EFFECT OF REGION OF INTEREST SELECTION AND UPTAKE MEASUREMENT ON GLOMERULAR FILTRATION RATE MEASURED BY 99mTc-DTPA SCINTIGRAPHY IN DOGS

Determinations of different methods of measurement of uptake of 99mTc-DTPA using scintigraphy of glomerular filtration rate (GFR) were made from 29 studies on 10 healthy beagle dogs. GFR was measured by calculating the percentage dose uptake (integral method) and rate of uptake (slope method) of 99mTc-DTPA using manual kidney regions of interest (ROI) and automatic kidney and background ROIs at different time periods of the uptake phase. These results were compared using linear regression analysis to the GFR obtained from 99mTc-DTPA plasma clearance using multiple blood samples. The best correlation coefficient between percentage DTPA uptake and GFR by DTPA clearance (r = 0.84, P < 0.001) was derived from time intervals between 30s-120s with a perirenal background ROI at 1 or 2 pixels out from the kidney ROI using automatic kidney ROI at 20% threshold. With the slope method, the best correlation coefficient (r = 0.85, P < 0.001) was obtained from time intervals between 30s-peak with the background ROI at 2 pixels out from the kidney ROI using automatic ROI at 35% threshold. The offset was higher, and the correlation varied more with different ROIs and the method was unreliable at time intervals extending beyond the peak radioactivity. Manual kidney ROIs with automatic background ROIs had slightly lower correlations. With DTPA renography both integral and slope uptake method with automatic kidney and background ROIs are accurate methods to estimate the GFR, but that the integral method is much more stable to variations in ROI size and the duration of the uptake phase of the renogram.     

Plasma and blood volume in the calf from birth till 90 days of age.

Determinations of plasma volume were made of 9 clinically healthy Swedish Red and White calves from birth to 90 days of age by means of the isotop dilution technique. Commercially available ¹³¹I labelled human serum albumin was used. Calculation of the total blood volume was based on the plasma volume and packed cell volume.The plasma and blood volumes increased per kg body weight in average 17 and 14% respectively from directly after birth to 24 hrs. old. From 1 to 90 days of age the plasma and blood volume fell steadily per kg body weight. Plasma volume expressed as a percentage of body weight was 5.3% at birth, 6.5% at 1 day old, and 4.9% at 90 days old. Corresponding values for blood volume were 8.4, 9.3 and 7.0%.     

Ferrokinetic studies in normal and iron deficiency anemic calves.

Ferrokinetic studies were performed on control calves and on calves with experimentally induced iron deficiency anemia, all 15 weeks old.The plasma iron clearance half time was about 4 times shorter in the experimental than in the control group. The low plasma iron concentration in the anemic calves was partially compensated by a more rapid plasma iron disappearance. Therefore the difference in the plasma iron turnover rate was reduced.The mean value of plasma iron daily renewal rate was about 3 times higher in the experimental than in the control group.The maximum uptake of injected ⁵⁹Fe into blood cells was reached 14 to 16 days after injection. The uptake of ⁵⁹Fe was about 10% higher in the control than in the experimental group.Using the values from the ferrokinetic study, the iron need for calves could be estimated. The requirement of iron to maintain a normal and constant Hb in a calf weighing 100 kg at a growth rate of 1 kg/daily was estimated as being 17.5 mg/day. Based on information in the literature and assuming a retention of dietary Fe of 25%, the total daily iron need for such a calf gaining 1 kg/day would be 160–180 mg.     

Environmental Impact on Soil Nematodes Following the Use of the Ivermectin Sustained-release Bolus or the Nematophagous Fungus Duddingtonia flagrans to Control Nematode Parasites of Cattle in Sweden

Management of nematode parasites of grazing livestock is essential, but there is concern about the potential environmental risk from agents used in their control. In this experiment, parasites in young cattle were controlled, using ivermectin boluses or the predacious fungus Duddingtonia flagrans , over 3 years. Treatment differences were sought among the soil nematodes recovered from soil samples collected from the paddocks on which treated animals grazed, and compared with similar samples taken from an untreated control paddock. Analysis of the soil nematode fauna on 21 occasions failed to demonstrate any impact of parasite management on soil nematodes. In 0-22 mm soil total nematode abundance averaged 524 000 m -2 , with 18 nominal taxa and H' diversity 2.41. There were both underlying paddock and year-to-year, climate-related, differences. The results of this trial not only confirm the lack of any adverse environmental impact of D. flagrans , a promising biological control agent, on soil nematodes, but also fail to show any impact arising from the use of ivermectin boluses.     

The effect of parenteral iron supply on hematology, health, growth and meat classification in veal calves.

Twenty veal calves were fed milk substitute containing 19 mg Fe/kg; ten calves were supplemented with iron in accordance with their requirements and the other 10 were unsupplemented controls. Serum iron (SI), hemoglobin (Hb) and packed cell volume (PCV) were determined at the start of the experiment and then every third week. From 3 weeks after the start to the end of the experiment there were significant differences between SI mean values between treated and untreated calves. In the treated group the Hb mean values were unchanged during the experiment while the untreated group had a significant decrease. The mean PCV values were also decreased. The daily gain was 1.36 g higher per calf in the treated group. The feed consumption per kg gain was 18 g lower and the carcass weight was 4.2 kg higher per calf in the treated group. The points for color and structure of carcass were 2.5 units higher per calf in the untreated group. The incidence of enteritis was less in the treated calves than in the untreated ones.     

Evaluation of a Tissue Cage Model for Use in Cattle

Three different types of subcutaneous tissue cages were evaluated as sources of tissue fluid in cattle. The biochemical composition of fluid sampled at various intervals after insertion was analysed and compared to corresponding serum values. It was shown that steel netting cages were quickly obliterated by ingrowing tissue and therefore unsuitable. The two types of silicone rubber tubing cages, on the other hand, were not obliterated and could be sampled repeatedly for volumes of about 2 ml tissue cage fluid (TCF) up to at least 32 weeks after insertion. Repeated sampling in a 12 h period was also possible. The levels of total protein and albumin in TCF were lower than in serum, and were shown to decline in the first 12 weeks after insertion to a level of about 35% of the serum concentration. Calcium and magnesium levels were also lower in TCF as compared to serum. The levels of chloride and potassium were slightly higher in TCF than in serum. For sodium no difference was observed and the results for inorganic phosphorous were not uniform. Repeated sampling did not alter the total protein and albumin level in TCF. It was also shown that cages with larger open areas had lower total protein content.     

Evaluation of gastro-intestinal nematode parasite control strategies for first-season grazing cattle in Sweden

A three-year grazing experiment (1998-2000) was conducted with first-season grazing cattle (FSGC) on improved pastures in central-eastern Sweden. Comparison was made between five groups with 10 calves in each group where four of these were set stocked and either (1) untreated, (2) ivermectin bolus treated, (3) subjected to biological control with the nematophagous fungus Duddingtonia flagrans, or (4) treated with a copper wire particle bolus. The fifth treatment was an evasive grazing strategy, whereby untreated calves were turned out onto pasture used by older cattle the previous year and then these calves were moved to silage aftermath in mid-July. To introduce low-levels of parasite infection to the experiment, each animal received a 'priming dose' of approximately 5,000 Ostertagia ostertagi and 5,000 Cooperia oncophora infective third stage larvae immediately prior to the start of the first grazing year of the trial.Results showed that efficient and sustainable parasite control of FSGC was possible to achieve without the use of anthelmintics by using turnout pastures that the previous year had been grazed by older cattle, in combination with a mid-July move to aftermath leys. Biological control also proved beneficial but the efficacy was impaired if high faecal egg counts coincided with rapid dung pat degradation due to heavy rainfall. No indication of parasite control was observed with the copper wire particle bolus. It was also demonstrated that the impact of gastrointestinal (GI) parasitism varied between years and that the level of overwintering contamination is important but likewise, is unpredictable. Although faecal egg counts in 1999 were low, due both to a delayed turnout and drought for the major part of the grazing season, deposited eggs successfully developed to infective larvae and overwintered in large numbers. The population of overwintered infective larvae at the time of turnout in early May played an important role in the course of infection in 2000 and resulted in an average 65 kg advantage of the ivermectin treated calves compared with the untreated calves.Thus, this three-year grazing experiment has emphasised the importance of subclinical gastrointestinal nematode infections in FSGC in Sweden. In addition, the study has shown that adequate parasite control may be achievable without the use of anthelmintics.     

Seasonal translation of infective larvae of gastrointestinal nematodes of cattle and the effect of Duddingtonia flagrans: a 3-year pilot study

A study was conducted over 3 years (1998-2000) to investigate larval availability of gastrointestinal nematodes from faeces of cattle reared under different parasite control schemes. These cattle were part of a parallel, but separate grazing trial, and were used as donor animals for the faecal material used in this experiment. At monthly intervals, faeces were collected and pooled from three groups of first-season grazing cattle. These groups were either untreated, ivermectin bolus treated or fed the nematophagous fungus Duddingtonia flagrans. The untreated and fungus treated animals were infected with gastrointestinal nematodes and the number of eggs per gram (epg) pooled faeces ranged between 50 and 700 in the untreated group and between 25 and 525 epg in the fungus treated group. Each year between June and September, artificial 1 kg dung pats were prepared and deposited on pasture and protected from birds. The same treatments, deposition times and locations were repeated throughout the study. Larval recovery from herbage of an entire circular area surrounding the dung pats was made in a sequential fashion. This was achieved by clipping samples in replicate 1/4 sectors around the dung pats 4, 6, 8 and 10 weeks after deposition. In addition, coinciding with the usual time of livestock turn-out in early May of the following year, grass samples were taken from a circular area centred where the dung pats had been located to estimate the number of overwintered larvae, which had not been harvested during the intensive grass sampling the previous year. It was found that recovery and number of infective larvae varied considerably within and between seasons. Although the faecal egg counts in 1999 never exceeded 300 epg of the faecal pats derived from the untreated animals, the abnormally dry conditions of this year generated the highest level of overwintered larvae found on herbage in early May 2000, for the 3 years of the study. Overall, biological control with D. flagrans significantly reduced larval availability on herbage, both during and between the grazing seasons, when compared with the untreated control. However, the fungus did not significantly reduce overwintered larvae derived from early season depositions (June and July), particularly when dung pats disappeared within 2 weeks after deposition. Very low number of larvae (<3 per kg dry herbage) were sporadically recovered from grass samples surrounding the ivermectin bolus faecal pats.