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Level of milk replacer nutrition and immunity of baby calves

Mark Hill, Jim Quigley and Gale Bateman Published on 17 January 2014

There has been a lot written about how feeding more milk replacer will improve the immune system and health of baby calves. Several laboratories have compared feeding calves conventional milk replacers at approximately 1 pound of solids daily to higher levels of nutrition.

Higher levels of nutrition were frequently milk replacers that are approximately 28 percent protein fed at approximately 2 pounds of solids daily.

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When reviewing the literature of peer-reviewed research, it is hard to find research where the higher levels of nutrition improved the health and immune function of baby calves. In fact, there are six journal articles from various laboratories that have reported reduced immune function with high versus low levels of milk replacer.

These reports have included reduced leukocyte and T-cell function, reduced serum immunoglobulin A and G2 concentrations, which are all responses measured in the blood that show how different parts of the immune system may respond when calves were fed high compared to low levels of nutrition.

At least two trials have reported some immune function differences post-weaning. One reported increased mRNA levels of L-selectin in weaned calves from high versus low levels of pre-weaning nutrition.

Another reported that Jersey calves fed a high level of nutrition pre-weaning had better neutrophil function than Jersey calves fed a low pre-weaning level of nutrition during the post-weaning period, but there were no differences in Holsteins.

L-selectin and neutrophil function are measures from blood samples that give some indication how the immune system may be quickly responding to challenges. However, these research trials found no differences pre-weaning.

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Maintenance or below-maintenance level of nutrients
Some believe maintenance is a critical threshold for the immune system and its proper function. In a veterinary journal article from 1987, Canadian researchers fed calves either well above nutrients required for maintenance or at 50 percent of the nutrients required for maintenance.

They reported the calves fed below maintenance had lymphocytes less able to respond to an in vitro challenge with an antigen: concanavalin A. Simply stated, in this trial calves fed well below maintenance had an immediate immune response measured in a blood sample that was poor compared to calves fed above maintenance.

More recently, in a field trial in Minnesota, veterinary researchers fed calves pasteurized milk or a 20 percent protein, 20 percent fat milk replacer and similar amount of solids adjusted to feed more during cold temperatures.

Calves fed the milk replacer which was lower in protein and fat than the milk were consuming 20 to 30 percent less energy and protein than the milk. Calves fed milk replacer had greater rates of death loss and sickness than calves fed milk, and this was especially pronounced in cold temperatures.

While not completely described in the journal article, it has been speculated by some scientists that the calves were fed below their maintenance requirements during the cold months of this trial.

We must point out that fatty acid and amino acid, as well as other functional nutrients, were likely greater in the milk than the milk replacer fed in this trial. These nutrients have a research-proven function in health and immunity, so level of nutrients were confounded with type of nutrients fed.

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In another recent veterinary research trial, calves fed a high level of milk replacer grew better to an oral challenge of Cryptosporidium parvum than calves fed a low level. This was a summer trial, 21 days long, with calves housed on concrete floors covered in pine wood shavings.

Calves fed on the low level of milk replacer were fed 1.1 pounds of a 20 percent protein, 20 percent fat milk replacer per day (to provide 0.13 Mcal ME per kg BW0.75), whereas calves fed the high level were fed 1.9 to 2.4 pounds of a 28 percent protein, 20 percent fat milk replacer daily (to provide 0.23 to 0.30 Mcal ME per kg BW0.75 until days 1 to 7 and 8 to 21, respectively). No calf starter was fed to the calves.

Under these conditions, calves fed the low level lost 0.1 pounds of bodyweight per day, and calves fed high level gained 0.9 pound per day. Immune measurements were similar between groups.

Since the calves lost bodyweight in the 21-day trial, some scientists have suggested that they are below their maintenance requirement; however, this is uncertain. Additionally, growth – not health – was the large difference in level of milk replacer fed. Sickness appeared to be robbing nutrients for growth.

Calves under 2 or 3 weeks old have immature body systems for regulating body temperature, immunity and digestion. This is demonstrated by calf performance in the first seven days of a trial feeding three levels of milk replacer, shown in Figure 1 .

calf performance in the first seven days of a trial feeding three levels of milk replacer

Calves fed the control program (1 pound of a 20 percent protein, 20 percent fat milk replacer) on average gained bodyweight; yet about one-third of the individual calves lost weight. However, calves fed a moderate or aggressive program (1.5 pounds or more of a 26 percent protein, 17 percent fat milk replacer) had few calves losing weight during the first seven days.

A gallon of milk or milk replacer (or approximately 1 pound of solids) supports approximately 0.3 pounds of daily bodyweight gain in the young calf according to the nutrient requirements of dairy cattle.

This program of a gallon of milk or milk replacer, along with free-choice dry starter feed, can support approximately 1 pound of bodyweight gain over the first six weeks or so of a calf’s life pre-weaning. Yet, environmental stress or sickness can rob nutrients from growth.

At least five other trials have reported more respiratory or digestive sickness with high then low levels (approximately 1 pound of solids) of milk replacer in peer-reviewed journal articles. However, most controlled research in scientific journals report no differences in health of calves with different amounts of nutrients fed via the milk replacer.

Take-home summary
There is much press that one can feed more milk replacer and improve immunity of the calf. The data regarding whether the level of milk replacer is involved in immunity is not clear. In fact, some articles show that health and/or immunity is poor at 2-plus pounds of milk replacer solids compared to about 1 pound of milk replacer solids.

It would appear that a threshold related to level of milk replacer and immunity/health could be maintenance. If calves are fed below maintenance (a very low level of milk replacer), then immunity might be poor.

We want to use this information to feed calves better. Farmers do not intentionally feed calves below maintenance. Farmers care for their animals. Here are some items to consider in how we feed and care for calves.

Housing and management trumps nutrition
Keep drafts off of calves and yet maintain good ventilation. Insulate calves from the cold ground with abundant long-straw bedding. If at all possible, use long, dry straw instead of shavings.

A scientific trial reported that bedding calves with straw supported more bodyweight gain than bedding with dry wood shavings or even an additional half-pound of milk replacer solids fed per day.

Avoid 1 pound per day conventional programs if management is less than excellent
These programs of about 1 gallon of liquid daily may not cover the maintenance requirements of calves during their first few weeks of life when calves do not consume large amounts of starter. This is all dependent upon housing, environmental temperatures and management.

Yet for that baby calf’s immature metabolism, along with temperature and pathogen stresses, 1 pound of solids per day has limitations. If immunity is related to being fed below maintenance, again, 1 pound of solids from milk or milk replacer could be too little to feed.

Feeding functional nutrients can improve health and immunity
In several species, including calves, functional nutrients like specific fatty acids and colostrum are known to aid in immune function and health. These levels in the diet may relate back to meeting specific minimum levels of these functional nutrients in the diet. This is a topic for another article. PD

Jim Quigley is technical and research manager – calf and heifer with Provimi North America. Gale Bateman is a ruminant nutritionist with Akey.

References omitted due to space but are available upon request. Click here to email an editor.

Mark Hill


Mark Hill

Ruminant Nutrition and Research
Provimi North America

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