Antibiotics în Milk

1. GENERALITIES

1.1.THE PRODUCTION OF QUALITY MILK: WHOSE CONCERN IS IT?

From history records we know that cows have been milked as far back as 9000 B.C. Most cattle were multi-purpose animals. They were kept to satisfy the family needs of food (milk and meat) and to provide draught power and manure. In those times milk had to be consumed immediately because it could not be stored. Moreover, milk production was seasonal, creating both periods of excess and of deficiency in the family milk supply. To stabilize these production fluctuations and to enable storage, further processing into butter, cheese, or other milk products were invented and developed. Later, this processing allowed marketing of milk, butter and cheese to towns as well. Over the years modern technology has been developed and today a wide array of safe, wholesome dairy products are available to people. Production of quality milk is a complicated process. It is the concern of so many stakeholders, which include: dairy farmers; dairy cooperatives; milk and milk product processors; retail distributors (shopkeepers and super markets); consumers of dairy products; state regulatory departments; extension staff and veterinarians. From the list it is obvious that very few of us are left out. Whether we derive a living from the dairy industry through employment or otherwise, most of us are at the very least consumers of dairy products. In the sections to follow we will examine the efforts made in the processing of dairy products (from the farm to the retail shelf) to preserve the public’s confidence and safety and to remain in dairy business.

1.2.THE ANIMAL

The animal itself is an important source of contamination. Care and management of the animal and its health is therefore the starting point for clean milk production. The skin of the animal provides a large surface for possible contamination. Dung, urine, uterine discharge, dirt, dust and hairs can pass millions of bacteria, when it drops from the skin and udder into the milk. Long hairs on the flanks, hind legs, tail and udder should be clipped at frequent intervals. Grooming the animals regularly can help to keep hair and dust away from milk. When cows are kept indoors or graze in heavily stocked paddocks, the udder will be grossly contaminated with bacteria, even when it appears visibly clean.If the animal is suffering from infections such as mastitis, the milk will contain harmful pathogenic micro-organisms. Milk from diseased animals should be kept separate and disposed of safely. Routine control on mastitis can reduce the proportion of infected cows. It is advisable to test the foremilk at each milking with a strip cup.

1.3.MASTITIS, CONTROL AND PREVENTION

- What is mastitis?

Mastitis is the biggest enemy of a dairy farmer whether small or big. It reduces both the productivity of the cow and the quality of the milk. Mastitis is very common. At any given time it is estimated that approximately 17 – 20 % of the total dairy cow population suffers from mastitis. Mastitis is a disease characterized by inflammation of the udder and is caused by bacteria.

- Causes of mastitis

The risk of mastitis is the highest in early lactation and in high producing cows. It increases with the age of the cow. Factors which predispose to mastitis include poor hygiene, poor animal husbandry and malfunction of milking machines. Wrong methods of both hand and machine milking may damage the teat or udder, allowing microorganisms easier access to the udder through the teat canal.

Fig.1. A cow with an initial stage of mastitis Fig.2. A swollen quarter with mastitis

in one quarter

- Diagnosis

Several simple tests can be performed on the farm at the side of the cow to diagnose mastitis. Clinical mastitis may be detected by examining the udder for warmth or hotness, swollen quarters and pain. Misshapen, hard and fibrotic quarters indicate damage caused by chronic mastitis.The strip cup test is a practical and effective method of identifying cows with clinical mastitis. A few drops of the foremilk of each teat are milked into a strip cup or on a plate with a black surface.

Fig.3. Test the foremilk with a strip cup

The California Mastitis Test (CMT) is another cow side test that can be used for the detection of mastitis. It is more sensitive than the strip cup test and enables sub-clinical mastitis to be detected.