Increasing Stocking Density Research Articles

Effects of stocking density on performance, egg quality, reproductive hormones, and antioxidant capacity in egg-laying ducks

ABSTRACT This study was conducted to evaluate the effects of stocking density on productive performance, egg quality, and antioxidant capacity in laying ducks. A total of 720 20-week-old Jinding laying ducks were randomly assigned to 5 stocking densities (4, 5, 6, 7, and 8 birds/m2) with 8 replicate pens each treatment. The results showed that increasing stocking density linearly increased egg production and egg mass and linearly decreased FCR of laying ducks (P < 0.05). The eggshell strength and thickness decreased linearly (P < 0.05) and quadratically (P < 0.05) with an increase in stocking density. Increased stocking density linearly decreased concentrations of estradiol-17β and follicle-stimulating hormone, activities of superoxide dismutase, glutathione peroxidase, and total antioxidant capacity in plasma (P < 0.05), but linearly increased plasma and hepatic malondialdehyde content (P < 0.05). The results suggested that high stocking density adversely influenced laying performance and egg quality of ducks, which is associated with impaired antioxidant capacity. Under our experimental conditions, we recommend that the stocking density of laying ducks should be kept to 4 or fewer birds/m2 to avoid the negative effects of high stocking density on performance and egg quality of laying ducks.

Influence of stocking density on water quality and growth performance of white leg shrimp (Litopenaeus vannamei) reared in fiberglass tanks, without water exchange

The present study evaluated the effects of stocking density on water quality parameters, growth performance and survival rate of white leg shrimp Litopenaeus vannamei, reared in fiberglass tanks, without water exchange. Three stocking densities (50, 100 and 200 shrimp/m2) were tested. Each treatment consisted of three replicates fiberglass tanks (500 L). The shrimp were fed ad libitum four times per day with a commercial pellet (40-42% protein). After an 8-week trial, concentrations of nutrients in the culture tanks showed an increasing linear relationship with increasing stocking density. The growth performance of shrimp in low stocking densities was significantly greater than that in high stocking densities. The results from this study demonstrate that with increasing the stocking density the production of shrimp increased but in a low final weight and survival compared to low stocking density.

Growth, yield and economic returns of striped catfish (Pangasianodon hypophthalmus) at different stocking densities under floodplain cage culture system

The influence of stocking density plays one of the major roles in the final production for profitable aquaculture. This study was conducted to investigate the effect of stocking density on growth, yield and economic return of striped catfish (Pangasianodon hypophthalmus). The fish were reared in cages at three different stocking densities. Fishes were stocked at 19, 22 and 25 fish/m3 densities indicated as T1, T2 and T3. After 90 days of the experimental period, growth and yield parameters were studied and economic analysis regarding farm profitability was carried out. Fish growth performance significantly decreased with increasing stocking density. The mean yields were 12.27 ± 0.08, 14.00 ± 0.14 and 15.01 ± 0.20 kg/m3 in T1, T2 and T3, respectively and showed significant variations (P < 0.05) with increasing stocking density. RGR, SGR, PER between 19 and 22 fish/m3 were not significantly different, but they were significantly higher than 25 fish/m3. The FCR was significantly lower in 19 and 22 fish/m3 than the 25 fish/m3 stocked cages. Environmental parameters were within the acceptable range. The benefit-cost analysis revealed significantly higher BCR in 19 and 22 fish/m3. Overall, best farm profitability was achieved from the stocking density of 22 fish/m3 among three stocking densities experimented in the study.

Effects of stocking density on the growth performance, serum biochemistry, muscle composition and HSP70 gene expression of juvenile golden pompano Trachinotus ovatus (Linnaeus, 1758)

Golden pompano (Trachinotus ovatus) is one of the most important cultured marine fish in Southeast Asia. Stocking density affects the growth performance and welfare of fish in aquaculture. A 70-day rearing experiment was performed to evaluate the effect of different stocking densities on the growth performance, feed conversion ratio, serum biochemistry, muscle quality, antioxidant capacity and HSP70 mRNA expression of juvenile golden pompano cultured in off-shore sea cages. The experimental design was completely randomized using three replications with three treatments: low (100 fish/m3), medium (200 fish/m3), and high (300 fish/m3) stocking densities. Fish growth decreased significantly, and the feed conversion ratio increased significantly with increasing stocking density (P < .05). The serum glucose concentration increased significantly (P < .05), and the total protein, total triglyceride and total cholesterol concentrations were significantly reduced with increasing stocking density (P < .05). High stocking density led to elevated serum cortisol levels and decreased thyroxine levels. There was a significant decrease in the muscular crude fat content with increasing stocking density (P < .05), while the moisture, ash and protein contents did not significantly differ among the groups (P > .05). In this experiment, superoxide dismutase, glutamine transaminase and total antioxidant capacity increased significantly with increasing stocking density (P < .05). The expression levels of heat shock protein 70 were significantly up-regulated in the liver, kidney and brain as stocking density increased (P < .05); however, there was no significant difference in the spleen (P > .05). Overall, high stocking density was a chronic stressor in this experiment and had a negative effect on the growth, feed conversion ratio and animal welfare of T. ovatus.

Effects of dietary ginger (Zingiber officinale) administration on growth performance and stress, immunological, and antioxidant responses of common carp (Cyprinus carpio) reared under high stocking density

In the present study, the effects of ginger (Zingiber officinale) on stress, antioxidant, humoral immune and cytokine responses of common carp (Cyprinus carpio) under high stocking density were investigated. The fish were assigned into four experimental groups: LD (the fish reared at 10 g L−1 and fed with the control diet), HD (the fish reared at 20 g L−1 and fed with the control diet), HD-5 (the fish reared at 20 g L−1 and fed with the control diet supplemented with 5 g kg−1 ginger), and HD-10 (the fish reared at 20 g L−1 and fed with the control diet supplemented with 10 g kg−1 ginger). After 60 days of rearing, the fish at the HD treatment exhibited significantly lower growth performance compared to the LD treatment, but the fish fed the diet supplemented with 10 g kg−1 (HD-10) showed growth performance comparable to the LD treatment. Under high stocking density, the fish had significantly higher cortisol and glucose levels, but ginger mitigated the stress responses. Plasma superoxide dismutase and glutathione peroxidase exhibited higher activities in HD, HD-5, and HD-10 treatments compared to the LD treatment. However, plasma catalase activity increased only in HD treatment. The increase in stocking density significantly increased plasma malondialdehyde levels, and ginger treatments significantly mitigated such increases. The fish at the HD treatment had significantly lower plasma lysozyme, complement and bactericidal (against Aeromonas hydrophila) activities and total immunoglobulin levels compared to those at the LD treatment; however, the dietary ginger administration inhibited these effects especially with fish fed 10 g ginger per kg diet. The fish at the HD treatment had significantly lower expression of tumor necrosis alpha (tnfa), interleukin 1 beta (il1b), and interleukin 8 (il8), and higher interleukin 10 (il10) genes. Ginger treatment, particularly at 10 g kg−1 level significantly mitigated the effects of high stocking density on the cytokines. In conclusion, the present study demonstrated that ginger treatment at 10 g kg−1 level is beneficial to suppress stress, oxidative stress, and immunosuppression caused by high stocking density in common carp.

Factors influencing GH and IGF‐I gene expression on growth in teleost fish: how can aquaculture industry benefit?

AbstractGrowth is a polygenic and environmentally controlled trait with the most influential genes being those of growth hormone (GH) and insulin‐like growth factor‐I (IGF‐I), as they consist the core of the hypothalamic–pituitary–somatotropic (HPS) axis. As a result, the influence of environmental and dietary conditions on GH and IGF‐I gene expression has a great potential in planning to optimize fish health and production, as growth rate of fish is a key factor in aquaculture. In this review, we provide a molecular and physiological overview of GH and IGF‐I gene expression as well as all the participating factors regulating GH/IGF‐I axis in growth. We further discuss the genetic, dietary and environmental factors affecting growth rate. More importantly, how external factors in combination with diet such as temperature, photoperiod, salinity, pollutants and stocking density affect GH and IGF‐I expression and growth rate. In addition, there is evidence that photoperiod effect varies among species by altering the seasonal cycle of GH and IGF‐I gene expression and biological cycle of fish. Pollution has also a variable effect on GH, IGF‐I and fish growth rate, depending on the pollutant, species and sex. Finally, increased stocking density influences the HPS axis and growth, dependent on species, temperature and the stage of growth. Notably, interactions among these factors were observed by the reported importance, primarily feeding‐related stress one of the most important factors, while environmental would add or subtract on each other’s optimal or suboptimal conditions in a hierarchy of significance, as further discussed.

Effects of stocking density on growth performance, growth regulatory factors, and endocrine hormones in broilers under appropriate environments

Stocking density is an important environment factor that affects the development of poultry farming, which has caused widespread concern. This study was carried out to determine the effects of stocking density on growth performance, growth regulatory factors, and endocrine hormones in broilers under appropriate environments. A total of 144 Arbor Acres male broilers (BW 1000 ± 70 g) were randomly divided into low stocking density (LSD; 6.25 birds/m2), medium stocking density (MSD; 12.50 birds/m2), and high stocking density (HSD; 18.75 birds/m2) groups, with 6 replicates in each group, and raised in 3 environmental chambers (same size) from 29-day-old to 42-day-old, respectively. The trial period lasted for 14 D with 21 ± 1°C and 60 ± 7% relative humidity, wind speed < 0.5 m/s, ammonia level<5 ppm. The results indicated that average daily food intake and average daily gain in HSD group showed significantly lower than other 2 groups (P < 0.05). Besides, the HSD group significantly reduced breast muscle yield, tibial length, tibial width, and tibial weight of broilers (P < 0.05). The HSD group increased the mRNA expression level of myostatin, and reduced the mRNA expression levels of insulin-like growth factor 1 (IGF-1) and myogenic determination factor 1 (P < 0.05). The HSD group significantly reduced the expression of parathyroid hormone-related protein in tibial growth plate (P < 0.05). The HSD group increased the serum corticosterone levels of broilers (P < 0.05), and decreased the serum IGF-1 and thyroxine (T4) levels of broiler chickens (P < 0.05) than other stocking density groups. Moreover, the serum alkaline phosphatase levels were decreased (P < 0.05) with increasing stocking density, whereas there were no significant effects on the serum 3,5,3′-triiodothyronine (T3) concentrations in 3 groups (P > 0.05). In conclusion, under appropriate environments HSD reduced the growth performance of broilers and this negative effect was likely associated with decreased growth of muscle and bone.

Fin damage and growth parameters relative to stocking density and feeding method in intensively cultured European perch (Perca fluviatilis L.).

We evaluated the relationship of stocking density to survival, growth performance and fin condition of European perch Perca fluviatilis with hand feeding and self-feeders. Hand-fed perch (body weight 19.1±5.1g and total length 107±9mm) were reared at 0.5, 1.0, 1.5 and 2.0 fish/L. Self-feeding perch (body weight 25.4±3.9g and total length 128±7mm) were reared at stocking densities of 0.6, 1.0 and 1.4 fish/L. Pond-reared perch served as a comparison group for fin damage assessment. We found no differences in survival rate among stocking densities with either feeding method. Hand-fed fish displayed the highest weight gain and SGR at stocking density of 0.5 fish/L. The self-feeding fish showed a non-linear association of weight gain with stocking density with the highest growth at 1.0 fish/L. Fin length was noticeably greater in pond-reared fish compared with RAS-reared fish regardless of feeding method. In both experiments, fin length relative to standard length showed a negative relationship with stocking density, with pectoral fins showing the greatest effect. Fin condition deteriorated with increasing stocking density, and growth was highest at 0.5 and 1.0 fish/L in hand-fed and self-feeding fish, respectively.

Effects of dietary protein levels with various stocking density on growth performance, whole body composition, plasma parameters, nitrogen emission and gene expression related to TOR signaling of juvenile blunt snout bream (Megalobrama ambylcephala)

A 70-day experimental trial was conducted to examine the interaction effects of dietary protein levels supplemented with essential amino acid (EAA) and stocking density on growth performance and physiological responses of blunt snout bream juvenile (Megalobrama ambylcephala). 3 × 3 factorial design is used to formulate three isoenergetic (18 KJ/g−1) diets having three levels of dietary protein (30%, 33%, and 36%) and stocking density (20, 40 and 60 fish/m3). Triplicate groups of blunt snout bream juvenile (initial weight 4.01 ± 0.01 g) were distributed into the floating cage (1 m3) and feed on the experimental diets according to the design three times daily till apparent satiation. Results showed that growth performances of the fish were not affected by the level of dietary protein and their interaction but decreased significantly with increasing stocking density. The moisture content of whole fish body was significantly increased, while lipid content was decreased with increasing level of dietary protein. However, moisture content was decreased significantly while lipid and protein contents were increased with increasing stocking density. Total ammonium nitrogen emission was increased significantly with increasing level of dietary protein and stocking density. Plasma glucose was affected positively by the level of dietary protein whereas total cholesterol (TC) was affected negatively. In the meantime, plasma protein, triglyceride, and cholesterol were affected positively by stocking density. Expression levels of the target of rapamycin, insulin-like growth factor-1, eukaryotic initiation factor 4E binding protein 2, and ribosomal protein S6 kinase 1 gene were not affected by the level of dietary protein but affected significantly by stocking density. Generally, using minimum levels of dietary protein supplemented with EAA and optimum stocking density has economic and environmental benefits in blunt snout bream production.

Effects of stocking density of Chinese soft‐shelled turtle and interactions between cultivated species on growth performance and the environment in a turtle–rice coculture system

AbstractExperiments were performed to investigate the effects of stocking density (6, 8, 10, and 12 turtles/m2) of Chinese soft‐shelled turtles (Pelodiscus sinensis) and coculture interactions on growth performance and environment in a turtle–rice coculture system. The average yields of rice grain and rice straw in four turtle–rice coculture (TR) groups were significantly higher than those in a rice monoculture with fertilizer (RMF) group and a rice monoculture (RM) group (p &lt; .05). The yield of turtles increased gradually with increasing stocking density until reaching 10 turtles/m2, and the yield of TR10 was 1,297.51 ± 106.31 g/m2. The death rate in TR6, TR8, and TR10 groups was significantly lower than that in the turtle monoculture (TM) group (p &lt; .05), whereas the specific growth rate and weight gain in TR6, TR8, and TR10 groups were significantly higher than those in the TM group (p &lt; .05). The nitrogen and phosphorus use efficiencies in the TR groups were significantly higher than those in the TM and RM groups (p &lt; .05). The water environment was improved in the TR group. The results suggest that an appropriate stocking density (10 turtles/m2) of turtles in the coculture system can effectively increase the yield of turtles and reduce the impacts on the environment compared with the TM.

Konsumsi Oksigen Ikan Uceng Nemacheilus fasciatus (Valenciennes, 1846) pada Kondisi Padat Tebar yang Berbeda

&lt;strong&gt;Oxygen Consumption of Barred Loach Nemacheilus fasciatus (Valenciennes, 1846) under Different Stocking Densities&lt;/strong&gt;. In aquaculture system, fish growth is affected by stocking densities. One way to predict the effect of stocking density on growth is to determine fish metabolic rate through oxygen consumption measurements. In Barred loach Nemacheilus fasciatus (Valenciennes, 1846), the information was scarce on oxygen consumption. This study was to analyze the effect of stocking density on oxygen consumption in Barred loach conducted at Research Institute for Freshwater Aquaculture and Fisheries Extension, Bogor in May 2018. Barred loach (total length: 5.79 ± 0.47 cm, weight: 1.32 ± 0.34 g) was observed its oxygen consumption on three different stocking densities (5, 10, and 15 fish/L) by using closed respirometers (volume: 1.4 L) with three replications of each treatment. Measurement of oxygen consumption was carried out under normoxia and hypoxia conditions. In addition, fish behavior and ventilation rate were also observed and recorded according to treatment. The results showed that the highest oxygen consumption of barred loach was found in the stocking density of 5 fish/L (1250.6 ± 128.4 mg O2/kg/h) which was significantly different from the stocking density of 10 fish/L (626.9 ± 46.7 mg O2/kg/h) and 15 fish/L (596.9 ± 48.9 mg O2/kg/h). Meanwhile, oxygen consumption of barred loach under hypoxic conditions decreased significantly compared to normoxic conditions, which was marked by a decrease in their swimming activities. Although the ventilation rate in hypoxic conditions has decreased, the value was not significantly different from those of normoxia condition. Results of this study provide information that an increase in stocking density and hypoxic conditions in barred loach caused a decrease in oxygen consumption rates. In addition, this study showed that the critical oxygen level for barred loach was around 3.1 mg/L

DESCENDí­Å NCIA DE NEOMACHOS DE &lt;i&gt;Rhamdia quelen&lt;i&gt;: AVALIAÇÃO DO CRESCIMENTO EM DIFERENTES DENSIDADES

Lotes monossexo feminino de Rhamdia quelen podem ser gerados por inversão sexual indireta e seu crescimento é influenciado pela densidade de estocagem, a qual é um fator importante no seu desenvolvimento. O estudo teve por objetivo comparar o desempenho produtivo das descendências de neomachos e de machos normais estocados nas densidades de 500, 1000 e 1500 peixes m-3 (D1, D2 e D3), durante 61 dias, através da avaliação de í­­ndices zootécnicos. A média inicial de peso e comprimento das descendências de neomachos e machos normais, foi respectivamente, 0,90 ± 0,12 g / 4,94 ± 0,22 cm e 0,80 ± 0,12 g / 4,60 ± 0,37 cm. Utilizou-se o delineamento experimental inteiramente ao acaso com três repetições, sendo os peixes estocados em tanques de 0,07 m³. Os valores finais de peso, comprimento e sobrevivência (média ± dp) foram os seguintes: Neomachos: D1 - 4,03 ± 0,50 g, 7,73 ± 0,20 cm, 98,10 ± 1,65%; D2 -: 4,08 ± 0,21 g, 7,80 ± 0,21 cm, 96,67 ± 0,82%; D3 - 4,74 ± 0,77 g, 8,18 ± 0,44 cm, 95,56 ± 3,34%; Machos: Dl - 3,67 ± 0,36 g, 7,58 ± 0,20 cm, 91,43 ± 2,86%; D2 - 3,96 ± 0,54 g, 7,86 ± 0,23 cm, 94,29 ± 3,78%; D3 - 4,23 ± 0,52 g, 8,05 ± 0,38 cm, 94,92 ± 3,85%. As diferentes descendências e densidades de estocagem testadas não apresentaram diferenças significativas para peso, ganho em peso, comprimento, sobrevivência, conversão alimentar e consumo de ração. Portanto, a descendência de neomachos apresentou desempenho produtivo adequado durante a fase de juvenis e suportou o aumento da densidade de estocagem sem prejuí­­zos ao seu desempenho, tornando os neomachos adequados para o cultivo de jundiá.

PENGARUH PERBEDAAN PADAT TEBAR LARVA TERHADAP PERTUMBUHAN DAN SINTASAN PADA IKAN UCENG (Nemacheilus fasciatus)

Proper stocking density on larval rearing of barred loach (Nemacheilus fasciatus Valenciennes, 1846) is very important in terms of obtaining the best growth and survival rate. This study was aimed to observe the growth and survival rate of barred loach subjected to different larval stocking density. Fish larvae were obtained by artificial spawning from in aquarium. Larvae were stocked on aquariums (50 × 40 × 30 cm) with three stocking density treatments (5, 10, and 15 individuals/L) and three replications. The experimental fish larvae were fed by Artemia and commercial feed (crude protein content: 30%) and feeding frequency twice per day (ad libitum). The length and weight were reassured every 10 days during 70 days of rearing period. Temperature, pH, and dissolved oxygen were measured at each treatment. Data obtained from measurements were analysed to assess the length gain, weight gain, specific growth rate (SGR), biomass gain, and survival rate. The results showed length gain of 3.35 ± 0.01, 2.94 ± 0.10, and 2.82 ± 0.15 cm and weight gain of 0.573 ± 0.023, 0.436 ± 0.018, and 0.417 ± 0.043 g in larval stocking density of 5, 10 and 15 individuals/L, respectively. Specific growth rates and biomass growth were of 6.22 ± 0.41, 5.93 ± 0.21, and 5.68 ± 0.41 %/day and 94.04 ± 5.39, 146.80 ± 3.81, and 167.24 ± 17.48 g in larval stocking density of 5, 10 and 15 individuals/L, respectively. Meanwhile, the survival rates obtained in this study were 89.13 ± 7.25, 93.13 ± 5.13, and 76.50 ± 3.54 % in larval stocking density of 5, 10 and 15 individuals/L, respectively. Increased stocking density has a negative impact on the growth and survival rate of barred loach.

PSV-3 Effects of space allowance and marketing strategy on growth performance of pigs raised to heavy market weights

Abstract A total of 976 pigs (PIC 327×L42, initially 22 ± 1.5 kg BW) were used in a 160-d study to determine the influence of space allowance and marketing strategy on performance of pigs raised to heavy market weights (165 kg). Pens were blocked by location and allotted to 1 of 6 treatments with 8 pens/treatment. The first four treatments reduced space allowance/pig via initial pen stocking density: 14 pigs/pen (1.20 m2/pig), 17 pigs/pen (0.98 m2/pig), 20 pigs/pen (0.84 m2/pig), or 23 pigs/pen (0.73 m2/pig). The fifth treatment began with 25 pigs/pen (0.67 m2/pig) and the heaviest 3 pigs/pen were removed on d 93, then on d 122 pens were marketed to a common inventory of 20 pigs/pen, and on d 147 marketed to a common pen inventory of 17 pigs/pen. The sixth treatment began with 23 pigs/pen (0.73 m2/pig) and were marketed to a common inventory of 20 pigs/pen on d 108 and marketed to a common inventory of 17 pigs/pen on d 147. Data were analyzed using PROC GLIMMIX with pen as the experimental unit. Overall (d 0 to 160) ADG, ADFI, and final BW decreased (linear, P &lt; 0.001) and G:F increased (quadratic, P = 0.042) as space allowance decreased. When comparing treatments with multiple marketing events (treatments 5 and 6) to treatment 4, there was no evidence for differences (P &gt; 0.05) for overall ADG or ADFI; however, overall G:F was improved (P &lt; 0.05) for pigs initially stocked at 0.67 m2/pig and marketed four times compared to both treatments that initially allowed 0.73 m2/pig, regardless of marketing structure. These results indicate that decreasing space allowance of heavy weight pigs reduces growth, feed intake and final BW, although use of multiple marketing events prior to final marketing may allow for increased number of pigs marketed/pen while balancing reduced growth performance often associated with increased stocking density. http://www.conferenceharvester.com/

All male nile tilapia Oreochromis niloticus fry nursing in net cages at haor of Sunamganj, Bangladesh

Nile tilapia (Oreochromisniloticus) of average 2.08 ± 0.06 to 2.14 ± 0.19 g fry nursed in nine-floating net-cages of 3 × 3 × 1.5 m in highstocking densitiesof 600, 800 and 1000 fry m–3 densities in triplicate. The fish were hand-fed a commercial tilapia floating feed at a rate of 5 to 30% of their body weight thrice daily. The final mean weight of tilapia ranged 15.13 ± 0.28 to 24.10 ± 0.35 g with the mean daily weight gain of 0.21 ± 0.11 to 0.38 ± 0.05 g/day. The low stocking density of 600 fry m–3 had significant higher mean weight, daily growth rate and specific growth rate than did the higher density treatment of 1000 fry m–3.The food conversion ratio were (1.46 to 2.30) significantly affected by stocking density (p&lt;0.05). Moreover, the net profit (BDT 1262 ± 85 - 2152 ± 55) showeda significant difference with increasing stocking density (p &lt; 0.05). The growth of nursing fry was found to be density dependent. However, survival rates were found high in all treatments and were not affected by density. But, higher gross yield was observed at the highest density. The results of this study has clearly demonstrated that the higher density (800and1000 fry m–3) could be more profitable for tilapia cages than the lower density (600fry m–3) in terms of cost effectiveness and to meet the demand for large scale fish production.&#x0D; Bangladesh J. Zool. 47(1): 149-158, 2019

Effect of dietary protein to energy ratio, stocking density and feeding level on performance of Nile tilapia in pond aquaculture

There is growing interest to understand the dietary P:E requirements for the supplemental feed used in tilapia pond culture where natural food contributes to production. In an on-farm trial, we tested the effect of lowering dietary P:E ratio on fish performance, pond nutrient utilization and economic benefit under two stocking densities and feeding levels. Forty ponds, (average size 234 ± 112 m2), were assigned to test the effect of two diets, which differed in P:E ratio (18 vs 14 g.MJ−1), two feeding levels (14 vs 18 g.kg-0.8.d−1) and two stocking densities (2 vs 3 fish.m−2). Initial fish biomass was 45(±21) vs 67(±38) g.m−2 at 2 vs 3 fish.m−2, respectively. The experiment lasted 82 days. Decreasing P:E ratio enhanced tilapia production (P < 0.05; 459 vs 399 g.m−2). Increasing stocking density of tilapia from 2 to 3 m−2 increased biomass gain 43% (P < 0.001; 354 vs 505 g.m−2). Averaged over both diets and stocking densities, growth and feed conversion ratio increased with increasing feeding level (P < 0.001). Fish survival was unaffected by diet, stocking density and feeding level. Dissolved oxygen increased with increased stocking density with low P:E diet. The opposite happened for high P:E diet (P < 0.05). Increasing the feeding level also increased the DO concentration (P < 0.001). N retention efficiency was higher with the low P:E ratio diet (P < 0.001; 71 vs 52%) and decreased with increasing feeding level (P < 0.001). The data on N gain and N balance at the pond level suggest that the food web productivity was stimulated by reducing the dietary P:E ratio. The low P:E diet increased the gross margin by 95% (P < 0.001; 2076 vs 1067 USD.ha−1) and benefit cost ratio by 22% (P < 0.05; 1.57 vs 1.29). The P:E ratio of the low P:E diet is less than the presently advised. Lowering the P:E ratio from 18 to 14 g.MJ−1 in pond feeds for tilapia will increase the economic viability of pond aquaculture.

Effects of stocking density on survival, food intake and growth of giant gourami (Osphronemus goramy) larvae reared in a recirculating aquaculture system

The influence of stocking density on survival, food intake, and larval growth was assessed in giant gourami (Osphronemus goramy) larvae reared in an indoor recirculating aquaculture system. Larvae aged eight days post-hatching were arbitrarily divided into six stocking density treatments (A: 0.6, B: 1.2, C: 2.4, D: 4.8, E: 9.6, F: 19.2 individuals L−1; four replicates per treatment) and reared for three weeks. Tubifex worms, used as food, were kept continuously available for larvae. Samples of larvae were collected at days 0, 7, 14 and 21. Performance indicators - including survival rate (%), food intake (% and g ind−1), total length (cm), body weight (g), specific growth rate (g day−1), biomass gain (g L−1), feed conversion ratio (FCR), condition factor (K) and coefficients of variation (%) - were measured. Water quality was checked throughout the experiment and parameters were maintained below critical thresholds for fish. The results showed no effect of stocking density on survival (> 98%) or size heterogeneity, although growth significantly decreased with increasing stocking density. At the end of the 21-day experiment, mean individual body weights were 563.2 ± 64.3, 461.0 ± 28.6, 288.8 ± 19.3, 170.2 ± 13.8, 113.6 ± 6.9 and 81.9 ± 2.3 mg, for groups A, B, C, D, E and F, respectively. Decreased growth may be due to reduction in food intake in larvae stocked at the highest densities. The consequences of intensification of giant gourami larval rearing should be further investigated in the nursery and grow-out phases.

The effect of stocking density on profitability of African catfish (Clarias gariepinus) culture in extensive pond systems

Stocking density is a major factor determining fish production and farm profitability because it directly affects fish survival, growth, behavior, health, water quality, and feeding. The effects of stocking density on water quality, production, body composition and farming profitability of Clarias gariepinus fed a practical marine fish viscera-diet in earthen ponds were studied. Fish (initial weight: 13.0 ± 0.2 g) were stocked in triplicate at densities of 5, 7 or 10 fish m−2 in earthen ponds (3 × 10 × 1 m, each) and hand-fed to apparent satiation twice daily with a diet (43% crude protein, 20 kJ g−1) formulated by mixing 30% of marine fish viscera meal with locally available ingredients, for a period of 90 days. Results indicated strong dependence of water quality parameters on stocking density, with water transparency, dissolved oxygen and zooplankton abundance significantly decreasing with increased stocking density. Similarly, production performance as measured by final weight, specific growth rate, daily weight gain and weight gain were affected by stocking density, and peaked at a stocked density of 7 fish m−2 (p˂0.05). Conversely, total fish yield and annual production increased significantly with increasing stocking density and reached a maximum yield (186.6 ± 3.2 kg are−1) and annual production (756.6 ± 10.7 kg−1are−1 year−1) at the highest density. Profitability analysis indicated that the profitability index (net return per total production cost) was high for all treatments and varied between 2.13 and 2.46, with significant differences between treatments. The highest profitability index was obtained at a density of 7 fish m−2; however, the highest net return was realised at the highest stocking density, but came at the expense of decreased production efficiency and an increased environmental cost, thereby demonstrating the potential trade-offs between maximising shorter term on-farm profits vs. ensuring long term sustainability. The results are useful to guide extensive, pond-based aquaculture practices in Benin, and the work can be expanded in future through synergy-and-trade-off analysis to quantify potential impacts of stocking density on the wider smallholder aquaculture sector in Benin.

Carry-over and contamination of veterinary drugs in feed production lines for poultry and pigs

ABSTRACTThe current model of pigs and poultry production has increased stocking density and reduced downtime between lots. This scenario may favour a rise of infection and disease risk in animals. To avoid this problem, routine use of drugs has been made, intensifying the possibility of residues in animal products and antimicrobial resistance. The aim of this study was to measure carry-over and contaminants of veterinary drugs included in the feed production lines for poultry and pigs. Samples were taken from 25 production lines. LC-MS/MS was used for simultaneous analysis of 62 active ingredients. In the medicated feed, 80.4% of the samples had a concentration of active ingredients different from the stated doses. In 70% of the feed samples, there was heterogeneity in the mixture of active ingredients. In subsequent feeds, carry-over was greater than 1% of the stated dose in 63% of cases. Of the 25 analysed lines, only one showed no contamination with other active ingredients. No correlations were found between the nutritional composition of the feed and carry-over. The present study demonstrated that the current production model allows the occurrence of unwanted drugs in feed-in doses that can contaminate animal products and can select antimicrobial-resistant bacteria.

Growth Performance of Bluntnose Black Bream, Channel Catfish, Yellow Catfish, and Largemouth Bass Reared in the In‐Pond Raceway Recirculating Culture System

AbstractIn China, the in‐pond raceway system (IPRS) is a novel aquaculture model that was designed to better control water movement to improve water quality and allow for increased stocking density, thus increasing production efficiency and profitability compared to conventional earthen ponds. In this study, two IPRSs were constructed in a 4.13‐ha, annular ecological ditch (circumference waterway) with a mean water depth of 2.5 m. Each raceway (220 m3) consisted of an air‐lift area, a fish culture area, and a waste‐collecting area. The air‐lift system was used to circulate and aerate the water through the culture area, producing a water velocity of 0.03 m/s and a water flow rate of 18 m3/min. This flow rate was equivalent to an average water exchange every 12.2 min for each raceway. Bluntnose Black Bream Megalobrama amblycephala (initial weight = 90 g), Channel Catfish Ictalurus punctatus (initial weight = 150 g), Yellow Catfish Tachysurus fulvidraco (initial weight = 12 g), and Largemouth Bass Micropterus salmoides (initial weight = 10 g) were reared at densities of 16.36, 13.64, 4.36, and 1.14 kg/m3, respectively, with duplicate raceways for each fish species in the IPRSs. The experiment duration for these species was 176, 389, 208, and 412 d, respectively. Total harvest weight was 21,840 kg (5,288 kg/ha) for Bluntnose Black Bream, 17,850 kg (4,322 kg/ha) for Channel Catfish, 12,960 kg (3,138 kg/ha) for Yellow Catfish, and 10,750 kg (2,603 kg/ha) for Largemouth Bass. Daily weight gain for the four species was 2.90, 2.31, 0.81, and 1.19 g·fish−1·d−1, respectively, and the feed conversion ratio was 1.50, 1.85, 1.51, and 1.22, respectively. These results indicate a high potential for more controllable and efficient production of fish in the IPRSs. Design and engineering modifications need to be enhanced in the future to improve IPRS production capabilities.