Biomedical subjects

C J McLaren

Publications and source records attributed to C J McLaren.

6 recordsLinked to original sources

PubMed2006

An evaluation of two indirect methods of estimating body weight in Holstein calves and heifers.

Monitoring the growth of replacement heifers is a useful management tool to assist producers in achieving a reasonable goal for age at first calving. Standard growth curves have been established, and heart girth tapes are widely available to estimate body weight (BW). Probably the easiest, and undoubtedly the most accurate, means of determining the actual BW of heifers is by using a calibrated electronic scale. However, if an electronic scale is not available, indirect methods of BW estimation are required. The hipometer is a new indirect tool that uses the external width between the greater trochanters of the left and right femurs to estimate BW. The purpose of this observational study was to evaluate the hipometer and the heart girth tape to estimate the BW of Holstein heifers, as compared with their actual weight recorded by an electronic scale. A total of 311 Holstein heifers in 4 research herds, ranging in age from 1 wk old to immediately prior to calving (24 mo), were used in this comparison. The mean BW of all heifers was 261 +/- 124 kg. The Pearson values of the correlation between the scale and hipometer weights, and the scale and tape weights were 0.92 and 0.94, respectively. The concordance correlations of scale weight with hipometer and tape weights were 0.98 and 0.99, respectively. The agreement among the 3 methods, as assessed by the kappa statistic, was substantial for heifers aged 3 to 15 mo. However, poor to no agreement was observed in heifers younger than 3 mo, as well as at 15 mo of age or greater (kappa 0 to 0.18). This is of particular concern because these groups represent the age when dairy heifers would be weaned (< 3 mo) and the age when breeding would normally commence (> 15 mo). We concluded that the hipometer is an easy and useful alternative method of estimating the BW of Holstein heifers, particularly in heifers aged 3 to 15 mo.

Animals↗

PubMed2005

The association of herd milk production and management with a return-over-feed index in Ontario dairy herds.

Associations of herd milk production and management variables to a return-over-feed (ROF) herd profit index were examined among 95 dairy farms. The ROF index is derived from 2 important determinants of profit on dairy farms: milk income and feed cost. All producers were participants in the Dairy Herd Improvement (DHI) ROF program in Ontario, Canada during 2002. Nutrition, housing, health, and other management data were collected through a phone survey of herd managers. Herd milk production, milk component percentages, and somatic cell count data were obtained from the Ontario DHI database. The linear regression model accounting for significant variation in ROF with highest R2 (0.66) included standardized milk production, milk protein percentage, milk fat percentage, and use of monensin in lactating cow rations. A 1-kg increase in standardized milk production (kg/d per cow) or a 0.1 percentage unit increase in milk protein was associated with $0.35/d per cow or $0.26/d per cow increase, respectively, in the ROF of the dairy herd. However, a 0.1 percentage unit increase in milk fat was associated with a $0.10/d per cow decrease in ROF, probably because of a negative association of milk fat with milk yield. Use of monensin in lactating cow rations was associated with a $0.39/d per cow increase in ROF. In a separate model (R2 = 0.27) that examined management factors independent of production variables, herds using 3 times daily milking had a $1.25/d per cow higher ROF vs. herds using twice daily, whereas use of an Escherichia coli mastitis vaccine was associated with $0.59/d per cow higher ROF. Production-related variables accounted for more variation in the ROF index than management variables, and the latter, e.g., use of monensin, only marginally increased R2 of production-based regression models.

Animal Feed↗

PubMed2002

Vesico-ureteric reflux in the young infant with follow-up direct radionuclide cystograms: the medical and surgical outcome at 5 years old.

OBJECTIVE: To compare the 5-year outcome of 82 infants with vesico-ureteric reflux (VUR) against the initial (< 1 year) and follow-up results of the direct radionuclide cystogram (DRC). PATIENTS AND METHODS: An initial DRC was taken at a mean age of 0.6 years and the follow-up study at 1.7 years. VUR was graded using 'one-third bladder volume' grades (BVG) of 'low', 'moderate', 'high' and 'void', with 'low' considered the most severe. Renal scintigraphy was used to assess renal scarring in 80 of the 82 patients. The outcome at a minimum age of 5 years was defined as resolved reflux, those with corrective surgery or those still being medically followed. RESULTS: Those being followed comprised 29%, corrective reflux surgery 17% and resolved 54% of the patients. Children with VUR grades of 'high' or 'moderate' (as the worst grade either side) were more likely to have resolution than those with 'low' (by four and two times, respectively). Reflux at 'low' bladder volume was 2.6 times more likely to be associated with renal scarring than the other grades combined. 'Low' reflux was present in nine of 14 children needing surgery. There was a linear relationship between VUR grade and the scintigraphic findings. CONCLUSION: The severity of VUR can be assessed from the bladder-volume graded DRC. Continuing VUR at 'low' BVG is associated with increased renal scarring, resistance to natural resolution and corrective reflux surgery.

Child, Preschool↗

PubMed2001

Direct comparison of radiology and nuclear medicine cystograms in young infants with vesico-ureteric reflux.

OBJECTIVE: To determine the sensitivity of the direct radionuclide cystogram (DRC) in detecting vesico-ureteric reflux compared with the micturating cysto-urethrogram (MCU) in the same initial setting, in infants younger than one year. PATIENTS AND METHODS: The results from the dual cystograms of 62 refluxing infants < 1 year old (mean 0.58) were compared. Results from same-day renal scintigraphy with dimercaptosuccinic acid (DMSA) in 60 of the 62 infants were also compared with the reflux grades. RESULTS: Reflux was detected in 105 units, 96 detected on the DRC and 47 on the MCU, representing a sensitivity of 91% and 45%, respectively. The DRC missed half of grade 1, 20% of grade 2 and 6% of grade 3 reflux. Reflux at low bladder filling rates (DRC) represented 40% of all reflux units, and a half (52%) of scarred renal units detected by DMSA scintigraphy. CONCLUSIONS: In young infants the MCU may fail to detect significant reflux and the DRC may fail to detect the lesser grades. The combination of both cystograms in the initial investigation of reflux provides more comprehensive information.

Cystoscopy↗

PubMed1986

Technegas--a new ventilation agent for lung scanning.

A simple process using technetium-99m generator eluate in a graphite crucible at 2500 degrees C, produces a structured ultra-fine dispersion of labelled carbon. Particle sizes are 5.0 nm (0.005 micron) and less and adhere to the walls of the alveoli on inhalation. Penetration characteristics are gas-like and the radioactivity per litre of carrier argon allows single breath inhalations of a diagnostic dose. Over 190 patients have been studied including 50 within a formal clinical trial with xenon-133. Results of tomography, dynamic inhalation, and image subtraction using this new agent-'Technegas'--are presented.

Carbon↗

PubMed1986

Lung ventilation studies with technetium-99m Pseudogas.

Technetium-99m Pseudogas is an ultrafine near monodisperse aerosol of 0.12-microgram diam particle size. This report describes initial clinical experiences with 27 patients referred for investigation of suspected pulmonary embolism, and in whom Pseudogas ventilation images were compared with a high quality commercial aerosol. An additional group of ten patients with severe COPD was examined in a comparative trial of Pseudogas with 81mKr. Pseudogas was better than a conventional aerosol in reaching a diagnosis of pulmonary embolism using a simple blinded comparison with coded images. In addition, bronchial deposition was minimal unless COPD was severe. Moderately well patients had no difficulty inhaling the necessary activity in one or two breaths, and even severely ill and frail aged persons could accomplish the passive breathing maneuver in less than a minute. Clearance of Pseudogas was directly to the systemic circulation with a half-time of 10 min in normal subjects extending up to 100 min in patients with airways disease.

Adolescent↗