Factors affecting IgG absorption in the baby calf aside from colostrum

Excellent colostrum management is key when it comes to providing the baby calf with its first source of immunity.

But what else can impact the immune status of baby calves?

A study conducted by Jones et al. (2004) found the apparent efficiency of IgG absorption ranged from less than 10% to greater than 25% in calves fed identical pooled colostrum at the same times after they were born.

What might be the cause of the differences in IgG uptake in these calves?

Various studies have reported some factors that may affect the ability of the calf to absorb adequate IgG, even when it receives what the rearer considers to be adequate colostrum.

We look at some of these factors:

Calves born from hypocalcemic cows

Recent findings from Sohrabi et al., (2024) have shown the proportion of calves with failure passive transfer (FPT) was extensively greater in calves born from persistently hypocalcaemic dams (P < 0.03) – these were cows that had low blood calcium levels four days post-birth; there was a strong tendency for FPT in calves from cows that did not show low blood calcium levels at birth but low four days post-calving (P < 0.10).

These calves also had higher faecal scores and were at greater risk of diarrhoea.

Interestingly, calcium status did not harm either the quality or quantity of colostrum produced by the cows but altered the ability of the newborn calf to absorb IgG.

Prevention is key when it comes to minimising the number of hypocalcaemic cows during the dry period.

Read our article on how reducing phosphorus in the transition cow positively effects calcium status.

Heat stress during the dry period

An interesting study looking at the effects on IgG absorption in calves (Dahl et al., 2016) if their dams were cooled with fans and misters. The calves were much more efficient at absorbing IgG from their colostrum compared to calves born from heat-stressed animals (Tao et al., 2012). Their serum IgG was greater in the first 28 days of life. These heifers also produced approximately 5kg more milk per day through 35 weeks of lactation, despite having similar body weight and condition scores at calving.

Keeping cows cool during extreme heat throughout the dry period will therefore reap benefits for the unborn calf’s health and future performance.

Dirty environment

It is a race against time to achieve IgG uptake before the intestine is exposed to bacteria. If this exposure happens before the calf consumes colostrum it will significantly reduce its ability to absorb adequate IgG to achieve passive transfer of immunity.

Good hygiene is therefore essential when it comes to the neonatal calf.

Dry cow diet

What a cow is fed during the dry period can have a big influence on her calf’s ability to absorb IgG.

An experiment in 1990 by Hough et al. saw Angus cows fed a restricted diet in which they received only 57% of their nutrient requirements for approximately three months before calving.

Although there was no significant difference in the colostrum quality between this group and cows fed a diet that provided all their nutrient requirements, the calves born to the restricted diet cows had significantly greater cortisol levels (33.8ng/ml compared to 26.1ng/ml for the control group).

At 24 hours, the calves from feed-restricted dams had a serum IgG level of 17.2g/litre compared to 22.2g/litre in the control calves.

High cortisol levels are a good indicator of stress and in this case, had harmed the ability of calves to efficiently absorb IgG.

Feeding higher energy diets to prepartum cows through fatty acid supplementation has also been found to have positive effects on IgG serum and enhanced apparent efficiency of absorption (AEA) (Garcia et al., 2014).

Avoiding any unnecessary stress and proper feed management during the dry period is highly recommended.

Calves born pre-term

Calves born before their due date may not efficiently absorb IgG as it is believed that the ability to absorb large molecules develops close to term.

An additional challenge resulting from a pre-term arrival is that colostrum formation takes place in the final weeks leading up to calving so colostrum quality and yield may also be impaired.

Difficult calving

Calf vitality can be impacted if its dam had a difficult calving as it will take longer for the newborn to achieve sternal recumbency and stand, both of which have a negative effect on the passive transfer of IgG.

This was confirmed in a study (Murray et al., 2015) which showed that calves that did not achieve sternal recumbency within 15 minutes of birth had reduced AEA compared tocalves that did. As all the calves in the study had received an identical quantity of colostral IgG at the same time after birth, reduced or delayed intake could be ruled out as the cause.

Pasteurisation of colostrum

Heat-treating colostrum can improve the efficiency of IgG absorption by 20%-35% (Johnson et al., 2007; Elizondo-Salazar and Heinrichs, 2009).

Calves fed colostrum heated to 60°C for 60 minutes had significantly greater serum IgG (18.0 g/litre) compared to calves fed fresh colostrum (15.4g/litre) according to Johnson et al., 2007. AEA was greater, at 35.6%, for the calves fed the pasteurised colostrum compared to the calves fed the raw colostrum, where the efficiency was only 26.1%. The study also highlighted that calves fed the fresh colostrum had an increased risk of scours – 20.7% – compared to calves fed the pasteurised colostrum, where the risk reduced to 16.5%.

Heat-treated colostrum should be fed immediately, or alternatively frozen, to prevent bacterial growth from occurring (Gelsinger et al., 2015).

Although there are benefits to feeding heat-treated colostrum, pasteurisation can have a detrimental effect on cytokine production which is involved in immune programming. It can also negatively affect lactoferrin concentrations and growth factors found within colostrum, which have an important role in intestinal epithelium development and in shaping the calf’s microbiome.

It is recommended that colostrum should always come from a low somatic cell count source.

Colostrum harvesting and feeding equipment must be kept as clean as possible to prevent bacteria from transferring to the newborn calf.