Get the calf health numbers' game right

19 Sep, 2017 04:00 AM
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The aim of a good calf-rearing program is to produce healthy calves that grow into efficient cows.
One of the indicators of the success of a calf-raising enterprise is the death rate.
The aim of a good calf-rearing program is to produce healthy calves that grow into efficient cows.

Calf health is just a numbers' game. The more things that stress or challenge calves' immune systems, the more likely the calves are to become ill. Unfortunately, there is still a lot of out-of-date information circulating in the industry, recommending practices that do not deliver good outcomes for calf health, growth and later productivity.

Recommendations such as restricting milk intake to force calves to eat concentrates early and the need to feed straw or hay to baby calves do not result in healthy calves that grow into efficient cows. Maybe more importantly, these recommendations result in unhealthy calves that lose weight in the first days of life, that are vulnerable to every passing bug and that have a greatly increased chance of dying. This outcome is of increasing concern to consumers, who are becoming more aware of animal welfare issues in farm animals.

From an economic and environmental perspective, calves that are not fully fed in the first two months of life will never reach their genetic potential for milk production and will have a lifelong reduction in feed conversion efficiency, resulting in higher cost of production and increased greenhouse gas emissions per litre of milk produced. In addition, the early cull rate of cows that were poorly fed as calves is higher than that of calves that were well fed. This significantly increases the heifer-raising component of the cost of production.

One of the indicators of the success of a calf-raising enterprise is the death rate. The commonly accepted definition of death rate is the percentage of calves that die out of the total number of calves the farm intended to rear, from birth to up to a cut off point of 12 weeks of age.

As a measurement of calf-raising success rate, it does not include still births or calves that are born weak and that are not expected to live. High rates of still births or perinatal deaths may be an issue but it is not an issue for which the calf raiser is responsible. If a calf has been tagged/identified and brought into the calf shed and it subsequently dies, it is counted as a dead calf.

An educated estimate would suggest that, on average, for every dead calf there are five calves that are clinically ill. For every five that are clinically ill, there is an even bigger percentage that are stressed from coping with the challenge that has overcome their peers.

Both sick and sub-clinically ill calves are converting feed less efficiently than healthy calves, and this poor feed conversion can go on for several months. Obviously, poor feed conversion increases the cost per kilogram of growth. Death rates of less than 1 per cent are easily achievable but many Australian dairies are running at a much higher percentage than this, which is costing enterprises dearly.

Therefore, the costs of dead calves go far beyond the value of those few dead calves and their treatment. Dairies running at 10, 15 or 20 per cent (or higher) death rates are haemorrhaging money. However, this massive cost associated with dead calves is not obvious and few farms correlate calf health with cow performance later in life, so continue to try to cut the costs of rearing calves without realising the negative impact this is having on the profitability of the farm.

Many farmers do not have accurate figures on death rates and evaluate calf-rearing success from unrealistic "guesstimates" of the number of dead calves in a season. Death rates can seem inconsequential until actual number are counted and percentages calculated. It is important that accurate figures are kept of the number of dead calves as a percentage of the number of calves that are brought in to be reared.

Consider death rates of calves in beef herds in southern Australia. It is rare to lose a beef calf in normal years and those that do die are likely to have suffered from either a congenital defect or snakebite. Rarely do unweaned beef calves suffer from scours or pneumonia unless the cows are severely undernourished and suffering some other stress such as bad weather. The fact is that beef calves that are even mismothered or orphaned often survive on stolen milk (although they may fail to thrive). They survive because, apart from the lack of nutrients, there are few other challenges in their world. They are not dealing with the stresses of overcrowding, contaminated milk or a dirty environment, to which many dairy calves are subjected. The greater the number of challenges calves have to overcome, the harder it is for calves to stay healthy.

How can a dairy achieve a death rate of less than 1 per cent? Every journey starts with a single step, so every little management change will bring a benefit.

Milk feeding at a level which is closer to what a calf will drink naturally is one way to reduce the level of challenge for calves. Even young calves left to suckle ad lib will consume between 18 and 23 per cent of their birth weight. This means a 40-kilogram calf will be drinking between 7 and 9 litres per day. This figure quickly ramps up to more than 15 litres by about 10 days of age.

Clearly, the recommended 4-5 litres a day is not delivering the level of nutrients calves naturally want to consume; it is certainly not delivering enough nutrients to enable calves to overcome multiple challenges to their survival.

Calves, like all other animals, prioritise the partitioning of nutrients, depending on the circumstances. Maintenance of normal bodily functions gets first cut of nutrients, then supporting the immune system to try to prevent illness, then finally, any nutrients left over will be used for growth. When feeding levels are low and immune challenge and/or stress levels are high, growth will be minimal.

Calves are born with little fat and this is burned up in the first couple of days of life, leaving an underfed calf with no alternative but to start breaking down muscle tissue. It is common to see young calves that have lost muscle mass in the first two weeks of life.

Calves should put on weight steadily from birth. Calves that lose weight within the first two weeks of life are an indicator that either calves are not getting enough nutrients, that there are too many immune challenges in the calves' environment or, more likely, a combination of the two.

One thing to make clear is that milk does not cause calves to scour ù what does make calves scour is contaminated milk. If feeding more milk results in scouring calves, there is a build up of pathogens (bugs) in the milk supply. This may come from poor sanitation practices, it may come from poor milk-handling practices or it may come from contamination from faeces. If effective milk hygiene practices are followed, it should be possible to increase milk feeding levels without calves developing scours.

Other challenges to calf health are overcrowding, dirty bedding, high ammonia levels, drafts and endemic diseases such as cryptosporidiosis and coccidiosis. Coccidiosis is particularly easy to control these days, so it makes economic sense to remove that challenge. Provided calves are consuming sufficient nutrients, it is remarkable what challenges they can overcome.

Improving calf management ticks all the boxes by leading to:

  • Improved animal welfare.
  • Reduced calf-rearing costs.
  • Reduced calf mortality and morbidity rates.
  • Increased lifetime feed conversion efficiency.
  • Reduced greenhouse gas emissions per litre of milk produced.
  • Increased retention rate of cows in the dairy.
  • The hardest part of changing calf management practices is psychological. To accept that change is necessary and to work out the best ways of implementing the improved practices is challenging; otherwise, there are no negatives to improved calf management.D

    *Jeanette Fisher runs an independent dairy heifer advisory service, Heifermax and can be contacted through her website www.heifermax.com.au.

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