Grain-based Feed Research Articles

72 Effect of In-feed fecal microbiota transplant on growth performance and gut microbiota dynamics of piglet subjected to post-weaning stress

Abstract Weaning is one of the most stressful events for piglets, due to diet change from sow milk to grain-based feed. This diet change causes turnover of the gut microbial which can allow proliferation of pathogens leading to diarrhea. Antibiotics are administered to treat or prevent post-weaning diarrhea (PWD). Increased occurrence of antimicrobial resistance has increased incentives to develop viable antibiotic alternatives. PWD is most often caused by enterotoxigenic Escherichia coli. Similarly, in humans, severe diarrhea can be caused by Clostridium difficile colonization. Use of fecal microbiota transplants (FMT) has been shown to resolve C. difficile-induced diarrhea in 80 to 90% of human cases which may suggest FMT as a potential therapeutic option for post weaning diarrhea. We previously have shown that in feed fecal microbiota transplant (FMT) improved body weight (BW) gain in newly weaned piglets but it is not clear if this benefit will be replicated in piglets subjected to weaning stress. We hypothesize that FMT (in-feed) will increase colonization efficiency, improve growth performance and reduce diarrhea incidence compared with control in piglets subjected to post weaning stress. The objective of this study was to determine the effect of In-feed FMT of diarrhea index, growth performance and gut microbiota dynamics. Piglets (n = 240) subjected to physiological and transport weaning stress were allotted to 5 treatments: In-feed FMT (FMT1), doubles dose of In-feed FMT1 (FMT2), Oral gavage (FMT3), Antibiotic (positive control), and no supplementation (negative control). The donor material was screened for enterotoxigenic E. coli (F18 and F4). FMT was carried out for 14 d. Diarrhea index was observed for the first 14 d and animal BW, and fecal microbiota was collected by rectal swab on d 0, 3, 5, 7, 14, 21, 28 and 32 for analysis of microbiota composition. DNA was extracted from fecal samples and 16S rRNA gene libraries (V4 region) were prepared for bacterial community analysis. Data were analyzed with one-way ANOVA in R. Only positive control had significantly decrease in diarrhea index and significant increase BW gain on d 14, 21, and 28 (P < 0.05) but there was no effect of FMT (P > 0.05). In conclusion, antibiotics but not FMT was efficient in alleviating the negative performance effect in piglets subjected to post-weaning stress.

277 Effect of Mode of Delivery of Fecal Microbiota Transplants on Growth Performance and Gut Microbiome in Weaning Piglets

Abstract Weaning is one of the most stressful events for piglets, due to diet change from sow milk to grain-based feed. This diet change causes turnover of the gut microbial which can allow proliferation of pathogens leading to diarrhea. Antibiotics are administered to treat or prevent post-weaning diarrhea (PWD). Increased occurrence of antimicrobial resistance has increased incentives to develop viable antibiotic alternatives. Previous studies have shown that fecal microbiota transplant (FMT) reduced diarrhea incidence and improved body weight gain in piglets. However, one barrier to FMT adoption in swine production is that FMT are generally given via oral gavage, which is difficult and labor intensive for large swine operations. For FMT to be a viable option in swine management, a simple method is needed to administer the transplant. The objective of this study was to determine the effect of three methods of FMT administration (oral, rectal and lyophilized in-feed) on growth performance, diarrhea incidence and gut microbiome. We hypothesize that FMT (in-feed and rectal) will increase colonization efficiency, improve growth performance and reduce diarrhea incidence compared with control. Weaned male piglets (n = 40) were allotted to 4 treatments at 10 piglets per treatment (no FMT - Control, Oral gavage - FMT1, rectal gavage - FMT2 and lyophilized in-feed – FMT3). Feces from 12-week-old pigs, screened for pathogens, was donor material. The study lasted nine days and FMT was for five days. Diarrhea incidences and body weight were observed for the first week. Fecal samples were collected on days 0, 2, 5 and 7. Five piglets per group were sacrificed on day 4 and the remaining on day 8. Cecal and colon contents were collected from the sacrificed piglets. DNA was extracted from fecal and digesta samples and 16S rRNA gene libraries (V4 region) were prepared for bacterial community analysis. Data were analyzed with one-way ANOVA in R. All FMT groups had significantly greater body weight on day 3 (P < 0.05) and average daily gain between day 0 – 3 (P < 0.05) compared with control but there was no difference between FMT groups. There was no effect of FMT on average daily feed intake and diarrhea incidence. Only FMT3 had greater alpha diversity (Observed features and Faith’s phylogenetic diversity) on day 5 (P < 0.05) compared with control, but there was no difference in beta diversity between FMT groups. There was decreased abundance of 27 ASVs (amplicon sequence variant) and increased abundance of 30 ASVs in increased in FMT3 compared with control on day 5. In conclusion, the three FMT groups has similar colonization pattern but there was no difference in diarrhea incidence. FMT3 (lyophilized in-feed) altered overall community structure of piglets and modulated individual taxa.

NEW FEED ENZYME PREPARATIONS FOR THE DESTRUCTION OF NON-STARCH POLYSACCHARIDES AND PHYTATES

New recombinant strains of Penicillium verruculosum have been created with a high level of expression of homologous endo-β-1,4-glucanase II and heterologous phytase A A. niger, as well as heterologous endo-1,4-β-xylanase E P. canescens and phytase A A. niger, allowing to obtain highly active feed enzyme preparations (AF) capable of simultaneously signi cantly reducing viscosity non-starch polysaccharides, as well as increase the bioavailability of phosphorus and minerals of grain-based feed and, thus, increase the digestibility of nutrients of agricultural animal and poultry feed. Speci c AF activities for speci c substrates (xylanau, β-glucan, phytate) were studied, the qualitative and quantitative component composition of new AF was determined. On the basis of a new enzyme preparation containing homologous endo-β-1,4-glucanase II and heterologous phytase A A. niger, a recipient strain ∆nia D - was obtained, into which heterologous endo-1,4-β-xylanase E P. canescens was successfully cloned and, thus, a promising producer of three target enzymes was obtained simultaneously.

Fatty Acid Composition of Grain- and Grass-Fed Beef and Their Nutritional Value and Health Implication.

Beef contains functional fatty acids such as conjugated linoleic acid and long-chain fatty acids. This review summarizes results from studies comparing the fatty acid composition of beef from cattle fed either grass or grain-based feed. Since functional lipid components are contributed through dietary consumption of beef, the fatty acid composition is reported on mg/100 g of meat basis rather than on a percentage of total fat basis. Beef from grass-fed contains lesser total fat than that from grain-fed in all breeds of cattle. Reduced total fat content also influences the fatty acid composition of beef. A 100 g beef meat from grass-fed cattle contained 2,773 mg less total saturated fatty acids (SFA) than that from the same amount of grain-fed. Grass-fed also showed a more favorable SFA lipid profile containing less cholesterol-raising fatty acids (C12:0 to C16:0) but contained a lesser amount of cholesterol-lowering C18:0 than grain-fed beef. In terms of essential fatty acids, grass-fed beef showed greater levels of trans-vaccenic acid and long-chain n-3 polyunsaturated fatty acids (PUFA; EPA, DPA, DHA) than grain-fed beef. Grass-fed beef also contains an increased level of total n-3 PUFA which reduced the n-6 to n-3 ratio thus can offer more health benefits than grain-fed. The findings signify that grass-fed beef could exert protective effects against a number of diseases ranging from cancer to cardiovascular disease (CVD) as evidenced by the increased functional omega-3 PUFA and decreased undesirable SFA. Although grain-fed beef showed lesser EPA, DPA, and DHA, consumers should be aware that greater portions of grain-fed beef could also achieve a similar dietary intake of long-chain omega-3 fatty acids. Noteworthy, grain-fed beef contained higher total monounsaturated fatty acid that have beneficial roles in the amelioration of CVD risks than grass-fed beef. In Hanwoo beef, grain-fed showed higher EPA and DHA than grass-fed beef.

Isolation and identification of phytate-degrading yeast from traditional fermented food

Abstract. Suryani AE, Anggraeni AS, Istiqomah L, Damayanti E, Karimy MF. 2021. Isolation and identification of phytate-degrading yeast from traditional fermented food. Biodiversitas 22: 866-873. Application of phytase (myo-inositol hexakisphosphate phosphohydrolase) to catalyze the release of phosphate from phytates contained on grain-based feed has been used widely in poultry feed industry. In this study, yeast as phytase producer from traditional fermented food was isolated, screened and identified their morphological, biochemical, and molecular characteristics. Production of extracellular phytase from yeast was quantified using spectrophotometer. The results showed that among 8 yeast isolates that had phytase activity, there were two isolates with the highest phytase activity and specific activity which were TKd3 isolate (6.57 U/mL and 54.230 U/mg) and GF1 (6.07 U/mL and 53.68 U/mg). Morphological identification using Scanning Electron Microscope revealed that TKd3 cells isolated from soybean tempeh had an elongated oval cell structure, whereas the GF1 isolated from fresh gatot had a rounder cell structure. TKd3 isolate with accession number MW131530 had homology with Candida tropicalis ATCC 750 28S rRNA with 99.83% similarity and GF1 isolate with accession number MW131531 had homology with Candida tropicalis ATCC 750 28S rRNA with 100% similarity. It could be concluded that C. tropicalis yeast from traditional fermented food produced the extracellular phytase for further use of phytase in poultry feed additive.

“Legumix” Stylosanthes pellets: A healthier and more sustainable animal feed

The development of a range of animal feeds based on leaf meal of the tropical forage legume Stylosanthes guianensis var. guianensis (“tropical alfalfa”) in Costa Rica, their potential for improving health of animals and consumers of animal products, the local and national economy, and ecological implications are described. A subproduct of the oil palm industry (palm oil fatty acid distillate) is used to supplement the Stylosanthes leaf meal with sufficient energy to produce a complete pelleted feed. Customer case studies showed that Stylosanthes-based feeds are highly palatable and improve health and performance of farm animals (horses, rabbits, calves, sheep, and goats) over that observed when using grain-based feeds. The improved quality of Stylosanthes-based over grain-based feed for ruminants could play an important role in the reduction of methane emissions and their negative consequences for climate change. A sustainable system whereby Stylosanthes is planted in association with plantation trees is proposed, providing a supplementary income for tree farmers and other benefits, such as weed control and soil amelioration. Stylosanthes can be rotated with sugarcane and pineapple, and cash flow projections show that Stylosanthes leaf meal production would be a favorable alternative activity for local farmers, yielding a greater and more constant income than sugarcane. Achieving economy of scale in the industrial process would permit production at lower cost to compete with the price of imported grain-based feed. Lack of finance is currently the major obstacle to scaling up the process, implementing the technology in different countries, and obtaining the concomitant benefits of food security, import substitution, improved ecological sustainability, and healthiness of animal products.

Enniatin B1-induced lysosomal membrane permeabilization in mouse embryonic fibroblasts

The mycotoxin enniatin B1 (ENN B1) is widely present in grain-based feed and food products. In the present study, we have investigated how this lipophilic and ionophoric molecule can affect the lysosomal stability and chaperone-mediated autophagy (CMA) in wild-type (WT) and in lysosome-associated membrane proteins (LAMP)-1/2 double-deficient (DD) mouse embryonic fibroblasts (MEF). The cell viability and lysosomal pH were assessed using the Neutral Red (NR) cytotoxicity assay and the LysoSensor® Yellow/Blue DND-160, respectively. Changes in the expression of the CMA-related components LAMP-2 and the chaperones heat shock cognate (hsc) 70 and heat shock protein (hsp) 90 were determined in cytosolic extracts by immunoblotting. In the NR assay, LAMP-1/2 DD MEF cells were significantly less sensitive to ENN B1 than WT MEF cells after 24h exposure to ENN B1 at levels of 2.5-10μmol/L. Exposure to ENN B1 at concentrations below the half maximal effective concentration (EC50) (1.5-1.7μmol/L) increased the lysosomal pH in WT MEF, but not in LAMP-1/2 DD cells, suggesting that lysosomal LAMP-2 is an early target of ENN B1-induced lysosomal alkalization and cytotoxicity in MEF cells. Additionally, cytosolic hsp90 and LAMP-2 levels slightly increased after exposure for 4h, indicating lysosomal membrane permeabilization (LMP). In summary, it appeared that ENN B1 can destabilize the LAMP-2 complex in the lysosomal membrane at concentrations close to the EC50, resulting in the alkalinization of lysosomes, partial LMP, and thereby leakage of CMA-associated components into the cytosol.

Optimal dairy feed input selection under alternative feeds availability and relative prices

Feed formulation is essential in the dairy production chain from economic, nutritional, and environmental perspectives. Optimizing the feed formulation across those three domains – given uncertainty of input prices, input availability, and regional climatic conditions – is a challenge for those in the industry. The diet formulation method that is widely used by trading firms and feed production facilities employs a static linear programming (LP) approach. This approach does not allow for intertemporal feed formulations and switches between dietary feed commodities under feed availability conditions, which result in foregone economic gains for feed producers.The current study develops a multi-period LP feed model that uses historical data to capture ration switch opportunities between available feed resources for dairy cows and demonstrates the potential use of the method in different commodity feed availability situations. We apply 14 diet formulations, each covering 150 months, representing a total of 2100 diets. The diet formulation considers a specific milk production level for a “model cow”, alternative feed formulations available, and volatility in feed prices. The results demonstrate that there is an opportunity for efficiency gains in the dairy industry with respect to feed formulation.Based on dietary feed inclusion and price spreads, barley can be an important dairy feed grain which completely replaces wheat, corn, and sorghum at price spreads of less than 94%, less than 78%, and less than 67%, respectively. Grain-based feed scenarios represent the lowest nutrient variation while multiple meal feeds had the lowest costs. Furthermore, and on average, multiple meal feed scenarios provided 10% higher dietary crude protein contents compared to grain based feed scenarios (i.e. 163 vs 179 g/kg DM formulated feed). Meanwhile, multiple meal feeding cost was 11% lower than that in the grain based feeding scenarios. Additionally, the use of multiple meals reduces alfalfa dietary inclusion by 7% on dry matter basis. Our analysis shows a strong reduction in feed cost associated with dietary crude protein reduction equivalent to 7.6 USD/tonne per 1% reduction in dietary crude protein level.The modeling approach allows for the interaction between feed components over time taking into consideration volatile global feed prices, thereby improving feed availability and feed formulation. Overall, the model provides a decision making tool to improve the use of feed resources in the dairy sector.

The occurrence of mycotoxigenic fungi in abalone feed in South Africa

Abalone feed in South Africa is mainly produced from locally sourced grains and has soy or fishmeal as a protein source. Contamination with fungal species associated with grain-based animal feed is, therefore, a predictable risk. Various Fusarium, Penicillium and Aspergillus species are known to produce mycotoxins when colonising grains. The aim of this study was to investigate the occurrence of toxigenic fungal species in the ingredients of compound abalone feeds as well as in final abalone-feed products. In this study, 248 fungal isolates were obtained from feed ingredients and compound abalone feeds collected from three different South African abalone farms and one feed supplier. Morphological and multigene phylogenetic analyses were used to identify the fungi isolated. Fusarium, Penicillium and Aspergillus species were consistently isolated. The presence of these species does not always result in mycotoxin contamination.

LivestockPlus: Forages, sustainable intensification, and food security in the tropics.

The increased use of grain-based feed for livestock during the last two decades has contributed, along with other factors, to a rise in grain prices that has reduced human food security. This circumstance argues for feeding more forages to livestock, particularly in the tropics where many livestock are reared on small farms. Efforts to accomplish this end, referred to as the 'LivestockPlus' approach, intensify in sustainable ways the management of grasses, shrubs, trees, and animals. By decoupling the human food and livestock feed systems, these efforts would increase the resilience of the global food system. Effective LivestockPlus approaches take one of two forms: (1) simple improvements such as new forage varieties and animal management practices that spread from farmer to farmer by word of mouth, or (2) complex sets of new practices that integrate forage production more closely into farms' other agricultural activities and agro-ecologies.

Wildlife Visitation on a Multi-Unit Educational Livestock Facility in Northwestern Georgia

Wildlife visitation of livestock facilities results in economic losses through feed consumption and a potential for disease transmission through fecal contamination of feeds and associated facilities. In order to assess wildlife visitation among livestock-management teaching units on a college campus, we monitored feeding and feed-storage areas via direct observations, live-trapping, and motion-detecting cameras. We also examined visitation patterns and fecal contamination and consumption of grain-based feed and hay. Nine species of wildlife visited the livestock units during the course of the study. Birds and Odocoileus virginianus (White-tailed Deer) were the most frequent visitors in less-enclosed facilities, and rodents, Didelphis virginiana (Virginia Opossum), and Procyon lotor (Raccoon) were mostly documented in more-enclosed facilities. Birds visited daily throughout the year, but documented visitations by Raccoons, Virginia Opossums, and White-tailed Deer occurred only during summer months. Marmota monax (Groundhog) were present each month except for January, February, and March. Of 827 feed samples examined, 16.8% were contaminated by wildlife feces, primarily from birds. Grain-based feed was consumed or removed more frequently than hay, and loss declined during the winter and increased in spring and summer.

Measurement and mitigation of methane emissions from beef cattle in tropical grazing systems: a perspective from Australia and Brazil

The growing global demand for food of animal origin will be the incentive for countries such as Australia and Brazil to increase their beef production and international exports. This increased supply of beef is expected to occur primarily through on-farm productivity increases. The strategies for reducing resultant greenhouse gas (GHG) emissions should be evaluated in the context of the production system and should encompass a broader analysis, which would include the emissions of methane (CH4) and nitrous oxide (N2O) and carbon sequestration. This paper provides an insight into CH4 measurement techniques applicable to grazing environments and proposed mitigation strategies, with relevance to the production systems that are predominant in grazing systems of Australia and Brazil. Research and technology investment in both Australia and Brazil is aimed at developing measurement techniques and increasing the efficiency of cattle production by improving herd genetics, utilization of the seasonal feed-base and reducing the proportion of metabolizable energy lost as CH4. Concerted efforts in these areas can be expected to reduce the number of unproductive animals, reduce age at slaughter and inevitably reduce emission intensity (EI) from beef production systems. Improving efficiency of livestock production systems in tropical grazing systems for Australia and Brazil will be based on cultivated and existing native pastures and the use of additives and by-products from other agricultural sectors. This approach spares grain-based feed reserves typically used for human consumption, but potentially incurs a heavier EI than current intensive feeding systems. The determination of GHG emissions and the value of mitigation outcomes for entire beef production systems in the extensive grazing systems is complex and require a multidisciplinary approach. It is fortunate that governments in both Australia and Brazil are supporting ongoing research activities. Nevertheless, to achieve an outcome that feeds a growing population while reducing emissions on a global scale continues to be a monumental challenge for ruminant nutritionists.

Establishment of intestinal microbiota with focus on yeasts of unweaned and weaned piglets kept under different farm conditions

This study aimed to characterize the intestinal yeasts in weaning piglets and to establish their possible relationships with main bacterial groups. German Landrace piglets were weaned (WP, n=32) at 28 days of age or kept with the dams until day 39 without creep feed (UP, n=32). The experiment was performed at an experimental and a commercial farm (CF). Faeces were collected from the piglets, sows and pen floors on days 28, 33 and 39 for isolation of DNA and cultivation for enumeration of yeasts, enterobacteria, enterococci and lactobacilli. Fragments of the D1 domain of 26S rRNA gene were amplified and separated by denaturing gradient gel electrophoresis (DGGE). No yeasts could be cultured from water and feed samples. No or only low numbers of yeasts were detected among all UP. In WP at CF, yeasts correlated with lactobacilli (r=0.456; P=0.009) and enterobacteria (r=-0.407; P=0.021). Kazachstania slooffiae dominated among the cultured yeasts. It was the only yeast species detected by PCR-DGGE. Yeasts, especially K. slooffiae, established in the porcine gastrointestinal tract after consumption of grain-based feed and may interrelate with the intestinal microbiota. The study provides data indicating importance of K. slooffiae for the development of balanced porcine gut microbiota.

Ewe’s Diet (Pasture vs Grain-Based Feed) Affects Volatile Profile of Cooked Meat from Light Lamb

The effects of ewe's diet during gestation and lactation on the volatile compounds profile in cooked meat from light lamb were compared. Two lamb groups from ewes that had been fed pasture (PA) or grain-based concentrate (FE) were tested. Cooked loin mixed with saliva was analyzed by solid phase microextraction, gas chromatography, and mass spectrometry. The fiber coating used was divinylbenzene-carboxen-polydimethylsiloxane. The volatiles detected and quantified were aldehydes, alcohols, ketones, phenols, indole, and sulfur compounds. The ewe's diet strongly affected the volatile compounds profile of the cooked meat. The total volatiles concentration was higher in PA (409 mg kg(-1)) than in FE (201 mg kg(-1)). The major volatiles in PA were phenol, 4-methylphenol, and hexanoic acid, while the major volatile in FE was 3-hydroxy-2-butanone. No branched C8-C9 fatty acids responsible for mutton flavor were detected in either group. The findings suggest that nutritional strategies can be use during gestation and lactation to modify the aroma of light lamb meat in the light of consumer preferences.

Cloth-Based Hybridization Array System for Expanded Identification of the Animal Species Origin of Derived Materials in Feeds

A cloth-based hybridization array system (CHAS) previously developed for the detection of animal species for which prohibited materials have been specified (cattle, sheep, goat, elk, and deer) has been expanded to include the detection of animal species for which there are no prohibitions (pig and horse) in Canadian and American animal feeds. Animal species were identified by amplification of mitochondrial DNA sequences by PCR and subsequent hybridization of the amplicons with an array of species-specific oligonucleotide capture probes immobilized on a polyester cloth support, followed by an immunoenzymatic assay of the bound PCR products. The CHAS permitted sensitive and specific detection of meat meals from different animal species blended in a grain-based feed and should provide a useful adjunct to microscopic examination for the identification of prohibited materials in animal feeds.

Feeding livestock food residue and the consequences for the environmental impact of meat

The environmental impact of meat is high mainly due to the feed required by livestock in combination with the impacts of cultivating, transporting and processing of feed crops such as tapioca and grains. Like regular feed crops, livestock also feed on residue from the food industry, such as pulp, scrap and peels. Both types of raw material have different environmental impacts. Feeding food residue to livestock is an efficient way to upgrade a low quality material into high quality foods. In the Netherlands, food residue represents the majority of the feedstock for feed. Distinguishing crops from food residue has consequences for the ascribed environmental impact of meat. This paper separates these two streams using volume, environmental impact and their relevance in meat production. An assessment is made of three food industries (sugar beet industry, vegetable oil industry and potato product industry) that produce the largest stream of food residue, and of the pork industry, as an example of meat production. The environmental impact of food residue-based feed is allocated in three different ways: mass ratio, economic basis, and no assigned burden. We found that the amount of pork produced from food residue is substantial. The environmental impact of food residue-based feed is also significantly lower than grain-based feed. We discuss changes in vegetable and in animal product consumption that influence the environmental impact of pork. It is concluded that the use of current food residue keeps the environmental impact of livestock foods relatively low. However, a further increase in meat consumption would require more feed grains with a correspondingly larger environmental impact because food residues are used up.

Carcass treatments for improved meat quality (In Swedish with Summary in English)

Meat quality is a term that includes many different aspects like e.g. safety, ethics, nutrition, taste and functionality. What is regarded as most important is mainly related to where a person is placed in the chain from production to consumption. Along this chain are also many factors that influence the quality of meat. By measuring the pH value of meat it is possible to get good information about shelf life, tenderness, colour and water-holding capacity. Meat pH also gives an indication to whether the animals have been exposed to stress prior to slaughter or not. Good pastures and supplementary feeding using grain-based feed mixtures have been demonstrated to increase the energy stores in the animals' muscles and therefore have a positive effect on pH values in venison. What the animals had been eating prior to slaughter also affected the fat composition and meat flavour. Meat from animals grazing pasture had more polyunsaturated fatty acids and a "wild" flavour compared with meat from animals fed grain-based pellets. It is possible to change the fat composition in a commercial grain-based feed mixture, without altering the protein or energy content, so that the fat composition mimic that of a natural pasture. Pelvic suspension of a carcass will stretch the muscles in valuable cuts and improve the tenderness of the meat. In fallow deer carcasses the tenderness was improved in several meat cuts and in addition the water-holding capacity of the meat increased after pelvic suspension. Electrical stimulation of the carcass quickly empties the energy stores in the muscles and accelerates the onset of rigor mortis. In red deer venison electrical stimulation accelerated the rate of meat tenderisation, but this benefit was lost after approx. 3 weeks of ageing (-1.5 °C). A study from Alaska demonstrated no effects of electrical stimulation of reindeer carcasses on meat tenderness or water-holding capacity. We recommend further studies of pelvic suspension and electrical stimulation to get a better understanding of their effects on venison quality and to be able to implement these techniques in the most optimal way.

Nutrient and microbial dynamics in high-intensity, zero-exchange shrimp ponds in Belize

Microbial and phytoplankton processes, and their effect on water quality were examined over a 3-week period in five high-intensity (120 animals m −2) shrimp ( Litopenaeus vannamei) ponds of varying crop ages at Belize Aquaculture Ltd., (BAL) in Central America. These ponds were characterized by zero water exchange throughout the crop, plastic lining and high aeration rates. Nitrogen (N) and organic carbon (C) inputs, in the form of fishmeal-based feed, grain-based feed and molasses, resulted in high concentrations of dissolved organic and inorganic N (2.29–5.56 and 0.17–10.66 mg l −1, respectively) and dissolved organic C (14.20–48.10 mg l −1). Phosphate levels were also high, ranging from 0.07 to 1.17 mg l −1. The high nutrient concentrations promoted the growth of bacteria, phytoplankton (mostly autotrophic flagellates) and protozoa. Up to 40% of the bacteria were associated with flocculated matter. However, bacterial numbers and oxygen (O 2) consumption in the water column did not appear to increase with crop age. This may be due to a reduction in the C/N ratio below the optimum for bacterial growth. Up to 22% of the O 2 consumption was due to nitrification and there was some indication of lowering of total ammoniacal N (TAN) concentrations and an increase in nitrite and nitrate levels in older crops. Both phytoplankton and bacteria were responsible for high rates of ammonium uptake. In ponds with high nitrate concentrations, nitrate uptake rates were also high. Phytoplankton productivity remained high irrespective of crop age and ponds fluctuated between net O 2 production (autotrophy) and net O 2 consumption (heterotrophy) irrespective of crop age. This reflected the highly dynamic nature of the bacterial and phytoplankton populations with frequent blooms and crashes of individual phytoplankton species. The high mixing rates resulted in phytoplankton and other detritus remaining suspended in the water column. However, a small area of sludge (<2% of pond area) did accumulate containing a high N and C content, and high pore water TAN. This study showed that despite what is generally considered as poor water quality in the ponds, i.e. high nutrient concentrations, high and unstable phytoplankton numbers, and high bacterial numbers, shrimp production was high relative to conventional ponds. There appeared to be scope for increasing bacterial production in these systems by increasing the C/N ratio, and hence C availability for bacterial growth. However, it remains to be established which microbial processes are likely to be promoted, and if the benefits of this outweigh the costs.

Sigma ligand-induced emesis in the pigeon

Pigeons were fed a fixed amount of grain-based feed and behavior was observed after administration of doses of ditolyguanidine (DTG), (+)-3-(3-hydroxyphenyl)-N-(1-propyl)-piperidine [(+)-3-PPP], dextromethorphan, haloperidol, (+)-N-allylnormetazocine (NANM), alpha-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine-butanol (BMY-14802) apomorphine, pentobarbital, propranolol, and MK-801. Of the drugs tested, DTG, dextromethorphan, and (+)-3-PPP each produced dose-related increases in the percentage of pigeons exhibiting an emetic response. The emetic response produced by DTG was antagonized by haloperidol and BMY-14802 but not by propranolol. These observations suggest that the emetic response in the pigeon may be mediated by sigma sites and is unlikely to be mediated by phencyclidine receptors.