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Davis, Donald Allen
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Efficacy of Purified Amino Acids in Practical Diets for Pacific White Shrimp Litopenaeus vannamei
Get PDFShrimp growth and nitrogen loading is influenced by the quantity and quality of protein supplied to the diet. Protein is also the main cost component of the diet, and, therefore, feed formulations need to be cost effective. Feed formulations are moving towards using less fishmeal in diets and more plant-based protein sources, which are cheaper and more widely available. However, plant protein sources have some disadvantages and one of the major problems are unbalanced amino acid profile. To meet an amino acid requirement, a combination of different ingredients may be used, or the diet may be supplemented with crystalline amino acids (CAA). Formulations now are “nutrient-based” as shrimp have a requirement for amino acids rather than for protein which makes the determination of essential amino acid requirements important. Studies determining amino acid requirements have been variable and opinions differ on whether CAA are utilizable by shrimp due to their slow feeding habits. Other possible causes of this variation are unclear but there could be some environmental factors or differences in experimental design limitations. Lysine and methionine are often the most limiting amino acids in plant-based diets. Methionine is an amino acid that is often supplemented in shrimp diets when soybean meal is the main protein source which is known to be deficient in sulphur containing amino acids. Reported methionine requirement is quite high and studies are variable and often not repeatable. Before a methionine requirement can be determined a suitable source that produces a response needs to be identified. Consequently, the objective of the first study was to determine the efficacy of CAA in diets of Pacific White Shrimp. For this experiment, a basal diet was designed to have 30% crude protein (CP) and 6% lipid. The CP was then decreased gradually to reach 28, 26, 24 and 22% CP in the first series. In the second series of diets, CAA was supplemented back to each of the lower CP diets to reach 30% CP of the basal diet. Limited statistical differences were found but, as the CP content of the diet decreases the percentage weight gain (PWG) and mean final weight (MFW) was significantly affected. None of the diets supplemented with CAA seemed to produce the same performance as that of the 30% CP diet. A second study was then formulated to determine the effect of protein level on CAA supplementation. A fishmeal-based reference diet was formulated, as in theory, fishmeal should be replete in essential amino acids required by this species. Two soybean meal-based diets were then formulated to reach 30 and 35% CP and each supplemented with essential amino acids in one set and methionine in another to reach the same level as a percent protein as that of the fishmeal reference diet. In terms of PWG, no significant differences existed among the diets, but in terms of protein retention efficiency (PRE), the fishmeal diets produced significantly higher performance compared to most other treatments. The last study looked at the efficacy of different methionine sources when supplemented to a soybean meal basal diet. Methionine (Met) was supplemented to reach 0.60% (by using DL-Met, coated Met, peptide Met and intact protein Met) of the diet from a basal diet containing 0.45%. However, none of the supplemented sources significantly improved performance of the shrimp leading to the conclusion that methionine may actually not be deficient in a soybean diet for Pacific White Shrimp. There is a clear need to find suitable sources that can be used for determining essential amino acid requirements, which may then also be used for diet supplementation in the industry. As per overall observation during the present study, it was not clear whether purified amino acids are effective in the diets of Pacific White shrimp or if a practical diet designed to be low in methionine is actually deficient.It may be necessary to complete further research to determine what the cause may be for the poor utilization of CAA. Poor utilization is likely due to leaching but other factors such as pH of the diet, absorption from the gut and palatability may also be considered
Practical diets for Pacific white shrimp Litopenaeus vannamei utilizing alternative ingredients
Get PDFGlobal shrimp production has steadily increased and is currently one of the primary users of fishmeal (FM). At the same time, Global fishmeal supply has reached a plateau, with demand still continuing to increase resulting in reduced availability and increased prices. From an economic standpoint, it is important to look for cost -effective protein sources from a variety of plant and terrestrial animal sources as replacements for more expensive proteins such as FM. This study was dedicated to exploring the usage of alternative protein sources which included two conventional yeast products (BY50 and BY70), corn processing product (CPC: corn protein concentrate), enzyme-treated soybean meal products (SPC: soy protein concentrate), grain processing product (HPDDG: high protein distiller’s dried grain) and by-products of salmon processing (SM and HSM: salmon meal and hydrolyzed salmon meal) as potential protein source to replace FM, CPC or SBM in practical shrimp diet. A series of 5 independent trials were conducted to evaluate those listed products. The first study results indicated that 180-240g/kg BY50 can be effectively used in shrimp diets as a replacement for FM, or up to 240g/kg when replacing SBM. Additionally, adding 20g/kg of BY70 does not cause impaired growth performance for the shrimp fed with low FM diet. Under green water conditions in the presence of natural foods, the second study results indicated that HPDDG is a good protein source and up to 20 or 15% HPDDG can be used to replace CPC or FM in practical shrimp diets. The third study demonstrated that total 92 or 138 g/kg of CPC and SPC (1:1 ratio) may be used in the diet of the Pacific white shrimp replacing 50 or 75% fishmeal in clear and green water under high stocking density and low salinity culture conditions, respectively. The fourth study results showed that up to 100 or 50% anchovy meal can be replaced by salmon meal or hydrolyzed salmon meal without causing impaired growth performance in both clear and green water conditions, respectively. The following up fifth study results indicated that the growth performance of shrimp has not influenced by HSM up to 60 g/kg to replace 50% of the SM in practical diets; however, higher levels resulted in significant decrease in performance. Based on those results of those studies, potential protein ingredients like BY50, HPDDG, CPC, SPC, SM and HSM can be used in practical shrimp diet as a replacement for FM, CPC or SBM. With the shortage of FM and the expansion of aquaculture production, it is necessary for us to evaluate these alternative ingredients and determine the optimum inclusion level to promote sustainable and economically viable aquaculture production
Development of Alternative-protein-based Diets for the Intensive Production of Florida pompano Trachinotus carolinus L.
Get PDFThe Florida pompano industry is a promising enterprise in the United States and with commercial production progressively increasing. However, the success of such an enterprise is dependent on the supply of environmentally sustainable and cost-effective diets able to promote optimum growth with reduced dependence on fishmeal as the primary dietary protein source. To facilitate the development of sustainable and cost-effective diets for Florida pompano, a series of three studies evaluating poultry by-product meal, and a meat and bone meal blend as alternative protein sources to fishmeal in diets for this species was conducted. Primary objectives of the first and second studies were to evaluate the isonitrogenous replacement of fishmeal (initially comprising 15% of the diets) by poultry by-product meal or meat and bone meal blend in pompano diets (40% crude protein and 8% lipid), containing 50% soybean meal as the primary protein source. Based on the results from the first two studies, the third study was conducted to evaluate the potential requirement for the free amino acid taurine in the fishmeal-free diets for Florida pompano.
The results of the first two studies demonstrated that poultry by-product and meat and bone meals are suitable for replacing 66% (10 g/100g) of dietary fishmeal without significant effects on fish performance. However, the total replacement of dietary fishmeal led to significantly lower diet digestibility and poorer pompano performance. In the third study, the supplementation of taurine to the fishmeal-free diets based on poultry by-product meal or meat and bone meal blend from the first and second studies led to a significant improvement of fish performance. Pompano fed diets with at least 0.25% or higher taurine content demonstrated improved growth and feed efficiency relative to fish fed diets without taurine supplementation.
The results of these studies demonstrated that Florida pompano can accept and assimilate fishmeal-free diets based on high levels of soybean meal in combination with poultry by-product meal or meat and bone meal blend and that taurine is likely dietary indispensable for this species
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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