Food Conversion Efficiency Research Articles

Effects of feeding frequency and density on growth, energy budget and physiological performance of sea cucumber Apostichopus japonicus (Selenka)

Feeding frequency and density are two of the most important factors that directly affect the growth and physiology of sea cucumber Apostichopus japonicus. In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber. The results revealed that there was no significant interaction between feeding frequency and stocking density on final weight and specific growth rate (SGR). The maximum SGR occurred at treatment of stocking density D10 with feeding thrice per day. Stepwise multiple regression analysis showed that SGRW and SGRE increased with increasing feeding frequency, and decreased with the increase of stocking density. Density had significant influence on coefficient of variation (CV) for the sea cucumber body weight. For D10 and D20, no significant difference in CV was found between different feeding frequencies. Feed intake, energy intake and feces production rate were significantly affected by feeding frequency, stocking density and their interaction. Density also had significant influence on food conversion efficiency and protein efficiency ratio. Apparent digestibility coefficients of crude protein and crude lipid exhibited remarkable descending trends as stocking density increased. The energy for growth decreased and energy required for metabolism increased with the increase of stocking density, suggesting that crowding stress modified their energy allocation by inhibiting the accumulation of growth energy and accelerating energy consumption of sea cucumber. Cortisol level in coelomic fluid of sea cucumber significantly increased with the increase of stocking density, which could generate energy to satisfy the increasing demand of stress-related energy. Lactate level significantly elevated, and glucose level in coelomic fluid and glycogen in muscle showed remarkable descending trends from D10 to D60, implying long-term energy consumption under high stocking density. Feeding frequency had significant influence on glucose, glycogen and cortisol levels. To some extent, increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber, especially under high stocking density. Statement of relevance•In the present study, a 60-day experiment was conducted to evaluate the effects of feeding frequency (1 time, 2 times and 3 times per day) and stocking density (D10, D20, D40 and D60) on growth performance, feed utilization, endocrine response and energy budget of sea cucumber.•Increasing feeding frequency could effectively reduce coefficient of variation of sea cucumber.•The present study provided valuable information for the intensive culture of A. japonicus.

Increasing fish farm profitability through aquaculture best management practice training in Egypt

Egyptian aquaculture production has grown rapidly to over one million tons per year so that it now provides most of the country's fish supply. However, Egyptian fish farmers have received little extension advice or training. An intervention starting in 2012 aimed to address this gap by providing best management practice (BMP) training for pondbased tilapia monoculture and tilapia-mullet polyculture fish farmers. A series of field-based training modules were developed and designed with the participation of leading fish farmers and delivered through private sector farmer-trainers to over 2400 fish farm owners and managers. This paper reports on the results of an impact assessment survey carried out in 2015 comparing fish farm performance, production and profitability in randomly selected farms where the manager had received and was applying the principles of BMP training (BMP) and farms where the manager had not received IEIDEAS project training (control). The results show that although the two groups were very similar in terms of general farm characteristics, BMP farms were more likely to practice tilapia-mullet polyculture than monoculture of tilapia. The main BMP training messages apparent in the results were improved feed and fertilizer management. This resulted in more efficient food conversion ratios in BMP farms compared to control farms. Average fish yields and values were similar between the two groups, although BMP farms produced less small-sized tilapia and more mullet than the control farms. Lower feed costs resulted in significantly lower operating costs in BMP farms compared to control farms, whereas fixed costs were similar for the two groups. Average net profits were significantly higher in BMP farms compared to control farms equivalent to additional profits of over $15,000 for an average farm size of 7.5 hectares. Taking into account the number of farmers trained and BMP adoption rates suggests that $18.9 million additional profits were generated through the intervention in 2014. The results demonstrate that fish farms in mature aquaculture systems can benefit significantly from the adoption of improved farm management practices suggesting that similar approaches, including field-based BMP training and the use of private sector farmer-trainers should be used to accelerate the development of nascent aquaculture sectors in other parts of Africa. Statement of relevanceWhile it is often assumed that training will benefit fish farmers the true economic benefits have rarely been documented. This research demonstrates clear improvements in the profitability of Egyptian fish farmers following best management practice training.

The effects of host plants on the feeding indices and chemical activities of elm leaf beetle, Xanthogaleruca luteola (Muller) (Coleoptera: Chrysomelidae)

ABSTRACT- Elm leaf beetle (ELB), Xanthoga leruca luteola (Muller), is considered as one of the most important and destructive phytophagous pests of Ulmus species in the north of Iran. In the current study, the effects of three host plants including Ulmus carpinifolia, U. carpinifolia var. umbraculifera, and Zelkova carpinifolia, on feeding indices and biochemical processes of ELB were examined under controlled conditions (25 ± 2 °C; 14:10 LD; 65% RH). The results showed that the highest efficiency of conversion of ingested food (ECI) (23.11±1.36 %) and efficiency of conversion of digested food (ECD) belonged to U. carpinifolia (79.9±4.12 %) and the lowest to Z. carpinifolia (p≤0.05). Relative growth rate (RGR) and approximate digestibility (AD) in U. carpinifolia var umbraculifera and U. carpinifolia were similar to each other. The highest consumption index (CI) belonged to U. carpinifolia var. um braculifera and the lowest to Z. carpinifolia (1.93±0.029, 1.47±0.054), respectively (p≤0.05). Significant differences were found among enzymatic activities of acid (ACP) and alkaline phosphatases (ALP), aspartate aminotransferases (AST and ALT) and lactate dehydrogenase (LDH) in the haemolymph of X. luteola larvae reared on three different host plants. The highest activities of LDH (33±0.58), AST (10074.7±25.25) and ALT (1053.75±5.6) were found in larvae fed on U. carpinifolia (p≤0.05). Also, the highest amount of protein and triglyceride (TAG: 126.5±0.866) was found in larvae fed on U. carpinifolia. The results show that all enzymatic activities significantly decreased on Z. carpinifolia compared with other host plants (p≤0.05). These results indicated that U. carpinifolia is the most appropriate host plant for larvae of X. luteolaas evidenced by the highest nutritional indices as well as activities of enzymatic component in intermediary metabolism.

Effects of light intensity on metabolism and antioxidant defense in Haliotis discus hannai Ino

We examined the effects of light intensity on the metabolism, antioxidant enzymes, and expression of related genes in Haliotis discus hannai Ino, to determine the optimal lighting conditions for aquaculture of these animals. Succinate dehydrogenase activity was significantly lower after 48h in animals exposed to light intensities of 30 and 60μmol/m2/s, while lactate dehydrogenase activity and lactic acid content at 96h were significantly higher compared with animals in the dark or exposed to 5 or 15μmol/m2/s (both P<0.05). There was no significant difference in reactive oxygen species (ROS) contents between animals in the dark and those exposed to 5 or 15μmol/m2/s (P>0.05) throughout the experiment. However, ROS contents under light intensities of 30 and 60μmol/m2/s peaked at 12h, when expression levels of genes encoding catalase (CAT), thioredoxin peroxidase (TPX), sigma-glutathione-s-transferase (GSTS), and mu-glutathione-s-transferase (GSTm) also began to increase, and CAT and glutathione peroxidase (GPX) activities were significantly higher than in animals in the dark or exposed to 5 or 15μmol/m2/s (P<0.05). After a further 12h, the ROS content at 30μmol/m2/s began to decrease, and GPX activity and malondialdehyde (MDA) content also gradually decreased, followed by increases in ROS and MDA 48h later, to reach respective peaks at 96h. Gene expression levels of TPX, GSTS, GSTm, heat shock protein 70 (HSP70), and CAT began to decrease 72h later, suggesting that excessive accumulation of ROS may have caused oxidative damage to the tissues. At a light intensity of 60μmol/m2/s, expression levels of TPX, GSTS, GSTm, and HSP70 genes, total antioxidant capacity, and GPX activity peaked at 48h, and the ROS content was significantly higher than in any other group 48h later (P<0.05). However, gene expression levels of TPX, GSTS, GSTm, HSP70, HSP90, and CAT, and reduced glutathione content began to decrease, indicating that the antioxidant system had been unable to perform its normal physiological functions to withstand the long-term stress of adverse environmental factors. These results suggest that the light intensity should be controlled at 5–15μmol/m2/s during H. discus hannai aquaculture, to maintain the organism's normal physiological metabolism. Statement of relevanceThe disc abalone Haliotis discus hannai is an economically important shellfish in China, with demand growing for this high-protein and low-fat seafood. In 2014, 11,5397 tons of H.discushannai were harvested from aquacultural sources, but supply cannot currently meet consumer demand. In recent years, the natural habitat of H. discus hannai has declined as a result of overfishing, marine reclamation, water pollution, among others, leading to a sharp decrease in the numbers of H. discus hannai in the wild. Thus, the development of an aquacultural system for farming H. discus hannai, as well as for its protection in the wild, are a focus of current research.Light, including photoperiod, quality and intensity, is one of the key environmental factors influencing the growth, culture and survival of aquatic organisms. Over evolutionary time, organisms have evolved both physiological and behavioral mechanisms that enable them to adapt to diurnal fluctuations in light. In Chinese traditional abalone aquaculture, a sunshade net is usually used because of the photophobic nature of abalone. In particular, the aquaculturist usually provides a darkened setting for adult abalones to increase their food intake rate, facilitate their growth and promote gonadal development. For abalones in their natural environment, the light intensity in the water area is relatively stable, suggesting that there is a key regulative effect of light intensity on their growth and development.Gao et al. (2016a,b) found that a dark environment not only adversely affected the daily aquaculture production, but was also associated with a lower growth rate compared with animals reared under higher light intensities, because of lower food conversion efficiency and greater energy losses through excretion and feces. Physiological metabolism and antioxidant defense systems may therefore be key indicators for measuring the suitability of light intensity for aquaculture production. We therefore examined the effects of light intensity on the metabolism and antioxidant defense system, and on the expression of related genes, in H. discus hannai using a light-emitting diode (LED) to replace the conventional fluorescent light source. The results of this study will improve our understanding of the physiological tolerance and antioxidant defense characteristics of abalone under different light intensities, and enable the optimization of environmental light conditions in abalone aquaculture.

Evolution of increased larval competitive ability in Drosophila melanogaster without increased larval feeding rate.

Multiple experimental evolution studies on Drosophila melanogaster in the 1980s and 1990s indicated that enhanced competitive ability evolved primarily through increased larval tolerance to nitrogenous wastes and increased larval feeding and foraging rate, at the cost of efficiency of food conversion to biomass, and this became the widely accepted view of how adaptation to larval crowding evolves in fruitflies.We recently showed that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolved greater competitive ability without evolving higher feeding rates, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater efficiency of food conversion to biomass, increased pupation height and, perhaps, greater urea/ammonia tolerance. This was a very different suite of traits than that seen to evolve under similar selection in D. melanogaster and was closer to the expectations from the theory of K-selection. At that time, we suggested two possible reasons for the differences in the phenotypic correlates of greater competitive ability seen in the studies with D. melanogaster and the other two species. First, that D. ananassae and D. n. nasuta had a very different genetic architecture of traits affecting competitive ability compared to the long-term laboratory populations of D. melanogaster used in the earlier studies, either because the populations of the former two species were relatively recently wild-caught, or by virtue of being different species. Second, that the different evolutionary trajectories in D. ananassae and D. n. nasuta versus D. melanogaster were a reflection of differences in the manner in which larval crowding was imposed in the two sets of selection experiments. The D. melanogaster studies used a higher absolute density of eggs per unit volume of food, and a substantially larger total volume of food, than the studies on D. ananassae and D. n. nasuta. Here, we show that long-term laboratory populations of D. melanogaster, descended from some of the populations used in the earlier studies, evolve essentially the same set of traits as the D. ananassae and D. n. nasuta crowding-adapted populations when subjected to a similar larval density at low absolute volumes of food. As in the case of D. ananassae and D. n. nasuta, and in stark contrast to earlier studies with D. melanogaster, these crowding-adapted populations of D. melanogaster did not evolve greater larval feeding rates as a correlate of increased competitive ability. The present results clearly suggest that the suite of phenotypes through which the evolution of greater competitive ability is achieved in fruitflies depends critically not just on larval density per unit volume of food, but also on the total amount of food available in the culture vials. We discuss these results in the context of an hypothesis about how larval density and the height of the food column in culture vials might interact to alter the fitness costs and benefits of increased larval feeding rates, thus resulting in different routes to the evolution of greater competitive ability, depending on the details of exactly how the larval crowding was implemented.

Effect of geographic origin of Spodoptera exigua (Lepidoptera: Noctuidae) and sugar beet cultivar on nutritional indices of this pest

Nutritional indices of three geographic populations (Miandoab, Moghan and Kalposh) of the fifth instar of Spodoptera exigua (Lepidoptera: Noctuidae) on four sugar beet cultivars (Dorothea, Rozier, Persia and Perimer) were evaluated at 25 ± 1 °C, 65 ± 5 % RH and a 16:8 L:D photoperiod. The estimates of all the nutritional indices were affected by the interaction effect of the geographic population and the sugar beet cultivars. Miandoab population reared on Dorothea, and Moghan and Kalposh populations reared on Perimer had the highest approximate digestibility (AD). Miandoab and Kalposh populations reared on Rozier showed the highest efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) values. Moghan population reared on Persia showed the lowest AD values and the highest ECI and ECD values. The present study showed that the nutritional indices of three populations, in most cases, were significantly different from with other, due to different environmental conditions that the pest collected from there. It is concluded that both geographic origins of the pest and host cultivar affected the nutritional indices of S. exigua larvae.

Environmental remediation potential of Perinereis aibuhitensis (Polychaeta) based on the effects of temperature and feed types on its carbon and nitrogen budgets

ABSTRACTThe effects of three temperatures (15°C, 20°C and 25°C) and four feed types (artificial feed, AF; sediment, SM; fish faeces, FF; and fish meat, FM) on the growth, carbon budget and nitrogen budget of the polychaete Perinereis aibuhitensis were evaluated over a 35 day period. The final body weight and specific growth rate (SGR) of P. aibuhitensis were significantly affected by temperature and feed types (T, F = 15.831, P = 0.000; Feed, F = 81.827, P = 0.000), but the interaction between these factors was not significant (F = 0.435, P = 0.848). The worms achieved the highest SGR in the AF group at 20°C. However, the SGR in the SM group was only half that of the other groups. The food conversion efficiency (FCE) was significantly lower at 25°C than at 15°C and 20°C (P < 0.05). The FCE was highest in the FM group (P = 0.000), with a mean of 39.83%. The apparent digestibility rate (ADR) at 25°C was significantly higher than at 15°C and 20°C (P < 0.05). These findings suggest that the higher FCE coupled with ADR (78.48%) resulted in higher SGR in worms that were fed artificial feed at 20°C. The slow growth in the SM group was attributed to the lower organic content in sediment and the higher expenditure of carbon and nitrogen in faeces and metabolism. The proportion of total C and N deposited was lower in groups fed with the higher-quality feed used for fish cage farming. Most of feed carbon and nitrogen were released into the water by polychaetes, which was good for the sediment environment recovery under the fish cages.

Effects of Sublethal Concentrations of Cyantraniliprole on the Development, Fecundity and Nutritional Physiology of the Black Cutworm Agrotis ipsilon (Lepidoptera: Noctuidae).

To better understand the sublethal effects of cyantraniliprole on the black cutworm Agrotis ipsilon (Lepidoptera: Noctuidae), several studies were carried out to investigate sublethal effects on development stages, population parameters, feeding indices and nutrient content of A. ipsilon. The result of a bioassay showed that cyantraniliprole had high toxicity against A. ipsilon fourth-instar larvae with an LC50 of 0.354 μg.g−1 using an artificial diet. Compared with controls, sublethal doses of cyantraniliprole at LC5, LC20 and LC40 levels prolonged larval and pupal duration and extended mean generation time and total preovipositional period. In addition, survival rate, reproductive value, intrinsic and finite rates of increase and net reproduction rate declined significantly. Meanwhile, cyantraniliprole had markedly antifeedant effects; decreased the relative growth rate (RGR), the relative consumption rate (RCR), the efficiency of conversion of ingested food (ECI), the efficiency of conversion of digested food (ECD); and increased the approximate digestibility (AD) significantly. This phenomenon contributed to the decrease of nutrient contents, including lipids, protein and carbohydrates, to the point that insufficient energy was available for normal growth. Therefore, sublethal concentrations of cyantraniliprole decreased growth speed and reduced population reproduction of A. ipsilon. This result provides information useful in integrated pest management (IPM) programs for A. ipsilon.

Adaptation to larval crowding in Drosophila ananassae and Drosophila nasuta nasuta: increased larval competitive ability without increased larval feeding rate.

The standard view of adaptation to larval crowding in fruitflies, built on results from 25 years of multiple experimental evolution studies on Drosophila melanogaster, was that enhanced competitive ability evolves primarily through increased larval feeding and foraging rate, and increased larval tolerance to nitrogenous wastes, at the cost of efficiency of food conversion to biomass. These results were at odds from the predictions of classical K-selection theory, notably the expectation that selection at high density should result in the increase of efficiency of conversion of food to biomass, and were better interpreted through the lens of α-selection. We show here that populations of D. ananassae and D. n. nasuta subjected to extreme larval crowding evolve greater competitive ability and pre-adult survivorship at high density, primarily through a combination of reduced larval duration, faster attainment of minimum critical size for pupation, greater time efficiency of food conversion to biomass and increased pupation height, with a relatively small role of increased urea/ammonia tolerance, if at all. This is a very different suite of traits than that seen to evolve under similar selection in D. melanogaster, and seems to be closer to the expectations from the canonical theory of K-selection. We also discuss possible reasons for these differences in results across the three species. Overall, the results reinforce the view that our understanding of the evolution of competitive ability in fruitflies needs to be more nuanced than before, with an appreciation that there may be multiple evolutionary routes through which higher competitive ability can be attained.

An Attempt to Overcome Dioxane Toxicity by Rabbits using Vitamin C

In an experiment for 60 days, newly weaned male rabbits were fed diets either containing dioxane (3.2mg/Kg), dioxane (3.2mg/Kg) plus vitamin C (1g/Kg), or vitamin C (1g/Kg) alone comparing with the control diet without any additives. These dietary treatments were evaluated via general observations of the experimented rabbits, their growth performance, food utilization, digestibility coefficients, economic efficiency, slaughter test and flesh chemical composition. The obtained results revealed the negative effects of feeding rabbits the contaminated diets that were responsible for very bad appearance of the face, nose and eyes, stench smell (similar to that of the dioxane itself) of the rabbits and their feces as well as their flesh (during the chemical analysis of the flesh), moderate vertebrates cord malformation [the upper (cervical) part was twisted], smaller size and weight, weakness and unbalance, increased food and water consumption followed by lower food conversion and economic efficiency as well as boneless meat and protein contents of the carcasses. The addition of vitamin C did not prevent these negative effects (but, to some extent, may ameliorate). Hence, the avoidance of such contaminant, in foods and drinking water, must be recognized for good rearing of the very sensitive animals such as rabbits.

Estimation of Some Life-History Parameters from Length at First Maturity of African Catfish Clarias Gariepinus (Burchell, 1822) Cultured Under 0l: 24d Photoperiod Using Empirical Equations

Estimation of some life history parameters such as length (L), weight (W), mortality (M),population food consumption (Q/B), gross food conversion efficiency (GE), von Bertalanffy growth factor (K) andlife span (tmax) using empirical equations was conducted on Clarias gariepinus reared in triplicate in the 0L: 24Dphotoperiod. The mean length and weight at first maturity was 45.7 ±0.2cm, and 728.13 ± 0.5g respectively. Highesttemperature recorded was 27 °C. Estimate of optimum length (Lopt) was 49.1 cm, mortality was 2.37/year and 1.18for the 6-month cultured period, food consumed and gross food conversion efficiency was 8.7 and 0.181respectively. The life span estimate was 1.8 years, while the von Bertalanffy growth parameter calculated from thetmax was 1.67. These estimates could be used to cropping the fish or obtain desired length class with the highestbiomass for harvest, evaluate signs of growth overharvesting, know and prevent mortality at larval or adult stages offish, indicate poor or good food conversion efficiency, know the life span of the fish thereby informing the time ofharvest and thus saving cost of production. All these could be used in the management of the species in aquaculture.(Keywords: life history, length, weight, sexual maturity, photoperiod)

Effects of periodical salinity fluctuation on the growth, molting, energy homeostasis and molting-related gene expression of Litopenaeus vannamei

To determine the response of Litopenaeus vannamei to periodical salinity fluctuation, a 30-day experiment was conducted in laboratory. In this experiment, two salinity fluctuation amplitudes of 4 (group S4) and 10 (group S10) were designed. The constant salinity of 30 (group S0) was used as the control. Levels of shrimp growth, molting frequency (MF), cellular energy status (ATP, ADP and AMP), as well as the expression of genes encoding molt-inhibiting hormone (MIH), crustacean hyperglycemic hormone (CHH), ecdysteroid-regulated protein (ERP), and energy-related AMP-activated protein kinase (AMPK) were determined. The results showed that periodical salinity fluctuation significantly influenced all indicators except MF which ranged from 13.3% in group S10 to15.4% in group S4. In comparison with shrimps cultured at the constant salinity of 30, those in group S4 showed a significant elevation in growth rate, food conversion efficiency, cellular energy status, ERP and MIH gene transcript abundance, and a significant reduction in CHH and AMPK transcript abundance (P < 0.05). However, salinity fluctuation of 10 only resulted in a significant variation in MIH and CHH gene expression when compared to the control (P < 0.05). According to our findings, L. vannamei may be highly capable of tolerating salinity fluctuation. When ambient salinity fluctuated at approx. 4, the increased MF and energy stores in organisms may aid to promoting shrimp growth.

Effects of the Agglutinins Extracted From Rhizoctonia solani (Cantharellales: Ceratobasidiaceae) on Pieris brassicae (Lepidoptera: Pieridae).

Lectins are widespread proteins found in plants, fungi, bacteria, and vertebrates, and they play the critical roles in many physiological functions. Two lectin molecules (namely, RSAI and RSAII) were extracted from Rhizoctonia solani Kuhn and their effects on Pieris brassicae L. larvae were determined by larval survival rate, body mass, nutritional indices, digestive enzyme activities, and caspase-3 gene expression. The highest mortality caused by RSA treatment was recorded up to 80%, the larval weight decreased to 0.05 g and Similarly, RSAs significantly decreased nutritional indices including conversion efficiency of ingested food (ECI), conversion efficiency of digested food (ECD), approximate digestibility (AD), relative consumption rate (RCR), and relative growth rate (RGR) in a dose-dependent manner. Activities of α-amylase and α- and β-glucosidases significantly decreased in the larvae fed with RSA-treated diets. Also, activities of TAG-lipase and proteases significantly reduced after feeding with different concentrations of RSAs. Gene expression analysis of caspase-3 in control and treated larvae revealed significant increment of its expression in the larvae fed with RSAI and RSAII, respectively, 9.52- and 1.47-fold compared to control. These results clearly demonstrated insecticidal effects of R. solani lectins on P. brassicae via several physiological pathways, thus rendering RSA as a good target for furthering our knowledge and suggesting new strategies to overcome pesticide side effects.

Elemental concentrations in the frass of saproxylic insects suggest a role in micronutrient cycling

AbstractConcentrations of 22 elements in pinewood were compared with that in frass produced by insects representing the following taxa: Reticulitermes spp. (Rhinotermitidae), Zootermopsis nevadensis (Termopsidae), Incisitermes snyderi (Kalotermitidae), Hylotrupes spp. (Cerambycidae), Heterobostrychus spp. (Bostrichidae), Lyctus spp. (Bostrichidae), and representatives of the family Ptinidae (formerly Anobiidae). Twenty elements (Al, B, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Mo, Na, Ni, P, Pb, Si, Sr, and Zn) were measured using inductively coupled plasma‐optical emission spectroscopy (ICP‐OES), whereas carbon, hydrogen, and nitrogen percentages were measured using a CHN autoanalyzer. Chromium was the only element present at a statistically lower concentration in all frass types compared to pinewood. A comparison of pinewood to frass from those taxa that fed on pine revealed that Reticulitermes frass contained significantly higher levels of 15 elements, Zootermopsis 10, Ptinidae 5, Incisitermes 4, and Hylotrupes 1. Only Incisitermes frass showed a significantly higher percent carbon than pinewood and Reticulitermes, Zootermopsis, and Ptinidae showed significantly higher percent nitrogen. Examination of percent approximate digestibility (PAD) indicated that Reticulitermes frass had 14 elements that were ≥200% more concentrated than found in pinewood, whereas Zootermopsis had 6, Lyctus 5, ptinid 4, Hylotrupes and Heterobostrychus 3, and Incisitermes none. This survey of elements in frass indicates that saproxylic insects are, for the most part, not sequestrating but rather recycling (releasing) the store of micronutrients in wood biomass, with the greatest potential contribution to soil nutrient cycles attributable to subterranean termites.

Cotesia ruficrus (Hymenoptera: Braconidae) Parasitizing Cnaphalocrocis medinalis (Lepidoptera: Pyralidae): Developmental Interactions and Food Utilization Efficiency of Hosts.

Cotesia ruficrus (Haliday), a gregarious larval endoparasitoid, is an important biological control agent of various pest species. The developmental interactions between the host rice leaf folder, Cnaphalocrocis medinalis (Guenée), and its koinobiont parasitoid, C. ruficrus, were investigated for the first time under laboratory conditions. The effects of host instar at parasitization on the development time, clutch size, and survival of C. ruficrus were determined. The results showed that the parasitoids starting parasitism in the fourth-instar larvae had the shortest development duration and highest fecundity. Meanwhile, the growth of the host parasitized by C. ruficrus in various instars was also observed. The results indicated that the growth of the parasitized larvae was significantly inhibited, compared with unparasitized ones, irrespective of the host instar at oviposition. In addition, the effect of parasitism on food consumption and utilization of the fourth-instar larvae was determined, suggesting that the nutritional physiology of the host was affected by parasitism. Wet or dry weight gain, food consumption, and fecal matter were all significantly reduced in the parasitized larvae in contrast with the unparasitized larvae. Parasitization by C. ruficrus could significantly increase the approximate digestibility of the host.

The effect of aerobic exercise and starvation on growth performance and postprandial metabolic response in juvenile southern catfish (Silurus meridionalis)

To investigate the effects of aerobic exercise and starvation on growth performance, postprandial metabolic response and their interaction in a sedentary fish species, either satiation-fed or starved juvenile southern catfish (Silurus meridionalis) were exercised at 25°C under three water velocities, i.e., nearly still water (control), 1 body length (bl) s−1 and 2 bl s−1, for eight weeks. Then, the feed intake (FI), food conversion efficiency (FCE), specific growth rate (SGR), morphological parameters, resting ṀO2 (ṀO2rest) and postprandial ṀO2 responses of the experimental fish were measured. Exercise at a low velocity (1 bl s−1) showed no effect on any growth performance parameter, whereas exercise at a high velocity (2 bl s−1) exhibited higher FI but similar SGR due to the extra energy expenditure from swimming and consequent decreased FCE. Starvation led to a significant body mass loss, whereas the effect intensified in both exercise groups. Exercise resulted in improved cardio-respiratory capacity, as indicated by increased gill and heart indexes, whereas it exhibited no effect on resting and postprandial metabolism in S. meridionalis. The starved fish displayed significantly larger heart, gill and digestive tract indexes compared with the feeding fish, suggesting selective maintenance of cardio-respiratory and digestive function in this fish species during starvation. However, starved fish still exhibited impaired digestive performance, as evidenced by the prolonged duration and low postprandial metabolic increase, and this effect was further exacerbated in both the 1 and 2 bl s−1 exercise groups. These data suggest the following: (1) aerobic exercise produced no improvement in growth performance but may have led to the impairment of growth under insufficient food conditions; (2) the mass of different organs and tissues responded differently to aerobic exercise and starvation due to the different physiological roles they play; and (3) aerobic exercise had no effect on the postprandial metabolic response under a “normal feeding” situation, whereas it may have resulted in the impairment of the digestive capacity when food availability was low due to the competition of energy and oxygen under unfavorable conditions in juvenile S. meridionalis.

Anthelmintic administration to small ruminants in emergency drought responses: assessing the impact in two locations of northern Kenya.

Internal parasites are a significant determinant of the productivity of ruminant species in the tropics. Provision of anthelmintics has become a predominant part of animal health interventions in emergency drought responses, aiming to maintain the food conversion efficiency of livestock when pasture is scarce. This study aimed to assess the owner-perceived impact of anthelmintic provision on the health and productivity of small ruminants in the drought-prone counties of Isiolo and Marsabit, northern Kenya. Participatory approaches were used to retrospectively measure differences in key indicators of livestock output before and after anthelmintic administration. Results showed that there was no perceived impact of anthelmintic administration during droughts on small ruminant health and productivity, but some benefit of anthelmintic administration during rainy season was perceived. The study also provided some evidence of potential differences in the epidemiology of internal parasites between the counties. These findings may be utilised to inform future livestock intervention programmes in drought-prone areas.

Effects of tea saponin on growth and development, nutritional indicators, and hormone titers in diamondback moths feeding on different host plant species

The diamondback moth (DBM) is an important worldwide pest. This insect has been studied for several decades; however, its control remains problematic. Numerous chemical insecticides have become ineffective and chemical residues constitute an important problem. In the present study, we determined the mortality of 3rd instar DBM larvae feeding on three different host plant species and exposed to various concentrations of tea saponin (TS). In addition, we evaluated growth and development parameters, nutritional indicators, and juvenile hormone (JH) and molting hormone (MH) titers in 2nd instar larvae exposed to LC20 and LC50 doses of TS. We found that treatment of DBM larvae with LC20 and LC50 doses of TS led to lower growth rates, decreased feed consumption, reduced frass production, lower pupal weights, reduced percentage pupation, slower adult emergence percentages, and diminished fecundity, but prolonged durations of the larval and pupal periods. The efficiency of conversion of ingested and digested food increased, but the approximate digestibility did not differ significantly between treatments and controls. JH and MH titers were higher after TS treatment; these increases varied according to the host species and TS concentration. Our results indicate that TS represents a potential new alternative insecticide based on its natural origin, low cost, and minimum environmental impact.

Evaluation of Crinkle Grass Rhizoclonium riparium in a Diet for Pacific White Shrimp Penaeus vannamei Post Larvae

A feeding experiment to evaluate the inclusion of Rhizoclonium raw meal (RM) in diets for growth and feed efficiency in Pacific white shrimp, Penaeus vannamei was conducted. Five diets were formulated containing increasing levels of RM inclusion: 0%, (control), 5.25%, 10.50%, 15.75%, and a diet with 15.75% RM totally replacing the mineral mix. The diets were fed to shrimp post larvae for 60 days with 4 replicates. Survival rates were excellent (98-93%) and similar for all treatments. Final average body weight (FABW) was highest in shrimp fed the diet containing 5.25% RM, and lowest with the 10.50% RM diet; FABW of the other groups were either statistically similar or lower than the control group. A similar pattern was also observed for specific growth rate (SGR) and protein gain (PG). Food conversion efficiency (FCE) was highest in shrimp fed the diet containing 5.25% RM; protein efficiency ratio (PER) was higher in all groups fed diets containing RM than the control group. Replacing the dietary mineral component with RM did not significantly affect the growth, feed efficiency, and survival rate. The present study demonstrated that Rhizoclonium riparium var. implexum is a possible complementary protein source and could replace from 15%-45% imported soybean meal (SBM) in the P. vannamei post larvae diet. An additional 1% RM could replace the dietary minerals.

Ecobiology of the Common Evening Brown, Melanitis leda Linn. (Lepidoptera: Rhopalocera: Nymphalidae: Satyrinae)

The common evening brown butterfly, Melanitis leda Linn. is seasonal in its occurrence at Visakhapatnam (17o 42' N and 82 18' E), South India, during September to March. It utilizes Brachiaria distachya (Linn.) Stapf. for oviposition and as larval host. It lays eggs singly. The hatched larvae show five instars. It shows light green colour with a pair of horns in the head region. Pupa shows green colour with a mid-dorsal dark green line. The developmental time from egg to adult emergence was 27 – 35 (31.40 ± 3.43) days in the laboratory conditions with 28 ± 20 C, 80 ± 10% relative humidity, 12 – 14 h day-length. The early lifestages (eggs, larvae, pupae) are evident on B. distachya for a period of 150 days during September to January, thus producing an estimated three to four overlapping broods per year. There was a relatively high frequency of the early lifestages during October to December corresponding to rainy and winter seasons. Probably this Satyrid may require more moist and shady conditions for its occurrence and reproduction throughout the year. Such conditions were not available in the study biotope throughout the year, hence its occurrence over a limited part of the year. The larvae were efficient in consuming and utilizing the host leaves as indicated by the food utilization and nutritional indices of different instars. Approximate digestibility (AD) 96.66% - 57.24%, efficiency of conversion of ingested food to body substance (ECI) 6.66% - 36.52%, efficiency of conversion of digested food to body substance (ECD) 6.89% - 51.76%