Validation of a handheld refractometer to assess Merino ewe colostrum and transition milk quality.

Autor:	Agenbag B; School of Animal and Veterinary Sciences, Davies Livestock Research Centre, University of Adelaide, Roseworthy Campus, Roseworthy, South Australia, Australia 5371. Electronic address: bianca.agenbag@adelaide.edu.au., Swinbourne AM; School of Animal and Veterinary Sciences, Davies Livestock Research Centre, University of Adelaide, Roseworthy Campus, Roseworthy, South Australia, Australia 5371; South Australian Research and Development Institute, Livestock Sciences, Turretfield Research Centre, 129 Holland Rd, Rosedale, South Australia, Australia 5350., Petrovski K; School of Animal and Veterinary Sciences, Davies Livestock Research Centre, University of Adelaide, Roseworthy Campus, Roseworthy, South Australia, Australia 5371., van Wettere WHEJ; School of Animal and Veterinary Sciences, Davies Livestock Research Centre, University of Adelaide, Roseworthy Campus, Roseworthy, South Australia, Australia 5371.
Jazyk:	angličtina
Zdroj:	Journal of dairy science [J Dairy Sci] 2023 Feb; Vol. 106 (2), pp. 1394-1402. Date of Electronic Publication: 2022 Nov 29.
DOI:	10.3168/jds.2022-22022
Abstrakt:	Colostrum quality is generally defined by the IgG concentration in colostrum, and many methods have been used to assess it. Methods to measure colostrum quality both in the laboratory and in the field have been validated in cattle; however, this is only a recent topic of interest for sheep colostrum. Laboratory-based methods are often time consuming and require trained personnel compared with new handheld evaluation tools such as the digital Brix refractometer, which gives real-time results. The aims of this study were to (1) evaluate the relationship between the digital Brix refractometer and constituents indicative of quality (IgG, protein, fat, and lactose) in colostrum and transition milk, and (2) determine an appropriate Brix % cut-off value for the Brix refractometer in sheep colostrum and transition milk. The study used 50 colostrum samples (collected at 0 h postpartum, before lambs' sucking) and 169 transitional milk samples (collected at 4 and 24 h postpartum, after lambs had sucked) collected over 6 lambing trials in 2 years (2019 and 2020). We concluded that the Brix refractometer results correlated weakly with IgG concentration determined by radial immunodiffusion assay in colostrum collected at 0 h postpartum (r = 0.11) and in transition milk collected at 4 h postpartum (r = 0.12); however, a moderate to strong correlation was shown in transition milk samples collected at 24 h (r = 0.66). Brix % was significantly correlated with fat %, lactose %, and protein % at all timepoints. To determine an appropriate Brix % cut-off value indicating an IgG concentration of 20 mg/mL, we analyzed sensitivity and specificity of the Brix refractometer at 0, 4, and 24 h. In samples collected at 0 and 4 h, the highest combination of sensitivity, specificity, and accuracy was achieved at a Brix % cut-off value of 29%; in samples collected at 24 h postpartum, a Brix % cut-off value of 27% gave the highest sensitivity, specificity, and accuracy. Overall, the Brix refractometer has potential as a useful in-field tool for researchers and producers in both extensively and intensively managed flocks to measure and determine the quality of sheep colostrum and transition milk. (The Authors. Published by Elsevier Inc. and Fass Inc. on behalf of the American Dairy Science Association®. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).)
Databáze:	MEDLINE
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