No abstract

This study measures the effect of protein and lipid levels in broodstock diet on the quality of juvenile Cherax quadricarinatus. Diets with different contents of crude protein (180, 250, 310, 370 g kg−1) and lipids (30 and 70 g kg−1) were offered to female crayfish. Juveniles were used to assess initial weight (IW), biochemical composition (BC) and survival to stress tests (ST). After 50 days, growth was estimated. No significant effects of broodstock diet on IW and BC of juveniles were detected. Protein content (PC) significantly influenced growth (P < 0.05), with an optimum level of 250 g kg−1, representing a weight gain of 1.17 g (98.08% body weight). PC significantly influenced survival of juveniles exposed to ST (P < 0.05). Results from fitting dose–response models indicated that maximum survival was obtained with PC above 261, 258 and 312 g kg−1 for hypoxia, salinity, ammonia tests. No significant effect of dietary lipid level was observed on growth and survival to ST, except for greater survival to ammonia ST at lipid content of 70 g kg−1. We recommend feed with PC of 260 g kg−1 to simultaneously enhance growth and quality of juveniles.

-In this work, we studied the digestibility, growth, blood chemistry, and enzyme activity of Nile tilapia (Oreochromis niloticus) juveniles (0.95±0.18 g) using different animal (fish silage meal, whey meal, bovine blood meal, and red crab meal) and plant (extruded bean, extruded chickpea meal, coconut paste, Jatropha curcas meal, and chickpea meal) dietary byproducts. Nine isocaloric diets (321.92±9.10 kcal g −1 ) were evaluated for 60 days. The highest digestibility of crude protein values for animal and plant sources were obtained for the whey (93.6) and extruded bean meal (90.5) diets, respectively. The final body weight was higher for the red crab and extruded chickpea meal diets, meanwhile the fish silage and red crab byproducts obtained the highest protein efficiency ratio. Hematocrit was similar among the diets of each byproduct source and presented correlation with growth parameters. The highest glucose, cholesterol, and triglyceride values were obtained for fish silage (138.0, 260.5, and 389.0 mg dL −1 , respectively) and whey meal (174.5, 242.3, and 284.0 mg dL −1 , respectively) groups. A positive correlation was found between the digestibility of crude protein of ingredients and chymotrypsin activity. Oreochromis niloticus is able to better utilize fish silage, whey, extruded bean, and extruded chickpea byproducts, adjusting its digestive physiology. Such ingredients can be used for formulating cheaper and efficient tilapia diets.Key Words: alternative byproducts, digestive response, formulated diets, growth performance, Nile tilapia, physiology Revista Brasileira de Zootecnia

-The objective of our study was to assess the apparent digestibility of plant ingredients in diets for juvenile (50 g) and adult (220 g) Nile tilapia (Oreochromis niloticus). Dietary dry matter and protein apparent digestibility coefficients of four plant-derived feedstuffs (chickpea, maize, high-quality maize protein, and beans) were tested. The beans diet had the lowest apparent digestibility coefficient of dry matter (ADC DM ) (69.41%), while no significant differences were detected in ADC DM among the other diets; ADC DM was significantly higher in adults compared with juveniles (77.02 vs. 73.76%). Apparent dry matter digestibility coefficient of ingredients (ADC I ) was significantly higher in the chickpea (70.48%) and high-quality protein maize (71.09%) ingredients, and lower in the beans (52.79%) ingredient. Apparent dry matter digestibility coefficient of ingredients was significantly higher in juveniles compared with adults (72.56 vs. 56.80%). The protein digestibility of diet (ADC CP ) was significantly higher in the reference diet (93.68%), while the lowest corresponded to the maize (87.86%) and beans (87.29%) diets. Significantly lower apparent digestibility coefficient of protein (ADC ICP ) was obtained with the highquality maize protein (59.11%) and maize (49.48%) ingredients, while higher ADC ICP was obtained with the chickpea and beans ingredients (71.31 and 63.89%, respectively). The apparent digestibility coefficient of ingredient crude protein ADC ICP was significantly higher in juveniles compared with adults (67.35 vs. 53.46). Digestibility is generally higher in juveniles, and we recommend using chickpea as an ingredient in diets for Nile tilapia.

No abstract

In recent years, the application of silver nanoparticles (AgNPs) as antibacterial compounds has been widely used in human and veterinary medicine. In this work, we investigated the effects of AgNPs (Argovit-4®) as feed additives (feed-AgNPs) on shrimp (Litopenaeus vannamei) using three different methods: 1) chronic toxicity after 28 days of feeding, 2) Effects against white spot syndrome virus (WSSV) challenged by oral route, and 3) transcriptional responses of immune-related genes (PAP, ProPO, CTL-3, Crustin, PEN3, and PEN4) following WSSV infection. The results showed that the feed-AgNPs did not interfere with the growth and survival of shrimp. Also, mild lesions in the hepatopancreas were recorded, proportional to the frequency of the feed-AgNP supply. Challenge test versus WSSV showed that feeding every 7 days with feed-AgNPs reduced mortality, reaching a survival rate of 53%, compared to the survival rates observed in groups fed every 4 days, daily and control groups of feed-AgNPs for the 30%, 10%, and 7% groups, respectively. Feed-AgNPs negatively regulated the expression of PAP, ProPO, and Crustin genes after 28 days of treatment and altered the transcriptional responses of PAP, ProPO, CTL-3, and Crustin after WSSV exposure. The results showed that weekly feeding-AgNPs could partially prevent WSSV infection in shrimp culture. However, whether or not transcriptional responses against pathogens are advantageous remains to be elucidated.

The trypsin enzyme of white shrimp Penaeus vannamei is a polymorphic molecule, which longest isolated and sequenced cDNA encoded a pre-proenzyme of 255 amino acids. Three of the described sequences are translated in the digestive gland, and SDS-PAGE detects the isoforms. The three isoforms named C, B and A are distributed by an individual to originate three trypsin phenotypes (CBA, CB and CA) that have already been isolated and characterized by defining theirs biochemical and kinetical differences. The CBA phenotypes exerted higher hydrolytic capabilities than the others. The trypsin phenotypes are inherited in a Mendelian fashion, and external or internal factors do not modulate them. In commercial hatcheries in Sinaloa, México, the most abundant phenotype was CBA, followed by CB and CA. The following two hypotheses may explain this finding: phenotype CA is not chosen throughout the selection process of breeders because they do not fit the anatomical characteristics desired by professionals in aquaculture or it is possible that shrimps with the CA phenotype die during the early stages of development. Two experimental designs were developed trying to explain such hypotheses and, in both experiments, CA phenotype frequency declined to zero when shrimps reached around 5 g of body weight. So far, no evidence explains the mortality of juvenile shrimps with phenotype CA. Research is needed to explain why CA phenotypes disappeared, how the survival of this phenotype can be improved, and how to produce shrimps with the most hydrolytic capability in support of the shrimp aquaculture industry.