Grazing management

Effective grazing management reduces the exposure of goats to worms.

There are four basics:

• Avoid paddocks heavily contaminated with worm larvae
• Reduce contamination of paddocks with worm eggs
• Allow time for most of the eggs and larvae on the pasture to die
• Where possible, encourage goats to browse as much as possible

Figure 1. Grazing management can significantly reduce the level of worm larvae on pastures. Source: Trevor Waterston and Shelly Gatt, Valley View & Bichance Dairy Goat Studs.

Alternating grazing of goats with cattle or horses

Alternating grazing between cattle and goats is an effective means of reducing worm infection because most worms are host-specific. That is, most worms are only able to successfully infect either goats or cattle, not both, and ingestion by the non-preferred host results in death of the larvae. Sheep and alpacas should not be used as they share common parasites with goats.

Notable exceptions are the ability of barber’s pole worm and stomach hairworm (Trichostrongylus axei) to successfully reproduce within goats and young cattle (i.e. pre-weaning). Using dry adult cattle for alternate grazing is preferable, but large benefits still arise from using cows and calves and this should not prevent their use for this purpose.

Goats can also be severely infected by brown stomach worms (Ostertagia ostertagi) from cattle, unlike the situation with sheep and lambs.

Grazing with cattle represents a period of rest for the paddock from goat grazing, during which the number of infective larvae on pasture declines because larvae continue to die. The same periods of cattle grazing, as described below for grazing management rest periods (40–80 days), are required to gain sufficient benefit for worm control in goats but will also depend on the type of worm, the temperature and humidity, and the stocking rate of cattle.

Horses are ideal for alternating grazing with goats as worms are not shared between goats and horses.  If numbers of goats are small and horses are used on the farm, then this may be a useful tool.   

Rotational grazing

The value of rotational grazing management as an aid for worm control is based on:

• Graze periods in a paddock being sufficiently brief (less than 4–10 days depending on temperature) to avoid autoinfection (see life cycle page); and/or
• Rest periods (i.e. the interval between consecutive grazing in a paddock by goats or sheep) long enough to have allowed enough time for many of the larvae on the pasture to die. Typically these need to be 40–80 days depending on temperature (see life cycle page and ‘Factors contributing to paddock contamination with worms’)

There are a number of approaches to rotational grazing that differ in the time used for graze and rest periods. Faster growing pasture will require a shorter rest period between grazing events, while slower growing pastures require a longer rest period; the longer the rest period, the longer the graze period.

Choosing the period of grazing and rest is a balance between worm control and pasture utilization. Information on grazing management is available at:

• Technograzing
• Holistic management
• Grazing management
• Evergraze

Rotational grazing has been demonstrated to reduce barber’s pole worm infection in summer rainfall regions with goats.

Differences between worm species

The benefit of rotational grazing for worm control is greatest for barber’s pole worm because development from egg to infective larvae cannot be delayed and larvae do not remain in the dung pellet, but quickly emerge onto pasture. There is also benefit for control of scour worms, but the survival of these worms on pasture is prolonged because they can delay development and remain in the faecal pellet. In winter rainfall regions there can be a delay of several months between eggs being deposited in the dung and the appearance of scour worm larvae on the pasture.

Control of scour worms in winter rainfall regions is greatly assisted by the integration of effective drenching followed by brief periods of intensive grazing (see 'Smart Grazing'). This approach also has benefit in the summer rainfall region.

Pastures for goats

Goats evolved as browsers and should be encouraged to browse as much as possible.  If a goat is eating with its head up it is not ingesting worm larvae as they can’t move that high. 

Most worm larvae are in the first 5 cm off the ground arriving there by random wriggling on moisture provided by dew.  Very few larvae are on grass stems that are above 10 cm in height.  Above 15 cm there is almost no worm larvae.

Because goats are less resistant to worms than sheep, higher stocking rates, especially when it exceeds the carrying capacity of the pasture, are likely to increase worm infection and compromise welfare.

Figure 2. Infective larvae are not often present above 15 cm, most are found below 5 cm where the humidity is higher. Source: Dr Sandra Baxendell.

Figure 3. Vertical and horizontal movement of infective larvae on vegetation. Source Vlassoff 1982.

Figure 4. Browsing on vegetation free of infective worm larvae. Source: Dr Sandra Baxendell.

Grazing with goats when eggs cannot develop to larvae

In lengthy periods of cold, heat or dry, worm eggs cannot develop to infective larvae. In these periods, pastures to be prepared as low worm-risk paddocks, can be grazed by goats regardless of their worm burden. The conditions and time required for this strategy will depend on the worm species (see 'Factors contributing to paddock contamination with worms').

This is a particularly successful strategy in the northern tablelands of NSW where a 4-month cold period is exploited. This only requires the paddocks to be actively managed (through spelling, grazing with cattle or ‘Smart Grazing’) in the 2 months prior to winter, so as to give a total of 6 months in which existing larvae are dying before being used as a low worm-risk spring lambing paddock.

In Mediterranean-climate areas with hot, dry summer months, the paddocks can be almost completely worm-free by the autumn break—particularly in areas of South Australia and Western Australia.

To find out how you can use grazing management to improve worm control on your property, follow this link to the WormBoss Worm Control Program for your region.