Antibiotic Growth Promoters 2 - Diarrhoea Defence Strategies
 
by

David G S Burch BVetMed MRCVS
Veterinarian, Octagon Services Ltd

(Review for Novartis Animal Health - Published in "Pig World" October 2005)
 

Following on from the previous article (Pig World - September, 2005) on the concerns of antibiotic growth promoter withdrawal and the likely associated increase in diarrhoeas, we describe some of the approaches being tried to control and reduce the effects on growing and finishing pigs.

Growth promoters were fed at low levels continuously for most of the growing and finishing period. Some had activity against such infections as ileitis, colitis and even swine dysentery. Because they were fed all the time meant that, in many cases, no further action was required to control these infections.

Therapeutic medicines tend to be more expensive, so the option to feed them all the time is often prohibitive. A more strategic approach is usually employed to achieve cost-effective control.

Ileitis (Lawsonia intracellularis) and also colitis (Brachyspira pilosicoli) infections will induce an immune response in the pig and after a certain period usually 2-4 weeks after infection, self cure occurs (see Graph 1). In some respects, a little infection, sufficient to induce immunity, is a useful thing and provides a prolonged protection through the finishing period. The downside is that disease can also reduce performance, so a controlled infection, to induce immunity and a strategic medication to treat the disease enables the pig to minimise the effect of the disease yet acquire an immunity to fight a further challenge. This can be very helpful for colitis or ileitis infection control.

Graph 1. Colitis Prevention Trial, demonstrating self cure

Porcine Colitis prevention trial, demonstrating self cure
(Source: Glossop, et al, 2000)

With regard to the chronic form of ileitis, which primarily occurs in growers, if immunity is allowed to develop, it will protect pigs throughout the finishing period from the acute form. In Graph 2, the serological response for the chronic form is almost complete in the grower stage (remember challenge or exposure to infection occurs 2 weeks before a serological response). Maternally derived antibodies may offer some protection in the first 8 weeks of life and mitigate challenge.

 

Graph 2. Ileitis Infections:
Different patterns between the chronic form in growers
and the peracute haemorrhagic form in finishers

Ileitis Infections - Different patterns between the chronic form in growers and the peracute haemorrhagic form in finishers
(Source: After McOrist 2004)

The problem with the acute form of ileitis, which causes sudden death and intestinal haemorrhage ('bloody gut' or white pigs) in the final finishing stage is that, besides the loss, medication needs to be applied often at the time of selection for slaughter, so a short/no withdrawal period product is required. A strategic use of medication, for the chronic form of ileitis or colitis, at the time of movement from the grower to the finisher stage (10-12 weeks of age) would be ideal to knock out the infection and allow the immunity to protect for the rest of the finishing period. Movement into a cleaned finishing house, preferably slatted, to prevent or reduce further challenge would be ideal. In a recent trial, (Thomson et al, 2005) pigs of 9 weeks of age (25kg bodyweight) delivered from a nursery unit were treated with tiamulin 100ppm (Tiamutin premix - Novartis) for 7-10 days on arrival, specifically to prevent the transmission of colitis. The isolates of B. pilosicoli from the unit showed good sensitivity to tiamulin in laboratory tests. Half of the pigs remained untreated as a negative control. After 6 weeks the pigs went on to the final finishing unit. Over 1800 pigs were used in each treatment group and the trial lasted for 1 year with 6 batches of pigs.

Table 1. Results of tiamulin 100ppm strategic treatment trial for colitis (B. pilosicoli)

 

Untreated control

Tiamulin 100ppm

No of pigs

1835

1856

Average daily gain (g)

757

880* (16.2%)

FCE

2.03

1.77* (-12.8%)

Mortality (%)

1.08

0.91

* Highly statistically significant

The average improvement in the cost of production per pig was calculated at 1.43/pig or 429/ batch of 300pigs.

A similar approach has been adopted by some major producers, to medicate bought in pigs with valnemulin (Econor - Novartis) on arrival into the finishing sheds. If the infections are primarily a mixture of ileitis and colitis the dose can be titrated down often from 75ppm to 37.5ppm valnemulin in the food for 7-14 days and this has proven most beneficial in performance terms. Chlortetracycline has also been added to control respiratory problems if the pigs were affected.

Dealing with swine dysentery infections are often more complex. The disease is much more severe, so even a little disease can severely damage the intestine and performance of the pig and treatment needs to be instigated more rapidly. Resistance is therefore slower to build up. Olson (1980) showed it took 3 treatments with water medication before immunity developed and recurrence of the disease stopped.

In a recent study (Burch, 2005) on a commercial straw-bedded, scrape-through finishing unit, involving over 2000 finishing pigs, infected with B. pilosicoli, B. hyodysenteriae and L. intracellularis as well as PMWS, PRRS and enzootic pneumonia, tiamulin given in the drinking water at 10mg/kg bodyweight for 5 days was compared with a combination of lincomycin/spectinomycin (Lincospectin - Pfizer) given at 10mg/kg bodyweight for 5 days.

Table 2. Comparative results of tiamulin and lincomycin/spectinomycin administered in drinking water
against a number of enteric pathogens in finishing pigs

 

Tiamulin
(8mg/kg bodyweight for 5 days)

Lincomycin/spectinomycin
(10mg/kg bodyweight for 5 days)

Mortality (%)

3.4

3.9

Hospitalised (%)

8.9

9.1

Liveweight gain (kg)

70.9

69.6

FCE

3.14

3.21

Net margin/pig ()

10.89

9.36

Difference/pig ()

1.53

-

The medications were administered twice, at 3 and 8 weeks in the finishing period. Initially, the colitis infection was treated and disappeared and B. pilosicoli was not isolated again. Acute swine dysentery occurred after the major pull-out period for poor pigs, associated with an active PMWS and PRRS infection, at about 7 weeks and the acute form of ileitis (PHE) occurred towards the end of the finishing period at week 12 (approximately 22 weeks of age), as well as some chronic dysentery and enzootic pneumonia.

Overall, both medications worked well in the face of a severe challenge, but the tiamulin-treated pigs showed a 1.53 extra margin/pig over the other treatment group.

Swine dysentery control is more complex, especially on solid floor systems, which have a higher faecal contamination level than slats. It is important to try to reduce the infection by cleaning up the pigs on or before entry with medication, cleaning out the fattening house between batches and maintaining as high a level of hygiene as possible during the finishing period. Eradication is really the only long-term option for swine dysentery.

In the future, it will be even more essential to understand which diseases are causing the problems on your farm and diagnostics carried out on faeces samples and serology will be increasingly helpful to determine where and when the challenge occurs. A suitable strategic control program can then be introduced in conjunction with your veterinary advisor to maintain performance without growth promoters.

 

References:

Burch, D.G.S. (2005) Novartis Report - data on file

Glossop, C., Whitehead, A., Ripley, P., Burch, D.G.S. and Fisch, R. (2000) Evaluation of the efficacy of Econor (valnemulin hydrochloride) in the prevention of naturally-occurring porcine colonic spirochaetosis. Proceedings 16th International Pig Veterinary Society Congress, Melbourne, Australia, p 12

McOrist, S. (2004) Epidemiology of ileitis. First NAH European Swine Ileitis/Colitis Workshop, Alpbach, Austria

Olson, L.D. (1980) Treatment of swine dysentery for elimination of disease or development of immunity. Proceedings 6th International Pig Veterinary Society Congress, Copenhagen, Denmark, p 247

Thomson, J.R., Murray, B.P. Henderson, L.E. Edwards, S.A. (2005) A cost-benefit study on the control of porcine colonic spirochaetosis in a commercial grower unit. Proceedings Third International Conference on Colonic Spirochaetal Infections in Animals and Humans, Parma, Italy, p 73

 

Copyright © Octagon Services Ltd   2005

*More on Pig Diseases & Medication:  Pig Technical Articles

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