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HEALTH AND SURVIVAL

Calf survival is crucial to the economic success of a beef operation. But the process of ensuring healthy calves doesn’t start at calving. It actually begins nine months earlier at conception, and the first factor that affects it is the dam’s nutrition. Once gestation is complete, the environment (facilities) as well as the management of the calf then play a sizable role. If you have these factors under control, you can minimize calf loss and lower subsequent disease in the calf crop.

Most calf losses occur in the first week of life, and the majority of these are directly attributable to dystocia. Though some causes of dystocia are impossible to control, such as malpositioning of the fetus, there are some that can be reduced.

For example, underfeeding cows has a profound negative impact on viability of calves. Poor nutrition means a weak cow and a prolonged labour, which boosts the stillbirth rate. In some cases, the cow may completely fail to go into labour.

If a live calf is born, poor nutrition during pregnancy decreases birth weight, and along with it, calf vigour. This effect is subtle and is only detected if records are maintained on cow condition as well as calf birth weights and survival statistics. However, there is a secondary effect — a weak calf has a greater chance of failing to get its needed colostrum. This lowers disease resistance through a lack of antibodies and also boosts cold stress and hypoglycemia due to insufficient caloric intake.

Overfeeding, though less common, is just as bad. By promoting fat deposition in the birth canal, it can cause dystocia. In growing heifers, excess fat replaces milk-producing tissue in the udder. Fat, mature cows fed low-protein yet high-carbohydrate diets have poorer responses to vaccines and this means fewer antibodies to pass on to calves in colostrum.

Producers have traditionally been told to focus on nutrition in the last trimester of gestation, after all, this is where the calf gains the majority of its weight. Newer research tells us that nutrition is just as important in early pregnancy. Optimal nutrition at this critical time can mean an increased weight of the placenta and a positive impact on subsequent fetal growth. This means that what the cow eats early in pregnancy can affect later growth and reproductive health of calves.

Maternal antibodies obtained through passive transfer are needed to protect the calf while its own immune system is developing and not yet able to respond to infections. These antibodies attack infections invading the body, but a significant number stay in the gut after the first 24 hours, providing local immunity and protecting the calf from scours. If passive transfer fails, calves do not grow as well and are at a greater risk of becoming ill.

Failure of passive transfer (this is measured as an insufficient amount of antibodies in the calf’s bloodstream) can occur if the colostrum itself lacks antibodies. This can be the result of poor nutrition, especially in heifers. As well, a calf may not be able to obtain colostrum if it is weak or there is poor udder conformation.

Calves may also be unable to absorb colostral antibodies properly. This can occur if a calf has had hypoxia (not enough oxygen) followed by acidosis during a dystocia, or if the calf takes its first meal of colostrum too late.

Each calf should ideally receive 100 grams of immunoglobulins (antibodies). This can be contained in two litres of beef colostrum or four litres of (high-quality) dairy colostrum. If milk is obtained from a dairy source, only milk from cows free of Johne’s disease should be used.

There are also alternative commercial colostral supplements. Christine Navarre, a veterinarian at the Louisiana State University Veterinary College, states that “colostral supplements available at this time are very poor substitutes for real colostrum, and do not warrant the purchase cost.” Your veterinarian can tell you if they are worthwhile in your operation.

There are many ways to prevent failure of passive transfer. It starts with supplying the best nutrition during pregnancy, minimizing dystocia so the calf has strength and can absorb antibodies, and make sure cows have good teat and udder conformation. Once the calf is born, you can help by making sure it can stand and nurse properly (it may need help or better footing).

On most farms, chances are, there is going to be a small number of calves that fail to get their needed immunity from colostrum. If the number stays small, disease outbreaks are controlled by the “herd immunity” — the disease fails to take hold. However, if the number of susceptible calves rises, there is a greater chance they will become ill from an infectious disease. This is because calves are effective amplifiers of disease and shed millions of organisms, contaminating the environment.

In some cases, vaccinating cows helps. However, to do this, the cause of the calf disease needs to be identified. This technique cannot be used as an emergency measure in the current year as the vaccines should be given a month before calving season starts. It is a tool to stop the same outbreak in the herd next year.

A contaminated environment is able to overwhelm the best-protected calves. It is simply a case of too many infectious organisms for the immune system to contend with. To prevent this, it helps to keep the cattle moving. Relocate feeders and hay racks to new places (away from waterers and shelters) so that the ground does not become saturated with organisms.

If disease does break out, it’s best to divide the herd. Sick animals and those that may be incubating the disease can be left where they are, but pregnant cows should be moved to a new, clean pasture. Segregating different-age calves so that younger ones are not housed with older ones helps reduce disease transmission.

Heifers deserve special attention. They should be bred to calve early in the calving season so they can be watched closely. As well, this gives them time to recover for breeding with the cow herd in the subsequent cycle. This also provides the opportunity for early weaning if they are nutritionally stressed and need a boost to prepare for the next season.

Selecting heifers and bulls that decrease dystocia and produce adequate milk also helps reduce calf loss. The same goes for embryo transfer. Embryo recipients should be proven cows that calve easily. They should also be free of diseases (such as BVD and Johne’s).

Lastly, feeding at night or late afternoon can boost the chance of daytime calvings. This means that more help will be available so that dystocia can be managed better and treated promptly.

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