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Introduction
The issue of how much colostrum to feed is extremely important – to the producer and to the newborn calf. The greatest risk occurs when the calf will receive too little colostrum, which puts the calf at great risk of disease and death. The traditional recommendation has been to feed 2 quarts of colostrum as soon as possible after birth and then again, 12 hours later. Is this recommendation still applicable today? Feeding too much colostrum is not usually considered a problem – unless it is fed at one time. So, how much is too much and how little is too little? Unfortunately, the answer is not as easy as it seems. The amount of colostrum to feed really depends on several factors – including the amount of antibody (or Ig) in the colostrum, the body weight of the calf, the age of the calf at first feeding, and several other factors.
To calculate he amount (or mass) of IgG that a calf needs, several assumptions may be made, based on existing research data (Figure 1). Our goal is for the calf to obtain a minimum of 10 grams of IgG per liter of serum. A calf’s plasma volume at 24 hours of age is approximately 9% of its body weight. To achieve 10 g/L, a newborn calf that weighs 40 kg (about 88 lbs.) must consume 36 grams of IgG from colostrum or a supplement by 24 hours of age. However, IgG is not absorbed with 100% efficiency. Research data suggest the efficiency is closer to 35% (the other 65-70% equilibrates with other body pools or is not absorbed at all). So, to achieve 10 g/L, the calf must consume 103 grams of IgG (36 grams / 35%) by 24 hours. If a margin of safety is included in the calculations (achieving a plasma IgG concentration of 15 grams of IgG per liter), the calf needs to consume 154 grams of IgG.
The efficiency of IgG absorption is an important component of the IgG intake equation. Efficiency is not a constant, but changes (declines) according to a number of factors – however, the most important is age at first feeding. Efficiency of IgG absorption is highest immediately after birth and declines to nearly zero by 24 hours of age. Thereafter, little of the IgG consumed is absorbed into the bloodstream. Because efficiency of absorption declines with age, it’s critically important for colostrum (or supplements) to be fed as soon as possible after birth. Research estimates of efficiency of absorption vary widely and range from as high as 65% to as low as 25%. Most estimates, however, fall in the range of 30 to 40%.
The amount of antibody (also called immunoglobulin, or Ig) in colostrum is the most important factor in deciding how much colostrum to feed. In reality, we’re trying to feed Ig, not colostrum per se. So as the Ig concentration in colostrum goes down, the more colostrum is needed. On the other hand, feeding enough high quality colostrum (lots of Ig) is still important – colostrum has lots of energy, protein, vitamins, and minerals that the calf needs to be healthy.
Generally, the amount of colostrum was assumed – usually we assumed that 2 quarts of colostrum in each of two feedings would do the trick. However, in many cases, this will not provide enough antibody to the calf. Using a colostrometer can provide you with an idea of whether the colostrum is of sufficient quality (see Calf Note “#22 – Using the colostrometer to measure colostrum quality)
So what are you to do? Many veterinarians recommend feeding 4 quarts of colostrum to Holstein calves in the first feeding – by esophageal feeder if necessary. By feeding a large amount in the first feeding, you can maximize absorption of antibody. Of course, Jersey calves and small Holsteins should be fed a smaller amount. Another approach is to look at the volume of colostrum produced. Washington state researchers reported that when a cow produces more than about 18 lbs. of colostrum, it may contain less Ig than necessary to provide adequate passive immunity for the calf. Recommendations published by The Bovine Alliance on Management and Nutrition are included on the following page.