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Background Brix refractometry can be used to assess colostral immunoglobulin G (IgG) concentration, but studies identifying Brix percentages to detect high‐ and low‐IgG colostrum are lacking for beef cows and interlaboratory agreement is unknown. Objectives Evaluate Brix refractometer performance and interlaboratory agreement for assessing beef cow colostrum IgG concentration, including determination of thresholds to identify colostrum containing IgG concentrations <100 g/L and ≥150 g/L. Animals Beef cows (n = 416) from 11 cow‐calf operations in Alberta, Canada. Methods Colostral IgG concentrations were measured using radial immunodiffusion (RID) and estimated by Brix refractometry for this retrospective study. Spearman correlation coefficients were assessed between RID and Brix refractometry. Likelihood ratios and misclassification cost‐term analysis were used to determine optimal Brix percentages for detecting colostrum containing IgG concentrations <100 g/L and ≥150 g/L. Concordance correlation coefficient (CCC) and Bland‐Altman analyses were performed for Brix percentages obtained at 3 different laboratories. Results Brix percentages obtained at 3 laboratories were positively correlated with IgG results (r = 0.72, 0.68, and 0.76, respectively). Colostrum Brix percentages of <24% and ≥30% were optimal for indicating IgG concentrations of <100 g/L and ≥150 g/L, respectively. Interlaboratory agreement was substantial, with CCC ranging from 0.89 to 0.96 and Bland‐Altman analysis showing small mean differences (−1.2% to 0.09% Brix) and narrow limits of agreements (−4.8% to 2.4% Brix) among laboratories. Conclusions and Clinical Importance Brix refractometry shows good potential for reliably estimating IgG concentrations in beef cow colostrum across multiple laboratories and can be recommended to aid colostrum management decisions on farms.

The aim of this research was to evaluate the effects of postpartum day and parity season on the lactoferrin (LF), immunoglobulin G (IgG), and chemical composition of Murciano–Granadina goat colostrum during the first 96 h after kidding, and the use of the Brix refractometer to estimate IgG content. A herd of 3500 intensively managed Murciano–Granadina dairy goats (45–50 kg body weight) was used. Colostrum samples were collected from days 1 to 4 postpartum in the winter, spring, summer, and autumn. The colostrum composition was assessed using an automated infrared method; the LF and IgG concentrations were measured using an ELISA, and for the Brix percentage, we used a digital refractometer. Colostrum taken on the first postpartum day showed the highest concentrations of LF, IgG, proteins and non-fat solids (NFSs). As the postpartum days progressed, a rapid decrease in the LF, IgG, protein, and NFS contents and the Brix value was observed. In contrast, the lactose content increased steadily until the fourth postpartum day (p < 0.001). The season influenced milk yield, LF, IgG, protein, fat, and somatic cell content (p < 0.05). LF contents were significantly higher in the spring season, IgG contents were higher in autumn colostrum, and fat components were higher in the winter season. The colostrum Brix value showed a positive correlation with the ELISA colostrum LF (r = 0.716, p < 0.001) and IgG (r = 0.894, p < 0.001) determination; a 20 mg IgG/mL colostrum concentration corresponded to 18 °Brix. Our results corroborate the importance of feeding colostrum to newborns on the first day after birth, not only because of its high level of IgG but also because of its greater presence of the other bioactive protein compounds such as lactoferrin.

Colostrum is an essential source of immunoglobulin G (IgG) for neonate piglets. However, colostrum IgG content and nutritional composition can vary considerably among sows due to age, parity, feeding regime and immunological background. Currently, there is no practical way to obtain information about colostrum IgG concentration at herd level. We evaluated sows’ colostrum IgG content on-farm using a Brix refractometer and its performance was compared with that of an IgG ELISA. In addition, nutritional compositions of the colostrum samples were analyzed using Fourier transform IR spectroscopy. Colostrum samples (5 to 6 ml) (n=153) were obtained within 0 to 3 h of farrowing. However, to obtain a 24 h IgG profile for 11 sows, colostrum samples were collected at 0, 2, 4, 6, 8, 10, 16 and 24 h after farrowing. A 0.3 ml of freshly drawn colostrum sample was used for the on-farm measurement of Brix percentages using a digital refractometer shortly after collection. The remaining fractions of the samples were frozen and submitted to laboratory analysis for total IgG, using a commercially available pig IgG ELISA kit. For nutritional composition analysis, a 35 ml colostrum sample (n=34) was obtained immediately after birth of first piglet from the first three pairs of frontal teats. Colostrum concentrations of IgG averaged 52.03±30.70 mg/ml (mean±SEM) at 0 to 3 h after farrowing. Concentration of IgG decreased on average by 50% during the 1st day of lactation (P<0.01). Sow parity did not influence colostrum concentrations of IgG. Differences in colostrum composition were recorded between two herds and among the parity groups (P<0.05). The Brix refractometer measurement of colostrum and the corresponding log transformed IgG measurements from the ELISA were moderately correlated (r=0.63, P<0.001, n=153). Based on the classification we suggest here, low levels of IgG (14.5±1.8 mg/ml) were recorded for colostrum samples with Brix readings below 20%. Borderline colostrum IgG content (43.8±2.3 mg/ml) had Brix readings of 20% to 24%, adequate colostrum IgG content (50.7±2.1 mg/ml) had Brix % readings of 25% to 29% and very good IgG colostrum content (78.6±8.4 mg/ml) had Brix readings >30%. Colostrum IgG concentration is highly variable among sows, Brix measurement of a sows’ fresh colostrum is an inexpensive, rapid and satisfactorily accurate method of estimating IgG concentration, providing indication of differentiation between good and poor IgG content of colostrum.

Brix refractometry has been widely demonstrated to be a useful tool for monitoring colostrum management program and passive immunity transfer (PIT) in Bovines, but its suitability has never been verified in Buffalo. Therefore, the objective of this study was to evaluate the utility of a simple and rapid tool such as a digital Brix refractometer to estimate colostrum quality and for evaluating the success of passive transfer of immunoglobulin G (IgG) in Buffalo calves. The optimal cut points levels for Brix Refractometry for distinguishing good- and poor-quality colostrum and for assessing the adequacy of passive immunity transfer in calves were determined. For this aim, 26 first-milking maternal colostrum (MC) were collected from first-calf heifers. Blood samples were obtained from their calves at birth (T0) and 72 hours after (T3). Colostrum and Serum IgG content were determined by indirect enzyme-linked immunosorbent assay (ELISA), whereas total protein (TP, g/dL) and percentage Brix (%Brix) by means of a digital Brix refractometer. The mean colostrum IgG was 64.9 ± 29.3 mg/mL. The mean serum %Brix at T3 was 9.6 ± 0.9 %. The mean serum IgG content at T3 was 11.1 ± 2.0 mg/mL. Pearson’s correlation coefficient (rp) was determined between Brix and ELISA measurements: colostrum %Brix showed a significant correlation with serum %Brix (rp = 0.82, p < 0.001); serum %Brix was highly correlated with serum TP (STP, g/dL) (rp = 0.98, p < 0.001) and serum IgG (mg/mL) (rp = 0.85, p < 0.001). A cut point of 18% Brix to estimate samples of MC ≥ 50 mg/mL from first-calf heifers was more appropriate for the buffalo. A cut point of 8.4% Brix resulted in the greatest percentage of calf serum samples being correctly classified. Based on our findings, a digital Brix refractometer could be a useful tool to monitor colostrum quality and to estimate PIT in Buffalo calves.

Objective This study aimed to determine the color, fat, viscosity, IgG concentration, %Brix and refractive index of fresh postpartum colostrum of German Holstein dairy cattle and assess the impact of different thermal treatments on the visual and dynamic viscosity, in association to IgG concentration, of colostrum that can be used for pasteurization process. Results Of the total 40 fresh postpartum colostrum, the color of colostrum (ranging from white-pale yellow to yellow and dark-yellowish), fat (1.4–8.2 100 g −1 ), IgG (4–116 mg mL −1 ), %Brix (8.5–35.4%), refractive index (1.3454–1.3905 nD), visual (ranging from watery to liquid and thick) and dynamic (4.9–219 cp) viscosity, were recorded. Statistical analysis between visual and dynamic viscosity of fresh colostrum showed significant correlation coefficients ( r s  = 634). Moreover, a significant correlation between viscosity and three IgG concentrations was also observed. Heat-treated colostrum showed dynamic viscosity ranged from 25 to 3066 cP, where dynamic viscosity of colostrum before- and after heat-treatment showed no significant correlation. Treated colostrum at 60 °C/60 min and 63.5 °C/30 min containing IgG concentration ≤ 80 mg mL −1 and ≤ 68 mg mL −1 showed no significant change in the viscosity and can successfully be applied for pasteurization of first postpartum colostrum.

The objective of this work was to investigate the evaluation of swine colostrum immunoglobulin G (IgG) concentration using the Brix refractometer. Colostrum samples were collected across all teats, from 124 sows of mixed parities. According to sampling time, three categories were created: samples available from 9 h before the onset of parturition until the first piglet was born were classified as before farrowing; samples collected after the first birth until 4 h later were classified as during farrowing; and finally samples collected from this point until 14 h after parturition, were classified as after farrowing. Samples were drawn and divided into three portions; one was immediately analyzed, a second was refrigerated and the third was frozen at −20°C. Fresh and refrigerated colostrum samples were analyzed at the farm with a Brix refractometer. IgG content of frozen samples was analyzed using a Brix refractometer, with a subset of 42 samples also tested with a commercially available radial immune diffusion (RID) kit. The Brix percentage ranged from 18.3% to 33.2%. Brix percentage repeatability, assessed by the intraclass correlation coefficient (ICC), was very strong (fresh ICC=0.98, refrigerated ICC=0.88 and frozen ICC=0.99). One-way repeated-measures ANOVA showed that storage temperature did not affect BRIX percentage of colostrum IgG (P>0.05). ANOVA results show a significant effect of sampling time on colostrum immunoglobulin concentration, measured with both Brix and RID (Brix: P<0.003; RID: P<0.05). Immunoglobulin G concentration measured by RID ranged from 13.27 to 35.08 mg/ml. Pearson correlation coefficient revealed that Brix percentage was positively correlated (r=0.56, P<0.001) with RID results (regression equation: RID=1.01 (±0.2) Brix −1.94 (±5.66); R 2=0.31). The results of this study indicate that the Brix refractometer provides a simple, fast and inexpensive estimation of colostrum IgG in sows.

The objectives of this study were to determine the immunoglobulin G concentration of colostrum in Czech dairy cows, to compare refractometer results with results achieved using the radial immunodiffusion method and to evaluate the reliability of three types of refractometers and recommend the best solution for the evaluation of colostrum quality. Colostrum samples (n = 1522) were collected from 38 herds between 2015 and 2017. The immunological quality of colostrum was estimated using Brix refractometers (optical, simple digital, digital Misco) and compared with the immunoglobulin G concentration assessed using radial immunodiffusion. We found high variability in the quality of colostrum. The minimum, maximum and median of individual measurements were the following: radial immunodiffusion immunoglobulin G – 5.2, 199.1, 76.9 g/l; optical refractometer – 9.5, 32.0, 23.1% Brix; simple digital refractometer – 5.4, 35.0, 19.1% Brix; digital refractometer Misco – 9.8, 37.4, 23.2% Brix. On the basis of immunoglobulin G concentration assessed using radial immunodiffusion, 20.9% of colostrum samples were of low quality (immunoglobulin G < 50 g/l). The Spearman correlation coefficients between radial immunodiffusion and the Brix refractometer readings were 0.62–0.67 (P < 0.001) according to the type of refractometer. The cut-off evaluation of the readings from optical and Misco digital refractometers both showed 20% Brix, with sensitivities of 89.4% and 88.2%, specificities of 73.2% and 74.5% and accuracies of 86.0% and 85.4%, respectively. The cut-off level for the simple digital refractometer showed 17% Brix with a sensitivity of 77.5%, specificity of 80.4% and an insufficient accuracy of 78.1%. For optical and Misco refractometers we recommend the use of two cut-off levels for the evaluation of colostrum: 23% Brix for the selection of good quality colostrum suitable for freezing and 19% Brix to discard poor quality colostrum. The different cut-off levels obtained by measuring with different types of refractometers indicate the need to check the quality of the instruments prior to their use in practice and, where appropriate, to determine their cut-off levels by comparison with results obtained using the reference method.

Failure of passive transfer (FPT) of immunoglobulins (IgG) is associated with increased morbidity and mortality of calves. In this study we evaluated the digital Brix refractometer usefulness for the assessment of FPT. A number of 16 colostrum samples from the first milking (2-3h post-partum) of Holstein-Friesian dairy heifers and 29 blood sera of 3-6 days old calves were analyzed with a digital Brix refractometer. Total proteins were determined by the biuret reaction. Colostral IgG were determined by radial immunodiffusion (RID), and colostral whey and blood serum γ globulin (composed almost entirely of IgG) were determined by agarose protein gel electrophoresis (APE) and densitometry. Colostral % Brix score was 25.5±3.4%. Concentrations of colostrum IgG and colostral whey γ globulin were 130±33 g/L and 100±24 g/L respectively. The concentration of total proteins in colostral whey was 134±30 g/L. The correlations between Brix values and the concentrations of IgG determined with RID and the concentrations of γ globulin determined with APE were positive and highly significant (P<0.001 and P<0.01). The concentration of serum proteins of new-born calves was 57.75±11.8 g/L, the concentration of γ globulin was 14.4±7.8 g/L, and the Brix score was 8.6±1.0%. FPT (serum γ globulin<10 g/L) was detected in 34.5% (10/29) calves. Brix score correlated with the concentration of blood serum γ globulins in all examined calves. The results have confirmed that digital Brix refractometry allows the producers to use this technique in order to estimate colostral and calf serum IgG, thereby monitoring both colostrum quality and success of passive transfer.

The evaluation of mare colostrum immediately after foaling and prior to nursing can be helpful in predicting if adequate passive transfer or failure of passive transfer is likely to occur. This is especially important in situations in which colostrum has been lost due to premature leakage from the mammary gland. The evaluation of colostrum is also valuable in determining the quality of colostrum to be harvested and stored in a colostrum bank. Quantitative measurement of IgG levels in colostrum can be obtained by a radial immunodiffusion (RID) assay at a diagnostic laboratory. Qualitative assessment of colostrum can be performed using a sugar (Brix) refractometer, which measures the concentration of dissolved solids in a solution. This chapter discusses step by step procedure for performing the evaluation of colostrum using Brix refractometer. It also discusses necessary conditions for evaluation of colostrum using Brix refractometer.

Background Refractometry is used to assess transfer of passive immunity (TPI), but studies evaluating different refractometers and appropriate thresholds for recommended target immunoglobulin G (IgG) concentrations for beef calves are limited. Objectives To evaluate test performance of digital (DSTP) and optical (OSTP) serum total protein (STP) refractometers and a digital Brix (DBRIX) refractometer for assessment of passive immunity in beef calves. Animals A total of 398 beef calves from 6 herds, 1 to 7 days of age. Methods Serum IgG concentration was estimated by DSTP, OSTP, and DBRIX, and measured by radial immunodiffusion (RID). Correlation coefficients (r) among results were calculated. Optimal STP and Brix thresholds for identification of IgG <10, <16, and <24 g/L were determined using interval likelihood ratios. Refractometer performance and agreement were assessed using areas under the curve (AUC), diagnostic test characteristics, Cohen's kappa (κ), and Bland‐Altman analysis. Results Refractometer results were highly correlated with RID (r = 0.82‐0.91) and with each other (r = 0.91‐0.95), and overall test performance was excellent (AUC = 0.93‐0.99). The STP concentrations of ≤5.1, ≤5.1, and ≤5.7 g/dL and Brix percentages of ≤7.9%, ≤8.3%, and ≤8.7% indicated IgG concentrations <10, <16, and <24 g/L, respectively. Agreement of refractometers with RID was variable (κ = 0.46‐0.80) and among refractometers was substantial (κ = 0.62‐0.89). Conclusions and Clinical Importance All refractometers showed good utility as monitoring tools for assessment of TPI in beef calves.