​Maryland Small Ruminant Page

Since it can take a week to several months (depending upon the climate) for eggs to hatch and the larvae to become infective, the shorter the period of grazing, the less chance there is of a severe build-up of infective larvae. Short duration, high pressure grazing not only improves pasture utilization, but brings parasite control benefits.

 

If length of stay cannot be reduced, then the number of animals grazing a pasture should be reduced. Pasture contamination can be lowered by reducing the number of animals that graze a unit of land. The period of pasture rest is crucial to reducing the build-up of infective worm larvae. The period of rest required varies from one month to several months, depending upon climate and season.

 

Another way to remove infective larvae from a pasture is to graze the pasture with non-susceptible species, such as cattle or horses. Pasture "hot spots" increase the risk of severe parasitism and should be avoided. Examples of hot spots include grassed pens, marshy areas, and leaky water troughs. Sheep and goats are attracted to these better-watered and fertilized grazing spots.

 

Pasture fertilization improves pasture growth, but indirectly protects larave from dessication. Fertilization also improves pasture palatability which encourages intake, resulting in more infective larvae being ingested.

 

# 3 Pasture
 

Since pasture is the vector for transmission, it is essential that pasture factors be considered when developing a parasite control program. The risk of infection is dependent upon the height of the pasture. It is well known that the infectivity of pasture decreases in a logarithmic fashion as the height of the pasture increases. Short-cropped pastures carry an increased risk of pasture infectivity.

 

The type (species) of pasture affects the risk of parasitism.  Certain pasture species are more prone to spreading parasite infection. Other are not. For example, sericea lespedeza has been shown to contribute to parasite control.

 

The slope of a pasture affects run-off and therefore larval survival. Pastures with good drainage carry a lower risk of severe parasite infection as compared to poorly-drained paddocks. The direction that a pasture faces (aspect) also affects risk. Slopes that get less direct sun are cooler and will retain their moisture longer.  Extra water on pasture (e.g. irrigation) can increase risk. Soil type may have an effect on risk. Heavy, clay soils retain moisture more than light, sandy soils.

 

# 4 Monitoring

 

Though less useful for monitoring the parasite burden for indivdiual animals, fecal egg counts are useful for monitoring the infection rate on pasture.  Collecting pool samples every month is a good plan. Before and after fecal egg counts can be used to efficacy of anthelmintics. Individual animals should be tested.  Pooled samples can be used to test for anthelmintic resistance, if the samples are collected from the same animals both times.

 

The Five Point Check© and other criteria such as weight gain and milk production can be used to assess the effect of parasities on individual animals. The FAMACHA© system is the most extensively researched component of TST.

 

The weather (rain, humidity, and temperature) can be monitored to predict conditions which are favorable to larvae development. Unfortunately, there is no scientific model which indicates the level of risk.  Grazing conditions also affect risk of parasitism.

 

# 5 Treatment

 

Anthelmintics (drugs) are an essential component of TST. However, they must be used effectively and frugally to ensure their continued usefulness. Most anthelmintic resistance can be traced back to frequent and inappropiate use of drugs.

 

Targeted Selective Treatment (TST) and Targeted Treatment (TT) should be implemented on all farms. The FAMACHA© system is the most widely used component of TST. The Five Point Check© is a simplified extension of the FAMACHA© system for use against other major parasites. It is gaining acceptance in the sheep and goat industry.

 

It is important to follow drug labels.  Drug dosage should be based on weight. Most producers do not accurately guess the weight of their animals. Underdosing accelerates the development of resistant worms. If an automatic drench gun is being used, it should be set for the heaviest animals in the group. The gun should be checked for accuracy and repeatability.The most vulnerable members of the flock/herd should receive special attention, e.g. lambs/kids and lactating or heavy pregnant females.