Determination of flunixin residues in bovine muscle tissue by liquid chromatography with UV detection

A new and sensitive liquid chromatography-ultra violet method with a detection limit of 6 ng/g (ppb) and a limit of quantification of 15 ng/g was developed for the determination of flunixin residues in bovine muscle tissue. Flunixin in homogenized animal tissue was extracted with acetonitrile after enzyme digestion. The tissue digest (extract) was then cleaned up on a solid-phase extraction cartridge and eluted with acidified hexane. After the eluate was evaporated to dryness under nitrogen at 55 degrees C, the residue was reconstituted in 1 mL mobile phase solution and analyzed by reversed-phase gradient chromatography with UV detection at 285 nm. The method was then applied in a survey study of slaughter animals to determine whether flunixin is being used in an off-label manner for veal and beef production in Canada.

Depletion of penicillin G residues in tissues, plasma and injection sites of market pigs injected intramuscularly with procaine penicillin G

Procaine penicillin G was administered by intramuscular (i.m.) injection to groups of healthy 100 kg market pigs at the approved label dose (15,000 IU/kg body weight), once daily for three consecutive days; or an extra-label dose (66,000 IU/kg body weight), once daily for five consecutive days. Penicillin G residue depletion was followed in plasma, tissue and injection sites using a liquid chromatographic method. Groups of pigs were killed 1, 2, 3, 4, 5 and 8 days after the last injection with the label dose. Penicillin G was not detected in liver after 1 day of withdrawal, in muscle and fat after 2 days of withdrawal, in plasma after 4 days of withdrawal, in skin after 5 days of withdrawal, or in kidney and the injection sites after 8 days of withdrawal. Other groups of pigs were killed 1, 2, 3, 5 and 7 days after injection with the extra-label dose. In these pigs penicillin G was not found in liver after 2 days of withdrawal, in fat after 3 days of withdrawal, or in the muscle, skin, plasma and injection sites after 7 days of withdrawal. Penicillin G was found at all times in the kidneys of the groups of pigs that received the high dose. The technique used for neck injections was critical to obtain intramuscular rather than intermuscular injections. The Bureau of Veterinary Drugs, Health Protection Branch, Health Canada calculated that the appropriate withdrawal period for pigs was 8 days for a dose of 15,000 IU procaine penicillin G/kg body weight and 15 days for a dose of 66,000 IU/kg.

Bacterial inhibition tests used to screen for antimicrobial veterinary drug residues in slaughtered animals

Bacterial inhibition tests used to screen milk, tissues, blood, and urine for antimicrobial veterinary drug residues must be high volume, quick, rugged, inexpensive, and sensitive. Bacterial inhibition tests--such as the Swab Test on Premises (STOP), the Calf Antibiotic and Sulfa Test (CAST), the Fast Antibiotic Screen Test (FAST), the Charm Farm Test (CFT), the Antimicrobial Inhibition Monitor 96 (AIM-96) assay, the German Three Plate Test, the European Union Four Plate Test and the New Dutch Kidney Test--have been used to screen tissues for antimicrobial activity. The CFT and the Brilliant Black Reduction Test (BBRT) also have been used to screen plasma. The Live Animal Swab Test (LAST) was developed to screen urine. This review examines the use and limitations of these screening tests for regulatory control and avoidance of veterinary drug residues in meat. The ideal bacterial inhibition test for screening antimicrobial residues in slaughtered animals does not exist. Each of the current and potential tests has limitations.

Determination of trimethoprim and sulphadoxine residues in porcine tissues and plasma

Healthy gilts and market-ready hogs were administered a single intramuscular (IM) injection of Borgal, a commercial formulation of trimethoprim-sulfadoxine (TMP-SDX), once or twice daily. The objectives were to determine if a newly-developed high-performance liquid chromatographic (HPLC) method would be suitable for measuring the residual concentrations of TMP in the plasma of these live animals, and to determine if the administration of this veterinary drug would leave measurable residues in their plasma and tissues at slaughter. Plasma and tissue concentrations of SDX and TMP from these animals were determined over a period of 14 d using thin-layer chromatography/densitometry (TLCD), and the newly-developed HPLC method, respectively. The lowest detectable limit (LDL) for SDX in plasma and tissue was 20 ppb by TLCD. The HPLC method had a LDL of 5 ppb for TMP in plasma and tissue. Both methods were then used to provide baseline data on the absorption and depletion of TMP and SDX from these healthy animals. It was observed that both TMP and SDX were readily absorbed into the blood and tissues, but TMP was eliminated much faster than SDX. No TMP residues were detected in the plasma of any of the gilts at and beyond 21 h after drug administration. Also, no TMP residues were detected in the plasma of any of the market-ready hogs 24 h after drug administration at either the label dose or twice the label dose. Sulfadoxine residues at concentrations above the maximum residue limit (MRL) of 100 ppb were, however, detected in the plasma, muscle, kidney, liver, and injection sites of hogs slaughtered 1 and 3 d after a single IM administration at the label dose. Although SDX residues were still detectable in the lungs, kidney, liver and plasma of some hogs 10 d after administration of the label dose and twice the label dose, these were below the MRL. Postmortem examination revealed necrosis and inflammation at the injection sites, but no visible deposits of the injected drug.

Application of an enzyme immunoassay for the determination of sulphamethazine (sulphadimidine) residues in swine urine and plasma and their use as predictors of the level in edible tissue

The potential of an enzyme immunoassay (EIA) with high cross-reactivity towards the major metabolite (N4-acetyl-sulphamethazine) of sulphamethazine was tested for screening fluids and tissues. Healthy pigs were given 20 mg sulphamethazine per kg body weight per day in their drinking water for 2 days. Groups of four pigs were slaughtered after 3, 4 and 7 days withdrawal. The results were compared with liquid chromatographic analysis for urine, plasma, kidney, liver, gluteal muscle and diaphragm. In general, concentrations found by the EIA were higher than those found by liquid chromatography (LC) because sulphamethazine metabolites were detected by the EIA and not by LC. Using the EIA for the detection of sulphamethazine and the major metabolite in urine and plasma, predictive relationships (tissue-fluid ratios) for the concentration of the parent drug in tissue, determined by LC, were calculated. The tissue-plasma ratios for muscle, liver and kidney were 0.1, 0.2 and 0.1, respectively. The tissue-urine ratios for muscle, liver and kidney were 0.02, 0.03 and 0.03, respectively. Owing to the higher concentration of the parent drug in both fluids, the presence of the major metabolite in urine and the sensitivity of the EIA, tissue can be screened for low concentrations of sulphamethazine.

Residue depletion in tissues and fluids from swine fed sulfamethazine, chlortetracycline and penicillin G in combination

Twenty-four hogs were fed a ration for 14 days containing three times the recommended label dose of a combination drug which included sulfamethazine, chlortetracycline and penicillin G. Groups of six hogs were slaughtered 0, 2, 4, or 8 days after withdrawal. Six untreated control hogs were slaughtered 5 days before the first group, of six treated hogs, were slaughtered. Residue concentrations were determined in kidney, liver, muscle, serum and urine. At zero withdrawal the kidney from one hog contained 0.018 mg penicillin G per kg and the serum from the same hog contained 0.016 mg penicillin G per litre. Penicillin G was not detected in any other samples that were analysed. Chlortetracycline concentrations in tissues at zero withdrawal time were below accepted Canadian Maximum Residue Limits (MRL) for chlortetracycline of 1 mg/kg in muscle, 2 mg/kg in liver and 4 mg/kg in kidney and were below the limit of quantitation in all tissues 4 days after withdrawal. Sulfamethazine persisted in the tissues longer than penicillin G or chlortetracycline. Sulfamethazine concentrations were above the Canadian MRL of 0.1 mg/kg at zero withdrawal time and did not decrease to below the MRL until 8 days after withdrawal. Our results suggest that, if the label withdrawal period of 10 days is observed, an increase in the dosage of up to three times the recommended rate is unlikely to increase significantly the risk that residues would occur in the tissues of treated hogs at concentrations which exceed MRLs. Sulfamethazine concentrations in all matrices decreased after storage at -76 degrees C for 6 months.

Chlortetracycline, oxytetracycline, and tetracycline in edible animal tissues, liquid chromatographic method: collaborative study

Thirteen laboratories analyzed samples of edible animal tissues for tetracycline residues. The method included extraction of analytes into buffer, elution from a C18 solid-phase extraction (SPE) cartridge, and reversed-phase liquid chromatographic (LC) analysis, including use of a confirmation column. An additional laboratory, using an alternative LC assay based on a different sample cleanup, also analyzed the samples. Results showed the 2 methods are comparable. The LC method for determination of cholortetracycline, oxytetracycline, and tetracycline in edible animal tissues has been adopted by AOAC INTERNATIONAL. Results from 13 laboratories indicate that the method under study provides generally better results at the higher concentrations tested than at concentrations near the detection limit and that there is less problem with interferences in muscle tissue than in kidney. The method can achieve reliable results for analytes and matrixes studied at concentrations from 0.1 to 0.6 ppm and above, depending on the analyte-matrix combination, with generally better performance to be expected with muscle than with kidney. The poorer performance for fortified samples, particularly kidney, was attributed to additional homogenization steps required to prepare these samples. Recovery of analytes from different lots of solid-phase extraction (SPE) cartridges was an important variable.

Comparison of four commercially available rapid test kits with liquid chromatography for detecting penicillin G residues in bovine plasma

Four commercially available rapid tests (Brilliant Black reduction test, LacTek test, Charm Farm test, and Charm Test II receptor assay) were compared with a liquid chromatographic (LC) method (lowest quantitatable level of 5 ng/mL) in their efficiency, reliability, and sensitivity to detect penicillin G in bovine plasma. Samples were obtained from 16 steers treated with procaine penicillin G alone or in combination with its long-acting form, benzathine penicillin G. The steers were injected intramuscularly with penicillin G doses ranging from label dose to about 9 times label dose. When results of the Brilliant Black reduction, LacTek, Charm Test II, and Charm Farm tests for penicillin G in plasma (with detection sensitivities of 5, 10, 20, and 30 ng/mL, respectively) were compared with results of LC, none of the rapid tests gave false-positive results. Each rapid test elicited a positive response when used to test bovine plasma containing penicillin G residues at concentrations above the test's detection sensitivity. The simplicity, selectivity, and sensitivity of the rapid tests, coupled with rapidity with which results are obtained, make them suitable for use in large-volume preslaughter screening of penicillin-treated cattle.

Investigation of Charm Test II receptor assays for the detection of antimicrobial residues in suspect meat samples

Charm Test II receptor assays for beta-lactams, sulfonamides, (dihydro)streptomycin and erythromycin were applied to 257 bovine muscle and kidney samples, and 215 porcine muscle and kidney samples collected from animals suspected to contain antimicrobial residues. The assays were run in conjunction with Agriculture and Agri-food Canada's routine diagnostic confirmation analyses for suspect samples collected at federally inspected packing plants. All samples were subjected to the Charm Test II receptor assays and thin layer chromatography-bioautography (TLC-BA). Selected samples were quantitatively analysed using a liquid chromatographic method for penicillin G and a thin layer chromatography-fluorescence densitometry (TLC-FD) method for sulfonamides. The Charm Test II assays for beta-lactams, (dihydro)streptomycin and erythromycin were an acceptable alternative to the TLC-BA screen for laboratory confirmation of the presence of these compounds, with enhanced sensitivity for (dihydro)streptomycin and erythromycin. In addition, the Charm Test II provided a sensitive screen for sulfonamides as confirmed by the standard TLC-FD procedure. The analysis time, laboratory space and analyst time required to complete the Charm Test II assays is less than that for TLC-BA. Operating costs are similar for both analyses, but the Charm Test II does require capital expenditure for a scintillation counter.

Disposition of penicillin G after administration of benzathine penicillin G, or a combination of benzathine penicillin G and procaine penicillin G in cattle

Plasma concentration of penicillin G was evaluated in beef steers after administration of either a combination of benzathine penicillin G and procaine penicillin G in a 1:1 mixture at a dosage of 9,000 U/kg of body weight, IM (n = 5), 24,000 U/kg, IM (n = 5), or 8,800 U/kg, SC (n = 5), or benzathine penicillin G alone at a dosage of 12,000 U/kg, IM (n = 7). Plasma concentration of penicillin G was measured by use of a high-performance liquid chromatography assay that had a limit of determination of 0.005 microgram/ml. At a dosage for this combination of 9,000 U/kg IM, and 8,800 U/kg, SC, which are approved label recommendations in Canada, and the United States, respectively, mean (+/- SEM) peak plasma concentration was 0.58 (+/- 0.15) and 0.44 (+/- 0.02) microgram/ml, respectively. Although plasma penicillin concentration was quantifiable for 7 days in the steers that received 9,000 U/kg, IM, and for 4 days in the steers that received 8,800 U/kg, SC, the concentration was < 0.1 microgram/ml in both groups after the first 12 hours. After administration of the combination at dosage of 24,000 U/kg, IM, there was an initial peak plasma concentration at approximately 2 hours; thereafter, plasma concentration decreased slowly, with half-life of 58 hours. Although plasma penicillin G concentration was quantifiable for 12 days at this dosage, concentration was < 0.1 microgram/ml after the first 48 hours. After the initial 48 hours, plasma concentration of penicillin was of similar magnitude and decreased at similar rate for the combination at dosage of 24,000 U/kg and for 12,000 U/kg of benzathine penicillin G alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Depletion of penicillin G residues in tissues and injection sites of yearling beef steers dosed with benzathine penicillin G alone or in combination with procaine penicillin G

The contribution of benzathine penicillin G to residues in tissues and injection sites of yearling beef steers was assessed by treating seven groups of five to seven steers with either benzathine and procaine penicillin G together or benzathine penicillin G alone. Steers were injected with a commercial combination of benzathine and procaine penicillin G according to the Canadian (intramuscular) or United States (subcutaneous) label dosages of 8600 and 8800 IU penicillin G/kg body weight, respectively. They were killed 14 or 30 days after the intramuscular injections, and 30 days after the subcutaneous injections. At the label withdrawal times, Canadian 14 days and United States 30 days, the levels in the injection sites for all of the treatments were 30-60 times above the Canadian and United States' Maximum Residue Limit of 50 micrograms/kg, while liver, kidney and gluteal muscle levels were below the Maximum Residue Limit. Other steers were injected intramuscularly with 24,000 IU benzathine/procaine penicillin G/kg body weight and slaughtered 8, 14 or 50 days after injection. Fifty-day injection site residues were 24 times the Maximum Residue Limit. Another group of steers was injected intramuscularly with benzathine penicillin G alone at 12,000 IU/kg body weight and slaughtered 14 days later. Penicillin G levels in the injection sites were 156 times the Maximum Residue Limit. The persistence of penicillin G residues at the injection sites in all the treatment groups appears to be attributable primarily to benzathine penicillin G. Visual inspection of muscle surfaces did not reliably reveal all injection site lesions in the underlying musculature.

Depletion of intramuscularly and subcutaneously injected procaine penicillin G from tissues and plasma of yearling beef steers

Withdrawal periods required when doses of 24,000 IU and 66,000 IU of procaine penicillin G/kg body weight were administered to yearling beef steers by intramuscular injection daily for five consecutive days were investigated. These dosages are in excess of product label recommendations, but are in the range of procaine penicillin G dosages that have been administered for the treatment of some feedlot bacterial diseases. The approved dose in Canada is 7,500 IU/kg body weight intramuscularly, once daily, with a withdrawal period of five days. Based on the tissue residue data from this study, the appropriate withdrawal period is ten days for the 24,000 IU/kg body weight dose and 21 days for the 66,000 IU/kg body weight dose when administered intramuscularly to yearling beef steers. In a related study, 18 yearling beef steers received 66,000 IU of procaine penicillin G/kg body weight administered by subcutaneous injection, an extra-label treatment in terms of both dose and route of administration, typical of current practice in some circumstances. Deposits of the drug were visible at subcutaneous injection sites up to ten days after injection, with more inflammation and hemorrhage observed than for intramuscular injections of the same dose. These results suggest that procaine penicillin G should not be administered subcutaneously at high doses; and therefore a withdrawal period was not established for subcutaneous injection.

A study of the disposition of procaine penicillin G in feedlot steers following intramuscular and subcutaneous injection

The disposition of an aqueous suspension of procaine penicillin G (300,000 U/mL) was studied in feedlot steers. Four groups of three steers were used. Steers in groups 1 and 2 received procaine penicillin G once daily for 5 days intramuscularly (i.m.) at a dose of 24,000 U/kg (group 1) or of 66,000 U/kg (group 2). The injection on the last day was administered in the gluteal muscle. Steers in group 3 (i.m. neck injection) and group 4 [subcutaneous (s.c.) injection] each received a single dose of procaine penicillin G at a dose of 66,000 U/kg. From every animal, after the last injection in groups 1 and 2 and following the single injection in groups 3 and 4, a series of blood samples was taken at fixed time intervals. The plasma from these samples was analysed for penicillin G by a high performance liquid chromatography (HPLC) assay in order to determine the disposition of penicillin. The maximum plasma concentration (Cmax) and the area under the curve (AUC) were significantly different between groups 1 and 2, but we found no difference in the disappearance rate constant between these two groups. Group 4 single s.c. injections produced a lower mean Cmax (1.85 +/- 0.27 microgram/mL) than the mean Cmax (4.24 +/- 1.08 micrograms/mL) produced in group 3 by i.m. injections into the neck muscle or the mean Cmax (2.63 +/- 0.27 microgram/mL) produced in group 2 by i.m. injections into the gluteal muscle. However the mean Cmax produced by i.m. injections into the neck muscles (group 3) was higher than the mean Cmax produced by i.m. injections into the gluteal muscle (group 2). Additionally, the disappearance t1/2 was longer (18.08 h) in group 4 following the s.c. injection and shorter (8.85 h) in group 3 following the i.m. neck injection, than the t1/2 following administration of the same dose i.m. into the gluteal muscle (15.96 h) in group 2. In this study, when procaine penicillin G was injected into the gluteal muscle, doses of 66,000 U/kg were necessary to produce plasma concentrations that were above a minimum inhibitory concentration (MIC) for penicillin G of 1.0 microgram/mL as compared to doses of 24,000 U/kg.

Determination of penicillin G in bovine plasma by high-performance liquid chromatography after pre-column derivatization

A simple, selective, and sensitive liquid chromatographic method with ultraviolet detection was developed for the analysis of penicillin G in bovine plasma. The assay utilizes a simple extraction of penicillin G from plasma (with a known amount of penicillin V added as internal standard) with water, dilute sulphuric acid and sodium tungstate solutions, followed by concentration on a conditioned C18 solid-phase extraction column. After elution with 500 microliters of elution solution, the penicillins are derivatized with 500 microliters of 1,2,4-triazole-mercuric chloride solution at 65 degrees C for 30 min. The penicillin-mercury mercaptide complexes are separated by reversed-phase liquid chromatography on a C18 column. The method, which has a detection limit of 5 ng/ml (ppb) in bovine plasma, was used to quantitatively measure the concentrations of penicillin G in plasma of steers at a series of intervals after the intramuscular administration of a commercial formulation of procaine penicillin G.

Performance of Five Screening Tests for the Detection of Penicillin G Residues in Experimentally Injected Calves

Three calves were each injected with a single intramuscular (IM) dose of penicillin G procaine at either 3750, 7500, or 15000 IU per kg of body weight and killed at 24 h postinjection, along with a control calf that had not received penicillin. Tissues were tested by the Swab Test on Premises (STOP), the Calf Antibiotic and Sulfa Test (CAST), the Brilliant Black Reduction Test (BBRT), the Charm Test II, thin layer chromatography - bioautography (TLC/BA), and high performance liquid chromatography (HPLC). Samples of muscle, liver, and kidney from all injected calves contained detectable penicillin residues when analyzed by HPLC. The BBRT and Charm Test II were the most sensitive test kits for penicillin G in muscle, while the Charm Test II also detected residues in livers and kidneys from all injected animals. The STOP and CAST were less sensitive, although improved performance was observed for the STOP using a modified growth medium. Penicillin residues were detected in all livers and kidneys from injected animals using TLC/BA. Urine collected from injected animals 12 and 24 h postinjection was positive by the Live Animal Swab Test (LAST). All urine and tissue samples from the control animal were negative. The BBRT and Charm Test II appear to offer greater sensitivity for penicillin G residues than such currently used procedures as STOP and CAST but should be confirmed by a suitable laboratory method, such as the HPLC procedure used in this study.

Bioassay techniques and high-performance liquid chromatography for detection of oxytetracycline residues in tissues from calves

Tissue specimens from muscle, liver, kidney, and injection sites were collected, and serum was obtained from 3 calves euthanatized on each of posttreatment days 5 and 22. Calves were treated with 6.7, 13.4, or 20 mg of oxytetracycline (OTC)/kg of body weight, IM, once daily for 3 days; these dosages are 1, 2, and 3 times the label dose, respectively. One control calf was euthanatized on each of posttreatment days 5 and 22. In treated male calves killed 2 days after the last injection, OTC residues were detected in all tissues and serum, using high-performance liquid chromatography. Tissues from all injection sites also were considered positive for antimicrobial residues, using the swab test on premises (STOP), microbial inhibition test (MIT), and thin-layer chromatography-bioautography (TLCB) test. Kidney tissues from a calf given 13.4 mg of OTC/kg and kidney and liver tissues from a calf given 20 mg of OTC/kg also were considered positive, using the MIT and TLCB. Results of the STOP only were considered positive for the liver and kidney of a calf given 20 mg of OTC/kg, but substitution of Saskatoon antibiotic medium-3 for the original medium (antibiotic medium-5) allowed the STOP to detect residues in these tissues from all treated calves. In female calves killed 19 days after the last injection, the STOP, MIT, and TLCB procedures revealed positive results for tissues from some injection sites, but revealed negative results for other tissues.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of diet on the response in rats to lead acetate given orally or in the drinking water

Liver lead levels were higher for rats that were orally dosed with 100 mg lead acetate/kg body wt and fed a semipurified diet than those fed a pelleted diet. The activities of delta-aminolevulinic acid dehydratase in blood were decreased in the group given 10 micrograms lead acetate/mL in their drinking water and fed the semipurified diet, but not in the blood from the group treated with lead and fed the pelleted diet. The levels of glutathione in the liver decreased in response to lead acetate in the drinking water of rats fed the semipurified diet, but not in the livers from the group fed the pelleted diet and treated with lead. The levels of lead in the kidneys were higher in the group given lead acetate in their drinking water and fed the semipurified diet than in the lead treated group fed the pelleted diet. Rats dosed orally with lead or given lead in the drinking water and fed the semipurified diet were more sensitive to lead treatment than those fed the pelleted diet.

Effect on blood, liver, and kidney variables of age and of dosing rats with lead acetate orally or via the drinking water

Levels of lead in the livers and kidneys of rats increased in proportion to the dose of lead acetate that the rats were given orally or in the drinking water. The activities of delta-aminolevulinic acid dehydratase (DALAD) in blood and liver decreased when the rats were dosed with lead, whereas glutathione levels in the blood increased. The decrease in the activity of blood DALAD was the most sensitive indicator of lead toxicity. Levels of lead in the livers and kidneys decreased after 3, 7, and 14 d of lead withdrawal. The activities of blood DALAD increased after 3 d of lead withdrawal. Groups of rats that initially weighted an average of 140 g were killed at weekly intervals for 6 wk. Blood hematocrits and liver glutathione levels increased, and blood DALAD and activated DALAD from blood decreased with increasing age of the rats. Activated DALAD activities from liver increased after the first week of the study.

A comparison of three bioassay techniques and high performance liquid chromatography for the detection of chlortetracycline residues in swine tissues

Three bioassay procedures used for the detection of chlortetracycline (CTC) residues in tissues from swine were compared with high performance liquid chromatographic analysis. Procedures were tested on incurred tissues from 3 groups of 4 pigs each treated as follows: group B, 110 mg CTC/kg diet for 28 days; group C, 220 mg CTC/kg diet for 28 days; group D, 220 mg CTC/kg diet for 21 days, followed by 7 days without CTC in the ration. A fourth group (A) of 4 pigs were fed the same basal ration as the other 3 groups without added CTC. All tissue samples from all groups tested negative by the swab test on premises (STOP) used at slaughter plants and by a laboratory microbial inhibitor test (MIT). A thin-layer chromatography-bioautography (TLB) procedure currently used for STOP confirmations detected CTC residues in the liver of 1 pig from group B and 2 pigs from groups C, as well as in kidneys of 3 pigs from group B. All tissues from groups B and C, with the exception of one liver from group B, contained detectable CTC residues using HPLC analysis, as did one kidney from group D. The control tissues (group A) were free of residues. The results indicated that the TLB procedure is more sensitive for the detection of CTC residues than the STOP or the MIT procedures, and that the STOP procedure is unable to detect levels of CTC in the range of 0.1 to 1.4 mu/g in livers and kidneys from swine tested at slaughter.

Persistence of chloramphenicol residues in calf tissues

Twenty-one 5 to 18 day old calves were administered 11 mg chloramphenicol in propylene glycol per kg body weight intramuscularly twice daily for three days. Groups of calves were euthanized with a barbiturate overdose at 5, 21, 42 and 70 days after the last dose was administered. Serum, kidney, analyzed for the drug using a quantitative gas chromatographic method with a detection limit of five parts per billion. After five days of withdrawal, chloramphenicol was detected in all the injection sites and in 6 out of 16 of the other samples. After 21 days of withdrawal, chloramphenicol was detected in all the injection sites and in one each of the serum, liver and muscle samples. After 42 days of withdrawal, chloramphenicol was detected in the injection sites only, and after 70 days of withdrawal it was not detected in any of the samples.

Trace element levels in liver and kidney from cattle, swine and poultry slaughtered in Canada

Levels of arsenic, cadmium, copper, mercury and lead were determined in approximately 650 samples of liver and kidney from cattle, swine and poultry slaughtered in Canada during 1979-81. In addition zinc levels were determined in livers and kidneys from swine, and selenium and zinc levels were determined in the livers and kidneys from cattle. Depending on the element several methods of atomic absorption spectroscopy were used to analyze samples including flame, hydride generation, cold vapour generation and graphite furnace atomization. Analyses were also done by plasma emission spectroscopy. Levels of arsenic over 2.0 micrograms/g were detected in 0.9% of swine livers and 0.3% of swine kidneys. Cadmium levels higher than 1.0 micrograms/g were detected in 0.3% of cattle livers, 10.8% of cattle kidneys, 1.8% of swine kidneys, 0.4% of poultry livers and 0.3% of poultry kidneys. Levels of copper over 150 micrograms/g were detected in 0.4% of cattle and swine livers. Levels of lead over 2.0 micrograms/g were detected in 1.4% of poultry livers and 1.6% of poultry kidneys. The highest level of mercury detected in all species was 0.25 micrograms/g and the highest level of selenium was 1.9 micrograms/g. Zinc levels of over 100 micrograms/g were detected in 1.7% of cattle livers, 0.2% of cattle kidneys and 5.0% of swine livers.

Studies on long chain cis- and trans-acyl-CoA esters and Acyl-CoA dehydrogenase from rat heart mitochondria

The beta-oxidation of long chain fatty acids was investigated in a preparation of rat heart mitochondria. The acyl-CoA esters of the cis and trans isomers of delta9-hexadecenoic, delta9-octadecenoic, delta11-eicosenoic, and delta13-docosenoic acids were prepared. Rates of the acyl-CoA reaction were determined with an extract from rat heart mitochondria. The apparent Michaelis constant (Km) and maximum velocity (Vmax) were calculated for each substrate. In general, apparent Vmax values decreased with increasing chain length of the monoenoic substrates. Reduced activity of acyl-CoA dehydrogenase with long chain acyl-CoA esters could have contributed to accumulation of lipids in hearts of rats fed diets containing long chain fatty acids.

Estimations of rates of synthesis and degradation of several rat mammary gland enzymes from changes in enzyme activities

Based upon rates of decrease in the activities of citrate cleavage enzyme (EC 4.1.3.7), malic enzyme (EC 1.1.1.40), fatty acid synthetase, UDPglucose pyrophosphorylase (EC 2.7.7.9), UDPglucose 4-epimerase (EC 5.1.3.3), and glucose-6-phosphate dehydrogenase (EC 1.1.1.49) in rat mammary glands after adrenalectomy–ovariectomy on the 11th day of lactation, the half-lives of the enzymes were estimated to be 28, 31, 28, 50, 20, and 24 h, respectively. The half-life estimates for UDPglucose pyrophosphorylase and glucose-6-phosphate dehydrogenase compared favorably with previous estimates of 35 and 20 h, respectively, obtained in rats 5 days postpartum utilizing specific immunological techniques. In a second experiment, increases in the activities of enzymes in adrenalectomized, lactating rats after initiation of cortisol therapy were investigated. Rats were adrenalectomized on the 5th day of lactation and cortisol therapy was started 5 days later. The estimated half-lives for citrate cleavage enzyme, malic enzyme, fatty acid synthetase, UDPglucose pyrophosphorylase, UDPglucose 4-epimerase, the A protein of the lactose synthetase complex, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase (EC 1.1.1.44), and hexokinase (EC 2.7.1.1) were, respectively, 84, 60, 92, 76, 170, 102, 79, 88, and 81 h.

Hormonal regulation of rat mammary gland enzyme activities and metabolite patterns

Activities of nine enzymes and the levels of 15 metabolites were determined in mammary glands from normal (N) and adrenalectomized–ovariectomized (AO) rats in midlactation. Mammary gland weights and mammary DNA did not change between day 11 and day 19 of lactation in N animals and were not affected appreciably by AO. Four days after AO the activities of citrate cleavage enzyme, malic enzyme, UDPglucose pyrophosphorylase, the A protein of the lactose synthetase complex, and glucose-6-phosphate dehydrogenase were decreased to 24, 59, 53, 52, and 56% of day 11 N. These same enzymes require cortisol therapy to increase in activity after adrenalectomy on the 5th day of lactation. Activities of phosphoglucomutase, 6-phosphogluconate dehydrogenase, fructose-1,6-diphosphate aldolase, and isocitrate dehydrogenase were not affected by AO. These enzymatic changes are discussed in relation to systems regulating milk synthesis. Mammary glucose levels increased 1.9-fold in AO animals. Levels of triose phosphate, α-glycerol phosphate, and aspartate in AO animals were decreased to 52, 49, and 62% of N. The proportion of high-energy phosphate bonds to total adenine nucleotides was not affected by AO. Ratios of [free NADP]/[free NADPH2] were not significantly affected by AO or stage of lactation. Metabolite patterns are discussed in relation to changes in enzyme activities and in vitro tracer data.

Effects of adrenalectomy, adrenalectomy--ovariectomy, and cortisol and estrogen therapies upon enzyme activities in lactating rat mammary glands

The effects of adrenalectomy and adrenalectomy–ovariectomy on the 5th day of lactation followed by cortisol and estrogen therapies on enzyme activities in rat mammary glands were investigated. This stage of lactation was selected because mammary secretory cell proliferation is essentially complete at this time thereby enabling study of the effects of cortisol and estrogen on enzyme levels in a nonproliferating secretory cell population. Eighteen enzymes were selected for study on the bases of their respective roles in milk biosynthesis and carbohydrate and energy metabolism and/or on the basis of previous studies indicating that their activities increase during midlactation or are regulated, in part, by steroid hormones. After adrenalectomy on the 5th day of lactation, cortisol therapy was required for normal increases in the activities of succinic dehydrogenase, citrate cleavage enzyme, malic enzyme, UDPglucose pyrophosphorylase, UDPglucose 4-epimerase, and glucose-6-phosphate dehydrogenase. The activities of UDPglucose pyrophosphorylase and glucose-6-phosphate dehydrogenase were higher than normal in cortisol-treated animals. Cortisol therapy during the last 2 days of the experiment increased the activity of UDPglucose pyrophosphorylase and possibly citrate cleavage enzyme. The activities of α-glycerolphosphate dehydrogenase, phosphoglucomutase, 6-phosphogluconate dehydrogenase, pentose phosphate metabolizing ability, hexokinase, phosphofructokinase, fructose-1,6-diphosphate aldolase, pyruvate kinase, lactic dehydrogenase, aspartate aminotransferase, isocitrate dehydrogenase, and extramitochondrial malate dehydrogenase were not notably affected by adrenalectomy or cortisol therapy. The activities of 6-phosphogluconate dehydrogenase, pentose phosphate metabolizing ability, phosphofructokinase, and pyruvate kinase may have increased after the 5th day of lactation in adrenalectomized as well as in normal animals. Combining ovariectomy with adrenalectomy reduced pup weight gains more than adrenalectomy alone, but did not further decrease significantly the activities of any of the enzymes measured. Ovariectomy had no effect when cortisol was administered. Cortisol therapy completely reversed adverse effects of estrogen given to adrenalectomized–ovariectomized animals. On the bases of these and previous data, it was concluded that cortisol regulates the rates of synthesis of several mammary gland enzymes during midlactation.

EFFECTS OF VARIOUS HEAT AND MOISTURE TREATMENTS ON MYROSINASE ACTIVITY AND NUTRITIVE VALUE OF SOLVENT-EXTRACTED CRAMBE SEED MEAL

Solvent-extracted crambe meal, uncooked, dry-heated, autoclaved or steam-stripped, was fed as 0, 5 or 10% of the diet to weanling mice. Ground rapeseed (1% of the diet) was fed in a cross-treatment as a source of myrosinase.Uncooked crambe meal significantly depressed (P < 0.05) feed intakes and gains. Heating by any method tested resulted in significant improvement, but feeding value remained below that of the casein-soybean protein control diet. The addition of the myrosinase source had little effect.In a second experiment, ground seed of crambe, rape and camelina (Crambe abyssinica Hochst., Brassica napus L. and Camelina sativa Crantz) were compared as myrosinase sources when incorporated 1:4 into cooked crambe meal and allowed to react overnight at room temperature with 0 or 30% moisture in the mixture. After this enzyme treatment, half of each mixture was autoclaved to destroy myrosinase prior to ration mixing and feeding.Appreciable hydrolysis of thioglucosides occurred in vitro at 30% moisture, resulting in marked growth depression. The feeding of active myrosinase similarly depressed animal responses, apparently through in vivo thioglucoside hydrolysis. All sources of enzyme were effective.The failure to obtain more enzyme response in the first experiment was attributed to lower enzyme concentration and inferior enzyme-substrate proximity during the time when conditions were otherwise appropriate for thioglucoside hydrolysis.

THE FEEDING VALUE OF SOLVENT-EXTRACTED CAMELINA MEAL EFFECTS OF LEVELS FED, HEAT TREATMENTS AND FLAVOR SUPPLEMENTS

Camelina seed was ground, solvent-extracted, and fed at levels of 0, 5, 10, 15, 20 and 25% of the diet to weanling mice. Licorice (0 and 0.025%) was tested as a cross-treatment to modify flavor. Levels up to 10% resulted in no adverse effects on growth of mice but each increase in level beyond 10% resulted m a significant (P <.05) reduction in gains and feed intakes. Licorice was ineffective.In a second experiment 20 to 22% of camelina meal was fed m all diets. Raw meal was compared with dry-heated meal (12 hours, 135 °C), autoclaved meal (15 min, 1.2 kg/cm2), steam-stripped (2 hours, 110 °C) and a casein–methionine–supplemented control diet. In each case, four myrosinase-source supplements were added: nil, crambe seed, rapeseed, and camelina seed (Crambe abyssinica Hochst., Brassica napus L., and Cameline sativa Crantz).Destruction of myrosinase by any method of heating resulted in significantly better feeding value of camelina meal, but steam stripping was superior to dry heating or autoclaving.It was concluded that camelina meal is probably superior to rapeseed and crambe meals, in that more than 10% of raw meal is tolerated in the diet before growth depression occurs. Near maximum growth was obtained with myrosinase-free diets containing about 20% meal. Growth depression that occurred at the higher levels of intake exceeded that which could be accounted for by the content of volatile isothiocyanates.