Influence of the seasons on the quality and composition of milk from dairy farms in the northern region of Rio Grande do Sul, Brazil

Abstract

This study aimed to verify the relationship between parameters of physicochemical composition, microbiological quality, and volume of milk delivered to a dairy in the northern region of Rio Grande do Sul, in 2020, at four different times of the year. For this, the parameters evaluated were volume, protein, fat, lactose, total solids, somatic cell count (SCC), and standard plate count (SPC). Data were collected in January, April, July, and October in 1,634 dairy farms located in the northern region of Rio Grande do Sul. Data were evaluated using Pearson's correlation, and the means were compared using the Tukey test, both at 5% significance. Milk fat and protein contents were higher during autumn (4.02 and 3.35%) and winter (3.90 and 3.36%, respectively), contributing to the higher solid’s concentration in the same period. The microbiological quality of milk, especially the SCC, is compromised during the warmer months due to the thermal stress suffered by the animals, challenging the immune system and increasing susceptibility to diseases. The highest milk CPP in the winter period (247.12 x 10³ CFU/mL) refers to the transfer of contamination from the teat to the tank due to the inefficiency of pre-milking procedures. Therefore, the microbiological quality of the milk was variable between the periods studied, and the fat and protein contents suffered reductions during the summer, reflecting in lower remuneration for quality, given the high CCS in the same season.
Keywords: Dairy cattle; Casein; Climatology; Standard plate count; Lactose.