QUALITY OF RAW REFRIGERATED MILK BASED ON SCC AND TBC INDICATORS IN THE SOUTHWEST OF MINAS GERAIS STATE, BRAZIL Qualidade do leite cru refrigerado obtido através dos indicadores CCS e CBT no sudoeste mineiro

Subclinical mastitis is a disease of dairy herds that causes serious financial losses to the producer resulting in reduced production and, in some cases, discarding of milk. Due to this problem, the aim of this study was to evaluate the presence of mastitis in cattle state of raw refrigerated milk producers in a total of 11 dairy farms in the southeast of Minas Gerais state, Brazil, in 2012, and verify suitability to Brazilian Standards IN-62. Duplicated samples were collected every month from April to November 2012 in 11 dairy farms in Southwest of Minas Gerais, bringing a total of 188 milk samples. These samples were collected in cooling tank and stored in sterilized bottles preserved in bronopol for SCC testing and azidiol for coliform microbiological and TBC testing. Among all the analysed variables, SCC results from all the dairy farms differed most from the control group (p ≤ 0.001). Consequently, according to legislation, all the dairy farms can be classified as contamination risk areas for subclinical mastitis considering that they all exceeded the limit values established by law.


INTRODUCTION
Milk production is considered one of the main agricultural activities in Brazil. Its social and economical importance is reflected in the position it occupies in Brazilian agribusiness and it is one of the key sectors for national income generation and tax collection.
In view of its composition, milk is considered one of the most complete nutritional food products and essential for the human diet. For this same reason, it is an excellent substrate for the development of a significant diversity of microorganisms, including pathogens. The availability of milk nutrients and its almost neutral pH makes this medium extremely favourable for microbial growth. The action of bacteria or their enzymes on its components causes several alterations to milk and its by-products. These changes include unpleasant flavours and aromas, reduced validity period, interference of technological processes and diminished yield, especially for cheese (HICKS et al., 1982;CHAMPAGNE et al., 1994). Leite Júnior et al. (2003); Timm et al. (2003) emphasize constant concerns and discussions among technicians and health authorities about the consequences and factors that affect milk quality, especially in relation to the risk of transmitting microorganisms that can cause outbreaks of food-related diseases.
In order to promote milk and by-product quality improvements, add value to Brazilian dairy products and safeguard the health of consumers, in 1996, the Federal Government, through the Ministry of Agriculture, Livestock and Supply -Ministério da Agricultura, Pecuária e Abastecimento, created a strategic public policy for agribusiness in Brazil called the National Milk Quality Improvement Program regulated in 2002, through the Inspection Department of Animal Products (Departamento de Inspeção de Produtos de Origem Animal -DIPOA), published Standard Instruction nr. 51 to establish milk quality identification parameters and criteria for collection, cooling and bulk transporta tion, with maximum and minimum limits of variables for product quality evaluations. Subsequently, to better adapt some parame ters to the reality of brazilian producers, Normative Instruction 62 (BRASIL, 2011) became effective, altering IN-51 (BRASIL, 2002) and amending the fixed limit for variables, Somatic Cell Count -SCC and Total Bacterial Count -TBC. These parameters, together with coliform count, are important tools to determine the incidence level of udder mastitis in a given herd.
Currently the most common mastitis prevention and control indicator is CSS (SOUZA et al., 2005), which, in addition to microbiological parameters, can more effectively and precisely determine the level of contamination caused by mastitis. Cunha et al. (2008) list the factors that can influence SCC variation, such as order of delivery, lactation period and seasonality. However, the occurrence of intra-mammary mastitis is the key factor responsible for SCC variation (HARMON, 1994).
According to Radostits (2000), subclinical mastitis is the inflammation of a mammary gland that results in pathological alterations in the glandular tissue and causes a series of physical, chemical and biological alterations to milk, directly affecting its quality and composition. Of all the different pathologies that affect dairy cattle, this disease causes the most serious financial losses to producers, resulting in reduced production or, in some cases, discarding of milk.
Within the context of this worldwide problem, the aim of this study was to evaluate the presence of subclinical mastitis in cows producers of refrigerated raw milk using the Somatic Cells Count, TBC and coliforms to evaluate the sanitary-hygienic quality during milking in 11 dairy farms in the southweast of Minas Gerais and verify suitability to IN-62/2011.

MATERIAL AND METHODS
Duplicated samples were collected every monthly from April to November 2012 in 11 dairy farms in the southwest of Minas Gerais, totalling 188 milk samples. This region produces approximately 176 million litres of milk per year and this agricultural sector is one of the most socially and economically important sectors in the region. The selection of the properties is: milking type and acceptance of the participants by the milk products. The milking types are: 1) Closed system with holding tank; 2) Closed system without holding tank; 3) Open system with holding tank (Table 1).
Milk samples were collected in the refrigerators at each farm, where they were stored in sterile jars and preserved in bronopol for SCC and azidiol of microbiological testing. The samples were then conserved in isothermal recipients with recyclable ice with approximate refrigeration temperature of 4 ºC and sent for testing at the Food Product and Environmental Analysis Laboratory (FPEAL) -LAAPA in the Passos Foundation of Higher Education (FESP/UEMG).
The multiple tube technique was adopted for total and thermotolerant coliforms. For total coliforms, the Brilliant Green Bile Broth 2% bacteriological culture medium was used with incubation at 36 ºC for 24 -48 hours. The contaminated samples were subsequently transferred to tubes with E. coli broth to determine the presence of thermotolerant coliforms in a 24-hour period with incubation at 44.5 ºC. The Most Probable Number (MPN/mL) was used in all coliform samples, as described in the Compendium of Methods for the Microbiological Examination of Foods (VANDERZANT; SPLITTSTOESSER, 1992).
Total Bacterial Count was measured using the method described in the Compedium of Methods for the Microbiological Examination of Foods (Swanson et al. 2001), which consists of quantifying a group of bacteria found in milk by inoculating the samples on plates and incubating at 36 ºC for 48 hours. The culture medium used in the plates was Plate Count Agar that contains nutrients that allow bacterial multiplication. Results were obtained by counting the colonies expressed in a Colony Forming Unit -CFU.
Somatic cell count of milk samples was based on the 300 system of Bentley, by flow cytometry. Results of milk sample tests were compared using IN-62 standards (BRASIL, 2011).
Data were analysed using two-way analysis of variance (ANOVA) associated with the Tukey multiple comparison test to determine whether the parameters studied in each farm differed from the control. The control group was based on limit values for each parameter according to . Original data of average values for each variable were transformed into base-10 logarithms. All statistical data were analysed using the SigmaPlot 11.0. programme. Table 02 shows results obtained from microbiological testing and CSS of raw refrigerated milk conducted at the 11 studied dairy farms, and limits of each variable established by   (BRASIL, 2011).

RESULTS AND DISCUSSION
Currently, there is a widespread debate about the importance and standards of SCC and TCB to guarantee hygiene and quality of milk (GODKIN, 2000), and on how to ensure that producers produce better quality milk and subsequently add value to their end product. However, whilst attempting to adapt legal reference values to the reality of Brazilian producers, MAPA altered the limit values of SCC from 6.00 x 10 5 to 4.00 x 10 5 , and of TBC from 5.00 x 10 5 to 10.00 x 10 5 , thus increasing strictness of compliance with two of the key parameters of milk quality indicators. The total and thermotolerant values of this present study were compared to those of the Compedium of Methods for the Microbiological Examination of Foods (SWANSON et al., 2001).
Among the analysed variables, SCC results of all the farms differed most from the control (p < 0.001). Consequently, according to IN-62, all daily farms can be classified as risk areas for subclinical mastitis contamination and as producers of lower quality milk. In spite of reducing concentrations of TBC and SCC according to IN-62, all the farms exceeded the limit value established by law. Therefore, the analysed milk indicates lack of mastitis control in the studied farms, as SCC is used to designate all cells found in the milk, including haematopoietic cells (leucocytes) and squamous epithelial cells, that increase significantly when there is swelling in the mammary gland (NATZKE, 1981).
In addition to increased cell count, mastitis causes alterations in the three main components of milk: fat, protein and lactose. Enzymes and minerals are also affected. The extent of increased SCC and changes in milk composition are directly related to the surface of mammary tissue affected by the inflammatory reaction (SCHAELLIBAUM, 2000). Furthermore, fat and lactose tend to drop as SCC increases.
In the study by Paiva et al. (2012) the percentage to SCC, in milk sample in 2008 increased in 60% according to the IN-62. The authors concluded that the seasonal variations influenced both the refrigerated raw milk quality and the TBC increase.
Seasonality is considered a primordial factor of SCC variations in cattle. In a study conducted by Bueno et al. (2005) that compared the SCC of milk during seasons showed a correlation between environment temperature and SCC variation, being that the highest averages of SCC occurred in the dry season (September and October). Magalhães et al. (2006), observed a greater tendency of increased SCC in the summer (January to March), correlating this variable with increased temperature, meaning that SCC increases as the temperature increases. However, Peller et al. (2000) emphasized that higher SCC associated to risk factors of subclinical mastitis is proportionally related to a greater number of calvings and start and end of lactation.
Another indicating factor that can cause CSS variation is related to the different milking systems used for dairy cattle. Milking can be manual or mechanical by means of an open or closed system. The milking location may or may not have a holding tank.
Comparing SCC results of the studied farms, the only differences were between Farm H and Farm A (p = 0.04), E (p = 0.36), F (p = 0.01) and J (0.01), which confirms that milking systems did not directly influence the high incidence of mastitis in the farms as these differences were detected in farms that used the same milking system (Table 01).
Results also showed that farms (A and K) with closed circuit freestall milking systems with tanks caused a reduction in somatic cell count, while other farms where production was mostly in the pastures presented increased SCC. The freestall cattle confinement system can influence contamination because after milking the cows are guiding to feeding stalls and remain standing until closing of the sphincter, thus reducing the possibility of environmental mastitis contamination.
According to Carvalho et al. (2013), the SCC variation is more closely related to a lack of equipment and tool maintenance or their inadequate usage, than to the actual system.
In a study carried out by Borges et al. (2013) in the mesoregions of Minas Gerais Central and west parts, it was believed that the values of the Somatic Cell Counting (SCC) were in the legally established limit of 600,000 cell/mL, except in the production range above of 1,000L/day, according to the Normative Instruction n. 62 (IN-62/2011). The total bacterial counting was the most critical factor. The average values of bacterial counting surpassed the current prescribed limit, and the cattle with daily production of over 500 L/day were the ones which presented a higher number of results which are not according to the legal standards.
Given the high concentration of somatic cells, there is also a tendency for increased TBC, although TBC parameters, as in the case of coliform testing, and considering the nonstandardization of limits in the laws of dairy products, are more closely associated to better hygiene-sanitary quality of milk than to the incidence of subclinical mastitis.
TBC results showed that eight dairy farms presented differences in relation to the control group, indicating that the incidence of mastitis is related to TBC. According to Eneroth et al. (2000), contamination of dairy products by TBC bacteria may be the result of inadequate quality of the water supply and hygiene procedure deficiencies, and not only mastitis. Therefore, hygiene procedures conducted in the productive chain of milk are critical for the obtainment of a high quality raw material.
Cousin (1982); Hogan et al. (1988) state that TBC is influenced by humidity and temperature of the environment, which directly reflects on hygiene of the animal, environment, equipment, milking procedures and cooling. Considering the potential for multiplication, milk bacteria can cause alterations, such as the degradation of fat, protein and carbohydrates, and render the product unfit for consumption and industrial processing. The TBC increase poses a risk for the consumers' health because of the disease traffic and, for the industry; it brings damages regarding sensorial problems in the milk derivatives (Mendonça et al., 2001).
Results related to contamination of milk by the total coliform group and thermotolerants all the dairy farms got different with the controlling. It is therefore increasingly important to produce good quality milk. Hygiene of the animal and hands of the milker are essential to achieve this objective (SANTOS;FONSECA, 2007).
In these contexts, the quality of raw milk is affected by several conditions, especially zootechnical factors, handling, feeding and genetic potential of cattle and factors related to the collection and storage of freshly milked milk (CARVALHO et al., 2002). Temperature and time of milk storage are also important, as these factors are directly related to the multiplication of microorganisms found in milk (GUERREIRO et al., 2005). Consequently, sanitary and hygiene control of herds and milking is fundamental to ensure the ideal composition of milk and reduce the risk of pathogenic agent transmission.
Good practices in milk production applicable to the areas of animal health, milking hygiene, nutrition, animal wellbeing and environmental conditions were established with follow-up and guidelines to producers by means of monthly reports. Results were also discussed to identify critical contamination points, support improvements of milk production and ensure that raw materials were collected from healthy animals and maintained under acceptable conditions. It was also emphasized that these activities should be constant, progressive and personalized to guarantee better adaptation to the reality of each farm and current legislation.

CONCLUSIONS
The sanitary hygienic quality of milk are not suitable to requiring IN 62/2011. The microbiological quality of milk indicates the necessity to improve the production system of milking, equipment sanitizing and the sanitary hygienic handling to obtain milk.
The implementation of a system of payment for milk quality producer is necessary to improve the quality indices of the raw material, which does not occur at the study site.
(FAPEMIG) and Fundação de Ensino Superior de Passos / Universidade do Estado de Minas Gerais (FESP / UEMG) for financing the project and helping in the logistical support in which the work can be performed successfully. We also thank all trainees for help in the field and in laboratory.