Beat somatic cell counts before they beat you

Dairy farmers should take note of the causes and effects of high somatic cell counts as milk buyers and processors worldwide implement more stringent requirements in this regard.
Issue date: 2 March 2007

- Advertisement -

Dairy farmers should take note of the causes and effects of high somatic cell counts as milk buyers and processors worldwide implement more stringent requirements in this regard.

Lloyd Phillips finds out from udder health specialist Dr Inge-Marié Petzer how dairy farmers can get on top of this new development.

Somatic cell counts (SCCs) are important as they can indicate both udder damage in a dairy herd, and the negative impact on the quantity and quality of the milk produced. SCCs can also negatively affect the production quality of products,” says Dave Durham, managing director of Orange Grove Dairy near Dundee in KwaZulu-Natal.

- Advertisement -

 “For example, milk with high SCCs can result in lumpy or granular yogurt. We recently had to throw away a large quantity of yogurt after inadvertently using milk with a high somatic cell count. We lost a lot of money.” Durham was speaking at a recent Dairycide Information Day for dairy farmers hosted by Orange Grove Dairy and Southbroom Chemical Distributors. The speaker was Dr Inge-Marié Petzer, an udder health specialist from the University of Pretoria’s Faculty of Veterinary Science at Onderstepoort.

Dr Petzer says dairy processors internationally are reducing the levels of SCCs in milk that they are willing to accept from dairy producers due to the impact these cells have on dairy product quality during processing. The current average SCC that processors in SA, the EU, New Zealand and some other countries are willing to accept is 400 000 cells/ml of milk.

However, the EU is already in discussions to possibly decrease these counts to as low as 250 000 cells/ml. Other countries are likely to follow suit and this could have serious implications for SA’s dairy farmers who want to export their milk. “Dairy farmers must realise that apart from losing money on milk with too high SCC levels, these cell counts are also a direct indication of their herds’ udder health,” stresses Dr Petzer. ”It is not easy to maintain a low SCC, but it is possible.

A 2001 UK report revealed an average herd SCC of 170 000 cells/ml to 180 000 cells/ml. With hard work, there’s no reason why SA’s dairy farmers cannot achieve this too.” Five points to control SCCs M any factors hamper dairy farmers from achieving lower SCCs. However, by using the UK and EU’s five-point plan as a basis to control SCCs, South African farmers can achieve greater success in lowering counts.

In summary, the five points of the plan are: ensuring the constant efficacy of the milking machine; implementing an effective post-milking teat dip; treating clinical mastitis effectively; having a blanket dry cow therapy programme; and culling all cows with incurable cases of mastitis and high SCCs.
According to Dr Petzer the causes of high SCCs are physiological (colostrum, disease and stress), environmental (temperature humidity index, nutrition deficiencies, incorrect handling of cows, and the incorrect functioning and use of milking machines) and most important of all, mastitis. C olostrum has high SCCs (antibodies for the calf) and farmers should be careful not to add colostrum to the bulk tank. This could increase the SCC and cause milk to test false positive for residues in some tests.

At the same time, SCCs will be higher at the end of a cow’s lactation in preparation for her dry period. As somatic cells consist of about 90% white blood cells (antibodies against disease and infection) and 0% to 10% of epithelial cells (body cells), it’s important to minimise stress on cows. Increased stress levels challenge the immune system of a cow, in turn increasing the risk of sickness. White blood cell (WBC) levels increase to fight illness and these WBCs can also increase in number in the cow’s milk.

The available WBCs in circulation of a cow with a chronic udder infection can decrease over time, rendering that cow more vulnerable to other diseases. Lowering SCC levels dequate hygienic practices during milking are important. Staff should disinfect their hands before, after and while working with udders and equipment during milking.

Since 2000, Dr Petzer and her colleagues have isolated bacteria from mastitis cases that originate from humans. This, she says, could have been prevented by good milker hygiene. “With regard to the environment, in warmer areas cows should be kept cool with shade and shelter against the elements. Handle cows gently and with minimum stress,” Dr Petzer advises. Some of the problems in SA resulting in high SCCs are improper functioning, lack of maintenance and incorrect use of milking machines. has been confirmed by more than 600 000 laboratory tests performed at the milk laboratory of the Veterinary Institute and by on-farm testing of milking machines.

Too many vacuum fluctuations and incorrect vacuum levels at the teat end of milking machines are the culprits causing teat end damage. High milk lines is a higher risk than low milk lines for a too-high vacuum level at teat end.
The lack of proper vacuum reserve on a milking system (pump too small or leakages on the system) affects vacuum fluctuations. The ideal vacuum level at teat level during the second minute of milking is 36kPa to 38kPa for the average cow in the herd and 32kPa to 34kPa for the above-average cow. A too-high vacuum will strip epithelial cells off the inside off the teat canal and damage the teat end, resulting in increased mastitis cases and high SCCs.

Dr Petzer says flowmeters installed high above or far from the cow’s udder can result in a delayed response by automatic cluster removers, causing overmilking. This is painful to the cow and causes teat damage. Clean the vacuum control valves, sensor, pulsator inlets and filters weekly. If a long pulsator line blocks even partially, the milking machine will milk two teats faster than the other two in a 2×2 system.

This results in overmilking and will damage the teats. “Vacuum meters must be easily viewable so the dairy manager and staff can monitor the vacuum level and vacuum variations during every milking, and identify and fix a problem immediately before udders are damaged,” explains Dr Petzer. Udders and teats should be properly stimulated and clusters attached 30 seconds to 60 seconds after touching. This encourages the cow to release milk effectively for about five minutes.

Poor udder stimulation will result in slower milking times, lower milk production and lower butterfat percentage due to the cow withholding milk or releasing it slowly. All rubber parts of the milking machine, especially teat liners, must be regularly checked to ensure they are working properly. After 3 000 milkings, teat liners no longer massage the teats properly, resulting in less milk production, slower milk flow and even mastitis. It is essential to apply post-milking teat dip correctly using non-return teat cups, effective disinfectants in the correct concentrations, and clean water for dilution.

 The disinfectants kill bacteria that might migrate up the teat canal to cause mastitis and, therefore, a relatively long-lasting post-milking teat dip should be used. It should be effective against gram positive bacteria, have a limited effect on the bacterial plate count, but contribute to lowering SCCs.

Minimising mastitis Dr Petzer says South African dairy producers often don’t treat clinical cases of mastitis effectively and this contributes to more and longer-lasting mastitis cases. The correct use of antibiotics and their treatment periods and intervals, together with hygienic application and record-keeping are essential to overcome this problem.

If two sets of treatments don’t cure a cow, it is in most cases a waste of time and money to continue the treatment. Chronic mastitis cows should be culled to stop further mastitis infections in the herd. “Maintaining good biosecurity will also minimise the risk of mastitis – that could result in increased SCCs – developing in the herd,” advises Dr Petzer. ”Off-farm new animals are a potential danger for introducing mastitis and should be quarantined and tested before being allowed to mingle with the existing farm herd. It is also important not to let strangers handle your cows unnecessarily.” Contact Dr Inge-Marié Petzer on (012) 529 8088/8405 or e-mail [email protected]. |fw