Getting the most out of spring calf rearing

1. The presence of a disease-causing organism.
2. The presence of a favourable environment to disease.
3. The requirement of a susceptible host.

Not everyone’s calf rearing facilities or systems will allow for the control of the above – but the more you can control, the lower the likelihood of disease development. With this in mind, my take on calf rearing, controlling disease and maximising calf growth are guided by the following principles:

1. Minimise disease by:
   • Minimising calf exposure to disease causing pathogens.
   • Maximising calf immunity.
   • Minimising the effects of stressors.
   • Minimising calf sickness and death rates.
2. Maximise growth by:
   • Maximising feed conversion efficiency.
   • Minimising growth checks.

Let’s also talk about minimising calf exposure to disease causing pathogens. Some points to consider regarding pathogens are:

• Pathogens are required to cause an infectious disease.
• Calves can be exposed to a pathogen from a contaminated environment or object (feeders, pens, other animals, people, feed, liquid, air etc.) or from another calf or cow.
• Some pathogens survive for long periods in the environment and can be a source of infection from one season to the next.
• Pathogens can be shed from healthy looking animals as well as sick looking animals.

Minimising a calf’s exposure to a pathogen is mainly about hygiene and biosecurity – i.e., breaking the pathways that a pathogen can take to get into a calf.

A couple of key actions that can be taken within the next two months are emptying your calf rearing sheds of old bedding, hot water/steam blasting your sheds (in every nook and cranny), disinfecting the shed with a broad spectrum product (one that can combat cryptosporidium), replacing calf feeder teats and carrying out maintenance on equipment and water lines.

Maximising growth in the calf

One of the ways to maximise growth in the calf is to take advantage of a young calf’s ability to convert feed into weight. A calf less than two weeks old should be able to convert more than 50% of the nutrients going in (dry matter weight) to bone and muscle growth. This rate steadily declines as the animal ages – down to about 10% at 11 months old. From a feed efficiency point of view, it pays to maximise this early growth potential.

The provisos to maximising this high feed conversion efficiency of the young calf are:

1. Each new-born calf needs 10 to 15% of its body weight in hygienically collected, fresh, good quality, first milked colostrum within 24 hours of birth (good colostrum management not only helps with a calf’s ability to fight disease but it also helps enable the gut to mature and to absorb nutrients).
2. The calf needs to be healthy.
3. The calf needs to be well fed (quantity AND quality of feed – a little bit more on this following).

Do not underfeed your calves (in dry matter content). Underfeeding will only prolong the time till weaning plus less nutrients and energy are available for immune function, so the risk of disease outbreaks is increased. As a guide try not to feed milk at a dry matter concentration higher than 20% unless following mixing instructions of a particular product. Feed the equivalent of 750 to 800 grams or 1000 grams of milk solids per day to Jersey/Wagyu calves and Holstein Friesian calves respectively. Feed a maximum of two to four litres per feed to calves less than four weeks old. To feed five to eight litres per day feed over two feed events. Whole milk may need to be fortified with a calf milk replacer. A product like Blossom Hi Spec calf milk replacer is perfect for this. Maximise this milk input for at least the first three weeks (which is when calves can start properly digesting meal).

If the dry matter weight of the milk solids fed to a calf is constant (volume may differ) there is little variation in growth rates achieved from feeding calves good quality whole milk, good quality skim/casein or good quality whey calf milk replacer. What may differ between the milk types is the incidence of disease (more on this next month but a calf milk replacer like Blossom Hi Spec has added immune related components that helps with supporting immune function plus is pasteurised to kill bacteria).

Maximising calf immunity 

The biggest drivers of immune function in the young calf centres around: colostrum (quality, quantity and the timing of feeding); trace element status; nutrition; stress and vaccinations to name a few.

Colostrum was touched on last month and you would have heard it all before, but it is worth repeating. Each new-born calf needs 10 – 15% of its body weight in hygienically collected fresh good quality first milked colostrum within 24 hours of birth. Colostrum quality (that is the IgG concentration of antibodies/immunoglobulins within the colostrum) can be influenced by the management of the cow prior to calving. Vaccinating cows (or heifers) prior to calving with vaccines like Rotavecâ Corona vaccine, ScourGuardâ 4(K) and Salvexinâ B increases IgG levels and produces antibodies that are specific to a number of common disease causing pathogens like Salmonella, Rotavirus, coronavirus and E.coli. Colostrum quality generally cannot be judged on appearance alone. A Brix Refractometer is a device that can be used to objectively measure the IgG concentration of colostrum. The best quality colostrum can then be fed to new-born calves and the lesser colostrum fed to older calves.

Trace elements play a part too. Cows or heifers transfer selenium and copper (and more) to the calf via the placenta to the foetus and via the milk to the newborn (know the status of these minerals in your animals prior to calving). These minerals are important for calf viability and immunity (they also are important for immune function, colostrum and milk production, and reproduction in the dam, but this is outside the scope of this article). Cows low in selenium prior to calving produce less colostrum with lower IgG levels. New-born calves with inadequate copper and selenium stores are more at risk to disease. Injecting a young calf with Multiminâ (copper, selenium, zinc, manganese) as they are born, or as a 4-day old for those who buy calves to rear, will boost immune function in a calf improving calf survivability and reducing disease incidence. The same applies once the calf is weaned off milk.

For those that rely on feeding a milk powder, a good quality milk replacer will provide trace elements to the calf as well. A product like Blossom Hi Spec will also have other added immune improvement components that assist with immune function.

Nutrition is another important factor in improving calf immunity. But, generally a well and fully fed calf will have more energy to divert to immune function and disease control.