The arrival of calves at the feedlot is a very important stage in the feeding process, as it will influence the final results.

Colostrum antibodies provide passive immunity to the animal and protection during the first days of life. Calves should develop active immunity as soon as possible after birth, to protect the organism from external agents.

The development of immunity against the main respiratory and intestinal pathogens in calves is a priority to achieve good health and profitability of the feedlot.

The arrival at the feedlot is the most critical stage in the feeding process. It is a stage with abrupt changes: transportation, changes of location, new groups, intensification, separation from the mother in the case grazing calves, changes of diet, among others. These changes generate stressful situations that cause immune suppression, a decrease in the immune response due to the reduction of the production of cytokines (molecules responsible for the activation of the defending cells in the body and the immune system).

Additionally, in many feedlots, animals come from different origins, which makes the arrival of animals a critical stage in the farm’s health program, because the immune system should face vaccinations and antiparasitic treatments. It is recommended to start antiparasitic treatments in the mothers. In the case of grazing calves, try rotational grazing, and, in suckler calves, eliminate parasites when they start with the milk replacer.

The digestive system with keratinized papillae is not yet completely developed, so it is necessary to focus on the establishment a balanced ruminal flora and the correct development of the papillae by starting with low concentrations of fat and starch and a high content of fibre, and gradually increase fat, starch and CFU and reduce fibre, so that animals efficiently convert energy and proteins.

Because of these factors, most cases of diseases and casualties occur during the first month in the feedlot. For this, many health programs include long antibiotic therapies at the animal’s arrival, to help animals while they develop immunity after vaccination and prevent the negative consequences of immune suppression.

Pronutrients are complex organic molecules of a plant origin that stimulate and regulate animal physiology without causing pharmacological effects, resistance, residues or withdrawal periods. The addition of immune-boosting pronutrients in this stage stimulates and strengthens the specific and non-specific immune system of the calf. In addition, they strengthen the immune response to vaccination and increase its effectiveness, which has a positive impact on animal health and, thus, on productive and economic performance.