Lus M. López

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 fishmeal replacement by soy protein concentrate with taurine supplementation on hepatic intermediary metabolism and antioxidant status of totoaba juveniles (Totoaba macdonaldi).

The effect of dietary incorporation of soy protein concentrate (SPC) and the concomitant supplementation with taurine on hepatic intermediary metabolism and antioxidant status of totoaba (Totoaba macdonaldi) juveniles was assessed. Four isoproteic and isolipidic diets were formulated containing either 30 or 60% of SPC (diets SP30 and SP60), supplemented or not with 1% of taurine (diets SP30T and SP60T). A fish meal (FM) based diet, without SPC and taurine supplementation, was used as a control. Triplicate groups of 32 totoaba juveniles (average body mass=7.5g) were fed these diets over 45days. Results revealed that dietary FM replacement by SPC depressed the overall intermediary metabolism. Activity of key enzymes of amino acid catabolism and gluconeogenesis was significantly reduced and a trend to reduce glycolysis and glucose-6-phosphate dehydrogenase activity was observed. The incorporation of the highest level of SPC also significantly increased hepatic lipid peroxidation and the activity of superoxide dismutase. Concomitant taurine supplementation restored the activity of amino acid catabolic and gluconeogenic enzymes and hexokinase to levels similar of those of the control diet. Taurine supplementation also led to a significant increase of glucose-6-phosphate dehydrogenase and catalase activity, as well as to a significant reduction of liver lipid peroxidation. These results suggest that taurine may play an important metabolic modulation action on totoaba fed SPC based diets, contributing to the enhancement of the overall metabolism and to the reduction of liver oxidative damage.

Expression and activity of trypsin and pepsin during larval development of the spotted rose snapper Lutjanus guttatus

The present study aimed to describe and understand the development of the digestive system in spotted rose snapper (Lutjanus guttatus) larvae from hatching to 40 days post-hatch (dph). The mouth opened between 2 and 3 dph, at that moment the digestive tract was barely differentiated into the anterior and posterior intestine, although the liver and pancreas were already present. Gastric glands were observed until 20 dph, followed by the differentiation of the stomach between 20 and 25 dph. Trypsinogen expression and trypsin activity were detected at hatching, increasing concomitantly to larval development and the change in the type of food. Maximum levels of trypsinogen expression were observed at 25 dph, when animals were fed with Artemia nauplii, and maximum trypsin activity was detected at 35 dph, when larvae were fed with an artificial diet. On the other hand, pepsinogen gene expression was detected at 18 dph, two days before pepsin enzymatic activity and appearance of gastric glands. Maximum pepsin activity was also observed at 35 dph. These results suggest that in this species weaning could be initiated at an earlier age than is currently practiced (between 28 and 30 dph), since larvae of spotted rose snapper develop a functional stomach between days 20 and 25 post-hatch.

Determinación de la calidad del alimento elaboradocon ensilajes de pescado crudo y cocido,para abulones juveniles de haliotis fulgens

The quality of two artificial diets for the abalone Haliotis fulgens were evaluated through protein leaching, stability analysis, consumption and feed conversion efticiency. The two diets were elaborated from unheated and heated tish silage (greater and lesser grade of hydrolysis, respectively). The results suggested that unheated silage was more stable, but it showed more protein leaching due to its higher water soluble protein. No significant differences were found (P > 0.05) between both treatments. Maximum eftkiencies of 1: 1.6 and 1: 1.1 were obtained for both the unheated and heated silage, respectively.

Functional Feeds in Aquaculture

The development of functional feed (FF) represents a great opportunity in the aquaculture industry. FF must promote the growth and health of cultivated organisms, improve their immune systems, and induce physiological benefits beyond traditional feeds. FF must be economically attractive and environmentally friendly. In this sense, the inclusion of animal products in FF formulations must be partially or totally eliminated, increasing the inclusion of alternative economical vegetable products. However, the kind and amount of vegetable protein, carbohydrates (CHO ), and lipids added to formulations are of great concern for growth, health, environmental, and economical issues. Therefore, deficiencies in proteases, carbohydrolases, and lipases in shrimp/fish are a major impediment to the digestion and assimilation of vegetable sources, limiting its high-level inclusion in formulations. In this sense, the utilization of probiotic bacteria has emerged as a solution with huge applications in the aquaculture industry. Today, Bacillus species are the most investigated bacteria for animal probiotic development due to: a) The versatility of their growth nutrients b) High level of enzyme production c) Secretion of antimicrobial compounds.