Milk quality in high production systems during dry and rainy seasons according to normative instruction N° 62
This study aimed to evaluate the milk quality of crossbred cows from five production systems according to the quality parameters required by Normative Instruction No. 62 (NI 62). Five different production systems were used, with different environmental and sanitary conditions, and with animals from different breeds in two seasons: dry and rainy. Three individual milk samples were collected from animals in the five production systems during the dry season; the same number of samples was collected during the rainy season. The samples were evaluated in the Milk Quality Laboratory of the Federal University of Goiás using analytical principles based on infrared differential absorption of milk components. The data were analyzed with a 2 × 5 factorial system in which factor 'A' includes the seasons and factor 'B' includes the five different production systems. The values of fat, protein, lactose, nonfat solids (NFS) and somatic cell count (SCC) were analyzed. Throughout the experiment, the chemical composition of milk was in accordance with NI 62; however, in relation to SCC, System 2 did not produce milk with optimal quality parameters and did not follow the criteria established by law. The analyzed milk had higher protein content of 3.32%, NFS of 8.89% and SCCs of 492,180 SC/mL during the rainy season compared to the dry season. Higher SCCs were also observed with increasing concentrations of fat and protein in the milk. Lactose and NFS values were found in lower concentrations with increasing SCCs due to epithelial damage present in animals with high SCCs. The systems differ among each other in some factors due to the particularity of each system. It was concluded that the milk components are in agreement with those required by NI 62, however all systems produced milk with higher SCC levels during the rainy season.
Keywords: Chemical composition, somatic cell count, season, individual milk samples, quality