Now showing items 1-5 of 5

    • Article

      Controlled release of testosterone and estradiol-17 β from biodegradable cylinders 

      X Zhang, UP Wyss, D Pichora, MFA Goosen, A Gonzal & CL Marte - Journal of Controlled Release, 1994 - Controlled Release Society
      A controlled release device for the hormones, testosterone and estradiol-17 β, was developed by coating a melt extruded hormone/poly (ϵ-caprolactone) cylinder with pure polylactide. Since testosterone and estradiol-17β have much higher permeabilities in poly (ϵ-caprolactone) than in polylactide, they primarily permeate through the open ends of the cylinder, with little release through the polylactide wall. By changing the cylinder length, the release rate and duration could be adjusted. The release followed Pick's diffusion equation for a drug loading below its solubility in poly (ϵ-caprolactone) or Higuchi's equation for a drug loading above the solubility. The diffusion coefficients of testosterone and estradiol-17β in poly (ϵ-caprolactone) were estimated as (8.31 ±3.12) × 10−18 and (0.728 ± 0.250) × 10−18 cm2/s, respectively.
    • Article

      Effect of prepared diet and vitamins A, E and C supplementation on the reproductive performance of cage-reared bighead carp Aristichthys nobilis (Richardson) 

      CB Santiago & AC Gonzal - Journal of Applied Ichthyology, 2000 - Blackwell Publishing
      Twenty-month-old bighead carp, Aristichthys nobilis (Richardson), were fed prepared dry diets for 20 months in cages in Laguna de Bay, Philippines, to determine the effect on reproductive performance. The experimental diets were similar in composition except for the combinations of vitamins being tested. Diet 1 was supplemented with vitamins A, E and C; diets 2, 3 and 4 each lacked one of the supplementary vitamins; and diet 5 did not include any vitamin supplementation. Bighead carp that relied solely on natural food without a prepared diet served as a control. The total of six treatments each had two replicates. Results showed that the onset of gonad maturation was 2–3 months earlier in the fish that were fed the prepared diets regardless of vitamin supplementation, when compared with the fish that were fed natural food (control). Moreover, the prepared diets enhanced egg hatchability which was significantly higher in fish that were fed diet 1 (+ vitamins A, E and C, 80.5 ± 18.1%) and diet 3 (– vitamin E, 78.5 ± 1.1%) than in those fish that were fed natural food (control) (36.5 ± 31.3%). Mean number of 3-day-old larvae was highest in fish fed on diet 1 (34 525 ± 1732), followed closely by fish that were fed diet 3 (32 420 ± 3909). A low number of 3-day-old larvae was obtained from fish fed the natural diet (14 490 ± 4331) as well as in fish that were fed diet 2 (– vitamin A, 14 347 ± 4863), diet 4 (– vitamin C, 21 407 ± 5840) and diet 5 (– vitamin A, E and C, 12 191 ± 1439). Other criteria for reproduction such as relative fecundity, fertilization rate, and hatching rate did not differ significantly (P > 0.05) among treatments. The addition of vitamins also had no significant effects on weight gain of adult fish.
    • Article

      Growth and reproductive performance of the Asian catfish Clarias macrocephalus (Gunther) fed artificial diets 

      CB Santiago & AC Gonzal - Journal of Applied Ichthyology, 1997 - Blackwell Publishing
      Four natural ingredient diets similar in nutrient composition (crude protein = 42–44%; P/E ratio = 115–120 mg/kcal) but different in protein sources, were formulated and fed to hatchery-reared catfish to measure the relative performance of the catfish fed alternative broodstock diets. The control feed was a combination of fish-by-catch and commercial fish pellets. In trial I, growth of the catfish was slow over a 36-week period, but some fish became gravid. Diets 1, 2, and 3 and the control feed were tested in trial II. Growth of fish did not differ significantly (P > 0.05) and female fish in all treatments became gravid. For fish induced to spawn from April to August (1994), hatching rate showed significant differences among treatments (P < 0.05). Relative fecundity, fertilization and hatching rates, and production of 3-day-old larvae were significantly different among fish induced to spawn in November (1994) when another incubation setup was used. Among the diets, diets 2 and 3 best enhanced reproductive performance of the catfish.
    • Article

      Response of bighead carp Aristichthys nobilis and Asian catfish Clarias macrocephalus larvae to free-living nematode Panagrellus redivivus as alternative feed 

      CB Santiago, AC Gonzal, M Ricci & S Harpaz - Journal of Applied Ichthyology, 2003 - Blackwell Publishing
      The use of Panagrellus redivivus as live feed for bighead carp and Asian catfish larvae was tested. In experiment 1, carp larvae were given Artemia nauplii (control) or Panagrellus twice daily for 21 days. A third treatment consisted of unfed larvae. The same three treatments were used in experiment 2 plus another with a commercial entomopathogenic nematode (EPN). Bighead carp larvae given Panagrellus in experiment 1 had much lower growth and survival than those fed Artemia nauplii. This could be due to low nematode density (5–30 mL−1 water) during feeding. The unfed larvae had 100% mortality by days 11–13. In experiment 2, growth and survival of carp larvae given Artemia nauplii (5–10 mL−1) and Panagrellus (50 mL−1) did not differ significantly (P > 0.05). All unfed larvae had died by day 13, while larvae fed EPN were all dead by day 8. Two experiments on Asian catfish were likewise conducted. In experiment 1, the catfish larvae were fed Tubifex (ad libitum), Panagrellus (50–100 mL−1 per feeding) orArtemia (5 nauplii mL−1 per feeding) three times daily for 14 days. In experiment 2, larvae were fed Artemia alone (10 nauplii mL−1 per feeding), Panagrellus alone (100 mL−1 per feeding), or their combination with a 38% protein dry diet twice daily. For both experiments, catfish larvae fed Panagrellus had significantly lower growth and survival than those fed Tubifex or Artemia. The combination of Panagrellus and dry diet created little improvement in the growth and survival of catfish larvae.
    • Article

      Survival and growth of bighead carp fry exposed to low salinities 

      LMB Garcia, CMH Garcia, AFS Pineda, EA Gammad, J Canta, SPD Simon, GV Hilomen-Garcia, AC Gonzal & CB Santiago - Aquaculture International, 1999 - Kluwer
      Bighead carp (Aristichthys nobilis Oshima) fry of various ages (11, 18, and 35 days post-hatch) were exposed to the low salinities encountered during the annual intrusion of seawater in Laguna Lake, Philippines. Practical indices of salinity tolerance assessed the effect of a 96 h direct exposure to low salinities (0–16‰). Mean (MST) and median survival times (MST50) of fry decreased as salinity of rearing medium increased. Younger fry were less able to tolerate exposure to these salinities than their older cohorts. Median lethal salinity after 96 h (MLS) revealed higher tolerance among 35–day old fry (7.6‰) than 11 (2.3‰) and 18–day old fry (6.0‰), demonstrating that survival in saline water depends on their age at initial exposure to low salinities. Mean body weight of 18–day old fry reared in 0 and 2‰ for 3 and 4 weeks was higher than for those reared in 4 and 6‰ for the same period. Growth over these periods was inversely related with the range of salinities tested. These results demonstrate that, despite their known stenohalinity, bighead carp fry possess some degree of osmoregulatory capability, allowing them to survive and grow in lakes subjected periodically to saltwater inflow.