{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T09:07:23Z","timestamp":1790068043653,"version":"4.0.1"},"reference-count":34,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001871","name":"FCT\u2014Foundation for Science and Technology","doi-asserted-by":"publisher","award":["CECAV UIDB\/00772\/2020"],"award-info":[{"award-number":["CECAV UIDB\/00772\/2020"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"FCT\u2014Foundation for Science and Technology","doi-asserted-by":"publisher","award":["MED UIDB\/05183\/2025"],"award-info":[{"award-number":["MED UIDB\/05183\/2025"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001871","name":"FCT\u2014Foundation for Science and Technology","doi-asserted-by":"publisher","award":["UI\/BD\/150834\/2021"],"award-info":[{"award-number":["UI\/BD\/150834\/2021"]}],"id":[{"id":"10.13039\/501100001871","id-type":"DOI","asserted-by":"publisher"}]},{"award":["CECAV UIDB\/00772\/2020"],"award-info":[{"award-number":["CECAV UIDB\/00772\/2020"]}],"id":[{"id":"https:\/\/ror.org\/00snfqn58","id-type":"ROR","asserted-by":"publisher"}]},{"award":["MED UIDB\/05183\/2025"],"award-info":[{"award-number":["MED UIDB\/05183\/2025"]}],"id":[{"id":"https:\/\/ror.org\/00snfqn58","id-type":"ROR","asserted-by":"publisher"}]},{"award":["UI\/BD\/150834\/2021"],"award-info":[{"award-number":["UI\/BD\/150834\/2021"]}],"id":[{"id":"https:\/\/ror.org\/00snfqn58","id-type":"ROR","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>This study investigated the relationship between Brix values and the nutritional and immunological composition of bovine colostrum. Colostrum samples (n = 82) were collected from Holstein-Friesian cows on four dairy farms. Dry matter (DM), solids non-fat (SNF), crude protein (CP), fat, IgG concentrations, and Brix values were determined. Correlation, regression, and receiver operating characteristic (ROC) analyses were used to evaluate associations among variables and identify a Brix cut-off for high-quality colostrum (IgG \u2265 50 g\/L). Brix was positively associated with both CP (\u03c1 = 0.90) and IgG concentration (\u03c1 = 0.75), although the relationship between Brix and IgG was significantly influenced by the IgG\/CP ratio. A robust regression model including SNF and fat provided the best prediction of Brix values (R2 = 0.98). ROC analysis identified a Brix cut-off of approximately 25%, which detected high-quality colostrum with 83% sensitivity and 76% specificity. Colostrum above this threshold had higher DM, SNF, CP, and IgG concentrations, but not fat concentration. These findings suggest that Brix values primarily reflect the soluble solids fraction of colostrum and that variation in the proportion of IgG within total protein may contribute to the variability in Brix\u2013IgG relationships and threshold values reported among studies.<\/jats:p>","DOI":"10.3390\/ani16192979","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T08:17:54Z","timestamp":1790065074000},"page":"2979","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["The IgG-to-Protein Ratio Influences the Relationship Between Brix Values and Immunoglobulin G Concentration in Bovine Colostrum"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-4218-498X","authenticated-orcid":false,"given":"Fl\u00e1vio G.","family":"Silva","sequence":"first","affiliation":[{"name":"MED-Mediterranean Institute for Agriculture, Environment and Development & CHANGE-Global Change and Sustainability Institute, University of \u00c9vora, P\u00f3lo da Mitra, Ap. 94, 7006-554 \u00c9vora, Portugal"},{"name":"Veterinary and Animal Research Centre & Al4AnimalS, Department of Animal Science, Quinta de Prados, University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Center for Research and Development in Agrifood Systems and Sustainability, Polytechnic Institute of Viana do Castelo, Agrarian School of Ponte de Lima, Rua D. Mendo Afonso, 147 Ref\u00f3ios do Lima, 4990-706 Ponte de Lima, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"conceptualization","vocabulary":"credit"},{"role":"methodology","vocabulary":"credit"},{"role":"software","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9735-2162","authenticated-orcid":false,"given":"Marta","family":"Gonz\u00e1lez-Cabrera","sequence":"additional","affiliation":[{"name":"IUSA-ONEHEALTH 4, Animal Production and Biotechnology Group, Institute of Animal Health and Food Safety, Universidad de Las Palmas de Gran Canaria, Campus Monta\u00f1a Cardones, s\/n, 35413 Arucas, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2729-0434","authenticated-orcid":false,"given":"Lorenzo E.","family":"Hern\u00e1ndez-Castellano","sequence":"additional","affiliation":[{"name":"IUSA-ONEHEALTH 4, Animal Production and Biotechnology Group, Institute of Animal Health and Food Safety, Universidad de Las Palmas de Gran Canaria, Campus Monta\u00f1a Cardones, s\/n, 35413 Arucas, Spain"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"given":"Rute","family":"Sobral","sequence":"additional","affiliation":[{"name":"MED-Mediterranean Institute for Agriculture, Environment and Development & CHANGE-Global Change and Sustainability Institute, University of \u00c9vora, P\u00f3lo da Mitra, Ap. 94, 7006-554 \u00c9vora, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"writing-original-draft","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7968-7826","authenticated-orcid":false,"given":"Ana","family":"Geraldo","sequence":"additional","affiliation":[{"name":"MED-Mediterranean Institute for Agriculture, Environment and Development & CHANGE-Global Change and Sustainability Institute, University of \u00c9vora, P\u00f3lo da Mitra, Ap. 94, 7006-554 \u00c9vora, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"visualization","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7045-2075","authenticated-orcid":false,"given":"Severiano R.","family":"Silva","sequence":"additional","affiliation":[{"name":"Veterinary and Animal Research Centre & Al4AnimalS, Department of Animal Science, Quinta de Prados, University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"resources","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"},{"role":"funding-acquisition","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0022-2749","authenticated-orcid":false,"given":"Joaquim L.","family":"Cerqueira","sequence":"additional","affiliation":[{"name":"Veterinary and Animal Research Centre & Al4AnimalS, Department of Animal Science, Quinta de Prados, University of Tr\u00e1s-os-Montes e Alto Douro, 5000-801 Vila Real, Portugal"},{"name":"Center for Research and Development in Agrifood Systems and Sustainability, Polytechnic Institute of Viana do Castelo, Agrarian School of Ponte de Lima, Rua D. Mendo Afonso, 147 Ref\u00f3ios do Lima, 4990-706 Ponte de Lima, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"validation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-4118-3283","authenticated-orcid":false,"given":"Cristina","family":"Concei\u00e7\u00e3o","sequence":"additional","affiliation":[{"name":"MED-Mediterranean Institute for Agriculture, Environment and Development & CHANGE-Global Change and Sustainability Institute, University of \u00c9vora, P\u00f3lo da Mitra, Ap. 94, 7006-554 \u00c9vora, Portugal"}],"role":[{"vocabulary":"crossref","role":"author"},{"role":"methodology","vocabulary":"credit"},{"role":"validation","vocabulary":"credit"},{"role":"formal-analysis","vocabulary":"credit"},{"role":"investigation","vocabulary":"credit"},{"role":"resources","vocabulary":"credit"},{"role":"data-curation","vocabulary":"credit"},{"role":"writing-review-editing","vocabulary":"credit"},{"role":"supervision","vocabulary":"credit"},{"role":"project-administration","vocabulary":"credit"}]}],"member":"1968","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"133","DOI":"10.1007\/s13594-015-0258-x","article-title":"Composition and Properties of Bovine Colostrum: A Review","volume":"96","author":"McGrath","year":"2016","journal-title":"Dairy Sci. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Silva, F.G., Silva, S.R., Pereira, A.M.F., Cerqueira, J.L., and Concei\u00e7\u00e3o, C. (2024). A Comprehensive Review of Bovine Colostrum Components and Selected Aspects Regarding Their Impact on Neonatal Calf Physiology. Animals, 14.","DOI":"10.3390\/ani14071130"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"4874","DOI":"10.3168\/jds.2022-22447","article-title":"Epidemiology of Bovine Colostrum Production in New York Holstein Herds: Cow, Management, and Environmental Factors","volume":"106","author":"Westhoff","year":"2022","journal-title":"J. Dairy Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"535","DOI":"10.1016\/j.cvfa.2019.07.005","article-title":"Colostrum Management for Dairy Calves","volume":"35","author":"Godden","year":"2019","journal-title":"Vet. Clin. N. Am.-Food Anim. Pract."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"4048","DOI":"10.3168\/jds.2015-9868","article-title":"Predicting Colostrum Quality from Performance in the Previous Lactation and Environmental Changes","volume":"99","author":"Cabral","year":"2016","journal-title":"J. Dairy Sci."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"1148","DOI":"10.3168\/jds.2012-5823","article-title":"Evaluation of the Brix Refractometer to Estimate Immunoglobulin G Concentration in Bovine Colostrum","volume":"96","author":"Quigley","year":"2013","journal-title":"J. Dairy Sci."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"100299","DOI":"10.1016\/j.animal.2021.100299","article-title":"Variation of Immunoglobulins G, A, and M and Bovine Serum Albumin Concentration in Holstein Cow Colostrum","volume":"15","author":"Costa","year":"2021","journal-title":"Animal"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"4084","DOI":"10.3168\/jds.2014-8491","article-title":"Technical Note: Comparison of Radial Immunodiffusion and ELISA for Quantification of Bovine Immunoglobulin G in Colostrum and Plasma","volume":"98","author":"Gelsinger","year":"2015","journal-title":"J. Dairy Sci."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"2438","DOI":"10.3168\/jds.2020-19020","article-title":"Short Communication: Comparative Estimation of Colostrum Quality by Brix Refractometry in Bovine, Caprine, and Ovine Colostrum","volume":"104","author":"Kessler","year":"2021","journal-title":"J. Dairy Sci."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"7453","DOI":"10.3168\/jds.2018-15645","article-title":"Short Communication: Effect of Barn Climate and Management-Related Factors on Bovine Colostrum Quality","volume":"102","author":"Zentrich","year":"2019","journal-title":"J. Dairy Sci."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"194","DOI":"10.1017\/S0022029921000340","article-title":"Predicting Colostrum and Calf Blood Components Based on Refractometry","volume":"88","author":"Hue","year":"2021","journal-title":"J. Dairy Res."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3713","DOI":"10.3168\/jds.2009-2943","article-title":"An Evaluation of Brix Refractometry Instruments for Measurement of Colostrum Quality in Dairy Cattle","volume":"93","author":"Bielmann","year":"2010","journal-title":"J. Dairy Sci."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"skac119","DOI":"10.1093\/jas\/skac119","article-title":"Letter to the Editor: Comments on Schalich et al. (2021), Colostrum Testing with Brix Is a Valuable on-Farm Tool. doi.org\/10.193\/jas\/skab083","volume":"100","author":"Lombard","year":"2022","journal-title":"J. Anim. Sci."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"skac120","DOI":"10.1093\/jas\/skac120","article-title":"Contradictions on Colostrum IgG Levels and Brix Values Are Real and Can Be Explained. Response to Letter by Lombard et al. (2022)","volume":"100","author":"Schalich","year":"2022","journal-title":"J. Anim. Sci."},{"key":"ref_15","unstructured":"(2002). Milk and Milk Products\u2014Determination of Nitrogen Content\u2014Routine Method Using Combustion According to the Dumas Principle (Standard No. ISO 14891:2002)."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"58","DOI":"10.1017\/S0022029915000734","article-title":"Covariance Structures of Fat and Protein Influence the Estimation of IgG in Bovine Colostrum","volume":"83","author":"Lokke","year":"2016","journal-title":"J. Dairy Res."},{"key":"ref_17","unstructured":"R Core Team (2025). R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"6261","DOI":"10.1080\/03610918.2016.1202271","article-title":"Robust Linear Regression: A Review and Comparison","volume":"46","author":"Yu","year":"2017","journal-title":"Commun. Stat.-Simul. Comput."},{"key":"ref_19","unstructured":"Maechler, M., Rousseeuw, P., Croux, C., Todorov, V., Ruckstuhl, A., Salibian-Barrera, M., Verbeke, T., Koller, M., Conceicao, E.L., and di Palma, M.A. (2026). Robustbase: Basic Robust Statistics R Package, R Foundation for Statistical Computing."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"3139","DOI":"10.21105\/joss.03139","article-title":"Performance: An R Package for Assessment, Comparison and Testing of Statistical Models","volume":"6","author":"Patil","year":"2021","journal-title":"J. Open Source Softw."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Robin, X., Turck, N., Hainard, A., Tiberti, N., Lisacek, F., Sanchez, J.-C., and M\u00fcller, M. (2011). PROC: An Open-Source Package for R and S+ to Analyze and Compare ROC Curves. BMC Bioinform., 12.","DOI":"10.1186\/1471-2105-12-77"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1878","DOI":"10.3168\/jds.2014-8415","article-title":"Evaluation of On-Farm Tools for Colostrum Quality Measurement","volume":"98","author":"Bartier","year":"2015","journal-title":"J. Dairy Sci."},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Jaywant, S.A., Singh, H., and Arif, K.M. (2022). Sensors and Instruments for Brix Measurement: A Review. Sensors, 22.","DOI":"10.3390\/s22062290"},{"key":"ref_24","first-page":"56","article-title":"Colostral Quality Determination by Simple Refractometry. A Preliminary Investigation","volume":"11","author":"Cash","year":"1995","journal-title":"Centaur"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"36","DOI":"10.1111\/j.2042-3292.1999.tb00916.x","article-title":"Colostral Quality Determined by Refractometry","volume":"11","author":"Cash","year":"1999","journal-title":"Equine Vet. Educ."},{"key":"ref_26","first-page":"206","article-title":"Field Determination of Colostrum Quality by Using a Novel, Practical Method","volume":"Volume 44","author":"Chavatte","year":"1998","journal-title":"Proceedings of the Annual Convention of the AAEP"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"761","DOI":"10.2460\/javma.233.5.761","article-title":"Comparison of Four Methods to Assess Colostral IgG Concentration in Dairy Cows","volume":"233","author":"Chigerwe","year":"2008","journal-title":"J. Am. Vet. Med. Assoc."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"skab083","DOI":"10.1093\/jas\/skab083","article-title":"Temporal Kinetics of Bovine Mammary IgG Secretion into Colostrum and Transition Milk","volume":"99","author":"Schalich","year":"2021","journal-title":"J. Anim. Sci."},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"595","DOI":"10.3168\/jds.2014-8730","article-title":"Validating a Refractometer to Evaluate Immunoglobulin G Concentration in Jersey Colostrum and the Effect of Multiple Freeze-Thaw Cycles on Evaluating Colostrum Quality","volume":"98","author":"Morrill","year":"2015","journal-title":"J. Dairy Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"356","DOI":"10.5398\/tasj.2021.44.3.356","article-title":"Comparison between the Brix Refractometer and ELISA for Assessment of Colostrum IgG of Montbeliard x Holstein Cross Dairy Cows","volume":"44","author":"Fahim","year":"2021","journal-title":"Trop. Anim. Sci. J."},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Sockett, D., Breuer, R.M., Smith, L.W., Keuler, N.S., and Earleywine, T. (2023). Investigation of Brix Refractometry for Estimating Bovine Colostrum Immunoglobulin G Concentration. Front. Vet. Sci., 10.","DOI":"10.3389\/fvets.2023.1240227"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"4838","DOI":"10.3168\/jds.2019-17949","article-title":"Comparison of Immunoglobulin G Absorption in Calves Fed Maternal Colostrum, a Commercial Whey-Based Colostrum Replacer, or Supplemented Maternal Colostrum","volume":"103","author":"Lopez","year":"2020","journal-title":"J. Dairy Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"636","DOI":"10.3168\/jds.2025-27097","article-title":"Optimal cutoff estimation and evaluation of direct and indirect diagnostic methods for assessing bovine colostrum quality with Bayesian finite mixture models","volume":"109","author":"Meletis","year":"2026","journal-title":"J. Dairy Sci."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"406","DOI":"10.3168\/jdsc.2024-0731","article-title":"Effect of frozen storage of bovine colostrum for up to 1 year on concentrations of immunoglobulins and insulin as well as bacterial counts","volume":"6","author":"Westhoff","year":"2025","journal-title":"JDS Commun."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/19\/2979\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T08:50:00Z","timestamp":1790067000000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/19\/2979"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,22]]},"references-count":34,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2026,10]]}},"alternative-id":["ani16192979"],"URL":"https:\/\/doi.org\/10.3390\/ani16192979","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,22]]}}}