Early Calf Mortality and Care During Winter Months

Authors: Dr Muhammad Usama*, Dr Muhammad Rehan, Dr Faisal Ramzan, Dr Safdar Hassan
Institute of Animal and Dairy Sciences, Faculty of Animal Husbandry, UAF
Corresponding author’s email: m.usama@uaf.edu.pk

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Key Message: Healthy calves today are the foundation of a profitable dairy tomorrow. In young calves there is almost 30% mortality in Pakistan – most of it preventable through better colostrum feeding, winter management, and disease control.

Why Early Calf Care Matters

The management and health of calves directly determine the future productivity, reproduction, and longevity of the herd. The genetic potential of the herd is expressed through well-reared calves that grow into superior dairy cows or breeding bulls.

Calf mortality or poor growth leads to financial losses due to replacement cost, delayed breeding, and reduced milk yield later in life. Proper colostrum feeding, nutrition, and disease control during the calf stage establish a strong immune system that helps the animal resist infections throughout its life.

In dairy farming, milk accounts for about 60% of the income, while the increase in calves and inventory value makes up the remaining 40% of the income.

Seasonal Effect on Calf Mortality

Impact of Cold Stress on Young Calves

Low ambient temperature increases the risk of pneumonia and diarrhea due to suppressed immunity. Growth rate becomes slower because more energy is spent on maintaining body heat rather than growth. During winter, low temperature, high humidity, and cold winds increase the risk of cold stress.

Respiratory diseases such as pneumonia tend to be worse during winter and early spring. Calf mortality also tends to increase during cold, wet, and windy winter weather because:

Maintenance energy requirements are much higher in a cold environment.
Antibody absorption from colostrum is less efficient during winter.
Lice, mange mites, and ringworm fungi prosper in confined, damp environments and with poor nutrition.

Regular observation of young calves is critical so their diets may be altered, if necessary, to sustain energy levels during these conditions. Health management for dairy calves during cold weather means more intense management procedures.

Some important tips include: better dry cow care, careful calving-time care, ensuring adequate colostrum intake, using high-fat milk replacer (greater than 10% fat), providing a dry and draft-free environment, and checking calves at least twice each day.

Why Calves Are More Sensitive to Cold

Calves have limited ability to regulate body temperature because of:

Thin skin and low body fat reserves.
Large body surface area relative to weight.
Immature thermoregulation system.

Calf Scour / Diarrhea Due to Low Temperature

Calf scours during the first month of life are the most common cause of calf sickness and death. Several pathogens, including E. coli, rotavirus, coronavirus, Salmonella, coccidia, and Cryptosporidia, cause calf diarrhea. These agents can be present year-round, but under conditions of crowding, cold stress, inadequate nutrition, and less frequent manure removal, calf scours can become a herd problem.

The best cure for scours is prevention. Calves should be fed correctly and housed in a clean environment. Calves with scours should be treated immediately with a homemade or commercial electrolyte solution to keep them from dehydrating.

Milk should not be fed when scours occur because milk may encourage growth of bacteria in the intestine and further complicate the scours. Milk or milk replacer should be replaced with an electrolyte solution for no more than 24 to 48 hours.

Calf Pneumonia Due to Low Temperature

In calves, pneumonia is usually caused by Pasteurella multocida, Pasteurella haemolytica, Staphylococcus epidermidis, Streptococci, Pseudomonas aeruginosa, Corynebacterium pyogenes, Mycoplasma, Pest virus and herpes virus. There are two types of pneumonia: proliferative and exudative.

Environmental factors that predispose calves to pneumonia include:

Transportation and movement stress.
Temperature extremes.
Crowding of calves in a small area.
Poor ventilation in sheds or calf pens.

The immediate causes of pneumonia are bacteria and viruses, but of greater significance are predisposing factors such as dampness, drafts, chilling, and toxic gases. The accumulation of gases in confinement housing irritates the respiratory tract. Ammonia is one of the major irritants. When the smell of ammonia is noticeable, there is a high probability of damage to the lung defense mechanisms of these confined animals.

Effect of Colostrum to Avoid Early Calf Mortality

Early colostrum feeding has three important characteristics: nutritive, laxative and prophylactic. Colostrum feeding is actually immunoglobulin feeding. It has three types of antibodies:

IgG (70–80%)
IgM (10–15%)
IgA (10–15%)

The absorption efficiency of colostrum is about 30% in the first 12 hours. The immunoglobulin concentration of 10 g per liter of blood plasma should be achieved in the first 12 hours.

In the small intestine, an absorptive competition occurs between the immunoglobulins and intestinal germs for the occupation of intestinal receptors. If pathogenic bacteria occupy the receptors then hypogammaglobulinemia occurs in calves, which results in decreased passive immunity and makes the calves more prone to different diseases.

Therefore, there is high morbidity and mortality due to diarrhea, pneumonia, etc. in immune-deficient calves. Season of calving also has a great impact on the absorption of immunoglobulins in calves. A research trial on the effect of season on the absorption of immunoglobulins showed that in temperate areas, the serum IgG concentrations were lowest in winter-born calves and increased during the spring and early summer.

Management to Avoid Calf Mortality During Winter Months

Practical Winter Management Tips

Feed warm milk at 38–40°C and increase energy content of feed.
Ensure timely colostrum feeding within the first 2 hours after birth.
Provide warm, dry, and draft-free housing with thick bedding (straw or sawdust).
Keep drinking water at lukewarm temperature (20–25°C).
Avoid overcrowding and ensure good ventilation without cold air drafts.

Feeding Chart for Calves in Early Life

Age	Milk	Calf Starter	Water	Fodder
Soon after birth	2–4 kg colostrum	–	–	–
1–2 days	2–4 kg colostrum	–	–	–
2–4 days	2–4 liters milk	–	Yes	–
4–7 days	3–5 liters milk	50–100 g	Yes	–
7–14 days	3–5 liters milk	100–150 g	Yes	–
2–8 weeks	Decrease milk quantity gradually	1–1.5 kg	Yes	Soft fodder
9 weeks	0	1–1.5 kg	Yes	Soft fodder / concentrate

By combining timely colostrum feeding, proper winter housing, and careful nutritional management, dairy farmers can significantly reduce early calf mortality and build a stronger, more profitable herd for the future.