Explore the vast range of titles available.

Abstract Background Transfer of passive immunity in calves can be assessed by direct measurement of immunoglobulin G (IgG) by methods such as radial immunodiffusion (RID) or turbidimetric immunoassay (TIA). IgG can also be measured indirectly by methods such as serum refractometry (REF) or Brix refractometry (BRIX). Objectives To determine the accuracy of REF and BRIX for assessment of inadequate transfer of passive immunity (ITPI) in calves. Design Systematic review and meta-analysis of diagnostic accuracy studies. Methods Databases (PubMed and CAB Abstract, Searchable Proceedings of Animal Science) and Google Scholar were searched for relevant studies. Studies were eligible if the accuracy (sensitivity and specificity) of REF or BRIX was determined using direct measurement of IgG by RID or turbidimetry as the reference standard. The study population included calves <14 days old that were fed with natural colostrum (colostrum replacement products were excluded). Quality assessment was performed by the QUADAS-2 tool. Hierarchical models were used for meta-analysis. Results From 1,291 references identified, 13 studies of 3,788 calves were included. Of these, 11 studies evaluated REF and 5 studies evaluated BRIX. The median (range) prevalence of ITPI (defined as calves with IgG <10 g/L by RID or TIA) was 21% (1.3–56%). Risk of bias and applicability concerns were generally low or unclear. For REF, summary estimates were obtained for 2 different cutoffs: 5.2 g/dL (6 studies) and 5.5 g/dL (5 studies). For the 5.2 g/dL cutoff, the summary sensitivity (95% CI) and specificity (95% CI) were 76.1% (63.8–85.2%) and 89.3% (82.3–93.7%), and 88.2% (80.2–93.3%) and 77.9% (74.5–81.0%) for the 5.5 g/dL cutoff. Due to the low number of studies using the same cutoffs, summary estimates could not be obtained for BRIX. Conclusions and Clinical Importance Despite their widespread use on dairy farms, evidence about the optimal strategy for using refractometry, including the optimal cutoff, are sparse (especially for BRIX). When using REF to rule out ITPI in herds, the 5.5 g/dL cutoff may be used whereas for ruling in ITPI, the 5.2 g/dL cutoff may be used.

Abstract 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.

Calves are born agammaglobulinemic and depend on transfer of passive immunity from colostrum. Failure of transfer of passive immunity (FTPI) and adequate transfer of passive immunity (ATPI) are defined as serum immunoglobulin G (IgG) levels < 10 and ≥ 10 mg/mL, respectively. The objective of this study was to evaluate the level of passively transferred immunity in Danish dairy calves measured with Enzyme-linked immunosorbent assay (ELISA) and Brix refractometer. Blood samples from 834 calves (430 bull calves and 404 heifer calves) aged two to nine days were included in the study. Serum IgG concentration was determined by ELISA and percentage Brix (%Brix) with a digital refractometer. Median serum IgG concentration was 17.05 mg/mL and mean %Brix was 8.5%. A total of 592 (71.0%) and 242 samples (29.0%) had a serum IgG concentration ≥ 10 mg/mL and < 10 mg/mL, respectively. For %Brix 541 (64.9%) and 293 (35.1%) was ≥ 8.1 and < 8.1%, respectively. Serum IgG concentrations and %Brix measurements were highly correlated ( r  = 0.88). The level of passive immunity in Danish dairy calves seems low and does not meet new recommendations. However, applying cut-offs based on radial immunodiffusion to serum IgG concentrations derived from ELISA are not straightforward and determination of new cut-off values for FTPI based on ELISA are recommended.

This study was aimed at the assessment of the reliability and performance of the Brix refractometer for the determination of colostral IgG concentrations in sheep. A total of 190 colostrum samples were collected from 150 ewes of various breeds. Out of the colostrum samples, 101 were taken at parturition, 10 at 6 h postpartum, 6 at 8 h postpartum, 2 at 10 h postpartum, 65 at 12 h postpartum and 6 at 24 h postpartum. The Brix percentages of the colostrum samples were determined using a Brix refractometer, and the colostral IgG concentrations were measured with the radial immunodiffusion (RID) technique. Correlation coefficients were calculated between the Brix percentages and RID‐IgG values. Receiver operating characteristics (ROC) analyses were performed to determine the optimal Brix thresholds for the prediction of colostral IgG concentrations using <20, <50, <75 and <100 g/L thresholds. The misclassification cost term (MCT) analyses were performed to test the robustness of the Brix thresholds based on the relative costs of misclassifications. The mean IgG concentration and Brix percentage of the ewe colostrum samples were determined as 62.7 g/L and 27.2%, respectively. A high correlation was detected between the colostral RID‐IgG concentrations and Brix percentages (r = 0.83). Brix percentages of ≤25.0%, ≤25.9%, ≤27.5% and ≤31.9% indicated IgG concentrations of <20, <50, <75 and <100 g/L, respectively. The Brix refractometer was demonstrated to be a low‐cost, practical and reliable tool for the determination of colostrum quality in sheep. It is recommended that the four Brix thresholds determined in this study be used strategically in feeding lambs in need of colostral supplementation due to inadequate or poor‐quality colostrum production by their dams.

Hardly published data are available to diagnose the failure of transfer of passive immunity (FTPI) in calves affected by neonatal calf diarrhea (NCD). This study evaluated the diagnostic performance and differences among optical serum total protein (STP) concentration and gamma-glutamyl-transferase (GGT) activity for assessing FTPI in diarrheic Holstein Friesian calves. 72 diarrheic and 19 healthy Holstein Friesian calves aged 1 to 10 days were enrolled. Each calf underwent a complete clinical examination and dehydration assessment. The effect of dehydration status and age on the correlation between the two methods under study (STP and GGT) and the gold standard (Immunoglobulin G [IgG] measured with RID) was investigated with Spearman’s correlation index R for ranks. Serum total protein concentration and GGT activity were analyzed by receiver operating characteristic (ROC) curve analysis to identify the optimal cut-off point to distinguish between diarrheic calves with or without FTPI, also considering the effects of dehydration and age. The results show that GGT activity was affected by the age of calves, while STP was influenced by dehydration. The cut-offs to distinguish calves with IgG < 10 g/L were < 52 g/L of STP in normohydrated calves, < 58 g/L of STP in dehydrated calves, and < 124 IU/L of GGT in calves with aged between 3 and 10 days. In nondehydrated diarrheic calves, the STP refractometer showed better diagnostic accuracy.In dehydrated calves aged between 3 and 10 days, however, its accuracy drops, and it is advisable to use GGT activity.

In this Research Communication we assessed factors affecting colostrum quality of dairy Lacaune ewes using the Brix-refractometer. Colostrum from 536 lambings from one commercial intensive dairy Lacaune farm were analysed for the following factors with potential influence in colostrum quality: (1) ewe parity (n = 84–132), (2) length of previous dry period (PDP) (n = 23–214), (3) age at first lambing (AFL) of primiparous ewes (n = 9–88), (4) lambing season (n = 192 or 344), and (5) year (2011–2013, n = 142–203). Parity significantly affected colostrum quality, with primiparous ewes showing the highest Brix refractometer values (22·6 ± 5·6%, P < 0·0001), though values were similar among multiparous ewes. PDP length also significantly affected colostrum quality: ewes with the shortest PDP showed the worst quality (16·8 ± 4·2%, P < 0·0001), with quality gradually rising with PDP length. Colostrum quality was significantly higher in 2011 (21·0 ± 5·2%) than in 2012 or 2013 (P < 0·0001); this likely reflects the several-fold greater proportion of animals with long PDP in 2011. In contrast, neither AFL nor lambing season significantly affected colostrum quality. These results suggest that parity and PDP length can substantially affect ovine colostrum quality of dairy ewes under intensive management conditions and they further show the usefulness of the Brix refractometer for providing a rough estimation of colostrum quality on-farm. However, further studies are needed to determine a validated cut-off Brix value for identifying good-quality colostra in ovine species.

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.

Abstract Background Urine specific gravity (USG) is an integral part of the urinalysis and a key component of many clinical decisions, and fluctuations in USG have the potential to impact case management. Objectives To determine the intraindividual variability of first morning USG results in healthy dogs. Animals One hundred three healthy client-owned dogs. Methods Dogs were deemed healthy based on clinical history and physical examination findings. Repeated USG measurements were performed over the course of 2 weeks. Three urine samples were collected each week for a total of 6 samples per dog. Sample collection was distributed evenly throughout the week. Urine samples were acquired immediately upon waking and before any ingestion of liquids, food, or exertion of physical activity in the dogs. All measurements were made using the same Misco digital refractometer. Results Intraindividual USG was variable over the course of the study. The mean difference between the minimum and maximum USG for each dog was 0.015 (SD, 0.007). The within-week difference between the minimum and maximum USG was less than over the complete 2-week study (0.009 [SD 0.006] for week 1 and 0.010 [SD 0.007] for week 2). The mean coefficient of variance across all 6 time points was 15.4% (SD 8.97%). Conclusions and Clinical Importance Clinically important variation occurs in USG in healthy animals and might impact clinical decision-making when diagnostic cutoff points are utilized. Clinicians should be aware of inherent variability in this clinical variable when analyzing results.

Background There is an increased interest in using digital refractometers to indirectly assess colostrum quality of dairy cattle, but knowledge on diagnostic accuracy for Norwegian Red dairy cows is lacking. Recent research has indicated a profound variability in the colostrum quality among dairy cows and herds in Norway. The aim of this study was to evaluate the diagnostic test sensitivity and specificity of a digital refractometer (Brix refractometer) at different cut-offs in Brix% for detection of colostrum of high quality (> 50 g/L) defined by the gold standard single radial immunodiffusion (IgG g/L). Furthermore, we aimed to identify possible associations between selected herd and cow-level management factors and colostrum IgG-levels in Norwegian Red dairy cows. Results Median colostrum IgG level across 167 cows from 19 herds was 35.0 g/L, ranging from 5 to 129 g/L. Mean Brix% (± SD) was 19.7 ± 4.12%, ranging from 10.1 to 30.5. Most samples (72.5%) had inferior quality as compared to the international standard of 50 g/L. Brix% and IgG in colostrum were strongly correlated (r = 0.71, P < 0.001). A Brix cut-off of 22%, which is currently recommended, yielded a sensitivity of (95% CI) 69.4% (54.6–81.7) and a specificity of 83.1% (75.0–89.3) for identifying colostrum with high quality (> 50 g/L). The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with low quality compared to cows in parities four and later. Conclusions The agreement between colostrum IgG and Brix% is good. However, the diagnostic test evaluation indicates suboptimal performance in identifying high vs. low colostrum quality in this population, possibly related to a high proportion of the samples with < 50 g/L IgG. The only factor found to be associated with low colostrum quality was parity. Specifically, cows in the second parity were found to produce colostrum with lower quality. Future research should investigate colostrum and serum IgG levels which best prevent calf illness under Norwegian conditions.