On-Farm Application of the Brix Refractometer for Estimating Sow Colostrum Immunoglobulin G in Commercial Pig Herds

The Brix refractometer is a commonly used instrument for measuring the soluble solid content of a liquid and is traditionally applied to estimate sugar concentration based on refractive index. However, Brix values also reflect other components, including proteins such as immunoglobulin G (IgG). In livestock production, the Brix refractometer is widely used as a practical tool for assessing colostrum quality. This study aimed to evaluate the use of a Brix refractometer for on-farm prediction of sow colostrum IgG concentrations in a commercial pig herd, using enzymelinked immunosorbent assay (ELISA) as the reference method. Data on Brix values (%) and IgG concentrations (mg/ml) were obtained from 105 colostrum samples collected from French Landrace × Yorkshire sows (average parity 3.1 ± 2.1). Colostrum samples (5 ml) were manually collected within 3 h after the birth of the first piglet in the litter. The Brix value was measured immediately using a Brix refractometer and the remaining samples were stored in clean bottles at −20 °C until IgG analysis. Spearman correlation analysis was performed to examine the association between Brix values and colostrum IgG concentrations. On average, the Brix value was 28.0 ± 3.4 % (range: 20.2–39.7 %), and IgG concentration was 47.7 ± 11.6 mg/ml (range: 20.5–78.9 mg/ml). A significant positive correlation was observed between Brix value and IgG concentration (r = 0.637, p < 0.001, n = 105). These findings suggest that Brix values can serve as a reliable proxy for colostrum quality in commercial pig herds.