Effects of frequency and time of feeding on growth and feed utilization in two Asian catfishes, Pangasius bocourti (Sauvage, 1880) and Pangasius hypophthalmus (Sauvage, 1878).

摘要

In the first experiment, Pangasius bocourti fingerlings were fed to satiation with the frequency of one, two or three meals. In the second (for P. bocourti) and third (for P. hypophthalmus) experiments, fish were fed equal fixed rations with four feeding frequencies including one-, two- and three-meal frequency and continuous feeding in two feeding periods: daytime or night time. The results show that P. bocourti fingerlings fed to satiation resulted in higher growth when meal frequency was increased from one to two or three feeds per day, but growth performance of two- or three-meal experiment fish did not differ significantly (SGR of 2.6%d-1 3.4%d-1 and 3.6%d-1 for one, two and three-meal feeding, respectively). When fed an equal fixed ration (not to satiation), P. bocourti and P. hypophthalmus fingerlings did not display much alterations in growth performance and feed efficiency with increased meal frequency (SGR of 4.0%d-1, 4.0%d-1 and 3.9%d-1 for P. bocourti; and 3.4%d-1, 3.5%d-1 and 3.4%d-1for P. hypophthalamus) when fed once, twice or thrice at night, respectively. However, one-meal frequency in the morning in both species tends to result in lower growth and smaller feed utilization efficiency than multiple feeding treatments. This is apparently not due to feeding frequency but likely due to time of feeding (daytime vs. night time) since one-meal frequency during the night gave the same growth and feed efficiency as other feeding regimes. Continuous feeding in both species always led toreduced growth performance and feed utilization efficiency (SGR of 3.4%d-1 vs. 3.6%d-1 and 3.6%d-1 in two- or three-meal feeding of P. bocourti during the day). Clearly, increased meals in both species in fixed ration do not improve growth and feed utilization efficiency; on the contrary, continuous feeding significantly reduces growth and feed utilization efficiency. Based on this study, both species clearly exhibit higher growth and better feed utilization with nocturnal than diurnal feeding. The SGRs were 3.68-4.02%d-1 at night feeds when compared to 3.39-3.62%d-1 at daytime feeds of P. bocourti. Increased meal frequency and nocturnal feeding of an equal fixed ration usually resulted in relatively higher fat deposition in both species and a higheradipose-somatic and hepato-somatic index.