Internal Parasites and Immunity in Ruminant Cattle: How to Strike a Lasting Balance?

The fact that ruminants live in coexistence with parasites is normal as parasites naturally belong to their environment. The balance between a host and its parasites reflects the actual opposition between a herd and its parasitic environment. Paradoxically, the upkeep of this relationship is indispensable to the optimal expression of these animals' performance. Disrupting this balance could lead, at best, to decreasing the efficiency of the diet, and at worst, to mortalities. The application of a sustainable approach can help to establish an effective immunity. It also results in shaping an environment that becomes hostile to parasites. This seems easy in theory, yet how can we implement it in practice?

Appetite and weight losses, intestinal disorders... Parasitic infestations in cattle, goats and sheep can lead to serious issues in the event that parasites proliferate. The obvious signs of their invasion range from a mere drop in production to the appearance of genuine pathological diseases. As an example, growth losses in cattle fluctuate between 80-150 g of average daily gain (ADG) for young adults; their daily milk production can drop from 0.5 to 2 liters of milk.

Knowing the different kinds of parasites at stake to be able to control them

To live in a state of balance with one’s enemy, one must be able to master this enemy. The implementation of a sustainable approach is not just based on a mere protocol. Interfering at the right moment requires that the concept of parasite growth be taken into account. A parasite’s life cycle thus consists of four essential stages:

• The first phase is hatching: parasites’ eggs are shed by animals’ dejection
• Then comes the ingestion phase. The larva matures in the meadow, until it is ingested by a specific animal or by an intermediate host.
• Migration: when it has been ingested, the larvae migrate towards its targeted organs; it then fixes itself onto this organs to finish growing. Each organ has his specific parasite: rumen (paramphistome), liver (liver fluke), stomach or intestine (gastrointestinal strongyles);
• This finally leads to expulsion: the eggs contained in cow’s dung are shed in the meadow; these then soon become ready to hatch.

These stages have varied lengths depending on the parasite concerned. A complete cycle lasts for about 21 days when it comes to strongyles, 3 months for paramphistome and more than six months for liver flukes. The period during which these actions can be set up depends on the accurate identification of the parasite at stake.

Immunity as a way to trust natural defenses

Where shall we begin? First, we will attempt to support the animal immunity, by activating a positive immune response in the animal’s body. This relates to the natural defense mechanisms that ruminants deploy against internal parasites in their environment. The success of this action will depend on the upkeep of a continuous contact with the parasite at a moderate level, and by the supply of a balanced diet. Remember that we must intervene at the right time of the parasite’s life cycle. Indeed, animal immunity takes several months to build up. It eventually results in the production of specific antibodies against the parasites at stake.

How can we maintain a good balance between the parasite and the animal host?

Maintaining a good balance between the host and the parasite can help to reduce performance drops in ruminants. Reducing the risk rather than treating the source of disease better fits in what is termed a ‘sustainable approach’; this method is actually a lot more profitable than the first option.
Here are a few guidelines for achieving this goal:

• at the nutritional level, we must ensure that the diet is well balanced, especially regarding the variations caused by the long grazing periods (copper, magnesium ...);
• at the grazing level: rotational grazing and the restricted access to water meadows contributes to limit the levels of infestation;
• at the environmental level: an environment that hinders the development of parasite cycle becomes hostile to the parasite.

Farmers must constantly adjust their methods to anticipate the worst risky periods. Some nutritional products have been specially designed to support animals' immunity in these trying periods. If these are administered in a timely manner, they can contribute to limit performance declines. They can also help to reduce the risks of resistance development and of immunity breaks in the event of anthelmintic treatment.

If you want to tailor your strategies regarding parasite risk management by stimulating the natural defenses of your animals, our experts are here to help you; please do not hesitate to consult them!