By now, most beef producers recognize the importance of colostrum in helping calves get off to a healthy start in life.  Since a mother cow’s antibodies don’t cross her placenta during gestation, the antibodies a calf gets through colostrum are all he will have to fight off infectious diseases during his first weeks of life.  Calves not getting enough colostrum are six times more likely to get sick during the first weeks of life compared to calves that got enough colostrum.

What are the factors that affect colostrum’s ability to help the calf?  One can break the list into factors that have to do with the cow, and factors that have to do with the calf. 

On the cow side, the quality and quantity of colostrum are affected by factors such as: cow body condition (cows with body condition scores of 5 or 6 produce better colostrum than poorer-condition cows); cow antibody level (which can be boosted by scours vaccination late in gestation); and the breed of cow (beef breeds generally have higher concentrations of antibodies compared to dairy breeds—some studies show as much as 2 or 3 times higher).   

But probably more importantly, there are many factors that affect a baby calf’s ability to drink colostrum and absorb the antibodies from it. 

  1. When the calf gets colostrum.  This might be the most important factor of all.  After 24 hours of life, a calf is essentially no longer able to get the benefit of the antibodies in colostrum.  But it’s also important to realize that a calf’s ability to absorb colostral antibodies starts to decline as soon as he is born.  What this means is that a calf will get a lot more antibodies from colostrum when it’s fed earlier than later.  I like to see calves get half of their required amount at 2-3 hours of age, then the rest 4-6 hours after that.  If you can’t get to the calf until he is 4 hours old or more, give him the whole amount at once. 
  2. How much colostrum the calf gets.  This is the subject of many “rules of thumb” among cattlemen, veterinarians, and extension people.  A common rule is that a calf should get a minimum of 100 grams of total antibody through colostrum.  But what does that mean?  It really depends on the concentration of antibodies in the colostrum, and we know that this can vary greatly between breeds and even between individual cows.  If one uses Holstein colostrum with 30 grams of antibody per liter, then a bit over 3 quarts will get the job done.  But beef cow colostrum might contain 100 grams in a liter, meaning 1 quart might do it.  But it might contain a lot less, too.  It’s hard to tell unless each dose of colostrum is analyzed. In spite of all these calculations, because of the limited window of absorption and the variability between cows in antibody levels, we really need to err on the side of caution when we administer calves colostrum.  Providing 4 quarts of colostrum during the first 8-10 hours of life is a common rule of thumb; if colostrum contains 25 grams of antibody per quart (probably attainable by most cows), this should generally result in adequate absorption of antibodies.  Feeding more than this to a viable calf will not hurt. 
  3. Temperature stress.  Many believe that chilled calves do not absorb antibodies from colostrum as readily as calves that are not chilled.  Likewise, heat stress causes calves to absorb antibodies less efficiently.  Common sense tells us that calves should be protected from temperature extremes, and colostral absorption is another reason to heed that common sense.  The nutrients in colostrum significantly improve a chilled calf’s ability to maintain normal body temperature, so it is not wise to delay administering colostrum too long in order to let a calf warm up to a more reasonable body temperature.  Cold stress does not affect the length of the “absorption window” significantly one way or the other. 
  4. Other factors.  Stress from a difficult calving or lack of mothering from the cow have both been shown to decrease the efficiency of colostrum absorption in calves.  

In the next iGrow article, we’ll look at when and how cattle producers should take it upon themselves to administer colostrum to newborn calves.

Source: Russell Daly