Interrelationships Between Milk Constituents, Protein Profile, Genotypes of Kappa-Casein Gene and Ethanol Stability of Cow's Milk

Abstract

This study aimed to withstand some factors that may be associated with and affected the alcohol instability of milk. Both individual milk and EDTA whole blood were collected from 162 cows among 4 Holstein dairy farms that suffered from their milk rejection because of milk ethanol instability. Milk samples were subjected to the measurement of milk components, pH, somatic cell count, and total bacterial count. Thirty milk samples were subjected to the detection of AFM1. Three mixed rations from each farm were subjected to the detection of AFB1. Blood samples were subjected to genotyping of the kappa-casein gene. About 72.2% and 27.8% of samples were recorded as ethanol-stable and unstable milk. A significant reduction was observed in the protein, fat, TS, and pH of ethanol unstable versus stable milk while a significant increase in salts, SCC, and TBC was observed. A significant difference was observed in AFM1 in stable versus unstable milk. The concentration of AFB1 ranged from 18.58 ppb up to 34.58 ppb. A significant difference in protein fractions was observed. Genotyping of the kappa-casein revealed that 51, 87, and 24 cows were AA, AB, and BB genotypes. Significantly higher fat and TS percentages and a significantly lower TBC in animals with BB genotypes (p≤0.05) versus those of both AA and AB genotypes were detected. In conclusion, continuous monitoring of different milk composition parameters, udder health represented by TBC and SCC and aflatoxin load in animal feed can be the first steps toward the production of ethanol-stable milk.