PREVENTIVE MEDICINE AND HERD FERTILITY MANAGEMENT

Because preventive medicine programmes in dairy herds are usually based on a regular fertility visit, this is a good opportunity to introduce the subject. I like to define preventive medicine as ‘the routine implementation of common sense husbandry.

No new technical information is needed, but rather a different approach to disease control in general, that approach being towards prevention rather than treatment. For some conditions, for example blackleg, vaccina­tion is the preventive measure and the disease can be completely eliminated, although infection remains in the soil and in the intestine of the animal. Most other conditions are far more complex, however, and the level of farm performance needs to be continually monitored if progress is to be made. Mastitis and fertility are good examples of this. Mastitis will never be eradicated and so preventive programmes must be devised to reduce the incidence of the condition to economically acceptable levels, such as those suggested in Chapter 7.

We can only assess the effectiveness of our preventive programmes if we actually record and monitor mas­titis incidence and fertility, and I believe that this is one of the functions of your vet. Not only should he be advising you on the appropriate mastitis control measures for your herd, but he should also make sure that you are recording those cases of mastitis which do occur and that periodically the overall incidence of mastitis in your herd is assessed by an analysis of the records, so that you can compare your performance with other herds. This is commonly available for subclinical mastitis using cell counts, but it needs to be expanded to include clinical cases.

Herd fertility control should be tackled in a similar way. Your vet should be able to advise you on the type of records needed and make sure that a regular analysis of those records is carried out.

The Costs of Disease

The concept of monitoring margin over concentrates and other criteria before making financial decisions has been well accepted and a similar approach should be instigated for animal disease. Before spending money on disease prevention measures we need to know:

• the cost of an average case of a particular disease

• the incidence of that disease in your herd

The subject has been extensively researched in the UK and much of the following is taken from an analysis of herds using the DAISY recording system. The cost of disease may be subdivided into two components, namely direct and indirect costs.

Direct costs: drugs used, reduced milk sales during illness, milk discarded during therapy, vet and herdsman’s time involved in treatment

Indirect costs: increased risk of a fatality, increased risk of other diseases and a possible adverse effect on fertility and on long-term productivity

For many diseases the indirect costs are greater than the direct costs. For example, some typical figures

£183) for mastitis and include an allowance for repeat treatments. The cost of a single case would be less than this. The figures are based on average cases of lameness and mastitis. If there was a high incidence of sole ulcers or of peracute coliform mastitis in your herd, then the figures could be double. Veterinary costs (fees and drugs) represented only a small proportion of the total costs of disease, for example, 14% of the cost of a case of lameness. So although a farmer may think that veterinary costs are high when dealing with an outbreak of lameness, the total costs of the problem will be very much greater.

It should be emphasised that these are one author’s estimate and 1995 figures and the reader is urged to substitute current day values when reading this text. The effect of releasing milk quota, which could then be used elsewhere, has also not been included.

Use of Records

The on-farm monitoring of disease incidence is therefore an essential part of maintaining profitability. Not only will records indicate when the incidence of a condition is becoming excessive, but they may also help to identify the cause of the disease. Examples of how records can be used to distinguish between environmental and contagious mastitis were given in Chapter 7. Other good examples of on- farm performance monitoring are heat detection analysis (Figures 8.13 and 8.14) and the Cu-sum plot (Figure 8.20). The Cu-sum is very simple and yet it gives a good check on conception rate. Fluctuations in fertility will undoubtedly occur: if possible the causes of these fluctuations should be identified, so that preventive measures can be introduced to prevent their recurrence.

This is an area where computerisation has a great deal to offer. For example, we have seen already that poor conception rates may be due to a variety of factors and unless we have a fairly sophisticated means of analysing herd fertility data, it may be impossible to identify which of the factors is a problem in your particular herd. If you are choosing a computer system, make sure that it offers the facility of an in-depth analysis of data, as well as a routine monitoring. It may be important to know whether poor con­ception rates are related to a particular bull, or serving too soon after calving, or previous cases of endometritis, or the average interval between services, or the accuracy of heat detection, and so on. The records are then used in a diagnostic capacity.

I have given several examples of what I think the vet ought to be doing in terms of preventive medicine programmes, so what part should the farmer be playing? First it is important that records are kept and that they are accurate. It is obviously pointless spending time monitoring performance data if the basic records are incorrect. Second, you need to allow your vet to visit the farm regularly, perhaps every 2 weeks, learning what the problems are and how they have been tackled so far.

To give an idea of what I mean, I will briefly describe the system we have used for farms in our own veterinary practice. The DAISY computer programme is now used both for construction of action lists and analysis of health and fertility data, although a non-computerised manual system to construct action lists proved successful for many years.

There are three basic fertility examinations carried out, namely:

• A post calving examination is made to check that there is no residual endometritis. This is performed at between 2 and 4 weeks after calving because many discharges will clear up without treatment by 2 weeks post calving. The examination simply consists of washing the vulva and then inserting a gloved hand into the vagina to check that the cervix is closed and that there is no gross evidence of pus in the cervical mucus. Some vets use a speculum and simply look at the cervix.

• Cows not seen bulling by 40-50 days post calving are examined to make sure they are cycling normally and that there are no cysts.

• Pregnancy diagnosis is performed 5-7 weeks after the last service date.

Cows which have been cycling irregularly, those which have been served more than 3-4 times but have not conceived, and those previously diagnosed as pregnant but which the herdsman suspects may have been bulling may also be presented for examination.

The list of cows sent to the farm in advance of the visit has two important uses. Firstly it compels the farmer to spend a few minutes going through his own records, deleting ‘non-bulling’ cows which have since been served, and cows due for a pregnancy check which have returned to service. Secondly the list reminds him that the visit is due. The discipline of having to check through the herd records every 2 weeks in itself makes a big contribution to improving overall fertility. Problem cows are regularly identi­fied and as such are watched much more carefully.

For a routine visit system to be successful, it should cause the minimum of disturbance to the cows and to the farm routine and, if possible, I like to carry out fertility examinations immediately after morn­ing milking.

Because your vet is checking cows on a routine basis, he can get an immediate idea of whether there is a problem with endometritis, or if too many normal cycling cows have not been seen on heat. This would then be verified by consulting the records. He is in a good position to suggest corrective measures. It may be that he will need to take samples, for example blood samples for a metabolic profile to check energy, protein or mineral status. Because he is attending on a routine basis, it is much easier to follow up at the next fortnightly visit with the results and any corrective measures needed. After a further 2-4 weeks the records may show if the necessary improvement was achieved.

In addition to carrying out fertility examinations, the routine visit is a good opportunity to check a few of the cows which have had troublesome feet, or maybe a group of weaned calves which are a bit loose and not growing as well as they ought. You may also want to talk about worm control in the young stock, or about a new animal health product which has been recently launched on the market.

Mastitis is such a complex subject that it is best to schedule a special discussion period at least once a year, perhaps just before afternoon milking. The records are examined to see what the current herd mas­titis status is like and this in itself may give an idea of what to look for. There may be a high incidence of environmental cases for example, or possibly an excessive number (more than 20%) of treated quarters have needed repeat treatment, suggesting a chronic staphylococcal problem. If it is the winter the cubi­cles are checked for comfort and cleanliness. Finally, in the parlour the milking routine is monitored, as are milking speeds and hygiene procedures such as teat dipping and udder washing, and teat ends can be examined and scored immediately after cluster removal. The whole visit may take an hour or more, but it is an excellent opportunity for the herdsman to discuss mastitis problems and for the vet to check that none of the standard routine control measures are being overlooked. With mastitis costing an average of £31.00 for every cow in your herd, this is time and money well spent.

These are all aspects of preventive medicine. The overall concept is to reduce the effects of disease to economically acceptable levels by a regular assessment of performance as seen both in the records and in the cows themselves. It requires enthusiasm and trust on the part of both the farmer and his vet, but it is the way that veterinary services will progress in the future; that is, in the routine implementation of com­mon sense husbandry.