The following information is informed by the May Parasite Forecast published by NADIS and is relevant for cattle producers in the UK only.
Young cattle in their first- or second-season at grass are at highest risk of parasitic gastroenteritis (PGE) and resulting production losses, caused by gutworm species. Reduced growth and failure to make average daily live weight gain targets is the most common sign of a gutworm burden, which makes regular weighing a useful monitoring tool.
Early in the grazing season, susceptible cattle become infected by over-wintered larvae from eggs that were shed onto pasture during the previous year. These larvae die off by early summer, but by this time infected cattle may be shedding significant numbers of eggs, which will hatch and contribute to a rapidly increasing pasture challenge.
It is important to treat youngstock with a suitable anthelmintic during the grazing season. Appropriately timed treatments will help to reduce contamination of the pasture as well as controlling worm-related production losses.
Making use of pasture not grazed the previous season, or moving animals to current season silage aftermath, will also reduce the worm burden in the latter part of the grazing season.
To prevent selecting for anthelmintic resistance, it is good practise to identify animals meeting growth targets and leave them untreated, while treating the remainder of the group. This ensures a mixed population of worm genetics are returned to the pasture without impacting the overall herd performance.
Cattle that grazed at-risk pasture and were not appropriately treated for fluke at housing, or were out-wintered, may be carrying an adult (chronic) fluke burden. These animals will now be shedding fluke eggs onto the pasture and may also be experiencing production losses.
Though cattle may not exhibit obvious signs of a chronic fluke infection, they may not be making growth rate targets, may have impaired fertility, or in lactating cattle, may have a reduced milk yield.
To stop ongoing pasture contamination and prevent costly production losses from chronic fluke disease, infected animals should be treated with a selective flukicide that only targets the later stages of liver fluke, such as TRODAX®.
If a worm treatment is considered necessary at the same time, IVOMEC® Super is a suitable combination product.
Lungworm disease is usually seen from mid-July onwards and where vaccination has not been used in susceptible herds, it is important to be alert for signs of disease.
Youngstock and adults with an unknown immunity status will be most at risk of disease. Vaccinated animals should still be monitored, especially later in the season if housing is delayed, since vaccine-derived immunity can be short-lived.
When developing a parasite control plan, remember that many products used for gutworm control also treat lungworm.
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