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1206 PD: Building immunity in dairy calves

Sharon T. Franklin Published on 10 December 2006

The immune system that protects the body from infection is composed of two main branches, the innate branch and the adaptive branch. The innate branch provides the first line of defense against an attack by infectious agents and includes such components as skin, mucous membranes and neutrophils. The adaptive branch includes cells that can adapt and specifically target many different invaders.

In many respects, an attack against the body by disease-causing organisms can be compared to the attack of an army against a fort. The fort and its defenders can be compared to the body and the immune system. The walls of the fort are similar to the skin and mucous membranes of the body. They are physical barriers against an invasion by bacteria. The neutrophils are similar to scouting parties that are patrolling the perimeter and have orders to engage any enemy they find. They are effective killers and can send an alarm.

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The commanding officers of the fort are similar to the monocyte or macrophage cells of the adaptive branch of the immune system. These cells take in much information about the invaders and send signals to other parts of the adaptive branch of the immune system about the best way to fight. The lieutenants and sergeants of the defending forces are similar to the T-cells of the adaptive branch. These cells convey the messages of the commanding officers to the troops defending the walls, but they also have their own way of fighting as well.

The troops lining the walls can be compared to B-cells in the adaptive branch of the immune system. B-cells are responsible for producing antibodies (or immunoglobulins, Ig) to be used in the fight against invading organisms. The antibodies can be compared to the bullets fired by the defenders in an attempt to repulse the invading army.

If reinforcements had started for the fort at the first word of an impending attack, this would have been similar to the response of the immune system to a vaccination or previous exposure. With adequate reinforcements, the fort probably could hold against an invasion. Without reinforcements, the fort may be overwhelmed.

When disease-causing organisms overwhelm the defenses of the immune system, an animal becomes sick. Eventually, perhaps with the aid of artillery (antibiotics), reinforcements may arrive to retake the fort and the disease may be banished from the land.

Adding nutrition or nutraceuticals to the picture may make the components of the immune system stronger, faster and more prolific. Although these may not be the deciding factor in this scenario, it may bolster the strength of the fort and its defenders so they could hold the fort until the reinforcements and artillery arrive.

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In many cases with calves, nutrition or nutraceuticals may provide enough extra support to the immune system to allow the calf to hold on until reinforcements arrive. Calves are born with a naïve immune system that must be educated before it can mount an effective immune response on its own and generate its own reinforcements.

Whereas the innate branch of the immune system is functional, the adaptive branch must expand and learn the types of invaders present before it can mount an effective defense. In essence, the immune system of a newborn calf lacks bullets (Ig). Even the neutrophils need bullets to fight effectively. For approximately the first three weeks of its life, the calf relies primarily on the bullets (Ig) acquired from colostrum to protect it against invaders.

During the first three weeks of life, concentrations of Ig in the blood gradually decrease from the 24-hour value while there is an accompanying increase in number and percentages of B-cells. After three weeks of age, Ig concentrations gradually increase as the immune system of the calf begins to provide its own bullets.

The health, performance and survival of calves, especially during the first three weeks of life, rely on achieving high concentrations of Ig (antibodies) in the blood. Without question, the successful transfer of Ig from the cow (through colostrum) to the calf is an extremely important component for minimizing death losses of calves.

The method used to supply colostrum to a calf can have a major impact on absorption of Ig and the concentration of Ig achieved in the blood. The majority of studies indicate that calves allowed to nurse their dam for their first colostrum intake may not achieve adequate transfer of immunity. Logan et al. compared serum Ig concentrations of calves that suckled only with those of calves that were left with the dam but were fed approximately 1 liter of hand-milked colostrum by bottle for the first feeding.

Results indicated that only 23.2 percent of the calves allowed to suckle naturally acquired sufficient Ig whereas 42.3 percent of calves fed 1 liter of colostrum by hand and also were left with the dam to suckle acquired sufficient serum Ig concentrations.

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Nocek et al. reported that Holstein calves fed a total of 5.45 liters of colostrum in three feedings by bottle during the first 12 hours after birth had higher serum protein and serum IgG concentrations than calves that suckled.

Besser et al. reported that failure of passive transfer (serum protein less than 5 grams per deciliter or IgG less than 1,000 milligrams per deciliter) occurred in 61 percent of Holstein calves allowed to suckle at birth compared to 19 percent failure of passive transfer in calves fed a half gallon (1.9 liters) of colostrum by bottle. Further, only 11 percent of calves experienced failure of passive transfer when fed three-fourths of a gallon (2.84 liters) of colostrum at birth.

We conducted a study utilizing 31 Holsteins calves that were either removed at birth and hand-fed colostrum from the dam or remained with the dam and allowed to nurse. Hand-fed calves were fed 3 quarts of colostrum at birth and 2 quarts at 12 hours after birth. Serum protein concentrations at 24 hours after birth were greater in calves fed colostrum by hand even though calves allowed to nurse the dams were helped to nurse if they were observed to be having problems.

One of the calves that was supposed to receive its colostrum by nursing its dam died during the study. The calf experienced failure of passive transfer of immunity as indicated by serum protein concentrations that did not increase above levels observed at birth. One of the problems with allowing calves to nurse for their first meal of colostrum is that the quality of the colostrum is unknown. In one study, we administered oxytocin as soon after calving as possible and milked the cow with a portable milker in an attempt to collect all the colostrum produced by the cow. We found that of 50 cows collected for the study, four of the cows (8 percent) produced an inadequate volume of colostrum to feed their calf 2 quarts of colostrum for the first feeding. Some produced no colostrum at all.

We also found that a total of nine of the 46 remaining cows had very low colostrum quality as estimated by a colostrometer. Therefore, if the calves had been allowed to nurse their dam for their first feeding of colostrum, 26 percent would not have received either adequate volume or quality of colostrum.

We have found that colostrum quality declines during the summer at the University of Kentucky dairy farm. In the previous study, 10 of 11 cows with colostrometer values at less than 60 milligrams per milliliter calved between May 1 and July 31. We found that the winter colostrum quality averaged 105 milligrams per milliliter (37 samples) compared with summer quality at 62 milligrams per milliliter (26 samples).

We do not use colostrum with values of less than 60 milligrams per milliliter. Therefore, it is extremely important to handfeed calves colostrum that has been evaluated for quality.

The National Animal Health Monitoring System surveyed heifer calves on 1,811 farms in 28 states and found that 40 percent had less than optimal concentrations of IgG (less than 1000 milligrams per deciliter). In the United States, the most recent national data indicate that approximately 47 percent of calves are allowed to remain with the dam and nurse while 53 percent are removed prior to nursing.

While part of the calves that remain with the dam are hand-fed their first colostrum, 30 percent of all calves received their first colostrum by nursing the dam only. The most important method for enhancing immunity of calves, therefore, is to hand-feed adequate amounts (preferably at least 3 quarts at birth and 2 quarts at 12 hours) of high-quality colostrum (greater than 60 milligrams per milliliter) from healthy cows that have been vaccinated to provide antibodies against important pathogens of calves. A little extra time and trouble at the beginning of a calf’s life may either save a lot of time, trouble, and expense a little later in the calf’s life or save the calf’s life itself.

In addition to proper feeding of colostrum at birth, several nutrients may enhance immune function of calves. Some of these include the fat-soluble vitamins A, D and E, the water-soluble B vitamins and vitamin C and minerals such as selenium, zinc and copper.

We were interested in determining the effects of vitamin A on health and disease resistance. One thing we learned is that if a little is good, it is not always true that a lot will be better. We supplemented groups of 16 calves with either 0, 1,200 (the recommended level of vitamin A), 34,000 (approximately the amount found in many milk replacers) or 68,000 (an excessive amount) international units (IU) of vitamin A per day. We conducted liver biopsies to monitor vitamin A concentrations as an indication of vitamin A status.

We found that calves are born with practically no vitamin A stored in their liver, and apparently they like it that way. Even when we supplemented calves with 68,000 IU per day, liver stores of vitamin A did not increase to levels considered adequate until calves were approximately 6 weeks old. We also found we obtained better growth rates in the calves with the 1200 IU per day supplementation rate and that plasma levels of vitamin E were decreased in calves supplemented at the two highest rates of vitamin A.

A subsequent study investigated levels of supplementation between the 1,200 and 34,000 IU rates we used and showed that the most effective rate of supplementation was at 10,000 IU of vitamin A per day.

We have conducted several studies trying to determine how ambient temperature affects the immune system of calves and whether or not nutrition plays a role. Originally, we noticed that types of white blood cells present in the blood differed in winter versus summer calves. In fact, we noticed alterations in the white blood cell types when these was a wide fluctuation in ambient temperature over a short period of time.

We continued studies regarding effects of temperature on immune function. We monitored white blood cell types present in blood of heifers during ambient temperature fluctuations from hot to warm to cold, then back to warm. We found the same general alterations in white blood cell types occurred.

A subsequent study led us to believe that the alterations in white blood cell types were in response to a need for extra energy. If calves consumed adequate energy during cold weather, the alterations in white blood cell types did not occur.

Another study we conducted investigated the use of supplements as support for the immune system. Antibiotics have traditionally been supplemented to calves in milk replacer to support the immune system. Calves subjected to stressful situations and supplemented with antibiotics have had improved growth rates compared with calves not supplemented with antibiotics. Many consumers, however, are concerned that use of antibiotics in livestock may result in drug-resistant pathogens. Alternatives to antibiotics may provide equal performance.

We supplemented calves with nutraceuticals (a combination of fructooligosaccharides, allicin and gut-active microbes) and compared their performance with calves supplemented with antibiotics. Growth of calves supplemented with the combination of nutraceuticals was equivalent to growth of calves supplemented with antibiotics. Other studies have reported similar results for calves supplemented with fructooligosaccharides.

One of our recent studies evaluated the impact of supplementing cows with mannan oligosaccharide (MOS) during the close-up dry period on immunity of the cows and transfer of immunity to their calves. We used data from 39 cows to compare the effects of a control diet versus a diet supplemented with MOS on immune parameters of cows.

Data from their calves, including one set each of Holstein and Jersey twins, were analyzed for effects of the control diet versus the MOS diet on transfer of passive immunity to the calves. At four weeks prior to expected calving, blood samples were obtained from the cows and they were vaccinated against rotavirus. At three weeks before calving, cows were weighed, assigned to treatments and moved to the close-up dry cow lot where they were fed the control diet or the control diet plus MOS.

Cows were vaccinated a second time at two weeks before calving and blood samples were obtained through parturition. The cows were milked as soon after calving as possible. All cows received an intramuscular injection of oxytocin to facilitate complete removal of colostrum. The colostrum was weighed and the quality was estimated using a colostrometer. Colostrum samples were frozen for later analysis of Ig concentrations and rotavirus titers. Calves were separated from the cows prior to suckling.

Blood samples were obtained at birth and 24 hours after the first feeding. Maternal colostrum was fed at the rate of a half-gallon (1.9 liters) for Holstein calves and a third of a gallon (1.2 liters) for Jersey calves both at birth and 12 hours after the first feeding. Blood samples were analyzed for serum protein concentrations, serum Ig concentrations, rotavirus titers, packed cell volume, white blood cell counts and white blood cell types.

Feeding MOS during the close-up dry period resulted in significantly greater serum rotavirus titers in cows at calving, numerically greater titers in colostrum and a tendency for greater serum rotavirus titers and serum protein concentrations in their calves. Measures of nonspecific immunity, such as Ig concentrations and white blood cell counts, were not affected by feeding MOS.

The results of this study indicate it is possible to enhance the immune response of cows during the dry period by feeding a nutritional supplement. The ability of MOS supplementation to enhance the rotavirus neutralization titer in serum of cows immunized against rotavirus, together with the tendency for an enhancement of rotavirus titers in the serum of their calves, provides evidence that improved intestinal protection against rotavirus in calves may be achieved because of the potential for transfer of rotavirus antibodies from the bloodstream to the intestine.

Parreno et al. reported that elevated rotavirus titers in colostrum provided newborn calves with enhanced protection against rotavirus, resulting in fewer calves with symptoms and fewer days of diarrhea compared with calves fed colostrum from cows not immunized against rotavirus. The enhancement in the immune response of cows to rotavirus immunization is an indication that responses to other pathogens of economic importance may also be enhanced through supplementation of dry cows with MOS. Further studies are needed to investigate potential benefits of supplementation with nutrients during the dry period on health and disease resistance of the cows during the transition period and transfer of passive immunity to their calves.

We recently have investigated effects of crossbreeding on the immune system of dairy calves. All calves were fed pooled colostrums at 5 percent of bodyweight at birth and again 12 hours later. Blood samples were obtained at various times through six weeks of age and analyzed for white blood cell types, serum protein concentrations and Ig concentrations. Total Ig concentrations were greater for crossbred calves compared with the mean of the purebred calves indicating improved absorption of Ig from colostrums by crossbred calves.

Additionally, differences among treatments in types of white blood cells and the phagocytosis and killing ability of neutrophils were detected. It may be that one of the most effective ways for improving immunity of dairy calves will be through crossbreeding.

Finally, no supplementation can replace good management. Feeding colostrum is the most important management practice for development of immunity in dairy calves. Other management practices can help decrease stress on calves and result in improved performance. Some important management practices include maintaining a clean environment, providing clean water and starter at an early age and decreasing stress at weaning. PD

References omitted due to space but are available upon request.

—From 2006 Intermountain Nutrition Conference Proceedings

Sharon T. Franklin, Franklin Consulting, Lexington, Kentucky

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