As the weather begins to warm up, many beef herds in Western Canada are in the midst of calving season.
Producing and weaning live calves is an obviously critical component of cow-calf profitability and problems that occur at this time can have significant consequences.
The birthing period and the subsequent first few days of life have been shown to be the most hazardous time of a calf’s life.
Calving difficulty or dystocia has been shown by a number of studies to be a major cause of calf losses in the North American beef industry.
In one extensive study, which involved following more than 13,000 calvings, 69 percent of pre-weaning mortality occurred within the first 96 hours of birth. Almost two-thirds of these losses were directly attributable to dystocia or calving difficulty. Occasionally, calving difficulties result in a dead calf, but more commonly the result is a weak calf that is slow to get up and start suckling.
Calves that survive dystocia have been demonstrated to be 2.4 times more likely to become sick during the first 45 days of life.
Other researchers have shown that calves that experience dystocia are 13 times more likely to die within 12 hours of birth.
The importance of early intake of colostrum is well understood by most experienced ranchers. Calves are born with a functional immune system but rely on colostrum from the dam to provide them with antibodies for their protection from infectious disease early in life.
The calf is only able to absorb these antibodies (also known as immunoglobulins) at a significant level during the first 12 hours of life. The calf’s gut allows passage of these antibodies into the bloodstream immediately after birth.
However, by six hours after birth, the gut begins to lose the ability to absorb these antibodies. The gut closure to antibody absorption is a gradual process, but it begins to decline rapidly until complete closure occurs at about 24 hours of age.
After the gut closes, the antibodies can still have some local effect within the gut but they can no longer be absorbed into the bloodstream.
This transfer of immunity from the dam to the calf is termed the “passive transfer of immunity” and consuming colostrum within that four-to-six-hour window after birth is key to ensuring this happens.
I assume that the “passive” part of this immunity just means the calf’s immune system didn’t have to create the antibodies, but ensuring this occurs is not necessarily a passive event.
It has been declared in many studies that this passive immunity is the single most important factor affecting the pre-weaning health and survival of beef calves.
Calves that experience a failure of passive transfer of immunity usually caused by not sucking within those crucial first four to six hours of life have been shown to be 3.2 times more likely to get sick and 5.4 times more likely to die.
Even calves that receive less than adequate amounts of passive transfer (not complete failure) have been shown to be 1.5 times more likely to be treated and 1.6 times more likely to die.
A study in Saskatchewan herds by Dr. Andy Acton demonstrated that these calves with less than optimal passive transfer also weighed significantly less at weaning.
In a 2009 study by Dr. Cheryl Waldner and Dr. Leigh Rosengren, they evaluated calves in 203 western Canadian cow-calf herds and demonstrated that almost one-third of calves had less than optimal levels of passive transfer, putting them at greater risk of infectious disease and death.
It is almost impossible for us to determine how much colostrum a calf has consumed when it suckles, but we can closely watch calves at birth to determine if they have suckled or not.
Ideally, we would like every calf to jump up and suckle on its own, but we need to be prepared to intervene and supplement colostrum in calves that aren’t going to do that.
We can supplement colostrum by milking the dam and tube feeding or bottle feeding the calf, using banked colostrum from other cows on the same farm or by using one of the higher quality colostrum supplements that are available. The question is, how do we know which calves need help?
One method is to pay special attention and provide supplementation to calves that are in a high risk category of failure of passive transfer. This would include calves from any cows or heifers that need to be assisted at birth, calves from cows that have poor udder conformation, and calves from cows that are not displaying good mothering behaviour.
If the weather is cold, you might need to be prepared to supplement that calf by feeding colostrum even sooner.
One of the best tools that a producer can use is a simple technique to assess the vigour of the calf shortly after birth. There are some calves that will be obviously vigorous as they will get themselves into sternal recumbency, struggle to stand and suck within a few minutes after birth.
However, if there is any doubt as to a calf’s vigour, Dr. Elizabeth Homerosky, now a consulting veterinarian at Veterinary Agri Health Services in Airdrie, Alta., along with colleagues at the University of Calgary, published research to show how a simple technique can be used to assess a calf’s vigour.
Homerosky evaluated assessing the suckle reflex of calves at 10 minutes after birth by rubbing two fingers along the length of the calf’s tongue and the roof of the mouth. Make sure you have washed your hands well or wear latex gloves so that you don’t transmit bacteria into the calf’s mouth.
A calf with good jaw tone, good rhythm and a quick strong latch has a strong suckle reflex. A calf with poor jaw tone and a poor suckling rhythm has a weak suckling reflex.
In Homerosky’s study, calves with a weak suckle reflex were greater than 40 times more likely to fail to suckle the dam by four hours after birth and were 6.4 times less likely to have optimal passive transfer of immunity.
This simple test in combination with supplementing high-risk calves that experience dystocia or mismothering can help a rancher make a quick decision about colostral supplementation.
Good vigour is essential for those calves to ensure that they stand and consume colostrum within the first four to six hours of life.
John Campbell is a professor in the department of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.