Relationships between urea dilution measurements and body weight and composition of lactating dairy cows.

The objective of the present study was to investigate the potential of the urea dilution technique, coupled with live animal measures to predict the body components of dairy cattle. The study involved 104 lactating Holstein-Friesian cows offered grass silage-based diets. Urea space volume (USV) was calculated from 2 collection periods of blood samples following infusion of urea at 12 (USV12, kg) and 30 (USV30, kg) min after infusion, and then as a proportion of live weight (LW) or empty body weight (EBW). All cows were slaughtered within 2 d of the USV trials. Large ranges existed in EBW and empty body concentrations of water, crude protein (CP), lipid, ash, and gross energy (GE). The USV12 and USV30 were both positively related to LW, EBW, and empty body component weights. The r2 values for USV12 were greater than USV30. The r2 values in the relationships of EBW and empty body composition with USV, however, were smaller than those with LW. Nevertheless, the relationships were improved when both USV and LW were used as predictors, rather than using either alone. Adding milk yield and body condition score as supporting predictors to prediction equations using USV and LW data for EBW, lipid, and GE contents further improved the relationships (r2 = 0.93, 0.66, and 0.77, respectively). Internal evaluation of one-third of the present data using equations developed from two-thirds of the present data indicated that using USV, live weight, and other live animal variables as predictors, rather than using USV alone, considerably improved the prediction accuracy. It was concluded that USV can be used to predict body composition, but the relationships with USV were poorer than those with LW. The USV can only be used as a supporting variable to live weight for prediction of body components in lactating dairy cows.

Alveolar capillary basement membrane lesions in Goodpasture's syndrome and idiopathic pulmonary hemosiderosis.

An ultrastructural study of lung distinguised between lesions of the alveolar capillary basement membrane in a case of Good pasture's syndrome and in three cases of idiopathic pulmonary hemosiderosis. In Goodpasture's syndrome, diffuse vascular injury with wide endothelial gaps, diffusely fragmented basement membranes and an electron dense layer on the basement membrane was found. In idiopathic pulmonary hemosiderosis, focal ruptures of the basement membrane were associated with hydropic changes in pneumocytes and, although fibroblasts were not seen, collagen deposition occurred within the basement membrane. immunofluorescent studies failed to show deposition of immunoglobulins G (IgG), A (IgA), M (IgM) or C3 in the lung in either disease. The ultrastructural lesions appear to separate these clinically similar entities.

An ultrastructural study of the pathogenesis of tissue injury in limited Wegener's granulomatosis.

Intravascular lysis of leucocytes was an early event in the process of tissue injury in a patient with limited Wegener's granulomatosis. This lysis, with consequent liberation of free organelles into the circulation, was followed by platelet aggregation and fibrin deposition in vessels with intact endothelial cells. Necrosis of endothelial cells also occurred early in the tissue injury. Complete obstruction of vessel lumina, with necrosis of their walls and of alveolar pneumocytes, followed. The alveolar spaces filled with fibrin and cell debris, and macrophages and fibroblasts migrated into these areas. The ultrastructural findings offer a rationale for current therapy. Cyclophosphamide therapy led to improvement in the clinical state, pulmonary function and histological changes.

Nortestosterone is not a naturally occurring compound in male cattle.

Nortestosterone (beta-NT) is a hormonal growth promoter banned from livestock production in the EU. Following injection, the major metabolite in cattle is the 17 alpha-epimer (alpha-NT). However, this also occurs naturally in pregnant cattle. It is not known whether alpha-NT is also endogenous to intact or castrated male cattle. Three surveys were undertaken to assess whether alpha-NT is naturally produced in this subset of the population. Bile samples from a total of 1,281 cattle (73 bulls and 1,208 steers) from 366 herds were collected at slaughter and initially screened by using a semi-automated EIA with multi-analyte immunoaffinity chromatography (IAC) clean-up. Bile samples from a further 38 male cattle (10 bulls and 28 steers) were analysed by high-resolution gas chromatography-mass spectrometry (GC-MS) with IAC pretreatment. Only samples containing more than 2 ng/ml alpha-NT were subjected to GC-MS. With 2 ng/ml alpha-NT as a threshold for confirmatory testing, the false positive rate of the screening EIA was 1.8%. Bulls (n = 16) and steers (n = 179) from government farms (n = 2) and which were not treated with exogenous beta-NT, did not have measurable concentrations of alpha-NT in their bile. Bulls (n = 35) and steers (n = 606) taken from herds (n = 204) which had no previous history of illegal growth promoter abuse also did not have alpha-NT in their bile. Of 32 bulls and 451 steers of unknown treatment history sampled from herds (n = 160), 56 steers from 19 herds contained GC-MS confirmed concentrations of alpha-NT higher than the limit of quantification of the assay LOQ (0.7 ng/ml). Of these animals, two had beta-NT-containing injection sites and five had residues of the beta-agonists clenbuterol and mabuterol. Examination of the animal movement and ownership histories of the 56 confirmed positive animals strongly suggested that exogenous beta-NT had been administered at the presenting farm. It is concluded that alpha-NT is not endogenous to this subset of the cattle population and that detection of this hormone in bile from bulls and steers constitutes evidence of abuse.

Residues of clenbuterol in cattle receiving therapeutic doses: implications for differentiating between legal and illegal use.

Clenbuterol (CBL) can be used legally in the treatment of respiratory diseases and illegally as a growth promoter in animals. Liver and eye have previously been shown to be effective matrices for the detection of residual concentrations of the drug. The pharmacokinetics of CBL in therapeutically treated cattle were investigated. During treatment, many body fluids and tissues contained residues of the drug. After a 14 day withdrawal only eyes (mean 27.1 micrograms/kg), and to a much lesser extent lung and kidney (mean 0.3 micrograms/kg), contained detectable residues. By day 28 of withdrawal only residues in eyes were present (mean, 6 micrograms/kg). These persisted to the end of the trial (42 days withdrawal). It is concluded that it is not possible to differentiate between the legal and illegal use of CBL solely on drug residue analysis. Other information must be made available to regulatory bodies to enforce control programmes.

Production of twin calves with in vitro fertilised embryos: effects on the reproductive performance of dairy cows.

Attempts were made to produce twin calves by implanting in vitro fertilised and matured (IVF) embryos into dairy cows. Twinning rates were consistently at the lower end of the range reported to have been obtained with in vivo derived embryos. The low pregnancy rates, higher than expected early embryonic losses, and increased fetal deaths and abortions recorded may indicate that IVF embryos are less viable. Fetal oversize in single calves was a significant problem in the first two years of the trial. The subsequent conception rates of cows that calved twins and those that calved singles were similar in spite of a much higher incidence of retained placenta and an increased interval to first oestrus in the cows bearing twins.

Transfer of sulphamethazine from contaminated dairy feed to cows' milk.

Four groups of four healthy mid-lactation Friesian cows were fed a compound feeding stuff containing either 2, 10 or 250 mg sulphamethazine/kg, corresponding to 0, 2, 10 and 250 per cent of the therapeutic inclusion rate in rations for pigs, at a flat rate of 3 kg twice daily for 21 days, followed by a seven-day withdrawal period. The cows were machine-milked twice daily and pooled milk samples from each cow were analysed by a commercially available microbiological assay with a sensitivity of 100 micrograms/litre and by a high performance liquid chromatography (HPLC) procedure with a limit of detection of 10 micrograms/litre. No sulphamethazine was detected by HPLC in the milk samples taken from any of the cows fed the concentrate containing 2 or 10 mg/kg. The milk samples from all four cows fed the highest concentration of sulphamethazine contained from 21 to 120 micrograms/litre while they were being fed the contaminated concentrate. The cow with the highest concentrations of sulphamethazine was the only one which repeatedly tested positive by the microbiological assay. The concentration of sulphamethazine declined rapidly during the withdrawal period and the drug was not detectable by either method in samples taken from two days after the contaminated feed was withdrawn.

Biliary elimination of endogenous nortestosterone by pregnant cows.

A temporal study of the biliary elimination of endogenous 19-nortestosterone during two successive pregnancies was made in three cows with cannulated gall bladders. Bile samples were analysed for 17 beta-19-nortestosterone (beta-NT) and the 17 alpha-epimer (alpha-NT) by using high resolution gas chromatography and mass spectroscopy. No beta-NT was detected in any of the samples analysed. However, alpha-NT was detected from around 120 days of gestation in each of the cows. Peak concentrations were observed in the last week before calving and ranged from 9.5 to 36.7 ng/ml. After parturtion, the concentrations of alpha-NT declined rapidly and were undetectable by seven days after calving, and it was not detected again until after 120 days of gestation. The biliary concentrations of alpha-NT detected subsequently were similar to those observed in cattle several weeks after an exogenous injection of the synthetic ester beta-NT phenylpropionate.

Transfer of chlortetracycline from contaminated feedingstuff to cows' milk.

Three groups of four Friesian cows in mid-lactation were fed a compound feedingstuff contaminated with 2, 10 or 300 mg chlortetracycline/kg for 21 days, and were then fed an uncontaminated diet for seven days. A fourth group of four cows was fed an uncontaminated diet throughout the study. Daily pooled milk samples from each cow were analysed by high performance liquid chromatography (HPLC) with a detection limit of 50 microg chlortetracycline/litre. Chlortetracycline was detected in only two milk samples taken from one of the animals fed feed containing 300 mg 300 mg chlortetracycline/kg, and both contained less than the maximum residue limit (MRL) specified by the European Union (100 microg/litre). All the milk samples were also analysed by the Delvotest SP microbiological assay, which has a detection limit of 300 microg chlortetracycline/litre. During the treatment period, this method gave four presumptive false-positive results, because they were not confirmed by HPLC. Selected daily pooled samples from each treatment group were also analysed by the semi-quantitative Charm II radioreceptor assay with a detection limit of 10 microg chlortetracycline/litre. Immunoreactive chlortetracycline was detected only in the animals fed feed containing 300 mg chlortetracycline/kg and several of the results exceeded the EU MRL during the treatment period. No significant treatment effects on animal performance were observed. However, there was a trend towards a higher milk fat concentration (P<0.09) and a lower milk protein concentration (P<0.07) with increasing concentration of chlortetracycline in the diet.

Comparison of the effects of injections of nortestosterone phenylpropionate at single and multiple sites in cattle on the detection of its residues in plasma, urine and bile.

The synthetic androgen 17 beta-19-nortestosterone (beta-NT) has been used illegally as a growth promoter in cattle production in the European Union. The elimination of beta-NT and its metabolites in plasma and urine was studied in cattle which had received intramuscular injections of its phenylpropionate ester (NTPP) at either single or multiple sites at a dose rate of 1 mg/kg bodyweight. In both groups, the plasma concentrations of beta-NT, measured by enzyme immunoassay, were consistently greater than the assay's limit of quantification (0.24 ng/ml) during days 1 to 7 of the study. The mean (sd) maximum plasma concentration (Cmax) was significantly greater in the multiply injected animals (4.4 [0.48] v 2.7 [0.15] ng/ml), but other plasma pharmacokinetic parameters, AUC, CL, T1/2 beta, Tmax and MRT, were not significantly different in the two groups. The equivalent urinary concentrations exceeded the limit of quantification of the assay (4.5 ng/ml) for up to 24 days after injection. In a second study, the biliary concentrations of beta-NT and its 17 alpha-epimer (alpha-NT) were measured by gas chromatography-high resolution mass spectrometry after cattle were injected intramuscularly at either single or multiple sites with NTPP. Only alpha-NT was detected in bile for up to 62 days after injection at concentrations above the limit of quantification of the assay (0.7 ng/ml). It is concluded that in some animals, intramuscular injections of NTPP at several sites may decrease the period after injection during which free beta-NT and its metabolites are detectable in plasma and urine. After the injection of NTPP, alpha-NT was detected in bile for longer than it was detected in plasma or urine.

Plasma, urinary and biliary residues in cattle following intramuscular injection of nortestosterone laurate.

The synthetic androgen 19-nortestosterone (beta-NT) has been used illegally as a growth promoter in cattle production in the European Union. Elimination of beta-NT and its metabolites in plasma, urine and bile was studied in three cattle with cannulated gallbladders following intramuscular injection at a single site of 500 mg of the laurate ester (NTL) containing 300.5 mg beta-NT. Using enzyme immunoassay quantification, plasma Cmax of free beta-NT was 0.5 +/- 0.15 microgram/L (mean +/- SEM). Concentrations of free beta-NT in plasma were consistently greater than the assay limit of quantification (0.12 microgram/L) for 32.7 +/- 13.42 days. Mean residence time for the beta-NT in plasma was 68.5 +/- 20.75 days. Following sample preparation by immunoaffinity chromatography, high-resolution GC-MS was used to quantify beta-NT and alpha-NT in urine and bile. beta-NT was detected irregularly in urine from two of the three animals post injection. The principal metabolite present in the urine, alpha-NT, was detected for 160.3 +/- 22.67 days post injection. Cmax for alpha-NT in urine was 13.7 +/- 5.14 micrograms/L. Mean urinary AUC0-183 days for alpha-NT was 845.7 +/- 400.90 (microgram h)/L. In bile, alpha-NT was the only metabolite detected for 174.3 +/- 8.67 days post treatment. Cmax for alpha-NT in bile was 40.8 +/- 12.70 micrograms/L and mean biliary AUC0-183 days for alpha-NT was 1982.6 +/- 373.81 (microgram h)/L. Concentrations of alpha-NT in bile samples were greater than those in urine samples taken at the same time. The mean ratio of biliary:urinary AUC0-183 days was 3.0 +/- 0.72. It is concluded that bile is a superior fluid for detection of alpha-NT following injection of NTL, owing to the longer period during which residues may be detected after administration.

Arterialized capillary blood gases in exercise studies.

The PCO2, PO2 and pH of arterial blood and arterialized capillary blood from the ear lobe were compared in 13 patients at rest and during submaximal exercise. The mean capillary PCO2 was .6 mmHg lower than arterial PCO2 at rest and 1 mmHg lower in exercise. The variation in comparisons (S.D. 1.4 mmHg) at rest and exercise, was greater than between duplicate capillary samples (S.D. .7 mmHg). The mean capillary PO2 was 3.3 mmHg higher than arterial at rest, and 1.7 mmHg higher in exercise: the variation was also greater than for PCO2 (S.D. 5.2 MMHg at rest, 4.2 mmHg in exercise) and greater than in duplicate samples (S.D. 2.6 mmHg). A comparison was made of calculated cardiac output (indirect Fick method) and dead space: tidal volume ratio during exercise, using arterial PCO2 and capillary PCO2: cardiac output was systematically overestimated by 6% (S.D. 9.3%) and VD/VT ratio underestimated by 10% (S.D. 9-3%) when capillary PCO2 was used in the calculations. Capillary blood samples are an acceptable alternative to arterial blood, for measurement of blood gases and pH, as long as blood flow is brisk enough to fill a large (125 mgl) glass capillary tube within 30 seconds. The accuracy of the estimates is greatest for pH, and least for PO2. The PCO2 and PO2 measurements are sufficiently precise for their use in the calculation of cardiac output, VD/VT ratio, alveolar-arterial PO2 difference and venous admixture effect during exercise.