ABSTRACT: This study aimed to characterize the whey proteome of colostrum, transitional milk, and mature milk from Murciano-Granadina goats, and to evaluate the use of transitional milk as a substitute for colostrum in feeding neonatal kids. Proteomic analysis identified a total of 1,385 proteins, with 736 in colostrum, 668 in transitional milk, and 625 in mature milk. Colostrum and transitional milk displayed a high degree of similarity between colostrum and transitional milk, particularly in proteins related to immune response and inflammation. In contrast, mature milk showed a shift toward proteins involved in metabolic and transport functions. To evaluate the practical application of transitional milk, newborn goat kids were fed either frozen colostrum (following standard farm protocol), freeze-dried colostrum, or freeze-dried transitional milk. All feeding strategies were well tolerated, with no adverse health effects, and resulted in similar growth performance. At 48 hours of life, serum IgG concentrations were 13.95 mg/mL in kids fed frozen colostrum, 17.36 mg/mL in those fed freeze-dried colostrum and 11.65 mg/mL in those fed freeze-dried transitional milk. Notably, kids fed freeze-dried transitional milk achieved satisfactory immunoglobulin levels, supporting its potential for passive immune transfer. These results highlight the biological value of transitional milk and support its use as a colostrum substitute in intensive farming systems, particularly when maternal colostrum is unavailable or insufficient. Furthermore, freeze-drying effectively preserved its functional properties, enabling convenient storage, handling, and administration. Overall, the successful use and preservation of transitional milk represent a sustainable approach to improving colostrum management, reducing waste, and increasing the efficiency of kid rearing in dairy goat production, in line with circular economy principles.
Lucía Ayala García 