Apparent Feed Conversion Ratio Research Articles

Biochemical analysis of bullfrog liver and blood: insights into growth and development

The aim of this study was to evaluate the productive and physiological performance of bullfrogs (Lithobates catesbeianus) after metamorphosis, through zootechnical growth parameters and the quantification of proteins and enzymes present in the liver. In addition we observed the behavior of circulating amino acids in the blood. The experiment was conducted at the Experimental Station of the Aquaculture, APTA Regional – SAA, in São Paulo, Brazil. We used 400 L. catesbeianus froglets weighing 5.76±1.32g, which were distributed in four fattening tanks in the wet system, installed under an agricultural greenhouse at  density of 51 frogs/m². The animals were fed with 5% of the biomass of each tank every day, with extruded feed for carnivorous fish with 40% Crude Protein. Every 28 days, they were weighed to calculate weight gain and apparent feed conversion ratio. At the same time, two animals from each tank were chosen randomly to have their blood and liver collected for biochemical analysis to quantify amino acids, proteins, phenols, peroxidase and polyphenol oxidase. The results obtained indicate that the absence of screening every 15 days affected the development and uniformity of the animals, favoring cannibalism. The average apparent feed conversion was 1.84. There was an increasing and proportional formation of proteins with low degradation as the animals gained weight. As for amino acids, we detected arginine, isoleucine, alanine and tryptophan in the first month, with trypsin appearing after 60 days. These results lead us to state that total or partial screening is essential during the first month after metamorphosis, and that the feed provided, although not specific to the species, fulfilled its role in animal metabolism, with little formation of phenolic compounds and free radicals.

Effect of molasses supplementation on growth performance, water quality and microbial dynamics during indoor rearing of pacific white shrimp Penaeus vannamei Boone, 1931

 A study was conducted with Pacific white-leg shrimp (Penaeus vannamei Boone, 1931) juveniles to ascertain the effect ofmolasses supplementation on the growth performance, culture environment and microbial dynamics of rearing water. Theweight gain at the end of the experiment of 55 days duration were significantly (p<0.05) higher in molasses supplementedgroup (12.08±0.45 g) as compared to control (10.44±0.34 g). Apparent feed conversion ratio (AFCR) was found significantly(p>0.05) lower in case of molasses supplemented group with higher survival percentage. Supplementation of molasses alsoimproved the rearing water quality. The total ammonia nitrogen (TAN) level was significantly (p<0.05) lower in the rearingwater of molasses supplemented tank (2.213±0.165 ppm) compared to control (2.915±0.191 ppm). There was no significantdifference in total heterotrophic bacteria (THB) and total Vibrio (TV) load between the water of the two groups. However,the proportion of TV to THB was significantly lower in case of molasses supplemented group as compared to control. Thisstudy indicated that supplementation of molasses can significantly improve the growth performance of P. vannamei withbetter feed utilisation and also improves the water quality by reducing the level of toxic gas i.e. ammonia in water. Keywords: Ammonia, C:N ratio, Molasses, Vibrio

Evaluation of gardi bangana dero and sahar tor putitora with rohu labeo rohita and Naini cirrhinus mrigala in poly culture at different stocking combinations

Conventional multispecies poly culture with compatible native species intercrop augments optimum utilization of the ecological niches in the pond ecosystem, diversity conservation, food value, and poverty alleviation potential through the direct involvement of rural people. Given the conservational value and the aquaculture potential of several indigenous species, Gardi Bangana dero and Sahar Tor putitora have been identified as important food fish. Rohu Labeo rohita and Naini Cirrhinus mrigala are two other native fishes that fetch a very high market price and are of high cultural value. A polyculture experiment was carried out on the Rohu, Naini, Gardi, and Sahar with the objectives to evaluate the optimum stocking density in terms of average body weight, specific growth rate, and total fish production of these fishes for nine months. Results showed that the final body weight of Rohu, Naini, Gardi were high in respective major poly culture systems, but Sahar was high in Naini major system. In case of survival, all fish species had high survival rate in Naini major system. Also, net fish yield of Rohu was observed significantly higher in Rohu major pol yculture system than in Naini major and Gardi major poly culture systems but not with control poly culture systems. Whereas, parameters of Naini, Gardi and Sahar observed similar in all poly culture systems. Apparent Feed Conversion Ratio was found higher in Gardi major poly culture system than others. Thus, for getting optimal stocking density, Naini polyculture system with supplementary feed is recommended.

Densidade de estocagem de tilápia vermelha (Oreochromis sp.) criada em sistema comercial de bioflocos na Colômbia

ABSTRACT Biofloc technology (BFT) has several advantages, such as low water supply requirements and apparent feed conversion ratio (FCR), and high densities. However, there is no information on adequate densities and their effect on the large-scale production of different species. In this study, we determined the effects of the stocking density of monosex red tilapia reared using BFT on the growth performance, water quality parameters, and chemical characteristics of fish on a large scale and under culture conditions in eastern Colombia. In total, six circular tanks (diameter: 14 m, height: 1 m, and capacity: 153 m³) were used in this investigation. Two stocking densities were considered: treatment 1 (T30: 30 fish/m³) and treatment 2 (T40: 40 fish/m³), in triplicate. The water quality parameters of the two treatment densities were within the normal ranges for the species, but dissolved oxygen decreased throughout the production process. The T30 and T40 treatments did not result in significant differences in growth performance. At the end of the trial, the FCRs were 1.6 and 1.7 from T30 and T40, respectively. Fishes raised at a lower density had a similar weight gain; however, their final biomass was not significantly different. BFT did not affect the nutritional characteristics of fish; the percentage of protein (%) in tilapia was 17.81% ±1% and 16.72% ±1% in the T30 and T40 groups, respectively. None of the fish were infected by Salmonella spp. or Vibrio cholerae.

Effects of estuarine oyster, Crassostrea cuttackensis as the extractive species at varied densities on productivity and culture environment in brackishwater integrated multi-trophic aquaculture (BIMTA) system

Integrated multi-trophic aquaculture (IMTA) involves incorporation of species from different trophic or nutritional levels in the same system to get better production based on mutual gain to the co-cultured species and improved ecosystem health. However, in brackishwater, very few trials on IMTA have been conducted so far with scarce information on the optimum density of extractive species like oyster and seaweed. Edible estuarine oyster, Crassostrea cuttackensis is abundantly available in the Sundarban. Being a filter-feeder, it can be used as an extractive species for organic matter removal in IMTA. Therefore, an experimental trial was conducted to assess the effect of different stocking densities of C. cuttackensis on performances of milkfish (Chanos chanos) and Pacific white-leg shrimp (Penaeus vannamei), and environmental remediation in an IMTA system. There were three densities of oyster, 0.6 (T1), 1.2 (T2), and 1.8 (T3) kg m−3 distributed to 1000 L FRP circular tanks containing milkfish (4.51 ± 0.05 g) and white-leg shrimp (4.50 ± 0.03 g) at 25 and 50 no. m−3, respectively. Control tanks contained the same number of milkfish and shrimp with no oyster. All the three treatments and control had triplicate tanks. During the 60-day trial period, fish and shrimp were fed with a common diet containing 30% crude protein at 5% of biomass. Results showed that the highest growth of milkfish (24.66 ± 0.31 g) and shrimp (15.20 ± 0.17 g) was obtained in T3 (P < 0.05) compared to that of the control [13.97 ± 0.08 g (milkfish), 11.83 ± 0.13 g (shrimp)]. Apparent feed conversion ratio (AFCR) was the lowest in T3 (0.92 ± 0.01) (P < 0.05). Although, survival of milkfish did not vary, shrimp survival was the highest in T3. The inorganic nutrients (nitrogenous and phosphorus compounds) and particulate organic matter (POM) of water improved in all the IMTA treatments compared to the control. The number of total heterotrophic bacteria and Vibrio counts in tank water was significantly low in T3 (P < 0.05). The benefit-cost ratio in T3 was found to be 1.6 times higher than that of the control. This trial suggested that oyster, C. cuttackensis can act as an effective extractive species in IMTA system when stocked at a density of 1.8 kg m−3. Therefore, treatment T3 IMTA model proved to be more productive and had a successful bio-remediation effect on the environment.

Effect of rearing systems and dietary probiotic supplementation on the growth and gut microbiota of Nile tilapia (Oreochromis niloticus) larvae

The establishment of the early-life gut microbiota plays an important role in fish development and influences the host's health status and growth performance. Different rearing conditions can impact the initial colonization of the gut microbiota, while the addition of probiotics may also affect such colonization. However, how this may affect fish larvae survival and growth remains largely unexplored. In this study, 3-day old Nile tilapia embryos were hatched until 9 days post fertilization (dpf) in three systems, including one flow-through system (FTS) and two identical recirculating aquaculture systems (RAS). When feeding started at 10 dpf, tilapia larvae in the FTS and one of the RAS were fed with a control diet, while larvae in the second RAS were fed with the control diet coated with B. subtilis spores (RASB). The feeding trial lasted 26 days, from larvae to fry stage, during which the survival, growth performance and gut microbiota were analyzed. The larvae reared in FTS showed significantly lower survival than those in RAS and RASB, while no differences were observed in fish growth and apparent feed conversion ratio between treatments. Different rearing systems resulted in different gut microbiota compositions, which strongly correlated with the survival rate and standard body length at harvest. Cetobacterium was enriched in RAS and RASB, while was barely detected in the gut of FTS-reared tilapia fry. Probiotic supplementation increased the relative abundance of beneficial Bacillus in fish gut. Our findings indicate that rearing fish larvae in RAS supports better survival compared to FTS, while dietary probiotic supplementation further modulates the gut bacterial composition and stimulates presence of beneficial bacteria during early life.

Alternative dietary protein source for nile Tilapia: Giant African Snail (Achatina fulica, Ferussac, 1821)

The present study was conducted for two months between November 2019 and December 2019 to investigate the growth performance of Nile Tilapia fed with diets containing soyabean 100% (T1), soyabean and Achatina fulica: 50/50% (T2) and A. fulica 100% (T3). The experimental diets were formulated with 45% crude protein content. The stocking density was 30 fingerlings per tank of size 1m*1m*0.8m with three replications for each treatment. The tanks were stocked with the fingerlings of uniform size 9 ± 677 cm and weight 24 ± 0.66g. The experimental fishes were fed twice a day at 5% of their body weight. No significant differences (p˃0.05) in average weight gain, apparent feed conversion ratio (AFCR), daily weight gain, gross fish yield and net fish yield were observed. The study revealed that Giant African Snail (GAS) can be used either as partial or total replacement for soyabean as protein source for the fish. The use of harmful pest A. fulica in fish feed shows bright prospect in reducing the feeding expenses together with its suitable management.

Evaluation of Nile tilapia in monoculture and polyculture with giant freshwater prawn in biofloc technology system and in recirculation aquaculture system

Biofloc technology system (BFT), recirculation aquaculture system (RAS) and polyculture promote efficient use of water, area and nutrient recycling, which are essential practices for sustainable aquaculture development. The aim of this study was to evaluate the growth, feed efficiency, biofloc composition and water quality of Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in monoculture and polyculture with giant freshwater prawn Macrobrachium rosenbergii (De Man, 1906) in BFT and RAS, over a period of 30 days. Fish (n = 128; 7.29 ± 0.67 g) were distributed randomly in 16 experimental tanks (8 fish/tank). Prawn (n = 96; 0.50 ± 0.09 g) were allocated in 8 experimental tanks (12 prawn/tank) in a polyculture. The experimental design was completely randomized with four treatments with four replicates each, in a factorial design 2 × 2 (BFT and RAS vs. monoculture and polyculture). The experimental diet (28% of digestible protein; 3100 kcal kg−1 of digestible energy) was used both to fish and prawn in BFT and RAS. There was significant effect (p < 0.01) of the system and the culture for weight gain, apparent feed conversion and protein efficiency ratio. The average weight gain and apparent feed conversion of tilapia in monoculture (30.04 g and 1.39) and in polyculture (36.44 g and 1.27) were superior (p < 0.01) in BFT than in monoculture (23.64 g and 1.74) and in polyculture (24.14 g and 1.61) in RAS. Weight gain and survival of giant freshwater prawn was superior (p < 0.01) in BFT (0.43 g and 87%) compared to RAS (0.26 g and 79%). The data showed that BFT provides better growth performance responses in monoculture for Nile tilapia and in polyculture with giant freshwater prawn compared to RAS.

Evaluation of live duckweed, Wolffia globosa as an allochthonous feed for Labeo rohita fry during nursery rearing

A 40 days feeding trial with Labeo rohita (rohu) fry was conducted in six outdoor cemented tanks (5m × 4m × 1 m; 6–8 cm soil base) to establish the relative impact of on‐farm grown live Wolffia globosa (a duckweed with crude protein of 28.57%) and a formulated iso‐nitrogenous feed (crude protein 28.37%) on growth performance, survival, health and overall quality of fingerlings. The experimental tanks were dried, limed at 250 kg/ha, filled with ground water and subsequently applied with cow dung (soaked overnight) and mustard oil cake at 1,000 kg/ha and 50 kg/ha respectively. The fry were stocked at 0.3 millions/ha in six prepared tanks, and fed live Wolffia (T1) and formulated feed (T2). Results of the study indicate better performance (p < 0.05) of fry in terms of final mean weight (7.83 g), length (8.82 cm), daily growth index (6.51 g %/day) and survival (89.5%) than those fed on formulated feed. Furthermore, significantly improved (p < 0.05) feed utilization parameters viz. apparent feed conversion ratio (AFCR), apparent protein conversion efficiency (APCE), apparent protein efficiency ratio (APER); haematological parameters viz. total erythrocyte count (TEC), total leucocyte count (TLC), packed cell volume (PCV), plasma glucose and protein of fry were also observed in T1 (live Wolffia). Overall findings from this study hints towards the possible utilization of on‐farm grown live Wolffia as a suitable nutrient source for fry rearing of L. rohita.

Integrated culture of Nile tilapia and Amazon river prawn in stagnant ponds, using nutrient-rich water and substrates

Monoculture is an inefficient aquaculture system because on average <~20% of the diet supplied is assimilated by the target species. Integrated aquaculture systems are attractive alternatives because they take advantage of the wasted nutrients to produce other marketable species. Substrate addition is known as beneficial management to promote natural food (periphyton) by trapping nutrients. Thus, the aim of this study was to evaluate the technical feasibility of integrating the culture of Nile tilapia, Oreochromis niloticus with the culture of Amazon river prawn, Macrobrachium amazonicum in stagnant ponds supplied with water rich in nitrogen and phosphorus, and investigate if the addition of substrates affects the performance of both species. The target species (tilapia) was fed with commercial diet, while the secondary species (prawn) took advantage directly and indirectly of feed wastes. A completely randomized experimental design comprised of three treatments (culture with geotextile blanket substrates, bamboo substrates, and no substrates) with four replicates per treatment was used. Vertical substrates were installed in each pond, which total area was equivalent to 50% pond bottom area. Twelve 0.01-ha earthen ponds were stocked with Nile tilapia (~30 g) and prawn post-larvae (~0.04 g) together, which were cultured for 140 days. Dissolved oxygen, pH and temperature were measured daily, whereas water samples were collected biweekly to evaluate ammonia-N, nitrite-N and nitrate-N. The water quality remained suitable for production throughout the experimental period and was not affected by the use of substrates. The addition of substrates did not affect the growth, survival, productivity and apparent feed conversion ratio of Nile tilapia. On average, Nile tilapia grew to ~0.5 kg, with a survival close to 90%, resulting in productivity of about 5 t/ha. On the other hand, substrates increased the portion of larger prawns in the harvest, improving market value. A major effect was observed using the geotextile blanket substrate. The proportions of prawn heavier than 3 g were 54.2, 41.9 and 25.6% in ponds using geotextile blanket, bamboo and no substrate, respectively. In conclusion, farming Nile tilapia and Amazon river prawn in integrated systems supplied with nutrient-rich water in stagnant ponds is technically feasible. The addition of substrates does not affect tilapia performance but increase the proportion of large prawns; the effect was more pronounced with geotextile substrates.

EFFECT OF REPLACING MUSTARD OILCAKE BY LINSEED OILCAKE ON GROWTH PERFORMANCE OF NILE TILAPIA (Oreochromis niloticus, Linnaeus, 1758)

 This study was done to explore the effect of replacing mustard oilcake by linseed oilcake in feed on the growth performance of Nile Tilapia (Oreochromis niloticus). Mustard oilcake (MOC) was replaced by linseed oil cake (LOC) at three different level 0%, 50% and 100% to prepare three different types of diets. Diets were prepared with about 18% analyzed crude protein content. Fingerlings were kept in three happa with three replications for each diet in completely randomized design (CRD). Fish of average weight 5.31 g were stocked in happa having size 1.5m×1.5m×1.2m. The experimental fish were fed 3% of their body weight per day, once in the morning for five months continuously. No significant difference (p&gt;0.05) in final mean weight, final total weight, average daily weight gain (DWG), survival rate, extrapolated gross fish yield (GFY), extrapolated net fish yield (NFY) and apparent feed conversion ratio (AFCR) among different treatments were observed. Hence, linseed oilcake can be used as the substitute in the feed of tilapia, if it is locally available.  Journal of Institute of Science and Technology, 2017, 22 (1): 10-16 

Effects of kelp Ecklonia maxima inclusion in formulated feed on the growth, feed utilisation and gut microbiota of South African abalone Haliotis midae

The effect of kelp Ecklonia maxima inclusion in formulated feeds on abalone growth and gut bacterial communities has not been previously investigated in South Africa. An eight-month on-farm growth trial was conducted with sub-adult Haliotis midae (∼43 mm shell length) fed graded levels of kelp in formulated feeds. Kelp inclusion (0.44–3.54% of pellet dry mass) promoted faster growth (65.7–74.5% total mass gain), with better feed and protein conversions (apparent feed conversion ratio [FCR] 1.4–1.8, apparent protein efficiency ratio [PER] 2.3–2.7), as compared with the non-supplemented feed (52.3% total mass gain, FCR 2.1, PER 1.9; p < 0.001). Abalone-gut bacterial DNA was sequenced using 16S rRNA gene pyrosequencing and the sequences were clustered into operational taxonomic units (OTUs) at a 97% similarity level. A supplementary 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) analysis was employed. The dominant OTUs differed in terms of their relative abundances, with an autochthonous Mycoplasma strain being significantly more abundant (p = 0.03) in the gut of abalone fed a kelp-supplemented feed. The DGGE band patterns displayed higher within-group variability for abalone fed the control diet, suggesting that dietary kelp inclusion promotes gut-bacteria homeostasis. This may contribute to better feed utilisation and growth in abalone fed kelp-supplemented feeds.

Evaluation of Soy Protein Concentrate and Meat and Bone Meal as a Replacement for Fish Meal in the Diet of Nile Tilapia Fingerlings

AbstractThis experiment evaluated soy protein concentrate (SPC) and meat and bone meal as a replacement for fish meal protein (FP) in the diet of Nile tilapia fingerlings. Five diets were evaluated including a control diet (50.0% crude protein [CP], of which half the protein came from fish meal [FM]), and four diets in which FM was replaced by increasing amounts of SPC (25.5, 50.0, 75.5, and 100.0%) in combination with meat and bone meal. At the conclusion of a 60‐d growth trial, the following parameters were determined: final weight (FW), final length (FL), weight gain (WG), feed intake (FI), apparent feed conversion (AFC), survival (SUR), and production cost. The estimate of the best replacement value was determined by polynomial regression and the linear response plateau. The results showed significant (P &lt; 0.05) improvement for WG and AFC ratio as FM was gradually replaced by SPC. The parameters FL and FI reached their optimum value at a replacement level of 100% SPC. These results show that it is feasible to use a combination of SPC and meat and bone meal in a balanced feed formulation as an alternative protein source in the diets of Nile tilapia fingerlings.

Pond Culture of Penaeus monodon (Decapoda, Penaeidae) on The Red Sea Area of Sudan

In this study the effect of two stocking densities (3 and 10 post larvae/m2) on the survival, growth performance, and apparent feed conversion ratio of the giant tiger shrimp, Penaeus monodon were evaluated over a period of six months in earthen ponds. The results of the study revealed that the survival rate of shrimps cultured under a low density of 3 PL/m2 (60.0%) was higher than those grown under a high density of 10 PL/m2 (50.5%). The weight gain of the shrimp was better under low density (49.82 g/shrimp) when compared to the group of shrimp grown under high density (35.2 g/shrimp). Apparently, the feed conversion ratios of the two groups grown under the low and high density were similar 3.1 and 3.2 respectively. In conclusion, a stocking density of less than 10 PL/m2 is recommended for culturing P. monodon under the climatic conditions of the Sudanese Red Sea Coast.

Water budgeting in a carp-prawn polyculture system: impacts on production performance, water productivity and sediment stack

This study was designed to quantify the total water requirement and consumptive water use in carp-prawn polyculture system under different water management protocols, using water balance model. Under different water management protocols, treatment-wise estimated total water use, TWU (×104, m3) was 3.7, 4.6 and 3.9, while the computed consumptive water use index, CWUI (m3 kg−1 biomass) was 6.62, 9.31 and 7.08, in T1 (no water exchange), T2 (periodic water exchange) and T3 (regulated water exchange) respectively. Significantly higher yield (P < 0.05) in both T2 and T3 over T1, was probably due to water exchange that improved the rearing environment. Although intensity of water exchange was more in T2, significant variation (P < 0.05) in overall growth and yield was not recorded between T2 and T3. Treatment-wise sediment load ranged between 54.6 and 71.3 m3 t−1 biomasses. Higher sediment load was recorded at lower intensity of water exchange as well as with higher apparent feed conversion ratio. Higher net total water productivity, net consumptive water productivity and OV-CC ratio in T3 infers that regulated water exchange has a distinct edge over the no water exchange protocol. Restricted water use instead of regular/excess water exchange not only improves the production performance and water productivity, but also helps in lessening the operational pumping cost.

Growth and feed utilisation of juvenile greenlip abalone (Haliotis laevigata) in response to water temperatures and increasing dietary protein levels

In this 91-day study, the interaction between four dietary crude protein (CP) levels (27, 30, 33 and 36% CP) and three water temperatures (14, 17 and 20 °C) on the growth and feed utilisation of 6-month old greenlip abalone (Haliotis laevigata) (0.91 g) were investigated. Diets were formulated to be isoenergetic (12.5 MJ kg− 1 digestible energy), containing a lipid level of ~ 3.6% and digestible protein from 17.99 to 28.57%. Abalone were fed to excess at 16:00 h daily, and uneaten feed was collected the following day. The specific growth rate (SGR) of abalone improved significantly as water temperatures increased from 14 to 17 to 20 °C. In addition, apparent protein deposition was significantly higher in abalone at 17 and 20 °C compared to abalone at 14 °C. There was no significant effect of dietary protein level on SGR, but faster growing abalone at 20 °C compensated by consuming more feed when fed low dietary protein levels. In contrast, a significant positive relationship was observed between dietary protein level and feed consumption rate in slower growing abalone at 14 and 17 °C. A non-significant tendency for the apparent feed conversion ratio (FCR) to improve was observed in abalone fed high protein diets at 20 °C, while at 14 °C, abalone had a significantly poorer FCR, especially when fed high dietary protein levels. Based on results from the current study, it is plausible to heat land-based nursery systems in order to gain accelerated growth of juveniles before transfer to grow-out systems. Additionally, no benefits were apparent by feeding abalone high protein diets at 14 or 17 °C, and we therefore recommend a dietary protein level of 29% CP at 14 and 17 °C. While the SGR of abalone at 20 °C was not significantly influenced by dietary protein, the feed consumption rate decreased and there was a tendency for FCR to improve as dietary protein level increased. Therefore, it may be beneficial for abalone to be switched to a diet containing ~ 35% CP at water temperatures > 20 °C.

Feed digestibility and productive performance of bullfrogs raised in cages and fed in different periods and high frequency

Abstract Three feeding frequencies (24, 48 and 96 meals/day) and three feeding periods (daytime, nighttime and daytime/nighttime) were evaluated in this experiment. Bullfrogs ( Lithobates catesbeianus ), with average weight of 78.6 ± 15.7 g, were distributed in 36 pens at a density of 88 frogs/m 2 . The pens, made of polypropylene and screened floor, were installed inside cages, linearly distributed in a 2000 m 2 pond with 5% water renewal. The frogs were fed daily by automatic feeders with extruded commercial feed for carnivore fish. The experiment lasted 90 days, corresponding to the autumn and winter seasons. Feeding frequency and period interacted on the frogs’ average weight (AW) values. At the end of the experiment, in the daytime and daytime/nighttime periods, there was no difference of the AW values between the evaluated feeding frequencies; however, in the nighttime period, the frogs’ AW was greater for the frequency of 48 meals/day. Separately, the feeding frequency and period influenced the result of apparent feed conversion ratio (FCR) which was better with the frequency of 96 meals/day with average value of 2.13, and average value of 2.23 at nighttime. There was no difference between the treatments regarding the coefficient of apparent digestibility of dry matter, crude protein and crude energy. The coefficients of apparent availability of calcium and phosphorus were higher with the feeding frequency of 48 meals/day, regardless of the feeding period. The results showed that bullfrogs can be fed at daytime as well as at nighttime and that the highest feeding frequencies improved FCR in the production of this species. For bullfrog rearing in cages, it is recommended feeding frequency of 96 meals/day at daytime and daytime/nighttime periods and 48 meals/day at nighttime.

Effect of food shortage on growth, energetic reserves mobilization, and water quality in juveniles of the redclaw crayfish, Cherax quadricarinatus, reared in groups

The aim of this study is to analyze the impact of food shortage on growth performance, by means of energetic reserves (proteins, glycogen and lipids) mobilization and hepatopancreas cells analysis in C. quadricarinatus juveniles maintained in groups, as well as the effect on culture water quality. Two experiments were performed, each of them with two feeding regimes during 45 days. The Control feeding regime, in which crayfish were fed daily (once a day) throughout the experimental period (DF), and the Cyclic feeding regime, in which juveniles were fed for 2 or 4 days (once a day) followed by 2 or 4 days of food deprivation (2F/2D and 4F/4D, respectively) in repeated cycles. Cyclic feeding influenced growth, biochemical composition from hepatopancreas and muscle, and water quality. Juveniles cyclically fed were unable to maintain a normal growth trajectory during 45 days. Apparent feed conversion ratio, apparent protein efficiency ratio, hepatosomatic index and relative pleon mass were similar in cyclic and daily fed animals and no structural damage was found in the hepatopancreas of juveniles subjected to cyclic feeding. The novelty of this study was the significant accumulation of proteins in pleonal muscle in both cyclic feeding regimes (approx. 18%) suggesting that the storage of this constitutive material during food shortage may be an adaptation for a compensatory growth when food becomes abundant again. The cyclic feeding regimes had a positive effect on water quality decreasing inorganic nitrogen concentration. This was due to the reduction in the amount of animal excretes and feces in the group that received approx. 50% less feed. Additionally, water pH was higher in cyclic feeding tanks, as a result of lower organic matter decomposition and consequent release of CO2. Accordingly, total ammonia in the water was significantly lower for the cyclic feeding regimes compared to their respective controls. This study suggests that the protocol of cyclic feeding could be applied at least 45 days in 1 g juveniles maintained in group conditions, without affecting the energetic reserves and hepatopancreas structure, emphasizing the high tolerance of this species to food restriction.

Polyculture of frogs and tilapia in cages with high feeding frequency

The polyculture of frogs and tilapia was evaluated in 12 pens made of polypropylene, installed within cages linearly distributed in a pond. 43 bullfrogs (Lithobates catesbeianus) with 79.1±16.9g were distributed in each pen; and 30 tilapia fry (Oreochromis niloticus) with 17.0±1.0g were distributed in each cage. Three feeding frequencies were tested (24, 48 and 96meals/day) and the feed was supplied by automatic feeders. Tilapia were fed only with the leftovers because the feed was supplied just to the frogs. At the end of the experiment (120 days), the average values of the apparent feed conversion ratio (FCR) of the frogs were 2.46, 2.43 and 2.11 for the feeding frequencies of 24, 48 and 96meals/day, respectively; regarding the polyculture, frogs and tilapia together, these values were 1.55, 1.52 and 1.33 for the same frequencies, respectively. The results indicated that the use of high feeding frequency (96meals/day) improved FCR of frogs’ production with consequent reduction of feed waste. The polyculture showed that it is possible to produce frogs in cages sustainably.

Effects of water exchange protocols on water quality, sedimentation rate and production performance ofPenaeus monodonin earthen ponds

This study was carried out in farmers' fields to quantify the total water and consumptive water use in grow-out culture of Penaeus monodon under recommended package of practice with two different water management protocols: T1, with no water exchange and T2, with regulated water exchange. Treatment-wise estimated total water use, was 2.09 and 2.43 ha-m 122 day−1, while the computed consumptive water use index (m3 kg−1 biomass) was 5.35 and 6.02 in T1 and T2 respectively. Lower rates of water exchange (T2) showed significantly improved (P < 0.05) crop performance in terms of performance index (19.75 ± 0.75), production-size index (74.1 ± 3.4), survival rate (80.13 ± 1.7%) and productivity (2.44 ± 0.08 t) over the zero water exchange. The shrimp pond water quality suitability index (WQSI) infers that regulated water exchange (T2) improved the overall suitability of water quality for shrimp culture. WQSI up to 90 days of culture ranged between 7.5–9.0 in T2, needs little management while in the last month of rearing, it was good with moderate management requirements. Treatment-wise sediment load ranged between 50.4–56.3 m3 t−1 shrimp biomass. High intensity of water exchange and low apparent feed conversion ratio influenced in lowering the sedimentation rate. Regulated water exchange protocol (T2) performed well (higher net total water productivity and net consumptive water productivity) against no water exchange (T1). A higher OV:CC ratio (ratio of the output value to the cost of cultivation) indicated that T2 had a distinct edge over the T1 protocol.