOC values were (66.586.40), (42.4910.13) and (53.465.80) mgO2 at 0h (before feeding), 12h and 60h after feeding, respectively. Both EPOC and MO2peak of fish in the 12h after feeding group significantly differed from the other two groups (P0.05). Our observation suggested that: (1) neither digestion nor exhaustive exercise led to maximal MO2 in juvenile Chinese catfish; (2) exhaustive exercise was curtailed under postprandial exercise, and the post-exercise metabolic recovery process became faster in a postprandial fish when compared to fasting ones. This faster recovery was possibly due to the alkaline tide (metabolic base loading during digestion in vertebrates) elicited by feeding, which significantly prevented the decreases in pH and HCO3- immediately after exhaustive exercise.