IT is always difficult to work out the costs of any disease in cattle. The problem of clinical coccidiosis increased in the late 1980s and has remained at a higher level ever since (Andrews, 2001).
It is particularly hard to cost coccidiosis when almost all animals will at some time become infested with the parasite. This will mean any financial estimation can be criticised as being too high or too low. However, most clinicians and farmers would consider that when some outbreaks of coccidiosis occur, it can have quite marked effects on production.
While it is often possible to show production effects of diseases in calves such as poor growth or feed conversion, animals are not followed through either to their slaughter in the case of beef animals or until milking in dairy heifers. When changes occur or are extrapolated, it is relatively easy to put a price on any growth reduction in beef animals as they will be sold on a weight basis. However, the same cannot be done for dairy heifer replacements.
Over the years their age at calving has been reduced, often to a target of two-year calving. This is to reduce the rearing costs, improve genetic turnover and merit within the herd, and often increase lifetime milk yields and other production parameters.
For a calving age around two years to be achieved, and the resultant benefits in milk yields, etc., to occur, it does depend on the heifer growing well and achieving its target growth pattern. Where heifers do not reach these growth targets, it will mean heifers calve at a lower weight with possible consequences for their subsequent yields. There are many reasons why targets in heifers are not achieved and one of these is disease.
This article looks at the cost implications of coccidiosis in calves destined for either beef or for milk production.
Some aspects of coccidiosis infestations
Age occurrence
It can be shown that most calves at some time or another will be infested with the parasite. The two most common and pathogenic species are Eimeria bovis and E. zuernii. In most animals, however, this infestation occurs without any apparent signs of illness or any obvious effects on production.
Whilst in one large study of enteritis in unweaned calves, coccidiosis was found to be the third most common cause, in another report it was the most common enteric problem between three and 12 weeks old.
In a study of weaned calves, it was again the most commonly diagnosed cause of enteritis and also of poor growth in calf groups without any other apparent disease signs. Most coccidiosis outbreaks occur in animals less than six months old, but they can be seen in older suckler calves following weaning, in growing cattle following turnout and, very occasionally, in adult animals.
Environments involved
The infestation is often thought of as being in housed calves, especially where there is overcrowding, poor levels of bedding or faecal contamination of feed and water troughs. Intercurrent disease may be precipitated or exacerbated by clinical infestations. On some units, however, it will occur year-in, year-out even when the housing has been scrupulously cleaned and disinfected. While disappointing, this is not too surprising as it is almost impossible to prevent animals becoming exposed to infestation and it must be remembered than ingestion of one infective oocyst can result in the production of millions of oocysts in the faeces.
Outbreaks can also occur outside in calves, particularly in the period soon after turnout and often where animals congregate around feed or water troughs. Some outside outbreaks occur in older animals and these may be due to a different species – E. alabamensis.
Diagnosis of coccidiosis
Diagnosis is often difficult because animals with no, or very few, oocysts, present may show signs of illness before the infestation becomes patent or following the damage caused to the gut by the intracellular stages of the parasite.
It is the experience of most cattle practitioners that in some groups of scouring calves, there is a response to anticoccidial treatment even when not indicated by faecal examination. However, even when oocysts are present it is often not possible just to rely on the numbers in the faeces for a diagnosis. Some animals with no apparent signs will have very high faecal oocyst counts. This has led to some suggesting that making a diagnosis of clinical coccidiosis should depend on several parameters: these are shown in Table 1.
Mortality
A questionnaire survey of USA cattle practitioners estimated the mortality at about 5% of calves treated. In the UK no data have been found but it would appear possible that a usual death rate of around 1% is about correct. However, this does not include deaths from intercurrent or subsequent disease to which the calves have become more susceptible.
The costs of coccidiosis
The main causes of quantifiable loss from clinical coccidiosis are: (a) impaired production, (b) mortality, and (c) cost of treatment.
However, the losses due to subclinical infections probably far outweigh those of clinical disease. This is partly because of the widespread incidence of coccidial infestation in young cattle. Many of these subclinical effects are unquantifiable but they include: (a) impaired alimentary function, (b) reduced feed conversion efficiency, (c) reduced growth, and (d) increased susceptibility to disease.
Production losses
Most of the literature where production has been monitored involves naturally or experimentally infested animals and then comparing the growth of those teated with that in untreated infected controls. This is a useful method of undertaking an analysis but it does not take into account any effect the medicine may have other than that on the coccidia development stages.
Thus, any medicine might have no other effect on the animal, or it might have a negative effect by, say, reducing appetite or it might have an enhancing effect by improving growth, feed conversion, etc. The ideal comparison of the effects of infestation is to compare uninfected animals with infected ones without therapy. Such studies are few in number and one has to go back over 30 years to find suitable material.
Fitzgerald in many studies was able to show that infested untreated animals had a reduced weight gain for several weeks after infection and then their subsequent growth was similar to, and ran parallel to, the uninfected animals (see Figure 1).
However, the calves did not make up the growth deficit, so that in moderately severely infested animals average weight differences of about 22 to 27kg were seen in one study 10 months after infestation. In other work, reductions in weight have been less (8.8kg over a 15-week period) or more (43kg in 11 months).
As the weight differences remained almost constant until 10 months old, it would be reasonable to assume that these differences might still continue to slaughter. If this was so and the animals were steers slaughtered at a medium weight of 485 to 585kg liveweight, then at an average mid January 2008 market price of 117 pence per kg the possible reduction in weight would amount to £25.74 to £31.59.
In the case of heifers slaughtered for beef at a medium weight (400- 480kg) using a price of 118.5 pence per kg, the possible loss was £26.07 to £32.00.
Another way of looking at the weight differences due to coccidiosis is to determine production costs to reach the same weight as would have been achieved if the animals were uninfested. Thus, using EBLEX’s Business Pointers 2007 costs for a male intensively finished beef, it would take 18.5 and 24 days to produce the extra 22 or 27kg respectively per animal. At a total onfarm cost of £1.64 per day, this results in extra costs of £30.35 to £39.35 per animal. Looking at the costs for extensively finished cattle which could then involve steers or heifers, to achieve the same extra 22kg to 27kg would take 31 to 39 days. The costs for extensively finished beef are £1.47 per day, making an additional cost of £46.50 to £58.50 per head.
As the difference in weight appeared to remain relatively constant, it might be possible to suggest that it would continue until sale for beef or until calving. Heifer lactation yields are affected by many different factors but work a few years ago undertaken at ADAS Bridgets farm, as well as elsewhere, has shown that animals that are heavier at calving tend to produce more milk than lighter ones.
Various figures have been related to this but a useful rule of thumb is that for each extra kilogram weight of a heifer at calving, it relates to possibly four litres extra milk in her lactation. This would mean an extra 88 to 108 litres of milk in the first lactation. The price for milk varies, but using a potential current price of 27 pence per litre this would amount to £23.76 to £29.16 for the lactation.
Mortality costs
At present there are no clear British figures of these costs, but it is possible that direct mortality is about 1% and there is also the cost due to mortality from intercurrent disease in which coccidiosis played a contributory part of, say, 0.5%. Giving a nominal cost of a calf at £50 (includes heifer replacements, beef calves of varying breeding), there is a loss of about £0.75 per animal affected with coccidiosis.
It is probable that this cost is usually too low and this would definitely be the case in higher value calves. The same goes for potential knock-on losses in heifers which in mid January 2008 when sold in milk or late pregnancy made £1,150, considerably less than in previous weeks.
The costs of treatment
There are several products available for treatment and/or control of bovine coccidiosis and all will have a positive effect on infestation. Their costs will vary but need to be included in any cost of the disease. In addition, there are the costs of labour for administering the medicines whether by drenching or adding to the feed. Some medicines may also have a feed mixing cost. However, although they are part of the costs of the disease, they are small compared with the losses in production.
Conclusion
It is generally accepted that clinical bovine coccidiosis has an effect on the productivity of the affected animals. The extent of this effect is hard to quantify. However, American studies involving experimental infestation showed losses in weight gain which were still present over 10 months later. Extrapolating from these results, it showed that there would be significant production loss, and so economic loss, from moderately severe infestation levels.
These losses occur both in animals being reared for slaughter (calculated as being sold at less weight or the extra days until slaughter) and heifers being used as dairy herd replacements. The negative costs calculated were £24.50 to £59.25 at current 2008 prices plus treatment costs. This is roughly £25 to £60 per calf.
Such losses show the economic importance of coccidiosis in cattle production and the cost-effectiveness for treatment, control and/or prevention of outbreaks in calves and older cattle.
References
Andrews, A. H. (2001) More coccidiosis in calves? Veterinary Times 31 (8): 10.
Andrews, A. H. (2004) The diagnosis of clinical coccidiosis in calves. UK Vet 9 (1): 45-47.
Fitzgerald, P. R. (1972) The economics of bovine coccidiosis. Feedstuffs 44: 28-30.
Taylor, M. (2000) Protozoal disease in cattle and sheep. In Practice 22 (10): 604-617.
