Strategies for Feeding Unweaned Dairy Beef Cattle to Improve Their Health

SIMPLE SUMMARY: In intensive fattening cattle, little attention has been focused to discuss if nutritional strategies could help reducing the incidence and severity of the most important health disease in feedlot cattle: the bovine respiratory disease (BRD). Bovine respiratory disease has a great impact on animal productivity with great morbidity and mortality rates during the first months after arrival. Metaphylactic antimicrobial programs are used to prevent and treat it, however, this strategy fails in aspects of the prudent use of antimicrobial treatments promoting the selection for resistance gene determinants and antimicrobial-resistant bacteria. The present review tries to answer the question if there are any nutritional strategies that could help to reduce the incidence and severity of BRD in dairy beef calves. Dairy beef calves are the calves born in dairy farms, around 65%, that are not going to replace the dairy cows and are fattened and slaughtered for meat production. These unweaned and unwanted calves are not a priority for the dairy sector and as a result, their postnatal care has not been a priority for them, and they are considered a by-product. Currently improving their health and welfare is a worldwide concern. ABSTRACT: In order to answer the question of whether nutritional interventions may help to reduce the incidence of respiratory disease in dairy beef calves at arrival, the present review is divided in three sections. In the first section, the nutrition of calves previous to the arrival from the origin farm to the final rearing farm is reviewed. In the second section, the possible consequences of this previous nutrition on gut health and immune status upon arrival to the rearing farm are described. The main consequences of previous nutrition and management that these unweaned calves suffer at arrival are the negative energy balance, the increased intestinal permeability, the oxidative stress, the anemia, and the recovery feed consumption. Finally, in the third section, some considerations to advance in future nutritional strategies are suggested, which are focused on the prevention of the negative consequences of previous nutrition and the recovery of the gut and immune status. Moreover, additional suggestions are formulated that will be also helpful to reduce the incidence of bovine respiratory disease (BRD) that are not directly linked to nutrition like having a control golden standard in the studies or designing risk categories in order to classify calves as suitable or not to be transported.