Metabolism is extremely altered during the transition period. The prepartum period is marked by accentuated fetal growth (Bauman and Bruce Currie, 1980) and the beginning of lactation; however, postpartum is marked by an increase in milk production over time and a deficit in nutrient intake. This situation causes a negative nutritional balance, when the supply of nutrients does not meet the animal's needs; more specifically regarding energy, it is well known that transitioning cows experience a negative energy balance (NEB), and this is easily characterized by a loss in body weight (BW) and body condition score ( BCS). Bertics et al., 1992, and Hayirli et al., 2002, observed that DMI is affected during the prepartum period, showing a decrease of approximately 30% during the last two weeks before parturition. After parturition, DMI increases to primarily meet lactation demands, but it is still not sufficient to meet animal demands (NRC, 2001). DMI is directly linked to milk production and strategies have been developed to maximize intake in order to increase milk production, this shows its importance by the fact that an increase of approximately 1 kg in milk production at peak lactation reflects approximately 200 kg of additional milk. on current lactation. Providing quality feed and maximizing DMI during the transition period is of great importance to minimize NEB and its adverse effects, thereby improving milk production. Metabolic demands increase to support lactation and homeoorhetic adaptations occur to distribute nutrients to the mammary gland. A good example is the metabolism of glucose, an important metabolite used as the main fuel for cells and also transformed into lactose by the mammary gland, which is affected in order to try to respond middle of paper... ...antibodies of whey. Release of stored cells and activation of colony-stimulating factors by bone marrow in response to recombinant bovine somatotropin (bST) increased leukocyte proliferative responses (Burvenich et al., 1999). At the farm level, Eppard et al. (1996) administered bST to cows during parturition and found a decreased incidence of clinical mastitis. Based on these results, it appears that GH is an important factor in strengthening the immune system at this time. The incidence of mastitis is associated with impaired PMN function (Cai et al., 1994), since resolution of the disease depends on the ability of the PMN to recognize the pathogen, to migrate to the site infection, phagocytic capacity and its elimination (Vangroenweghe et al., 2005), and reliability of ROS generation by PMN (Heyneman et al.., 1990).