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3 critical periods in a calf’s life: The first and second

A. F. Kertz for Progressive Dairy Published on 13 January 2020
dairy calves

The three critical periods in a calf’s life are as follows: the calf’s birth (the cow’s condition, degree of calving difficulty, cleanliness of the cow and colostrum management), the first two weeks of life (when most deaths occur) and the two weeks before and after weaning.This article will address the first two critical periods, and the third critical period will be addressed in a future article.

The first critical period 

Since there is no antibody transfer from the mother to the calf during pregnancy in ruminants, newborn dairy calves are dependent on colostrum for their antibody protection. The degree of protection calves get depends on the amount of antibodies actually absorbed. This in turn is dependent on several key factors: how soon after birth calves are administered colostrum, the antibody content of the colostrum and the quantity of colostrum administered. This has been simplified to: quickly, quality and quantity.



Another major factor in determining how calves respond to colostrum is the pathogen load in their environment at birth and how clean the colostrum is. In a sense, there is an equation of pathogen load plus colostrum equals the degree of protection for the calf. The strength or weakness of both these factors determines how much protection the calf is provided. This degree of protection must last until about 3 weeks of age when the calf begins to produce its own antibodies (Figure 1).

011020 kertz fig1

Immunity absorption

A study conducted with calves at a large dairy and found that doubling the amount of colostrum fed from .5 to l quarts and then from 1 to 2 quarts per feeding doubled the subsequent blood plasma levels of IgG (Figure 2). When colostrum was administered at birth, blood plasma IgG levels were about 25% greater compared to when initial feeding of colostrum was delayed until four hours after birth, doubled when first feeding was delayed until eight hours after birth, and virtually not effective when delayed until 24 hours after birth. Other factors which reduce antibody absorption are stresses due to heat, cold and especially difficulty with birth. And fat cows have more difficult calvings.

011020 kertz fig2

Colostrum management practices

Recent studies indicate that colostrum is not being harvested, fed or stored properly. As many as 30% to 90% of on-farm samples in different field studies in the U.S. and Canada have exceeded upper limits for bacteria of 100,000 colony-forming units per milliliter (cfu/ml) total plate counts (TPC) and 10,000 cfu/ml total coliform counts (TCC). Harvesting of colostrum is the first route of bacterial exposure to calves.


There are three primary sources of bacteria in colostrum: those shed directly from the udder, from contaminated equipment such as buckets and bottles used for feeding and bacterial proliferation in improperly stored colostrum. Thus, for optimal colostrum feeding, it is necessary to (1) prepare and clean the udder properly, (2) sanitize collection, storage, feeding, etc. equipment, (3) not pool sources for disease control such as Johne’s disease (Mycobacterium avium subspecies paratuberculosis) and (4) refrigerate by two hours (and use within three days) or freeze.

These field problems are most often due to using dirty colostrum or keeping colostrum warm too long before feeding. Thus, calves are inadvertently inoculated with bacteria (“bacterial soup”) when the colostrum has been kept warm too long (more than 20-30 minutes) before it is fed, especially in the summertime. Greater bacterial counts also reduce IgG absorption, and contribute to a false sense of security when other good practices of feeding colostrum are being followed.

Colostrum should generally not be pooled unless it has been or will be pasteurized or heated before feeding. When heat treating colostrum, use a well-insulated, well-stirred batch pasteurizer which can maintain 140°F for one hour before cooling down and feeding or storing. This operation must be closely monitored, controlled and periodically checked for efficacy by sampling and culturing both before and after processing. Minnesota workers found that the first control point in feeding clean colostrum is to prevent contamination during the harvest, storage and feeding processes. And that prompt refrigeration or freezing along with a preservative agent, such as potassium sorbate, are management strategies to limit or prevent bacterial proliferation. As herds got larger, they were often faced with separate crews for calving and receiving calves for rearing and different shifts around the clock. Thus, there can be problems with shifts operating inconsistently, as well as with crews with differing responsibilities pointing fingers at each other as the source when problems occur.

Consequently, some dairies have determined a major part of the solution to these issues is to pasteurize colostrum, which will take care of Johne’s disease, allow colostrum to be pooled and fed to any or all calves, and reduce the bacterial load in colostrum fed.

Long-term colostrum benefits

In a study conducted at a Wisconsin Brown Swiss, calves were fed either 2 quarts or 4 quarts of colostrum at the very first feeding. This was followed by feeding of transition milk for the next two days. Calves were then fed and managed the same for their growing period until completing one or two lactations. Calves fed only 2 quarts colostrum had twice the veterinary costs, gained 0.5 pounds less daily by breeding time, had 11% less milk production in the first lactation and had 17% less milk production in the second lactation than those calves that had been fed 4 quarts colostrum. Why this difference? Colostrum has been found to have over 200 bioactive compounds which affect growth, nutrient absorption, and bacterial exclusion. These are major benefits simply from feeding more colostrum at the very first feeding as a calf.

The second critical period

Quite simply, it is primarily related to the first critical period. About 60% of calf deaths prior to weaning are related to diarrhea. And that diarrhea is primarily related to cleanliness at calving when pathogens inoculate the calf and grow to surface as causes of diarrhea and death within the first two weeks of life.


Colostrum is essential to provide antibody protection to newborn calves, which is dependent on how quickly after birth it is fed, how much is fed, the antibody concentration in the colostrum best measured by a refractometer and how clean the colostrum and cow are. Failure to adequately manage this first critical period results in calves getting diarrhea in their first two weeks of life, which is the leading cause of death in calves before weaning. Properly pasteurizing, storing and feeding colostrum can be an effective method to minimize pathogen-contaminated colostrum.  end mark

PHOTO: Colostrum is essential to provide antibody protection to newborn calves, which is dependent on how quickly after birth it is fed, how much is fed, the antibody concentration in the colostrum best measured by a refractometer and how clean the colostrum and cow are. Photo by Mike Dixon.

This article is part one in a two-part series on the three critical periods in a calf's life. Watch for part two in a future edition of the Progressive Dairy Extra. References omitted but available upon request. Click here to email an editor.

A.F. Kertz is the founder and principal of Andhil LLC and the author of the book Dairy Calf and Heifer Feeding and Management: Some Key Concepts and Practices. Email A.F. Kertz.