Gert-Jan Gerrits, Technical Sales and Commercial director, CehaveKorm LTD

Strong, sustainable milk production starts with cows in optimum health. Providing a well-balanced diet based on the nutritional requirements for a high milk yield, in combination with good management, is an absolute must. This challenge is becoming harder and harder nowadays due to the growing pressure to reduce the use of antibiotics in farm animals. As a result, the potential effect of feed supplements on animals’ immunity is attracting greater interest.

The vitamins and minerals that play an important role in udder health include vitamin E, selenium and zinc, thus a sufficient dosage should be given to the animals (see tables 1-2-3).

Table 1: Functions of zinc, selenium and vitamin E and symptoms in cases of deficiency or excess.

Zinc:

Zinc is a cofactor in over 300 different body enzymes needed for functions such as tissue repair and tissue renewal. It therefore plays an essential role in maintaining the surface of the skin which, at udder level, is vitally important in preventing bacterial infection. Because zinc has applications in several body systems, zinc deficiency can have strong adverse effects on growth, reproduction and immunity among other things.

Zinc also plays an important role in keratin formation. Keratin provides a protective layer in the teat canal and, at the teat opening, forms a sort of wax plug that seals the opening after milking. This greatly reduces the entry of bacteria into the teat canal. With each milking, however, 25 to 35% of this keratin is lost from the teat. This means that it has to be produced again every day. However, in a zinc-deficient cow the renewal of the teat plug is a slow process, leaving the teats exposed to a variety of bacteria for longer after milking. Studies have already shown that low zinc levels in dairy cows soon lead to lower milk yields as a result of increased susceptibility to udder infections.

Selenium:

Like vitamin E, selenium is an antioxidant and both have a complementary effect at cell level. Selenium is contained in the enzyme glutathione peroxidase which in turn is responsible in turn for removing toxic hydrogen peroxide from the cells of the body. As a result, selenium deficiency can cause a form of oxidative stress in the body that may damage DNA, disrupt the ion metabolism in the cells and impair cell membrane quality. All of this then results in poor cell function. Selenium deficiencies can therefore lead to lower resistance to disease, probably caused by reduced production of antibodies and a weakened response by the white blood cells to an infection.

Table 2: Minimal feed levels of zinc and selenium per cow per day, according to CVB Standard, The Netherlands

Read the full version of the article in the magazine «Milk and Farm» № 4 (7), December 2011