Análise da produção e qualidade do leite através de análises bioquímica e de expressão de genes em búfalas (Bubalus bubalis)

Abstract

Buffalo milk stands out on the global stage due to its great nutritional and energy potential and, in Brazil, buffalo milk production is expanding due to its quality and the rustic nature of buffaloes. However, like other ruminants, buffaloes are also susceptible to heat, exhibiting physiological and behavioral changes, characteristic of heat stress. In this context, the objective of this study was to evaluate the biochemical and molecular parameters of milk and blood in order to relate to possible impacts of thermal stress on the production and quality of milk in groups of buffaloes (Bubalus bubalis) with different averages of daily milk production , namely: group with the highest average of liters of milk, MAp (n=6; 3.46 L) and with the lowest average, MEp (n=6; 5.93 L). The compositional analysis of the milk, such as fat, protein and lactose, analysis of somatic cell count (CCS) and cortisol concentration in the blood and, finally, the analyzes of expression of the genes HSP70, HSP90, TLR-2 and TLR -4. As for the biochemical analysis of the milk, the percentage of fat, protein and lactose was not different between the groups (p > 0.05), as well as the concentration of serum cortisol (p > 0.05) and CCS (p > 0 .05), which was below 200,000 cells/mL, characterizing the absence of clinical and subclinical mastitis infection. As for the molecular analysis, the expression of all genes, that is, HSP70 (0.96 MEp versus 0.58 MAp), HSP90α (0.98 MEp versus 0.03 MAp), HSP90β (0.95 MEp versus 0. 48 MAp), TLR-2 (1.02 MEp versus 0.16 MAp) and TLR-4 (1.26 MEp versus 0.07 MAp) was higher in the MEp group compared to the MAp group, respectively (p < 0.05). The correlation test was performed and showed significance only between the parameters: Production x HSP90α (-0.89; p < 0.05), Production x HSP90β (-0.66; p < 0.05), TLR-2 x Production (-0.72; p < 0.05) and TLR-4 x Production (-0.67; p < 0.05). The molecular results indicate that the animals (MEp) were under stress, at least at the cellular level, being detrimental to milk production. However, this damage occurred only in the amount of milk produced and not in the quality of the milk, since none of the composition parameters such as lipids, proteins and lactose showed significant changes between the groups. The correlation data showed that the production and gene expression parameters were negatively correlated, that is, when genes are overexpressed, production tends to decrease. Therefore, we conclude that, in this study, there was a relationship between heat stress and production, however, there was no relationship between heat stress and milk quality.