Influencia de las alteraciones metabólicas sobre la actividad PEPCK, la generación de IGF-1 plasmático y la reactivación ovárica en vacas en la lactancia temprana

Abstract

ABSTRACT: In order to assess the influence of the energetic and protein metabolism alterations on the activity of the enzyme phosphoenolpyruvate carboxykynase (PEPCK), the generation of insulin, the insulin like growth factor-1 (IGF-1) and ovarian reactivation, ten Holstein cows were used obtain samples on the 12th prepartum and on the 12th, 24th, 35th and 100th postpartum days (lactation days, DEL) to determinate the balances of lactation net energy (ENL), the concentrations of plasmatic urea (BUN), glucose, total cholesterol, ammonia, ß-OH butyrate, non-esterified fatty acids (AGNE), insulin, IGF- 1, and the transaminase oxaloacetate glutamate activity (AST). In addition to the before mentioned tests, the concentration of plasmatic progesterone (p4) was determined on the 12th, 16th, 20th, 24th, 28th, 32nd, 36th and 40th postpartum days. On the 12th prepartum and on the 12th and 24th postpartum days, liver biopsies were obtained to estimate the PEPCK level of activity. As a result, the glycemia and IGF-1 postpartum values were significantly lower. The average values of ß-OH butyrate, BUN, ammonia, and plasmatic insulin did not show any significant variations between the two periods. Similarly, the AST values were significantly lower prepartum than postpartum. The lowest AGNE values arose, respectively, from the prepartum sample and the sample obtained on the 100th postpartum day. The PEPCK activity was significantly higher prepartum than postpartum. On the one hand, positive relations between PEPCK and BUN, as well as between ENL and p4 were found. On the other hand, negative relations were arrived at between PEPCK and ß-OH butyrate as well as between AGNE and p4. The relation between PEPCK and IGF-1, and the relations between AGNE and p4 could have occurred as an indirect effect of glycemia and ENL. Only the cows with an ENL higher than -10% of the requirements showed ovarian reactivation.

RESUMEN: Con el fin de evaluar la influencia de las alteraciones en el metabolismo energético y proteico sobre la actividad de la enzima fosfoenolpiruvato carboxikinasa (PEPCK), la generación de insulina, del factor 1 insulinoide de crecimiento (IGF-1) y sobre la reactivación ovárica, se utilizaron 10 vacas Holstein, las cuales se muestrearon el día 12 preparto y los días 12, 24, 35 y 100 posparto (días en lactancia, DEL) con el fin de determinar el balance de energía neta de lactancia (ENL), las concentraciones plasmáticas de urea (BUN), glucosa, colesterol total, amonio, b-OH butirato, ácidos grasos no esterificados (AGNE), insulina, IGF-1 y la actividad glutamato oxaloacetato transaminasa (AST). Adicionalmente los días 12, 16, 20, 24, 28, 32, 36 y 40 posparto se determinó la concentración de progesterona plasmática (p4). El día 12 preparto, 12 y 24 posparto se tomaron biopsias de hígado con el objetivo de estimar la actividad (PEPCK). Los valores de glicemia e IGF-1 fueron significativamente más bajos en el posparto. Los valores promedio de b-OH butirato, BUN, amonio e insulina plasmáticos no presentaron variaciones significativas entre periodos. Los valores de AST fueron significativamente más bajos en el preparto que en el posparto. Los valores más bajos de AGNE correspondieron en su orden al muestreo corres-pondiente al día 100 posparto y al muestreo preparto. La actividad PEPCK fue significativamente más alta en el preparto que en el posparto. Se encontraron relaciones positivas entre PEPCK y BUN, y entre ENL y p4. Se encontraron relaciones negativas entre PEPCK y ß-OH butirato y entre AGNE y p4. La relación entre PEPCK e IGF-1 y entre AGNE y p4 pudo ser debida a un efecto indirecto de la glicemia y de ENL. Solo las vacas con ENL superior a -10% de los requerimientos presentaron reactivación ovárica.