Quality determination of fresh, refrigerated, frozen and refrozen goat colostrum using a digital BRIX refractometer

Abstract

Colostrum is the primary source of immunoglobulins, particularly IgG, for newborn goat kids. However, limited colostrum availability or poor-quality colostrum (i.e., low IgG concentration) forces farmers to store high-quality colostrum. Given the strong correlation between IgG concentration and BRIX degrees, optical and digital refractometers have been widely used to rapidly assess the quality of fresh colostrum. However, no information is available in the literature regarding this correlation in stored colostrum. This study aimed to evaluate the use of a digital refractometer for the rapid assessment of colostrum quality in fresh, refrigerated, frozen, and refrozen colostrum. The statistical analysis was performed using the software SAS 9.4 (SAS Institute, Cary, NC, USA). The variance and the normality of the residuals were graphically assessed using the PROC UNIVARIATE of SAS. The Pearson correlation coefficient was determined using the PROC CORR of SAS. These correlations were categorized according to Schober & Schwarte, (2018) as follows: negligible (r < 0.30); low (r = 0.30 to 0.49); moderate (r = 0.50 to 0.69); high (r = 0.70 to 0.89); or very high (r ≥ 0.90). Statistical significance was set as P ≤ 0.05. All the results are presented as Mean ± Deviation. The findings showed that IgG concentration remained unaffected by the storage method (P = 0.995). However, BRIX degrees tended to be influenced by the storage method (P = 0.086). A strong correlation between IgG concentration and BRIX degrees was observed in fresh colostrum (r = 0.80), whereas no significant correlation was found in refrigerated, frozen, or refrozen colostrum (r = 0.11, r = 0.33, r = 0.29, respectively). In conclusion, while a digital refractometer is an effective tool for assessing the quality of fresh colostrum, it is not reliable for evaluating colostrum stored under refrigeration or freezing conditions. These findings enhance the understanding of the chemical changes occurring in stored colostrum and set the path for future research in this field.