31 March 2022
Dr Emma Davies: IBERS, Aberystwyth University.
- An awareness of the risk factors associated with increased calf morbidity and mortality is very important so that management strategies that mitigate these risks can be employed.
- The primary strategies to improve suckler herd health focus upon reducing dystocia, good colostrum management, the prevention of disease, and good hygiene and biosecurity. These strategies will also help to reduce antibiotic use.
- Developing and regularly reviewing a health plan with the farm’s veterinarian is crucial to ensure the best health strategies for the herd are in place and are working effectively.
Introduction
The performance of a suckler beef herd is significantly impacted by poor cow and calf health. Poor health may be caused by a range of factors, such as poor nutritional management, sub-optimal housing environments, or increased disease prevalence. These factors may manifest in reduced calf growth, increased cow and calf morbidity and mortality, or increased veterinary costs, potentially resulting in severe economic consequences.
Many farmers in Wales are looking to improve the health of their herd around calving. One European Innovation Partnership project is supporting a group of farmers in Carmarthenshire and Ceredigion to develop management strategies to improve the health and performance of their beef herds and to reduce their antibiotic use. The strategies, developed with the farm’s veterinarians, will include improving ration formulations, increasing colostrum quality and absorption, and preventing the incidence of infectious diseases. A framework to assist decision making regarding antibiotic use will also be used.
Calf mortality
A high calf mortality rate is one of the most significant indicators of poor health and welfare within a suckler beef herd. The average mortality rate for suckler beef calves following birth is 3-6%. The risk of calf mortality is greatest in calves younger than 3 months of age, with approximately 50-55% of calf deaths occurring in the first two weeks of age. The risk factors associated with increased mortality in calves include dystocia (a slow or difficult birth), having a small birth weight, and being born during winter or early spring. The age and parity of the dam also has an effect.
Calves that experience dystocia are at a greater risk of mortality due to an increased risk of physical injury and an increased length of time taken to stand and suckle. Calves that have experienced dystocia are also more likely to have a weaker suckle reflex. These effects result in the consumption of colostrum being delayed, further resulting in reduced antibody absorption and a reduction in the effectiveness of passive immunity transfer between the cow and calf. Calves with a greater risk of dystocia include bull calves, twin calves, and calves born to primiparous (first calving or first parity) dams. One study found that 51.2% of calves born to primiparous dams required assistance during calving, compared to 29.4% of calves born to dams with a parity of 3-5.
The risk of mortality in calves between 1-5 months of age also increases for calves born to primiparous cows. In addition to the increased risks associated with dystocia, this may be due to younger cows having lower milk yields and lower colostrum antibody concentrations. For calves younger than 30 days of age, the risk of mortality has also been found to increase when a calf is born to a dam with a parity higher than five. This has been attributed to older cows being more likely to have a lower overall health status, and the high dependency of the calf on this health status in the first few months of life.
While calves born with low birth weights have a lower risk of dystocia than calves with large birth weights, during the early post-natal period a large birth wight is a protective factor, as calves tend to be more vigorous and resistant to adverse environmental conditions. Calves born in winter and spring have a higher mortality risk than calves born during the summer, due to low ambient temperatures, greater fluctuations between day and night time temperatures, and increased precipitation.
Calves born in winter are susceptible to adverse weather conditions and have an increased risk of mortality than calves born during the summer.
Newborn calves are immunologically naive and are highly susceptible to disease. Following dystocia, the most commonly reported reasons for calf morbidity and mortality include digestive disorders and infectious diseases, such as diarrhoea and pneumonia. Neonatal diarrhoea is commonly caused by viral infections with agents such as bovine viral diarrhoea virus (BVDV), bovine rotavirus (BRV) and bovine parvovirus (BPV). However, parasitic infections with intestinal helminths and protozoan parasites such as Cryptosporidium parvum and Eimeria species that cause cryptosporidiosis and coccidiosis respectively, are also common causes. Respiratory infections in calves are often multifactorial, as viral infections often precipitate severe bacterial pneumonias. Viral respiratory infections in calves can be caused by a wide range of viruses, such as bovine herpesvirus-1 (BHV-1), parainfluenza virus-3 (PI-3), and bovine respiratory syncytial virus (BRSV). The BVDV is also well-recognised as a major pathogenic factor in respiratory infections, as it results in calves being immunosuppressed, increasing their susceptibility to secondary bacterial infection. Bacterial and mycoplasmal infections are often caused by commensal organisms that become pathogenic following a period of acute stress (including viral infection or poor management, handling, or environmental conditions). Common bacterial organisms implicated in the pathogenesis of respiratory infections in calves include Mycoplasma bovis, Mannhaemia haemolytica, Pasturella multocida and Histophilus somni, amongst others.
Other common bacterial infections in calves are caused by the entry of bacteria into the bloodstream, from either the umbilicus, the upper respiratory tract, or the digestive tract. This can result in a range of conditions such as omphalitis (navel ill), septicaemia, peritonitis, or infectious polyarthritis (joint ill).
Managing calves to improve herd health
The incidence of digestive and respiratory illnesses needs to be managed to improve the health and survivability of young calves. Whether calving indoors or outdoors, calves need to be born into a clean environment and receive an adequate colostrum supply to combat the pathogenic challenge from viral, bacterial and parasitic agents.
Colostrum
Calves should be checked immediately after birth and should be observed to ensure they can stand and suckle. As inadequate colostrum consumption has been identified as a major risk factor for infectious disease, making sure calves receive a colostrum supply of adequate quality and volume is vital to ensure calves acquire passive immunity. Particular focus on calves born to primiparous cows is important as primiparous cows are at greater risk of dystocia, reduced colostrum volume and reduced antibody concentration.
To maximise passive antibody transfer calves should consume at least 3 litres of colostrum in the first 2 hours of life and consume 10% of their body weight within the first 12 hours of life, before the intestinal absorption of antibodies ceases 24-36 hours after birth. Obtaining an accurate calf birth weight will help estimate how much colostrum the calf requires, and a sample of colostrum can be taken to estimate colostrum quality. To determine if calves consume enough colostrum naturally, it's estimated that one litre can be suckled in approximately 10 minutes. Therefore, calves should suckle for a combined total of 25-30 minutes in the first two hours of life to consume 3 litres of colostrum, with subsequent suckling thereafter. If a calf is unlikely to have consumed enough colostrum naturally, suckling can be assisted, or colostrum can be fed directly to the calf using a bottle or stomach tube. When feeding 3 litres of colostrum, bottle feeding and stomach tubing methods result in comparable levels of serum antibody levels. However, when feeding volumes of 1.5 litres or less, feeding with a bottle is preferrable as this is more likely to promote closure of the oesophageal groove, and effectively deliver colostrum directly to the abomasum, maximizing antibody absorption. Colostrum can be collected from the dam following parturition, or supplementary colostrum from another cow or an external supply can be provided. Colostrum can be assessed relatively easily using a colostrometer or refractometer, and a good quality colostrum has an IgG concentration of >50g/L. If supplementing colostrum it is essential that the supply is handled as aseptically as possible to reduce bacterial contamination.
It is essential for newborn calves to consume an adequate quantity of colostrum within the first 12 hours of life. Colostrum quality can be estimated using a colostrometer (right).
Housing
Strictly maintaining a clean housing environment is essential to maximise calf health. Housing areas should be thoroughly mucked out and disinfected before being used and between occupants. All general good hygiene measures, including the provision of adequate quantities of dry clean bedding, clean water supplies that are regularly disinfected, and clean feeding areas that prevent forage from becoming contaminated should be adhered to. If cows are housed together and calve in a small area then moving cow and calf pairs from the calving environment to a nursery area within 48 hours has been shown to reduce calf losses, as overcrowding in the calving area is prevented. The management of drainage and air flow is also extremely important as increased humidity and poor ventilation can contribute to increased disease prevalence. Housing areas should have enough air flow to ensure the air is always fresh, without leaving calves susceptible to draughts.
Similar management considerations are also important for calves born outdoors. Stocking density should be low enough so that field conditions remain hygienic, with adequate ground cover, good drainage, and no muddy areas. If providing additional feed, then feeding sites should be moved frequently and artificial water sources should be disinfected regularly. When outdoors, young calves also need to be protected from extreme environmental conditions. This can be achieved with the provision of open field shelters suitable for both the calf and cow, since the calf is unlikely to leave its mother to seek shelter when very young. Additionally, since a summer birth has been identified as a protective factor against mortality in calves up to 5 months of age, a long-term breeding strategy can ensure calves are born in late spring and early summer months.
Insulated calf jackets are commonly used in the dairy sector to keep calves warm and dry, particularly in periods of cold weather. This is important as in cold conditions, calves need to expend energy to maintain their body temperature. This means less energy is available for growth and immunological function, leaving calves at an increased risk of disease. While calf jackets may not be practical or beneficial in all suckler herd scenarios as calves have ad lib access to milk and their mother’s body heat, calf jackets may be extremely beneficial when used on vulnerable calves, such as those that have experienced dystocia, have had little colostrum, or are already ill.
Other important management considerations
Treating the umbilical cord with a suitable disinfectant, such as a 7% iodine solution immediately after birth is vital to prevent bacterial infection of the umbilicus. Other management factors such as the method of castration in bull calves has also been shown to affect calf health. One study found that the use of small elastrator bands applied within the first two days of life increased the risk of diarrhoea by 2% and increased mortality during the first week of life by 1.4%, when compared to other methods used after two months of age.
Studies have also found that the mortality risk for calves and youngstock increase with increasing herd size. This is attributed to an increased risk of disease transmission amongst larger groups and an increased prevalence of pathogenic organisms as the calving season progresses. Therefore, stocking strategies should ensure that calves of significantly different ages are housed separately, and that the mixing of individuals and groups is minimised. This is especially important when bringing in replacements, as herds with cattle purchased in the month before calving experience higher mortality rates than herds that have remained stable.
Whether indoors, or outdoors, strict biosecurity protocols should be followed to reduce the transmission of disease between farms, and between different groups of livestock. This includes regular disinfection of personnel and equipment. Cow and calf pairs should also be kept separately from all other youngstock, including cattle and sheep, and direct contact between these groups through field boundaries should be prevented. If a calf does become ill, then it’s important that the cow and calf are separated from the herd to reduce the transmission of infectious disease.
In the case of suspected illness, it is vital that farmers consult their veterinarian so that an accurate diagnosis can be made, and the best treatment can be given in accordance with veterinary advice. Veterinarians can also help develop robust vaccination protocols, parasite control programmes, and offer advice regarding biosecurity. For example, an increasing number of suckler beef farmers now determine the BVDV status of their own herds, conduct pre-purchase tests for BVDV and Johne’s disease, vaccinate breeding stock against BVDV, infectious bovine rhinotracheitis, Leptospira species, and Salmonella, and vaccinate calves against common clostridial and respiratory pathogens. Farmers in Wales are able to participate in the Gwaredu BVD scheme which provides access to funding and support from professionals to eradicate BVD from herds.
Managing cows to improve herd health
The highest mortality risk for cows occurs in the first 30 days post-calving, with the risk for primiparous cows being greater than for multiparous cows. One study found that for primiparous cows, the risk of mortality was greater when cows experienced their first calving over 44 months of age than when compared to cows less than 36 months of age. Additionally, in multiparous cows, the lowest mortality risk occurred for cows with a parity of three to five but increased significantly with increasing parity beyond that. Other factors such as abortion and stillbirth also significantly increase the risk of mortality for cows, while dystocia significantly increases the risk of mortality in the first seven days post-calving.
Management strategies to decrease the risks associated with dystocia are very important for the survival of both the cow and the calf. A long-term breeding strategy focused on selecting heifers and bulls for calving ease is one way dystocia across the whole herd can be reduced. The risk of dystocia can also be mitigated by optimising the age at which a cow has her first calving. The education and training of farm personnel in the stages of parturition is also very important so that normal calving can be recognised, dystocia can be identified, and any necessary interventions can be quickly decided upon. Reducing the effects of dystocia by assisting in difficult calvings can also reduce the incidence of disease, as beef herds that never intervene at calving have an approximately 5% higher incidence of calf diarrhoea than those that occasionally do.
Other factors relating to nutrition have been associated with 25% of heifer and cow deaths in beef production systems, with conditions such as rumen tympany (bloat), myopathy (associated with vitamin E or selenium deficiency), nitrate toxicity and polioencephalomalacia identified. This highlights the need for careful nutritional management throughout the cow’s life, but particularly throughout pregnancy and lactation. Managing the diet to ensure cows have an optimal body condition score of 2.5-3 (on a 5 point scale) at calving is very important to reduce dystocia. However, any changes to body condition should be made during early pregnancy and never in late gestation. Effectively managing the energy, protein and mineral status of cows is also very important to ensure quality colostrum and milk production, and support a rapid post-partum recovery. Post-partum conditions such as a retained placenta, prolapse, and mastitis are commonly reported in beef cows, indicating that management strategies to increase the speed of recovery following parturition and to manage the transition period are extremely important.
Optimising the cow’s diet before pregnancy is important to ensure she calves with a body condition score of 2.5-3. Cows with a body condition score less than 2.5 (left) and higher than 3 (right) are at an increased risk of dystocia.
Summary
The first few hours immediately after calving are critical to the health and survival of both the cow and calf. Management strategies at calving focused upon reducing the impacts of dystocia, ensuring adequate colostrum consumption, and managing housing and environmental conditions are essential. Regular observation of the cow and calf in the first week of life is equally as important to ensure the cow has recovered from parturition and is exhibiting good maternal behaviour, and that the calf is receiving enough milk, is vigorous, and is not vulnerable to poor weather conditions. Regular observations also enable subtle clinical symptoms of disease to be detected early. Maintaining a close working relationship with the farm’s veterinarian is also crucial so that the best prevention and treatment measures can be put in place.
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