Growth, nutrient utilization and body composition of juvenile bagrid catfish, Chrysichthys nigrodigitatus (Actinopterygii: Siluriformes: Claroteidae), fed different dietary crude protein levels

Background. The African bagrid catfish, Chrysichthys nigrodigitatus (Lacepède, 1803), is an omnivorous species cultured in both fresh and brackish waters because of its good growth rate, excellent taste, and high market demand. There has been little nutritional work on this economically important species. This study was designed to determine the effects of varying dietary crude protein levels on growth, nutrient utilization and body composition of juvenile C. nigrodigitatus. Materials and methods. One hundred and twenty fish with an initial mean weight of 21.33 ± 0.48 g were divided randomly among 12 tanks for triplicate groups that were fed diets containing 20%, 25%, 30%, and 35% crude protein (CP). Feed consumption and fish weight were measured biweekly for eight weeks, after which proximate composition of the fish was determined. Results. Fish fed the 35% CP diet had the best growth performance and nutrient utilization (P < 0.05), with a mean weight gain of 88.3% ± 0.2%, feed conversion ratio (FCR) of 2.60 ± 0.12, and protein efficiency ratio (PER) of 1.10 ± 0.05. The least weight gain (32.1% ± 0.9%) and poorest FCR and PER (5.70 ± 0.06 and 0.87 ± 0.01, respectively) were observed in fish fed the 20% CP diet. Body protein content was not affected by diet, but body lipid increased significantly (P < 0.05) with increasing dietary protein levels. Conclusion. C. nigrodigitatus juveniles will grow best when fed diets containing at least 35% CP

Gonadal Morphology of Normal and Sex-Reversed Triploid and Gynogenetic Diploid Coho Salmon (Oncorhynchus kisutch)

13 pagesIn this study, the gonadal morphology of untreated and sex-reversed juvenile triploid and gynogenetic diploid coho salmon was compared with that of diploids. Testes of triploids were of the same size as those of diploids. Spermatogonia, however, were significantly bigger than those of diptoids in both diameter (P<0·001) and volume (P<0·01), suggesting that this characteristic can be a useful indicator of ploidy in the early stages of gonadal development. In females, induction of triploidy did not affect the lamellar structure of the ovaries but reduced their size considerably. Further, these ovaries had no oocytes. Treatment of triploids with oestrogen resulted in the feminization of genotypic males, which had ovaries similar to those found in tripioid females. However, gonads of triploid males partially sex-re versed into females were identified by their enlargement, the presence of remnants of the male vascular system, and by the appearance of ovarian lacunae and germinal and somatic cells typical of triploid females, Induction of gynogenesis resulted in 100% females, of which 34% had ovaries of reduced size with areas devoid of oocytes. However, and contrary to what has been found in cyprinids, no male germ cells were observed in these ovaries. This discrepancy may reflect differences, in the mechanisms of sex determination between salmonids and cyprinids. Treatment of gynogenetics with androgen increased the number of fish with abnormal ovaries but also resulted in the production of phenotypic-male gynogenetic diploids, of which 11% had testes indistinguishable from those of untreated control diploid

Production de femelles triploïdes de saumon coho (Oncorhynchus kisutch) au moyen de chocs de pression et de traitement direct d'estrogène

5 pages, 1 figure, 1 table[EN] The aquaculture production of all-female triploid (sterile) populations is recognized as being of potential advantage for many species of fish where sexual maturation is not desired. All-female triploids have been produced by inducing triploidy in eggs that had been fertilized with monosex female sperm. However, monosex stocks to produce this type of sperm are currently available only for a limited number of economically important species. To circumvent this problem, an alternative method would be the direct fertilization of tripoid embryos. In Pacific salmon, pressure shocks applied shortly after fertilization have consistently resulted in high yields of tripoids, and feminization by direct estrogen treatment has also been shown to be highly effective if applied shortly after hatching. In this study, coho salmon eggs were made triploid by a pressure shock of 633 kg/cm2 for 4 min, applied 20 min after fertilization and incubation at 10 °C. Some of the resulting embryos were then feminized with estradiol-17β in single 2-hour immersion treatments at 400 μg/liter, administered 1 and 8 days after hatching. Six months later, when the fish were juveniles, analysis of the DNA content of erythrocytes by flow cytometry revealed a 100% induction of triploidy, while histological examination of the gonads showed 82% females, which were completely devoid of oocyte development and thus genetically sterile. These manipulations reduced survival during early stages of development but survival became stable later. Together, these results suggest that the production of sterile fish by direct feminization of induced triploids could be of particular advantage for those species in which all-female stocks are yet not available or difficult to obtain[FR] La production aquacole de populations monosexes femelles et triploïdes (stériles) est reconnue comme étant un avantage potentiel pour de nombreuses espèces où la maturation sexuelle n'est pas désirée. Les triploïdes monosexes femelles étaient produites en induisant la triploïdie dans les oeufs qui avaient été fertilisés avec du sperme de femelles monosexes. Cependant, des stocks de monosexes pour produire ce type de sperme ne sont disponibles que pour un nombre limité d'espèces importantes économiquement. La féminisation d'embryons triploïdes permettrait de résoudre cette question. Chez le saumon du Pacifique, des chocs de pression appliqués peu après la fertilisation donnent des résultats satisfaisants pour des rendements importants de triploïdes; la féminisation par traitement aux estrogènes est également très efficace s'il est appliqué dès l'éclosion. Dans cette étude, les oeufs de saumon coho sont devenus triploïdes par un choc de pression de 633 kg/cm2 pendant 4 min, appliqué 20 min après la fertilisation et l'incubation à 10 °C. Certains embryons ainsi obtenus ont ensuite été féminisés par traitement à l'estradiol-17β à raison d'une seule immersion dans une solution à 400 μg/litre, administré 1 et 8 jours après l'éclosion. Six mois plus tard, chez les juvéniles, l'analyse de l'ADN des érythrocytes par cytométrie de flux révèle 100 % de triploïde induite, tandis que l'examen cytologique des gonades montre 82 % de femelles, mais sans développement ovocytaire et donc génétiquement stériles. Ces manipulations réduisent le taux de survie durant les premiers stages de développement qui devient stable plus tar

The effect of dietary energy level on growth and nutrient utilization by juvenile diploid and triploid brook charr, Salvelinus fontinalis

Triploids are used in aquaculture because they are sterile and do not undergo preharvest loss in flesh quality. Despite this advantage, they do not always perform as well as diploids when fed commercial diets. This study investigated whether differences in dietary energy utilization might explain this reduced performance. Dietary lipid levels were adjusted to supply diets with 22.7, 23.6 or 24.4 MJ kg-1 gross energy and fed to juvenile diploid and triploid brook charr. Fish were fed to satiation twice daily in a 70-day growth trial, with samples collected at days 0 and 70 for proximate composition and plasma insulin-like growth factor I (IGF-I) analysis. This was followed by a digestibility trial using the same diets to determine apparent digestibility coefficients. Triploids had lower growth rates and condition factor than diploids on all three diets, but there was no effect of ploidy on feed conversion efficiency. Triploids also had lower whole-body lipid content, but equal protein content, which resulted in lower energy content at both days 0 and 70. There was no effect of diet or ploidy on plasma IGF-I concentrations. Triploidy did not affect diet digestibility, suggesting that the reduced performance of triploids is due to a difference in metabolism and energy utilization. \ua9 2015 John Wiley & Sons Ltd.Peer reviewed: YesNRC publication: Ye