Tagging cost of managing onset of calf pneumonia

Calf pneumonia is a very common and economically important disease, especially in the rearing of dairy replacement heifers and beef store cattle.

The average cost of a case of pneumonia has been calculated at £29.58, with a quarter of this due to the loss in weight experienced by a sick calf and just under a quarter due to the cost of drug treatments (Andrews, 2000). As well as the reduction in growth rates, calf pneumonia can cause long-term lung damage due to fibrosis and, therefore, leads to a less productive adult animal, with a 150kg reduction in heifer milk production (van der Fels-Klerx et al, 2002) or increased time to slaughter weights.

Many treatment options have been marketed for tackling calf pneumonia, but most do not address the fundamental reasons for the development of the disease.

TempVerified FeverTags are a management tool that can be used to identify and monitor early onset pneumonia and response to treatment of sick animals. They can also be used in conjunction with facility changes to provide a method of measuring its impact on pneumonia prevalence.

Over the past few years, the number of publications around calf health have increased, with a big drive towards the production of healthy, well-grown heifer dairy replacements that reach bulling weight (about 60% of adult bodyweight) by 13 months of age.

Calves have the most efficient feed conversion ratio of any stage of bovine life, with approximately a 2:1 (feed:gain) conversion ratio compared to a post-weaned calf with a 4:1 ratio (Heinrichs et al, 2011). This means, during the pre-weaning period, calves are the most efficient animals to feed and this should be maximised though adequate milk powder feeding rates of 900g/day, with additions made for low environmental temperatures to hit target growth rates of ≥800g/day.

Growth rates of calves are strongly affected by the presence of disease, with the legacy of this disease impacting on their performance as an adult, increased age at first calving and reduced milk production as a heifer (van der Fels-Klerx et al, 2002).

The level of pneumonia is affected by the housing type of calves. Outdoor housing, such as individual or group hutches, have increased air flow and a reduction in spread of aerosolised pathogens between individuals, whereas calves kept indoors typically have poorer ventilation and greater spread of pathogens between animals, especially if the groups contain a wide spread of age ranges.

Accurate assessment of building ventilation and layout is an important part of improving calf health, with the use of smoke bombs providing a good visual assessment of air flow through a building.

Historically, calf pneumonia was considered to be a winter problem, but an RVC study using the ear tags has demonstrated it can be an all-year-round problem, especially when humidity levels are high and air movement is low, such as over the summer period when calves may experience periods of heat stress. Ensuring calves have access to shade and a constant clean water source is important, along with continued farmer vigilance for signs of respiratory disease.

Identification

One of the biggest on-farm challenges is the early identification of calf pneumonia, with subtle signs such as loss of appetite, depression or a raised respiratory rate being easily overlooked by a busy stockperson.

One study demonstrated a stockperson was only able to detect 56% of calf pneumonia cases (Sivula et al, 1996), showing the need for additional pneumonia identification techniques. Manual restraint and examination of neonatal calves and determination of rectal temperatures is time consuming, so is, therefore, often not frequently employed until obvious clinical signs are displayed, by which time significant lung damage may have occurred (Bryson et al, 1983). The tags allow the very rapid and early detection of pyrexia, so providing a useful management tool.

TempVerified FeverTags have been developed to help detect pyrexia in bovines at all ages. It uses a temperature probe inserted into the external ear canal that monitors body temperature every 15 minutes. The temperature probe is connected to a small circuit board with an LED light secured in the ear using a normal ear tag applicator.

When the probe detects the body temperature has risen to, or above, 39.7°C for a sustained period of 6 hours, an LED light will flash for 6 hours to draw attention to the animal. The tag will then enter a monitoring phase where the temperature is taken every 15 minutes and will flash immediately if pyrexia is detected again.

The tags are sold as stand-alone units, each with its own in-built circuit board and LED light, with no further requirements for expensive base stations.

The initial use of the tags on farm requires some training for the fitting and placement, usually with the retailer. Fitting it involves fixing the body though the pinna, similar to a normal identification tag, being sure to avoid the ridge of ear cartilage and positioning the tag as close to the opening of the external auditory meatus. The temperature probe is then guided down into the ear canal using the thumb. One of the key aspects to this procedure is the position of the calf’s head, with the use of a calf halter providing ideal restraint and positioning.

Instalment can be done from birth onwards, although if fitted in very young animals, care must be taken to monitor the placement of the probe as the animal grows, as the probe may need repositioning in the ear canal to ensure optimal body temperature detection.

Once a calf has exited the risk period for pneumonia on farm (the timing of which is farm-dependent), the tags can be removed from the ear, cleaned and reused in another calf. The authors’ experience is one FeverTag can be reused in around three calves. Although prevention of pneumonia will always be better than cure, the tags do allow the very early identification and initiation of pneumonia treatment, allowing targeted and efficient use of drugs.

Available pneumonia treatment options

Many antibiotic treatment options are available for calf pneumonia, with selection based on diagnostics to enable targeted drug choices, especially in the face of specific pathogens, such as the identification of Histophilus somni or Mycoplasma bovis, which are not responsive to all antibiotic groups.

Selection of appropriate antibiotics should also take into account other factors, such as cost, duration of action and spectrum of activity. Use of “older” drug groups (for example, oxytetracycline) should not be ruled out unless resistance has been detected on farm, referring to the World Health Organization’s list of critically important drugs for human health (World Health Organization, 2011) that vets should consider when selecting antimicrobials.

Many traditional pneumonia control programmes use prophylactic (treatment given to prevent development of disease in exposed animals) or metaphylactic (treatment of a whole group before a suspected risk period or exposure) antibiotic treatments, but this increases antibiotic usage. With the tightening of restrictions on antibiotic usage across Europe, and a drive to cut usage, development of tools to help us target antibiotics at the right individuals early in an epidemic ensures rational use of antimicrobials when prevention has failed.

Adjunctive therapy is also an important part of pneumonia treatment. NSAIDs reduce the pyrexia associated with pneumonia (Lockwood et al, 2003), reduce inflammation of the lungs that can lead to fibrosis and the long-term effects of pneumonia that can lead to reduced lung capacity affecting future growth and productivity.

Clinical trials have shown NSAIDs improve the clinical resolution of pneumonia (Deleforge et al, 1994), with flunixin-based NSAIDs demonstrating the most significant reduction in lung consolidation (although no comparative trials have been done using meloxicam; Lockwood et al, 2003).

RVC study

A study by the RVC focused on using TempVerified FeverTags to develop an optimised treatment protocol for calf pneumonia.

The study compared the use of an initial antibiotic treatment with an NSAID treatment as the first line treatment for calves identified as pyrexic through the flashing of a tag.

Results indicated the early use of an antibiotic lead to resolution of 65% of the cases of pneumonia, compared to only a 26% success rate using an NSAID-only treatment.

This study verifies the importance of antibiotics in the treatment of pneumonia detected following six hours of pyrexia, with further work underway to investigate the combined effect of initial treatment with both NSAIDs and antibiotics.

The tags allowed the individual identification and treatment of calves in the study group, with targeted therapy only given to those identified as pyrexic. Compared to a conventional prophylactic treatment system, this allowed targeted antibiotic treatment leading to a reduction in antibiotic use of 54%.

Another advantage of the tag identified by the study was the continued real-time monitoring it offers, as temperature readings continue to be taken even after the initial pyrexia incident has occurred. In many conventional systems, continued monitoring of calves, after treatments have been given, is minimal, with a further delay in the provision of secondary treatments for calves that continue to experience pyrexia or progression of clinical symptoms after the initial treatment.

Summary

Calf pneumonia is a costly disease affecting animals in the dairy and beef industry, with long-lasting consequences on growth and productivity. The initiation of early treatment is crucial for swift resolution of clinical signs, reduction in lung pathology and reduced risk of cross-infection.

TempVerified FeverTags enable effective early detection of pyrexia in a simple way. The targeted use of antibiotics in pyrexic calves and continued monitoring post-treatment by the tag provides a time-efficient and easy method to help stock people ensure high standards of calf welfare and health are maintained.

Acknowledgements

Many thanks go to John Baggs for his help on farm, Tim Farrow and Richard Crider for their provision and technical support with the FeverTags, and Sioned Timothy from Merial, Matthew Burge from Damory Veterinary Clinic and Nick Bell from the RVC for their support with the RVC study.