Effects of long-term exposure to high temperature on growth performance, chemical composition, hematological and histological changes, and physiological responses in hybrid catfish [♂Clarias gariepinus (Burchell, 1822) ×♀C. macrocephalus (Günther, 1864)].

The anthropogenic and climate-driven rise in water temperature is expected to have an effect on the physiological functions of ectothermic species. In the present study, hybrid catfish were subjected to three different temperatures (27, 32, and 37 °C) for 50 days to examine the effect of long-term exposure to high temperatures on growth and physiological parameters. The results showed that acclimation temperature improves growth and feed utilization with a quadratic effect (P < 0.05). The highest performance was observed at 32 °C, but fish acclimated at 37 °C decreased growth and feed utilization. In addition, skin darkening was observed in fish acclimated with increasing temperatures. Fat content of whole-body, liver, and dorsal muscle of fish was decreased by increasing temperatures (P < 0.05). Higher temperature levels significantly increased in all blood parameters (P < 0.05), except for high-density lipoprotein cholesterol, which was quadratically decreased (P = 0.004). Fish acclimated with increasing temperature also altered gill and liver histology such as gill shortening, hyperplasia and edema in the connective tissue, severe hyperplasia of epithelial cells, and desquamation, hepatocyte vacuolization, nuclei displacement, and pyknotic hepatic cells. While mucus cells were periphery distributed in the subcutaneous skin. In addition, cuboidal shape-like of club cells and melanophores were also observed in fish acclimated at 37 °C resulting in increased epithelial layer thickness. After fish subjected to increasing temperature exhibited an increase in the number of operculum movement and number of gasping for air (P < 0.05) in all acclimated groups. While fish challenged at 37 °C showed higher critical thermal maximum (CTmax, 41.33 °C) than those of the other groups. Overall, the maximum temperature (37 °C) may rick to hybrid catfish. To prevent physiological damage to the fish, as well as reduction of growth and productivity, the temperature in the aquaculture setting should be kept below 37 °C.

Empirical Evaluation and Prediction of Protein Requirements for Maintenance and Growth of 18-24 Months Old Thai Swamp Buffaloes.

In some geographical areas and in certain breeding situations, the interpretation of increased gain in the bovine is difficult to investigate. Due to their inherent genetic variations, their energy and protein needs vary as a function of inherent genetic differences, making these requirements difficult to accurately assess in bull species, e.g., Thai swamp buffalo. The study aimed at investigating and predicting protein requirement systems, by the provision of an abundant energy intake of 2.2 Mcal/kg DM for the maintenance and growth of Thai swamp buffaloes using a comparative prolonged feeding trial for 90 days. Sixteen bull Thai swamp buffaloes at the initial (Age: 18-24 months; BW: 233 ± 25.0 kg) were assigned into four treatment groups, four buffaloes each, fed 5.4, 6.6, 8.5, and 10.5% DM crude protein (CP). CP intake, BW, and physiological fluid were determined. The net CP requirements for maintenance and growth of Thai swamp buffaloes were 5.41 g CP/kg W0.75 and 0.46 g CP/g average daily gain (ADG), respectively. Our results indicated that CP requirement increases when the BW increases. An increased dietary CP resulted in increased amounts of blood urine nitrogen (N), N absorption, total volatile fatty acid, urinary purine derivative, and the microbial N. Notably, the net CP requirement for growth of Thai swamp buffalo was higher than it reported in NRC, but the maintenance was lower.