María Teresa Viana

Diet development for juvenile abalone Haliotis fulgens Evaluation of two artificial diets and macroalgae

Abstract Two artificial diets made with local ingredients, fish meal (FM) and casein meal (CM), proved to give better growth than that obtained with macroalgae (MA), the natural food of Haliotis fulgens , a native abalone from the northern coast of Mexico. The experiment was conducted on triplicate groups, each consisting of 20 abalone. The duration of the study was 90 days. Diets were offered as dry pellets of 2 cm 2 . The growth pattern was very similar for both treatments fed artificial diets (FM and CM), and the highest growth rate was during the first weeks, decreasing gradually thereafter. The abalone fed with FM showed the highest growth rate, being 101 μ m per day. The rate at the end of the experiment was 13.5 μ m per day. For the CM the daily growth rate decreased from 98 to 17 μ m per day. With MA, the growth rate decreased from 25 to 17 μ m per day. The decrease in growth rate may be due to several factors.

The use of silage made from fish and abalone viscera as an ingredient in abalone feed

Abstract Silage prepared from fish and abalone viscera are effective dietary protein sources for the juvenile abalone, Haliotis fulgens . Significantly higher growth rates occurred when abalone were fed artificial diets containing heated fish silage (53 μm day −1 ) and unheated fish silage (61 μm day −1 ) as a protein source compared with the kelp, Macrocystis pyrifera (1.5 μm day −1 ). However, no differences were found between diets containing heated and unheated fish silage at 30% protein inclusion, suggesting that the degree of hydrolysis did not affect protein utilization by abalone. Similar results were obtained when abalone viscera silage was used (50 μm day −1 ), producing faster growth rates than kelp (18 μm day −1 ) or kelp meal (12 μm day −1 ). In the same experiment a significant increase in growth rate was observed when abalone with low growth rates, resulting from feeding on kelp and kelp meal, were switched to a diet containing abalone viscera silage. These animals exhibited higher growth rates (135 and 167 μm day −1 ) than animals fed this diet throughout the trial (122 μm day −1 ), suggesting the presence of compensatory growth of organisms.

Effect of dietary protein:energy ratio on intake, growth and metabolism of juvenile green abalone Haliotis fulgens

Abstract Juvenile green abalone Haliotis rufescens were grown under laboratory conditions at 21±1 °C and fed formulated diets consisting of different protein:energy ratios (mg protein/kcal), 62, 74, 85, 100, 108, for 60 days. The level of crude protein ranged from approximately 26% to 44% while the energy content remained constant at about 4.1 kcal g −1 . Growth ranged from 3.63 to 12.33 mg day −1 . The growth of abalone fed the 100 and 108 diets was significantly greater than that of each of the other diets. Protein efficiency ratio increased as the dietary protein content increased except for the T108 diet (44% crude protein). Abalone apparently consume food to satisfy an energy requirement. Caloric expenditure due to metabolism was estimated for abalone fed diets with protein ratios of 62, 85, 100. Energy loss due to respiration did not vary appreciably among abalone fed the different diets. The proportional distribution of dietary energy into fecal, digestible, growth, and metabolic energy was estimated for abalone fed these diets. Apparent dry matter digestibility was among the lowest for abalone fed the 100 P:E diet, but growth of abalone fed this diet was significantly higher than that of each of the other treatments except the 108 diet. Unexplained energy loss to achieve balance ranged from 7% to 28.5%, some of which is probably due to differential mucus and ammonia production. Results suggest a potential for the reduction of both dietary protein and lipid without causing any adverse effects on the growth response.

Effect of triacylglycerols in formulated diets on growth and fatty acid composition in tissue of green abalone (Haliotis fulgens)

Abstract Isocaloric formulated diets containing four different sources of triacylglycerols (olive, corn, linseed and cod liver oils) at three levels (1.5%, 3.0% and 5.0%, total added dietary lipid=5.0%) and a crude protein content of 37.5% to 39.9% were fed to juvenile green abalone ( Haliotis fulgens ). Growth and fatty acid composition of the muscle tissue were compared to that of abalone fed a reference diet that contained no added lipids (0.25% total lipids). After 75 days of culture in a flow-through system, no significant differences in growth were found among abalone fed the different oil types. Responses to different dietary levels of lipid were significantly different but not to sources of oils. Maximum growth was achieved at a 1.5% inclusion of oil sources. It appears that abalone have a great capacity to synthesize lipid from carbohydrate sources. Results also suggest that abalone are capable of desaturation and elongation of 18 C polyunsaturated fatty acids (PUFAs) of the n −3 and n −6 family to 20:5 n −3 and 20:4 n −6. Synthesis of 22:6 n −3 from 20:5 n −3 is not reflected in the results. The lack of a growth response to the different levels of highly unsaturated fatty acids (HUFA) provided by the different oils included in the experimental diets may be due to an insufficient duration of the experiment to achieve an essential fatty acid deficiency. The relationship between fatty acid profiles of tissue and the diets fed to the abalone suggests that metabolic activity of the gut microflora is not a source of essential fatty acids.

Growth of abalone Haliotis fulgens fed diets with and without fish meal, compared to a commercial diet

Abstract In the present work, it was demonstrated that abalone viscera silage and soybean meal can be used to replace fish meal in diets for abalone without any significant difference in growth. Feeding a diet containing abalone viscera silage as the main protein source, soybean meal, corn meal, kelp meal and cellulose resulted in good growth. Abalone fed a commercial diet showed a better feed conversion efficiency (FCE). However, the experimental diet with abalone viscera silage gave higher feed consumption resulting in better growth. The dry matter loss from the pellets was highest in pellets containing abalone viscera silage (24.0%), whereas the commercial diet showed the best water stability (10.3%) followed by the fish meal diet (13.5%). Therefore, it will be necessary to achieve better water stability for the abalone viscera silage diet in order to avoid water quality problems at commercial scale.

Partial characterization of the digestive enzymes of Pacific bluefin tuna Thunnus orientalis under culture conditions

The digestive enzyme activities of Pacific bluefin tuna Thunnus orientalis were evaluated for specific activity and characterized for pH and temperature optima in crude extracts of stomach, caecal mass, and proximal, middle and distal intestine. A higher level of alkaline proteolytic activity was detected in the caecal mass than in the proximal intestine. Total alkaline proteases, trypsin, chymotrypsin and leucine aminopeptidase (LAP) were tested. The temperature and pH analyses showed that proteolytic activity as well as lipase were maximal in the alkaline range, with a maximum at pH 9.0 and at temperatures between 35 and 60°C, except for the pepsin, which showed maximum activity at the same temperatures but in the acid range (pH 3.0). The α-amylase activity showed a broader range in activity, both for pH and temperature, with higher activity over the alkaline pH values and higher temperature. The lipase activity seems to be nondependent on bile salts under our assay conditions, resulting in a significant activity reduction in the presence of bile salts. This knowledge will allow the development of a gastrointestinal model (everted intestine) where food or feed will be hydrolysed with the fish’s own enzymes, a project that is being undertaken in our laboratory as a contribution to the development of novel diets for tuna fish.

Laccase-mediated transformations of endocrine disrupting chemicals abolish binding affinities to estrogen receptors and their estrogenic activity in zebrafish.

Endocrine disrupting chemicals (EDCs) are known to mainly affect aquatic organisms, producing negative effects in aquaculture. Transformation of the estrogenic compounds 17β-estradiol (E2), bisphenol-A (BPA), nonylphenol (NP), and triclosan (TCS) by laccase of Coriolopsis gallica was studied. Laccase is able to efficiently transform them into polymers. The estrogenic activity of the EDCs and their laccase transformation products was evaluated in vitro as their affinity for the human estrogen receptor alpha (hERα) and for the ligand binding domain of zebrafish (Danio rerio) estrogen receptor alpha (zfERαLBD). E2, BPA, NP, and TCS showed higher affinity for the zfERαLBD than for hERα. After laccase treatment, no affinity was found, except a marginal affinity of E2 products for the zfERαLBD. Endocrine disruption studies in vivo on zebrafish were performed using the induction of vitellogenin 1 as a biomarker (VTG1 mRNA levels). The use of enzymatic bioreactors, containing immobilized laccase, efficiently eliminates the endocrine activity of BPA and TCS, and significantly reduces the effects of E2. The potential use of enzymatic reactors to eliminate the endocrine activity of EDCs in supply water for aquaculture is discussed.

Methods of measuring feed digestibility in the green abalone (Haliotis fulgens)

Abstract Various methods of calculating feed digestibility in the green abalone were compared. The total fecal collection technique was evaluated by comparing it with two different marker methods, one external (chromic oxide) and one internal (acid-insoluble ash). To obtain this information, a funnel-shaped digestibility chamber was designed. All the chambers (experimental units) were suspended in a square tank (200-l capacity) containing aerated seawater and with airflow and temperature kept constant (0.5 l/min, 19±0.5 °C). Two abalone (2 years old; 4.8±0.69 cm; 14.1±6.04 g) were placed in each chamber. All animals were fed daily with a similar diet containing 1% chromic oxide. After 1 week of acclimatization to the chambers and the experimental diet, feces were collected for the next 45 days to ensure that there were sufficient samples to perform all the evaluations. The results showed that the digestibility coefficients obtained with total collection and with acid-insoluble ash marker were similar (80.5±2.73% vs. 84.4±5.21%, respectively), whereas using a chromic oxide marker produced a significantly lower value (61.7±2.0%). The advantages and disadvantages of each technique are discussed. We also suggest some modifications to enable the acid-insoluble ash method to be run using a smaller sample size (200 mg).

Effect of broccoli (Brassica oleracea) and its phytochemical sulforaphane in balanced diets on the detoxification enzymes levels of tilapia (Oreochromis niloticus) exposed to a carcinogenic and mutagenic pollutant

Tilapia fish (Oreochromis niloticus) were fed with enriched diets containing broccoli and its phytochemical sulforaphane over 30 d. The levels of cytochrome P450, superoxide dismutase, catalase, lipid peroxidation and glutathione-S-transferase activities were measured. Basal value of cytochrome P450 activity was significantly increased as consequence of the broccoli and sulforaphane enriched diets, while no statistically significant changes were found on catalase and lipid peroxidation activities. After benzo(a)pyrene exposure, the cytochrome P450 activity increased to higher levels in the fish feed with broccoli and sulforaphane when compared with the control fish. Activities of antioxidant enzymes also varied but without significant difference with the control fish. Supported by the lower concentrations of BaP metabolites in bile from fish fed with broccoli or with sulforaphane enriched diets (indicating a better xenobiotic elimination) the cytochrome P450 induction could be considered beneficial for the detoxification because this transformation is the first step for PAH elimination by the phase II system. The protection of aquaculture organism against pollution effects by designing special diets able to modulate the enzymes involved in the phase-I and phase-II detoxification mechanism are discussed.

Effect of pH, water stability and toughness of artificial diets on the palatability for juvenile abalone Haliotis fulgens

An artificial diet containing abalone silage and other ingredients was adjusted to different pH values (pH 4, 5, 6, 7 and 8) to evaluate the effect of dietary pH on palatability for juvenile abalone. The pelleted diets were offered to abalone for 12h periods. Maximum food intake was observed for diets adjusted to pH 6 and 8, which also were the toughest, with high water stability (low percentage of dry matter loss). The lowest intake was observed for the pH 5 diet, which had the lowest water stability. A forward stepwise regression procedure showed that food intake can be predicted from a linear combination of toughness (P < 0.05), whereas pH and water stability did not significantly add to the ability of the equation to predict food intake. It is concluded that pH alone did not affect abalone food intake. However, pH may have had an indirect influence on the diets, owing to toughness and other possible masked factors. Thus, one may be able to reduce production costs and avoid feed spoilage by using feeds with a low pH, as long as they have higher pellet toughness.