Harry Ako

Growth response and fatty acid composition of juvenile Penaeus vannamei fed different sources of dietary lipid

Abstract A study was conducted to evaluate the effects of feeding various sources of dietary lipid on weight gain, feed conversion, survival and fatty acid composition of juvenile Penaeus vannamei . Seven semi-purified diets (35% protein and 3400 kcal of metabolizable energy kg −1 ) containing defatted, freeze-dried shrimp meal, 1.0% soybean lecithin and 0.5% cholesterol were supplemented with 6.5% of either stearic acid, coconut, safflower, corn, soybean, linseed or menhaden fish oils. Each diet was fed to shrimp (1.00 ± 0.03 g average weight) in four replicate aquaria four times daily for 10 weeks. Weight gain, feed conversion and survival were best for shrimp fed the diet containing menhaden fish oil. Shrimp fed the linseed oil diet had the second highest weight gain, followed by shrimp on soybean oil, corn oil, stearic acid, coconut oil and safflower oil diets, respectively. Feed conversion values were a reflection of weight gain. Results of this study show that both n -6 and n -3 fatty acids are dietary essential for juvenile Penaeus vannamei , although n -3 fatty acids promoted faster growth than n -6. However, highly unsaturated fatty acids (HUFA) (20:5 n -3 and 22:6 n -3) had better growth-promoting effect than 18:3 n -3, due probably to the limited ability of shrimp to bioconvert fatty acids to polyenoic forms of longer chain length. The fatty acid composition of the shrimp generally reflected that of the dietary lipids, especially for the diets containing unsaturated fatty acids. Shrimp fed stearic acid and coconut oil diets low in polyunsaturated fatty acids accumulated high levels of 16:1 n -7 and 18:1 n -9.

Fatty acid and amino acid profiles of spawned eggs of striped mullet, Mugil cephalus L.

Abstract Striped mullet, Mugil cephalus , females were matured in a variety of facilities (i.e., outdoor ponds with seawater or brackishwater, and indoor seawater tanks). Hormonally induced spawnings ( n = 29) resulted in no significant difference in the average spawned egg diameters and fecundity per spawn from females maturing in the various maturation facilities. A significant difference in the percentages of fertilized eggs was obtained from females maturing in the indoor tanks resulting in the lowest average fertilization (50.0 ± 38.6%). In contrast, spawnings from females maturing in the brackishwater pond resulted in an average fertilization of 78.4 ± 28.8%. Fatty acid and amino acid profiles were obtained from the induced spawnings of the striped mullet. No detectable differences were found in the essential or nonessential amino acids and total protein of the spawned eggs. Oleic, eicosenoic, and arachidonic acids were significantly different between the spawned eggs from females maturing in the various facilities.

Growout performance of diploid and triploid Chinese catfish Clarias fuscus

Abstract Culture performance of diploid and triploid Chinese catfish Clarias fuscus was evaluated at two temperatures (21.5 and 25.0°C), and with two feed formulations. New Age Pacific (NAP) feed (49% crude protein and 18% crude lipid) and Catfish No. 2 (C2) feed (36% crude protein and 23% crude lipid) were provided once daily at 5% body weight. After 175 days, triploid fish gained more weight than diploids. Both diploids and triploids grew faster at 25°C than at 21.5°C. At the lower temperature, C2 feed enhanced fish growth compared with NAP feed in both ploidies, while triploid fish gained more weight than diploids only with C2 feed. Male C. fuscus grew faster than females regardless of ploidy. Neither fish survival nor condition factor differed among treatments, but the condition factor in diploid males was lower than others. If our results apply to commercial scale, culture of triploids at temperatures >25°C could improve total yield and profitability.

Enhancing the resistance to physical stress in larvae of Mugil cephalus by the feeding of enriched Artemia nauplii

Abstract Striped mullet, Mugil cephalus , larvae were first reared exclusively on rotifers until 15 days post-hatching. Larvae were then separated and reared until 35 days post-hatching using four different rearing strategies: Treatment 1 = newly hatched Artemia nauplii, Treatment 2 = rotifers plus nauplii, Treatment 3 = enriched nauplii, and Treatment 4 = rotifers plus enriched nauplii. No obvious differences in larval growth and survival were observed between treatments. However, significant differences in the ability to tolerate physical handling were observed. Highest mortalities occurred with larvae reared using Treatment 1. Intermediate percentages of mortality were observed from larvae grown using Treatment 2 and almost no mortalities were observed when employing enriched nauplii (i.e., Treatments 3 and 4).

Rotifers fed various diets of baker's yeast and/or Nannochloropsis oculata and their effect on the growth and survival of striped mullet (Mugil cephalus) and milkfish (Chanos chanos) larvae

Abstract The rotifer Brachionus plicatilis (S-type Hawaiian strain) was cultured with various combinations of bakers yeast and Nannochloropsis oculata . There were no significant differences in the daily rotifer production and amino acid profiles of the resulting rotifers. The significantly lower levels of fatty acids (C14, C16, C20:4 n −6, C20:5 n −3 and C22:6 n −3) observed in the rotifers were found to correspond with the amount of yeast presented in their diet. The low survival and growth of striped mullet larvae recorded at Day 15 posthatching indicates that rotifers fed only yeast were nutritionally deficient in fatty acids. The fatty acid requirements of mullet, however, appeared to be satisfied with rotifers cultured on a combination of yeast and N. oculata . In contrast, no significant differences in larval milkfish survival and growth at Day 10 posthatching were detected when using rotifers fed the various diets in the larval rearing protocol.

The utilization of blood meal as a protein ingredient in the diet of the marine shrimp Penaeus vannamei

Abstract Four blood meal products were compared and tested as protein substitutes for a marine protein mix in grow-out rations for the marine shrimp Penaeus vannamei. The blood meal products tested were a ring-dried blood meal (RD), an acidulated, sun-dried blood meal (AS), an acidulated, sundried blood meal with crystalline methionine added (ASAM), and an acidulated, sun-dried blood meal with covalently linked methionine (ASCM). There were no significant differences in weight gain (0.62–0.75 g per week), survival (96.8–100%), or feed conversion ratios (1.6–2.0) during the 42-day trial. The AS and ASAM blood meal diets produced significantly (P 0.05) from the control diet. The results suggest that blood meal products can replace marine proteins in grow-out rations for medium sized (3–4 g) Penaeus vannamei. Results also indicate that the blood meal product containing covalently attached methionine may be a potentially useful way to supplement limiting amino acids in shrimp diets.

Chemical and physical differences in milkfish (Chanos chanos) eggs from natural and hormonally induced spawns

Fatty acid and amino acid analyses were performed on milkfish eggs from natural (n = 8) and hormonally induced (n = 12) spawns. No significant differences were observed in amounts of 18:1n−9, 18:3n−3, 22:1n−11, and 22:6n−3 in eggs. However, all other fatty acids were significantly higher in naturally spawned eggs. No significant differences were observed in non-essential amino acids between eggs from natural and hormonally induced spawns; however, the majority of essential amino acids were found to be significantly higher in naturally spawned eggs. The mean egg diameter was significantly larger in naturally spawned eggs, while the number of eggs per spawning event was found to be significantly higher from hormonally induced spawns. Using the relationship ED = 1.069 (ID) + 0.372 (P < 0.001, r2 = 0.493), where ED = spawned egg diameter in mm and ID = initial oocyte diameter in mm, the oocyte size at which a female that will spawn naturally and initiates final maturation was estimated to be 0.849 mm. Collectively, the data indicate that the initial oocyte diameter (0.750 mm) previously used as the standard size for induced spawning of milkfish is premature.

Essential fatty acid profiles of maturation feeds used in freshwater ornamental fish culture

An investigation of live or freshly prepared feeds used as ‘maturation’ diets for freshwater ornamental fish was conducted to uncover similarities or differences in total and essential fatty acids. Analysis of these ‘maturation’ feeds reveals that there are relatively low levels of total fatty acids (0.81–8.96 mg/100 mg−1 dry weight) and with the exception of the beef heart diet all other feeds have undetectable levels of docosahexaenoate (22:6n3). The beef heart diet was observed to possess 4.86 mg 100 mg−1 dry weight of 22:6n3 most probably due to the addition of skipjack tuna, Katsuwanus pelamis, roe. All other feeds examined were found to contain low to moderate levels of eicosapentaenoate (20:5n3) 0.00–0.61 mg/100 mg-1 dry weight. Surprisingly relatively high amounts of arachidonate (20:4n6) 0.16–0.90 mg/100 mg−1 dry weight were observed in all of the maturation diets and ranged between 3.79%–27.16% on a percent composition basis. The results obtained to date indicate a need to scrutinize the role of arachidonate in the maturation and spawning process.

Inactivation of bean ornithine carbamoyltransferase by phaseotoxin: Effect of phosphate

Abstract The results of kinetic studies of the inactivation of bean ornithine carbamoyltransferase by phaseotoxin, the extracellular toxin of Pseudomonas phaseolicola , are consistant with the notion that the toxin is an active site directed irreversible inhibitor of the enzyme. Phosphate, an end product of the enzymatic reaction, protects the enzyme from inactivation by the toxin. It is proposed that phaseotoxin is one of a few naturally occurring affinity labels.

Improved isolation of a 50 kDa anorexigenic protein from rat urine

In prior work, a 50 kDa protein was purified to homogeneity from rat urine. This protein reduces food intake when injected into rats and is the only natural substance other than satietin known to be effective for long (24 hour) time periods and which does not make animals ill. However, when attempts were made to repeat the purification, contamination appeared in the 50 kDa fraction. The present contribution documents successful reisolation of the 50 kDa anorexigen by an improved method. Reisolation involved Cibacron blue-Sepharose, DEAE-Sephacel and Sephacryl S-200 chromatography, and SDS disc preparatory electrophoresis. The reisolated 50 kDa anorexigen contains no detectable carbohydrate. Partially purified preparations of the 50 kDa anorexigen were fragmented with trypsin and proteinase K without loss of anorexigenic activity. It is concluded that the 50 kDa anorexigen may be reproducibly purified to homogeneity and may contain within its amino acid sequence a peptide which is the basis of its anorexigenic activity.