Increasing Stocking Density Research Articles

Yerleşim Sıklığının Sprague Dawley Ratlarda Büyüme Performansı, Bazı Serum Oksidatif ve Nitrosatif Stres Parametreleri Üzerine Etkisi

Objective of his studywas to compare the growth performances of Sprague-Dawley female rats fed at normal and narrowed stocking density with certain stress parameters. 72 Sprague-Dawley female rats aged 4 weeks were used in the experiment. The average live weight per trial for normal and narrow stock density groups was calculated as 54.22 ± 2.65 and 55.53 ± 2.66 g. Animals’ weekly weighs during a month indicated that as their weight increased, the floor area per animal gradually expanded. Female rats reach sexual maturity at 8-9 weeks. For this reason, the experiment was continued until the animals were 2 months old. Based on the weekly weighing results of the rats, it was found that live weights increased regularly for both groups and growth performances did not change according to stocking density (P>0.05). It was concluded that serum Total Antioxidant Capacity (TAC) and Glutathione (GSH) values were affected by the stocking density and that significantly reduced in the rats fed at narrowed stocking density. On the other hand, Total Oxidant Capacity (TOC), Nitric Oxide (NO) and malondialdehyde (MDA) values increased approximately 1.5 times in the rats at the group of narrowed stocking density. As a result, it was found that even if the increasing stocking density has no negative effect on the growth performance of the animals, it causes some physiological changes in blood values by stressing the animals. Therefore, in order to get the most accurate results in scientific studies, it must be paid attention to breed the animals at the ideal housing conditions.

Effect of stocking density on growth and yield of Labeo bata fingerlings reared in cages

An experiment was carried out to evaluate the growth performance and yield of Labeo bata reared in cages at different stocking densities in a floodplain wetland of Assam, India. Fifteen cages (effective water volume 40 m3 each) installed in the wetland were stocked with fingerlings of L. bata (mean length 8.20 ± 0.08 cm; mean weight 4.82 ± 0.13 g) at five different stocking densities, i.e., 25 (D25), 50 (D50), 75 (D75), 100 (D100) and 150 fingerlings m−3 (D150) in triplicates. Fish were fed with pelleted feed containing 30 % CP at 3–5 % body weight twice-a-day for six months. Specific growth rate of the reared fish recorded at different stocking densities were 1.08 ± 0.03, 0.89 ± 0.01, 0.90 ± 0.05, 0.77 ± 0.02 and 0.57 ± 0.02 % day-1, respectively, in D25, D50, D75, D100 and D150. The corresponding weight gain percent were 604.77 ± 35.63, 395.37 ± 11.32, 407.88 ± 44.91, 296.61 ± 13.07 and 180.70 ± 11.02. In general, growth performance of the reared fish was inversely proportional to stocking density. However, yield (biomass) increased with increase in stocking density of up to 75 fingerlings m-3 after which no significant increase was observed. Economics of the cage aquaculture system also showed highest net revenue and benefit-cost ratio at 75 fingerlings m-3. Rearing of fish at this stocking density yielded 50 % higher fish production and generated 92.5 % higher net revenue than rearing at the lowest stocking density. The results suggest 75 fingerlings m-3 as the optimum stocking density for rearing L. bata in net cages.

NILE TILAPIA NURSERY IN A BIOFLOC SYSTEM: EVALUATION OF DIFFERENT STOCKING DENSITIES

This trial aimed to evaluate the growth performance and hematological parameters of Nile tilapia (Oreochromis niloticus) GIFT strain during nursery using different stock densities in a biofloc system. The experiment was conducted in circular tanks (400 L) with sexually reversed fish, weighing 6.74 ± 0.37 g, over a period of 35 days. Five treatments with three replicates each were used in a completely randomized design. The treatments were as follows: T1 (200 fishes m-3); T2 (300 fishes m-3); T3 (400 fishes m-3); T4 (500 fishes m-3), and T5 (600 fishes m-3). The fishes were fed four times a day, following a feed table for this species, with adjustments according to fish biomass. The water quality parameters total ammoniacal nitrogen, and unionized ammonia showed a significant difference (p<0.05) between the treatments with lower (T1) and higher stocking densities (T4, T5). Alkalinity was significantly higher in treatments with higher densities (T4 and T5). For hematological parameters, the number of thrombocytes was higher in T5. Hemoglobin concentration was significantly lower in T5 than in T3. The best productive indexes were found in T4, presenting final biomass of 9915.16 ± 14.80 g m-3, apparent feed conversion rate of 1.11 ± 0.02, mean survival of 95.75 ± 0.75%, and daily mean weight gain of 0.43 ± 0.07 g. Overall, the Nile tilapia nursery in a biofloc system showed higher individual growth at densities up to 300 fishes m-3 and increased stocking density up to 500 fishes m-3.

Growth and Economics of Silver Barb (Barbonymus gonionotus) in Rice-fish-vegetable Integrated Culture System at Different Stocking Densities in a Rainfed Arid Zone

Sustainable integrated farming involving the combination of rice-fish-vegetables requires advanced technology to be adopted in crop production in arid zones characterized by red or yellow soil. In the present study, we used suitable and varying stocking densities of Silver barb (Barbonemus gonionotus) and evaluated in a structured production and economic framework under four treatments (T1, T2, T3, and T4) assigned with a stocking density of 10, 20, 30 and 40 fish/decimal, respectively. We used standard methods of water, soil, and plankton monitoring of the rice field. The study showed that lower stocking density provided the fish with more spaces and less competition for food resulting in higher growth performance in T1 compared to other treatments. Although stocking density did not show any significant (P>0.05) effect in rice, straw and vegetable production in all the treatments, the highest rice and straw production at T4 could be ascribed to the improvement in soil fertility by the accumulation of fish excreta and subsequent release of nutrients from the soil by the higher number of fish in that treatment. The best fitted polynomial regression line obtained between gross yield and net yield with different stocking densities of Silver barb described an inevitable fluctuation in net yield of fish with increasing stocking density. Despite the stable growth performance of fish in T1, a combined effect of lower total input cost, higher yield of fish and rice, and economical vegetable production, T2 showed a significantly (P<0.05) higher total return. Furthermore, the benefit-cost ratio (BCR) for rice-fish-vegetables integrated culture system in the rain-fed rice field was also high. In conclusion, this study revealed that maintaining a stocking density of 20 fish/decimal was economically profitable for rice-fish-vegetables integrated culture systems in arid zones on a global scale.

Polyculture culture of black tiger shrimp Penaeus monodon and red seaweed Gracilaria tenuistipitata under different densities: effects on water quality, post-larvae performance and their resistance against Vibrio parahaemolyticus

The integration of seaweeds (extractive, low-footprint species) into aquaculture systems has been considered an alternative approach for the sustainable development of the shrimp industry, which aims to expand in an environmentally friendly way. Two consecutive experiments were conducted to evaluate the effects of integrating various densities of black tiger shrimp Penaeus monodon post-larvae (PL) and red seaweed Gracilaria tenuistipitata on water quality and shrimp performance in the nursery phase. The first experiment involved a 3 × 4 factorial design with three levels of shrimp density (1000; 2000 and 3000 PL m−3) and four levels of red seaweed density (0, 1.0, 1.5 and 2.0 kg m−3) randomly allocated in triplicate tanks for 30 days. Shrimp PL (with a mean weight of 0.012 ± 0.002 g and length of 1.12 ± 0.09 cm) and red seaweed were reared in 150 L tanks at a salinity of 15 g L−1. Significant synergistic effects between shrimp and seaweed densities were observed for the NO3− total nitrogen (TN) and PO43− contents, as well as for the survival (p < 0.05) and production of shrimp (p < 0.01). The integration of shrimp and red seaweed significantly decreased the concentrations of nitrogen and phosphorus in the rearing tanks and greatly enhanced the survival and growth rate of shrimp. In particular, increased stocking density resulted in poorer growth performance but enhanced production. Applying stocking densities of 1000 and 2000 PL m−3 obtained larger shrimp size, while a density of 3000 PL m−3 achieved the highest production output in the integrated system. In the second experiment, which followed the 30-day growth trial, shrimp quality was assessed via an immersion challenge test using pathogenic Vibrio parahaemolyticus (a concentration of 2 × 108 CFU mL−1) on the shrimp groups previously stocked at a density of 3000 PL m−3 and integrated with different quantities of seaweed. After 14 days of challenge, the cumulative mortality in the monoculture system averaged 75.6%, which was significantly higher (p < 0.05) than those in the integrated groups (17.8–31.1%). It is concluded that the integration of P. monodon shrimp and G. tenuistipitata improved tank water quality as well as shrimp survival and growth while also enhancing the antibacterial activity of shrimp against V. parahaemolyticus infection in the nursery phase.

The influence of density and dominance on Pacific white shrimp (Litopenaeus vannamei) feeding behaviour

Identifying correct stocking densities is an important concern for shrimp farming especially when intensification of shrimp production is growing in order to meet increasing demand. Increased stocking densities generate greater competition among individuals, reduced feeding efficiencies and increased water degradation. Little is known, however, about the effects of stocking density on feeding behaviour and conspecific interactions in commercial shrimp species. Therefore, the aim of the present study was to investigate the effects of density and dominance hierarchies on the feeding behaviour of Pacific white shrimp (Litopenaeus vannamei). Juvenile shrimp (7.91 ± 1.81 g, n = 56) were divided into three density treatments (low: 6.2 shrimp/m2, medium: 12.4 shrimp/m2 and high: 24.8 shrimp/m2) with four groups at each density. Groups of shrimp were placed with feed in test arenas and recorded for 20 min, with each group recorded eight times on consecutive days. Video analysis was conducted via automated observation using EthoVision tracking software. Dominance hierarchies were observed within each group and were found to remain stable across observations. Therefore the effect of dominance on feeding behaviour was investigated via comparisons of behaviour of the most dominant and subordinate shrimp in each group. Results showed a clear effect of both density and dominance on L. vannamei feeding. A greater relative feed consumption was observed in shrimp at the high density, even though less time was spent on the feeding area due to space limitations on the feeding tray. Lowest levels of feeding activity were found in the low-density treatments, coupled with higher levels of exploratory behaviour (i.e. moving, distance and velocity) indicative of a reduced feeding motivation. Smaller distances and extended contact times between individuals were found with increasing density. Dominance influenced feeding behaviour; subordinates spent longer on the feeding area whereas dominants explored the test arena more, however, these differences were minimised at high density. Findings from this study therefore revealed how L. vannamei at high density (24.8 shrimp/m2) maximized feeding behaviours while minimising feeding inefficiencies due to dominance interactions. The study also showcased tracking shrimp feeding behaviour automatically at a group level.

Influence of Photoperiod and Rearing Density of Fry in Production of Stunted Fingerlings of Catla catla (Hamilton)

Background: Seed stunting is a process of suppressing the normal growth of fish by manipulating various factors affecting the growth process. The present study aimed at evaluating the influence of varied photoperiod and stocking density on the growth and survival of catla (Catla catla) during the stunting process. Methods: Five treatments including control were used in triplicate and stocked with catla fry (0.84 g, 38.8 mm). Control, T-1 and T-2 groups were stocked with fry at 20 m-3 densities and maintained at 12 hours light and 12 hours darkness (12L:12D), 6L:18D and 0L:24D, respectively to study the influence of varied photoperiod. T-3 and T-4 were stocked with fry at 30 and 40 m-3 densities respectively to study the effect of crowding on the growth. Control at 20 m-3 density and 12L:12D photoperiod served as control for both the studies. Result: There was a significant reduction in the survival, harvested body weight, total length and specific growth rate in the treatments T-1 and T-2 as compared to the control (P less than 0.05). Though these attributes were statistically similar (P greater than 0.05) between T-1 and T-2, the values were relatively higher in T-1 suggesting considerable photoperiod effect on fish growth. Similarly, the HBW, total length and SGR significantly reduced from T-3 to T-4 with increased density depicting effect of crowding on growth. Such results indicated that both increased stocking density and decreased photoperiod lead to growth suppression and can be used as tools for seed stunting in catla.

Effect of understocking density of channel catfish fingerlings in intensively aerated multiple‐batch production

AbstractMultiple‐batch production is the most widely practiced method of raising channel catfish. Producers are increasingly adopting intensified production practices in multiple‐batch systems by increasing stocking density and aeration rates as a means to improve cost efficiencies. Proven stocking recommendations are required for the efficient implementation of recent developments in multiple‐batch production. Twelve 0.4‐ha ponds were understocked with 17,484, 20,612, and 26,124 fingerlings/ha (mean weight = 40 g/fish) over equal weights of carryover fish (0.46 kg/fish @ 4,589 kg/ha). Fish were fed once daily to apparent satiation with a 28% protein floating feed and aerated with a single 7.4‐kW electric paddlewheel aerator. Density‐dependent significant differences were absent for gross, net, daily net yields, marketable yields (≥0.54 kg), growth (g/day), and survival. Sub‐marketable yield (&lt;0.54 kg) and feeding rate increased significantly with increased understocking density. Economic analysis revealed increased breakeven prices and diminished net returns with increased stocking density when sub‐marketable fish were not considered as revenue. These differences in production costs and profits among the three treatments became minimal when sub‐marketable fish were included as revenue. All three density treatments attained positive annual net cash flows. This study validates channel catfish understocking densities of 17,000–26,000 fish/ha to improve cost efficiency in intensively aerated, multiple‐batch production systems.

Climate mitigation and intensified forest management in Norway: To what extent are surface waters safeguarded?

While the role of forestry in mitigating climate change is increasingly subject to political commitment, other areas, such as water protection, may be at risk. In this study, we ask whether surface waters are sufficiently safeguarded in relation to the 2015 launch of a series of measures to intensify forest management for mitigation of climate change in Norway. First, we assess how impacts on water are accounted for in existing regulations for sustainable forestry. Secondly, we provide an overview of the impacts of forestry on water quality relevant to three support schemes: afforestation on new areas, increased stocking density in existing forests, and forest fertilisation. Lastly, we assess the uncertainties that exist with regard to surface waters in the implementation of these measures. We find that the safeguards in place are adequate to protect water resources at the point of initiation, but there is a large degree of uncertainty as to the long-term effect of these mitigation measures.

Effects of stocking density on growth, serum parameters, antioxidant status, liver and intestine histology and gene expression of largemouth bass ( Micropterus salmoides ) farmed in the in‐pond raceway system

In China, the in-pond raceway system (IPRS) recirculating culture is a new model of freshwater aquaculture. A 120-day feeding study was carried out to evaluate the influence of stocking density on growth, digestive enzymes activity, serum parameters, antioxidant status, liver and intestine histology and gene expression of HSP70 and Cu/Zn-SOD of largemouth bass farmed in IPRS. Largemouth bass, Micropterus salmoides (initial body weight, 4.50 ± 0.23 g), were randomly farmed in nine raceways stocked at three stocking densities of 0.2 (LSD), 0.4 (MSD) and 0.6 (HSD) kg/m3, and sampled at 30, 60, 90 and 120 days. The results showed that body weight, specific growth rate and weight gain of fish farmed at MSD group were higher than that farmed at LSD and HSD treatments on 30 days (p < 0.05), while fish farmed at MSD and HSD treatments had significantly lower growth than those farmed at LSD groups on 90 and 120 days (p < 0.05). There were no significant differences in serum cortisol, glucose and triglyceride levels among three groups on 30, 60 and 90 days (p > 0.05), whereas fish farmed at HSD group had significant higher values than that farmed at LSD group on 120 day (p < 0.05). There were no significant differences in serum lysozyme level on day 30, while it decreased with increasing stocking densities on after day 60. Fish reared at LSD group had significantly higher SOD activities than those farmed at MSD and HSD treatments, and had significantly higher CAT activities than those farmed at HSD group on 120 day (p < 0.05). MDA level increased with increasing stocking density on days 60, 90 and 120 (p < 0.05). Fish farmed at HSD group had significantly higher liver HSP70 mRNA levels on days 90 and 120 (p < 0.05). Cu/Zn-SOD mRNA levels showed a downward trend. No significant difference was observed on liver and intestine histology (p > 0.05). In conclusion, largemouth bass farmed at 0.4 kg/m3 had better growth and health status before days 30. After that, fish farmed at higher stocking densities in IPRS would inhibit growth and reduce immune function.

Effects of different stocking densities on Nile tilapia performance and profitability of a biofloc system with a minimum water exchange

The determination of an optimum stocking density should be obtained according to a complex assessment, in which growth performance, water quality, animal welfare, and production costs need to be considered. In this context, the objective of this work was to evaluate different stocking densities of Nile tilapias in biofloc technology (BFT) with minimal water renewal. Six hundred masculinized Nile tilapia juveniles with an initial average weight of 133.91 g were evaluated at four different stocking densities (18.75, 37.50, 56.25, and 75.00 fish‧m−3) and four replications, during 260 days of trial. The increase in stocking density resulted in a reduction of DO and pH. The minimum water renewal at a rate of 5%‧day−1 promoted an average reduction of settleable solids in the system of 23.75% at each discharge. The final biomass followed a quadratic regression on the stocking density, with a maximum at 72.27 fish‧m−3 or 36.86 kg‧m−3. However, the greatest daily weight gain (2.84 g‧day−1) that resulted in the highest average final body weight (842.26 g) was obtained at the lowest stocking density. We did not obtain any significant differences in body composition. The biofloc, on the other hand, had lower ash content and higher gross energy in the high stocking densities. Regarding gill morphometry, we found a greater number of branchial lesions in the highest and lowest stocking density evaluated. By an economical assessment, if the sales price is influenced by the final body weight, the reduced average harvest weight in higher stocking densities could lead to low profitability or even financial loss. Therefore, it is concluded that the use of intermediate stocking density, around 33 fish‧m−3, has higher profitability since it produces a large proportion of harvested fish that reach high body weights, and possible high selling prices, combined with desirable biomass.

Effect of selenium sources in plant-based diets on antioxidant status and oxidative stress-related parameters in rainbow trout juveniles under chronic stress exposure

Selenium (Se) is an essential micronutrient required for normal development and antioxidant protection. Oxidative stress induced by stressful conditions has been shown to be reduced by dietary Se supplementation. However, replacing fishmeal, an important source of Se, with ingredients of plant origin usually results in decreased Se content in aquafeeds. The objective of the study was hence to assess the impact of dietary Se supplementation by an inorganic or organic source on the antioxidant defense system of rainbow trout (Oncorhynchus mykiss) juveniles fed practical plant-based feeds under normal or chronic stress conditions. Fish (initial mean weight: 42 ± 2 g) were maintained under normal (25 fish/tank, dissolved oxygen: 7.9 mg/l) or stressful conditions combining decreased water quality with hypoxia and increased stocking density (50 fish/tank, dissolved oxygen: 5.9 mg/l) for 12 weeks at 17 °C. Rainbow trout juveniles were fed three plant-derived protein-based diets containing 0.5 mg Se/kg diet supplemented or not with 0.3 mg Se/kg diet supplied as sodium selenite or Se-enriched yeast, Selsaf®. The apparent digestibility coefficients (ADC) of dry matter, protein, ash and Se were improved by Se-enriched yeast supplementation while the ADC of Se was reduced by sodium selenite supplementation and the ADC of dry matter, starch, energy, ash and phosphorus were reduced by chronic stress exposure. Dietary Se supplementation had no significant impact on growth performance contrary to chronic stress exposure which led to decreased final body weight and feed intake. Total Se content of fish was increased by both dietary Se supplementations but to a larger extent with Se-enriched yeast. Fish fed Se-enriched yeast displayed increased hepatic selenomethionine content and decreased muscle anisidine value. Blood glutathione content was reduced by chronic stress exposure. While hepatic catalase activity and transcript expression were increased by chronic stress exposure, both hepatic and renal glutathione peroxidase (GPX) activity and hepatic transcript expression of gpx1b2 and gpx4a2 were decreased in non-Se supplemented fish. These results suggest the necessity to supplement plant-based diets with Se for rainbow trout juveniles, independently of chronic stress exposure and highlight the superiority of organic form of Se to fulfil the dietary Se requirement and sustain the antioxidant status of fish.

Glutamate and glutamine transporter genes in grass carp (Ctenopharyngodon idellus): Molecular cloning, characterization and expression in response to different stocking densities

Active transporters play a central role in the uptake and efflux of glutamate by cells and organelles. We aimed to assess the effects of crowding stress on the efficiency of active glutamate and glutamine transport in fish. We cloned intestinal-related transporters and investigated their transcriptional changes in grass carp Ctenopharyngodon idellus exposed to different stocking densities. The full-length cDNA sequences of slc1a1, slc1a3 and slc7a6 cloned by rapid amplification of cDNA ends were 2,869, 2,508 and 2,141 base pairs respectively. Based on homology modelling, we derived three-dimensional models of SLC1A1, SLC1A3, SLC7A6 and SLC7A7 and noted their transmembrane domains. The expression profiles of slc1a1, slc1a3 and slc7a7 demonstrated tissue specificity, with section-dependent expression patterns along the intestine. Moreover, segmental mRNA expression patterns of slc1a3, slc7a6 and slc7a7 were affected by stocking density. Crowding stress notably altered the segment-specific mRNA expression of slc7a6. The results of this study showed that increased stocking density increased mRNA expression levels of glutamine transporters (slc7a6 and slc7a7) but decreased mRNA expression of the glutamate transporter (slc1a3). These results furthered our understanding of the relationship between crowding stress and intestinal glutamate/glutamine transport in fish.

Assessment of Stocking Rate and Housing System on Performance, Carcass Traits, Blood Indices, and Meat Quality of French Pekin Ducks

Commercial practice in poultry production management has been susceptible to increased problems, driven by concerns about safety of food and animal welfare. Thus, the main proposal of the present study was to evaluate the influence of different stocking densities on performance, blood, and carcass traits of Pekin ducklings reared on two different floor types (wood shaving litter, WSL or plastic slatted floor, PLS). A total of 450 one-day-old ducklings were randomly allocated into six equal experimental groups stocking density (nine, 15 and 21 birds/m2 during the first 14 d and three, five and seven birds/m2 until 49 days) reared on two floor types (WSL and PLS), five replicate pens each. Increased stocking density reduced body weight (BW), weight gain (WG), and feed conversion ratio (FCR) values and increased feed intake (FI) in both floor types at 14 days old. At 49 days old, reared ducklings on PLS type verified higher BW and WG and reduced FCR values. Moreover, increasing stocking density in both floor types significantly reduced the breast, thigh, and left fillet percentages. Conversely, reared birds floored on PLS system decreased the triglycerides (TG) and increased the total cholesterol (TC) serum content. Furthermore, the meat contents of TG and TC were decreased in birds reared on higher stocking density but not affected by floor type. Further, serum antioxidant indices were reduced in PLS birds on low stocking densities. In conclusion, housing Pekin ducklings on PLS improved their growth performance, carcass traits, meat cholesterol, and antioxidant status, particularly at stocking density of three and five birds/m2.

Effects of stocking density on the growth performance, physiological response and intestinal microbiota of juvenile Echiura worms ( Urechis unicinctus )

Aquaculture of the Echiura worm Urechis unicinctus has developed rapidly in recent years. However, the artificial cultivation technology remains to be perfected. In this study, the effects of stocking density on the growth performance, physiological responses and intestinal microbiota of U. unicinctus juveniles were evaluated. Juvenile worms were randomly stocked at densities of 200 U (U. unicinctus/m3), 500 U, 1,000 U and 2,000 U, in aquariums. The results indicated that the contents of triglycerides, glucose, total cholesterol, lactic acid, alkaline phosphatase, acid phosphatase and aspartate transaminase in the coelomic fluid of U. unicinctus juveniles were significantly enhanced with increasing stocking density. The digestive enzyme activities increased with increasing stocking density from 200 U to 1,000 U, before exhibiting a significant decrease in the 2,000 U group. In contrast, the antioxidant capacity of U. unicinctus juveniles was suppressed under high stocking density conditions. In case of the intestinal microbiota of U. unicinctus juveniles, Actinobacteria were more abundant in the 200 U group; SJA15, Gluconobacter and OP81 were higher in the 1,000 U group; Burkholderiales and Limnohabitans were enriched in the 2,000 U group. The highest and lowest survival rates of the U. unicinctus juveniles were recorded in the 500 U and 200 U groups respectively, and high stocking densities negatively affected the individual growth performance. In summary, due to the highest survival rate and appropriate growth performance and physiological responses, 500 U was considered to be the optimal stocking density for the cultivation of U. unicinctus juveniles.

Effects of alpha-lipoic acid on the behavior, serum indicators, and bone quality of broilers under stocking density stress

The objective of present study was to investigate the effects of alpha-lipoic acid (ALA) dietary supplementation on the behavior, physiological and oxidant stress indicators, and bone quality in broilers under high stocking density (HSD) stress. A total of one thousand eight hundred 22-day-old Arbor Acres male broiler chicks were randomly allocated to 18 pens (2.97 × 2.03 m) in 3 groups: 14 birds/m2 (NSD, normal stocking density) or 18 birds/m2 (HSD) or 18 birds/m2 plus 300 mg/kg ALA dietary supplement (HSD + ALA, high stocking density + alpha-lipoic acid). Each treatment had 6 replicates, and the experiment lasted 3 wk. The HSD group was significantly lower than the NSD group (P < 0.05) in the frequency of eating, walking, and preening behavior. The alkaline phosphatase activity and serum calcium content were significantly higher, and the parathyroid hormone (PTH) level was significantly lower in the HSD group than in the NSD group (P < 0.05). When compared with the NSD group, the HSD group showed an increase (P < 0.05) in serum heterophil/lymphocyte ratio (H/L ratio), corticosterone (CORT), malondialdehyde (MDA) content, and catalase (CAT) activity, whereas a decrease (P < 0.05) in total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) concentrations. The HSD group was also significantly lower (P < 0.05) than the NSD group in the tibia and femur breaking strength, bone mineral density, and BMC. Importantly, the addition of ALA into the diets of the HSD group enabled the HSD + ALA group to recover to the levels of NSD group (P > 0.05) in the standing and preening behavior, alkaline phosphatase activity, PTH concentration, H/L ratio, CAT, T-AOC, MDA, SOD, and GSH-Px. These results indicate that the increase of stocking density lowered the bone quality, increased the physiological and oxidative stress indicators, and modified the behavior of broilers, whereas ALA dietary supplementation could counteract the reduction in the performance and physiological responses of broilers under high-density environmental stress.

Molecular characterization of GRP94 and HSP90α from Trachinotus ovatus, Linnaeus 1758 and their expression responses to various levels of stocking density stress and Cryptocaryon irritans infection

Heat shock proteins (HSPs) are a class of molecular chaperones with a wide range of biological activities. To understand the stress responses of 94-kDa glucose-regulated protein (GRP94) and heat shock protein 90 alpha (HSP90α) under stocking density stress and C. irritans infection, we obtained their cDNA sequences from T. ovatus and performed bioinformatic analysis on their structures. Meanwhile, the tissue-specific expression patterns of these genes were also detected by qPCR. The ToGRP94 cDNA contains an open reading frame of 2394 bp, which encodes a protein of 797 amino acids, while ToHSP90α contains an open reading frame of 2190 bp, which encodes a protein of 730 amino acids. Amino acid sequence analysis showed that these proteins have highly conserved characteristic family domains or motifs, such as the heat shock hsp90 protein family signature (Y [k/s] NKEIFLRE). ToGRP94 was recently related to S. dumerili GRP94 with amino acid sequence homology up to 96.86%, and ToHSP90α had a higher evolutionary correlation with M. armatus and A. testudineus HSP90α with sequence homology of 98.49% and 97.67%, respectively. ToGRP94 and ToHSP90α mRNAs were widely expressed in all tissues tested under normal conditions. ToGRP94 mRNA was most strongly expressed in gill tissue followed by fin and kidney tissues, while ToHSP90α was most strongly expressed in blood tissues followed by brain, kidney and gill tissues. Under stocking density stress, ToGRP94 mRNA in the liver was significantly higher in the LD group, but it did not change in the kidney and spleen tissues with increasing stocking density; however, the expression level of ToHSP90α gene increased significantly in liver, spleen, and kidney tissues under high stocking densities, which indicates that ToHSP90α was closely related to density chronic stress. After C. irritans infection, the expression of ToGRP94 was significantly increased in liver, spleen, and kidney tissues. Similarly, ToHSP90α gene expression was significantly increased in liver and kidney tissues, but there was no difference in spleen tissue. The results indicate that these two genes may be involved in the immune response of T. ovatus. In summary, ToHSP90α would be involved in chronic stress and the immune response, while ToGRP94 would be mainly involved in the immune regulatory response. These results may provide a reference for further research studying the function of fish HSP90 and its mechanism under environmental stress.

Effects of rearing density and dietary tryptophan supplementation on intestinal immune and antioxidant responses in rainbow trout (Oncorhynchus mykiss)

The present study was conducted to assess the effects of dietary tryptophan (Trp) supplementation on intestinal health in rainbow trout (Oncorhynchus mykiss) reared at two stocking densities. For this, the fish were kept at 15 (low density) or 25 (high density) kg m−3 initial densities and fed diets supplemented with 0 (T0), 5 (T5) and 10 (T10) g Trp. kg−1 diet. After 70 days of rearing, the fish intestinal cytokine and antioxidant-related gene expressions as well as oxidative stress were evaluated. Dietary Trp and stocking density showed significant interaction effects on intestinal tumor necrosis factor-alpha (tnfa) (P < .001), interleukin-1beta (il1b) (P = .016), interleukin 8 (il8) (P = .007), interleukin 6 (il6) (P < .001), superoxide dismutase (sod) (P = .019), catalase (cat) (P = .041), and glutathione peroxidase (gpx) (P = .001) gene expression, as well as, superoxide dismutase (SOD) (P < .001), catalase (CAT) (P = .007), glutathione peroxidase (GPx) (P < .001) activities, and malondialdehyde (MDA) (P < .001) levels. Under low stocking density, dietary Trp supplementation induced no significant changes in the cytokines, cat and gpx gene expressions compared to the control group. Intestinal SOD and CAT activities increased, but MDA level decreased in the T5 treatment compared to the T0, under low stocking density. The T10 group showed significantly lower sod gene expression and higher CAT activity compared to the T0 groups at low density. Expression of tnfa, il6, il8, and cat genes increased, but gpx decreased in the T0 group, under the high stocking density. This group, also, showed decrease in SOD and GPx activity, and increase in MDA levels at high stocking density. The T5 treatment showed significant increase in all gene expressions, SOD and GPx activities, with no changes in MDA levels under 25 kg m−3 stocking density, compared to 15 kg m−3. Significant increase in tnfa and cat gene expression and MDA levels, but decrease in CAT activity wwere observed in the T10 treatment, under high stocking density. Overall, dietary Trp at 5 g kg−1 levels intensifies intestinal antioxidant and inflammatory responses to the increase in stocking density, but inhibits MDA elevation. But higher Trp supplementation (10 g kg−1) weakens/inhibits the intestinal gene expressions and antioxidant enzymes activity, with no benefits on oxidative stress.

A multi-objective optimization model for dairy feeding management

The allocation of feedstuff to intensively managed dairy cows to achieve different objectives is challenging due to the inherent complexity of the system and the combinatorial problem that has to be solved. Pareto-based multi-objective optimization approaches using evolutionary algorithms can help to address these challenges and show the trade-offs and synergies among various objectives. Here we present a framework for multi-objective optimization with the Differential Evolution (DE) algorithm applied to dairy feeding systems with grazing and concentrate supply to generate an approximation of the Pareto front. The available feed resources are located in different feeding areas, and the number of animals and groups of animals with similar feeding requirements are distributed across these areas for feeding purposes. To evaluate the DE algorithm, we performed two in-silico experiments to: (1) compare the solutions quality of single-objective DE with exact Linear Programming (LP) solutions, and (2) assess the influence of different stocking rates (number of cows/ha) on milk production, feed allocation and economic performance indicators. The DE solutions that minimize the feeding costs for different stocking rates (1.1–2.6 cows/ha) closely approached the solutions derived with LP, confirming the quality of the heuristic algorithm. The multi-objective model scenarios demonstrated that increasing stocking density would enhance milk production and gross margin per unit of area at largely unchanged productivity per animal by shifting the feed ration from roughage to a large proportion of supplementary concentrate feed. At low stocking rates solutions with high productivity and gross margin and a large proportion of roughage in the ration and limited supplementary feeding were identified. We conclude that the multi-objective optimization with a Pareto-based DE algorithm is highly effective to explore the interrelations among conflicting objectives and to find suitable solutions.

Vaname Shrimp Cultivation (Litopenaeus vannamei) on High Stocking Densities in Controlled Ponds

Efforts to increase the productivity of ponds can be done by increasing stocking densities accompanied by providing excellent input and adequate technological support. Three stocking densities are 750; 1,000; and 1,250 individu/ m2, applied to ponds with an area of 1,600 m2 with water depth of 2.0 m, equipped with aeration systems in the form of windmills and root blowers, submersible pumps, automatic feeders, central drain and collector drain as well as wastewater treatment plants. The capacity of the aeration system is 500 kg of shrimp/HP biomass. Shrimp kept for 110 days. The results showed that the stocking density applied resulted in a final shrimp weight which was relatively the same range 15.50-16.45 (15.60 ± 0.40) g/individual with a daily growth value of 0.165-0.185 (0.17 ± 0.01) g/day. The production obtained is 13,714 kg; 18,285 kg; and 21,942 kg. Value of feed conversion ratio 1.42, 1.39, 1.54 and electricity needs 3.21, 2.53, 2.42 kw/kg of shrimp and 2.25 water requirements, 1.65, 1.63 m3/kg shrimp. The lowest shrimp production cost is IDR. 30,526/kg of shrimp on a stocking density of 1,000 individu/ m2 with an operating profit of IDR 585,142,857.14/year. The stocking density of 1,000 individu/m2 produces better performance, so it is recommended to be a reference for high stocking densities for vaname shrimp farming.