Newborn calves are born with virtually no immunity of their own.
The cow’s placenta does not allow antibodies to pass from the mother to the calf during pregnancy, which means the calf must receive its initial immunity from the antibody rich colostrum, or first milk of the cow.
This initial immunity is essential because it provides protective antibodies against many of the diseases that affect newborn calves, such as calf scours, navel abscesses, arthritis and pneumonia.
Even the vaccines we use to prevent scours in calves rely on this passive transfer of immunity in the colostrum.
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These vaccines are given to cows before calving to promote specific antibodies against bacteria and viruses that cause neonatal calf diarrhea. However, the calf must receive these antibodies through the cow’s colostrum to receive the benefit of this protection.
The calf is able to absorb these antibodies at significant levels only during the first 12 hours of life.
The gut’s closure to antibody absorption is a gradual process but begins to decline rapidly until complete closure occurs at about 24 hours of age.
After the gut closes, the antibodies can still have local effect within the gut, but they can no longer be absorbed into the blood stream.
Calves that do not receive adequate amounts of colostrum immediately after birth are at a much higher risk of becoming sick and are also more likely to die.
Many cases of diarrhea, navel ill, blood poisoning and pneumonia in calves are a result of failing to receive an adequate level of colostral immunity.
A recent study that Dr. Andy Acton conducted in Saskatchewan cow-calf herds found calves that did not receive optimal levels of colostral immunity were twice as likely to be treated and tended to weigh significantly less at weaning.
Ideally, a calf needs at least two litres of colostrum within the first six hours of life to provide optimal levels of immunity, but the required volume depends on the concentrations of antibodies in the first milk of the cow.
Dairy cows tend to produce a much greater volume of colostrum and their concentrations of antibodies may be diluted. Many dairy veterinarians routinely recommend that dairy calves be tubed with up to four litres of colostrum within the first six hours of life to optimize immunity.
In beef calves, we would hope that the calf gets up quickly after birth and begins to suckle within the first few hours.
Calves that have not nursed properly within the first two to three hours should be noted and observed more closely.
In colder weather, calves will become hypothermic and may be less vigorous and less likely to suckle immediately. These calves should be tube fed colostrum and placed in a warming box.
A calf can probably be given more time to suckle properly on a warm day, but it should be tube fed colostrum if it has not suckled by six to eight hours.
The calves that are at the highest risk of failing to receive adequate colostral immunity:
• had a difficult birth;
• were abandoned or mismothered;
• are hypothermic in cold weather.
Pendulous udders and large teats can also make suckling difficult for even vigorous newborn calves.
Colostrum can be collected by milking the cow or by using reconstituted freeze dried colostrum substitutes. Your veterinarian can recommend a good colostrum substitute because quality varies.
Take the opportunity to collect colostrum from cows that lose their calves or that have an abundance of colostrum and need to be milked.
The colostrum can be kept in the refrigerator for seven to 10 days to be used for other newborns. Extra colostrum can also be kept frozen for up to a year. Frozen colostrum should be gradually thawed in a warm water bath because high heat can destroy antibodies.
Acton’s study found that up to 25 percent of calves in well managed herds can have less than optimal levels of colostral immunity.
Preventing calving difficulties, chilled calves and mismothering are important components to ensure that calves are vigorous and more likely to suckle early and receive this essential protective immunity.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.
