Clarias macrocephalus has been extirpated in most regions in the Philippines and as a preliminary study towards its reintroduction, we aimed at enhancing the growth and reproductive performance of the broodstock. Several studies have identified thiamine deficiency as a factor in the extirpation of some important fish species in the wild. The present study aimed to determine the effects of elevated dietary carbohydrates and benfotiamine, a more bioavailable analog of thiamine (vitamin B1). Three diets were used, namely, a commercial diet specific for catfish was used as the control diet (Com), a high carbohydrate (HC) diet, and a benfotiamine-supplemented HC diet (HCB). Results show that survival of the subadult catfish in captivity for 10 weeks was remarkably high, exhibiting an average of 99% for all three treatments (P>0.05). HCB diet resulted in significantly higher final average body weight (FABW), weight gain (WG), specific growth rate (SGR), and significantly best food conversion ratio (FCR) (P<0.05) than the values for both Com and HC groups (P>0.05). For the reproductive performance, female Asian catfish fed the HCB diet exhibited significantly heavier ovary and liver (P<0.05) than those female catfish fed either the Com or HC diet (P>0.05). GSI of the female catfish and fecundity were significantly higher in the HCB group (P<0.05) than in the Com or HC group (P>0.05). In the male catfish, testes were significantly heavier in the HCB group (P<0.05) than in the Com or HC diet (P>0.05). HSI, male LW, and LL were significantly higher in the HC and HCB groups (P>0.05) than in the Com group (P<0.05). GSI values of the male catfish were significantly highest in the HCB (P<0.05), followed by the HC group, and significantly lowest in the Com group (P<0.05). The larval survival rate for one week was significantly higher (P<0.05) in the Asian catfish fed the HCB diet than in those fed the Com or HC diet (P>0.05). In conclusion, elevating dietary carbohydrates in the diet from 7.70% to 22.73% (i.e., Com to HC diet, respectively) did not negatively affect the growth and reproductive performance of the Asian catfish. Further supplementation of benfotiamine at 0.02% to the HC diet enhanced significantly both the growth and reproductive performance of the Asian catfish.

Three experiments were conducted to investigate the use of pollen from Pinus tabulaeformis (PP), as a possible replacement for synthetic 17-alpha-methyltestosterone (MT) in Nile tilapia, Oreochromis niloticus larvae diets. In experiment 1, the attractability of a diet containing PP (640mg/kg) compared to a control diet containing no PP was assessed. Experiment 2, lasting 8 weeks, evaluated the effects of PP on growth, food conversion efficiency, survival, and sex inversion compared with that of 17a-methyltestosterone (MT). Results showed that after 60 days of feeding, 100% of Nile tilapia fed the MT diet converted to male; this was statistically similar to the percentage of fish fed the PP diets (81.0% to 89.1% male, p<0.05). Results of the growth trial showed that final weight (FW) and weight gain (WG) of fish fed diets containing 0.08 g/kg PP and 0.64 g PP/kg were significantly higher than those fed the MT diet (p<0.05). Feed intake (FI) of all experimental fish were statistically similar (p>0.05). The group fed 0.08 g PP/kg diet exhibited significantly higher SGR than the MT group. The MT group exhibited lower food conversion efficiency (i.e. higher FCR) than the control group. Fish fed diets containing 0.08 and 0.64 g PP/kg exhibited better FCR than those fed the MT diet. Survival was statistically similar for all dietary treatments (p>0.05). In experiment 3, fish larvae were fed: no PP (control diet), a medium dose (0.32 g/kg), and a high dose (0.64 g/kg) of PP for 14 days and assayed for alpha amylase and trypsin activities. Results showed that diets containing PP were significantly more attractive to the fish than the control diet (p<0.05) for the first 5 min. At the 6th min, results were statistically similar for both PP diets. In conclusion, PP could replace MT in effecting sex reversal from female to male with statistically similar results; it could also promote better growth and food conversion efficiency at the minimum dietary level of 0.08 mg PP/kg.

Feeding trials were conducted to evaluate the effects of dietary pine pollen from Pinus tabulaeformis Carr. on masculinization, growth, food conversion efficiency, and survival of Clarias gariepinus. Experimental diets were prepared using a commercial feed for fry as basal diet with 5 levels of pine pollen supplementation: 0 (control, T1), 80 (T2), 160 (T3), 320 (T4), and 640 (T5) mg/kg diet; two positive control diets were also included, namely 17--methyltestosterone, and testosterone at 60 mg/kg diet. Two feeding trials were conducted, the first; larvae to fry for 72 days (Phase 1) and the second; fry to fingerling for an additional 45 days (Phase 2). Results showed that the percentage of males was significantly lower in the untreated diet (50.4%) and significantly higher in all of the pine pollen groups although there was no significant difference between the pine pollen groups. The male percentage was significantly highest in the 17--methyltestosterone and testosterone groups with no significant difference between the two groups. Phase 1 feeding showed that pine pollen did not affect growth, feed intake, food conversion efficiency, and survival of catfish. In Phase 2 feeding, the final average body weight (FABW), weight gain (WG), feed intake (FI), and protein efficiency ratio (PER) in all pine pollen groups similarly increased, but specific growth rate (SGR) and food conversion ratio (FCR) did not. 17-methyltestosterone treatment significantly increased WG and SGR, but enhancement was significantly inferior to the pine pollen groups (P<0.05). Testosterone did not have any effect on any of the response parameters. FIs were significantly higher in the pine pollen groups than either the control, 17--methyltestosterone, and testosterone groups. There was no effect on survival rate in any of the treatments All rates were statistically similar (P>0.05). Conclusion: pine pollen resulted in slightly but significantly inferior androgenic effect, but anabolic effect was superior compared to both 17--methyltestosterone, and testosterone. Its use for sex reversal and improved growth is recommended. The IJA appears exclusively as a peer-reviewed on-line open-access journal at http://www.siamb.org.il. To read papers free of charge, please register online at registration form. Sale of IJA papers is strictly forbidden.

This study aimed to assess the effects of 17α-methyltestosterone (MT) on the growth and reproductive performance of male Asian catfish (Clarias macrocephalus). A total of 36 immature male Asian catfish (ABW = 125.97 g) were randomly distributed into 12 circular tanks, and fed with either the control diet (with no MT) or diets containing MT at 60 mg·kg-1, 90 mg·kg-1, or 120 mg·kg-1 for 45 days. Results showed that weight gain (WG), specific growth rate (SGR) and feed intake (FI) were significantly higher in the male catfish fed with diets containing 60 and 90 mg·kg-1 MT than in those fed with the control diet. Also, the diet attractability test revealed that the 60 and 90 mg·kg-1 MT groups significantly attracted more catfish than did the control diet; however, increasing MT to 120 mg·kg-1 reduced its attractability to the immature male catfish. MT-treated male catfish exhibited significantly heavier and significantly longer testes than male catfish fed the control diet at the termination of the feeding trial. These male catfish also exhibited significantly higher gonadosomatic indices (GSI) than catfish in the control group. Following induced spawning of nontreated female catfish and artificial fertilization of its eggs using testis preparation from the experimental male catfish at the termination of the feeding trial, results showed that testis preparations from all MT-treated males resulted in significantly higher fertilization (FR) and hatching rates (HR) of the eggs. In conclusion, incorporating MT to the diet improved both the growth and reproductive performance of the male Clarias macrocephalus. Precisely, dosages of optimal dietary MT using a quadratic model for maximal SGR, GSI, FR, and HR values were estimated to be 58.3, 75.0, 90.6, and 78.2 mg·kg-1, respectively.

Two feeding trials were conducted to investigate the effects of dietary pH (pH 2.5, 3.7, 4.6, 5.7-control, pH 7.0, and pH 8.0) and dietary acid source (acetic acid, citric acid, hydrochloric acid and control-no acid) on growth rate and feed utilization efficiency of the Nile tilapia fry. In addition, attractability of the diets at different pH and dietary acid sources were determined. Results of the first feeding trial showed that the feed with pH adjusted to 4.6 resulted in significantly highest final average body weight (FABW), weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER) and most efficient food conversion ratio (FCR) in the Nile tilapia fry. Survival was 100% in diets with pH 3.7 up to 7.0; the diet with pH 2.5 exhibited significantly lowest survival followed by the pH 8.0 diet. In the second feeding trial, diets that contained hydrochloric, citric or acetic acids that were used to adjust the pH to the optimal 4.6 resulted in higher FABW, WG, SGR, and PER values but lower FCR values than did the control diet; these parameters were not significantly different among the dietary groups. This study demonstrated that the dietary pH promoted growth and efficiency in the Nile tilapia fry and that the three acids that were used were similar in their effects on growth and efficiency. Furthermore, it was demonstrated that either acidifying the diet to pH 4.6 by an inorganic acid such as HCl or the provision of a dietary acidifier such as citric acid or acetic acid could enhance growth, feed efficiency and survival of the Nile tilapia.The IJA is a peer-reviewed open-access, electronic journal, freely available without charge to users -Produced by the AquacultureHub non-profit Foundation Sale of IJA papers is strictly forbidden 2 Fabay et al.