1Dixit K. Parasana,2P. M. Makwana, 2D. R. Patel, 3I. H. Kalyani

1Ph. D. Scholar, 2Assistant Professor,3Professor and Head,  Department of Veterinary Microbiology, College of Veterinary Science & Animal Husbandry, Navsari

The causes of calf mortality can be divided into infectious and non infectious. Infectious causes include diseases caused by bacteria, viruses or protozoa. The major non-infectious causes are dystocia, improper feeding of colostrum, low birth weight and poor management practices.

Infectious causes

These can be due to any of the following types of microbes:

Rotavirus: Rotaviruses are the most common cause of diarrhoea in neonatal calves between the ages of 4 and 14 days. It is also possible for younger and older calves to become infected with rotavirus. The virus specially attacks the epithelium of the small intestine of young calves. The virus replicates in intestinal epithelial cells near the tips of the villi. Calves infected with rotavirus show watery diarrhoea. The diarrhoea can vary in colour from yellow to green. Infected calves become severely depressed and dehydrated.

Coronavirus: Coronaviruses are one of the most common causes of diarrhoea in calves. It usually affects calves that are between 4 and 30 days old. There are at least three different types of coronaviruses that affect calves, causing diarrhoea, respiratory infections and winter dysentery. Coronavirus infection of the intestine in calves causes profuse watery diarrhoea. Affected calves become dehydrated very quickly and develop a fever and loss of appetite. Incidence of coronavirus in neonatal calf diarrhoea is slightly lower than rotavirus.

Escherichia coli (E. coli): These organisms are part of the normal flora of the intestinal tract. Many strains are harmless to the calf, but certain strains can cause moderate to severe scours and even death. E. coli affects calves within the first 10-14 days of age, usually within the first week. E. coli is often referred to as “white” scours and is the most common cause of calf scours.

Salmonella: Salmonella infections are most frequent and of great concern to young animals. This rod shaped, gram negative organisms are usually motile and produce gastroenteritis with nausea, vomiting, cramps and diarrhoea. The organism can affect calves of any age, but usually affects calves that are over 10 days old. The organism invades the mucosa of the small intestine causing inflammation and erosion of the intestinal lining.

Coccidiosis: There are many species of coccidia – Eimeria zurnii and Eimeria bovis are usually associated with clinical infections in cattle. Coccidiosis has been observed in calves 3 weeks of age and older, usually following stress, poor sanitation, overcrowding or sudden changes of feed. These organisms enter the body through contaminated feed and water. They can remain dormant in manure and soil for up to one year. After entering the intestine, the oocysts (eggs) release protozoa that multiply. They enter into the cells of the intestinal lining decreasing digestion and absorption of feed ingredients. Sub-clinical (chronic) infections show few outward signs, but animals suffer reduced feed consumption, feed conversion and growth. Acute infections result in diarrhoea (often with blood), depression, weight loss, dehydration, but calves will often continue to eat.

Non-Infectious causes:

Improper colostrum feeding: Adequate colostrum feeding provides essential immunoglobulins to the calf. Absorption of immunoglobulins continues up to 48 hours in calves, but maximum absorption occurs within the first 6-8 hours of life. The maternal antibodies protect the calf during the initial 6 months of its life when it is most vulnerable by a process called passive immunity. Compared to hand feeding, suckling is a greater source of absorption of colostral immunoglobulins; therefore, it is generally recommended to allow the calf to suckle its mother for the first two days post-partum. High mortality and morbidity due to diarrhoea, pneumonia and other diseases occurs in immunodeficient calves which do not consume adequate colostrum immediately after birth.

Season of birth: Season has a significant effect on the calf mortality. In a report 40 per cent of total deaths on a farm were recorded during winter season (December to February). Change in climate and severe cold waves results in stress in immunodeficient calves and they become prone to other infections.

Dystocia: This is a major cause of calf mortality due to the tremendous stress that occurs on the calf during a difficult birth. However, research has shown that calving difficulty has long term effects on the immune status of the calf. Hence, calving difficulty has the potential to reduce the passive immunity of the calf and, thus, make it more susceptible to disease. Dystocia is mainly due to abnormal presentation of calf especially posterior and breech presentation. Incidence of dystocia is higher in primiparous dams than in multiparous dams and is also significantly higher when the calf is male.

Sex and birth weight of calf: Mortality is higher in male than in female neonatal calves. Reason for this higher mortality might be due to the fact that absorption of colostral immunoglobulins is less in male than female calves. Birth weight of calves also significantly affects mortality. Too low birth weight and too high birth weight caused greater mortality in calves. Calves having higher birth weight had calving difficulties, whereas those with very low body weight had lesser ability to handle environmental stresses and diseases

Management factors: In calf houses, poor ventilation, overcrowding, inadequate cleaning and disinfection predispose the calves to various diseases, especially those affecting the respiratory tract. Tympany and milk indigestion also play an active role in the neonatal calf mortality. Calves should be allowed to move freely in open spaces and exposed to sunlight to get sufficient Vitamin D. Naval disinfection and removal of mucous from the mouth and nose reduces mortality and morbidity rates in calves.

Control strategies to reduce calf mortality:

General management before birth: The care of calf starts in the womb of animal itself. The maximum growth of calf takes place during the last trimester of pregnancy. So balanced feeding of cow during the last trimester will give birth to a healthy calf and increase in milk production in the subsequent lactation. Feeding of animals during pregnancy with balanced ration including mineral mixture and vitamins will prevent deficiencies in both the cow and the calf. It will also take care of other associated problems like retention of placenta, lazy calving, dystocia, milk fever, calf death and poor calf health.

Care of calf after birth: After the birth of the calf, remove the mucous from its nose and mouth and stimulate breathing. Allow the dam to lick her young one soon after birth to induce maternal instinct and help in cleaning and drying of the newborn. Cut the navel cord about 2 inches away from the abdomen with a sterile blade, ligate it and apply strong tincture iodine solution (7%). Feed colostrum at the rate of 10% of body weight per day in divided doses for the first 4-5 days. Provide a clean, dry resting surface for the calf to ensure that its hair coat stays dry. Protect it from exposure to cold surfaces, low air temperatures and sudden temperature changes. Provide at least 6 inches of bedding as a cushion to minimize physical trauma.

Feeding of calves after birth:

Nutrition and management of neonatal calves has a great impact on their later productivity and longevity. It is essential to feed colostrum to the young one immediately after birth in order to ensure development of adequate immunity until it can produce its own antibodies. Colostrum also has a laxative effect and helps to clear meconium from the gut of the calf. It is a good source of vitamins, minerals, protein and energy. It contains 3-5 times more protein the normal milk and 5-15 times more Vitamin A. At two weeks of age, the calf should be introduced to good quality green fodder and concentrates, as a calf starter. This stimulates the rumen to grow and function properly.

Calf starter mixture: A typical calf starter mixture should have easily digestible good quality low fiber feed. It should contain 22 per cent crude protein and have a TDN of 70-75%. The ingredients used for preparation of calf starter should be of good quality and free from any detrimental adulterants. At the age of 3 months the rumen is developed substantially and microbial digestion takes place in rumen. A palatable ration containing 13-14% CP and 60-62% TDN is required for normal growth. From six month onward the animals can be transferred to coarse fodder and straw based ration.

Deworming: This is one of the most important management practices followed to prevent mortality in calves. Internal parasites in the calf cause diarrhoea, stunted growth, rough skin and a pot belly shaped abdomen. Worms causes huge losses to dairy farmers in terms of feed loss, growth loss and mortality of calves. So it is necessary to deworm the calves at regular intervals to prevent parasitic infection. Growing calves also need to be protected from external parasites like lice, ticks, mites etc. by spraying of animals and livestock sheds with ectoparasiticides regularly.