Maximizing calf survivability is crucial to economic success of beef producers. But having healthy calves starts many months
before calving season. Proper herd nutrition impacts calf survivability more than any other factor. Proper environment/facilities
also are important. If these two factors are under control, herd outbreaks of calf diseases will be minimized.
Calf losses are greatest in the first week of life, and most of these are a direct result of dystocia. Some causes of dystocia,
such as fetal malpositioning, are impossible to control. However, other causes of dystocia, such as poor nutrition due to
under or overfeeding and poor heifer and bull selection, can be minimized with proper management.
Underfeeding late-gestation cows can have a major impact on calf survivability for two reasons. First, stillbirths will increase,
probably due to failure of the cow to go into labor or prolonged labor. Second, birth weights of calves might decrease, as
will calf vigor. The producer might not notice this unless records are maintained of cow body-condition scores and calf birth
weights and survival. This slight decrease in calf birth weight and vigor increases failure of passive transfer, increases
cold stress and hypoglycemia, and decreases disease resistance, all of which decrease calf survivability.
Overfeeding, although less common, can be as damaging as underfeeding. Excess fat in the vaginal cavity can cause dystocia.
Overfeeding of heifers can increase fat in the udder, and impact milk production later. Nutrition also impacts vaccine response
due to its impact on the immune system—both humoral and cell-mediated immunity. Cows can respond to a vaccine only if they
have proper energy, protein and mineral levels in the diet. For example, if a cow isn't taking in enough protein to maintain
her body condition, she can't make antibodies. Therefore, vaccinating cows to protect calves through colostral transfer of
immunity will only work with proper cow nutrition.
Historically, focus has been placed on the influence of nutrition in the third trimester on calf health. A newer focus is
the influence of nutrition in early gestation and its impact on placental weight and subsequent fetal growth, neonatal weight
and conformation, and body fat makeup and metabolism. Subsequent growth later in life and long-term reproductive health of
calves could be impacted by nutrition in these early stages of gestation in their dams.
Failure of passive transfer
Many immune-system defense mechanisms are lacking or deficient in the neonatal calf. Therefore, intake of high-quality colostrum
to provide adequate passive transfer of immunity is one important factor in protecting calves from disease. Besides providing
circulating immunoglobulins, colostrum provides local immunity in the gut, WBC's that also contribute to local immunity and
stimulate cell-mediated immunity if fresh, and nutritional elements. Calves that receive colostrum might have higher growth
rates than calves that don't receive colostrum, even if those calves don't become ill. This increase in growth rate carries
over even into the feedlot.
Several factors can contribute to failure of passive transfer (FPT). Low immunoglobulin concentrations in colostrum of beef
cows usually are a result of poor nutrition, especially in heifers. Weak calves and poor udder conformation or a poor environment
can all interfere with the calf's ability to ingest colostrum. Even if calves ingest adequate amounts of good quality colostrum
at the appropriate time, sometimes they do not absorb enough of the immunoglobulins. Dystocia leading to hypoxia and acidosis
likely is the most common cause of poor absorption. Other causes that are implicated, but difficult to prove, are placental
insufficiency due to fetal oversize and/or poor nutrition in early gestation.
Prevention of FPT in an individual calf involves ensuring that 100 grams of immunoglobulins is ingested. Two liters of beef
or four liters of high-quality dairy colostrum is recommended. High-quality dairy colostrum is hard to find and should come
only from farms on a Johne's control program. The colostral supplements available at this time are very poor substitutes for
real colostrum, and do not warrant the purchase cost.
Prevention of FPT on a herd basis involves providing adequate nutrition, providing an environment that allows the calves to
stand and nurse without difficulty, minimizing dystocia and culling cows with poor udder and teat conformation.