NUTRITION AND FEEDING 251 



high-quality, 36"o protein catfish feed (Appendix F) is an adequate supple- 

 mental feed for fry and small fingerlings as they will get a large portion of 

 their nutrients from natural pond organisms. 



Feed first should be pelleted or extruded before it is reduced to smaller 

 particle sizes. Fat sprayed onto the feed after processing reduces the loss of 

 water-soluble vitamins. 



Growth of channel catfish fingerlings is similar with either sinking or 

 floating pellets, provided that the nutrient contents are the same. Floating 

 feeds are a valuable management tool to help determine the effects of low 

 dissolved oxygen content and low or high water temperature on feeding, 

 general vigor, and health of fish during the feeding season. It also is help- 

 ful in determining amounts of feed to give fish in special culture systems 

 such as cage feeding, raceway feeding, and ponds having abundant rooted 

 vegetation. 



Table 28 presents a feeding guide for channel catfish in ponds, and 

 Table 29 offers one for catfish in raceways. The pond feed is a supplemen- 

 tal, 36"o protein diet; that for raceways is a complete formulation. See Ap- 

 pendix F for ingredients. 



Low dissolved oxygen levels depress feeding activity of catfish, and fish 

 should not be fed in early morning for this reason. Neither should they be 

 fed late in the day because their increased metabolic oxygen requirement 

 during active feeding and digestion will coincide with the period of low 

 dissolved oxygen in the pond during the night and early morning. The 

 best times to feed are between mid- morning and mid- afternoon. 



The optimal temperature for catfish growth is approximately 85°F; as 

 temperature decreases, food consumption decreases proportionally. Gen- 

 erally, catfish do not feed consistently in ponds when the water tempera- 

 ture drops below 60°F; below 50°F they will feed, but at greatly reduced 

 levels and frequencies. Below 60°F, the efficiency of digestion and metabo- 

 lism drops markedly. 



During colder months, feed catfish only on warm days and only what the 

 fish will consume readily. A recommended guide for winter feeding of cat- 

 fish in ponds is to feed the fish 0.75-1% of their estimated weight daily 

 only when the water temperature is above 54°F, and not to feed at lower 

 temperatures. 



There are no reliable data on the best feeds for catfish in the winter. 

 Catfish do not respond as well to high- protein diets in cool weather as in 

 warm weather. This may indicate that lower- protein feeds (below 32%) are 

 more economical in cold water. Digestibility of carbohydrates is suppressed 

 even more at low temperatures than the digestibility of proteins and fats, 

 indicating that high-grain feeds are not utilized by catfish in cool weather. 

 Therefore, winter rations should contain less protein and carbohydrates 

 than those fed during the summer. 



