Antibiotic-free Feed Research Articles

A choice experiment for different preparation methods of eggs: The impact of sensory, health, and animal welfare

The risk of salmonella food poisoning increases the lower the degree of heating the eggs.This study investigated the effect of cooking methods on the willingness to pay (WTP) for sterilization method.The choice experiment consisted of eight attributes; yolk color (yellow vs. orange), grade (special vs. first grade), omega-3 (3 levels), egg sterilization method (no sterilization vs. sodium hypochlorite vs. pasteurization), hen feed (antibiotics vs. antibiotic-free vs. organic), hen’s breeding method (caged vs. cage-free), production area (in-prefecture vs. outside of prefecture), and price (5 levels).The online survey included 1,000 Japanese consumers. A within-design was employed in which everyone responded under the assumptions of eating a hard-boiled egg, a soft-boiled egg, and a raw egg.As the degree of heating decreased, the WTP for the sterilization attribute became higher. Sodium hypochlorite was always higher than pasteurization. As the degree of rawness increased, the WTP of antibiotic-free and organic feed rise. However, the organic feed had a lower WTP than the antibiotic-free feed. When eating raw eggs, the WTP of antibiotic-free was the second important compared with the sterilization. As the degree of rawness increased, the WTP of the orange color of the yolk rise, and finally reached three times higher when eating raw eggs than when eating hard-boiled eggs. The WTP of local production was not significantly different in any case. Omega-3 had a significant negative WTP only for raw eggs. Cage-free had a significant negative WTP only for boiled eggs.

Non-antibiotic feed additives production by Acremonium terricola solid-fermented Camellia oleifera meal

The Camellia oleifera meal (COM), a primary byproduct of oil-tea processing, often being discarded or used as a low-grade fertilizer due to its low value. The underutilization has become a significant bottleneck hindering the high-quality development of the oil-tea industry. In this study, the production of antibiotic-free feed additives through the solid-state fermentation of COM by Acremonium terricola was investigated. Our findings revealed that a saponin concentration of 5 mg/mL significantly enhanced the production of cordycepic acid (70.4 mg/g), ergosterol (3.32 mg/g), and chitin (110 mg/g) by A. terricola. This concentration also promoted chitin production and the activities of peroxidase (POD) and Na+/K+-ATPase, thereby maintaining cellular homeostasis and energy balance in A. terricola. Solid-state fermented rice bran (RB), wheat bran (WB), and desaponificated COM (containing 2.6 mg/100 g of tea saponin) were all found to be beneficial for increasing the production of cordycepic acid and ergosterol. The blend of COM, RB, and WB in the ratio of 15:65:20 was particularly advantageous for the production and accumulation of cordycepic acid and ergosterol, yielding 1.54 and 1.43 times, 1.27 and 1.37 times, and 1.98 and 5.52 times more than those produced by WB, RB, and COM alone, respectively.Meantime, the difference in contents of sugar and protein in A. terricola cultures (ATCs) using combination were not significant compared to RB and WB. These results indicated that COM can partially replace foodstuffs or food by-products to prepare antibiotic-free feed additives by A. terricola.Graphical

Dietary Supplementation of Lactococcus lactis subsp. lactis BIONCL17752 on Growth Performance, and Gut Microbiota of Broiler Chickens.

The rapid rise of antimicrobial resistance (AMR) is a global concern, being triggered by the overuse or misuse of antibiotics in poultry farming sector. We evaluated Lactococcus lactis subsp. lactis BIONCL17752 strain, and characterized its probiotic potential to endure hostile gastrointestinal conditions. Genome sequencing analysis revealed probiotics traits, and gene clusters involved in bacteriocins, lactococcin A, and sactipeptides production. The absence of genes for antibiotic resistance, virulence, and biogenic amine production indicates the potential of probiotic strain. The BIONCL17752 strain was explored for antibiotic-free feed supplement for growth promotor in broiler chicken. The feed supplemented with 4 × 109CFU/kg of probiotic strain, in combination with various concentrations of fructooligosaccharides (FOS) 1.0, 2.5, and 5.0kg/tonne in starter, grower, and finisher diets, respectively. A significant improvement of body weight 152 to 171g/bird (p < 0.05), and a low feed conversion ratio (FCR) of 1.62, was achieved without using synthetic antibiotics for growth promotion. The results of biochemical, hematological, and histological examinations showed normal features, indicating that the treatment had no harmful effects on the bird's health. Reduced levels of cholesterol, triglycerides, high-density lipoprotein(HDL), and low-density lipoprotein (LDL) in serum are an indication of the health benefits for the treated birds. Microbial community analysis of fecal samples of poultry birds exhibited a higher abundance of Bacteroidetes, Firmicutes, Proteobacteria, Actinobacteria, and Fusobacteria. Probiotic treatment resulted in reduced Firmicutes and increased Bacteroidetes (F/B ratio) in the broiler's gut which highlights the benefits of probiotic dietary supplements. Importantly, the probiotic-fed group exhibited a high abundance of carbohydrate-active enzymes (CAZyme) such as glycoside hydrolases (GH), glycoside transferases (GT), and carbohydrate-binding module (CBM) hydrolases which are essential for the degradation of complex sugar molecules. The probiotic potential of the BIONCL17752 strain contributes to broilers' health by positively affecting intestinal microbiota, achieving optimal growth, and lowering mortality, demonstrating the economic benefits of probiotic treatment in organic poultry farming.

Microbiome, Transcriptome, and Metabolomic Analyses Revealed the Mechanism of Immune Response to Diarrhea in Rabbits Fed Antibiotic-Free Diets

In this study, diarrhea was induced in rabbits by feeding them antibiotic-free feed. The gut provides important defense against the barriers of the body, of which the duodenum is an important part to help digest food and absorb nutrients. However, the mechanisms underlying the roles of the gut microbiome and fecal metabolome in rabbit diarrhea caused by feeding an antibiotic-free diet have not been characterized. Recently, only a single study has been conducted to further characterize the antibiotic-free feed additives that caused diarrhea in weaned rabbits. The multi-omics techniques, including 16S rRNA sequencing, transcriptome sequencing, and LC-MS analysis, were combined to analyze the gut microbial compositions and functions. They also determined the fecal metabolomic profiles of diarrhea in rabbits caused by feeding antibiotic-free feed. The results showed that the liver, duodenal, and sacculus rotundus tissues of diarrhea rabbits were diseased, the composition of intestinal microbes was significantly changed, the diversity of intestinal microbes was decreased, and the distribution of intestinal microbe groups was changed. Functional analysis based on the cluster of GO and KEGG annotations suggested that two functional GO categories belonged to the metabolism cluster, and five KEGG pathways related to the metabolic pathways were significantly enriched in diarrhea rabbits. Moreover, real-time quantitative PCR (RT-qPCR) was used to verify the significant expression of genes related to diarrhea. Metabolomics profiling identified 432 significantly differently abundant metabolites in diarrhea rabbits, including amino acids and their derivatives. These amino acids were enriched in the tryptophan metabolic pathway. In addition, the functional correlation analysis showed that some altered gut microbiota families, such as Parasutterella, significantly correlated with alterations in fecal metabolites. Collectively, the results suggested that altered gut microbiota was associated with diarrhea caused by antibiotic-free feed additives in weaned rabbit pathogenesis.

Higher tolerance of predominant Salmonella serovars circulating in the antibiotic-free feed farms to environmental stresses

To counteract the dramatic increase in antibiotic-resistant bacterial pathogens, many countries, including China, have banned the use of antibiotic-supplemented feed for farming animals. However, the exact consequences of this policy have not been systematically evaluated. Therefore, Salmonella isolates from farms that ceased using antibiotics 1–5 years ago were compared with isolates from farms that continue to use antimicrobials as growth promotors. Here, we used whole-genome sequencing combined with in-depth phenotypic assays to investigate the ecology, epidemiology, and persistence of multi-drug resistant (MDR) Salmonella from animal farms during the withdrawal of antibiotic growth promotors. Our results showed that the prevalence of Salmonella was significantly lower in antibiotic-free feed (AFF) farms compared to conventional-feed (CF) farms, even though all isolates obtained from AFF farms were MDR (>5 classes) and belonged to well-recognized predominant serovars. The additional phylogenomic analysis combined with principal component analysis showed high similarity between the predominant serovars in AFF and CF farms. This result raised questions regarding the environmental persistence capabilities of MDR strain despite AFF policy. To address this question, a representative panel of 20 isolates was subjected to disadvantageous environmental stress assays. These results showed that the predominant serovars in AFF and CF farms were more tolerant to stress conditions than other serovars. Collectively, our findings suggest that AFF helps eliminate only specific MDR serovars, and future guiding policies would benefit by identifying predominant Salmonella clones in problematic farms to determine the use of AFF and additional targeted interventions.

A 3-week post-weaning restricted feeding as alternative to an ad libitum antibiotic-medicated feed: Effects on growth, carcass and meat of rabbits differing in genotype and slaughter age

In this investigation, the impact of a 3-week post-weaning restricted feeding (RF) using an antibiotic-free feed, applied to rabbits from 36 to 56 days of age to preserve their health status as alternative to an ad libitum medicated feed with antibiotics (AMF), was verify in relation to rabbit genotype and slaughter age (SA). The RF and AMF treatments were compared evaluating their effects on feed intake, growth, mortality, carcass and meat quality of rabbits of two genotypes, Italian White purebred (IWP) and hybrid Hycole×IWP crossbred (HIWC), slaughtered at 78 or 92 days of age to obtain light or heavy carcasses. At 36 days of age, 256 weaned rabbits of both sexes were divided into 4 homogeneous groups based on feeding treatment (FT) and genotype: RF-IWP, RF-HIWC, AMF-IWP and AMF-HIWC. The RF treatment was performed offering to each rabbit 70, 80 and 90 g/day of feed in the 1st, 2nd and 3rd week. After the 3-week RF and AMF treatments, all rabbits received the same ad libitum antibiotic-free feeds until their slaughter. For each group, 24 rabbits were slaughtered, 12 at 78 days and 12 at 92 days. On the whole feed intake with RF was equal to 63% of that with AMF. Regardless of genotype, RF was associated with a lower feed intake until 78 days and a compensatory growth from 58 to 78 day, whereas from 79 to 92 days intake was not affected by FT and genotype. Despite the compensatory growth, the lower intake of restricted rabbits resulted in lower live weight at 78 and 92 days, but in more favourable feed conversion than with AMF. The growth potential allowed the crossbred rabbits to reach higher body and carcass weights with more efficient feed utilization. Mortality for enteropathies occurred mainly during the post-weaning phase from 36 to 56 days of age, with no difference due to FT, whereas HIWC rabbits showed a lower resistance to enteropathies. Heavier and fatter carcasses were obtained from AMF rabbits, at both SA, whereas the heavier HIWC carcasses showed a lower fat content than IWP ones. Carcass yield was influenced by FT and SA, being lower in RF rabbits and at earlier age. The restriction affected some colour indexes of meat and induced lower adiposity. Collagen was higher in meat of 92-day rabbits and in males, with no relationship to shear force. No particular effect of genotype emerged for meat quality. On the whole a 3-week post-weaning RF with antibiotic-free feed is confirmed to be a suitable method to replace an ad libitum feed containing antibiotics. In addition, RF appeared more suitable for rabbits of high-growth genotype slaughtered at 92 days which were more effective to recover the growth slowing due to the post-weaning feed restriction.

Chinese medicinal materials industry during the 14th Five-Year Plan period: trends and development suggestions

This study steps through the future perspectives and gives the development suggestions of Chinese medicinal materials(CMM) industry by presenting the characteristics and open problems during the 13 th Five-Year Plan period. The development of CMM industry presents the following trends:(1)the development of Dao-di herbs speeds up with the increasing demand for high-quality CMM;(2)the mismatch between supply and demand is aggravating, which presses for supply-side structural reform;(3)ecological planting will become the core mode of production and bolster rural revitalization;(4)the demand for CMM with both medical and edible values keeps growing, and the antibiotic-free feed policy brings significant opportunities;(5)the &quot;Internet Plus CMM&quot; wave emerges, which promotes the construction of traceability system. Finally, we put forward the following suggestions for the sustainable development of CMM industry:(1)optimizing the layout for the production of Dao-di herbs according to local conditions;(2)strengthening the commercialization of the seeds and the breeding, multiplication, and extension of CMM to accelerate the realization of specialized seed production, mechanized seed processing, localized variety layout, and county-based unified seed supply;(3)ensuring the safety of pesticide use and accelerating the registration of special pesticides;(4)promoting both theoretical and practical research on ecological production of CMM;(5)publicizing the demonstration and popularization of CMM traceability system. Overall, significant progress has been achieved in the CMM industry during the 13 th Five-Year Plan period, and this industry is in a critical stage of high-quality development, facing both challenges and opportunities.

Safety evaluation study of lincomycin and spectinomycin hydrochloride intramuscular injection in chickens

This study aimed to investigate the nonclinical safety of lincomycin and spectinomycin hydrochloride (LC-SPH) intramuscular (i.m) doses on target animals (chickens) to provide guidelines for dose level design and side effect monitoring in clinical trials.A total of 80 healthy Arbor Acres plus broiler chicks were completely randomized and blindly divided into four treatment groups (control, one-time dose, three-time dose, and five-time dose) of 20 chicks each (20 chickens per group). At the age of day 15, all chickens (except the control group) were administered LC-SPH intramuscularly (chest muscles) at different doses of 20 mg/kg.bw, 60 mg/kg.bw, and 100 mg/kg.bw respectively for 9 consecutive days recommended by veterinary international cooperation on harmonization (VICH) guidelines. The chickens had ad libitum access to antibiotic-free feed and water. Feeding chickens were observed twice a day throughout the study. The drug safety was evaluated by complete blood count, biochemical parameters, histopathological, clinical signs, body weight gain, and feed conversion ratio (FCR).Hence, considering the minor toxicity of 60 mg/kg, our results reveal that intramuscular injection of at least 20 mg/kg body weight has no effects on growth performance, clinical blood parameters, organ coefficient, and histopathological parameters. Thus, a combination of LC-SPH 20 mg/kg body weight i.m injection investigated safe followed daily administration for nine consecutive days in healthy chickens.It is concluded that the experimental results support the safety of 20 mg/kg body weight in combination for the further clinical research study.

Untargeted Metabolomics Reveals Intestinal Pathogenesis and Self-Repair in Rabbits Fed an Antibiotic-Free Diet.

Simple SummaryIn recent years, China imposed a total ban on the use of antibiotics in animal husbandry. This caused huge economic losses, one of the main reasons being an increase in the incidence of diseases. In this study, rabbits were used as a model to study the pathogenesis of intestinal diseases in rabbits on an antibiotic-free diet, through non-targeted metabolomics methods. The results showed that 1969 different metabolites were identified. These differential metabolites were involved in five metabolic pathways associated with intestinal inflammation (tryptophan metabolism, pyrimidine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, lysine degradation, and bile secretion). In summary, the use of non-antibiotic feed might cause intestinal inflammation in rabbits and activate intestinal repair.The prohibition of the use of growth-promoting drug additives in feeds was implemented in China in 2020. However, rabbits can experience symptoms of intestinal disease, such as diarrhea and flatulence, when switching from standard normal diets with antibiotics to antibiotic-free diets. The molecular mechanisms related to the occurrence of these diseases as well as associated physiological and metabolic changes in the intestine are unclear. Thus, the objectives of this study were to study the pathogenesis of intestinal inflammation using untargeted metabolomics. This was done to identify differential metabolites between a group of antibiotic-free feed Hyplus rabbits (Dia) whose diet was abruptly changed from a standard normal diet with antibiotics to an antibiotic-free diet, and an antibiotic diet group Hyplus rabbits (Con) that was fed a standard normal diet with antibiotics. Morphological damage to the three intestinal tissues was determined through visual microscopic examination of intestinal Dia and Con tissue samples stained with hematoxylin and eosin (HE). A total of 1969 different metabolites were identified in the three intestinal tissues from Dia and Con rabbits. The level of 1280 metabolites was significantly higher and the level of 761 metabolites was significantly lower in the Dia than in the Con group. These differential metabolites were involved in five metabolic pathways associated with intestinal inflammation (tryptophan metabolism, pyrimidine metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, lysine degradation, and bile secretion). Rabbits in the Dia group developed metabolic disorders that affected the intestinal microbiota and changed the permeability of the intestinal tract, thereby triggering intestinal inflammation, affecting feed utilization, reducing production performance, and activating the intestinal tract self-repair mechanism. Thus, the abrupt transition from a diet with antibiotics to an antibiotic-free diet affected the structure and metabolism of the intestinal tract in Hyplus rabbits. Consequently, to avoid these problems, the antibiotic content in a rabbit diet should be changed gradually or alternative antibiotics should be found.

Profile of digestive organ and carcass yield of broiler chickens reared with free-antibiotics feed-in different elevation area in Banyumas regency, Indonesia

The research objective was to determine the digestive tract profile and carcass production of broiler chickens fed on antibiotic-free feed in areas with different elevation area. The study a survey designed according to the General Linear Model with purposive random sampling to choose farmer with 5.000-10.000 chickens Cobb strain, used opened house and free-antibiotic feed. The data was analyzed used univariate one-way analysis of variance. The result showed that the different elevation area have not significantly affected (p>0.05) the crop, proventriculus, duodenum weight and lenght, inter villi space, carcass weight, carcass percentage of broiler chickens fed by antibiotic-free feed. However, it has significantly affected (P

Antibiotics control in aquaculture requires more than antibiotic-free feeds: A tilapia farming case.

Public concern over the health implications of antimicrobials employed in aquaculture has resulted in adoption of strict regulations for their use. This study employed a high-throughput protocol covering 86 compounds in six pharmaceutical groups to screen feed and sediments from 20 tilapia ponds randomly in 18 farms of an aquacultural unit in southern China, one of important tilapia fillet suppliers in the world. Seventeen samples of commercial feeds from manufacturer-sealed bags in the farms were tetracyclines-free but not antibiotic-free. All the sealed-bag feeds contained quinolones and two feeds had sulfonamides (up to 140μgkg-1). Meanwhile, seven leftover-feeds in opened bags contained added antimicrobials: tetracyclines (570-2790μgkg-1) in all and florfenicol (20-294μgkg-1) in four. All the feeds regardless sealed or not had large amounts (221-2642μgkg-1) of salicylic acid (possible antimicrobial substitute) and caffeine, and one sealed-bag feed even was quantified with medroxyprogesterone. Surface sediments (0-10cm) from the ponds were detected with 36 compounds and sublayer sediments (10-20) with 8 compounds. Large amounts of salicylic acid were present in both surface and sublayer sediments accounting up to 10% of total pharmaceutical residues. Surface sediments were dominated by antibiotics (5.2-172μgkg-1), mainly sulfonamides and quinolones, contributing 68% of the total quantitative compound mass. Sublayer sediments were also enriched in quinolones (up to 260μgkg-1). Surprisingly, all sediments contained progesterone (up to 8.0μgkg-1) in coincidence to the feed with medroxyprogesterone, perhaps arising from endocrine abuses or cross-contamination. Although high levels of other pharmacologic residues (caffeine) in sediment posed greater than medium ecological risks, antibiotic residues contributed only 2-35% to the risk. These findings suggest that antibiotic-free feed may be insufficient to control antibiotic abuse in aquaculture and that additional regulatory actions may be necessary, such as veterinary prescription as human antibiotic uses.

Supplementing Oregano Essential Oil in a Reduced-Protein Diet Improves Growth Performance and Nutrient Digestibility by Modulating Intestinal Bacteria, Intestinal Morphology, and Antioxidative Capacity of Growing-Finishing Pigs.

Simple SummarySerious nitrogen pollution and shortage of protein feed resources have constrained the rapid development of the pig industry. Thus, the strategy of using a reduced-protein diet supplemented with amino acids in pig production has been widely accepted. Additionally, antibiotic growth promoters have been widely used in pig production for many years. However, their enormous and uncontrolled use has promoted bacterial resistance, leading to less effective treatment for animal diseases. Accordingly, this study investigated the effects of inclusion of oregano essential oil in a reduced-protein, amino acid-supplemented diet on growth performance, nutrient digestibility, gut health, and antioxidative capacity of growing-finishing pigs as an alternative to antibiotics. Our results suggested that adding oregano essential oil to a reduced-protein diet improved the growth performance and carcass lean percentage of pigs. In addition, long-term supplementation of oregano essential oil to a reduced-protein diet improved the intestinal bacteria, intestinal morphology, and antioxidative capacity of pigs. This study provides theoretical guidance for application of low-protein diet to guide the production of antibiotic-free feed for growing–finishing pigs.This study investigated the effects of supplementing oregano essential oil (OEO) to a reduced-protein diet on growth performance, nutrient digestibility, intestinal bacteria, intestinal morphology, and antioxidative capacity of growing-finishing pigs. Forty-eight barrows were randomly allotted to four treatments including normal-protein diet (NPD), reduced-protein, amino acid-supplemented diet (RPD), the same RPD supplemented with chlortetracycline (RPA), and RPD supplemented with OEO (RPO). The data showed that dietary OEO supplementation increased the average daily gain of pigs compared with NPD and RPD. The gain:feed in RPO- and NPD-fed pigs was higher than those in RPD- and RPA-fed pigs. Increased average daily feed intake and 10th-rib backfat thickness were detected in RPA-fed pigs. Pigs fed the RPO had higher apparent total tract digestibility (ATTD) of crude protein than those fed the other diets. The RPD and RPA treatments showed reduced counts of Lactobacillus spp. in ileal digesta of pigs. The RPA and RPO treatments also showed lower Escherichia coli counts in ileal digesta than the NPD and RPD treatments. Dietary OEO supplementation increased villous height of the jejunum and the ileal and plasma total antioxidative capacity of pigs. In conclusion, dietary OEO supplementation could improve the growth performance and nutrient digestibility of pigs by modulating intestinal bacteria, intestinal morphology, and antioxidative capacity.

Enhancing thermal stability of glucose oxidase by fusing amphiphilic short peptide

Glucose oxidase catalyzes the oxidation of β-D-glucose to gluconic acid and its derivatives, thus shows a great potential in the development of antibiotic-free feed. However, its production and processing still have the problem of poor thermal stability of enzyme activity. In this study, fusion of amphiphilic peptide technology was used to improve the stability of glucose oxidase. Herein, eight self-assembling peptides with different amino acid lengths and Linkers were fused to the N terminus of the glucose oxidase, yielding eight chimeric fusions SAP1-GS-GOD, SAP1-PT-GOD, SAP2-PT-GOD, SAP3-PT-GOD, SAP4-PT-GOD, SAP5-PT-GOD, SAP6-PT-GOD and SAP7-PT-GOD. Then, the 8 recombinant proteins were expressed in P. pastoris GS115. After separation and purification, the stability of glucose oxidase at 60 ℃was determined. The relative enzyme activities of the PT Linker-linked fusion enzyme incubated at 60 ℃ for 60 min were higher than those of the original enzyme, and the relative activity of SAP5-PT-GOD was 67% at 60 ℃ for 30 min, which was 10.9 times higher than that of the initial enzyme with the same treatment. Among them, the Kcat/Km value of SAP1-PT-GOD, SAP2-PT-GOD, SAP3-PT-GOD and SAP5-PT-GOD of the fusion enzyme was further improved than that of the initial enzyme. Through the analysis of the intramolecular force of the fusion enzyme, the increase of the thermal stability of the fusion enzyme is mainly due to the increase of the hydrogen bond. In summary, the study indicates that translational fusion of self-assembling peptides with PT Linker was able to augment the thermo-stability of glucose oxidase, which has certain potential in the production and application of glucose oxidase. The glucose oxidase with improved thermostability obtained in the above study and the related mechanism will play an important role in improving the activity of related enzymes in the proceeding of processing and application.

Study on establishing normal ranges of chosen biochemical parameters of haemolymph of Cornu aspersum maxima and Cepaea nemoralis gastropods.

The aim of the study was to establish normal ranges for chosen biochemical parameters of haemolymph of snails (Gasropoda: Mollusca), in the light of the use of these animals as experi- mental models in various types of studies. The study was conducted on 100 specimens of Cornu aspersum maxima (CAM) and 100 specimens of Cepaea nemoralis (CN). The haemolymph col- lected from the animals was analysed using colorimetry to assay aspartate transaminase (AST) activity, alanine transaminase (ALT) activity, amylase activity and the concentrations of urea and triglycerides. In the further part of the study, the influence of administering doxycycline with feed on the change of AST and ALT activity in snail haemolymph has been studied. The normal values established for CAM are as follow: AST activity: 26-38 u/l, ALT activity: 0-11 u/l, amylase activity 9-16 u/l, concentration of urea: 3-6 mg/dl, concentration of triglycerides: 16-20 mg/dl. For CN, the following data have been obtained: AST activity: 30-80 u/l, ALT activity: 0-15 u/l, amylase activity 12-15 u/l, concentration of urea: 5-8 mg/dl, concentration of triglycerides: 18-24 mg/dl. It has been shown that doxycycline presents a high workload on the hepatopancreas of snails, which is reflected by a statistically significant (p ⟨ 0.05) increase of AST and ALT activity in the haemolymph of the specimens which obtained doxycycline in feed, as compared to the groups with antibiotic-free feed. The haemolymph activity of both studied parameters increased together with study time and tetracycline administration time.

Effect of temperature (cooking and freezing) on the concentration of oxytetracycline residue in experimentally induced birds.

Aim:The objective of this study was to determine the effect of varying temperatures (different cooking methods and freezing) on the concentration of oxytetracycline (OTC) residues in tissues of broiler birds.Materials and Methods:Fifty, 5-week-old birds were purchased and acclimatized for 3 weeks while being fed antibiotic-free feed and water. Four birds were then tested for residue and in the absence; the remaining birds were injected intramuscularly with oxytetracycline at its therapeutic dose. Muscle and liver samples of the treated birds were harvested and checked for OTC residues before subjecting them to boiling, microwaving, and roasting. The three plate test was used for the residue detection.Result:OTC was detected at both pH 6.0 and pH 7.2 but not detected at pH 8.0. Roasting and boiling significantly reduced the concentration of oxytetracycline in muscle by 53.6% and 69.6%, respectively, at pH 6.0, microwaving reduced the concentration by 49.1% but was not statistically significant. The same pattern was followed at pH 7.2 with reduction of 34.3%, 53.2%, and 67.7% for microwaved, roasted, and boiled. For the liver tissues, there was a significant reduction in the concentration for both pH: 6.0 (57.75%, 79.75%, and 89%; pH 7.2 (48.06%, 79.6%, and 88.79%) for boiled, microwaved, and roasted samples. Boiling had a greater reduction effect for muscle samples while roasting had a greater reduction in liver samples at both pHs. Freezing at −10°C had no effect on the concentration of OTC even after 9 days.Conclusion:The significant reduction of OTC concentration by cooking indicates that consumers may not be at risk of the effects of OTC residues in meat, but microwaving meat may not reduce the concentration below the maximum residue limit if the initial concentration is very high. Therefore, routine monitoring of drug residues in farms and abattoirs is still advocated.

Response of Intestinal Microbiota to Antibiotic Growth Promoters in Chickens

Antibiotic growth promoters (AGPs) have been used as feed additives to improve average daily weight gain and feed efficiency in food animals for more than five decades. However, use of AGPs is associated with the emergence of antibiotic-resistant human pathogens of animal origin, posing a significant threat to food safety and public health. Thus, development of novel alternatives to AGPs is important to mitigate antimicrobial resistance in foodborne pathogens. To achieve this goal, the mode of action of AGPs should be elucidated. In this study, the response of the chicken gut microbiota to AGPs was examined using two culture-independent approaches: phospholipid fatty acid (PLFA) biomarker analysis and 16S rDNA clone library sequencing. PLFA analysis showed that AGP tylosin treatment changed composition of the microbiota in various intestinal sites; however, total viable bacterial biomass in intestine was not affected by tylosin treatment. PLFA analysis also revealed an abundant viable fungal population in chicken microbiota. Eight 16S rDNA libraries (96 clones per library) were constructed using ileal samples from chickens that received either antibiotic-free or medicated feed. The 16S rDNA clone analysis of the growth-relevant samples showed the AGP treatment influenced the diversity of ileum microbiota in the chickens primarily in the Firmicutes division. In particular, Lactobacillus spp. populations in the ileum of AGP-treated chickens were significantly lower than those from chickens receiving antibiotic-free feed. Together, this study revealed novel features of the intestinal microbiota in response to AGP treatment and suggested approach to develop potential alternatives to AGPs for mitigation of antimicrobial resistance in foodborne pathogens.

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Biological effects of bacitracin as a therapeutic agent and growth promoting compound

Bacitracin is a peptide antibiotic and it has several effects on the microbial population of the intestines that could account for its growth‐promoting ability. Enterotoxigenic E. coli is a major pathogen of weaned pigs and is responsible for significant death loss and retardation in weight gain. We found in in vitro studies that bacitracin at sub‐inhibitory concentrations (390 to 780 μg/ml) preferentially selected for the outgrowth of tetracycline sensitive bacteria from among a population of tetracycline resistant and tetracycline sensitive E. coli and Salmonella. Two E. coli strains were used and showed that bacitracin did select Tetracycline sensitive bacteria (P &lt; 0.05). Nine tetracycline resistant and nine tetracycline sensitive Salmonella strains were pooled in this study. Twenty‐five percent more tetracycline sensitive bacteria were found in LB broth containing bacitracin at the sub‐inhibitory concentration (P &lt; 0.01). These findings suggested that a possible benefit from using bacitracin as a feed additive might be to reduce the Tetrpopulation of pathogens in the intestinal tract. In studies utilizing newly weaned piglets, we established that a feed level concentration of bacitracin in the starter diet did enable piglets to clear a pathogenic bacterium at a faster rate than was the case when piglets were placed on antibiotic‐free feed.Supported by Alphamra Inc., the South Dakota Agricultural Experiment Station, and the South Dakota Center for Infectious Disease Research and Vaccinology

Escherichia coli O157:H7 Does Not Require Intimin To Persist in Pigs

<i>Escherichia coli</i> O157:H7 Does Not Require Intimin To Persist in Pigs

Inhibition of In Vitro Salmonella Typhimurium Colonization in Porcine Cecal Bacteria Continuous-Flow Competitive Exclusion Cultures

Continuous-flow (CF) chemostate cultures were used as models to determine the potential usefulness of undefined porcine cecal bacteria as competitive exclusion (CE) cultures against colonization by Salmonella Typhimurium. One culture, pCF1, was derived from cecal bacteria of an animal maintained on antibiotic-free feed, while the other culture, pCF4, was derived from cecal bacteria of an animal maintained on feed containing chlortetracycline. The effectiveness against a chlortetracycline-resistant Salmonella Typhimurium was examined in CF cultures maintained in the absence (pCF1 and pCF4) and presence (cpCF1 and cpCF4) of chlortetracycline. CF cultures were inoculated with each of 102, 104, and 106Salmonella Typhimurium CFU/ml. Chemostat inocula of 102Salmonella CFU/ml resulted in no Salmonella Typhimurium being detected at 2 and 3 days postinoculation in pCF1 and pCF4, respectively, and after 2 days in both cpCF1 and cpCF4. Inoculations of 104Salmonella Typhimurium CFU/ml resulted in clearance from pCF1 and pCF4 within 4 days and within 3 days from cpCF1 and cpCF4. Following inoculation with 106 CFU/ml, no Salmonella Typhimurium were detected in all CF cultures by 6 days postinoculation. The results indicated that in vitro CF cultures of porcine cecal bacteria were able to inhibit the growth of Salmonella Typhimurium. The ability to limit Salmonella Typhimurium growth was not restricted by prior exposure of the cecal bacteria to the feed additive chlortetracycline. The present study demonstrates the potential application of CF cultures as models to aid in the identification of CE cultures against salmonellosis in pigs.