Calf Rearing

The rearing period is one of the most important in the life of ruminants, as the subsequent productivity of the animal is determined during this stage. Mistakes in the management of this period follow the animal throughout its productive life.

Colostrum

Ruminants, when they are born, do not have any antibodies. That is why it is very important for the newborn calf to receive, within the first hours of its life, an adequate amount of high-quality colostrum, through which the mother’s antibodies will pass to the young animal and immunize it against several diseases. In addition, colostrum is an important source of energy for the calf during its first hours of life, helping it maintain its body temperature. Immediately after calving, the quality of the dams’ colostrum must be checked for its density in essential immunoglobulins using a colostrometer or a BRIX refractometer. Suitable colostrum is that which contains at least 50 g/l of proteins, which corresponds to 22% on the BRIX scale. The digestive tract of the newborn has an increased ability to absorb the immunoglobulins provided by the colostrum immediately after birth, which decreases over time. Therefore, it is important for the calf to consume an adequate amount of colostrum within the first 12 hours of its life, with the first feeding given 1–2 hours after birth. In case of low-quality colostrum, it is recommended to administer colostrum replacer or colostrum from the farm’s reserve.

Rearing

During the rearing period, young animals are fed with milk in order to grow and for their digestive system to mature so that they can gradually transition to consuming exclusively solid feed. Calf rearing may last 8–10 weeks, and the goal is for their body weight to have at least doubled at weaning. Animals that “fall behind” during the rearing period and fail to reach the desired targets at weaning tend to have lower fertilization rates with a longer time to first A.I., lower milk production, inability to compete with the rest of the herd, and incomplete development of the mammary glands.

Rearing with the use of milk replacer presents notable advantages:

A) Cost control of rearing

B) Disease prevention
Milk replacers are sterile, free from anything that could harm the animal’s health, ensuring the smoothest possible development of the calves without the risk of infection by a pathogen.

C) Better growth
Milk replacers have stable composition and characteristics. Thus, the animals receive all the nutrients they need through rearing, ensuring that at weaning the animal is in the proper physical condition and developmental stage.

The selection of an appropriate milk replacer should be based on its protein and fat content (>20%) and the absence of crude fiber. The preparation instructions recommended by the manufacturer of each milk replacer must be followed, and the indicated dosages and temperatures must be observed so that the milk has the proper composition. Attention must be paid to the temperature at which the milk is offered to the animals, which should not be lower than 37°C.

Solid Feed

The introduction of solid feed should begin in the first week of the calves’ life. This helps in the gradual development and formation of the stomach and overall digestive system of the animal so that it can later support exclusive feeding with solid feed. For this period, a complementary feed specially designed for the nutritional requirements of this specific stage must be chosen. Fresh, clean water must also be provided continuously to all animals, otherwise feed intake decreases.

Weaning

For weaning to be successful, the development of the animal’s digestive system must be complete, and the animal must be able to feed exclusively on solid feed. Calves are weaned when they consume 1–1.5 kg of concentrate feed for at least 3 consecutive days and gain 0.8–1 kg of body weight per day. Calves under rearing are a sensitive group of animals, and the required attention must be given to their management. The products used for their feeding must be carefully selected and of excellent quality so that the optimal growth rate and weaning targets can be achieved.