Effect of dietary carbohydrate to lipid ratio on performance of Nile tilapia and enhancement of natural food in pond aquaculture

This study tested the effect of two diets differing in carbohydrate to lipid (CHO:LIP) ratio (4.7 vs. 19.5 g/g) on the contribution of natural food and the total fish production in tilapia ponds. Eight ponds, each divided into three equally sized compartments, were assigned to one of the two diets, which differed in CHO:LIP ratio but had the same digestible protein to digestible energy (DP:DE) ratio (15.5 and 15.6 g/MJ). Ponds were fed equal amounts of crude protein. Three feeding levels (no, low and high) were nested in each pond in a split plot design. Average body weight of fish at stocking was 90 g, and the duration of the experiment was 42 days. Increasing the CHO:LIP ratio had no impact on tilapia production. However, the feeding level influenced both biomass gain, specific growth rate and survival. The apparent digestibility coefficient (ADC) for fat and carbohydrate was influenced by dietary CHO:LIP ratio but ADC for energy was unaffected. Proximate analysis of fish body composition showed no effect of diet except for levels of ash. Diet had no effect on the organic matter composition of the faeces, and the contribution of natural food to fish nitrogen gain. Therefore, we postulate that changing the dietary non-protein energy source from lipid to carbohydrate does not have any impact on tilapia culture in semi-intensive ponds.</p

Ideotyping integrated aquaculture systems to balance soil nutrients

Due to growing land scarcity and lack of nutrient inputs, African farmers switched from shifting cultivation to continuous cropping and extended crop area by bringing fragile lands such as river banks and hill slopes into production. This accelerated soil fertility decline caused by erosion, harvesting and insufficient nutrient replenishment. We explored the feasibility to reduce nutrient depletion by increasing nutrient utilization efficiencies, while diversifying and increasing food production through the development of integrated aquaculture – agriculture (IAA). Considering the climatic conditions prevailing in Kenyan highlands, aquaculture production scenarios were ideotyped per agro-ecological zone. These aquaculture production scenarios were integrated into existing NUTrient MONitoring (NUTMON) farm survey data for the area. The nutrient balances and flows of the resulting IAA-systems were compared to present land use. The effects of IAA development on nutrient depletion and total food production were evaluated. With the development of IAA systems, nutrient depletion rates dropped by 23–35%, agricultural production increased by 2–26% and overall farm food production increased by 22–70%. The study demonstrates that from a bio-physical point of view, the development of IAA-systems in Africa is technically possible and could raise soil fertility and total farm production. Further studies that evaluate the economic feasibility and impacts on the livelihood of farming households are recommended

Constraints on Energy Intake in Fish: The Link between Diet Composition, Energy Metabolism, and Energy Intake in Rainbow Trout

The hypothesis was tested that fish fed to satiation with iso-energetic diets differing in macronutrient composition will have different digestible energy intakes (DEI) but similar total heat production. Four iso-energetic diets (2×2 factorial design) were formulated having a contrast in i) the ratio of protein to energy (P/E): high (HP/E) vs. low (LP/E) and ii) the type of non-protein energy (NPE) source: fat vs. carbohydrate which were iso-energetically exchanged. Triplicate groups (35 fish/tank) of rainbow trout were hand-fed each diet twice daily to satiation for 6 weeks under non-limiting water oxygen conditions. Feed intake (FI), DEI (kJ kg−0.8 d−1) and growth (g kg−0.8 d−1) of trout were affected by the interaction between P/E ratio and NPE source of the diet (P<0.05). Regardless of dietary P/E ratio, the inclusion of carbohydrate compared to fat as main NPE source reduced DEI and growth of trout by ∼20%. The diet-induced differences in FI and DEI show that trout did not compensate for the dietary differences in digestible energy or digestible protein contents. Further, changes in body fat store and plasma glucose did not seem to exert a homeostatic feedback control on DEI. Independent of the diet composition, heat production of trout did not differ (P>0.05). Our data suggest that the control of DEI in trout might be a function of heat production, which in turn might reflect a physiological limit related with oxidative metabolism

The Biology and Economics of Coral Growth

To protect natural coral reefs, it is of utmost importance to understand how the growth of the main reef-building organisms—the zooxanthellate scleractinian corals—is controlled. Understanding coral growth is also relevant for coral aquaculture, which is a rapidly developing business. This review paper provides a comprehensive overview of factors that can influence the growth of zooxanthellate scleractinian corals, with particular emphasis on interactions between these factors. Furthermore, the kinetic principles underlying coral growth are discussed. The reviewed information is put into an economic perspective by making an estimation of the costs of coral aquaculture

White spot syndrome virus (WSSV) risk factors associated with shrimp farming practices in polyculture and monoculture farms in the Philippines

White spot sydrome virus (WSSV) is one of the most important viral disease of shrimp. Several studies to control the disease have been done. Tank experiments identified WSSV risk factors related to the physico chemical properties of the water. A few studies reported pond level WSSV risk factors. This study identifies the risk factors associated with essentially two different farming systems: polyculture and semi-intensive monoculture of Penaeus monodon. Data were gathered from a total of 174 shrimp farmers in eight provinces of the Philippines using a structured questionnaire. Forty-seven variables related to pond history and site description, period of culture, pond preparation techniques, water management, culture methods, feed and other inputs, and biosecurity measures were investigated. In the analysis for combined monoculture and polyculture farms, feeding live molluscs was identified as important WSSV risk factors. In addition to feeding live molluscs, sharing of water source with other farms, having the same receiving and water source, larger pond size, and higher stocking density were identified as important WSSV risk factors in monoculture farms. Climate, i.e. stocking during the cold months and sludge removal and its deposition on the dikes were identified as WSSV risk factors in polyculture farms. Protective factors, listed in decreasing significance, were feeding with planktons and high mangrove to pond area ratio, both observed in the dataset with both monoculture and polyculture farms, while only the latter was observed in the dataset for monoculture farms only. No protective factor was observed in the dataset for polyculture farms. This study confirmed the negative effect of sharing water source with other farms and identified several new factors influencing WSSV infection such as feeding live molluscs increases the risk, while feeding with planktons and high mangrove to pond area ratio reduce the risk.The authors wish to acknowledge the funding support of the Government of Japan under the trust fund granted to SEAFDEC AQD (study code: GoJ TFD FH0206) and RESCOPAR, Wageningen University, the Netherlands. Our gratitude also goes to those who supported and assisted in the conduct of the survey−Dr. John Albaladejo and staff: Ruel, Pepe, and Wetet; Mr. Andres Bojos and staff: Carol, Tetet, Joy, Jonah, Renren and Nong Nards; Dr. Gigi Carillo and staff: Ron, Mel, Johnel, Elsie, Bart, and Guada; Bong and Roselyn; Mr. Rey Cawaling, and Ms. Sarah Fedelicio; and to the shrimp farmers of Aklan, Antique, Bohol, Bulacan, Cebu, Leyte, Negros and Northern Samar who willingly and unselfishly shared their experiences

WSSV risk factors related to water physico-chemical properties and microflora in semi-intensive Penaeus monodon culture ponds in the Philippines

Whitespot syndrome virus, WSSV, is the most important among the shrimp diseases. One of the suggested WSSV risk factors is the occurrence of stress since stressors could compromise the shrimp defence system thus increasing the risk of WSSV infection. Stressors are usually related to the physico-chemical properties of both water and pond bottom. This paper investigates the effect of some biotic and abiotic components of the pond ecosystem on WSSV infection and outbreak. Water physico-chemical properties and microflora of 91 production cycles of 8 semi-intensive shrimp farms were analyzed to determine WSSV risk factors, using factor analysis and logistic regression. Fluctuations of temperature and pH are important risk factors that will result to an infection but not necessarily to an outbreak. Exposure to high salinity and high temperature are important factors for an infection to result to an outbreak. The risk of an infection is reduced when the water temperature is high, salinity fluctuations are small, and percentage of yellow Vibrio colonies is greater than the green ones. Further studies are needed to clarify the effects of water depth, water transparency, and various bacterial counts; these factors could be individual or interactive.The authors wish to thank the Government of Japan for funding the study under the trust fund granted to SEAFDEC (GoJ TFD FH0206)

Formulation and measured nutrient composition of experimental starch (SD) and fat diet (FD).

1<p>Starch diet.</p>2<p>Fat diet.</p

Relative water flux [ml g⁻¹ ingested DM]

<p>(<b>Means±SE</b>)<b>.</b> Measured in the stomach (A), proximal intestine (B), mid intestine (C) and distal intestine (D) of African catfish (<i>Clarias gariepinus</i>) at 2, 5 and 8 h after feeding a starch (SD) or fat (FD) diet. A 2-Way ANOVA (<i>p</i><0.05, Tukey) was used to detect the effects of diet (D), time (T) and the diet*time interaction (D*T) within compartments. Effects are marked with ns for non-significant; # <i>p</i><0.10; * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001. Means (<i>n</i> = 2) within compartments marked with different letters are significantly different from each other (<i>p</i><0.05).</p

Relative water flux in proximal intestine and stomach [ml g⁻¹ DM].

<p>Relative water flux in the proximal intestine vs. Relative water flux in the stomach of African catfish (<i>Clarias gariepinus</i>) measured at 2, 5 and 8 h after feeding a starch (SD) or fat (FD) diet. The estimated linear models are given in the text. No significant differences were detected between intercepts (<i>p</i> = 0.962) or slopes (<i>p</i> = 0.959) of the linear models (One-Way ANCOVA, <i>n</i> = 2, <i>p</i><0.05).</p

Dry matter

<p>(<b>DM</b>) <b>content of chyme [g kg⁻¹]</b> (<b>Means±SE</b>)<b>.</b> Measured in the stomach (A), proximal intestine (B), mid intestine (C) and distal intestine (D) of African catfish (<i>Clarias gariepinus</i>) at 2, 5 and 8 h after feeding a starch (SD) or fat (FD) diet. A 2-Way ANOVA (<i>p</i><0.05, Tukey) was used to detect the effects of diet (D), time (T) and the diet*time interaction (D*T) within compartments. Effects are marked with ns for non-significant; # <i>p</i><0.10; * <i>p</i><0.05; ** <i>p</i><0.01; *** <i>p</i><0.001. Means (<i>n</i> = 2) within compartments marked with different letters are significantly different from each other (<i>p</i><0.05).</p