Passive immunity transfer in dairy calves fed with raw colostrum

Abstract

The objective of this study was to evaluate the efficiency of passive immunity transfer (PIT) in Girolando dairy calves, as well as to identify possible failures in colostrum management in the Dairy Cattle Sector of the Glória Experimental Farm, at the Federal University of Uberlândia. From November 2023 to October 2024, 77 calves (30 males and 47 females) from predominantly multiparous cows were evaluated. The variables analyzed included birth weight, colostrum quality measured via Brix, volume provided in the first suckling, Brix and total whey protein, average daily gain (ADG), and days on lactation. Colostrum was evaluated using an optical refractometer. Serum samples were obtained 24 hours after colostrum feeding and analyzed to determine Brix (%) and total protein (g/dL). The average Brix level was 24.8% ± 3.05, ranging from 15 to 30%, indicating good, albeit heterogeneous, quality. Average concentrations of total soluble solids, determined via Brix, were significantly higher in females (9.62 ± 1.36%) compared to males (7.45 ± 1.09%). Similarly, average serum total protein values ​​were also higher in females (9.46 ± 1.50 g/dL) compared to males (7.26 ± 1.26 g/dL). Most animals presented a PIT classified as excellent, totaling 89.36% of females and 73.33% of males. ADG was 0.85 ± 0.16 kg/day for females and 0.71 ± 0.15 kg/day for males. The observed mortality rate was 10%, with diarrhea and bovine respiratory disease as the main causes. Colostrum BRIX cor-related positively with serum BRIX and total protein, confirming its usefulness as a practical indicator of colostrum quality and success in PIT. It is concluded that, although the results indicate good efficiency in PIT, neonatal mortality is still above the ideal, suggesting a need for improvements in hygienic-sanitary management and in the calf rearing environment.