Merial has published figures which show that gutworm is seriously affecting dairy cow fertility in up to 80% of UK dairy herds1, in order to raise awareness of the damaging impact of Ostertagia ostertagi.
Sioned Timothy, veterinary adviser for Merial said: “The reduction in milk production from a gutworm infection is well documented2. Both animal health advisers (Suitably Qualified Persons – SQPs) and vets recognise the threat such infections cause. However, since cows often show no outward signs of disease, even in the face of a massive challenge, dairy farmers could unwittingly suffer heavy losses in milk yield, reduced fertility and increased heifer rearing costs at a time when they can least afford it.”
Merial points out that the extent of a herd’s gutworm exposure can be easily and simply assessed from a sample taken from the bulk milk tank – using the MOO Test. This test determines the amount of antibody to Osteragia ostertagi present in a sample, giving an assessment of the level of herd gutworm challenge.
The metabolic demands placed on cows during the post-calving period can lead to a negative energy balance, when energy gained from feed intake is less than that used for milk production. This natural ‘energy gap’ leads to weight loss; a parasite burden can make matters worse.
Sioned advises taking action to reduce the effect of this post-calving energy gap to maintain productivity levels. She said: “Management of cows in the weeks following calving should focus on maximising dry matter intake to correct the energy imbalance as quickly as possible. Studies have shown that cows treated for gutworm have improved appetites, and graze for up to an hour longer than untreated cows3. Grass is the cheapest form of nutrition so it makes sense to make the most of it.”
Merial also points towards studies which have shown that effective parasite control may have a beneficial effect4,5. Reduced body condition scores caused by the energy gap after calving may impact on reproductive parameters. In one study, cows treated for gutworm were back in calf 13 days sooner than untreated animals4.
Sioned said: "This has obvious implications for productivity. We need to look at employing a range of practical measures to ensure cows are as productive and efficient as possible, and this includes targeted worming where required.”
According to the company, effective parasite management of the replacement heifer during the rearing period is key to her future performance and productivity. Achieving breed-appropriate target weights throughout the rearing period is a crucial component of heifer rearing. The onset of puberty and the start of breeding are more closely linked to weight, body size and condition score than age. It is therefore critical to ensure that heifers reach approximately 60% of mature weight by 14 months of age in order to achieve a 24 month average age at calving.
Sioned said: “Losses in potential liveweight gain due to poor parasite control during a heifer’s first grazing season will not be recouped during the second year at grass6. She won’t catch up, and this will impact on her ability to meet important milestones.”
Getting heifers in-calf at the optimal time will help to reduce breeding costs and maximises the potential productive life of the animal. Heifers treated for gutworm have been shown to have a 20% higher conception rate at first service than untreated cattle2.
Merial says there is also evidence that parasite burdens exert physiological effects that directly impact on the parameters influencing performance and profitability of heifers, and increased mammary development and earlier onset of puberty have been observed in strategically wormed heifers in comparison to those left untreated7,8.
Sioned said: “Effective worming will mitigate the effect of parasites on fertility levels in growing cattle4, while still allowing them to build the necessary immunity required to prevent clinical disease in adulthood.”
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