Decisions to vaccinate growing pigs against respiratory disease are usually based on past experiences of clinical problems. However, they may also be prompted by an adverse result from British Pig Health Scheme (BPHS) inspections and reports - in which case protecting the next batch of pigs may be a wise and economically justified decision.

Lungs damaged by respiratory infection. How much is PRDC costing your herd?

The response to vaccination is usually measured over time, in terms of reduced mortality, fewer clinical problems, and improved BPHS scores. In the long term, the benefits will also be visible within herd performance records and usually through noticeable improvements to growth rate, FCR and mortality.

This may seem logical in theory, but in reality at least two factors confound this simplistic approach:

First, which pathogens are causing the Pig Respiratory Disease Complex (PRDC)? In most cases there is more than one causal agent - hence the common quandary as to which vaccines to use.

Second, is it possible to accurately predict the improvement in pig performance and profitability as a result of a vaccination policy? In an ideal world it would be simple to calculate this before investing the time and expense on vaccines.

ResPig® - A practical and viable solution

ResPig® has been developed by Intervet to help pig veterinarians and their clients to calculate the value of vaccination. But it's far from the usual computer model. The initiative offers much more in terms of practical advice, health management, biosecurity and treatment and control strategies for complex respiratory infections.

ResPig® has three integral components - and each one offers significant value to the pig producer.

• Step 1 - The Production Audit
  This is carried out by an experienced person who will objectively assess all aspects of the production system. Factors such as bio-security, housing type, pig-flow and nutrition will be considered together with an evaluation of the various management techniques used throughout production cycle, from post weaning to sale. A simple scoring system is used for every factor assessed: zero being very good, through to three, which indicates a poor standard that is in need of attention.
  
  
• Step 2 - Diagnosis of respiratory disease
  This is a key element of health management. The benefits of a specific diagnosis, using pathology and post mortem analysis, are well documented. However, most pig producers are still unwilling to invest in laboratory investigations, in spite of the fact that it would enable their vets to implement strategic - and often more effective - treatment and control policies. Such investigation allow vets to conduct a full range of tests to identify which pathogens are present and when the pigs are most at risk.
  
  To support customers and help promote the value of diagnostic services, Intervet will sponsor detailed testing of blood samples for major respiratory pathogens and also the independent post-mortem of three pigs by the VLA. This information, when combined with recent BPHS reports and a clinical assessment by the producers vet, enables a precise diagnosis of incidence and the degree of severity of a disease present in the herd. Each disease is scored from zero to three - zero indicating not present; one moderate presence; two as having considerable impact and three being severe.
  
  
• Step 3 - Economic impact simulation
  This element shows the cost of disease and the benefits yielded from an appropriate vaccination regime. It uses the herd's own performance data, costs of production and financial returns and together with the diagnosed severity of disease, the simulator can demonstrate the response to eight different vaccination permutations. The information presented is detailed and ranges from a no-vaccination strategy, a single vaccination for either M hyo, PRRS or APP, or a combination of two or more vaccines.
  
  The results are presented as the benefits realised per pig produced or per pig place. Values can also be presented for the entire herd on an annual basis. The tabulated results are shown in both financial terms as well as the improvement made to FCR, growth rate, mortality and throughput.

The 'Maybe Not' Option

Weak piglet born as a result of PRRS infection in the sow

John Richardson of Intervet says that demonstrating the benefits of vaccination in terms of productivity is very valuable, however, Intervet's ResPig® simulator will also point out when it may be more cost-effective NOT to vaccinate the pigs.

"Put simply it may be that the return on investment does not justify the cost of vaccination, which is vitally important to cost conscious pig producers," he adds.

ResPig® in action

A 600-sow breed to finish herd was diagnosed as having PRRS and M hyo at a considerable level (score 2). APP was also found but classed as moderate (score 1). The results based on the unit's current performance and cost structure are noted in Table 1.

In terms of physical performance relative to the situation without any vaccination, the regime using PRRS and M hyo vaccination was predicted to give the following improvements:

• Increased growth by 52 gms/day
• Reduction in FCR by 0.22
• A 4.2 per cent improvement in mortality
• Increased output by 1514 pigs sold per year

After analysis, a report is generated showing the results from the economic simulator. Poor and good areas of production are highlighted and advice is provided on how to improve these aspects.

Table 1. Value of vaccination for 600-sow breed to finish unit with PRDC
Net Margin (£)	No Vaccination.	PRRS + Mhyo + APP	PRRS + Mhyo	PRRS +APP	PRRS	M hyo + APP	M hyo	APP
Per pig	0	2.86	2.82	2.55	2.10	2.05	1.54	0.75
Per pig place £/yr	0	6.16	5.94	5.37	4.25	4.22	3.04	1.46
Per farm / year	0	33869	32675	29541	23350	23200	16721	8023

Intervet considers ResPig® to be a hugely powerful tool that pig producers should be using to address PRDC problems and improve efficiency. It clearly shows the merits and value of vaccination, -or not! and how better health management will increase herd profits.

As John Richardson says, the proof can be seen in the output data and the benefits are amply visible in pig performance on farm.

April 2008