Apparent digestibility of dry matter, crude protein, and amino acids of six rendered by-products in juvenile Litopenaeus vannamei

Apparent digestibility coefficients (ADC) of dry matter, crude protein (CP), and amino acids (AA) were evaluated in diets with six rendered by-products used to feed juvenile Pacific white shrimp: two poultry meals (poultry meal 1, 69% CP; poultry meal 2, 72% CP), two feather meals (89% CP), one blood meal (96% CP), and one pork meal (57% CP). Experimental diets were formulated with 30% of the test ingredient and 70% of a commercial diet supplemented with 1% of chromium oxide as inert marker. AA contents in ingredients, diets, leached diets, and feces were determined by high performance liquid chromatography. Preprandial AA losses attributed to leaching were higher in the blood meal diet (15%) and pork meal diet (10%). Poultry meal diets 1 and 2 showed mean AA losses of 3% and 5%, respectively, while the reference diet had a mean AA leaching of 6%. The AA that had the highest leaching rates were lysine (21%), methionine (15%), and histidine (12%). The ADC of dry matter was higher for poultry meals 1 (70%) and 2 (73%), followed by pork meal (69%), feather meals (61%), and blood meal (57%). The digestibility of CP was higher for poultry meals (78–80%), followed by pork meal (76%), and blood meal and feather meals (65–67%). The digestibility of CP in the reference diet (83%) was higher than that observed for all the animal by-product meals except the poultry meals. The ADC of the sum of AA adjusted for nutrient leaching fluctuated from 65% for blood meal to 80% for poultry meals.

Chemical composition of cultivated seaweed ulva clathrata (Roth) C. Agardh

Samples of cultivated Ulva clathrata were collected from a medium scale system (MSS, 1.5 1.5 m tank), or from a large scale system (LSS, 0.8 ha earthen pond). MSS samples were dried directly while the LSS sample was washed in freshwater and pressed before drying. Crude protein content ranged 20–26%, essential amino acids accounting for 32–36% of crude protein. The main analysed monosaccharides were rhamnose (36–40%), uronic acids (27–29%), xylose (10–13%) and glucose (10–16%). Some notable variations between MSS and LSS samples were observed for total dietary fibre (26% vs 41%), saturated fatty acids (31% vs 51%), PUFAS (33% vs 13%), carotenoids (358 vs 169 mg kg1 dw) and for Ca (9 vs 19 g kg1 ), Fe (0.6 vs 4.2 g kg1 ), Cu (44 vs 14 mg kg1 ), Zn (93 vs 17 mg kg1 ) and As (2 vs 9 mg kg1 ). The chemical composition of U. clathrata indicates that it has a good potential for its use in human and animal food.

Incorporation of dietary nitrogen from fish meal and pea meal ( Pisum sativum ) in muscle tissue of Pacific white shrimp ( Litopenaeus vannamei ) fed low protein compound diets

Stable isotope analyses were applied to explore the relative dietary nitrogen contributions from fish meal and pea meal (Pisum sativum) to muscle tissue of Pacific white shrimp postlarvae (141 ± 31 mg) fed low protein diets having different proportions of both ingredients as the sole dietary protein sources. A negative control diet was formulated to contain 100% pea meal and six more isoproteic diets to have decreasing levels of pea meal-derived nitrogen: 95%, 85%, 70%, 55%, 40% and 0% of the initial level. Growth rates were negatively correlated to dietary pea protein inclusion due to progressive essential amino acid deficiencies (sulphur amino acids, threonine, lysine, histidine). The nitrogen turnover rate significantly increased in muscle tissue of shrimps fed diets having high levels of pea meal; however, contrary to observations from a previous study using soy protein, the relative contributions of dietary nitrogen from pea meal to shrimp muscle tissue were equal or higher than expected contributions established by the dietary formulations. Results highlight the effectiveness of stable isotope analysis in assessing the nutritional contributions of alternative ingredients for aquaculture feeds and the potential suitability of pea as a source of protein (provided the diets are nutritionally balanced)