Hamer, K., Bellingham, M. , Evans, N. P. , Jones, R. O. and Denholm, K. S. (2023) Defining optimal thresholds for digital Brix refractometry to determine IgG concentration in ewe colostrum and lamb serum in Scottish lowland sheep flocks. Preventive Veterinary Medicine, 218, 105988. (doi: 10.1016/j.prevetmed.2023.105988)
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Abstract
This research aimed to define thresholds for ewe colostrum and lamb serum Brix refractometer measurements in lowland Scottish sheep. This would facilitate the use of this convenient, sheep-side test, enabling quick and accurate identification of poor quality colostrum and prevention of failure of transfer of passive immunity (FTPI) in lambs. Secondary aims were to identify risk factors for poor colostrum quality and FTPI in lambs. Serum samples (n = 233) were collected from lambs between 24 and 48hrs after birth, from four lowland Scottish meat sheep farms. Pre-suckle colostrum samples (n = 112) were also collected from ewes on two of these farms. Farmers provided information on litter size, ewe body condition score, ewe breed and dystocia. Duplicate digital Brix refractometer measurements were compared with immunoglobulin G (IgG) radial immunodiffusion (RID) testing for all colostrum and serum samples. Receiver operating characteristic (ROC) curves were used to redefine thresholds for Brix testing in colostrum and serum. Linear regression models were constructed with colostrum and serum IgG concentration as the outcomes of interest. Colostrum and serum IgG concentrations were highly variable. The prevalence of inadequate colostrum quality (using <50 g/L IgG on RID) was 4.5% (95% CI = 1.5 – 10.1) and the prevalence of FTPI (using <15 g/L IgG in serum on RID) was 7.73% (95% CI = 4.64–11.93). A ewe’s colostrum IgG concentration was significantly and positively associated with the serum IgG concentration of her lamb(s) (p = 0.02). ROC analysis defined a Brix threshold for adequate colostrum quality of > 22.10% (sensitivity 80% (95%CI=28.4–99.5), specificity 90% (95%CI=82.3–94.8)). ROC analysis defined a Brix threshold for serum of > 8.65% for adequate passive transfer of immunity in Scottish lambs (sensitivity 94% (95%CI=72.7–99.8), specificity 82% (95%CI=76.6–87.2)). To optimise passive transfer of immunity in lambs, we suggest that ewe colostrum Brix measurements be defined as ‘poor’ (<22%); ‘fair’ (22–26%) and ‘good’ (>26%); and lamb serum as ‘poor’ (<8%); ‘fair’ (8–9%) and ‘good’ (>9%). It is recommended that these tests are used as for flock screening, using samples from multiple animals.
| Item Type: | Articles |
|---|---|
| Additional Information: | This work was supported, with financial support only, by MSD Animal Health Ltd [Ruminant Bursary] and the National Institute of Health [grant number R01 ES030374/ES/NIEHS NIH HHS/United States]. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Hamer, Miss Kim and Bellingham, Dr Michelle and Denholm, Mrs Katie and Evans, Professor Neil and Jones, Rheinallt |
| Authors: | Hamer, K., Bellingham, M., Evans, N. P., Jones, R. O., and Denholm, K. S. |
| College/School: | College of Medical Veterinary and Life Sciences College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine |
| Journal Name: | Preventive Veterinary Medicine |
| Publisher: | Elsevier |
| ISSN: | 0167-5877 |
| ISSN (Online): | 1873-1716 |
| Published Online: | 01 August 2023 |
| Copyright Holders: | Copyright © 2023 The Authors |
| First Published: | First published in Preventive Veterinary Medicine 218:105988 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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