Calf rearing

Calf rearing is an important job on the dairy farm. Remember the young calf is the future of your dairy herd. Calves that receive inadequate attention during the first few weeks of life:

Will not meet liveweight targets thus delaying age at first calving
Are more prone to disease
Cost more to rear

Attention to detail is the critical component of any successful calf rearing regime. This includes preparation of the cow for calving, monitoring the birth, providing suitable housing for calf rearing, a proper feeding regime for the animal, a disease prevention program in conjunction with a strict hygiene code of practice and the use of veterinary assistance when required.

Managing the cow for a healthy calf

Ensure that the cow is dried off six to eight weeks before calving. Target condition score for cows at drying off is 2.5 - 3.0. Cows should also receive dry cow minerals where necessary to maintain the required vitamin and mineral status of both cow and developing calf. Particular attention should be paid to the calcium, selenium, iodine and vitamin E status of dry cows depending on the mineral and vitamin status of your farm. Consult your local veterinarian about the need for these minerals and vitamins on your own farm if you suspect a problem.

A number of farmers also use the dry period as an opportunity to vaccinate cows against some of the agents which cause calf scour (e.g. Rotavirus or E. coli). The derived immunity is passed on to the unborn calf. Consult your local veterinarian about the use of such vaccination programs in your own herd. If Rotavirus or E. coli have been diagnosed as a persistent problem, vaccination is recommended.

Consult your vet about the need for vaccinations

Post birth management

Once the calf is born make sure that its airway is clear and that it can breath properly. The navel should be treated after birth with tincture of iodine dip (2 percent) solution to prevent onset of joint ill.

Ensure the calf receives colostrum as quickly as possible after birth

Feeding colostrum

A new born calf has no active immunity and is highly vulnerable to infection. Protection is achieved by ensuring that the new born calf consumes approximately 10 percent of its body weight (around 3.5 - 5 litres depending on the calf’s birthweight) of colostrum within the first six hours after birth. Colostrum is produced by the cow before and shortly after the birth of the calf and is rich in nutrients for the new born calf. It also contains immunoglobulins (antibodies) which will provide the calf with immunity to infection. The effectiveness of colostrum in providing immunity to the calf is greatly affected by:

Timing of the colostrum intake - the ability of the calf to absorb immunoglobulins decreases rapidly after birth (Figure 1). Calves should receive around 3.5 - 5 litres colostrum within six hours of being born. Keep a supply of frozen colostrum which can be used if none is available at the time to feed to new born calves.

Figure 1. Effect of Feeding Time on Immunoglobulin Absorption

Effect of Feeding Time on Immunoglobulin Absorption graph

Source: Pennsylvania State University, USA

Quality of the colostrum - The percentage of antibodies in colostrum decreases rapidly with each milking. Usually the second milking has only 60 - 70 percent of the immunoglobulins contained in the first milk. Calves should receive the first milk produced from the dam. The number of pregnancies that the dam has had also affects the quality of colostrum. Older cows have been exposed to a greater number of infections than first calved heifers and so have higher concentrations of antibodies in their colostrum. The quality of colostrum is reduced by the presence of dirt or other debris leading to contamination. Always ensure that the cow’s udder and teats are clean before the first feeding.

Calves are unable to absorb antibodies from the intestine after 24 - 36 hours. From a health management perspective calves should continue to receive their dam's milk for up to the first 14 days of life to provide local immunity against pathogens that may be present in the gut. However seldom on the practical farm situation is this possible with calves being fed other sources of milk after a few days.

REARING THE CALF (BIRTH - WEANING)

Feeding milk

Calves can be fed either whole milk or milk replacer from three days after birth. Milk or milk replacer should be gradually introduced over a period of four days.

Whole milk is fed to calves on many dairy units, especially in situations where the farm's milk supplies may exceed the allocated quota. Feeding whole milk to calves can replace part of the concentrate portion of the diet particularly for older calves. If high rates of whole milk feeding (10 litres per day) are continued beyond six to seven weeks then supplementary minerals and vitamins are required.

The two main types of milk replacer are:

Skim based milk replacer
Zero skim milk replacer

Good quality skim based milk replacers contain 50 - 60 % skimmed milk powder. The protein within the reconstituted milk forms a clot in the calf's stomach, slowing its release which in turn reduces the risk of digestive upsets and minimises the incidence of scour. Acidified versions of skim milk replacers have been shown to further reduce the incidence of scour. Skimmed milk powders suit bucket and machine feeding systems.

Zero skim milk replacers contain whey and whey protein based concentrates along with some soybean or other vegetable proteins. This type of milk replacer can give similar levels of performance compared to skimmed milk powders and in some situations is more cost effective. Zero skim milk replacers do not form a clot in the calf's stomach. As a result there is a risk of overloading the calf's small intestine if this replacer is fed infrequently. Therefore care should be exercised to avoid overfeeding this type of replacer on a twice a day feeding system to calves under four weeks of age.

When using milk replacer it is important to follow the manufacturers' mixing and feeding instructions properly. It is particularly important to feed the milk at the correct temperature as this can affect the willingness of the calf to drink the milk and the incidence of bloat. Feeding milk replacer at the incorrect temperature can also cause fat breakdown or affect the protein quality of the milk replacer. Calves can be fed milk using:

Twice a day bucket systems
Cold ad lib feeding (using acidified milk replacers)
Machine ad lib feeding (warm milk)
Computer controlled machine feeding

Computer controlled machine feeding

Basic guidelines for systems of feeding milk replacers are given in Table 6

Table 6. Systems of feeding milk replacers

	Mixing rate (g/litre)	Mixing temperature (oC)	Feeding temperature (oC)	Amount per feed (litres)	Amount feed per calf per day (litres)
Twice a day bucket	125	40	36	2	4
Cold ad lib (acidified milk replacer)	125	na	na	na	8
Machine ad lib (warm milk)	100-125	na	na	na	8

Bucket feeding systems tend to be used on most calf rearing units as they are simple to operate, calves can be taught to drink at an early age and they are less expensive in terms of cost per KG liveweight gain as ad lib systems use considerably more milk powder. Heifer calves at Greenmount College are fed using a skimmed milk powder based milk replacer (50 - 60 % skimmed milk powder) on a twice a day bucket feeding system.

Dry feed

Calves reared at Greenmount Campus, as on many dairy units, are introduced to a coarse calf mixture between 7 - 14 days after birth and are fed ad lib thereafter through to weaning. Clean, dry hay or straw should be placed in a manger for calves to feed on. This helps the development of the rumen. After a few weeks calves at Greenmount Campus are also offered some fresh silage to allow them to become accustomed to the forage. Calves should have access to clean, fresh water at all times from five days of age onwards.

Dehorning and teat removal

Dehorning should be carried out, using a local anaesthetic, at three to four weeks of age. The horn bud at this stage should be easily felt. Extra teats should be removed at the same time as dehorning. Both procedures should be carried out by an experienced operator. Individuals in any doubt about either technique should seek veterinary advice about recommended techniques

Calf rearing at Greenmount

Weaning

Weaning can be a stressful time for the calf and if not carried out properly can set back progress within the rearing programme. Calves may be weaned as early as six weeks of age, although it is commonplace for calves to be weaned between 8 - 12 weeks of age depending on the availability of milk due to the quota situation on the farm. Making a decision about what stage to wean calves should not be based solely on the age of the animals. Criteria which are used to wean heifer calves at Greenmount College are as follows:

Target weaning age is eight weeks
Calves must weigh at least 65 KG prior to weaning
Calves should be consuming at least 1 kg per calf per day of a coarse calf mixture for three days prior to weaning
Calves to be weaned are healthy and free of disease

The calves will be at least six weeks of age before the weight and intake criteria are met. Heifer calves at Greenmount Campus are weaned in groups of six to eight animals. The calves are grouped together according to age and size from a few weeks after birth. This is carried out to help minimise stress associated with weaning. Weaning occurs over a period of four to five days whereby the amount of milk replacer offered is gradually reduced. The calves are kept on the same silage and coarse calf mix over the weaning period. After weaning calves usually remain in the same pen for one to two weeks. The coarse calf feed continues to be offered ad libitum until concentrate intakes of around 2 KG per calf per day are achieved. The animals are then moved on to a kennel house.

REARING THE CALF (WEANING - FOUR MONTHS)

Calves at this stage are managed to achieve growth rates approaching 0.7 KG per calf per day. This is achieved by maintaining calves on ad lib silage as well as introducing them on to an 18 percent crude protein (CP) rearing compound. Typical feeding rates are between 1.0 - 1.5 KG per calf per day depending on the quality of forage on offer.

REARING THE CALF (4 - 10 MONTHS)

Target growth rates for calves at this stage of development at Greenmount Campus are 0.80 KG per calf per day. This requires a high level of management as calves growing at this age can potentially grow at 1.1 KG per day. Calves are weighed on a monthly basis during the winter to monitor liveweight gain and levels of supplementation are adjusted according to the figures recorded. Silage is offered ad lib.

Target pre pubertal growth rate is 0.8 KG/day

A number of dairy farmers have found that calves at this stage perform well on straw based systems. Levels of concentrate feeding with ad lib straw need to be higher than with silage and vary according to the age of the calf and forage intakes achieved.

CALF HOUSING

Housing is often the weakest link in a calf and heifer rearing program. Important features for calf housing include:

Clean, warm, dry and draught free but not stuffy conditions
Always provide adequate ventilation for calves
Calves aged less than three months should be isolated from older animals
Convenient location to encourage quality care and observation
Minimise manual labour

Pens

Calf pens should be designed to provide a clean environment, which minimises disease risk and hence encourage high growth rates. Calves can be kept in individual pens up to eight weeks of age. There are regulations* regarding space requirements for calf pens. Typical minimum internal dimensions are 1.5 m x 0.75 m for calves up to four weeks of age and 1.8 m x 1.0 m for calves aged up to eight weeks. Individual pens should also have perforated walls to allow the calves to have direct visual and tactile contact with each other.

Pens should be easily dismantled for cleaning

A calf should always have a dry bed. Concrete floors should have a minimum slope of 1 in 20 to allow effective drainage of water and urine. The installation of duckboards on which bedding can be placed will also help to keep the calf dry. A drainage channel at the front of the pen will also help to remove water and urine.

Legislation* is now in place which affects the way calves are managed within pens. For example, the tethering of all calves is banned with the exception of group housed calves which can be tethered for up to one hour per day during milk feeding. In addition calves aged over eight weeks will have to be loose housed unless a veterinary surgeon has certified that they be housed individually for health reasons. Calves in a loose housing system should be able to stand up, turn around, lie down, rest and groom without hindrance. The minimum space allowance for calves weighing less than 150 KG is 1.5 m² per calf in group housing, while the allowance for calves weighing between 150 - 200 KG is 2 m² per calf. Calves weighing over 200 KG should have a space allowance of 3 m² per calf.

There are some exemptions to the regulations outlined. For example calves reared in pens brought into use between 1 January 1994 and 1 January 1998 must have at least one perforated wall. In addition calves weighing over 150 kg and reared in loose housing systems brought into use during the same time period are allocated a minimum space allowance of at least 1.5 m2 per calf. However these systems must be brought up to the level of the original standards outlined* by 2004.

Clean and rest calf pens when possible. Use an 'all-in/all-out' policy when moving calves to prevent cross infection.

Cubicles should be designed to encourage calves to lie in them

Cubicles

Cubicles in calf houses should be designed to encourage calves to lie in them from an early age. Calves should have free access to cubicles. The cubicle should be designed to suit the animal at the end of and not the beginning of the housing period. Suitable cubicle dimensions for calves weighing 75 - 150 KG are 1.5 x 0.7 m.

Hutches

Calf hutches are mainly used for individual accomodation but they tend to provide more space than that offered within a house as many hutches have a covered lying area and an external loafing area. Any liquid runoff from a hutch system must be directed into a slurry store. Many dairy farmers find that calves perform well under this system. However there are some limitations associated with using hutches:

It can be difficult to maintain a dry bed under difficult weather and ground conditions
Regulations* do not permit tethers to be used so systems which use chains will have to be modified to provide an outside run

Ventilation

Adequate ventilation in the rearing house is necessary to:

Minimise levels of airborne infections
Minimise condensation
Aid evaporation from urine and faeces, bedding and water spillage
Remove water vapour
Reduce dust levels
Create even air distribution

Air space should be 6 m³ per new born calf, rising to 12 m³ at three months. Purpose built calf accomodation with natural ventilation should have inlet areas allowing 0.05 m² per calf and outlet areas, 0.04 m² per calf.

Rearing houses should have adequate ventilation

One of the main problems associated with ventilating calf houses is the presence of draughts within the house. Draughts must be avoided at calf level. If pens are arranged along the sides of naturally ventilated buildings then a cover should be placed over the rear part of the pen to prevent air from dropping onto the calves. Natural forms of ventilation such as space boarding with baffling or windows with baffling will also help to avoid draughts at calf level.

Converted buildings often require adaptations such as mechanical ventilation eg., polythene duct air distribution systems with speed controllable fans. Such a system should have an air exchange capacity of 30 m³ per calf per hour in winter and 70 m³ per calf per hour in summer. The fans should be placed above calf height.

Polythene duct air distribution system

In summary all ventilation systems should ensure that the house is draught free and that airflow is above calf height. Always seek professional advice when selecting the most appropriate form of ventilation for your calf rearing unit.

HEALTH CARE

Maintaining healthy calves is the product of good nutritional and housing management in addition to planned disease prevention and control measures. Target growth rates cannot be achieved without an effective health management programme. Scours and respiratory problems are the two main causes of illness.

Calf scour

There are two causes of scour - nutritional and infectious. Symptoms include a change in faeces which becomes liquid with variable colour and smell. The clinically affected calf has a dull appearance with sunken eyes and is often reluctant to feed or drink.

Causes of nutritional scour include:

Lack of colostrum
Too much or too concentrated milk being fed
Milk replacers which are too dilute or not properly mixed
Incorrect milk feeding temperature
Irregular feeding times
Cold, damp, draughty or humid housing

Infectious scours are caused by a number of pathogens. The results of a recent survey of the organisms causing scour in calves on farms in England are summarised in Figure 2.

Figure 2. Causes of Calf Scour

Source: Milk Development Council

Scouring only occurs when the challenge of the infection is greater than the calf's resistance. Scouring is also more likely when the young animal is exposed to more than one type of infection at a time.

Treatment

Isolate the affected calf under a heated lamp in a clean, dry pen with adequate bedding
Monitor the calf's temperature. Ensure that it is kept hydrated and warm
Stop feeding milk where possible
Feed electrolyte solution in place of the milk until the faeces has firmed. If the situation has not improved after 36 - 48 hours seek veterinary advice on the cause of the scour and appropriate treatment
After the faeces has firmed introduce milk gradually back into the feeding regime

Prevention

Ensure that all newborn calves receive adequate colostrum
Use high quality milk replacer and follow the mixing instructions precisely (see Feeding milk)
Power hose and disinfect all calf pens after each batch of calves
Calving boxes should be thoroughly cleaned and disinfected at least twice during the calving season
Avoid mixing calves of different ages and different sources
Keep the stress from dehorning and movement to a minimum
Isolate sick calves
If Rotavirus or E. coli has been diagnosed as a persistent and troublesome problem, vaccinate against these diseases.

Pneumonia

Pneumonia is a respiratory disease that reduces performance and unless treated effectively will result in the death of the calf. Symptoms include rapid breathing, high temperature, excess eye and nasal discharge and coughing.

A number of different infectious agents can be involved in the onset of calf pneumonia. They include:

Viruses (eg bovine respiratory syncytical virus RSV)
Bacteria (eg Pasteurella)
Mycoplasmas

Poor housing and ventilation are among the main causes of pneumonia. High humidity caused by damp bedding, poor air movement or overcrowding can lead to a ten fold increase in the number of infectious organisms and the time they survive. Stress, inadequate colostrum feeding and high levels of atmospheric ammonia are other factors which predispose calves to infection.

Treatment

Once pneumonia is identified it should be treated promptly. Consult you local veterinarian about the best course of action.

Prevention

Steps which should be taken to prevent incidences of pneumonia include:

Ensure adequate colostrum intake
Keep the bedding dry with good drainage and frequent cleaning
Prevent high humidity through effective ventilation (see CALF HOUSING - Pens)

Effective ventilation is essential to prevent pneumonia

Avoid draughts at calf level
Avoid overcrowding (see CALF HOUSING - Ventilation)
House yearlings and young calves separately
Minimise stress

After discussion with your veterinary surgeon consider vaccination where a particular organism has been identified as the cause of the pneumonia

*Welfare of Farm Animal Regulations (Northern Ireland) 2000