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Gut worms in adult dairy cows
- How do gut worms impact my milking cows?
- How to diagnose gut worms in my milking herd?
- Worming the milking herd
The roundworms Ostertagia and Cooperia are found in pastures across the UK and can infect cattle if they are grazed or fed fresh grass. These gut worms can cause disease in cattle, with severity of disease depending on the animal’s immunity to the worms. Young stock have little immunity and so are most susceptible, showing signs of scour and/or reduced growth rates – see ‘Gut worm and lungworm control in dairy youngstock' for more on this.
However, it is important not to forget the potential parasite burden in adult dairy cows – gut roundworms can significantly impact milk production, especially in high-yielding dairy cows, if they are grazed or fed fresh grass.parasites have a lesser effect on yield but can reduce milk fat yields. Ostertagia exposure is also associated with lower body condition score which in turn can have negative effects on cow health, lameness and fertility.1
How do gut worms impact my milking cows?
As discussed in the article about gut worms in dairy heifers,the roundworms Cooperia and Ostertagia can act individually or together to reduce appetite and feed intake, damaging the abomasum and small intestine to prevent cattle from efficiently extracting nutrients from their feed. As adult cattle have generally developed some immunity from grazing pasture as young stock they are less severely affected –however the reduction in appetite is thought to be the main cause of the reduction in milk yield.2
How to diagnose gut worms in my milking herd?
For monitoring young stock (both sheep and cattle) we generally recommend the use of faecal worm egg counts (FWECs) – counting the number of eggs per gram of faeces (pooled from several animals) to get an indication of worm burden in the group.
Unfortunately, FWECs are less useful in adult cows. This is because they have developed some immunity to worms, so although their immune system cannot completely prevent damage to the gut, it can minimise the number of worms which make it to the adult stage of their life cycle and reproduce.This means the number of worm eggs shed in adult cow faeces is generally much lower than in young stock and is less accurate when estimating worm burden of the individual or group.
A better assessment of exposure to worms is through measuring Ostertagia antibodies – these are produced by the cows in response to exposure to Ostertagia and can be measured either in blood or milk. A bulk milk test is commercially available and in grazing dairy herds can be very useful in assessing effect of worm burden on the herd, as high levels of Ostertagia antibodies in the bulk tank are correlated with a reduction in milk production. On average, farms with a high level of Ostertagia antibodies in their bulk tank are likely to have a 1-2kg/cow/day reduction in milk yield.3 Farms with bulk tank results showing the very highest category of Ostertagia antibody level are likely to be losing 2-4kg/cow/day.4
For dairy cows grazing in the UK, it is usually beneficial to test the bulk tank for Ostertagia antibodies twice during the grazing season; firstly, at mid-grazing in July/August and secondly later on in the season when the weather has become wetter and the larval worm burden on the pasture is likely to be higher.
Worming the milking herd
Treatment decisions can be made from the results of Ostertagia antibody testing alongside clinical signs (if any) shown by individual cows:
· Low antibody levels – indicates that few of the cows whose milk is contributing to the bulk tank have had exposure to gut worms.If individual animals are looking poor then testing these animals individually for Ostertagia antibody may be useful, alongside a veterinary examination to check for other causes of poor body condition.
· Medium antibody levels – this indicates that some of the cows whose milk is contributing to the tank have had exposure to gut worms and that on average a decrease in milk production is likely. Depending on the clinical signs, age and stage of lactation, the herd may need worming or individual animals may need worming – your vet will be able to advise on this.
· High antibody levels – this indicates that the majority of the herd has been exposed to gut worms and on average the herd is likely to be losing >2kg/cow/day of milk. Worming the group is likely to be beneficial in this case.
Treatment options for milking cows are limited as many products are not licensed to be given to milking cows or dry cows/heifers within 60 days of calving. Eprinomectin products such as Epromec are highly useful as they have a zero-hour milk withdrawal so can be used in milking cows throughout milking and pregnancy. Epromec is also oil-based which makes timing your applications easier as rainfall before or after treatment won’t affect efficacy.
As well as focusing on treatment, herds which have evidence of gut worm exposure in their milking herd would benefit from discussing their Parasite Management Plan with their farm vet. This allows grassland management and cow health to be evaluated to find other ways to minimise worm burdens on the farm and reduce the need for treatment going forward.
References:
1. Springer A, Jordan D, Kirse A, et al.Seroprevalence of Major Pasture-Borne Parasitoses (Gastrointestinal Nematodes,Liver Flukes and Lungworms) in German Dairy Cattle Herds, Association with Management Factors and Impact on Production Parameters. Animals (Basel).2021;11(7):2078. Published 2021 Jul 12. doi:10.3390/ani11072078
2. Control of roundworms in cattle, COWS -https://www.cattleparasites.org.uk/app/uploads/2020/01/roundworm-140120.pdf
3. Charlier J, Claerebout E, Duchateau L,Vercruysse J. A survey to determine relationships between bulk tank milk antibodies against Ostertagia ostertagi and milk production parameters. VetParasitol. 2005;129(1-2):67-75. doi:10.1016/j.vetpar.2004.11.024
4. Charlier J, Duchateau L, Claerebout E,Vercruysse J. Predicting milk-production responses after an autumn treatment of pastured dairy herds with eprinomectin. Vet Parasitol. 2007;143(3-4):322-328.doi:10.1016/j.vetpar.2006.08.015
Gut worms in adult dairy cows
- How do gut worms impact my milking cows?
- How to diagnose gut worms in my milking herd?
- Worming the milking herd
The roundworms Ostertagia and Cooperia are found in pastures across the UK and can infect cattle if they are grazed or fed fresh grass. These gut worms can cause disease in cattle, with severity of disease depending on the animal’s immunity to the worms. Young stock have little immunity and so are most susceptible, showing signs of scour and/or reduced growth rates – see ‘Gut worm and lungworm control in dairy youngstock' for more on this.
However, In dual-purpose breeds these it is important not to forget the potential parasite burden in adult dairy cows – gut roundworms can significantly impact milk production, especially in high-yielding dairy cows, if they are grazed or fed fresh grass.parasites have a lesser effect on yield but can reduce milk fat yields. Ostertagia exposure is also associated with lower body condition score which in turn can have negative effects on cow health, lameness and fertility.1
How do gut worms impact my milking cows?
As discussed in the article about gut worms in dairy heifers,the roundworms Cooperia and Ostertagia can act individually or together to reduce appetite and feed intake, damaging the abomasum and small intestine to prevent cattle from efficiently extracting nutrients from their feed. As adult cattle have generally developed some immunity from grazing pasture as young stock they are less severely affected –however the reduction in appetite is thought to be the main cause of the reduction in milk yield.2
How to diagnose gut worms in my milking herd?
For monitoring young stock (both sheep and cattle) we generally recommend the use of faecal worm egg counts (FWECs) – counting the number of eggs per gram of faeces (pooled from several animals) to get an indication of worm burden in the group.
Unfortunately, FWECs are less useful in adult cows. This is because they have developed some immunity to worms, so although their immune system cannot completely prevent damage to the gut, it can minimise the number of worms which make it to the adult stage of their life cycle and reproduce.This means the number of worm eggs shed in adult cow faeces is generally much lower than in young stock and is less accurate when estimating worm burden of the individual or group.
A better assessment of exposure to worms is through measuring Ostertagia antibodies – these are produced by the cows in response to exposure to Ostertagia and can be measured either in blood or milk. A bulk milk test is commercially available and in grazing dairy herds can be very useful in assessing effect of worm burden on the herd, as high levels of Ostertagia antibodies in the bulk tank are correlated with a reduction in milk production. On average, farms with a high level of Ostertagia antibodies in their bulk tank are likely to have a 1-2kg/cow/day reduction in milk yield.3 Farms with bulk tank results showing the very highest category of Ostertagia antibody level are likely to be losing 2-4kg/cow/day.4
For dairy cows grazing in the UK, it is usually beneficial to test the bulk tank for Ostertagia antibodies twice during the grazing season; firstly, at mid-grazing in July/August and secondly later on in the season when the weather has become wetter and the larval worm burden on the pasture is likely to be higher.
Worming the milking herd
Treatment decisions can be made from the results of Ostertagia antibody testing alongside clinical signs (if any) shown by individual cows:
· Low antibody levels – indicates that few of the cows whose milk is contributing to the bulk tank have had exposure to gut worms.If individual animals are looking poor then testing these animals individually for Ostertagia antibody may be useful, alongside a veterinary examination to check for other causes of poor body condition.
· Medium antibody levels – this indicates that some of the cows whose milk is contributing to the tank have had exposure to gut worms and that on average a decrease in milk production is likely. Depending on the clinical signs, age and stage of lactation, the herd may need worming or individual animals may need worming – your vet will be able to advise on this.
· High antibody levels – this indicates that the majority of the herd has been exposed to gut worms and on average the herd is likely to be losing >2kg/cow/day of milk. Worming the group is likely to be beneficial in this case.
Treatment options for milking cows are limited as many products are not licensed to be given to milking cows or dry cows/heifers within 60 days of calving. Eprinomectin products such as Epromec are highly useful as they have a zero-hour milk withdrawal so can be used in milking cows throughout milking and pregnancy. Epromec is also oil-based which makes timing your applications easier as rainfall before or after treatment won’t affect efficacy.
As well as focusing on treatment, herds which have evidence of gut worm exposure in their milking herd would benefit from discussing their Parasite Management Plan with their farm vet. This allows grassland management and cow health to be evaluated to find other ways to minimise worm burdens on the farm and reduce the need for treatment going forward.
References:
1. Springer A, Jordan D, Kirse A, et al.Seroprevalence of Major Pasture-Borne Parasitoses (Gastrointestinal Nematodes,Liver Flukes and Lungworms) in German Dairy Cattle Herds, Association with Management Factors and Impact on Production Parameters. Animals (Basel).2021;11(7):2078. Published 2021 Jul 12. doi:10.3390/ani11072078
2. Control of roundworms in cattle, COWS -https://www.cattleparasites.org.uk/app/uploads/2020/01/roundworm-140120.pdf
3. Charlier J, Claerebout E, Duchateau L,Vercruysse J. A survey to determine relationships between bulk tank milk antibodies against Ostertagia ostertagi and milk production parameters. VetParasitol. 2005;129(1-2):67-75. doi:10.1016/j.vetpar.2004.11.024
4. Charlier J, Duchateau L, Claerebout E,Vercruysse J. Predicting milk-production responses after an autumn treatment of pastured dairy herds with eprinomectin. Vet Parasitol. 2007;143(3-4):322-328.doi:10.1016/j.vetpar.2006.08.015