Calves born with a condition commonly known as weak calf syndrome often die within minutes after birth, while others live for a few days. They are generally depressed and often unable to stand, walk or nurse without assistance. Caring for these calves takes a lot of time and work, yet the effort is seldom successful.
Recent studies by Dr. Cheryl Waldner of the Western College of Veterinary Medicine at the University of Saskatchewan have found that more than a third of all calves that are born alive then die before turnout to summer pasture are lost within the first three days of life. Calves that require assistance at birth are more than twice as likely to die as calves that do not.
An autopsy rarely gives obvious clues as to why very young calves have died, however, detailed tissue examinations often show damage to muscles including the tongue, diaphragm, heart and thyroid gland. Dr. Waldner was the lead researcher on a project funded by Alberta Beef Producers looking at some of the factors that play a role in weak calf syndrome and early calf mortality.
The objectives were three-fold: To describe lesions of skeletal muscles (tongue, diaphragm and leg muscle), heart and thyroid gland in calves that die soon after birth. To describe the micronutrient profile — particularly selenium and vitamin E— from the the livers of these calves.
To determine whether calf serum thyroid hormone, muscle enzyme creatine kinase, vitamin E, selenium and, or trace minerals are related to difficult or prolonged calvings by comparing blood samples from calves that underwent difficult births to those from calves that were born easily.
One part of the project involved collecting data from beef herds near Caroline, Alta. Detailed management records were kept and the dead calves were classified into four groups: abortions (born at least a month premature), still births (full-term calf that died within an hour of birth), neonatal mortality (lived for at least one, but less than 72 hours), and older calf mortality (died after three days of age).
The data from the Caroline herds were compared to those from the Western Interprovincial Scientific Studies Association (WISSA) study carried out by Dr. Waldner in 205 herds with 33,000 cows across B. C., Alberta, and Saskatchewan.
Nearly 92 per cent of the females exposed for breeding in the Caroline herds calved and 87 per cent of the calves survived to weaning. Of the 13 per cent of calves that died prior to weaning, 11 per cent were abortions, 33 per cent were stillborn, and 56 per cent died between birth and weaning.
In the WISSA study, 1.6 per cent of cows aborted, 2.6 per cent of calves were
stillborn, and 4.0 per cent died between birth and summer pasture turnout.
In the Caroline and WISSA groups, thyroid lesions were observed in 25 and 29 per cent of neonatal calf deaths respectively. Skeletal muscle lesions were found in 21 per cent of neonatal mortalities in the Caroline herds to 46 per cent of the neonatal mortalities in the WISSA herds.
Variations in feed due to drought may have contributed to vitamin and trace mineral deficiencies and led to higher levels of these problems in calves in the WISSA study.
Muscle lesions and deficiencies in vitamin E and, or selenium have also been linked to white muscle disease in calves. However, the lesions seen in white muscle disease differ slightly from the muscle lesions seen in this study. Typical white muscle disease often affects calves that are older than those examined in this study.
About 33 per cent of the calves from both studies that died within three days of birth had low levels of selenium. More than 80 per cent had low levels of vitamin E, and up to 95 per cent of the dead calves were defi-cient in vitamin A.
Compared to calves with normal thyroids, calves from the WISSA study that died with underdeveloped thyroids were more likely to have low liver selenium concentrations. Herds from the WISSA study where the cows had low serum selenium concentrations at pregnancy testing were more likely to have calves that died with muscle lesions.
Blood samples revealed that micro-nutrient deficiencies were common in the live calves as well: 20 per cent were deficient in selenium and more than 50 per cent had concentrations of vitamin E, vitamin A and copper that were below the reference level.
T3 and T4 thyroid hormones play an important role in regulating metabolic rate and have wide-ranging effects throughout the body.
High creatine kinase enzyme activity in muscle tissue is an indicator of muscle damage and breakdown.
Calves that required assistance at birth had lower T3 concentrations and were more likely to have muscle damage indicated by high creatine kinase levels than calves that were born easily.
Calves with higher serum creatine kinase activity also had lower serum vitamin E concentrations. However, it was unclear as to whether the muscle damage suggested by the high serum creatine kinase activity was caused by the low vitamin E.
Similarly, it wasn’t possible in this preliminary study to determine whether the low thyroid hormone concentration caused the associated calving difficulty or whether calving difficulty caused the low thyroid hormone levels — or whether a third factor was causing both.
What it means
This study showed that thyroid and muscle lesions are a common finding in early calf losses and suggests that trace mineral and vitamin nutrition during gestation may play an important role in the frequency and severity of these problems. Dr. Waldner adds that thyroid lesions are still under study as researchers have not yet been able to fully determine what they mean to calf health and production.
Identifying the potential risk factors that contribute to weak calf syndrome may help to determine ways to avoid the condition or better treat affected calves and may help to increase the percentage of calves that reach weaning age.
To improve calving ease and early calf survival, she suggests:
1. Paying attention to genetics. The bull has a major influence on calf birth weight and calving ease.
2. Following your veterinarian’s advice regarding selection, storage, use and timing of vaccines.
3. Working with a qualified nutritionist to ensure adequate feed quality and quantity and an appropriate vitamin-trace mineral supplementation program for bred females. Excessive amounts of trace minerals can be as dangerous as deficiencies.
4. Managing your feeding program to attain optimum cow body condition score at calving. Body condition is one of the most important factors affecting herd health and productivity.
5. Providing adequate shelter, bedding and space during calving. Segregating cow-calf pairs from the cows yet to calve as calving season progresses helps to minimize the risk of newborn calves being exposed to early calfhood diseases, such as scours.