October 2008 No. 7

General articles:

QLIF training and exchange workshop - Improved quality in organic food production

QLIF papers in
'Cultivating the Future Based on Science'

Registration open
for the 5th annual
QLIF congress

Knowledge synthesis on opportunities and barriers for organic production

QLIF research

Suckling systems improve natural living in organic dairy calves

Herbs in the diet moderates roundworm infections in organic pigs

Animal welfare of rodent pests needs public awareness

Differences in the composition between organic and conventional milk

Ozone treatment keeps the quality of fresh-cut green leaf lettuce

Single cleaning of pig pens is ineffective against roundworms


Final QLIF training...
Reseach Vision...
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Knowledge synthesis...

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Herbs in the diet moderates roundworm infections in organic pigs

by M.M. van Krimpen, G.P. Binnendijk, F. Borgsteede and C. Gaasenbeek, Animal Sciences Group, Wageningen UR

A diet with a mixture of Thyme, Melissa and Purple Coneflower, all at 1 percent, reduces the number of roundworms (Ascaris suum) in growing and finishing pigs. However, the herbs does not decrease the number of pigs which are infected. Black Tea added to the herb mixture does not improve the efficiency.

Control of roundworms in pigs

The percentage of disapproved livers of growing and finishing pigs has increased during the last years. And often this percentage is higher in organic than in conventional pig farms. Disapproved livers are in most cases the result of an infection with the roundworm Ascaris suum.

Usually, an infection of Ascaris suum is treated or controlled by using conventional synthetic drugs. Organic farmers, however, prefer a non-pharmaceutical approach of worm control. Therefore, use of herbs with high contents of active component, such as phenols and tannins, could be an interesting alternative.

Echinacea purpurea  Thymus vulagaris  Melissa officinalis

The objective of this study was to test the ability of herbs to prevent and control a mild infection of Ascaris suum in growing and finishing pigs. The tested herbs were thyme, melissa, purple coneflower and black tea. A full account of the present study is provided by van Krimpen et al. (2007).

Comparison of four experimental treatments

An experiment was conducted with 32 young boars (average starter weight was 24 kg) purchased from a SPF-pig farm. The pigs were monitored during 67 days in the period December 2006 until February 2007. Four treatments were compared:

  1. negative control: no treatment was applied to prevent or control an infection with Ascaris suum

  2. positive control: pigs were treated with a conventional anthelmintic (Flubendazole) one week before slaughter

  3. herb mixture: pigs were fed a diet supplemented with a herb mixture

  4. herb mixture + tea: pigs were fed a diet supplemented with a herb mixture (as treatment 3) plus black tea.

All pigs were housed individually and fed a commercial organic starter diet during the first three days. Pigs of treatment 1 and 2 were fed this diet during the whole experimental period. From day 3 onwards, pigs in treatments 3 and 4, respectively, received a comparable starter diet supplemented with herbs (1% Thymus vulgaris, 1% Melissa officinalis and 1% Echinacea purpurea), or herbs plus tea (also including 1% Camellia sinensis).

From day 17 until day 21, all pigs were infected daily by oral inoculation of 200 Ascaris suum eggs. In total 1000 eggs per pig were inoculated.

From day 39 onwards, supply of the herb diets was stopped and pigs in treatments 3 and 4 received the same diet as the pigs in treatments 1 and 2. On day 59, pigs in treatment 2 were treated with Flubendazole. On day 67, all pigs were dissected to determine the worm burden in the small intestine.

Herbs reduced the number of worms per pig

All livers from all treatments had white spots, indicating that inoculated worm eggs developed into adult worms in all pigs. This showed that the method used to infect the pigs was highly effective.

The resulting number of worm-infected pigs were similar for the herb supplemented and the unsupplemented treatments (5-6 pigs out of 8), while the treatment with flubendazole resulted in 0 infected pigs (>> Table 1).

Whereas the number of worm infected pigs was similar, addition of the herb mixture to the diet almost significantly reduced the number of worms per infected pig (48 vs 23) compared to unsupplemented diet (>> Table 1). Yet, addition of herb mixture plus black tea did not affect the number of worms per infected pig compared to unsupplemented diet. Likewise, the percentage of adult worms did not differ between treatments (>> Table 1).

Possible effects on adult worms

The tested herb mixtures significantly increased the phenolic and tannin content of the feed, thereby providing a basis for control of Ascaris suum. Yet, no effect on the number of worm positive pigs was found, whereas the number of worms per infected pig was only non-significantly reduced.

These findings did not accord with the results of Van der Gaag et al. (2004), although herb mixture and number of inoculated worm eggs were similar in both experiments. Thus, Van der Gaag et al. (2004) found a significant effect of herb mixture, tested in concentrations 1% and 5%, on reduction of percentage worm positive pigs as well as the number of worms in the small intestine of worm positive pigs.

The reason for the differences in both findings are not fully clear. Yet, in the experiment of Van der Gaag et al. (2004), herb supplemented diet was fed until the end of the experimental period (day 77), while we stopped feeding herb-rich diet at day 39. We stopped earlier, because we expected only a positive effect of herbs on worm burden during the first two weeks after egg inoculation, during the developing phase from egg to adult worm. Probably, the tested herbs could have an anthelmintic effect on adult worms, or the immune system of the pig was more triggered by long term feeding of these herbs.

Possibilites for practical implementation

On organic farms with a low worm infection probably a combination of a conventional synthetic drug and a diet with herb mixture containing 1% Thymus vulgaris, 1% Melissa officinalis and 1% Echinacea purpurea is an option. However, it depends on the level of worm infection whether it is an opportunity to deworm the pigs with a diet containing the herb mixture to keep the level of Ascaris suum at an acceptable low level.

Examination of faeces of sows, weaners and growing and finishing pigs regularly, and also the percentage of disapproved livers of growing and finishing pigs, can support to monitor the level of worm infection on the farm. Based on this monitoring probably a strategy of varying deworming with a synthetic drug and a diet with herb mixture can be developed for the different categories of pigs.


Van der Gaag, M.A., T. Schuurman, F.H.M. Borgsteede en C.P.H Gaasenbeek, 2004. Kruiden effectief bij bestrijding wormen. Praktijkkompas (Jaargang 18) Nr. 2.

Van Krimpen, M.M., G.P. Binnendijk, F. Borgsteede and C. Gaasenbeek. In vivo testing of alternatives for conventional treatment of Ascaris suum in pigs. Report XX. Animal Sciences Group, Wageningen UR. http://orgprints.org/14950/