ASSESSMENT OF THE QUALITY AND YIELD OF COW COLOSTRUM OBTAINED IN THE FIRST 24 HOURS AFTER CALVING

<b>The aim of the study was to assess the quality of colostrum of Polish Holstein-Friesian cows on the first day after calving, by measuring the refractive index on the Brix scale with an electronic refractometer, as well as the colostrum yield. The influence of the following factors on these colostrum characteristics was analysed: time after calving, herd, lactation number, and length of the dry period before parturition. In total, colostrum from 21 cows (7 from each herd) was assessed. Yield was assessed, and antibody content on the Brix scale was determined using an electronic refractometer up to 2 hours after calving and at the time of subsequent milking on the farms (between 3 and 12 hours and between 13 and 24 hours after calving). Time after calving was shown to significantly affect the quality and yield of colostrum (P < 0.05). The immunological value of colostrum assessed on the Brix scale decreased at successive milking times after calving, amounting to 22.7%, 19.2% and 16.4%. However, the average colostrum yield increased with time (from an average of 6.5 kg in the first colostrum collection to 9.4 kg in the period between 13 and 24 hours after calving). The length of the dry period and the age of the cow were particularly important factors for the high value of the first colostrum. The best colostrum was produced by cows with a longer dry period, lasting from 46 to 59 days (23.4% Brix) and by older cows in lactations from 4 to 7 (24.2% Brix). The correlation and regression coefficients calculated in the study indicate that the increase in the yield of colostrum obtained up to 2 hours after calving is associated with a decrease in its quality. Extension of the dry period before parturition is accompanied by an increase in antibody content assessed on the Brix scale. Despite the fact that routine assessment of colostrum quality using an electronic refractometer is known to have tangible benefits, it is still not widely conducted.