Semi-arid Zone, Large Scale Ranches

Figure

Typical Problems In This Area

1. Due to the uneven distribution of rainfall during the year, there are times when grazing is in short supply and animals suffer from nutritional stress.

2. Worm burdens often build up slowly and coupled with poor feeding lead to a chronic condition.

3. Trichostrongylus, Haemonchus and Oesophagostomum can all be present and contribute to a generalised parasitic gastroenteritis.

4. During the dry seasons invading larvae may enter a period of delayed development in the animal (see Inhibited worms).

5. Although overall stocking rates may be low, these can be locally high around watering points and bomas.

6. SEVERE RISK OF DEVELOPING AND DISSEMINATING ANTHELMINTIC RESISTANCE.

Features Of The Area That Can Help In Control

1. Transmission is seasonal and a significant portion of the year is too dry for worm larvae to survive on pasture.

2. When inhibited worms are present, drug treatments can be efficiently targeted at these.

3. Overall stocking rates are low.

4. Presence of infrastructure can permit managed lambing and grazing management.

Control Methods That May Be Useful

· Frequent observation of individual animals and treating only clinical cases.

· Seasonal, treatments can be targeted at:

times of peak infection.
inhibited worms.
chronic infections.

· Crossing local breeds of animals rather than keeping pure-bred exotics can lead to sustainable production at lower treatment costs (Genetic Resistance).

· A Dose & Move system where all animals in the flock/herd are treated and moved onto clean ground.

· Regular movement of bomas can prevent local build up of infection on pasture (Boma Rotation).

· Use of narrow spectrum drugs can reduce the reliance on broad spectrum anthelmintics and slow the development of anthelmintic resistance