Dynamic of metabolic indicators, insulin like-growth factor I (IGF-I) and cortisol in holstein cows during the transition period

Background : Physiological events occur in the transition period marked by negative energetic balance, where the energetic demand is higher due to fetal nutrition and lactogenesis and intensified by the decrease of the dry matter intake in the pre-partum period. The adaptation of cows is dependent of homeostatic and homeorhetic mechanisms regulated by catecholamine, cortisol, GH, IGF-I, insulin and glucagon but the priorization of homeorhetic mechanisms could result in metabolic diseases. Considering the scarce longitudinal studies about the Brazilian conditions the aim of this project was to evaluate the influence of transition period on metabolic indicators, cortisol and IGF-I in Holstein cows. Materials, Methods & Results : Thirteen cows, from 2nd to 4th lactation were evaluated weakly from week -2 to week +3 in relation to calving to determine the body condition score (BCS), metabolic and endocrine profile. The BCS decreased between week -2 (BCS = 4.0) and +1 (BCS = 3.0), followed by and slight increase on weeks +2 and +3 ( P = 0.000). The most of metabolic indicators and hormones have changed during the transition period ( P ≤ 0.05), especially around calving. It was possible to detect the peak of cortisol, glucose, non-esterified fatty acids (NEFA), s-hydroxibutyrate (BHB), and aspartate aminotransferase (AST) on delivery and week +1. On the other hand, total calcium, triglycerides (TG) and cholesterol (CHOL) decreased was observed around parturition. Insulin like growth factor type I (IGF-I) showed marked reduction between pre and postpartum, and the lowest value was observed in the week +1. TP and GLOB had the lowest value on calving and globulin has a gradual increase from delivery to week +3. Discussion : Cows included in this experiment had dystocia (4/13, 30.8%), retention of placenta (1/13, 7.7%) and clinical hypocalcemia (1/13, 7.7%). One of the animals with episodes of dystocia was also aggravated by ketosis in week +1 and +2 (1/13, 7.7%). Uterine infections were observed in five animals (5/13, 38.4%). Of this total of animals with uterine infection (5/13), three had already expressed earlier disturbances: two cows had dystocia and one cow with retention of placenta. The weight loss observed between pre and postpartum may be due to an increase of energy demand for fetal maintenance and the concomitant initiation of lactation, in conjunction with an approximately 30% reduction in dry matter intake during the transitional period. The hyperglycemia concomitant with the peak of cortisol at delivery may be explaining by the activation of the somatotropic axis, due to the stress of calving. The increase of NEFA, BHB and AST around calving associated with decreased of TG and CHOL could be associated with homeorhetic mechanisms, especially lipolysis and gluconeogenesis. The IGF-I decrease in postpartum may be by the decreased expression of receptors for growth hormone (GH) in the liver, and consequently reduced synthesis and/or IGF-I hepatic clearance, which reduce of the negative feedback of IGF-I on GH secretion. The total calcium concentrations were below the threshold (8.50 mg/dL) established by Goff [10] at parturition, week +1 and +2 and probably is due to the secretion of 20-30 g of calcium per day during the colostrum synthesis. Total protein and albumin have a slight variation, except for the peak observed on week +3 due to uterine infection. Keywords: body condition score, non-esterified fatty acids, s-hydroxibutyrate, total calcium, hormones.