Comparative pharmacokinetics of enrofloxacin in healthy and Aeromonas hydrophila‐infected crucian carp (Carassius auratus gibelio)

The comparative pharmacokinetics of enrofloxacin (ENR) and its metabolite ciprofloxacin (CIP) were investigated in healthy and Aeromonas hydrophila‐infected crucian carp after a single oral (p.o.) administration at a dose of 10 mg/kg at 25 °C. The plasma concentrations of ENR and of CIP were determined by HPLC. Pharmacokinetic parameters were calculated based on mean ENR concentrations by noncompartmental modeling. In healthy fish, the elimination half‐life (T_1/2λz), maximum plasma concentration (C_max), time to peak (T_max), and area under the concentration–time curve (AUC) values were 64.66 h, 3.55 μg/mL, 0.5 h, and 163.04 μg·h/mL, respectively. In infected carp, by contrast, the corresponding values were 73.70 h, 2.66 μg/mL, 0.75 h, and 137.43 μg·h/mL, and the absorption and elimination of ENR were slower following oral administration. Very low levels of CIP were detected, which indicates a low extent of deethylation of ENR in crucian carp.     

Pharmacokinetics and oral bioavailability of amoxicillin in chicken infected with caecal coccidiosis

Chicken infected with caecal coccidiosis (Eimeria tenella) was used to evaluate the effect of coccidiosis on the pharmacokinetic and bioavailability of amoxicillin. The level of amoxicillin was estimated by high‐performance chromatography (HPLC) to calculate the pharmacokinetic parameters and oral bioavailability. For i.v. injection of amoxicillin, Vd and CL were 0.29 and 0.27 (mg/kg)/(μg/mL)/h, respectively. Compared with healthy chicken, intravenous injection of amoxicillin in the infected chicken showed higher distribution and elimination constants, delayed clearance and statistically significant higher AUC and MRT. Oral administration in healthy chicken was accompanied by rapid absorption and high bioavailability with T_max, C_max and F about 1.03 h, 3.26 μg/mL and 40.2, respectively. Furthermore, oral administration in the infected chicken produced higher mean absorption time, delayed T_max, lower C_max, smaller AUC value and lower bioavailability (16.76). Based on these results, monitoring and adjustment of amoxicillin dosing could be practiced during the presence of coccidiosis. The measured C_max values suggest the administration of 1.3‐folds of the normal dose to maintain the normal maximal serum concentrations of amoxicillin in chicken infected with caecal coccidiosis.     

Pharmacokinetics of enrofloxacin and danofloxacin in premature calves

The aim of this study was to determine the pharmacokinetics/pharmacodynamics of enrofloxacin (ENR) and danofloxacin (DNX) following intravenous (IV) and intramuscular (IM) administrations in premature calves. The study was performed on twenty‐four calves that were determined to be premature by anamnesis and general clinical examination. Premature calves were randomly divided into four groups (six premature calves/group) according to a parallel pharmacokinetic (PK) design as follows: ENR‐IV (10 mg/kg, IV), ENR‐IM (10 mg/kg, IM), DNX‐IV (8 mg/kg, IV), and DNX‐IM (8 mg/kg, IM). Plasma samples were collected for the determination of tested drugs by high‐pressure liquid chromatography with UV detector and analyzed by noncompartmental methods. Mean PK parameters of ENR and DNX following IV administration were as follows: elimination half‐life (t_1/2λz) 11.16 and 17.47 hr, area under the plasma concentration–time curve (AUC_0‐48) 139.75 and 38.90 hr*µg/ml, and volume of distribution at steady‐state 1.06 and 4.45 L/kg, respectively. Total body clearance of ENR and DNX was 0.07 and 0.18 L hr^?1 kg^?1, respectively. The PK parameters of ENR and DNX following IM injection were t_1/2λz 21.10 and 28.41 hr, AUC_0‐48 164.34 and 48.32 hr*µg/ml, respectively. The bioavailability (F) of ENR and DNX was determined to be 118% and 124%, respectively. The mean AUC_0‐48CPR/AUC_0‐48ENR ratio was 0.20 and 0.16 after IV and IM administration, respectively, in premature calves. The results showed that ENR (10 mg/kg) and DNX (8 mg/kg) following IV and IM administration produced sufficient plasma concentration for AUC_0‐24/minimum inhibitory concentration (MIC) and maximum concentration (C_max)/MIC ratios for susceptible bacteria, with the MIC₉₀ of 0.5 and 0.03 μg/ml, respectively. These findings may be helpful in planning the dosage regimen for ENR and DNX, but there is a need for further study in naturally infected premature calves.     

Pharmacokinetic study of enrofloxacin in Nile tilapia (Oreochromis niloticus) after a single oral administration in medicated feed

The objective of this study was to evaluate the disposition kinetics of enrofloxacin (ENR) in the plasma and its distribution in the muscle tissue of Nile tilapia (Oreochromis niloticus) after a single oral dose of 10 mg/kg body weight via medicated feed. The fish were kept at a temperature between 28 and 30 °C. The collection period was between 30 min and 120 h after administration of the drug. The samples were analyzed by high‐performance liquid chromatography with a fluorescence detector (HPLC‐FLD). The ENR was slowly absorbed and eliminated from the plasma (C_max = 1.24 ± 0.37 μg/mL; T_max = 8 h; T_1/2Ke = 19.36 h). ENR was efficiently distributed in the muscle tissue and reached maximum values (2.17 ± 0.74 μg/g) after 8 h. Its metabolite, ciprofloxacin (CIP), was detected and quantified in the plasma (0.004 ± 0.005 μg/mL) and muscle (0.01 ± 0.011 μg/g) for up to 48 h. After oral administration, the mean concentration of ENR in the plasma was well above the minimum inhibitory concentrations (MIC₅₀) for most bacteria already isolated from fish except for Streptococcus spp. This way the dose used in this study allowed for concentrations in the blood to treat the diseases of tilapia.     

Pharmacokinetics of enrofloxacin after oral,intramuscular and bath administration in crucian carp (Carassius auratus gibelio)

The pharmacokinetics of enrofloxacin (ENR) was studied in crucian carp (Carassius auratus gibelio) after single administration by intramuscular (IM) injection and oral gavage (PO) at a dose of 10 mg/kg body weight and by 5 mg/L bath for 5 hr at 25°C. The plasma concentrations of ENR and ciprofloxacin (CIP) were determined by HPLC. Pharmacokinetic parameters were calculated based on mean ENR or CIP concentrations using WinNonlin 6.1 software. After IM, PO and bath administration, the maximum plasma concentration (C_max) of 2.29, 3.24 and 0.36 μg/ml was obtained at 4.08, 0.68 and 0 hr, respectively; the elimination half‐life (T_1/2β) was 80.95, 62.17 and 61.15 hr, respectively; the area under the concentration–time curve (AUC) values were 223.46, 162.72 and 14.91 μg hr/ml, respectively. CIP, an active metabolite of enrofloxacin, was detected and measured after all methods of drug administration except bath. It is possible and practical to obtain therapeutic blood concentrations of enrofloxacin in the crucian carp using IM, PO and bath immersion administration.     

Body weight,meat quality and blood metabolite responses to carbohydrate administration in the drinking water during pre‐slaughter feed withdrawal in broilers

This study was conducted to determine weights of body (BW), carcass (CW), gastrointestinal tract (GTW), meat quality and some blood metabolite responses to corn starch, saccharose or glucose administration in the drinking water during pre‐slaughter feed withdrawal (FW) in broilers. On day 42 of age, 200 broilers (Ross 308) were allocated randomly to five treatments with four replicates. During a 10‐h FW, control broilers (C) were provided with non‐treated water and the standard finisher diet ad libitum, whereas fasted broilers provided with non‐treated (NFW) or treated water, 3 g glucose (G), saccharose (S) or corn starch (CS)/L. Eight birds (four males and four females) per treatment were slaughtered. Birds receiving non‐treated or treated water had lower BW and higher carcass yield than the full‐fed broilers. The full‐fed broilers had higher absolute and relative GTW than the fasted birds. Broilers consumed more readily treated water compared with non‐treated water. While the a* value of breast meat from CS birds was higher than that from NFW, the b* value of that was higher than S and C birds. The c* values of breast meat from S birds were lower compared with that from the CS treatment. The thigh meat from NFW broilers had higher h* value than that from C and G broilers. The thigh meats of C and CS broilers had higher c* value than that of G birds. The full‐fed broilers had higher plasma triglyceride concentration than NFW, S and G birds. The full‐fed broilers had higher plasma uric acid and uric acid nitrogen concentrations than S birds. These results show that carbohydrate administration in the drinking water cannot be a good alternative for the FW period before slaughter due to the fact that the carbohydrates do not reduce BW losses and do not lead to increases in meat quality.     

Inclusion of Bacillus amyloliquefaciens strain TOA5001 in the diet of broilers suppresses the symptoms of coccidiosis by modulating intestinal microbiota

Coccidiosis is an intestinal parasitic infection and one of the most prevalent and economically damaging diseases of chickens. Furthermore, coccidia‐induced mucogenesis promotes secondary colonization by Clostridium perfringens, a major pathogen of chickens that causes necrotic enteritis. Our previous work found that supernatant of a culture of Bacillus amyloliquefaciens strain TOA5001 (BA) inhibited the growth of C. perfringens on Gifu anaerobic broth medium. Accordingly, we evaluated the effectiveness of dietary BA administration in inhibiting C. perfringens colonization of the intestine in broilers that were experimentally infected with coccidia. Ten healthy broilers from a BA‐supplemented (2 × 10⁵ colony‐forming units/g of feed) broiler group and 10 from a non‐treated group were challenged with Eimeria tenella and E. maxima (5000 oocysts of each species/chick) at 28 days old. At 36 days old, five chicks from each group were slaughtered, whereas the remaining five in each group were killed at 49 days old. Dietary BA administration into Eimeria‐challenged birds reduced coccidial symptoms such as intestinal lesions. It also modified the cecal microbiota through suppressing C. perfringens and E. coli colonization, and inducing domination of Faecalibacterium prausnitzii, the Lactobacillus group and unknown Lachnospiraceae genera by bacterial DNA‐based metagenome analyses. B. amyloliquefaciens TOA5001 supplementation suppressed the symptoms of coccidiosis by modulating cecal microbiota in Eimeria‐challenged broilers.     

Population pharmacokinetics for danofloxacin in the intestinal contents of healthy and infected chickens

Avian pathogenic Escherichia coli could cause localized and systemic infection in the poultry, and danofloxacin is usually used to treat avian colibacillosis through oral administration. To promote prudent use of danofloxacin and reduce the emergence of drug‐resistant E. coli strains, it is necessary to understand the population pharmacokinetics (PopPK) of danofloxacin in chicken intestines. In this study, reversed‐phase high performance liquid chromatography (HPLC) with fluorescence detection was used to detect the concentrations of danofloxacin in the contents of duodenum, jejunum, and ileum of the healthy and infected chickens after single oral administration (5 mg/kg body weight). Then, the PopPK of danofloxacin in intestines were analyzed using NONMEM software. As a result, a two‐compartment PK model best described the time‐concentration profile of duodenal, jejunal, and ileal contents. Interestingly, absorption rate (K_a), distribution volume (V), and clearance (CL) for danofloxacin from duodenal, jejunal to ileal contents were sequentially decreased in the healthy chickens. However, the trend of K_a, V, and CL of danofloxacin was changed dramatically in the intestine of infected chickens. K_a and V of danofloxacin in the jejunum were higher than in the ileum and duodenum. Compared with healthy chickens, K_a and V of danofloxacin in the duodenum decreased significantly, while increased in jejunum, respectively. It has been noted that K_a decreased and V increased in the ileum of infected chickens. Besides, CL in the duodenum, jejunum, and ileum of infected chickens was, respectively, lower than those of healthy chickens. Interestingly, the relative bioavailability (F) of danofloxacin in the ileum was relatively higher in both healthy and infected chickens. In addition, F in the duodenal, jejunal, and ileal contents of infected chickens was respectively higher than healthy chickens. In summary, the PopPK for danofloxacin in infected chicken intestines was quite different from healthy chickens. The absorption, distribution, and clearance of danofloxacin in healthy chickens decreased from duodenum to jejunum and to ileum. Moreover, the pharmacokinetic characteristics in the intestine of infected chickens changed significantly, and the pharmacokinetic characteristics in the ileum can be used as a representative of all intestinal segments.     

Pharmacokinetics of enrofloxacin and its metabolite ciprofloxacin in freshwater crocodiles (Crocodylus siamensis) after intravenous and intramuscular administration

To the best of the authors’ knowledge, pharmacokinetic information to establish suitable therapeutic plans for freshwater crocodiles is limited. Therefore, the purpose of this study was to clarify the pharmacokinetic characteristics of enrofloxacin (ENR) in freshwater crocodiles, Crocodylus siamensis, following single intravenous and intramuscular administration at a dosage of 5 mg/kg body weight (b.w.). Blood samples were collected at assigned times up to 168 hr. The plasma concentrations of ENR and its metabolite ciprofloxacin (CIP) were measured by liquid chromatography tandem–mass spectrometry. The concentrations of ENR and CIP in the plasma were quantified up to 144 hr after both the administrations. The half-life was long (43–44 hr) and similar after both administrations. The absolute i.m. bioavailability was 82.65% and the binding percentage of ENR to plasma protein ranged from 9% to 18% with an average of 10.6%. Percentage of CIP (plasma concentrations) was 15.9% and 19.9% after i.v. and i.m. administration, respectively. Based on the pharmacokinetic data, susceptibility break point and PK-PD indexes, i.m. single administration of ENR at a dosage of 5 mg/kg b.w. might be appropriate for treatment of susceptible bacteria (MIC > 1 μg/mL) in freshwater crocodiles, C. siamensis.     

Pharmacokinetics studies of enrofloxacin injectable in situ forming gel in dogs

The objective of this study was to evaluate the pharmacokinetic characteristics of enrofloxacin (ENR) injectable in situ gel we developed in dogs following a single intramuscular (i.m.) administration. Twelve healthy dogs were randomly divided into two groups (six dogs per group), then administrated a single 20 mg/kg body weight (b.w.) ENR injectable in situ gel and a single 5 mg/kg b.w. ENR conventional injection, respectively. High‐performance liquid chromatography (HPLC) was used to determine ENR plasma concentrations. The pharmacokinetic parameters of ENR injectable in situ gel and conventional injection in dogs are as follows: MRT (mean residence time) (45.59 ± 14.05) h verse (11.40 ± 1.64) h, AUC (area under the blood concentration vs. time curve) (28.66 ± 15.41) μg·h/mL verse (11.06 ± 3.90) μg·h/mL, c_max (maximal concentration) (1.59 ± 0.35) μg/mL verse (1.46 ± 0.07) μg/mL, t_max (time needed to reach c_max) (1.25 ± 1.37) h verse (1.40 ± 0.55) h, t_1/2λz (terminal elimination half‐life) (40.27 ± 17.79) h verse (10.32 ± 0.97) h. The results demonstrated that the in situ forming gel system could increase dosing interval of ENR and thus reduced dosing frequency during long‐term treatment. Therefore, the ENR injectable in situ gel seems to be worth popularizing in veterinary clinical application.     

Study on differentiation during embryonic development across selective and ancestral breeds

In order to explore the effect of strain on diverging post‐hatch muscle properties, muscle regulation during embryo development was investigated in selected and unselected breeds. Four broiler strains were used: JingNing (JN) chicken (a Chinese native chicken), HuangYu (HY) broiler, BaiYu (BY) broiler and Hyline layer (commercial crossbred chickens). Results showed that the four breeds had almost the same characteristic during different incubation periods. BY broilers moved more than JN and Hyline layers from Hamburger & Hamilton stage (HH)24 to HH31 (P < 0.05). HY broilers moved more than JN and Hyline layers from HH27 to HH31 (P < 0.01). All the embryos were heavier daily from HH24 to ED18 (P < 0.05); broilers presented greater body weights than JN and hyline layers (P > 0.05); broilers presented smaller fiber diameter than JN chickens before HH31 (P > 0.05). From then on, JN chicken exhibited smaller fiber diameter compared to the broilers (P > 0.05). Western blotting indicated all the breeds had continuous insulin‐like growth factor‐I (IGF‐I) expression, with the highest expression level in broilers from HH19 to HH24 and highest expression level in JN chicks from HH27 to HH31. The results indicated that the diverging growth among breeds was already shown in embryonic stages; the different expression patterns of IGF‐I may be involved in cell proliferation and differentiation.     

恩诺沙星在健康及巴氏杆菌感染鸡体内的药物代谢动力学研究

健康及巴氏杆菌感染鸡 (10CFUC4 8- 1多杀性巴氏杆菌 /只鸡 ,im)按 5mg/kg恩诺沙星单次im后 ,采用反相高效液相色谱法检测用药后不同时间点的血浆药物浓度。结果表明 ,恩诺沙星在健康及巴氏杆菌感染鸡体内的消除均符合二室开放模型。巴氏杆菌感染可显著加速鸡体内恩诺沙星的消除 ,推测可能与感染鸡体内巴氏杆菌裂解后产生的内毒素有关。内毒素可刺激骨髓产生大量白细胞 ,而恩诺沙星又恰恰能在吞噬细胞中富集 ,且在富集后可迅速向周围炎性组织中释放 ,因此导致血中药物浓度下降。提示在应用恩诺沙星预防、治疗细菌性疾病时 ,利用其在健康鸡体内的药物动力学参数指导临床用药 ,有时是不适宜的。     

Oral administration of L-citrulline changes the concentrations of plasma hormones and biochemical profile in heat-exposed broilers

We examined the effects of oral administration of L-citrulline (L-Cit) on plasma metabolic hormones and biochemical profile in broilers. Food intake, water intake, and body temperature were also analyzed. After dual oral administration (20 mmol/head/administration) of L-Cit, broilers were exposed to a high ambient temperature (HT; 30 ± 1°C) chamber for 120 min. Oral administration of L-Cit reduced (p < .001) rectal temperature in broilers. Food intake was increased (p < .05) by heat stress, but it was reduced (p < .05) by L-Cit. Plasma levels of 3,5,3′-triiodothyronine, which initially increased (p < .0001) due to heat stress, were reduced (p < .01) by oral administration of L-Cit. Plasma insulin levels were increased by heat exposure (p < .01) and oral L-Cit (p < .05). Heat stress caused a decline (p < .05) in plasma thyroxine. Plasma lactic acid (p < .05) and non-esterified fatty acids (p < .01) were increased in L-Cit-treated heat-exposed broilers. In conclusion, our results suggest that oral L-Cit can modulate plasma concentrations of major metabolic hormones and reduces food intake in broilers.     

Comparative pharmacokinetics and bioavailability of tylosin tartrate and tylosin phosphate after a single oral and i.v. administration in chickens

The pharmacokinetics and oral bioavailability of tylosin tartrate and tylosin phosphate were carried out in broiler chickens according to a principle of single dose, random, parallel design. The two formulations of tylosin were given orally and intravenously at a dose level of 10 mg/kg b.w to chicken after an overnight fasting (n = 10 chickens/group). Serial blood samples were collected at different time points up to 24 h postdrug administration. A high performance liquid chromatography method was used for the determination of tylosin concentrations in chicken plasma. The tylosin plasma concentration's time plot of each chicken was analyzed by the 3P97 software. The pharmacokinetics of tylosin was best described by a one‐compartmental open model 1st absorption after oral administration. After intravenous administration the pharmacokinetics of tylosin was best described by a two‐compartmental open model, and there were no significant differences between tylosin tartrate and tylosin phosphate. After oral administration, there were significant differences in the C_max (0.18 ± 0.01, 0.44 ± 0.09) and AUC (0.82 ± 0.05, 1.57 ± 0.25)between tylosin phosphate and tylosin tartrate. The calculated oral bioavailability (F) of tylosin tartrate and tylosin phosphate were 25.78% and 13.73%, respectively. Above all, we can reasonably conclude that, the absorption of tylosin tartrate is better than tylosin phosphate after oral administration.     

肌注硫酸庆大霉素在大肠杆菌感染鸡体内的药动学试验

为分析硫酸庆大霉素在健康和鸡大肠杆菌感染鸡体内的药物动力学特征,试验通过给健康鸡腹腔注射大肠杆菌O157,以临床症状、病理剖检和微生物检查为指标,成功建立鸡大肠杆菌感染模型。选取健康鸡和患病鸡各8只,分别以20 mg/kg体重单剂量肌内注射硫酸庆大霉素,分别于0.167、0.25、0.5、0.75、1、2、3、4、6、8和12 h时间点采血,采用管碟法测定血浆中庆大霉素的浓度。结果显示:试验所建立的标准曲线相关性好,相关系数均达0.990以上,日内、日间变异系数均小于10%。肌注给药后,硫酸庆大霉素在鸡体内吸收迅速,房室模型分析表明,健康鸡与患病鸡药时数据均符合有二室开放模型,硫酸庆大霉素在健康鸡体内峰浓度(Cmax)为(15.01±3.51)μg/mL,药时曲线下面积(AUC)为(100.79±5.14)μg/mL·h,消除半衰期(t1/2β)为(4.41±1.32)h,达峰时间(Tp)为(1.27±0.50)h。硫酸庆大霉素在患病鸡体内峰浓度(Cmax)为(12.50±2.19)μg/mL,药时曲线下面积(AUC)为(83.38±4.19)μg/mL·h,消除半衰期(t1/2β)为(4.18±1.17)h,达峰时间(Tp)为(0.97±0.05)h。结果表明:硫酸庆大霉素在患病鸡体内的峰浓度和药时曲线下面积低于健康鸡(P<0.05),因此对于已感染大肠杆菌的病鸡可以考虑适当增加给药剂量。     

The influence of Actinobacillus pleuropneumoniae infection on tulathromycin pharmacokinetics and lung tissue disposition in pigs

A tulathromycin concentration and pharmacokinetic parameters in plasma and lung tissue from healthy pigs and Actinobacillus pleuropneumoniae (App)‐infected pigs were compared. Tulathromycin was administered intramuscularly (i.m.) to all pigs at a single dose of 2.5 mg/kg. Blood and lung tissue samples were collected during 33 days postdrug application. Tulathromycin concentration in plasma and lung was determined by high‐performance liquid chromatography with tandem mass spectrometry (LC‐MS/MS) method. The mean maximum plasma concentration (C_max) in healthy pigs was 586 ± 71 ng/mL, reached by 0.5 h, while the mean value for C_max of tulathromycin in infected pigs was 386 ± 97 ng/mL after 0.5 h. The mean maximum tulathromycin concentration in lung of healthy group was calculated as 3412 ± 748 ng/g, detected at 12 h, while in pigs with App, the highest concentration in lung was 3337 ± 937 ng/g, determined at 48 h postdosing. The higher plasma and lung concentrations in pigs with no pulmonary inflammation were observed at the first time points sampling after tulathromycin administration, but slower elimination with elimination half‐life t_1/2el = 126 h in plasma and t_1/2el = 165 h in lung, as well as longer drug persistent in infected pigs, was found.     

Effect of three polyether ionophores on pharmacokinetics of florfenicol in male broilers

Drug–drug interactions (DDIs) may adversely affect the prevention and cure of diseases. The effects of three polyether ionophore antibiotics, salinomycin (SAL), monensin (MON), and maduramycin (MAD) on the pharmacokinetics of florfenicol (FFC) were investigated in broilers. The chickens were fed rations with or without SAL (60 mg/kg feeds), MON (120 mg/kg feeds), or MAD (5 mg/kg feeds) for 14 consecutive days. FFC was given to the chickens either intravenously (i.v.) or orally (p.o.) at a single dose of 30 mg/kg body weight. Blood samples were taken from each chicken at 0–24 h postadministration of FFC. The plasma concentration of FFC was detected by high‐performance liquid chromatography. The plasma concentration of FFC decreased with i.v. or p.o. co‐administration of SAL, MON, or MAD in broilers, implying occurrence of DDIs during the co‐administration of FFC with these ionophores. Our findings suggest that more attention should be given to the use of FFC to treat bacterial infections in chickens supplemented with polyether ionophore antibiotics.     

Pharmacokinetics and relative bioavailability of tiamulin in broiler chicken as influenced by different routes of administration

The bioavailability and pharmacokinetic disposition of tiamulin in broiler chicken were investigated after administration through the crop, drinking water, and feed at 40 mg/kg body weight. Residues of tiamulin in tissues of broiler chicken were also assessed. Plasma and tissue concentrations of tiamulin were analyzed by reverse‐phase high‐performance liquid chromatography (HPLC) method. Plasma concentration–time data were described by the non‐compartmental model for all three routes, and pharmacokinetic parameters were calculated. There were no significant differences (p > 0.05) in pharmacokinetic parameters and mean plasma concentrations of tiamulin between three routes tested (crop, water, and feed), indicating equal efficacy. Tiamulin residues in edible tissues (muscles, skin, and fat) were lower than the advocated maximum residue limit (MRL of 0.1 µg/g and that of liver was 1 µg/g) on the 3rd day. No traces were found on the 5th day after drug administration. This indicated that the withdrawal period (less than 5 days) is very short, which makes it safer. This study shows that tiamulin can be used with equal efficacy through all routes of administration in broiler chicken (crop, water, and feed).     

Effects of oral administration of different dosages of carvacrol essential oils on intestinal barrier function in broilers

Essential oils are widely used in the pharmaceutical, food and cosmetic industries, and many plant essential oils have shown that they have positive effects on broilers nutrition. This experiment was conducted to study the effects of orally administered different dosages of carvacrol essential oils on intestinal barrier function in broiler chickens. A total of eighty 28‐day‐old (1.28 ± 0.15 kg) ROSS 308 broilers were randomly allocated to four groups of 20 replicates each, with one chicken per replicate per cage, and all were fed with the same diet. Four experimental groups were orally administered 0, 200, 300 or 400 μl carvacrol essential oils at 18:00 hr every day during the 2‐week experimental period. As a result of which, the gene expression of the occludin, claudin‐1, claudin‐5, ZO‐1 and ZO‐2 in intestinal mucosa of small intestine (p < 0.05) and the goblet cell content in small intestine epithelium (p < 0.05) were significantly increased; test subjects with 300 or 400 μl carvacrol essential oils reduced the microbial counts of Salmonella spp. and Escherichia coli in the intestines (p < 0.05); Essential oils administration also significantly increased activity of the sucrase (p < 0.05) and lactase (p < 0.05) in intestinal mucosa. In conclusion, the carvacrol essential oils have positive effects on growth performance and intestinal barriers function of broilers; those effects may be related to the dosage, as administration of 300 or 400 μl was more effective than that of 200 μl.     

Distribution of ceftiofur into Mannheimia haemolytica‐infected tissue chambers and lung after subcutaneous administration of ceftiofur crystalline free acid sterile suspension

Washburn, K., Johnson, R., Clarke, C, Anderson, K. Distribution of ceftiofur into Mannheimia haemolytica‐infected tissue chambers and lung after subcutaneous administration of ceftiofur crystalline free acid sterile suspension. J. vet. Pharmacol. Therap. 33 , 141–146. The objective of this study was to evaluate the penetration of ceftiofur‐ and desfuroylceftiofur‐related metabolites (DCA) into sterile and infected tissue chambers, lung tissue and disposition of DCA in plasma across four different sacrifice days postdosing. Twelve healthy calves were utilized following implantation with tissue chambers in the paralumbar fossa. Tissue chambers in each calf were randomly inoculated with either Mannheimia haemolytica or sterile PBS. All calves were dosed with ceftiofur crystalline free acid sterile suspension (CCFA‐SS) subcutaneously in the ear pinna. Calves were randomly assigned to 4 groups of 3 to be sacrificed on days 3, 5, 7 and 9 postdosing. Prior to euthanasia, plasma and tissue chamber fluid were collected, and immediately following euthanasia, lung tissue samples were obtained from four different anatomical sites DCA concentration analysis. Results of our study found that, in general, DCA concentrations followed a rank order of plasma > infected tissue chamber fluid > noninfected tissue chamber fluid > lung tissue. Data also indicated DCA concentrations remained above the therapeutic threshold of 0.2 μg/mL for plasma and chamber fluid and 0.2 μg/g for lung tissue for at least 7 days post‐treatment.