Weak calf syndrome is not a specific disease. The word syndrome is a generic term to define a pattern of events due to known or unknown causes. When veterinarians use this word, it usually means the latter. Many possibilities could cause a “syndrome” and in the case of weak calf syndrome, research eventually pointed toward nutritional deficiencies (and sometimes diseases) as some of the possible causes.

“Weak calves” can be caused by different things, and sometimes multiple factors at the same time. These calves often die within a few days and are sometimes called dummy calves.            

Usually there is just an occasional “weak” calf born in a beef herd, but some years there might be loss of many calves.  Prevention can be difficult because the condition can be caused by different things, some of which may be too late to correct for that calving season.

Claire Windeyer, University of Calgary, says there are two main scenarios. One is the weak calf for which you know what happened to cause the problem. “Maybe it was born in a snowstorm, or had a hard birth, or some other obvious reason. The second scenario is a cluster of weak calves and it’s harder to know what happened,” she says.

Back in the 1960’s and 70’s some ranchers in the western U.S. were losing a lot of calves at birth or soon after to a mysterious ailment that came to be called weak calf syndrome. These newborn calves were typically normal-looking, with no noticeable problems, but were unable to get up. If they did manage to get up, they were too weak to seek the udder and usually fell down if they tried to walk around.

From a disease standpoint, BVD (bovine viral diarrhea) in the herd can sometimes cause weak calves, and from a nutritional standpoint, vitamin A deficiency, protein deficiency or selenium deficiency in the dam has been associated with weak newborn calves. Diagnostic tests, utilizing blood or tissue samples from the calf or the dam, can reveal BVD, or vitamin A and selenium deficiencies.

Protein deficiency

One of the major causes of weak calf syndrome, however, is protein deficiency in the dam. Some of the first studies to determine the cause were done by University of Idaho researchers from 1971 to 1985. Richard Bull, University of Idaho, was the lead nutritionist. The researchers and ranchers involved in this project learned how to prevent this condition even before they fully understood it.

On western ranches, most of the affected calves were from young cows (2 and 3 years old), due to deficiency of protein in the diets of these young cows. In 1971 and 1972 the research group collected thousands of blood and tissue samples from healthy calves and weak calves, and their dams. Analysis of these samples showed that the weak calves had a protein deficiency. These were mainly on ranches that used summer grazing allotments, calving in February, March and April—to have calves born and branded before range turnout.

In 1973 the researchers started a controlled study, selecting four ranches in Idaho that had a history of weak calf syndrome. The ranches varied in size from 150 cows to 1100 cows.  To make sure they were not dealing with mineral deficiencies, all the cows were fed the same customized mineral supplement developed by Dr. Bull. 

All the hay and winter feed sources on these ranches were tested, to determine protein levels. The researchers then manipulated diet protein levels for the young cows on two of the ranches by utilizing forage with adequate protein or by adding a protein supplement. Weak calf syndrome was eliminated on the two ranches where diet was manipulated, and incidence of weak calves remained the same on the other two ranches.  In 1974 they published a paper (Nutrition & Weak Calf Syndrome in Beef Cattle) and their recommendations were widely adopted over the next few years by ranchers who had experienced weak calf syndrome, virtually eliminating it.

Later, Bull demonstrated that calves born from protein-deprived dams were not physiologically normal; they were unable to efficiently absorb antibodies from colostrum.  Over a number of studies, he showed that the protein requirement of two-year old cows in the last 45 days gestation was about 1.81 pounds crude protein per day. As a result of his research, the National Research Council increased their recommendation for protein requirement of young cows.

Effects of protein deficiency in young cows are increased by cold stress. If cows calve in cold weather and calves are chilled at birth, their ability to absorb antibodies from colostrum are greatly reduced. If the immune system of the calf is already compromised due to protein deprivation in the dam, the likelihood that he will suffer from weak calf syndrome and die is high.

Call your veterinarian

Windeyer says that a calf that you know the cause (such as being chilled after a difficult birth), usually just needs basic care such as warming and drying, providing colostrum, helping it stand and nurse, etc. A herd problem can be harder to figure out or to know how to deal with those calves. “Producers should call their veterinarian and get diagnostic help.  All too often these cases are not fully investigated.”

Maybe the rancher lost five calves last week and this week has lost 10 calves and finally calls the vet, but calving season is almost over and there’s not much that can be done. “You no longer have the materials to submit to the lab, and it’s harder to figure it out,” she explains.

Ideally you should call your vet at the first loss, but most producers don’t—they just chalk up the odd loss here or there to bad luck. “Most producers don’t call the vet until they are already too far into it, but getting help earlier might give the veterinarian more chance to make a diagnosis and get some answers,” she says.

“There is a lot of information available about weak calf syndrome, but it is one thing to understand the factors that cause it, in general, and another to find out what’s causing it in your herd, to be able to prevent it in the future,” she says.

“Without looking into it you can’t make a good plan. Your vet can help.” 

There are many things that may be lurking under the surface that you can’t see.  Some calves may be born with an obvious abnormality, but if the calf looks normal it could be anything from a genetic problem to a toxic plant the cow ate, or nutritional deficiency.

“Nutrition can be a key factor, and may involve several deficiencies. If forage is low in protein it is probably also low in energy and vitamin A,” she pointed out.

[Heather Smith Thomas is a freelance writer based in Salmon, Idaho.]