O level Notes : Agriculture- Cattle management & Disease control

The rearing of cattle, sheep and goats is farming practice that has been practiced over many years. Goats, cattle and sheep are amongst the most widely consumed livestock with valued meat products. Throughout the decades, farmers and animal breeders have come up with a number of livestock breeds with carefully selected traits and improved characteristics.

Disease control


Observation of strict hygienic practices is a vital in prevention of disease prevalence. Clean fresh water and feeds should be provided to livestock.

Control of parasites in disease control

Parasites are living organisms that survive and benefit on taping food reserves and blood from other organisms without the host animal benefiting. The parasites deprive the animal of the nutrients obtained from feed. Some parasites act as vectors of diseases and may cause damage to internal and external organs. To eliminate possibilities of parasitic disease outbreaks, it is very important to control internal and external parasites. Parasites are controlled through dosing, spraying and dipping.

Deworming or dosing

Deworming is the killing of internal parasites which affect the internal organs or digestive system of the livestock or absorption of nutrients. Ruminant animals are de-wormed by dosing using Anthelmintics such as ranide, trodax, valbazen, and ripercol. Ruminant animals are forced to drink the drug using a dosing gun. Dosing should be done in October at the onset of the rains, then in January during the rainy season and in April after the rainy season.

Internal parasites affect the growth rate or weight gain of calves, kids or lambs, damage the internal organs and affect the absorption of nutrients in the small intestines. Therefore, it is important to control internal parasites in ruminant animals.

Control of ticks

Ticks are vectors of diseases and through their feeding results in damage to the hide and loss of livestock weight.As a management practice, farmers should control ticks regularly by dipping the cattle or walking them through a spray race with chemical acaricides.

Dipping or spraying cattle

Farmers should regularly dip or wash their cattle in acaricides at weekly intervals during the rainy season (November to April). Between May and October chances of tick infestations are less severe, therefore, cattle is dipped or sprayed every two weeks.


Cattle have natural periods of breeding when the animals are sexually very active. Mating of animals can be controlled by the farmer as a way of producing best economic animal breeds. Selected animals can be made to mate naturally or the farmer can carry out artificial insemination. With artificial insemination, a syringe with a bull’s semen containing sperm is inserted through the vagina by the farmer and semen is injected.

Examination of pregnancy

Farmers and experienced personnel should physically examine the cows to diagnose for pregnancy. Knowing pregnant and non-pregnant cows is very important for feed management and for monitoring throughout pregnancy.


Castration or gonadectomy refers to the processes that remove the ability of a bull to reproduce by depriving the animal of using its testicles. The bull will no longer be producing sexual hormones and sperms. A castrated bull is known as a steer.

The main reasons for castration is to prevent breeding of inferior breeds and to improve meat quality for beef breeds. Farmers who use cattle as draught power castrate bulls to make them easier to handle as they become more docile. Castration is more easily done on calves than on mature bulls.

Castration methods

Castration methods mostly used by farmers are the burdizzo clamp method, rubber ring and surgical or knife method. The choice of method depends on the safety to the farmer as well as the skills available. Castration using burdizzo clamps (emasculator)

The most common and widely used method of castration by farmers in Zimbabwe is the use of a burdizzo. A burdizzo should be used on calves that are over a month older and it works by crushing the vas deferens as well as cutting blood supply to the testicles. It is the best method to use where flies and muddy conditions prevail, because the steer will be safe from infections.

When using the burdizzo method, the spermatic code is located first by feeling with the hand. The spermatic code is then guided to the outside edge of the scrotum. The jaws of the burdizzo are then placed over the spermatic code about 1.5cm to 2cm above the testicle and the tool is clamped down. The burdizzo clamp should remain clamped for at least 10 seconds. The procedure is done for each testicle on the bull.

Castrating a bull using a burdizzo clamp

Rubber ring castration method

The rubber ring method, also known as the elastic band castration, makes use of a thick rubber ring and an elastrator for stretching the rubber ring wide enough to be placed in position on the testicles. The method is used on calves less than three weeks old.

Rubber ring works by cutting off blood supply to the testicles and killing the testicular tissue. The testicles will fall away in about seven weeks from castration, if the rubber has been properly placed.This method has increased chances of infection and subjects the animal to a lot of pain. The animal may even lose weight during the period when the rubber ring is in position. For ethical reasons some countries have banned this method citing it as inhumane. elastrator

 Surgical (knife) castration method

The surgical or knife method involves the use of sharp knives or surgical blades to make incisions on the testicles to remove all testicular tissue. The equipment as well as the scrotum must be sterilized first before the operation. In farms where animals are housed under muddy conditions, the method is not recommended because of increased chances of the wound getting infected. The animal must be properly restrained before the operation, as the knife method subjects the animal to great pain which may compromise the safety of the farmer carrying out the operation. Animal blood loss can be high in this method.

Chemical castration

This is another method of castration but it is not yet in practice. There has been a lot of research on the possibilities of injecting chemical products that terminate sperm production in animals. Chemical castration remains an option even though commercial products are not yet available.


Weaning is a process of stopping calves from suckling. It is normally done at about 8 months of age. Farmers can wean through physically separating the calves from the mothers. The calves will be moved to pens where food is supplied. Alternatively, calves can be weaned by placing nose plates on the calves for a week or for two weeks to prevent them from suckling.

Branding and identity marking

Cattle need to be marked or numbered for easy of identification and management. Cattle are marked or branded using a hot iron which leaves a permanent mark or brand on the cattle that is specific for the farm.
Farmers also place numbered plastic tags on the cattle ear. This makes identification of individual cattle easier and more practical. Ear notching can also be done on cattle to number them for identification purposes.

Record keeping

Keeping and maintenance of records is a very important aspect of the farm business management. Physical and financial records for cattle management are very important tools for planning, decision making and adjustments in management to maximise productivity.

Types of records in beef cattle management

Stock register

A stock register is a form of physical record that shows current number of livestock in stock, type of animals, age, deaths, sales made and purchases of new animals.

 Dairy cattle breeds

Dairy cattle breeds kept for commercial milk production in Zimbabwe are mostly exotic cattle breeds such as Guernsey, Ayrshire, Jersey and Holstein Friesland. The most common breed in Zimbabwe being the Friesland also known as Holstein, with a distinct black and white colour. Indigenous cattle breeds reared traditionally are dual purpose, that is, they are both meat and milk breeds.

Dairy cattle breeds management requirements are much higher. More skilled labour is required, nutrition management standards are high, record keeping is very critical for individual cattle and heifer and calf management is more complex, when compared to beef cattle. Success of dairy farming heavily depends on the management of the cattle.

 Jersey dairy cattle breed

 Jersey dairy cattle breed originates from Jersey Channel Islands.

Characteristic features of the Jersey cattle breed

  • Colour is a fawn shade
  • Small sized breed
  • Horned with short horns inclining forward
  • Hardiness is very good
  • Produce high quality milk
  • Milk has high fat content
  • Milk yields are medium

Holstein or Friesland cattle breed

The breed originates from Netherlands and Holland.

Characteristic features of the Friesland cattle breed

  • Large animal breed
  • Breed has well defined black and white markings
  • Friesland has uncurving horns inclining forward
  • Hardiness is good
  • Milk quality is fair
  • Friesland has high milk yields

Ayrshire dairy cattle breed

Ayrshire dairy cattle originates from Ayr in the southwestern part of Scotland

Characteristic features of the Ayrshire cattle breed

  • Light deep red to mahogany, can also be white or mixed colour of deep red and white
  • Medium sized
  • Horned
  • Hardiness is good
  • Milk yields are medium
  • Milk quality is good

The Jersey and Guernsey breeds both originate from the Channel Islands and are commonly referred to as channel island breeds. Their characteristic features are similar. These breeds produce the best quality milk than Friesland. However, milk yields for channel island breeds are lower than those from Friesland breeds.

Management practices for dairy cattle

Dairy cattle breeds require much closer attention and monitoring than beef cattle breeds. The farmer and workers should know each cattle individually and in detail. Understanding each animal’s behaviour patterns helps to detect critical periods in the cattle such as the oestrus period when cows come into heat or are sexually receptive.Management practices for dairy cattle breeds include feed management, calf rearing, heifer (cow) management, selection and breeding, milking, record keeping and disease control.

Dairy cattle feed management

The feeding of dairy cattle should follow a strict program that meets the nutritional requirements of each cattle. Feeding is important to maintain the animal weight and milk production. For a dairy cattle to produce milk with a high fat content it requires more food. The quality of feed and amount of nutrient content is measured using the total digestible nutrients (TDN) and the crude protein (CP) in a kilogram of feed. Information on nutrient content of feed is usually provided by the feed manufacturer.

The farmer’s task is to calculate the amount of feed to be given to the animal with standard amount of nutrients to produce milk with 3.5% fat content, because the higher the fat content the higher the quality of the milk. A typical dairy cow requires 0.304 TDN and 0.082 CP in a kg of feed. Feed nutrient specifications can be obtained from feed analysis charts that can be bought for reference.

Dairy cows are fed just after milking. Each cow is fed individually. Feed costs for dairy cows are higher than for other cattle. Heifers can be allowed to graze or alternatively fresh grass is cut and transported to the milking parlour.

Calf rearing and management

Feed management

Dairy cows produce milk after successfully giving birth to calves. The calves will not be allowed to suckle on the mother as in beef calves. Dairy calves are allowed to drink the first milk produced by their mothering cows only within 24 hours of birth. It is very important that the calves drink a lot of colostrum in the milk to boost their immunity to diseases.

The calves are then hand-fed with milk substitutes. These milk substitutes are very expensive and, therefore, it is wise to wean the calves in good time, from five weeks onwards. A daily supply of about 3 litres milk and calf starter meal containing 19 % crude protein is given for the first week. From 1 week onwards, hay and water should be supplied. Once the calf starts to consume half a kilo of starter meal, it should be weaned off from milk.

Weaned calves should have access to quality fresh grazing with proper grazing rotations to avoid infections and parasites. After weening, feed is changed to calf growth meal with a lower CP content of 16 % as compared to calf starter meal. A daily supply of about 2kg per calf will be adequate.

Housing for the calves

Young calves require safe and good housing with high standards of hygiene and ventilation. The calves are usually housed in individual crates that are 140cm long and 90cm wide. In good weather conditions, crates can be placed outside, but under harsh weather, it is best to place the crates in shades that are draught free. Calves can also be housed in groups of the same age with number not exceeding five. In this system each individual calf should be allowed a free space of 1.4m x 1.8m.

Heifer management

Heifers are cows that are for milk production. They can be dry (not in production) in preparation for the next calving and milk production. Proper records are important in managing the inter-calving period which is the period between giving births by the cow. The heifer must not be dry or unproductive for too long since the feeding expenses for dairy cows are high. A typical dairy cow should have 310 lactating days and a dry period of 55 days in 365 days.

When heifers are over 15 months, they can be mated or the farmer carries out artificial insemination. Mating the heifers earlier than 15 months usually produces less and poor-quality milk.

Heifer feed management

Feeding of dairy cows (heifers) is usually done with concentrates and supplementary fresh feeds. In a heifer feeding programme, feed concentrate percentage is increased in winter and reduced in summer when natural feeds are abundant. A farmer should know each individual heifer and its history to be able to design an appropriate feeding programme to meet the nutritional demands and production targets.

Heifers differ in their lactation stages and a farmer should factor this in, when preparing feeding programme for heifers in early lactation, peak lactation, from 6 weeks after calving and heifers with declining milk production towards drying off.

Heifers that are at peak milk production and those that produce quality milk with high fat, protein and minerals require more food.

Cattle selection and breeding

During the rearing of dairy calves, calves with good economic and physical appearance are selected for mating. Those that are not good for production are culled or sold. Basic characteristics that are looked at are milk yields, appearance of the udder and quality of milk as measured by fat and protein content, and posture.

The main reason for breeding is to multiply volumes of milk production.

The most important aspect of heifer management is the ability to notice animals in heat in good time. Missing the heat will be very costly as this lengthens the unproductive period of the dry heifer.

Signs of heifers in heat

Heat refers to a sexually receptive state of an animal that is triggered by hormones or body chemical signals. During this period, the animal is sexually very active and the chances for successful fertilization are very high. An animal in heat shows certain behavioural patterns which should be noticed by a farmer, and some include those listed below.

  • The cow is restless.
  • Cow will mount other cows.
  • Animal will keep standing in position when mounted by other cows.
  • Vulva becomes wet and swollen.
  • Milk output declines.


Naturally, mating occurs when a bull picks up females in heat through smells of hormones passed out in urine.

Selection of a bull depends on a farmer’s choice.

A bull mounts a cow in heat from behind forcing its erect penis through vulva into the cow’s vagina. Pressure on the penis stimulates release of semen in the vagina. Sperms then travel towards ovary through the oviduct where fertilization takes place.

Artificial insemination

This is a process of artificially placing sperms into the vagina using a catheter or an inseminating tube. The sperm is collected from bulls with proven and confirmed breeding qualities using an artificial vagina. Semen or sperm is stored at very low temperatures in nitrogen containing flasks. Sperm for artificial insemination (AI) is sold commercially and a farmer may not need to keep a bull on the farm.


Milking of dairy heifers is one aspect of dairy cow management that is critical, as this determines volumes of income from sales of the milk. Milking is done by hand where the herd of cattle is small. In large commercial dairy milk production farms, cows are milked by machines using an electrically operated milking machine. Specialised equipment and milk storage facilities should be sound. A milking parlour design should allow smooth flow of cows into and out of the parlour in one flow of direction.

Dairy cows are milked twice a day. Milking is first done early in the morning from 5am. The second milking is done late in the afternoon from 3pm. Timing also depends on the size of the dairy herd. During the milking process, care should be taken not to damage the udder and all milking equipment must be properly sterilised to avoid infections and contamination of the milk.

 A skilled worker can milk four to five cows in an hour.

Milking machines are more efficient. A single milking unit is comprised of two sets of four teat cups. Each unit can accommodate two cows at the same time.

 A cow can be injured if machines are left for too long on the udder. The cow should be handled gently and should not be stressed. Soon after release from the milking unit, the cow moves to feeding area where it is supplied with a ration feed of concentrate feed and silage.

Disease control

Dairy cattle are affected by parasites and diseases that affect beef animals, and most disease control practices are similar. Tick control for dairy cows should be done once every week through a spray race to minimize stress on the animal. Contagious abortion and Quarter evil are diseases that negatively impact on dairy production. Vaccination or inoculation against such diseases will help to keep the diseases at bay. The most important disease of concern in dairy farming is mastitis.


Mastitis is a bacterial disease which causes inflammation of the udder. This disease affects quantity and quality of milk. The disease is controlled by:

  • High level of hygiene standards
  • Early identification and treatment of infected cows
  • Culling of infected animals
  • Correct milking procedures
  • Proper disinfection and maintenance of milking machines

Detection of mastitis

Mastitis can be detected by using the somatic cell count method, visualization and palpation of the udder.

Somatic cell count

Animals respond to infection by producing white blood cells (leukocytes) that flow towards infected area. Mastitis is an inflammation of the mammalian gland. In mastitis, white blood cells increase in concentration on the udder depending on the level of infection. White blood cells detected in milk are referred to as somatic cells. Mastitis somatic cell counts can be done on temporary bulk storage tanks and on individual cows. Normal cell count should be 10 000 per millimetre and a farmer should maintain the count at 3000 per millimetre.


Visualization is another method of detecting mastitis.Visualization is done by stripping the first squirts of milk on to a strip cup for detecting flakes and clots in the milk. There are noticeable changes in the milk such as presence of flakes, clots and serous milk. Swellings on the udder can also be noticed.

Record keeping

Dairy farming is a very expensive venture that is also labour intensive and would require proper record keeping. The records must be simple and easy to interpret. Examples of a dairy cow’s records are:

  • Financial records
  • Animal performance
  • Production records
  • Breeding records
  • Stock register
  • Feed records