Raising healthy heifers is a key component to making sure that future herds are high-production. Poor growth in young calves strongly impacts subsequent milk production. As such, even during a busy calving period, calves should not be forgotten. There are four crucial areas to look at when rearing healthy heifers:
- Early nutrition
- Rumen development
Colostrum is the first source of nutrients, vitamins and antibodies (immunoglobulins) the calf will ingest. The colostrum immunoglobulins protect the calf against pathogens and disease during the critical time when the young ruminant’s own immune system is evolving. The ability to absorb colostrum is at its highest in the first hour after birth, after which, it begins to decline and continues to do so through the calf’s first 24 hours.
A rule of thumb is to feed 10 percent of body weight (i.e., 3-4 litres) of good-quality colostrum within the first two hours, as a delay in the first feeding will reduce the absorption rate — and a failure to absorb enough immunoglobulins from colostrum leaves a calf susceptible to disease. A second feed should be given eight hours later, before transitioning to milk or calf milk replacer.
Early nutrition is important for the pre-ruminant calf to successfully transform into a ruminating, high-producing cow, as well as for providing the calf with the energy and nutrients its immune system needs in order to develop.
The golden rule is to double birth weight before weaning (at 8-10 weeks), and this is best done during the few months when feed efficiency is at its greatest. Therefore, a 40-kilogram calf should gain 0.6 kilograms per day. To achieve this, aim to feed 15 percent of body weight (i.e., 6 litres for a 40-kilogram animal). Keep in mind that, at this stage, the calf abomasum is not large enough to deal with 6 litres of milk at once.
Calves require around 325 grams of milk solids for maintenance. Milk powder contains 12.5 percent DM, which translates to 2.6 litres. Calves weighing 40 kilograms being fed four litres per day (i.e., 10 percent of their body weight) can achieve 200 grams of growth per day. However, calves weighing more than 40 kilograms will struggle to maintain on this level. Milk replacer has a lower fat and energy content than whole milk, and as such, a higher rate is necessary.
When mixing milk powder, always remember that 125 grams of milk powder makes up to one litre — not 125 grams added to one litre of water. Milk replacer should match growth targets.
The rumen needs to be fully functioning to successfully perform later in life. The development of the rumen is aided by the starch content in concentrate feeds, which should be made available within 2–3 weeks of birth.
To strengthen the rumen wall, calves should have access to straw. However, avoid feeding a diet with a high hay content; there is a greater risk of overeating hay, which can lead to pot belly — that is, filling the rumen with hay that cannot be properly digested. This can lower concentrate intake.
After birth, a calf should be dried off as quickly as possible and placed in a clean, dry, draught-free environment. Alternative bedding, such as wood chip and peat, is adequate but may need to be topped up regularly to ensure it stays consistently dry.
Cleaning all feeding equipment is necessary for maintaining healthy animals, and prioritizing younger animals first, along with rinsing before feeding the other batches, will help mitigate the spread of disease. Clean, fresh water should always be available, as consumed milk goes into the abomasum, leaving no liquid in the rumen to digest the concentrates.
Changes within groups should be kept to a minimum, and calves of similar sizes or ages should be kept together.
Along with good management practices, you can build a healthy herd with a strong rumen and robust immunity by focusing on:
- Colostrum — quality and quantity are both important, and there is only one chance to get it right.
- Early nutrition — monitor body condition and weight gain during this period to ensure that feed is meeting the calves’ needs.
- Rumen development — use starch and fiber to grow a healthy rumen.
- Environment — keep their living quarters clean, dry and stress-free.