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Controlling parasitic infection & pneumonia in growing and finishing beef cattle

In suckler herds, calves generally remain with the cows at pasture until they are weaned between six and nine months old. In addition to removal from the cow, the weaning procedure may be compounded by other stressors occurring around the same time, e.g.

  • change of diet - grass and milk to conserved feed with or without concentrates
  • change of environment - outdoors to indoors
  • transport/marketing.

Weaning therefore can be a multi-factorial stressor, in which, nutritional, social, physical, and psychological stress are combined. Psychological stress is present in the form of maternal separation and social disruption, whereas nutritional and physical stressors are often present through the introduction and adaptation to a novel diet and environment. Research at Teagasc, Grange has shown that reducing the cumulative effect of multiple stressors around weaning time results in a less marked stress response in the calf.

Dairy calves, in contrast to suckler calves, are commonly separated from their dam a few hours after birth. In grass-based dairy-beef steer production systems, spring-born calves are typically offered milk replacer plus concentrates over an indoor rearing period of 8 weeks, turned out to pasture in May, and housed at the end of the grazing season (October/ November).

During the ‘first’ indoor winter (‘store’) feeding period, both suckler-bred and dairy-bred animals consume a restricted-energy diet based on grass silage and supplementary concentrates. This is followed by a ‘second’ grazing season (February/March to October/November) where they can exploit compensatory growth.

Some animals, primarily heifers and earlier maturing breed types, are finished towards the end of this second grazing season. During the ‘second’ indoor winter period animals are offered grass silage and concentrates, and some animals are finished at approximately 24 months of age. Animals not finished at the end of the second grazing season or during the second winter are returned to pasture from where they are finished at approximately 28 months of age.

An optimal herd health programme should be designed to prevent major disease and it is important to consult with a veterinary practitioner prior to weaning and/or purchase of finishing cattle to discuss the prevalent diseases and associated risks specific to the farm. Respiratory disease (pneumonia) and internal parasites (stomach worms, lungworm (hoose) and fluke) are among the main health concerns affecting weanlings and older cattle.

Control of stomach worms, lungworm and fluke

Parasite control programmes, encompassing internal parasites such as gutworms, lungworm and fluke along with ectoparasites such as lice and mange mites, should be developed in consultation with a veterinary practitioner. The programme should consider all parasite challenges and be designed for holistic and sustainable parasite control on the farm.

Lice and mites

During the winter housing period the major parasites of concern are often ectoparasites such as lice and mites. These parasites increase during the winter months due to higher stocking densities, longer coats and the low amount of UV light. Signs of infestation include:

  • itching
  • hair loss
  • skin lesions
  • poor thrive.

These ectoparasites are usually controlled by the administration of synthetic pyrethroids or injectable or pour-on macrocyclic lactones - clear wormers. While all products both injectable and spot or pour-on are effective against mites and sucking lice, only topical products are effective against biting lice.

Round worms and fluke

When turned out to grass the following spring, the major parasites of concern for the second grazing season include roundworms, i.e. gutworms and lungworm, and fluke, including rumen and liver fluke. Cattle develop immunity to roundworms over time, relatively quickly in the case of lungworm and over 1-2 grazing seasons in the case of gutworms. In contrast, there is little evidence that cattle develop immunity to fluke infection and these remain a threat throughout the animal’s life.

In their second grazing season yearlings should have some immunity to roundworms. Immunity may be stronger in the case of dairy calves than in suckler calves as a higher proportion of their diet in the first grazing season came from grass, resulting in higher exposure to these worms. If roundworms are well managed in dairy calves in the first grazing season, allowing sufficient exposure for immunity to develop, then they are unlikely to be a major issue in the second grazing season.

In contrast, suckler progeny may be at greater risk of disease or ill-thrift due to roundworms in their second grazing season because of their relatively limited exposure to worms in their first year of grazing. Such animals should be monitored for signs of lungworm (hoose) such as coughing and gutworms (scour and poor thrive). Due to the build-up of at least some immunity, second season grazers are more likely to experience sub-clinical disease due to gutworms than clinical disease.

Monitoring animal performance will help identify any issues. This can also be combined with laboratory testing, such as examination of faecal samples for gutworm eggs, to determine if and when animals need to be treated. Chemotherapeutic control of roundworms is dependent on the availability of broad-spectrum anthelmintics or ‘wormers.’

Anthelmintic resistance

In recent years anthelmintic resistance has been detected on cattle farms in Ireland. Anthelmintic resistance refers to the ability of a worm to survive a dose that should kill it. Resistance has been detected in Ireland among gutworms to all three classes of anthelmintics available:

  • the benzimidazoles - white wormers
  • levamisole - yellow wormers
  • macrocyclic lactones - clear wormers

Therefore, it is important to know what wormers work on the farm before choosing which product to use.

Liver fluke and rumen fluke

The flukes, liver fluke and rumen fluke, can also cause disease in grazing cattle. In the case of rumen fluke, they appear to be usually well-tolerated. Large numbers of larvae in the intestine has been associated with clinical disease which can manifest as rapid weight loss and severe scour. If untreated it can be fatal.

Of far greater concern is the liver fluke. Liver fluke disease, caused by Fasciola hepatica can result in anaemia, poor thrive or loss of weight/condition. Liver fluke has a seasonal, indirect lifecycle with both animal and snail hosts. Eggs passed out onto pasture in late spring by infected animals hatch into miracidia, which infect mud snails where they multiply. After about 6 weeks, cercariae are released from the snail host and encyst on the grass as metacercariae. Therefore, the major risk period for fluke is from late summer/autumn onwards. When infective metacercariae are eaten by grazing cattle the newly excysted juvenile fluke burrow through the gut wall and migrate to the liver, a process that takes about two weeks. Over the following eight to 10 weeks the immature fluke migrate through the liver where they can cause extensive damage, ending up in the bile ducts where the mature fluke lay eggs that are passed out with the dung.

The effect of weather and ground conditions on disease prevalence is well known with warm, wet weather providing ideal conditions for the intermediate mud snail host. This enables the Department of Agriculture Food and the Marine (DAFM), in conjunction with Met Éireann, to produce a liver fluke forecast each autumn predicting the risk of disease. Avoiding grazing particularly wet areas of the farm in autumn will help reduce exposure to liver fluke. In addition, the DAFM fluke forecast, farm history and liver report information, such as from the Animal Health Ireland Beef Health Check Programme, can help to ascertain liver fluke exposure.

Housing represents a good opportunity to control fluke. However, there are different products on the market, which kill fluke of different ages. It is important to target the treatment to the appropriate stage of the parasite. Products that target early immature and immature fluke can be used in the weeks after housing while products that target adult fluke are more suitable for use in spring, before turn-out.

Prevention of pneumonia/bovine respiratory disease

The sourcing of cattle from multiple sources and housing them together within the same airspace almost invariably leads to respiratory disease. Take steps to protect your animals and your profits by “conditioning” animals prior to housing, controlling the animals’ environment, vaccinating your animals against respiratory pathogens and taking steps to exclude pathogens from your farm.

The primary cause of pneumonia (respiratory disease) in weanlings is initially attributable to viruses such as bovine herpes virus-1 (BoHV-1/infectious bovine rhinotracheitis (IBR)), bovine respiratory syncytial virus (BRSV), bovine parainfluenza-3 virus (BPI-3 virus), and in many cases is followed by secondary bacterial infections usually caused by Mannheimia (Pasteurella) haemolytica and Mycoplasma bovis. Bovine virus diarrhoea/mucosal disease (BVD/MD virus) was previously an important component of respiratory disease in weanlings, but its contribution now is minimal as a result of the national eradication programme.

Orla Keane, Bernadette Earley and Edward O’Riordan

Teagasc, Grange Animal & Grassland Research and Innovation Centre, Dunsany, Co. Meath