25 Mar 2025
Tim Potter
Job Title
The importance of the correct management of dairy heifer replacements has been well demonstrated (Boulton et al, 2015), with problems in calf-rearing phases having long-term implications for the health, welfare and performance of the individual animal affected and ultimately for the profitability and sustainability of the dairy business.
It is also important we do not focus solely on the replacement heifers and, in line with the aims of the GB Dairy Calf Strategy 2020-2023, we work to ensure all dairy-bred calves are reared with care and for a purpose.
The GB Dairy Calf Strategy brought together farmer organisations, farm assurance scheme providers, vets, the supply chain, retailers, Defra and the Welsh and Scottish governments in a commitment to provide the best care for all calves and address the health and welfare issues surrounding dairy-bred animals – especially male Holstein-type calves. In a published progress report, the findings demonstrated significant achievements against the seven priority areas, and highlighted the progress that can be made from a collaborative approach to improving calf health and management.
The priority areas are:
Whatever the ultimate destination of the calf, correct colostrum management remains the most critical area of calf care and is the essential step in the animal acquiring the immunoglobulins they require.
For successful passive transfer of immunoglobulins, the calf must ingest sufficient good quality colostrum as soon as possible after birth. Failure of passive transfer (FPT) is defined as a serum IgG concentration below 10mg/mL and has been found to be associated with increased preweaning morbidity and mortality, increased duration of illness, reduced growth rates and poorer long-term performance (for example, reduced growth rates, reduced first lactation yield and increased culling rates).
Although the importance of passive transfer has been studied extensively, and despite repeated communications around the importance of colostrum from industry bodies, farms continue to struggle with FPT. Worldwide prevalence estimates range from 14.2% in Scottish dairy-bred calves (Haggarty, 2022) to as high as 41.9% in Australia (Abuelo et al, 2019).
The use of serum total protein monitoring offers a simple and cost-effective way of monitoring colostrum feeding practices on farm and can be a key component of calf health monitoring programmes. The system proposed by Lombard et al (2020) gives clear categorisation of passive immune transfer, with the aim of having 40% of animals tested being classified as having excellent passive transfer (serum total protein greater than or equal to 6.2g/dL) and 30% of animals being classified as having good passive transfer (serum total protein 5.8g/dL to 6.1g/dL). It must be noted that the cut-offs proposed by Lombard et al are based on calves fed natural colostrum, and work by Lopez et al (2021) has highlighted the potential for serum total proteins to be less well correlated with serum IgG and the tendency for calves fed colostrum replacer to have lower serum total proteins, even when they have adequate serum IgG. So, if implementing monitoring systems on farms where colostrum replacers are being used, it is important to potentially reduce the target thresholds.
While traditionally the focus has been on the initial colostrum feeding phase and the importance of having calves consume the requisite amount of colostrum within the first 12 hours to ensure sufficient immunoglobulin absorption, interest has been increasing in extended colostrum feeding.
Colostrum is a highly nutritious feed (rich in protein and fat) and evidence shows antibodies remaining in the gut lumen after colostrum feeding also provide local immunity against enteric infections. Other components in colostrum include insulin and insulin-like growth factor, which promote gut health and lactoferrin and lactoperoxidase, both of which have antipathogenic properties. Therefore, feeding of colostrum beyond the first feed can provide health benefits to the calf.
Extended colostrum feeding can take a number of forms. It can be achieved by feeding transition milk (the milk produced during the second to eighth milking) over an extended period, which more truly mimics what would happen in a naturally suckled calf. Alternatively, extended colostrum feeding can be achieved by the supplementation of milk replacer or whole milk with true colostrum, or a high-quality (minimum of 100g of IgG per dose) colostrum replacer for a minimum of four days and up to 14 days.
Several potential benefits to implementing an extended colostrum protocol exist. These include:
While the list of benefits to extended colostrum feeding is long, it is essential producers ensure colostrum is harvested, stored and fed in a clean manner. Denholm et al (2017) and Haggerty et al (2021) have highlighted the high levels of bacterial contamination of colostrum on farm and the risks this poses for disease. It is also important to consider how such feeding practices fit into control programmes for diseases such as Johne’s.
Young calves are extremely susceptible to disease as they are still developing immunocompetence and because of the numerous stressors that they face in their first few weeks of life. While ensuring they receive the necessary immunoglobulins from colostrum is essential it is also important that we take steps to minimise exposure to disease-causing organisms in the first place. Numerous studies have identified the wide variation in hygiene practices that currently exists on UK farms, and this represents an area where, as vets, we can deliver true value to our clients by providing advice and guidance on maintaining a high standard of hygiene in all areas of calf rearing.
Poor hygiene can result in bacterial contamination of colostrum and milk (or milk replacer), which can then result in failure of passive transfer as well as higher morbidity rates. Irregular or inadequate cleaning of feeding equipment is one of the most common problems in calf-rearing and implementing appropriate cleaning and management interventions are key tools for disease prevention. It is important to make the cleaning process easy. Poor setups or lack of the essential equipment are barriers frequently seen on farm and reported by farmers to adoption of good hygiene practices.
It is essential the team is provided with adequate supplies of water at the correct temperature, the correct chemicals and the means to measure them out to the right concentration, cleaning equipment, such as brushes, and a decent wash trough with good drainage. Having space to hang everything up to drain and dry, off the floor and away from potential sources of contamination, is also important post-cleaning. Vets can help the process by providing their clients with written protocols describing the cleaning process and regularly checking that it is being followed.
As we look to the future it is exciting to see more and more technology coming into calf space. Calf-monitoring systems are becoming increasingly commonplace, with eartags available that can gather information on calf activity, behaviour and also temperature.
Such systems will hopefully go some way to address some of the challenges around rapid and early disease detection. The true benefit from early disease detection is going to be realised if the farmers can take clear actions off the back of the health alerts, and so it is essential we engage with the use of the systems and work with our clients to implement robust treatment protocols for commonly identified disease conditions, such as scour and pneumonia.
While monitoring systems can help facilitate early detection of disease, it is important we also use the data provided by these systems and from other sources to identify key challenges on farm and then develop focused disease prevention strategies. Taking a holistic approach to disease management and ensuring we address all aspects of disease risk, including biosecurity, the environment, nutrition and the management of the calf, will enable us to provide long-term sustainable solutions for our clients.
The practice of immunising the pregnant cow with the intention of controlling neonatal morbidity and mortality is well-established, with a number of licensed vaccines available for the administration to pregnant animals for the control of Rotavirus, coronavirus and Escherichia coli. We have also seen the launch of a vaccine for Cryptosporidium parvum, which further extends the range of scour pathogens we can vaccinate for. All of these vaccines work by enhancing the antibody titres in colostrum, so it is essential clients understand the importance of colostrum feeding for these products to be effective.
Vaccination is also a key tool in the prevention of pneumonia, and we are in the privileged position of having a several different vaccines available to us. There is not a one-size-fits-all programme for pneumonia vaccination, and so it is essential we consider the individual challenges, risk factors and pathogen profiles on each farm when designing vaccine schedules.
Vaccines must be used as an intervention at the critical control point in bovine respiratory disease (BRD) pathogenesis, rather than being administered to high-risk, stressed calves under high infection pressure. Vaccinating the calves before the risk period should always be the aim, but with farmers indicating calves between 10 days and 6 weeks are the most commonly affected by BRD it can be a challenge to get vaccines in early enough. Products are available, though, that can be used from the day of birth.
The calf-rearing phase should remain a key area for vets to engage with their clients. Industry initiatives, new technologies and new biologicals all offer an opportunity for engagement with this critical period, which can lay the foundations for an animals’ life-time performance.
References
Abuelo A, Havrlant P, Wood N and Hernandez-Jover M (2019). An investigation of dairy calf management practices, colostrum quality, failure of transfer of passive immunity, and occurrence of enteropathogens among Australian dairy farms, J Dairy Sci 102(9) 8,352-8,366.
Boulton AC, Rushton J and Wathes DC (2015). A study of dairy heifer rearing practices from birth to weaning and their associated costs on UK dairy farms, Open J Anim Sci 05(02): 185-197.
Denholm KS, Hunnam JC, Cuttance EL and McDougall S (2017). Associations between management practices and colostrum quality on New Zealand dairy farms, NZ Vet J 65(5): 257-263.
Haggerty A, Mason C, Ellis K and Denholm K (2021). Risk factors for poor colostrum quality and failure of passive transfer in Scottish dairy calves, J Dairy Res 88(3): 337-342.
Haggerty A (2022). Failure of passive transfer and colostrum quality in Scottish dairy calves. MVM(R) thesis, University of Glasgow.
Lombard J, Urie N, Garry F, Godden S, Quigley J, Earleywine T, McGuirk S, Moore D, Branan M, Chamorro M, Smith G, Shivley C, Catherman D, Haines D, Heinrichs AJ, James R, Maas J and Sterner K (2020). Consensus recommendations on calf and herd-level passive immunity in dairy calves in the United States, J Dairy Sci 103(8): 7,611-7,624.
Lopez AJ, Steele MA, Nagorske M, Sargent R and Renaud DL (2021). Hot topic: accuracy of refractometry as an indirect method to measure failed transfer of passive immunity in dairy calves fed colostrum replacer and maternal colostrum, J Dairy Sci 104(2): 2,032-2,039.
