Variação das características funcionais do leite bovino de diferentes grupos genéticos

Abstract

This study aimed to evaluate the physicochemical characteristics of milk from cows of different genetic groups: Holstein, Jersey, and Jersolando (Jersey × Holstein), considering the parameters of ethanol thermal stability (ETS), titratable acidity (TA), and hydrogen potential (pH). Samples were collected from three commercial dairy farms located in the municipality of Dois Vizinhos, Pa-raná, Brazil. Collections were performed individually during the afternoon milking on two occasions with a 15-day interval, totaling 144 milk samples obtained from Jersey (n = 44), Holstein (n = 63), and Jersolando (n = 37) cows. The animals were managed under a semi-confinement system, with feeding based on Cynodon spp. pastures, corn silage, and concentrate supplementation with commercial feed and soybean meal. The samples were stored in plastic containers and sent to the Bromatology Laboratory of the Federal Technological University of Paraná (UTFPR), where ETS, TA, and pH analyses were performed. ETS was determined by the ethanol test using increasing concentrations from 64 to 90°GL, pH was measured using a digital potentiometer, and titratable acidity was determined by titration with 0.11 mol/L NaOH solution, with results expressed in Dornic degrees (°D). The experimental design adopted was a completely randomized block design, considering farms as blocks. Data were subjected to analysis of variance using the MIXED procedure of SAS OnDemand, considering the effects of farm, genetic group, parity order, and days of pregnancy. Milk physicochemical variables differed among farms for ETS (p = 0.0379), TA (p = 0.0001), and pH (p < 0.0001). Regarding genetic group, a significant effect was observed only for ETS (p = 0.0024), in which Holstein cows showed greater ethanol thermal stability compared to Jersey and Jersolando groups. Parity order influenced TA (p = 0.0264) and pH (p = 0.0137), with primiparous cows showing higher titratable acidity and lower pH than multiparous cows. Days of pregnancy did not significantly influence the evaluated variables (p > 0.05). It was concluded that genetic and physiological factors influence the physicochemical characteristics of milk and may impact its stability and technological quality.