Interacciones entre el metabolismo y la reproducción en la vaca lechera: es la actividad gluconeogénica el eslabón perdido?

ABSTRACT: The specialized systems of milk production in Antioquia, Colombia exhibit a high incidence of metabolic, nutritional and reproductive disorders, whereas the nutritional ones are characterized by energy and fiber deficits and by excesses of crude protein. This review proposes a model of sequence of events supported on experimental evidences which can explain in a good manner the nature of the nutritional, metabolic and reproductive interactions in the cows in early lactation. The intestinal absorption of glucose is very low in ruminants because of its disponibility is conditioned by ruminal fermentation. Given the mammary gland is able to use glucose under low insulin concentrations and that the demands of glucose for milk production are very high, the effect on the glicemia must be stabilized through an increase in the gluconeogenesis and decrease in the glucose oxidation rates. The capacity of metabolic response to the glicemia reduction could be diminished by exaggerated lipid mobilization and by excess in crude protein. In cows with hepatic lipidosis it was found that the activity of key enzymes for gluconeogenesis was lower than in healthy cows. It is also know that the urea cycle is submitted to saturation, and it is therefore expected that the high ammonia concentrations, present in the hapatocyte will alter its chemical conditions, affecting the normal gluconeogenesis. Recent work demonstrated in vitro that the addition of NH4Cl to ovine hepatocytes decreased gluconeogenesis rate. So the infertility problems could origin from the reduced gluconeogenic capacity. Reported results show low glicemia values and this suggest that the mechanism which permit the maintenance of the normal glicemia are failing. The main factor regulating insulinogenesis in ruminants is glicemia. Both glucose and the carbonated skeletons of amino acids or insulin or Insulin-Like Growth Factor (IGF- 1), can modulate the ovulation rate, independent of the plasmatic concentrations of Follicular Stimulant Hormone (FSH), through direct effect on follicular development on the ovary. It is proposed then that during early lactation the hormonal factors that favours low concentrations of insulin and IGF-1 are potentialized; this factors and the coexistence of adverse ones, like the accelerated lipid mobilization and the excess of ammonia, significatively reduce the gluconeogenesis rate and thus glicemia, bringing at last to a marked reduction on the plasmatic concentrations of insulin and IGF-1, which are both factors of ovarian growth. This would explain the fertility decrease observed in milk cows in early lactation.

• Autores: Galvis Góez, Rubén Darío; Correa Cardona, Héctor J.
• Tipo de recurso: Review article
• Fecha de publicación: 2002
• Institución: Universidad de Antioquia
• Repositorio: Repositorio UdeA
• Idioma: spa
• OAI Identifier: oai:bibliotecadigital.udea.edu.co:10495/7254
• Acceso en línea: http://hdl.handle.net/10495/7254
• Palabra clave: Fecundidad del ganado; Ganado de leche; Metabolismo; Reproducción animal; Nutrición animal
• Rights: openAccess
• License: Atribución-NoComercial-CompartirIgual 2.5 Colombia (CC BY-NC-SA 2.5 CO)