Quality indicators of tank milk in different production systems of tropical regions

Research was conducted in eight commercial herds located in the state of Rio Grande do Norte, Brazil. Properties were classified according to the production system, the seasons were divided into four and the genetic groups into six. Milk samples from morning milking were collected monthly, directly from a cooling tank. Protein, fat, lactose, total solids, casein, urea nitrogen concentrations/levels, somatic cell count (SCC) and total bacterial count (TBC) were determined. For milk composition, the detected results were satisfactory and met the requirements of Normative Ruling 62, but the averages for SCC and TBC were above the recommended limit. All variables, with the exception of casein from total protein were influenced (P <0.05) by the production system used in the production unit. A lower fat content was recorded in 2010 compared to 2011. For the seasons, all the constituents of milk had lower values in drier season (seasons 3 and 4), with the exception of casein; SCC and TBC had higher values in periods 1 and 2, which are considered rainy periods. There was variation in the chemical composition of milk according to the genotypes. Milk chemical composition met the legal and market requirements, with a positive emphasis on specialized production systems. The variations over the year and according to the genetic group of the herd are also significant and should be taken into account in the search for improvements. As for the hygiene and health aspects of milk, the results portray the need for a greater focus by the entities involved in the sector, as well as the producers, on the viability of an adequacy program and monitoring of management practices related to this criterion.