Fishmeal availability in the scenarios of climate change: Inevitability of fishmeal replacement in aquafeeds and approaches for the utilization of plant protein sources

Fishmeal is being trusted as the most reliable protein source due to its nutritional quality in terms of attractability, palatability, digestibility, excellent nutrient profiles to fulfil the dietary requirement of aquatic species. The aquaculture sector consumes >70% of global fishmeal, though aqua feeds constitute only 4% in total industrial feed production (900–1,000 Mt in 2018). The global fishmeal production has shown a downward trend of 26.50% during 2000 to 2018 due to the occurrences of El Niño–Southern Oscillationsand other climatic events, which in turn increased the fishmeal price from 452 USD/t (2000) to 1596.54 USD/t (2018). The increasing trend of aquaculture production along with reduced fish‐in/fish‐out ratios (0.63 in 2000 to 0.33, 0.22 in 2010 and 2015 respectively) indicates the resilience of the aquafeed sector for fishmeal replacement. The wide availability, reasonable price and reliable nutrient content made an interest in plant protein sources, but their utilization was limited due to poor digestibility, imbalanced profiles of essential nutrients and the presence of anti‐nutrients. Numerous methodologies are invented in recent times to enrich the nutritional qualities for maximizing the utilization of plant proteins in aquafeed formulations. The present review concludes that the aquafeed sector should use climate economics and technological innovations for substituting fishmeal to formulate the cost‐effective feeds.     

Aspergillus niger fermented plant protein mix as a potential substitute for fishmeal in the diet of Penaeus vannamei (Boone, 1931)

A 45‐day feeding trial was conducted to evaluate the utilization of fermented plant protein mix (FPPM) as a fishmeal substitute in the diet of Penaeus vannamei. Six isonitrogenous and isolipidic diets were formulated by substituting fishmeal at 0% (control), 50%, 60%, 70%, 80% and 90% (FR‐0, FR‐50, FR‐60, FR‐70, FR‐80 and FR‐90, respectively) using FPPM. Shrimps fed with diets FR‐50, FR‐60 and FR‐70 had no significant difference in weight gain (173.22%–178.07%) with the control group (179.50%). However, the broken‐line regression indicated that 70.8% fishmeal could be substituted by FPPM. The trend of digestibility was reflected in growth performance. Survival had no significant difference among the treatments. Fishmeal substitution had significant (p < .05) variations in protease and amylase activity, but not in lipase. Except lipid, other body composition was not affected due to dietary change. A decrease (p < .05) in haemolymph total protein, cholesterol and triglycerides was observed to increase in fishmeal substitution. A higher fishmeal substitution (FR‐90) had significantly (p < .05) lower total haemocyte count and the reverse was true for phenoloxidase. Results conclude that a combination of fermented ingredients would be more effective rather using alone in shrimp feed, with a great potential in reducing the pressure on fishmeal.     

Apparent digestibility coefficients of fungal fermented plant proteins in two different penaeid shrimps—A comparative study

Using the 70:30 replacement method and chromium as an inert marker, the digestibility of four fermented oilseed meals/cakes (soybean meal (FSBM), groundnut oil cake (FGNC), rapeseed meal (FRSM), and sunflower oil cake (FSFC)) were determined in Penaeus monodon and Penaeus indicus. Apparent dry matter digestibility (ADMD) of fermented ingredients was ranked as FSBM > FGNC > FRSM > FSFC. The critical variations in apparent protein digestibility (APD) in P. monodon (0.816%) and P. indicus (0.608%) were lower than the ADMD. Appaprent amino acid digestibility (AAD) was >90% in FSBM for both the species and was lower for other ingredients. Protein had a higher digestibility than total amino acids and was in the range of 0.69%–2.71% in P. monodon and 0.32%–2.75% in P. indicus. A correlation between the ADC of total amino acids and protein was found to be r = 0.8229 in P. indicus and r = 0.7447 in P. monodon. Data were further subjected to two way analysis of variance for assessing the digestibility variations between the species. It was observed that P. indicus had higher values of ADMD than P. monodon in FSBM (2.97%) and FRSM (1.22%) and the reverse was true in FGNC and FSFC. The APD was high in P. indicus for FSBM, FGNC and FRSM but not for FSFC. However, significant variations could be noticed in AAD between the species.     

Effect of fungal fermentation on apparent digestibility coefficient for dry matter,crude protein and amino acids of various plant protein sources in Penaeus vannamei

Four commercial solvent‐extracted oilseed meals/cakes, viz. soybean meal (SBM), groundnut oil cake (GNC), rapeseed meal (RSM) and sunflower oil cake (SFC), were fermented with fungus Aspergillus niger, and its effect on apparent digestibility coefficient (ADC) was studied in Penaeus vannamei. Reference diet and eight experimental diets containing 700 g/kg reference diet and 300 g/kg test ingredient with 5 g/kg chromic oxide were formulated. Each diet was randomly allotted to three tanks containing ten shrimps. Shrimps were adapted to the experimental diets for a week, and faeces were collected using Falcon tube from second week onwards. The ADC of all the ingredients significantly (p < .05) increased with fermentation and the increase being higher in SBM (78.46%–91.71%) for dry matter and in SFC (71.51%–87.02%) for protein. Analysis of variance showed that the ADC of both dry matter and protein significantly (p < .05) differed in treatments (p = <.001) and ingredients (p = <.001). The average ADC of ingredients was ranked as SBM > GNC > RSM > SFC. The most digestible essential amino acid (EAA) in fermented ingredients was methionine in SBM, arginine in GNC, valine in RSM and histidine in SFC. A better improvement in amino acid digestibility was observed in fermented SFC. Results indicated that P. vannamei efficiently digests fermented ingredients compared to unfermented ones.     

Fungus,Aspergillus niger,fermented groundnut oil cake as a fishmeal alternative in the diet of Penaeus vannamei

Commercial de‐fatted groundnut oil cake (GNC) fermented with the fungus Aspergillus niger was evaluated as a fishmeal alternative in the diet of Penaeus vannamei. A 45‐day growth trail was performed using nine iso‐nitrogenous and iso‐lipidic diets. Untreated/fermented GNC was included at the rate of 0 (control), 25, 50, 75 and 100 g/kg by replacing fishmeal (w/w). Each diet was randomly assigned to triplicate group of 20 shrimps (initial weight of 3.09 ± 0.03 g). Results revealed that shrimp fed with diets having untreated GNC up to 50 g/kg has no significant difference in growth, whereas the inclusion level was enhanced to 100 g/kg with fermented GNC with no deleterious effect. The negative linear trend was found for SGR with increasing the inclusion of both untreated and fermented GNC. The feed and protein efficiency measures, viz. feed conversion ratio, protein efficiency ratio and apparent protein utilization, were better in shrimps fed with diets having fermented GNC than those fed the respective level of untreated GNC. The broken‐line analysis indicated that the inclusion of 72.5 g/kg fermented GNC showed the best FCR. No significant difference was observed in survival (86.67%–96.67%) between the dietary treatments. There was a significant difference in ether extract of shrimp between the treatments, whereas other parameters were not affected. Haemolymph indices showed a significant difference in total protein, glucose, cholesterol and triglycerides between control and test diets. The results conclude fermented GNC, which can be better than untreated one in the diet of shrimp.     

Effect of dietary protein level on fattening and mineral profiles of mud crab,Scylla serrata,in individual cages under mangrove ecosystem

A fattening demonstration was carried out in Sorlagondi (15.8640⁰N, 80.9671⁰E) mangrove ecosystem in Diviseema region, Krishna district, Andhra Pradesh, India, by adapting a holistic approach of “Integrated Mangrove Fishery Farming System.” The local Yanadi tribal communities engaged in mangrove afforestation programmes were provided with 144 individual crab fattening cages (60 × 40 × 30 cm). Two formulated feeds were prepared with two levels of protein (32% and 36%) and were tested on fattening of the marketable size (200–1,000 g) of mud crabs, Scylla serrata. Significantly (p < 0.05) higher weight gain, feed and protein efficiency measures were observed in crabs fed with CP‐36% diet across all size groups. This diet also reduced the time (days) taken for fattening crabs irrespective of the size. Moisture content was very high in soft crabs (>800 g/kg) compared with hard crabs (679.70–688.65 g/kg), whereas the reverse trend was observed for protein, ether extract and ash content. Both diet and size of the crab have not shown much influence on proximate composition. However, cultured hard crabs had higher ether extract (20.10 g/kg) than wild hard crabs (17.06 g/kg). The changes in concentration of mineral values on wet basis indicated the increase in concentration in hard crabs compared with soft crabs, whereas when the percentage change, values on dry matter basis indicated the reduction in concentration of mineral contents of K, Na, P, Cu, Fe and Zn. This higher concentration of minerals in soft crabs could possibly be attributed to the reabsorption of minerals into soft muscle or to the body fluids.     

Enhancing the dietary value of palm oil in the presence of lysolecithin in tiger shrimp, <Emphasis Type="Italic">Penaeus monodon</Emphasis>

The effect of four iso-nitrogenous and iso-lipidic diets containing soy lecithin and lysolecithin with fish oil (sardine) and palm oil on growth, digestibility, and fatty acid composition of tail muscle and non-muscle portions of tiger shrimp, Penaeus monodon, was evaluated. Shrimp fed with lysolecithin diets had significantly (P?<?0.05) higher daily growth coefficient values (1.40–1.45% day^?1) than those fed with soylecithin containing diets (1.32–1.37% day^?1). Correspondingly, lysolecithin-supplemented diets showed significantly higher (P?<?0.05) apparent digestibility coefficients (ADC) of fatty acids with both the oils due to higher emulsification ability of small micelle forming by lysolecithin. However, there were no significant differences in survival and FCR among all treatments. The fatty acid composition of the test diets reflected to a certain extent in the fatty acid composition of the muscle and non-muscle portions of shrimp. Arachidonic, eicosapentaenoic, and docosahexaenoic acid contents of muscle and non-muscle portions of shrimp were significantly (P?<?0.05) higher in lysolecithin-supplemented diet compared to soylecithin-supplemented diet. The present results suggest that lysolecithin improved the fatty acid digestibility with its high emulsification properties that reflected in better performance by improving dietary value of palm oil.