Influence of repetitive periods of fasting and satiation feeding on growth and production characteristics of channel catfish, Ictalurus punctatus.

摘要

Two feeding trials were conducted to determine the effects of repetitive periods of fasting and satiation feeding on growth and production characteristics of channel catfish. In the laboratory, juvenile catfish (22+or-2 g) were stocked into 20, 114-l tanks at a density of 25 fish per tank and fed a commercial diet in one of three feeding regimens: daily, satiation feeding for 72 days (full-fed); alternating periods of 5 days of fasting followed by 14 days of daily, satiation feeding (5-day fasted); and alternating periods of 10 days of fasting followed by 14 days of daily, satiation feeding (10-day fasted). Five-day fasted fish were fed for 57 days and fasted for 15 days (total). Ten-day fasted fish were fed for 42 days and fasted for 30 days (total). There were no differences (P>0.05) among treatment groups in catfish weight gains (pooled mean, 24.12+or-8.65 g), feed conversion ratios (pooled mean, 1.64+or-0.40), or condition factors (pooled mean, 0.82+or-0.12) when results were compared after an equal number of days (42 days) of satiation feeding. However, at termination of the feeding trial (day 72), the body weights of fish in the 5-day fasted and 10-day fasted treatments were 25% and 41% lower, respectively, than the body weight of full-fed fish. The specific growth rate (SGR) of fish in the 10-day fasted treatment (0.45+or-0.08% day-1) at termination of the growth trial was significantly lower than the SGR of fish in the full-fed and 5-day fasted treatments (pooled mean, 0.70+or-0.10% day-1), which were not significantly different. Results indicated that fish subjected to repetitive 14-day periods of satiation feeding after repeated 5-day or 10-day periods of fasting were unable to achieve the final body weight of fish fed to satiation from the beginning of the growth trial, although a compensatory growth response during each 14-day satiation feeding period usually did occur. A second experiment, conducted in 21 ponds (0.08-ha each) stocked at a density of 18,532 fish ha-1 (mean body weight, 31+or-1 g), evaluated the same treatments under practical production conditions. The fish were fed to satiation daily for 158 days (full-fed), 112 days (5-day fasted), or 97 days (10-day fasted) with the same diet used in the laboratory trial, and feed consumption was closely monitored to minimize waste. Fish in the 5-day fasted and 10-day fasted treatments consumed 30% and 38% less diet, respectively, than fish in the full-fed treatment during the course of the production trial. At harvest, feed conversion ratios (pooled mean, 2.17+or-0.35) and protein efficiency ratios (pooled mean, 1.43+or-0.26) did not differ (P>0.05) among treatments. Mean body weights of fish in the 5-day fasted and 10-day fasted treatments were 24% and 29% lower (P<=0.05), respectively, than the mean body weight of full-fed fish; however, the yield (kg ha-1) of pond-run fish (all sizes) in the 5-day fasted treatment did not differ significantly from the yield of pond-run fish in the full-fed treatment. The SGR of fish in the full-fed treatment (1.75+or-0.25% day-1) was significantly higher than the SGR of fish in the 5-day fasted and 10-day fasted treatments (pooled mean, 1.42+or-0.11% day-1), which were not significantly different. The yield of marketable (>=0.46 kg) fish in the full-fed and 5-day fasted treatments (pooled mean, 3441+or-936 kg ha-1) did not differ significantly, but the mean body weight of marketable fish in the 5-day fasted treatment (470+or-30 g) was lower (P<=0.05) than that of marketable fish in the full-fed treatment (570+or-30 g). Under the conditions of this study, the diet-related cost of producing 1 kg of pond-run fish (US$0.57-0.68 kg-1) did not differ significantly among treatments. The diet cost of producing marketable fish in the 5-day fasted treatment was lower (P<=0.05) than the diet cost of producing marketable fish in the 10-day fasted treatment, but not different (P>0.05) from the diet cost of producing marketable fish in th