Managing worms in dairy cows

The main worm challenges for grazing dairy cows.^1,2

• Ostertagia ostertagi: The most clinically important. Causes parasitic gastroenteritis during the grazing season. Re-emergence of inhibited larvae cause type II ostertagiasis (severe often fatal diarrhoea) in late winter.
• Cooperia oncophora: Often the most common gutworm in the first grazing season. Causes parasitic gastroenteritis and can have a major impact on growth rates.
• Dictyocaulus viviparous (lungworm): Causes bronchitis and pneumonia resulting in persistent coughing, laboured breathing, weight loss and death in extreme cases. Can cause severe disease in adult animals where no immunity is present.

Immunity to worms²

Dairy cows naturally acquire immunity to gut and lungworms while grazing. This immunity is maintained by continual exposure while at pasture.

Immunity develops after one to two months for lungworm, three to six months (one grazing season) for Cooperia while exposure over two grazing seasons is required to develop immunity to Ostertagia.

Overwintered larvae die off as they run out of energy(a). Calves faced with a low-moderate challenge produce increasing numbers of eggs from 3 weeks after infection. Pasture larval numbers increase rapidly from July onwards(b) (exact timing weather dependent).

Two doses of Dectomax™, the first at turn out, the second eight weeks later, effectively manages gut worm burdens in the animal and on the pasture, giving optimum growth rates while allowing some exposure to worms to stimulate immunity.³

Lungworm

Lungworm risk is weather dependent but is generally highest from July to housing.¹ Pre housing treatment with Dectomax™ (up to 5 weeks before housing) can manage this risk and also remove inhibited Ostertagia to control the risk of Type II Ostertagiasis in late winter.