Michelle Arnold, DVM, Ruminant Extension Veterinarian, University of Kentucky Veterinary Diagnostic Laboratory

“Weak Calf Syndrome” is a term applied to any calf born alive but is slow to stand and may or may not attempt to nurse. Calves born to dams that experience weight loss during the final 50-60 days of gestation are at high risk of being weak. An energy deficient diet fed to late gestation cows leads to prolonged labor, dystocia (difficult birth), poor quality and quantity of colostrum and decreased milk production. Many of the newborn calves presented to the UKVDL in recent weeks for necropsy have had no milk within the digestive tract. With excellent management, some weak calves will survive but most will die shortly after birth. If they survive, many experience sickness, decreased growth rates and lower weaning weights. The following is a summary of known factors involved in weak calf syndrome and how to best address them.

1. Inadequate Pre-Partum Nutrition: As mentioned previously, nutrition in the last 50-60 days of gestation is key to preparing a calf for life outside the cow. Approximately 80% of fetal growth occurs during this time so the dam must have adequate nutrition to support this growth. Additional nutrients are required to develop the brown fat in the fetus that will supply energy for the newborn calf to survive until adequate colostrum and milk are ingested. The two most important cow requirements are protein and energy. Research has shown that calves born to cows on a protein restricted diet have less vigor, less ability to warm themselves, and it takes a much longer time for them to stand after birth. Energy restricted cows (cows losing weight during late gestation or are thin) have calves with lower fat stores and longer intervals from birth to standing.

There is a much higher incidence of weak calves born to heifers and very old cows. First calf heifers are still growing themselves while pregnant so it is easy for them to become deficient in protein and energy. Older cows may have difficulty keeping weight on due to bad teeth, lameness or chronic disease issues. Often, heifers, thin cows and older cows simply cannot compete for hay and feed and should be fed separately to allow them access to the feed they need.

2. Micromineral or Trace Mineral Deficiencies: Deficiencies in blood selenium levels of cows (occasionally cobalt and iodine) have been associated with weak calves. A severe selenium deficiency will cause “white muscle disease” in which calves are born with a weak heart and/or weak muscles and die soon after birth. Keep a good trace mineral mix in front of the cows at all times or have it mixed in the feed if offering supplemental feed so calves are born with sufficient amounts.
3. Dystocia (Difficult Birth): A calf involved in a difficult birth will have decreased vigor and take longer to stand and nurse. Low levels of oxygen in the blood of the calf (“hypoxia”) may also impair the function of the central nervous system (brain and spinal cord) as well. Signs of dystocia in a newborn calf include a swollen head or tongue, bruising, fractures, excessive fluid in the trachea or lungs, and brown or yellow staining of the hair coat from the meconium. Additionally, a calf may have broken ribs that affect its ability to breathe.

If a calf does not stand and nurse within one hour of birth, the calf must be fed colostrum either milked from the dam or use a commercial colostrum replacement. Colostrum should be given as soon after birth as possible, preferably within 1-2 hours and no later than 6 hours.

4. Severe Cold or Wet Weather: Weak calves born during cold, wet weather with little brown fat can quickly develop hypothermia (low body temperature) and are unable to stand or nurse until warmed. A warm water bath, blow dryer, heat lamp or floorboard heat can quickly warm a cold calf. Beware of heating pads as they can cause burns.

5. Infectious Causes-Bovine Viral Diarrhea (BVD) Virus and Leptospirosis: Both the BVD virus and the spirochete Leptospira interrogans serovar hardjo infections have been implicated in weak calves. If the cow is infected with the BVD virus during gestation, there may be multiple congenital defects such as a domed head, cleft palate, cataracts and other eye defects, hydrocephalus and other brain abnormalities in the affected calf. The involvement of Leptospira organisms in weak calves is not well understood but they have been isolated and are undergoing further study.

If pregnant cows in the herd have been losing weight, especially in late gestation, it is best to prepare for the birth of weak calves. Several measures should be instituted immediately to save as many calves as possible:

1. Check heifers and cows in labor frequently (at least 2-3 times daily) – Although producers are accustomed to watching heifers closely for calving difficulty, this recommendation should be extended to all cows. Once the water bag or hooves appear, the calf should be born within an hour. If the cow is not making progress, call your veterinarian for help. If signs of labor are observed for 6-7 hours and the water bag does not appear, the calf may be breech (tail first). Again, call for help quickly for a better chance to have a live calf.

2. Provide shelter during harsh winter weather – Unrolling hay on the ground where there are windbreaks or wooded areas provide some protection during times of intense rain and cold. A shed or barn can be beneficial but remember organisms that cause calf diarrhea build up very quickly in those protected areas. Barns should be clean, dry and well-bedded if used for calving. If cows were not vaccinated with scours vaccine prior to calving, there are products available to give the calf by mouth at birth to aid in scours prevention.

3. Identify the weak calves and institute special care – If the calf is slow to stand and nurse, intervention is necessary. It is important to dry the calf off, dip or spray the navel with disinfectant, warm the calf, and feed colostrum with an esophageal feeder. Have a good quality commercial colostrum replacement (NOT supplement) on hand and ready to mix and feed. Do not delay because the longer the interval from birth to feeding, the fewer antibodies absorbed by the calf. If you observe a calf frequently attempting to nurse, it is unlikely to be getting enough milk and may need supplementation.

4. Test your hay then evaluate the protein and energy in the ration and address any deficiencies. Body condition score the cows and heifers due to calve in the next 60 days to evaluate their needs. In addition, remember that lactating cows have the greatest need for energy because they are producing milk. If at all possible, separate cows according to their nutritional needs and feed them accordingly. Creep feeding calves will help the older calves continue to grow and lessen the burden on the lactating dams.

5. Do your best to feed in different spots to avoid creating areas of deep mud. Calves and weak cows will get stuck in deep mud and die. Similar to the La Brea tar pits, mud is very sticky and will trap weaker animals until they die of exhaustion or fall prey to a predator. Fields can be fixed when winter is over.

6. Diagnose the cause of unexpected death in newborn calves. Contact your local veterinarian and submit any calves that die due to unknown causes to the UK Veterinary Diagnostic Lab or Breathitt Laboratory in Hopkinsville.

The best strategies to prevent weak calves next calving season are a solid vaccination and deworming program, proper nutritional management, and avoiding dystocias. Not only will calf survival improve but pregnancy rates will increase as well. Keep the following points in mind:

1. Vaccinate cows at least 4-6 weeks before breeding with a 5-way viral respiratory vaccine (IBR, BVD Types 1 & 2, PI3, BRSV), with Vibriosis and the 5 strains of Leptospirosis. Consult your veterinarian about testing the herd for persistent infection with BVD virus.
2. Test your hay and plan to provide enough protein and energy for cows and heifers with a balanced ration based on the stage of production (lactation, mid- or late gestation). Ensure a clean, uninterrupted water supply 24 hours a day, 7 days a week.
3. Maintain a body condition score of 5 for cows (up to a 6 for heifers) to ensure adequate condition at calving.
4. Allow cows access to some form of shelter in case of bad weather when calving. However, if unable to keep this area clean, calves are far better off being born outside in a grassy area.
5. Have enough help on hand at calving to watch cows, assist with calving and treat weak calves if necessary. A strong relationship with your local veterinarian is exceptionally important for difficult calving situations and the evaluation and treatment of weak calves.