In the first part of our two-part interview, LifeStart sat down with Sarah Bolt, Knowledge Exchange Manager for AHDB (British Agriculture and Horticulture Development Board) Dairy, to discuss the health benefits of colostrum for neonatal calves as well as recommended parameters for quality and quantity.
LifeStart: Why is colostrum so important to the health of neonatal calves?
Sarah Bolt: Heifers are the future of our dairy herds and getting management correct from the start means that we stand a fighting chance to have a successful herd in the future. As such, they are an important investment. With good management practices, the mortality and morbidity rates of dairy heifer calves can be dramatically reduced. Colostrum is one factor, of many, that plays a significant role in the health and vitality of the neonatal calf. It is probably the single most important factor for new-born calf management, and certainly one that can be easily influenced on farm.
Calves are born agammaglobulinemic, therefore at birth the immune system is naïve to pathogens present in the calves' environment. Immunoglobulins must be obtained from colostrum whilst the gut wall is open to macromolecular transport. Passive immunity acquired during this time will protect the calf from these pathogens during their first few days of life. Failure of passive transfer (FPT) is experienced if inadequate IgG (serum IgG <10g/L) is transferred to the calf via the colostrum. Calves with FPT are more susceptible to infection (calves receiving <12g/L IgG are at a 2.3 greater risk of pneumonia (Virtala et al., 1999)), and have higher mortality rates. Indeed, a study by Godden (2008) showed that calves with a serum IgG <10 g/L had a survival rate of 94% whilst those with a serum IgG >10 g/L had a 2% higher survival rate at 96%. Additionally, FPT reduces long-term performance: delayed time to first calving, lower feed efficiency including decreased DLWG (Robinson et al., 1988), and decreased milk and fat production during first lactation (DeNise et al., 1989).
LifeStart: Do you think that the value of colostrum is in the IgG transfer only? Or, do you feel that other positive properties of colostrum can be beneficial to neonates?
Sarah Bolt: Whilst the transfer of IgG is vitally important, colostrum will also contain IgA and IgM in much lower concentrations. IgM acts much like IgG, although unlike IgG it stays in the bloodstream rather than entering other parts of the body. IgA will function on the surfaces of the intestine and other organs to prevent pathogens from attaching to the surfaces. As such, even after the gut has closed to the absorption of antibodies, the IgA in colostrum will remain active and provide localised protection against pathogens such as E. coli. For this reason, there is a benefit to the feeding of colostrum days into a calves' life.
With milk solids over 20%, colostrum is also rich in essential nutrients which the calf needs in its first few hours of life, for both maintenance and growth. Insufficient colostrum may lead to hypothermia as a neo-natal calf has very little body fat, leaving the calf helpless to keep itself warm, without an energy supply of fats and lactose from colostrum. According to David and Drackley (1998) a calves' store of body fat would be depleted after 18 hours if no additional energy was provided. Vitamins and minerals are also found at higher levels in colostrum. It is thought that these help with adsorption and digestion in the calf.
A relatively new definition related to epigenetics in new-borns is the concept of the lactocrine hypothesis. This is the effect of factors/mammary secretions (found in colostrum and milk) that have an impact on young mammals. The implication from data from other species suggests the possibility that the neonate can be programmed post-natally to modify developmental functions. Further work is needed to understand what role colostrum plays in this. Factors thought to be important in these processes include: glucose, insulin, IGF-1 and relaxin, amongst others.
LifeStart: What would you consider to be high quality colostrum? A particular level of IgG? Or is there some other parameter you would use?
Sarah Bolt: Good quality colostrum is high in antibodies as well as being a source of energy. Colostrum should be collected as soon after calving as possible, as the concentration of IgG decreases rapidly as the transition from colostrum to whole milk happens in the udder of the cow. There are many factors that can affect the quality of colostrum including: immune status of the dam (natural exposure/ vaccines), age of the cow (>3rd calvers are usually better quality), length of the dry period (poor quality colostrum is likely after a short dry period <30 days) and dry cow nutrition.
To ensure that the calf gets sufficient passive transfer, Chigerwe et al. (2008) found that a minimum 153g of IgG was required when fed at 2 hours after birth. With an abomasum volume of around 3 litres, it can be calculated that the colostrum has to be of at least 50g/L IgG, if 3 litres are to be fed. This figure of 50g/L IgG is a well-documented industry standard for good quality colostrum.
LifeStart: How much quality colostrum (and how soon after birth) do you recommend farmers get into their new-born calves?
Sarah Bolt: The quality of the colostrum and the time since birth will determine the volume required. The ability of a calf to absorb immunoglobulins is less than 50% at birth. This ability declines rapidly and by 24 hours of age, it is nearly non-existent. Hence, the calf should ideally receive colostrum within 2 hours of birth. All colostrum should be tested before feeding. The easiest way to do this is using a Brix refractometer (0-32%). A brix is not only cheaper than a colostrometer, but it is considerably more robust (I am yet to break one, but have a trail of broken colostrometers to my name!). Additionally, smaller volumes of colostrum are required for testing and it can be done without waiting for the colostrum to reach room temperature, as you should with the colostrometer. Using a Brix (0-32%) 22% TS = 50g/L IgG.
It is my view that we should not be talking about litres of colostrum as a target to be fed but looking to achieve a minimum intake of 153g of IgG (as previously discussed to achieve adequate passive transfer). Thus, if only poorer quality colostrum is available (less than 50g/L IgG), arrangements can then be made to feed more colostrum in an additional feed. Ideally, colostrum should be fed via a nipple. Not only do calves have an innate response to suck, the position of the neck and the sucking action enables the oesophageal groove to take the colostrum to the abomasum and avoid leakage into the rumen. Godden et al. (2009) compared feeding methods of colostrum and the apparent efficiency of absorption of IgG was higher when bottle fed over tube feeding.
As it important to get the colostrum into the calf as soon as possible, if the calf does not suck, tube feeding is advised. However, going back to the average abomasum size, I would not recommend this feed to be more than 3 litres. If more colostrum is required to reach the >153g of IgG, an additional feed should be fed within 6 hours, preferably by nipple.