Cell Check – ‘First’ things first

In the second of a series of articles highlighting the elements of LLM’s popular ‘Dairy Monitor Cell Check’ service, Bill May looks at ‘First’ infections, how they are monitored and how they may be controlled.

Cell Check Report

‘Firsts’ – What are they?

First infections are cows that record a cell count of >200,000 cells per ml at the first recording of their current lactation. They are expressed on the Cell Check report as a number and as a proportion of all of the cows recorded for the first time in their current lactation that month e.g. 30 cows recorded for the first time, 10 of which have a cell count of >200,000 cells /ml. Firsts = 10/30 = 33%. The target performance level for Firsts each month is <15%.

‘Legacy Firsts versus Fresh Firsts’

The major distinction to make within the Firsts category is whether the infection has occurred since the last recording of the previous lactation (a ‘Fresh First’) or whether it is a longer standing infection which failed to cure over the dry period (a ‘Legacy First’). This distinction is made on the basis of the cow’s last cell count recording; if it was above or below 200,000 cells/ml. This distinction tells us if the First infections are a problem of failing to cure Chronic infections over the dry period, OR whether they are a problem of Fresh infections becoming established over the dry period.

Of course, there are several circumstances in which these assumptions do not hold up; for example a cow with a high cell count at the last recording of the previous lactation can be cured with dry cow therapy and then become re-infected. In this scenario, it is assumed to be a failure of dry period cure when in fact it is a failure of dry period protection. However, in most circumstances this broad division of Firsts holds up.

The Cell Check report shows both the current month and the last six months average of First infections.

Cell Check Report - Benchmarking Data

Prevention of Firsts

Legacy Firsts are effectively Chronic infections that have failed to cure over the dry period. Given that the dry period affords the best opportunity for long-standing udder infections to be treated and to cure, then the chance of treating and curing a cow during lactation that has failed to cure in the dry period is unlikely. These cows should be treated as Chronics and a decision made on each cow as to whether they should be bred again and/or retained in the herd.

The control of Legacy Firsts is dependent on how these infections are originating from the outset and the cell count records should be interrogated. The type of predominant udder pathogen(s) in the herd can determine how many Legacy Firsts arise, for example a herd suffering with Staphylococcus aureus infections is likely to end up with more than a herd that predominantly suffers from E.coli infections, but typically the target for Legacy Firsts would be <30% of the total number of Firsts.

Fresh First infections can theoretically occur at any time between the last recording of the last lactation and the first recording of the next lactation. The highest period of risk for Fresh infections has been shown to be immediately after dry off and shortly before and at calving. Broadly speaking, the areas that have been identified as highest risk are:

1 – Drying Off
When cows are dried off they are at high risk of acquiring Fresh infections, as (one or more) products are infused into the quarters and residual milk is present for a period of time, which can support bacterial growth. In addition, the naturally occurring antibacterial chemicals that accumulate in the udder are not yet present in any significant concentration. Following a hygienic drying off protocol will reduce the chances of an infection being introduced at this time and the training of stockpersons in the consistent application of the correct technique is crucial.

2 – Dry period / Transition period management
As well using Orbeseal teat sealant to physically prevent infections from finding their way into dried off quarters, do not neglect the conditions in which dry cows are kept. If indoors, a clean, dry, well bedded and ventilated building that is not overstocked is required. The current recommended stocking density for dry animals is based on the cow’s milk yield and is 1.25m2 per 1000 litres of yield, in other words 12.5m2 for a 10,000 litre cow! When outside and especially in bad weather, dry cows are sometimes exposed to high levels of mud and slurry. These areas can represent a high risk for the introduction of fresh infections even with teat sealants in place.

3 – Management at calving time
Calving time presents arguably the greatest risk period for acquiring Fresh First infections and is often the best area to audit when a problem arises. A number of management practices can reduce the risk:

a. Removal of the calf ASAP after calving:
Leaving the calf with the cow to suckle naturally increases the risk of introducing Fresh First infections into the udder. The calf’s mouth will transfer pathogens onto the outside of the teat and usually the quarter suckled is not completely milked out. Leaving the calf on the cow in the calving area also increases the risk of the calf picking up a neonatal scour pathogen such as Cryptosporidiosis, E.coli and Rotavirus (as well as some exotic pathogens such as Salmonella), not to mention Johnes.

b. Milk the cow out fully at the first milking:
Not milking a freshly calved cow out fully at the first milking used to be common practice in order to help manage milk fever. However, leaving residual milk in a freshly calved udder increases the risk of Fresh First infections and is unnecessary. There are very effective nutritional solutions to the management of milk fever that are successfully employed on many farms to keep it’s incidence to almost zero, so milking the cow out fully as soon as possible after birth of the calf is recommended.

c. Routine maintenance and hygiene/disinfection of the milking equipment used on freshly calved cows:
Sometimes a separate standalone unit is used to milk fresh calved cows, that can be taken into the calving area and run from a vacuum line. These units have separate pulsators that are rarely serviced and often unknowingly malfunction even though appearing to effectively milk the cow. They are also often neglected in terms of appropriate disinfection after each milking, but are high risk for the spread of contagious udder pathogens. Remember to both regularly service and to wash and disinfect these units effectively if they are routinely used.

4 – Remember heifers are different!

Heifers often represent a quarter or more of the calvings in the herd but have usually been managed differently to the cows in the run up to calving. The Cell Check report allows the incidence of First infections in heifers over the preceding twelve months to be compared to the incidence in the herd over the preceding six months, so that their contribution to the overall incidence can be assessed. The target incidence in heifers (<10%) is lower than in the herd as a whole (<15%), mainly because the majority of heifers should have no pre-existing infections in the udder from previous lactations.

However, unlike many cows nowadays, heifers lack the physical protection against Fresh First infections in the run up to calving that is provided by Orbeseal teat sealant. They can also get significant udder and teat oedema (‘hogging’) at calving that prevents the effective milk out of quarters. If you do have a high number of heifers with First infections, then there are a number of control strategies.

Heifer Control Strategies

If heifers appear to have a high incidence of First infections then there are a number of control strategies that can be considered. Firstly, their rearing environment(s) should be checked as this is often a different part of the farm or even a different unit altogether, so that in some cases a significant number of heifers can become infected well before calving.

The majority of First infections in heifers do occur around calving though, a problem that has been seen in New Zealand where large numbers of animals have been infected in unfavourable outdoor conditions. Here the use of Orbeseal teat sealant 3-4 weeks before calving has significantly reduced the incidence of Streptococcus uberis infections occurring after calving. In the UK this practice would constitute ‘off label use’ of the product so consultation with your routine vet is recommended.

Anyone wanting to try the Cell Check reporting service, contact the Practice on 01948 663000. The most recent herd recording data can be downloaded from any of the major recording companies once permissions have been given.