Effect of chilling temperature on the long-term survival of rabbit spermatozoa held either in a tris-based or a jellified extender

As the preservation of the fertilizing capacity of rabbit spermatozoa for several days after semen collection remains a major target for the artificial insemination programs of rabbit breeding, a study was conducted to compare the efficacy of 5 or 15°C as holding temperature in lengthening the preservability of rabbit semen quality during 192 h of storage both in a solid (Cunigel) and a liquid (Tris-Citric acid-Glucose; TCG) extender. Six pooled semen samples (two ejaculates/male; two-three males/pool) were taken and made four aliquots: two aliquots were tenfold diluted with the TCG extender, whereas the other two were tenfold diluted with the Cunigel extender. One aliquot per diluent was stored at 5°C and the second one at 15°C. Sperm motility (light microscope), viability (SyBr-PI staining), plasma membrane functional integrity (Hypo-osmotic swelling test) and acrosome integrity (PSA-FITC staining) were recorded at 0, 48, 120 and 192 h of storage. In liquid-stored spermatozoa, mass motility and viability were significantly higher (p ≤ 0.05) in samples stored at 5°C than at 15°C at all the storage times; at 5°C resulted also higher (p ≤ 0.05) the percentages of both forward motility at 48 h and sperm functional integrity at 120 and 192 h of storage, whereas chilling temperature did not affect acrosome integrity. With the Cunigel extender, all the semen qualitative parameters were significantly higher in sample stored at 5 than 15°C over storage time (p ≤ 0.05); only acrosome integrity at 192 h was not different according to the chilling temperatures. In conclusion, 5°C were better than 15°C for the long-term storage of rabbit semen both in the TCG and Cunigel extender.     

磺胺二甲嘧啶在麻黄鸡组织中残留消除规律研究

用添加临床剂量100 mg/kg磺胺二甲嘧啶的饲料喂养40日龄麻黄鸡,连续用药3 d,分别在停药0、12、24、48、72、96、120、144、192、240、360、480、600 h时间点对肌肉、肝和肾组织采样,检测磺胺二甲嘧啶残留浓度。停药25 d后,肌肉组织残留量为0.054 mg/kg,肝和肾组织未检出磺胺二甲嘧啶,结果表明磺胺二甲嘧啶在麻黄鸡组织中停药期为25 d,《中国兽药典》2005年版中规定磺胺二甲嘧啶10 d的停药期是不尽合理的。     

鸡胚骨骼肌细胞增殖和融合培养模型的建立

本实验建立了鸡胚骨骼肌细胞增殖和融合培养模型,增殖和融合培养液分别为添加5％胎牛血清(FCS)和添加10％FCS+0．5％鸡胚浸出液的DMEM培养液。结果表明:培养的骨骼肌细胞增殖和融合情况良好,可存活1周以上。胰岛素(INS,10-1 000 ng/mL)处理48 h显著促进骨骼肌细胞增殖,而100-1000 ng/mL INS处理96 h可显著促进骨骼肌细胞融合。该模型可用来研究激素、生长因子或营养物质对骨骼肌细胞增殖和分化的影响。     

日粮钙水平对产蛋鸡吸收~(65)Zn的影响

将放射性65Zn盐酸盐注入经高钙日粮(基础日粮添加6.7％钙)饲喂4个月的产蛋鸡嗉囊内,分别在24 h、48 h、96 h和192 h的实验终点累积计算粪尿排泄物中65Zn的放射性剂量.结果表明,日粮中钙水平的提高可使65Zn的吸收减少,排除增加.因此认为,日粮中的高钙因素对锌在鸡体内的吸收具有阻碍作用.     

Culture system and long-term storage of culture media in the in vitro production of bovine embryos

The optimum culture system for in vitro matured and fertilised oocytes still remains to be clarified. Culture media (CM) for mammalian embryos are routinely prepared fresh for use and preserved under refrigeration during one or two weeks. The purposes of this work were (1) to compare the efficiency of a synthetic oviduct fluid (SOF) with two different bovine serum albumin (BSA) concentrations (3 and 8 g/L) for the in vitro production of bovine blastocysts, (2) to test the effect of timing on adding fetal calf serum (FCS) to the SOF, and (3) to evaluate the effects on bovine embryo development of freezing and lyophilisation as procedures for preserving the SOF. Supplementation of SOF with 3 g/L BSA increased Day-7 blastocyst expansion rates (18.3 ± 1.6 vs. 14.4 ± 0.7; P < 0.05), although no differences in hatching rates were found. Addition of FCS to SOFaa (SOF with amino acids) medium supplemented with sodium citrate (SOFaaci) at 48 and at 72 h post-insemination (PI) allowed obtaining higher Day-6 embryo development rates than when FCS was added at 18 or 96 h PI (Day-6 morulae + blastocyst rate: 30.0 ± 1.1, 40.8 ± 1.1, 43.9 ± 2.3 and 39.3 ± 0.5 for FCS addition at 18, 48, 72 and 96 h, respectively). Hatching rates were significantly improved when serum was added at 72 h PI. Finally, both refrigeration and lyophilisation appeared as useful cryopreservation procedures for SOFaaci, although a significant loss of its ability to support embryo development, compared to the control fresh culture medium, was observed.     

Measurement of protein turnover in skeletal muscle strips

Isolated porcine and bovine muscle strips were incubated in Krebs Ringer bicarbonate buffer to determine in vitro protein synthesis (PS) and protein degradation (PD) rates to validate the in vitro system for use with livestock species. The addition of 5X plasma concentrations of amino acids to the medium stimulated PS 30%. Addition of 3.5 mM leucine to a leucine-deficient buffer supplemented with amino acids decreased PD 37% and stimulated PS 24%. The addition of .1 U/ml insulin reduced PD 28% and increased PS 30%. Protein degradation was elevated in longitudinally split rat soleus and extensor digitorum longus muscles compared to their contralateral intact muscles. Muscle strips must be removed within 15 min of exsanguination because PD rates become greatly elevated thereafter. ATP concentrations declined during incubation, but the addition of ATP or creatine had no effect on either PD or PS. Neither PD nor PS was affected by the addition of transferrin, fetuin, ascorbate, dexamethasone or indomethacin to the incubation medium. However, muscle strips were sensitive to the addition of triiodothyronine (T3), PD was increased up to 75% as T3 concentration was increased, and PS rates doubled compared to controls. Serum from mature barrows or gilts had no effect on protein turnover, but the addition of 10% and 15% serum from boars increased both PD and PS. With fasted pigs a continual decline in PS occurred over 5 d, whereas PD was elevated at 3 d and then declined to rates comparable to the fed state after 5 d. These data suggest that the in vitro system has application for assessing relative changes that occur in vivo following nutritional, physiological and endocrinological manipulation.     

Stage-specific effect of growth hormone on developmental competence of bovine embryos produced in-vitro

Many efforts have been made to develop effective culture conditions for the production of bovine blastocysts. Growth hormone (GH) and glucose are known to affect in vitro embryo development. To improve in vitro culture conditions, the culture medium containing fetal calf serum (FCS) or bovine serum albumin (BSA) was supplemented with GH at various periods of development, and the effects of GH on the rate of development and the quality of the blastocysts were studied. Then, starting at the morula stage, the effect of glucose and GH on the rate of development was studied. In all experimental periods, FCS was more effective than BSA at improving the development rate and increasing the cell number of blastocysts. Adding GH to the culture medium between 18 and 48 h after fertilization (1-8 cell stage embryo) did not affect either the rate of blastulation or the cell number regardless of the serum protein (FCS or BSA). From 48 to 120 h after fertilization (5-cell to morula stage) GH increased the cell number of the blastocysts in the presence of BSA, but not in the presence of FCS. From 120 to 192 h after fertilization (morula to blastocyst stage), GH improved the developmental rate and cell number in the presence of FCS, although there was no significant difference when BSA was used instead of FCS as the serum protein. When cows were implanted with blastocysts developed in the presence of GH from the morula stage, their pregnancy rate did not differ from that of the control. Increasing the glucose concentration in the medium from 1.5 mM to 3 mM starting at the morula stage (120 h after fertilization) slightly decreased the rate of development, but on the other hand, decreasing the glucose concentration to 0 mM did not affect either the rate of development or the cell number. Also, then GH had no effect on the developmental rate or the cell number in the absence of glucose. In conclusion, when the medium was supplemented with serum, GH improved embryo development from the morula stage, but an increased concentration of glucose decreased embryo development. Furthermore, GH did not improve the pregnancy rate of blastocysts developed in vitro.     

Pharmacokinetics of caffeine in the oestrogen-implanted ovariectomized ewe

The disposition kinetics of caffeine and its metabolites theophylline, theobro-mine and paraxanthine in the oestrogen-implanted ovariectomized ewe following single intravenous doses of 5, 10, 15 or 20 mg/kg caffeine are described in this paper. Blood was collected at 5, 30 and 60 min, and at 3, 6, 8, 12, 24, 48, 72, 96, 120, 144, 192 and 240 h after dosing. Caffeine concentrations peaked within 30 min of administration but remained in a plateau phase for 3-6 h before declining over a prolonged period of time. For caffeine the mean elimination half-life was calculated to be 47 h. Detectable caffeine concentrations remained for 10 days after administration in all groups. The area under the plasma concentration-time curve ( AUC ) values were used to compare tissue caffeine exposure and were, approximately, linearly related to dose. Metabolite concentrations were maintained at peak and near peak concentrations for 6-24 h after caffeine administration followed by prolonged elimination. Because of significant species differences in drug elimination rates, it is concluded that the ewe is not a suitable animal model in the clinical context. However, the sheep may well provide insights into caffeine's mechanism of action of relevance to veterinary drug research.     

Post mortem muscle metabolism and meat quality in three genetic types of turkey

1. A standard (FG, fast-growing), a black local or 'label', type (SG, slow-growing) turkey line, and the crossbreed between these two lines were compared for muscle post-mortem metabolism and related meat quality traits. 2. Ninety male turkeys (30 of each genetic type) were raised under the same experimental conditions until slaughter at 16 weeks of age. 3. Live weights at 16 weeks of age differed significantly (7.8, 6.0 and 4.2 kg, for the FG, crossbred and SG lines, respectively). Collagen content of Pectoralis superficialis (PS) muscle was higher in SG birds than in the other two types. 4. The rate of post-mortem glycogen depletion and lactate accumulation in PS and Ilio tibialis (IT) muscles were similar in the 3 lines, as were the rate and extent of post-mortem pH fall in PS muscle. In IT muscle, however, SG birds showed a slight but significantly faster pH decline. 5. Colour measurements indicated a paler breast muscle and a higher degree of myoglobin oxidation in SG birds at 24 h post mortem, than in both other lines. But these differences had disappeared after 4 and 7 d post mortem 6. SG birds showed higher drip loss and instrumentally-assessed toughness in breast muscle, compared with crossbred and FG birds. FG birds, however, had the lowest yield of breast meat after curing-cooking. 7. No marked differences in post-mortem metabolism were found between the three lines. However, differences in water-holding capacity of fresh and cured-cooked meat suggest that factors other than the rate and extent of post-mortem pH fall may contribute to the respective characteristics of these lines.     

DVH引发雏鸭血清及肝脏中NOS活性变化的研究

用鸭肝炎病毒人工感染雏鸭,于感染后3、12、36、48、72、96、144、168h和192h剖杀感染组和对照组雏鸭各5只,测定其血清和肝脏中一氧化氮合酶(NOS)的活性。结果表明,雏鸭感染鸭肝炎病毒后,血清和肝脏中NOS的活性升高,在感染48h时显著高于对照组,表明鸭肝炎病毒导致的肝损伤与NO有关。     

Atopy patch test reactions in high-IgE beagles to different sources and concentrations of house dust mites

Protocols for atopy patch testing (APT) were evaluated on six high-IgE dogs sensitized to house dust mites (HDM) using various concentrations and sources of HDM. Two sources of HDM were compared: Heska slurry and four concentrations of Greer HDM. Saline was used as a negative control. Patches were removed after 48 h and the sites evaluated at 0, 6, 24, 48, 72 and 96 h for erythema, macules, papules and pustules. Each sign was scored from 0 to 3 (0 = absent and 3 = severe). Total score was used for analysis. Mean total scores significantly increased for both Greer and Heska HDMs from 6 h, peaking at 48 h for G100 (100 mg mL(-1)), G300 and G668, and at 72 h for Heska and G31.25. Across all times, Heska HDM scores were significantly higher than those of G31.25 with the largest difference at 96 h. Heska scores, however, were significantly lower than those of other Greer concentrations (G100, G300 and G668) particularly at 96 h. No reactions were noted at saline sites. It is concluded that Greer-HDM at 100 mg mL(-1) is the most suitable concentration for APT in dogs because it induces reactions comparable if not higher than more concentrated HDM preparations.     

Metabolism and residue depletion of albendazole and its metabolites in rainbow trout, tilapia and Atlantic salmon after oral administration

Metabolic and residue depletion profiles of albendazole (ABZ) and its major metabolites in three fish species, rainbow trout, tilapia and Atlantic salmon are reported. Based on these profiles, similarities (or dissimilarities) between species will determine the potential to group fish species. ABZ at 10 mg/kg body weight was incorporated into fish food formulated in a gelatin base or in gel capsule and fed as a single dose to six fish from each species. Rainbow trout were held three each in a partitioned 600-L tank. Tilapia and Atlantic salmon were housed in separate 20-L tanks. Samples of muscle with adhering skin were collected at 8, 12, 18, 24, 48, 72, and 96 h postdose from trout kept at 12 degrees C, at 4, 8, 12, 24, 48, 72, 96, 120, and 144 h postdose from tilapia kept at 25 degrees C and at 8, 14, 24, 48, 72, and 96 h postdose from Atlantic salmon kept at 15 degrees C. The samples were homogenized in dry ice and subjected to extraction and cleanup procedures. The final extracts were analyzed for parent drug ABZ and its major metabolites, albendazole sulfoxide (ABZ-SO), albendazole sulfone (ABZ-SO2) and albendazole aminosulfone using high-performance liquid chromatography with fluorescence detection. ABZ was depleted by 24 h in trout and tilapia and by 48 h in salmon; ABZ-SO, a pharmacologically active metabolite, was depleted by 48 h in tilapia, by 72 h in rainbow trout and was present until 96 h in salmon; and low levels of ABZ-SO2 and albendazole aminosulfone, both inactive metabolites, were detectable at least till 96 h in all three fish species.     

Attempts to immunize rats against infection with Fasciola hepatica using in vitro culture antigens from newly excysted metacercariae.

Attempts were made to immunise rats against Fasciola hepatica using the culture products obtained from the in vitro cultivation of newly excysted metacercariae. Three culture regimes were chosen: (1) medium NCTC 135 for 48 h (2) NCTC 135 + 20 per cent fetal calf serum (FCS) for 48 h (3) NCTC 135 + 20 per cent FCS for 14 days. The used culture medium from each of these regimes was concentrated, mixed with adjuvant and injected subcutaneously into rats. Similarly treated unused culture media was used in control rats. The rats were challenged with an oral dose of 20 F hepatica metacercariae 35 days later and autopsied 96 days after the start of the experiment. The fluke burdens in those rats which had received the culture antigens did not differ significantly from those in the control groups.     

Comparative quality assessment of buffalo (Bubalus bubalis) semen chilled (5°C) in egg yolk- and soya milk-based extenders

Egg yolk-Tris is most commonly used semen extender; however, its use involves hygienic risk, interference with fertility and poor microscopic examination. Therefore, replacement of egg yolk with a plant-based component with protective effects on spermatozoa would be advantageous. In present study, we observed effect of soya milk-based extenders on dilution and liquid preservation of Murrah buffalo bull semen at 5°C up to 72 h in comparison with conventional egg yolk-Tris extender (Ext.1). In experiment one, a total of 32 buffalo semen ejaculates from four animals were extended and preserved at 5°C for 72 h in soya milk-based extender (Ext.2) with different percentages (10%, 15%, 20%, 25% and 30%) of soya milk for optimization of soya milk concentration. Semen quality was assessed for individual motility, viability, membrane integrity and acrosome integrity at 0, 24, 48 and 72 h of liquid preservation. The results of experiment one indicated that 25% soya milk is an optimum concentration for buffalo bull semen extender preparation. A modified method was used to prepare another soya milk-based extender (Ext.3). In the second experiment, two soya extenders (Ext.2 and 3) with optimized concentration (25%) of soya milk were comparatively assessed with egg yolk-Tris extender (Ext.1) for semen quality parameters at 0, 24, 48 and 72 h of liquid preservation. The individual sperm motility at 0 and 24 h following dilution were found non-significant among extenders. However, after 48 h of dilution, individual motility in Ext.3 was observed significantly (p < 0.05) higher than Ext.1. After 24, 48 and 72 h of dilution sperm membrane integrity in Ext.3 was found significantly (p < 0.05) higher than Ext.1. Overall, comparative evaluation of sperm parameters obtained revealed that Ext.3 containing 25% soya milk can be used as a substitute of egg yolk-based extender for buffalo semen liquid preservation.     

Functional integrity of precision-cut liver slices from deer and cattle

Precision-cut bovine and cervine liver slices were incubated in RPMI 1640 media for up to 72 h, and cellular integrity was assessed utilizing the leakage of lactate dehydrogenase (LDH) and the formation of the formazan metabolite of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT). Leakage of LDH (80%) from the bovine and cervine slices was noted only following 10 h of culture, and similarly, the generation of MTT-formazan declined. Metabolic viability was determined using 7-ethoxycoumarin as the model substrate, which was metabolized by slices from both animal species in a time-dependent manner for at least 6 h to generate 7-hydroxycoumarin, which was secreted into the media primarily as glucuronide and sulphate conjugates. With both cervine and bovine slices metabolic activity decreased markedly after a 4-h preincubation as assessed following a further 2-h incubation in the presence of 7-ethoxycoumarin. Subsequently, ethoxycoumarin metabolism by bovine slices did not decrease further until 24 h and was still detectable at 72 h. In the case of cervine slices, activity declined gradually after 8 h, with no activity being detectable at 72 h. It may be concluded that cervine and bovine slices may be maintained metabolically active for 8-10 h, which should prove sufficient for xenobiotic metabolism studies to be performed.     

Effect of prostaglandin F2 alpha administration on early pregnancy in ewes

Two trials were conducted with ewes to determine the effects of prostaglandin F2 alpha (PGF) administration during the first week of gestation. In trial 1, ewes (n = 134) were checked for breeding activity once daily and half of them received 10 mg PGF im at either 0, 24, 48, 72, 96, 120 or 144 h after detection of a breeding mark. The other half served as uninjected controls. In trial 2, ewes (n = 153) were checked for breeding activity twice daily. Two-thirds of the ewes received 10 mg PGF at either 24, 36, 48, 60, 72, 84, 96, 108, 120 and 132 h following detection of a breeding mark. The other one-third of the ewes served as uninjected controls corresponding to treatment times of 24, 48, 72, 96 or 120 h. In trial 1, the percentage of ewes lambing as a result of first service decreased as time of administration of PGF increased. The first-service pregnancy rate was 87.5% for ewes given PGF at 0 h and 0% for ewes given PGF at 144 h. Fewer (P less than .05) ewes given PGF at 96, 120 or 144 h after first mating lambed than control ewes. Similarly in trial 2, fewer (P less than .05) ewes given PGF at 96, 108, 120 or 132 h after first mating lambed than did controls. The total number of ewes lambing as a result of the entire breeding season did not differ (P greater than .05) between treated and control ewes in trial 1 (88.2 vs 87.3%) or trial 2 (85.7 vs 83.3%).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of vitamin C supplementation on plasma ascorbic acid and oxalate concentrations and meat quality in swine

Two experiments were conducted to determine the effects of vitamin C supplementation 48 h before slaughter on plasma ascorbic acid and oxalate concentrations and its effect on pork quality. In Exp. 1, 16 pigs (87.8+/-2.13 kg BW) were blocked by sex and weight and assigned randomly within block to one of three vitamin C treatments: 1) control; 2) 1,000 mg/L; or 3) 2,000 mg/L supplemented in the drinking water for a 48-h period. This was then followed by an additional 48-h period without supplemental vitamin C. Vitamin C increased plasma ascorbic acid concentrations (11.6, 19.5, and 23.4 microg/mL for 0, 1,000, and 2,000 mg/L of vitamin C; P < 0.05) within 6 h of supplementation. Plasma ascorbic acid concentrations from treated pigs decreased and did not differ from those of control pigs (13.7, 18.2, and 18.6 microg/mL for 0, 1,000, and 2,000 mg/L of vitamin C; P = 0.30) within 2 h of ending supplementation. No differences in plasma ascorbic acid concentrations were found between the two levels of supplementation. Vitamin C did not affect plasma oxalate or cortisol; however, cortisol tended to increase quadratically (P = 0.077) with vitamin C after 96 h. In Exp. 2, 30 pigs (107.5+/-0.54 kg BW) were blocked by sex and weight and assigned randomly within block to one of three vitamin C treatments: 1) control; 2) 500 mg/L; or 3) 1,000 mg/L supplemented in the drinking water 48 h before slaughter. Pigs were slaughtered 4 to 5 h after vitamin C supplementation ended, and loin samples were collected for meat quality measurements. At the time of slaughter, no differences in plasma ascorbic acid or cortisol were observed, but oxalate tended (P = 0.074) to increase quadratically with increasing vitamin C. Muscle ascorbic acid at slaughter and lactic acid in muscle at 0 and 1.5 h after slaughter were not different; however, lactic acid increased (P = 0.048) quadratically at 24 h after slaughter. Vitamin C did not affect initial or ultimate pH. Initial fluid loss (P = 0.041), and fluid loss on d 4 (P = 0.014) and 8 (P = 0.076) of simulated retail display; L* on d 0 (P = 0.038), 4 (P = 0.010), and 8 (P = 0.051); a* on d 0 (P = 0.021); and b* on d 0 (P = 0.006), 4 (P = 0.035), and 8 (P = 0.017) were negatively affected in a quadratic manner when vitamin C was supplemented. Vitamin C tended (P = 0.086) to increase oxidation in chops on d 0, but not d 4 or 8. Results indicate that on-farm supplementation of vitamin C was generally not effective in improving pork quality, which may be related to timing relative to slaughter.     

Influence of foetal calf serum supplementation during in vitro embryo culture in Iberian red deer

Nowadays, the use of foetal calf serum (FCS) during in vitro embryo culture is very controversial. Whilst some authors have encouraged its use, others reject it because of its harmful effects. Although in vitro embryo production in red deer is a promising assisted reproductive technique, it is still in its infancy and a great effort is needed to update the protocols used. The aim of this study was to assess whether FCS supplementation in red deer embryo culture medium is necessary to produce blastocyst and, if so, when is the best time to add it in terms of blastocyst production and quality. In vitro blastocysts were cultured with FCS added at 24, 48 or 96 hours post‐insemination (hpi). In addition, a treatment without FCS was used as control. Six hundred and ninety‐four cumulus–oocyte complexes were collected for in vitro fertilization. Cleavage rate was examined at 48 hpi, and blastocyst yield was recorded on days 6, 7 and 8. FCS had no influence on cleavage and blastocyst rate for any of the treatments studied. However, the number of cells was higher (p = .025) in those blastocysts cultured with FCS from 48 hpi compared with FCS‐free culture media (93.88 ± 7.76 vs. 54.11 ± 8.36). In conclusion, the addition of FCS to the embryo culture medium at 48 hpi improves the quality of red deer blastocyst, although it does not affect the percentage of embryos obtained.     

Assessment of Extent of Apoptosis and DNA Defragmentation in Chilled Semen of Stallions During the Breeding Season

The objective of the study was to assess apoptosis and DNA defragmentation in equine semen diluted and chilled to +4°C. Semen was collected from nine fertile stallions, including four Arabian thoroughbreds and five coldbloods. Examinations were carried out immediately after semen collection (0) and at five storage times (24, 48, 72, 96 and 120 h). The basic semen evaluation was performed in terms of volume, sperm concentration, viable sperm percentage, progressive motility and morphology. Using flow cytometry, DNA defragmentation and cell membrane integrity of spermatozoa were determined. The results of basic tests did not demonstrate significant differences amongst stallions, except for progressive sperm motility, which was significantly higher (p < 0.05) in the semen of Arabian stallions. In the semen of the same stallions, a significant decrease in the percentage of alive spermatozoa was observed at 72, 96 and 120 h of storage, whereas a significant increase in the number of spermatozoa with DNA defragmentation was found after 24 h storage. In the semen of coldblood stallions, significantly reduced live spermatozoa percentage was observed at 96 and 120 h, while increased DNA defragmentation was observed at 48 h. These findings demonstrated that the semen of Arabian stallions chilled to +4°C retained original characteristics until 24 h of storage, whereas in coldbloods, these were preserved up to 48 h of storage.     

Plasma/muscle ratios of sulfadimethoxine residues in channel catfish (Ictalurus punctatus)

Channel catfish ( n = 84) maintained at a water temperature of 27°C were used in a feeding study to determine the plasma to muscle concentration ratios of sulfadimethoxine (SDM) and 4-N-acetylsulfadimethoxine residues. Sulfadimethoxine medicated feed was provided free choice at 42 mg SDM/kg body weight once daily for 5 days and the plasma and muscle concentrations of SDM were determined at selected withdrawal times (6, 12, 24, 48, 72, and 96 hours) following the last dose. Considerable variation in total SDM tissue concentration among fish within a sampling period was observed. For fish ( n = 12) at six hours post-dose, total SDM concentrations ranged from 1.4–24.8 μg/mL and 0.6–12.6 μg/g, with mean total SDM concentrations of 9.1 μg/mL and 5.3 μg/g for plasma and muscle, respectively. However, a mean plasma:muscle concentration ratio of 1.8:1 ± 0.3:1 was obtained over all concentrations and sampling periods. The plasma:muscle 95% t distribution interval for individual fish was 1.2:1 to 2.4:1. A correlation coefficient of 0.967 was obtained for the relationship between plasma and muscle total SDM concentration among individual fish ( n = 25). Results of this study indicate that plasma total SDM concentration may be used to identify samples containing violative SDM muscle residue. No fish contained total SDM muscle residues greater than the FDA tolerance (0.1 μg/g) by 48 hours following the final dose.