Larvae do not withstand hot, dry conditions well, thus, lower numbers of larvae would be expected to have survived on these pastures. Granted this is not always possible due to forage type available and number of pastures. After treating sheep for parasites, rotate to pastures that have been rested and should have lower numbers of infective larvae. Pastures that have been harvested for hay would be less likely to contain high numbers of larvae. Pastures that have had cattle or horses grazing them prior to grazing sheep, would be considered safe.
Lambs are the most susceptible class of sheep to internal parasite infections.
Because of their age, stage of growth and lack of a developed resistance, they can develop high levels of infection. Therefore, it is imperative they have access to the cleanest pasture possible and are monitored closely for infection. Summary Prevention of a problem with internal parasites in sheep through strategic treatments, proper drug use, working with a knowledgeable veterinarian and employing sound pasture management is the key to control. Waiting until anemia, scours, lack of thrift and growth are present before treatment is ineffective in solving the real problem. Preventing pasture contamination is the most cost effective method of parasite control.