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INTRODUCTION Calves are born free of parasites. They pick up infection while grazing pastures harbouring the infective stages of these parasites i.e. the larvae and metacercariae (encysted stage of fluke that causes infections). Thus, turnout marks the start of exposure to parasites on pasture, such as:
1 2 3 Stomach and intestinal worms; collectively called gut worms* Lungworms* Liver fluke and rumen fluke*
When cattle are turned out, a combination of shorter summer coats, higher temperatures, less humidity and exposure to ultra-violet light leads to a marked decline in lice and mite populations - thus the control of these skin parasites is generally not considered an issue during the grazing season. * There are individual leaflets on each of these parasites available on the AHI website www.animalhealthireland.ie.
1 Gut Worms
Gut worms cause parasitic gastroenteritis (PGE)- clinical signs of which are diarrhoea and weight loss. Ostertagia and Cooperia are the two worms that cause most problems for Irish cattle. The control of gut worms depends on: 1. Grazing management 2. Good nutrition 3. Appropriate use of anthelmintics 1. Grazing Management
The objective is to reduce the concentration of infective larvae on pasture and so reduce the parasite challenge to grazing cattle. • New or reseeded pastures should have very low numbers of infective larvae initially. • Pastures that have not been grazed by cattle from the previous housing to mid-season (June/July) may carry lower numbers of infective larvae.
Ostertagia Type II.
• Pastures that have been grazed by sheep alone for 1-2 months should carry lower numbers of bovine infective larvae. • Pastures that have been co-grazed with sheep and cattle should carry lower numbers of bovine infective larvae. • Pastures subject to rotational grazing generally have lower numbers of infective larvae than those under continuous grazing. • Pastures that contain forbs, e.g. clover and chicory may carry lower concentrations of infective larvae than pure ryegrass swards. 2. Good Nutrition Appropriate supplementation of cattle diets at pasture can offset some of the negative effects of poor quality herbage and parasites.
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