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Investigation of brix refractometry for estimating bovine colostrum immunoglobulin G concentration
Donald Sockett1, Ryan M Breuer1,2, Lindsey W Smith1
1Wisconsin Veterinary Diagnostic Laboratory, University of Wisconsin-Madison, Madison, WI, United States.
Insights
A digital Brix refractometer cannot precisely predict colostrum IgG concentration. However, specific Brix thresholds can estimate minimum IgG levels, guiding strategic colostrum feeding for newborn calves to ensure passive immunity.
Area of Science:
- Veterinary Medicine
- Animal Science
- Dairy Production
Background:
- Dairy operations commonly use Brix refractometers to evaluate first-milking colostrum quality.
- Accurate assessment of colostrum quality is crucial for successful passive immunity transfer in newborn calves.
- Digital Brix refractometers offer a potential tool for rapid colostrum assessment.
Purpose of the Study:
- To determine if a digital Brix refractometer can predict colostrum immunoglobulin G (IgG) concentration.
- To identify specific %Brix thresholds for estimating different minimum colostrum IgG concentrations.
- To evaluate the utility of Brix refractometry in guiding colostrum feeding strategies for calves.
Main Methods:
- Colostrum samples (n=182) were analyzed using a digital Brix refractometer and single radial immunodiffusion (SRID) for IgG concentration.
- Simple linear regression was employed to correlate %Brix readings with IgG concentrations.
- Receiver operating characteristic (ROC) analysis identified %Brix cutoffs with no false positives.
Main Results:
- Linear regression showed a R² value of 0.818 and a large S-value (21.7 g/L), indicating poor predictive accuracy for IgG concentration.
- %Brix thresholds of 19.0, 22.0, 25.0, and 30.0 were identified to estimate minimum IgG concentrations of 25, 50, 75, and 100 g/L, respectively.
- These cutoffs allow for strategic feeding of smaller, adequate colostrum volumes.
Conclusions:
- Digital Brix refractometry is not suitable for precise prediction of colostrum IgG concentration.
- Established %Brix cutoffs can effectively estimate minimum IgG levels, enabling targeted colostrum feeding.
- Strategic feeding based on Brix thresholds can optimize passive immunity transfer and reduce calf-side effects.
Abstract:
Many dairy operations uses a Brix refractometer to assess the quality of first-milking colostrum. This study investigated whether a digital Brix refractometer could be used in a model to predict colostrum IgG concentration and whether more than one %Brix threshold could be used for different colostrum IgG concentrations. Colostrum from 182 animals was tested using a digital Brix refractometer and by single radial immunodiffusion. Statistical analysis, using simple linear regression to relate %Brix results with corresponding colostral IgG concentration, and receiver operating characteristic (ROC) analysis were used to identify %Brix cutoffs that had no false positive results. Colostral IgG concentrations from digital Brix refractometry had a R2 value of 0.818 and a S-value of 21.7 g/L. The large S-value shows that a digital Brix refractometer should not be used in a model to predict colostrum IgG concentration. However, %Brix scores of 19.0, 22.0, 25.0 and 30.0 percent can be used to estimate minimum colostral IgG concentrations of 25, 50, 75 and 100 g/L. These four cutoffs can be used to strategically feed smaller volumes of colostrum to newborn calves. Smaller volumes may reduce unwanted side effects and shorten the time interval in which calves refuse to nurse, while still delivering an adequate mass of IgG to have successful transfer of passive immunity.
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