Evaluation of digital and optical refractometers for assessing failure of transfer of passive immunity in Chianina beef–suckler calves reared in Umbria

Abstract

There are few published data on the accurate on-farm diagnosis of failure of transfer of passive immunity (FTPI) in beef-suckler calves. This observational study aimed to evaluate the diagnostic performance and differences among four types of refractometers for assessing FTPI in Chianina beef-suckler calves. Blood samples were collected from 85 Chianina calves aged 2-7 days. The serum immunoglobulin G (IgG) concentration was measured using radial immunodiffusion (RID), digital and optical serum total protein (STP) refractometers, and digital and optical serum refractometers. The diagnostic performance of the refractometers was determined based on the serum IgG threshold of 16 g/L (measured by RID). A receiver operating characteristic (ROC) curve was used to identify the optimal cutoff values for all refractometers. The RID IgG concentration was positively correlated with all four refractometers (correlation coefficient: 0.75-0.84). ROC analysis yielded optimal cutoff values for predicting FTPI of 51 g/L (sensitivity (Se)¼0.63 and specificity (Sp)¼0.96) and 52 g/L (Se ¼ 0.69 and Sp ¼ 0.90) for the digital and optical STP refractometers, respectively. At the threshold of 8.3% Brix, the Se and Sp were 0.66 and 0.92 for the optical Brix and 0.77 and 0.92 for the digital Brix refractometer, respectively. All four refractometers were useful for assessing FTPI in Chianina calves. However, the digital Brix had the highest combined diagnostic accuracy for FTPI. The on-farm use of refractometers to assess FTPI can become part of routine monitoring of the colostrum management program in beef-suckler calf herds. HIGHLIGHTS The cutoff values were 51 and 52 g/L for the digital and optical serum total protein refractometers, respectively. The digital Brix refractometer was the most accurate for the detection of calves with inadequate transfer of passive immunity.

An Assessment of the Accuracy of Digital and Optical Brix Refractometers for Estimating Passive Immunity in Beef Calves

“…The optimal cut-off value we ascertained in the present study for the D-Brix refractometer for the estimation of IgG concentrations of <16 g/L was similar to previously reported digital Brix percentages for IgG of <16 g/L (Gamsjäger et al, 2021;Pisello et al, 2021;Akköse et al, 2022c). The cut-off value we determined for the D-Brix refractometer for estimating IgG concentrations of <24 g/L was higher than the digital Brix refractometer cut-off value previously reported by Gamsjäger et al (2021) and lower than the digital Brix refractometer cut-off value previously reported by Akköse et al (2022c).…”

“…The cut-off value we determined for the D-Brix refractometer for estimating IgG concentrations of <24 g/L was higher than the digital Brix refractometer cut-off value previously reported by Gamsjäger et al (2021) and lower than the digital Brix refractometer cut-off value previously reported by Akköse et al (2022c). The cut-off value ascertained for the O-Brix refractometer for estimating IgG concentrations of <16 g/L was similar to the optical Brix refractometer cut-off value reported by Pisello et al (2021). The present study proposes, for the first time, a cut-off value for the optical Brix refractometer for estimating serum IgG concentrations of <24 g/L in beef calves.…”

“…Our study compared the diagnostic accuracy of optical and digital Brix refractometers in predicting different passive immunity statuses in beef calves. To date, only very few studies have assessed digital Brix percentages indicative of serum IgG of <16 g/L (Gamsjäger et al, 2021;Pisello et al, 2021;Akköse et al, 2022c) or <24 g/L (Gamsjäger et al, 2021;Akköse et al, 2022c). On the other hand, there is no report on optical Brix percentages indicative of serum IgG of <24 g/L.…”

“…In a recent study in beef calves, digital Brix refractometer cut-off values of ≤8.4% and ≤8.8% were reported for the estimation of serum IgG concentrations of <16 g/L and <24 g/L, respectively (Gamsjäger et al, 2021). In a study describing ITPI as being associated with a serum IgG concentration of <16 g/L, a cut-off value of ≤ 8.4% was proposed for the digital Brix refractometer (Pisello et al, 2021). Our research team has recently found digital and optical Brix refractometers cut-off values of <8.5% and <10.1% for the estimation of serum IgG concentrations of <16 g/L and <24 g/L, respectively, (Akköse et al, 2022c).…”

“…It is also possible to use Brix refractometers in determining colostrum quality (Buczinski et al, 2016). While a large number of comparative studies are available on the utility and performance of refractometers in diagnosing ITPI in dairy calves (Buczinski et al, 2021;Akköse et al, 2022a:b), there are only very few studies that have evaluated refractometry methods for the assessment of passive immunity status in beef calves (Vandeputte et al, 2011;Todd et al, 2018;Gamsjäger et al, 2021;Pisello et al, 2021;Akköse et al, 2022c). This study aimed at determining and comparing the diagnostic accuracy of digital and optical Brix refractometers for the prediction of different passive immunity statuses in beef calves, and at demonstrating the correlation and agreement level of the results achieved with these refractometers.…”