Dietary organic acids ameliorate high stocking density stress-induced intestinal inflammation through the restoration of intestinal microbiota in broilers

Background:High stocking density(HSD)stress has detrimental effects on growth performance,intestinal barrier function,and intestinal microbiota in intensive animal production.Organic acids(OA)are widely used as feed addi-tives for their ability to improve growth performance and intestinal health in poultry.However,whether dietary OA can ameliorate HSD stress-induced impaired intestinal barrier in broilers remains elusive.In this study,a total of 528 one-day-old male Arbor Acres broilers were randomly allocated into 3 treatments with 12 replicates per treatment including 10 birds for normal stocking density and 17 birds for HSD.The dietary treatments were as follows:1)Normal stocking density+basal diet;2)HSD+basal diets;3)HSD+OA.Results:HSD stress can induce increased levels of serum corticosterone,lipopolysaccharides,interleukin-1β,tumor necrosis factor-α,and down-regulated mRNA expression of ZO-1,resulting in compromised growth performance of broilers(P<0.05).Dietary OA could significantly reduce levels of serum corticosterone,lipopolysaccharides,interleukin-1β,and tumor necrosis factor-α,which were accompanied by up-regulated interleukin-10,mRNA expres-sion of ZO-1,and growth performance(P<0.05).Moreover,OA could down-regulate the mRNA expression of TLR4 and MyD88 to inhibit the NF-κB signaling pathway(P<0.05).Additionally,HSD stress significantly decreased the abundance of Bacteroidetes and disturbed the balance of microbial ecosystems,whereas OA significantly increased the abundance of Bacteroidetes and restored the disordered gut microbiota by reducing competitive and exploita-tive interactions in microbial communities(P<0.05).Meanwhile,OA significantly increased the content of acetic and butyric acids,which showed significant correlations with intestinal inflammation indicators(P<0.05).Conclusions:Dietary OA ameliorated intestinal inflammation and growth performance of broilers through restor-ing the disordered gut microbial compositions and interactions induced by HSD and elevating short-chain fatty acid production to inhibit the TLR4/NF-κB signaling pathway.These findings demonstrated the critical role of intestinal microbiota in mediating the HSD-induced inflammatory responses,contributing to exploring nutritional strategies to alleviate HSD-induced stress in animals.

Effects of dietary tryptophan and stocking density on the performance,meat quality,and metabolic status of broilers

Background： Highly automated cage-rearing systems are becoming increasingly popular in China. However, a high stocking density can cause oxidative stress and decrease broiler performance. The tryptophan （TRP） derivative 5-hydroxytryptophan （5-HT） has been shown to preserve membrane fluidity in birds suffering from oxidative stress Therefore, this experiment was conducted to determine the effects of dietan/TRP supplementation on performance, breast meat quality and oxidative stress in broilers reared in cages with a high or low stocking density. Methods： Female Arbor Acres broilers （25-d-old, n = 144） were randomly allocated to 1 of 4 treatments. The birds were fed a diet based on corn, soybean meal, cottonseed meal and corn gluten meal containing either 0.18 or 0.27% TRP and were housed with stocking densities of 11 or 15.4 birds/m2 in a 2 x 2 factorial experiment. Broiler performance was evaluated from d 25 to 42. Eight birds from each treatment were slaughtered on d 42 and plasma and breast muscle samples were collected to measure biochemical indices. Results： A higher stocking density tended to be associated with reduced weight gain （P 〈 0.10）, and significantly increased plasma glutamic-pyruvic transaminase （GPT） activity （P 〈 0.001）. Increased dietary TRP significantly reduced the activities of lactic dehydrogenase and GPT while increasing total cholesterol in the plasma （P 〈 0.01）, reducing drip loss of breast muscle （P 〈 0.10） and improving feed efficiency （P 〈 0.10）. Conclusions： An increase in dietary TRP, ].S-fold higher than the standard supplementation level, can alleviate oxidative stress as well as improve welfare and feed efficiency in broilers reared in cages with a high stocking density.

Effect of Stocking Density on Water Quality and(Growth, Body Composition and Plasma Cortisol Content) Performance of Pen-Reared Rainbow Trout(Oncorhynchus mykiss)

The goal of the study was to examine the effect of stocking density on the water quality of culture area, as well as the growth, body composition and cortisol content of rainbow trout(Oncorhynchus mykiss). Pen-reared trout were stocked in densities of 40, 60, 80 fish individuals m^(-3)(4.6, 6.6, 8.6 kg m^(-3), SD1, SD2 and SD3 groups, respectively) for 300 days. Compared to the water from SD1 and SD2, that from SD3 exhibited significantly higher NH_4^+-N content and COD(chemical-oxygen-demand), and a significant reduction of dissolved oxygen in day 180(40.6 kg m^(-3)). Stocking density was significantly associated with body weight, standard length, VSI(viscerosomatic index), CF(condition factor) and FC(food coefficient) in group SD3, particularly in day 240 and day 300(45 or 49.3 kg m^(-3)). Increased crude fat and decreased crude protein were displayed in high density group when the density reached to 36 kg m^(-3). As a cumulative effect of density-related stress, VSI, CF, FC, moisture, and crude protein content varied over time in each density group(SD1, SD2, and SD3). In summary, trout exhibited a better growth performance in low density(26.3 kg m^(-3)) than those reared in high densities(36 and 45 kg m^(-3)). The results indicate that rainbow trout(114.44 g ± 6.21 g, 19.69 cm ± 0.31 cm) initially stocked in 6.6 or 8.6 kg m^(-3) should be lightened to less than 36 kg m^(-3) after an intensive rearing for 240 days.

Research Progress on Effects of Stocking Density on Performance, Health and Welfare of Duck

Stocking density is an important factor for animal production performance.It appears particularly urgent and important to research systematically on stocking density for the dual restriction of environmental protection and animal welfare.This review dealt with the influence of stocking density on ducks'productivity and health through production performance,animal behavior and animal welfare,and analyzed the possible mechanism of high stocking density reducing production performance,resulting in abnormal behavior and stress,causing welfare and health problems.We consider that it might be associated with heat stress,more spatial competition(to gather the food,drinking water,sports area,etc.),as well as the quality deterioration of litter and house air caused by high stocking density.Finally,we put forward some suggestions on the study of stocking density's effects on ducks,and proposed the future work that need to be studied and problems that need to be solved imminently.

Stocking density effects on growth and stress response of juvenile turbot(Scophthalmus maximus) reared in land-based recirculating aquaculture system

Stocking density is widely recognized as a critical factor in aquaculture and a potential source of long-term stress.The influence of stocking density on growth and stress response of juvenile turbot（Scophthalmus maximus, ~3–75g, initial to final weight） was examined in fish held under low（LD, ~0.21–5.31 kg/m^2, initial to final density）,medium（MD, ~0.42–10.81 kg/m^2） and high stocking density（HD, ~0.63–14.27 kg/m^2） for 120 days in a recirculating aquaculture system（RAS）. In this trial, the growth curve for weight of juvenile turbot in RAS, all fitted by the Schnute model. No significant difference was found in growth performance among the three densities until at the final sampling（Day 120）. The final weight and body weight increase（BWI） in the HD group were significantly lower than in other groups（P〈0.05, weight：（75.83±2.49） g,（75.39±2.08） g,（65.72±2.86） g and BWI：（2 436.12±28.10）%,（2 421.29±4.64）%,（2 097.88±20.99）% in LD, MD and HD groups, respectively）. Similarly, the specific growth rate（SGR）, feed conversion ratio（FCR） and coefficient of variation for weight（CV_w） were adversely affected by high stocking density（P〈0.05）. However, there was no difference in survival and Fulton＇s condition factor（K） of turbot among the different groups. Physiological analyses demonstrated a clear increase in the plasma cortisol level and an obvious decrease in growth hormone（GH） concentration in the HD group on Day120（P〈0.05）. There was no significant effect of stocking density on plasma glucose, Cl– and protein levels. All these findings would provide a reference for selecting the optimal stocking density of juvenile turbot in RAS.

Effects of Temperature,Salinity and Stocking Density on Larval Survival and Growth of Reciprocal Crosses Between Two Strains of Pacific Oysters,Crassostrea gigas

The Pacific oyster Crassostrea gigas is one of the most widely cultivated aquaculture species and contributes signifi-cantly to total seafood production for human beings.However,mass mortality occurred frequently,and in some regions almost all oysters died during seed production and grow-out stage.In order to explore whether hybridization breeding can improve its growth and survival,a complete diallel cross between a selected strain‘Haida No.1’(S)and an orange shell variant(O)of C.gigas was carried out.The larval growth and survival were compared among hybrids and purebred strains at temperatures of 16,20,24,28 and 32℃;salinities of 15,20,25,30 and 35;and stocking densities of 0.5,1,2,4 and 8 larvae mL−1.Under different environments,the hybridization between two strains of C.gigas showed the heterosis of growth and survival.The mean shell height and survival rate of the two reciprocal crosses(OS,SO)were significantly higher than those of the two purebred strains(SS,OO)under all environ-mental conditions.In particular,OS showed greater heterosis than the purebred strains and SO progeny.The results showed that the productive traits of the‘Haida No.1’could be improved by crossing with the orange shell line.Meanwhile,the results from this study also indicated that hybridization between the two strains of C.gigas may be a promising way for breeding new variety with high survival rate.

Effect of Alum-Amended Litter and Stocking Density on Ammonia Release and Footpad and Hock Dermatitis of Broilers

Two experiments were conducted to evaluate the effect of alum on ammonia emission,live performance,and health of broilers.In experiment 1,the effect of alum （0,2,and 4%） supplementation on the emission of ammonia was measured.The effects of alum-treated litter and stocking density （12,16,and 20 birds m-2） on the live performance and incidence of footpad and hock dermatitis were investigated in experiment 2.Alum supplementation in chicken excreta significantly decreased pH from 8.06 to 5.27 and 3.62 by 2 and 4% alum treatments,respectively.Ammonia emission rate was reduced 73.0 and 75.8% by 2 and 4% alum treatments,respectively.The suppressed litter urease activity was detected in 4% alum treatment.Alum-amended litter （1 kg m-2） decreased atmosphere ammonia concentrations by 30% in broiler house.Alum-amended litter maintained a lower pH until 35 d of age.Body weight （BW） gain was decreased by alum treatment in the period of 4-7 wk of age.Higher stocking density （20 birds m-2） increased BW gain in the first 3 wk of age but decreased BW gain during the period of 4-7 wk of age.Neither alum nor stocking density treatments had a significant effect on feed intake and feed efficiency.Alum-treated litter had no detrimental effect on the development of footpad and hock burns.In contrast,high stocking density （20 bird m-2） increased the incidence of footpad and hock lesion.The result suggests that the decreased litter pH and suppressed bacterial urease activity by alum treatment is responsible for the decreased ammonia emission.At high stocking density,the increased litter moisture content should be responsible,at least partially,for the development of footpad and hock lesions.

Effects of osmotic pressure, temperature and stocking density on survival and sexual reproduction of Craspedacusta sowerbii

The effects of osmotic pressure, temperature and stocking density on medusae survival of Craspedacusta sowerbii were examined. The medusae were shown to be sensitive to the variations of osmotic pressure. And the survival time was 〈90 h at 34 mOsm/L and it declined rapidly with rising osmotic pressure. The peak survival time of 〉200 h was recorded at 0.2 mOsm/L. Comparing with 27℃ and 32 ℃ treatments, 23 ℃ treatment yielded lower activities at a range of 8-13/min. However, there was a longer survival time. A non-linear relationship existed between survival time and stocking density. Lower density resulted in larger body size. And sexual reproduction resumed after breeding for 〉22 days. Newly-formed polyps and medusae appeared subsequently but only in the higher-density groups of 10, 14 and 18 ind./L. It suggested that the number of newly-formed polyps and medusae was highly dependent on stocking density. That is, a higher stocking density produced more organisms. However, newly-formed medusae died within one month and none grew a diameter of 〉5 mm.

Evaluating a Three-Fold Continuum of Fry Stocking Density for Rearing Walleye in Lined Ponds

Fry stocking density can affect harvest metrics for fingerling walleye (Stizostedion vitreum) reared in drainable ponds, but few studies have examined these relationships with the use of elevated walleye fry stocking densities in lined ponds. Correlation and regression analyses were used to assess how a three-fold change in walleye fry stocking density (234,375 to 703,125 per hectare) relates to harvest metrics and length of the culture period, as well as the tradeoff experienced between walleye size (grams) and harvest density in 0.32-hectare lined ponds over a nine-year period at Blue Dog State Fish Hatchery, South Dakota. As fry stocking density increased, so did harvest metrics for both number (r = 0.85, P < 0.01) and yield (r = 0.81, P < 0.01). Length of the culture period varied between 24 and 35 days and was negatively related to stocking density (r = -0.66, P The linear relationship between harvest density and yield was highly correlated (r = 0.95, P < 0.01) with highest values measuring 617,625 walleye and 173 kilograms per hectare. Harvest density explained 61% of the variation in walleye size (P 0.01) and exhibited a decreasing curvilinear relationship such that continued increases in harvest density resulted in smaller reductions in fish size. Increasing fry stocking density from 234,375 to 703,125 per hectare in lined ponds coincided with increased rearing efficiencies for number and yield, as well as a reduced culture period. Minimal reduction in walleye size occurred once harvest density exceeded 300,000 per hectare.

Effects of stocking density on growth performance, blood parameters and immunity of growing pigs

This study was conducted to evaluate the effects of different stocking densities on growth performance,blood parameters,intestinal morphology and intestinal immunity of growing pigs.A total of288 male pigs(44.35±0.50 kg)were randomly assigned to groups with stocking densities of 2.46,1.23 and 0.82 m2/pig for a month.The results showed that there was no significant difference on growth performance among groups.Pigs in the stocking density of 0.82 m2/pig had the lowest backfat thickness and spleen weight index among groups(P<0.05).With increasing stocking density,the serum concentrations of blood urea nitrogen(BUN),transglutaminase(TGG),alkaline phosphatase(AKP)and immunoglobulin A(Ig A)were increased,and albumin(ALB),albumin-to-globulin ratio(ALB:GLO),insulin-like growth factor-1(IGF-1)and immunoglobulin(Ig M)were decreased(P<0.05),and cortisol tended to increase and glucose tended to decrease(0.05<P<0.1).Compared with the stocking density of 2.46 m2/pig,the ileal villus height and jejunal villus width decreased in stocking densities of 1.23 and 0.82 m2/pig(P<0.05).The duodenal villus height and ileal villus width in the stocking density of 0.82 m2/pig were the lowest among 3 groups(P<0.05).The content of immunoglobulin A in duodenum,jejunum and ileum mucosa increased along with increasing density(P<0.05).The contents of interleukin(IL)-2 in the spleen or liver and IL-10 in the spleen were higher in the stocking density of 0.82 m2/pig than in other 2 groups.These results showed that stocking density could affect the metabolism,intestinal morphology,and immunity of growing pigs and 1.23 m2/pig may be the suitable stocking density for the growing pigs in the present study.

Role of dietary gamma-aminobutyric acid in broiler chickens raised under high stocking density

The present study was conducted to evaluate the effects of dietary gamma-aminobutyric acid(GABA)in broiler chickens raised in high stocking density(HSD)on performance and physiological responses.A total of 900 male broiler chicks(Ross 308)at 1 d old were assigned in a 2×2 factorial arrangement to 4 treatments(10 replicates per treatment)with stocking density,7.5 birds/m^2(low stocking density;LSD)or 15 birds/m^2(HSD),and dietary GABA,0 or 100 mg/kg.Chickens raised in HSD exhibited a decrease in body weight gain in all phases(P<0.05)and feed intake in starter and whole phases(P<0.01),and an increase in feed conversion ratio in the finisher phase(P<0.01)compared with LSD-raised chickens.However,dietary GABA did not affect growth performance nor interacted with stocking density on production variables.The HSD vs.LSD increased relative liver weight on d 35 whereas dietary GABA increased relative liver weight and decreased relative bursa weight on d 21.Both stocking density and dietary GABA affected yield and quality of breast and leg muscles.Dietary GABA increased(P<0.05)width of tibia on d 35 and interacted(P=0.054)with stocking density on breaking stocking density on d 35.The HSD vs.LSD group lowered(P<0.05)feather coverage scores.Significant interaction between stocking density and GABA on surface temperature of shank on d 21 was noted(P=0.024).Dietary GABA exhibited an opposite effect on the concentrations of cecal short-chain fatty acids depending on stocking density leading to a moderate to significant interaction.Stocking density decreased alpha-1-acid glycoprotein whereas dietary GABA decreased heterophil-to-lymphocyte ratio and corticosterone in blood or serum samples.Serum biochemical parameters were altered by stocking density or dietary GABA.It is concluded that dietary GABA alleviated stress indices including corticosterone and heterophilto-lymphocyte ratio,but failed to reverse stocking density-induced growth depression.

Effect of stocking density on growth performance of monosex Nile Tilapia (Oreochromis niloticus) in the aquaponic system integrated with lettuce (Lactuca sativa)

Aquaponics is a fish-plant recirculating system where nutrients received from the fish culture are absorbed by the plants for growth.The technology is relatively new for fish culture in Kenya,and the principles and operations remain largely untested for many fish species.This study determined how stocking density affects the growth performance and water quality in a Nile tilapia-lettuce(Lactuca sativa)aquaponics system.The experimental design included five replicates for each of the aquaponic systems stocked at densities of 150,300,and 450 fish/m^(3) for a rearing period of 56 days.Each treatment had a planting density of 16 lettuce/m2.The water quality parameters ranges during the rearing period were 3.83-5.35 mg/L for dissolved oxygen,7.44 to 7.6 for pH,0.014 mg/L to 0.032 mg/L for total ammonium nitrate(TAN),1.11-1.34 mg/L for nitrate,and 0.01-0.08 mg/L for nitrite,and all decreased with increasing stocking density.The final weight of fingerlings was 25.2±4.2 g,32.0±3.8 g and 42.6±3.1 g for 450,300,and 150 fish/m^(3) respectively.Specific growth rate(SGR)was reduced with increasing stocking density whereas food conversion ratio(FCR)increased with stocking density.Aquaponic systems with the lowest stocking densities performed better than 300 and 450 fish/m^(3) respectively.

Determine the Optimal Density of Nile Tilapia (<i>Oreochromis niloticus</i>) Fingerlings Cultured in Floating Cages

The objective of the study was to determine the optimal density of fingerlings of the Nile tilapia (Oreochromis niloticus) culture in floating cages with respect to growth performance and to know the effect of temperature on growth during the winter period. Tilapia fingerlings (mean weight 8.5 ± 0.36 g) were stocked at densities of 120, 180 and 360 fish/m3 for 10 weeks. During culture, fish were fed a diet contains 35% protein made of peanut seed, cottonseed, wheat bran, and Sorghum. The results showed that the increase in fish density reduced the final weight of the fish. The percentage of the fish weight increased and reached 111% ± 1.45% in the lowest fish density (120 fish/m3), 79% ± 1.87% in the medium density (240 fish/m3), and 63% ± 2.03% of high fish density (360 fish/m3), therefore the daily growth rate was better in the lowest density. The rate of food conversion ratio was also better in the lowest density with 2.17 ± 0.33, followed by the medium density with 2.79 ± 0.28 and then the highest density with 3.09 ± 0.21. However, the total production in the cage increased with increasing fish density, and the return to the cost of food was better with higher fish density. According to various performance evaluation criteria, it can be concluded that the medium density 240 fish/m3 is the best for growing Nile tilapia fingerlings in floating cages. It was observed that the growth rates of the three treatments were low due to the decrease in water temperature in most of the study period, which may indicate the useless of culture in cages in the winter season.

Seasonal Variations in Fishery Resources in Shenzhen Sea Area

Seasonal variations and causes for these were elaborated for fishery resources in Shenzhen sea area,to provide scientific basis for sustainable utilization and management of fishery resources in typical fisheries of South China Sea coasts. Based on the data of fishery resources collected through trawl surveys in Egong Bay fisheries area,Shenzhen,from August( autumn) and December( winter) of 2012 to March(spring) and May(summer) of 2013,seasonal variation of nekton species composition,stock density,dominant species composition,size spectra and biodiversity were studied. Results showed that there were 113 species of nekton in Shenzhen sea area,which belonged to 78 genus,50 families,14 orders and 3 classes. The number of species was the largest in summer(61 species) and smallest in autumn(53 species). In spring and winter,there was 56 species. The stock density and individual density of nekton were the minimum in summer(5950. 20 kg/km2 and 356. 45 ind/km2,respectively),whereas the percentage of fish stock density and individual density were the highest in summer(51. 99%and 42. 19%). The seasonal variations of size spectra indicated that fishing intensity was the highest in autumn,and was the lowest in summer. Additionally,biodiversity index presented significant seasonal variations,including Shannon-Wiener diversity index( H '),Margalef richness index( D') and Pielou evenness index( J'),with the same trend as summer > spring > autumn > winter. In conclusion,there are clear seasonal variations in the nekton species,biomass and structure in Egong Bay fisheries area in Shenzhen. Due to the difference in fishing intensity in different seasons( low intensity in summer and high intensity in autumn),community structure and function in summer are more stable than that in autumn and winter. Particularly,with the increase in the fishing intensity in autumn,k selection species will be replaced by r selection species.

Biological manipulation of eutrophication in West Yangchen Lake

This paper aims to share findings on nonclassical biomanipulation from a field study on eutrophic West Yangcheng(WY)Lake.In the forty years before 2009,cyanobacteria frequently bloomed in WY Lake,an event which has not occurred since 2009.The stocking density of filter-feeding carp was estimated to be more than 50 g/m^(3) in July after 2009,approximately double the amount observed before 2009,and the ratio of silver carp to bighead carp(SBR)increased from 0.8 to more than 1.6.Compared with the water quality between 2004 and 2007,the total nitrogen(TN)and the chlorophyll-a(Chl-a)concentration decreased while total phosphorus(TP)and transparency(SD)increased significantly after 2009(P<0.05).The decreasing Chl-a concentration was observed in Jul,Jun,May,Jul,and Mar in 2009,2010,2011,2016,and 2017,respectively.The Chl-a concentration was significantly negatively correlated with TP(P<0.05),and no significant correlation with TN was observed(P>0.05).A significant negative correlation was observed between fish yield and SD(P<0.05).The results also showed that filter-feeding carp more effectively restrained algae growth when SD was low.These results indicated that a high density of filter-feeding fish with increased SBR interfered with the driving effects of nutrients and temperature on the growth of algal biomass and then restrained bloom of algae.It may be necessary to take SD into consideration for determining the appropriate fish stocking density for the biomanipulation of algae.