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Saturday 10 December 2016

Keeping cell counts down via careful management of milk

Four areas key to limiting infection and aiding production

Eddie O'Callaghan

Published 10/08/2010 | 05:00

Even when cows are out on pasture, high numbers of staphylococcus aureus bacteria on the teat surfaces at the start of milking can
cause problems
Even when cows are out on pasture, high numbers of staphylococcus aureus bacteria on the teat surfaces at the start of milking can cause problems

THE PRODUCTION of milk with low cell counts requires consistent milking management. In some cases, farmers implement hygiene practices when the horse has bolted and the cell count has soared. However, it is often difficult to identify the specific reason for increases in bulk cell counts in milk.

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SCC can be reduced by focusing on four main areas. This involves ensuring that the milking machine is running correctly, implementing a good infection control programme, carrying out the main milking practices correctly and using the management aids to their greatest potential. The fundamental issue is the poor cure rate obtained with antibiotics during lactation. It is a little distressing for farmers when, after full treatment for staph aureus-type infections in particular, the clinical symptoms can reoccur a few weeks after intensive treatment.

Consequences

A major issue in milking management is making the milkers aware of the consequences of inconsistent practices. For example, the correct application of a good post-milking teat disinfection product to cows' teats after milking is the most significant and important task as it reduces new staphylococcus aureus infections by 50pc.

There is a high risk of spread of contagious mastitis from infected to uninfected cows during the milking process. Cluster dipping before the next cluster application reduces the spread of bacteria from cow to cow, and is a useful procedure, but it is quite laborious. Studies at Moorepark have shown that dipping the clusters in disinfectant between cows, or by pre-spraying with disinfectant plus drying with paper, reduces the number of staphylococcus aureus bacteria on the liners (table, below).

Automatic cluster flushing

Automated cluster flushing systems are now available and are effective at ensuring the cross infection from cow to cow does not occur. These systems allow clean water or treated water to enter the long milk tube after automatic cluster removal and flush both the long milk tube and the inside of the cluster.

Pre-spraying

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The high numbers of staphylococcus aureus bacteria that are present on teat surfaces at the start of milking, even though cows are out on pasture, presents a serious challenge.

Pre-dipping or pre-spraying with a disinfectant solution or foam is now practised in order to minimise the number of these bacteria before cluster application. Research data indicates that this practice is effective in reducing the spread of contagious bacteria, such as E-coli, strep uberis and staphylococcus aureus. There is a need to evaluate the products used for pre-spraying as the contact time is short and staph aureus is a difficult bacteria to eliminate. If the cluster that is applied is bacteria-free, as is the teat surface, the possibility for infection to occur should be minimal.

In the past, many mastitis experts were reluctant to recommend pre-spraying due to the poor kill rate of products in the short period of contact between the application of the product and cluster application. There are also residue issues with some pre-spray products. However, new pre-spray foam/liquid disinfectants can reduce bacteria numbers on teats in a short time frame and these products are widely adopted.

Regular tail clipping and having a clean holding yard and approach passages to the parlour can reduce the level of pre-milking preparation. Having a teat sprayer in good order and replacing damaged spray nozzles should be part of the milking-machine service.

Milking technology and mastitis

Undermilking or excessive overmilking are the two main reasons why a milking machine can increase the rate of new mastitis infection. Excessive overmilking (more than three minutes) is a cause for concern in large parlours with greater than 16 units per operator that are not fitted with cluster removers. When fast milking machines are used in these situations, there seems to be little advantage in having an excessive number of units.

Incomplete milking, on the other hand, can be mainly caused by poor liner or cluster designs, worn liners, defective pulsation or excessively high vacuum levels. I notice that the sponge filters on vacuum regulators are often clogged with dust and farmers should clean these at least once a month. A blocked or partly blocked air inlet on a vacuum regulator can result in increases in vacuum level or poor regulator performance. Farmers are more accustomed to the immediate effect of a blocked air filter on the performance of tractors rather than milking machines. When vacuum levels increase, the cows are generally undermilked due to excessive teat penetration.

At this time of the milking season, liners should be changed and farmers often comment on the effect on the improved milkout when worn liners are replaced. Regrettably, it takes the arrival of a high cell count to motivate some farmers to change the liners. If cows are left undermilked, due to worn liners, the bacteria at the teat end can move easily after milking through the milk in the teat sinus up to the gland sinus in the udder and initiate infection.

Dr Eddie O'Callaghan is an independent milk quality consultant based in Kilworth, Co Cork. He can be contacted at eddie@milkqualitysolutions.com

Irish Independent



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