Hormonal status and regulation of glycemia in neonatal calves during the first hours of postnatal life

Abstract

The aim of this study was to examine changes in some hormones concentrations in calves during the first 32 hours of neonatal life and to estimate their association with glycemia. Thyrty two Holstein breed calves were selected for the study. Blood samples were taken at 30, 60 and 90 minutes postnatal. Calves received pooled colostrum: primary colostum (1.5 L, 2 hours after birth), secondary colostrum (2 L, 14 hours after birth) and tertiary colostrum (2 L, 26 hours after birth). Blood samples were taken at hours 5, 20 and 32 of neonatal life. Concentrations of glucose, insulin, cortisol, thyroid hormones and IGF-I and abundance of IGFBP-1, IGFBP-2 and IGFBP-3 were determined in the blood serum. The T3/T4 ratio was also calculated. Calves were born hypoglycemic (glycemia was 2.56±1.05 mmol/L at birth). Thereafter, glycemia significantly increased (p<0.001) to 3.05±0.89 mmol/L at min 90. Glucose concentration showed a further increase after colostrum intake and was significantly higher than at the initial value in all examined periods (p<0.001). During the first 90 minutes of neonatal life insulinemia decreased significantly (p<0.001) compared to initial value (26.33±10.05 μIU/L) and it measured 18.66±5.56 μIU/L at min 90. Cortisolemia was highest at minute 30 (85.08±19.36 nmol/L) and than decreased until the end of the experiment (p<0.001) compared to initial values in samples obtained during the period of colostrum intake. A significantly high correlation was determined between glycemia and cortisolemia in all examined periods before the first colostrums intake (r2=0.854; p<0.01 at min 30; r2=0.742; p<0.01 at min 60 and r2=0.551; p<0.01 at min 90). T4 concentrations significantly increased during the first 2 hours, while T3 concentrations decreased, significantly from min 30 to min 90 postnatal (p<0.05). T3/T4 ratio significantly increased during the first 2 hours of neonatal life. After first colostrum intake, concentrations of both hormones rose significantly compared to the initial level, but T3/T4 ratio did not change and maintained the value determined at minute 90. IGF- 1 concentrations significantly decreased during the first 2 postnatal hours. A significant positive correlation was observed between IGF-1 concentration and insulinemia (r2=0.463; p<0.05 at min 30, r2=0.662; p<0.01 at min 60 and r2=0.583; p<0.01 at min 90). IGFBP-3 abundance significantly decreased, while IGFBP-1 significantly increased in this period. IGFBP-2 abundance was highest at birth. Results presented in this study indicate that the increase in glucose concentration during the first 2 hours of neonatal life, before the first colostrum intake is mainly the result of increased activity of the adrenal cortex in cortisol secretion and extrathyroidal tissue thus providing sufficient triiodothyronine. Immaturity of mechanisms responsible for insulin secretion provides the dominance of catabolic processes. Changes of the IGF system provide a rise of glucose concentration...

Endocrine And Metabolic Adaptations Of Calves To Extra-Uterine Life

“…This IGFBP status is opposite than in most other animals and humans [70,71]. Thereafter, during the fi rst 90 minutes of neonatal life, when calves are exposed to starvation, IGFBP-3 and IGFBP-2 concentrations signifi cantly decrease and IGFBP-1 concentration signifi cantly increases [68]. Decreased IGFBP-3/IGFBP-1 ratio enables IGF-I to pass though the capillary walls into the extracellular space where it may complement effects of insulin on glucose metabolism [72].…”

“…In the condition of negative energy balance, that occurs immediately after birth, the concentration of IGF-I depends on the concentration of insulin in the circulation [66,67]. There is a signifi cant positive correlation between IGF-I and insulin concentrations during the fi rst 2 hours of calf`s postnatal life, meaning that insulinemia, rather than GH, at birth affects IGF-I concentration [68]. In the condition of additional energy supply by glucose infusion, IGF-I concentration is strongly positively infl uenced by glucose concentration [43].…”

“…Kirovski and coworkers [68] showed that immediately after birth in neonatal calves the concentration of IGFBP-3 is highest and concentrations of IGFBP-2 and IGFBP-1 are lowest. This IGFBP status is opposite than in most other animals and humans [70,71].…”

“…In a study presented by Kirovski and coworkers [43] hyperglycemia induced by glucose application immediately after birth provoked an increase of IGFBP-3, with no effect on IGFBP-1 and IGFBP-2 concentrations, leading to a retention of IGF-I in the circulation. Some authors observed a higher abundance of IGFBP-2 in neonatal calves immediately after birth [43,68,76] and explained it by a stress reaction that is characterized by an increased concentration of IGFBP-2 [77].…”

“…At birth the placental supply of carbohydrates from the mother stops abruptly and neonatal calves show hypoglycemia immediately after birth [68]. Because of that, during the fi rst several hours of life, meaning until fi rst colostrum intake, the newborn has to derive carbohydrates from its own endogenous sources through activation of gluconeogenesis and glycogenolysis.…”