Mastitis is an important disease of public health importance due to the consumption of raw or improperly pasteurized milk. Mastitis is an important disease of great economic importance in diary industry due to intramammary infection (IMI) which results into reduced secretory capacity of the mammary gland [1, 2].
In general, mastitis is caused by bacteria pathogens such as Staphylococcus aureus, Streptococcus agalactiae, environmental streptococci and coliforms leading to direct milk contamination. Cows suffering from systemic disease could also secrete pathogenic bacteria such as Mycobacterium sp., Brucella sp. and Bacillus sp. Majority of the cattle herds are not under veterinary supervision without adequate disease and health programs especially without mastistis screening. Both clinical and subclinical mastistis in dairy cows in Nigeria have been reported by several authors [3 – 5]. Also, unregulated administration of antibiotics to cattle by the herdsmen could result in their residues that is also detrimental to milk quality and dairy technology [2, 6].
There is rising demand for milk and other dairy products in developing countries including Nigeria. Milk is an excellent source of high quality protein diet and also containing a lot of essential vitamins and minerals which can be easily digested and absorbed by all mammals especially the infants. Milk and milk products are major global diets providing about 5-10% of the total calories of the daily human diet in several countries and are the best natural sources of essential amino acids, calcium and phosphorus. These nutrients are essential role in body building, especially the bones and teeth development [7]. These nutritional attributes have made milk an acceptable and staple global diet of both infants, and adults [2].
The largest proportion of milk produced for human consumption is obtained from cattle. Dairy cows efficiently convert human-inedible food and by-products into nutrient-rich milk [8]. The recent dairy farming improvement efforts in Nigeria through public-private partnership scheme comprising collection of milk from different cattle herds owned by nomadic and sedentary pastoralists. This Nigerian Dairy Development Program (NDDP) is geared towards improving the livelihoods of smallholder dairy farmers and improving cattle productivity by integration traditional milk source into the formal dairy value chain in Nigeria [2].
Subclinical mastitis is a major disease affecting the dairy industry [9 – 10]. It causes economic losses by decreasing milk production, costs of therapy, and unused milk during the withdrawal period. Clinical mastitis can be detected by the farmer, but subclinical mastitis can only be detected by the measurement of inflammatory components and pathogens in the milk [11]. Since somatic cell count (SCC) in milk has been shown to be an excellent marker for subclinical mastitis, the use of SCC is inevitable for specifying the reduction of the milk yield [10]. SCC is directly related to the CMT scores as follows: Somatic cell ranges of 0 – 200,000 cell/mL, 200,000 – 400,000 cell/mL, 400,000 – 1,200,000 cell/mL, 1,200,000 – 5,000,000 cell/mL and Over 5,000,000 cell/mL are equivalent to CMT scores Negative, Trace, CMT +, CMT ++ and CMT +++ respectively [12].
The contents and nutritional values of milk, which are important for human nutrition, may be changed with a systemic or mammary gland infection of host animals. High bacterial contamination in milk reduces the quality of both milk and dairy products, affects milk shelf life and flavor, and deteriorates the physicochemical properties of milk. Mastitic milk contains both pathogens and bacterial toxins and its consumption may directly or indirectly increase the risk of foodborne illnesses [10].
Different methods have been suggested for detection of subclinical mastitis, such as the California mastitis test (CMT), SCC, some biochemical methods, the presence of pathogens in the milk, and electrical conductivity (EC) [10]. The husbandry and milking practice by the local dairy producers could result in poor milk quality, since milk is an excellent growth medium for both endogenous and environmental pathogenic and non-pathogenic bacteria [13].
Microbial growth and multiplication in milk result from pre-harvest intramammary infections as well as milking and post milking environmental [12] contamination with deleterious effects on quality, wholesomeness and safety of milk and milk products. Safe and high quality milk can only be obtained from mastitis free and healthy animals. Also, herd hygiene, management and milking processes influence the microbial quality of cow manure milk while cows suffering from a disease could excrete the pathogenic bacteria in the udder with the milk, thereby predisposing consumers to food/milk borne disease. Milk borne outbreaks represent 2-6% of bacterial food-borne outbreaks reported by surveillance systems from several countries [2].
The unhygienic hand milking in the open filed with the milk pooled from unscreened cows collected and stored in local calabash guards commonly practiced by herdsmen in Nigeria portent food safety risks from such products. Private-Public- Partnership efforts of Nigeria government on dairy development aim at improvement of yield, safety and quality milk produced by indigenous cows. Improvement of traditional and nomadic milk production through dairy development programs in Nigeria will therefore require routine quality and safety monitoring of milk parameters such as CMT, SCC, total aerobic plate and coliform counts both at herd level and milk collection centers [2]. Therefore, this study was aimed at elucidating the relatedness of CMT scores and bacterial presence in mastitis milk for safety of consumption of milk and the overall health of the animal.