Introduction

Atrophic rhinitis is an infectious disease known since 1830 and widely extended throughout the world. Infection is caused by toxigenic strains of Bordetella bronchiseptica and Pasteurella multocida; other secondary infectious agents contribute to severity of symptoms, as do various environmental and management factors.

Animals affected solely by toxigenic B. bronchiseptica develop a moderate type of rhinitis named nonprogressive atrophic rhinitis (NPAR), which normally is not extremely serious. Nevertheless, when this infection is compounded with toxigenic P. multocida, symptoms and losses in performance are much more pronounced and pigs develop the typical lesions characterised by the emergence of deviant maxillae (upwards or laterally) as a result of the atrophy of nasal osseous structures and disintegration of turbinates. In this case, the term progressive atrophic rhinitis (PAR) is used.

Factors Determining Clinical Symptomatology of Atrophic Rhinitis

Lesion grade depends, in large part, on the age an animal is infected. Infection with B. bronchiseptica must occur at an early age to cause turbinate distortion, whereas P. multocida can do so in animals from 12-16 weeks of age (Jong and Akkermanns, 1986–1999).

For this reason, proper colostrum intake with a rich source of defences is an important point to take into account. Piglets born to primiparous sows and those born with low birth weights show a greater tendency to develop lesions due to the lower quality of colostrum received or greater difficulty in gaining access to it. This can also occur in litters with greater competition at the udder (few teats or many piglets or both elements at the same time). With the high prolificacy of current breeds, proper management of piglet adoptions after birth and supplementation with natural colostrum of the weakest piglets, are key factors in controlling early infections. The best option in severe cases of PAR is vaccination of breeders to provide an adequate level of antibodies. The sow is thereby protected throughout the entire lactation phase; thus, premature weaned animals also have greater possibilities of displaying problems.

Non-compliance of the 'all in - all out' management technique and compromised environments (poor ventilation, low air volume, overcrowding of animals, etc.) during nursery and fattening of piglets contribute to exacerbation of symptoms.

Impact of PAR on Pig Growth

Progressive atrophic rhinitis delays animal growth and predisposes them to pneumonia due in part to the degeneration of turbinates it causes and opening of the door to secondary infections.

In a study conducted by Donkó et al. in 2005, it was observed that its impact is already evident at the initiation of fattening, i.e. from 11 weeks of age.

In this study, weight differences between animals were not observed at time of weaning, although they subsequently displayed various grades of lesions at the abattoir. However, by day 90 (13 weeks of age), the most severely affected animals (grade 3 lesions) represent 29 per cent of the total of pigs and their growth is 3kg less than the others (51.7 grams less per day).

From day 90 until slaughter (approximately 190 days or 27 weeks of age) with 110kg of body weight:

• The most affected animals (grade 3) grew 7.6kg less (75.8g per day) than those showing no lesions and took eight days longer to reach slaughter. They grew 56.8g less per day from day 28 to day 190 (9.6 per cent less than those with grade 1 lesions).
  
  
• Moderately affected animals (grade 2) represent 38 per cent of the total of animals and grew 5kg less (56.8g per day) than those not showing any lesions and took three days longer to reach slaughter. They grew 25.1g less per day from day 28 to day 190 (4.3 per cent less than those of the grade 1 group).
  
  
• Slightly affected animals represent 33 per cent of the total of study animals.

It can be concluded from this study that severely affected animals represent about one third of the total and may have 10 to 15 per cent lower growth than those animals not displaying lesions; animals with moderate lesions grow around four per cent slower. Other trials by Pedersen et al (1982), conducted with piglets up to 10 weeks of age, concluded that animals severely affected by PAR had an ADG nearly 15 per cent lower than those that displayed no lesions. In the chart below, Blaha shows the loss of growth as a consequence of respiratory diseases based on data from Madec and Tillon (1988) and Straw et al. (1989). It can be seen, once again, how animals affected with very mild turbinate and lung lesions can easily lose around four to five per cent average daily gain.

Financial Assessment of Losses Due to Progressive Atrophic Rhinitis and Its Possible Control Via Vaccination of Breeders

Vaccination cost

The cost of a dose of vaccine is around €1.20 to €1.30 per dose. The vaccination programme recommended by technicians from pharmaceutical laboratories is to vaccinate multiparous sows with one dose three weeks pre-farrowing and nulliparous females with two doses (the first dose six weeks pre-farrowing and the second dose three weeks pre-farrowing). In cases of very high incidence, it is advisable to vaccinate nulliparous females three times before the first farrowing, i.e., at five months of age, three weeks later and three weeks pre-farrowing.

Supposing the most expensive treatment is implemented, the per pig vaccination cost in each reproductive cycle would be:

• In nulliparous females:
  3 vaccinations × €1.20 per dose = €3.60 per cycle.
• In multiparous sows:
  1 vaccination × €1.20 per dose = €1.20 per cycle.

Since multiparous sows represent approximately 80 per cent of a farm’s herd and nulliparous females 20 per cent, treatment cost would be:
(1.2 × 0.8) + (3.6 × 0.2) = €1.68 per sow and cycle.

Supposing 10.5 piglets are weaned per litter and the percentage of death events in the nursery is two per cent and in fattening three per cent; 9.75 pigs per sow and cycle would reach the abattoir. This would represent a vaccination cost of:
€1.68 per sow and cycle ÷ 9.75 pigs to abattoir per sow and cycle = €0.17 per pig to slaughter (without taking into account the labour costs of applying the vaccine).

Cost of possible antibiotic treatment

One way to assess financial efficiency of vaccination would be to compare it with a hypothetical antibiotic treatment of diseased animals. Supposing we apply a treatment with 2.5kg of doxycycline per tonne of feed for seven days in 50-kg pigs, treatment would imply a cost of:

• Doxycycline cost: €5.00 per kg (€12.50 per ton of feed, i.e. 0.0125 for 1kg feed).
• Feed consumption: 2kg per day for 7 days = 14kg.
  Treatment cost per 50-kg pig = €0.175.

As can be seen, treatment cost would be approximately equivalent to cost of vaccination. What would remain to be seen is which of the two options is more efficient, although in severe cases of PAR it seems quite risky to expect that a simple seven-day doxycycline treatment would be able to control the disease 100 per cent.

Financial impact of production losses

Ratio between average daily gain (ADG) and feed conversion rate (FCR)

To assess the financial impact of an outbreak of PAR, a hypothetical case of a five per cent loss of ADG during the fattening phase in 100 per cent of animals could be proposed; something that, according to the studies mentioned, is more than likely in cases of PAR. These studies only mention losses in ADG and there is no crucial information available to assess financial impact, i.e. FCR. However, ADG and FCR are closely related.

How can we extrapolate CR loss?

Based on the SIP Consultors data source, an analysis of information from companies and under marketing conditions from 2007 to 2009, a correlation of –0.267 is found, which shows statistical significance (p<0.05) between the two variables. The slope of the regression line is –0.783, signifying a 100-gram loss in average gain; feed conversion increases by 78.3 grams.

Financial impact of a five per cent loss in average daily gain

A five per cent loss in ADG has two types of financial repercussions.

Firstly, direct consequences due to increased fixed costs as more days of fattening are needed for pigs to reach optimum slaughter weight and, secondly, costs arising from a worse feed conversion ratio, thereby signifying an increase in feed consumption and, as a result, feed costs.

The cost breakdown simulator (v1) from 3tres3 will be used to calculate the financial impact of a five per cent loss in ADG to produce a pig from 16kg to 105kg pig. The above-mentioned ratio between ADG and FCR will also be taken into account.

After entering the initial and final weight in the simulator, we obtain reference values for the time spent in fattening (134.2 days) and the conversion rate (2.61). Therefore, the reference ADG is 0.663kg per day, calculated by dividing the kilos gained (89kg) by the time scheduled to be spent in the fattening unit (134.2 days).

The technical reference values are compared in the chart below to values found when the ADG is reduced five per cent (Affected):

Comments:

1. A five per cent reduction in the reference ADG implies a 0.033kg/day decrease, i.e. an 89-kg gain equals a 7.1-day longer fattening period.
   
   
2. Applying the regression curve coefficient (–0.783) between ADG and FCR, we find a growth reduction of 0.033kg/day that causes a 0.026 increase in FCR, leading to a 2.3-kg increase in feed consumption per pig.

The following reference values provided by the simulator will be used to assess financially effects of growth and conversion on production costs:

1. Fixed costs per fattener and year (€35.00), equivalent to €0.096/day.
2. Cost per kg of feed (€0.238/kg).

Taking into account that prevention costs for sows are on the order of €0.17 per pig, and financial impact of the disease is €1.23 per pig when the ADG is reduced five per cent, we achieve a 7.2 per cent economic return. This value is of great interest provided the vaccine is truly effective and vaccinated animals grow the same as those that are healthy.

Conclusion

Supposing a problem with PAR causes a five per cent decrease in growth during fattening, the financial impact would be approximately €1.23 of production costs per pig slaughtered.

This does not take into account other losses, such as medication costs and increased mortality. This situation would be valid provided the supposition is met that vaccinated animals grow the same as if they were healthy, a subject not covered in this article and for which the rationale must be given by pharmaceutical laboratory experts.

Another benefit to take into account is the possibility of eradicating the disease after a few years based on vaccination of breeder sows and introducing negative replacement animals.

If the vaccine costs €0.17 per pig at slaughter and offers animals good protection, it seems clear that its use is fully justified, even in cases in which losses due to the disease could be lower. However, the decision should be supported with proper diagnosis. Observation of clinical signs on farms (deviation of snouts, sneezing, nasal discharge and so on) and evaluation of lesions at the abattoir (affecting the turbinates and deviation of nasal septum) must be accompanied by isolation and identification of toxigenic Pasteurella multocida.

Acknowledgements:

Josep Font (SIP Consultors)
José Casanovas Granell (swine veterinary consultant)

References:

Web page 3tres3.com section. Cost simulator, run by SIP Consultors.
Straw B.E., S. D'Allaire, W.L. Mengeling and D.J. Taylor (1999) Diseases of swine. Blackwell Science.
Donkó T., Kovács M. and Magyar T. (2005) Association of growth performance with atrophic rhinitis and pneumonia detected at slaughter in a conventional pig herd in Hungary. Acta Veterinaria Hungarica, 53(3):287-298.
K.J. Schwartz. Manual de enfermedades del porcino. Suis, Asis Veterinaria.
Pedersen, K.B and Barfod, K. (1982) Nord. Vat. Med. 34:293–302.

Further Reading Find out more information on atrophic rhinitis by clicking here. Go to our previous article in this series by clicking here.

November 2012