Strategic Dosing - Sheep and Goats

                                   

As winter approaches in South Africa many farmers believe that the worm problem associated with the humid and often hot summer months will be drastically reduced with the decreasing temperatures. 

While this may be true, winter is not without its worm challenges. This said, flukes (conical and liver flukes), roundworms (Brown stomach worm, Bankrupt worm (Long necked), White bankrupt worm, over wintering roundworm and nasal bots larvae’s are some of the worm burdens your stock has to deal with during the winter period.

 There is increasing recognition that larvae arrest in development as a result of prior experience of certain climatic or seasonal influence, a phenomenon referred to as hypobiosis.  Low or zero egg counts in winter is therefore no assurance that there exists a low or no worm burden. These hypobiotic larvae will continue from their arrested development when favourable environmental conditions ensue:

     ·         During the next spring or,

    ·      When host (ewe) immunity around the next lambing time is reduced – a “normal” occurring phenomenon that we need to manage. 

Winter is also a critical time for ewes, most of whom are pregnant during a period often characterised by poor grazing quality and harsh weather conditions. Ewes are required to maintain and grow the foetus inside them – especially during the last third of pregnancy. Closer to term, there is an increased nutrient requirement towards formation of colostrum. An increased winter worm burden will, despite improved nutrition, erode on the ewe’s body condition (fat reserves), increase the risk of poor oöcyte (egg) quality and conception, decrease the quality of colostrum and put the newborn at risk. Additionally, anaemia, poor growth and diarrhoea are also seen in winter due to worm problems.

The fact pointed out above should make “pre-winter strategic dosing” an essential component of any farm’s integrated parasite management (IPM) system. Farms applying a “before winter strategic dosing” dose all their animals usually in May, after the frost, when there is little or no re-infection of the animals from the pasture. 

Using the correct remedy, pre-winter strategic dosing should achieve the following:

• Eliminate nasal bot larvae in the sheep when there are no longer free living flies around that lead to re-infestation. Pre-lambing dosing against nasal bots is important as we need to ensure that the ewe can identify her lamb after birth by olfactory means. Similarly, rams are more efficient in detecting ewes in oestrus when nasal cavities are free of bots and the mucus secretion this infestation causes    
• Remove hypobiotic roundworm larvae (positive egg count is therefore not a requirement for dosing).