J. Chávez, Guadalupe Bernal, A. Rodríguez, K. Mark, E. Díaz, A. Aguilera, T. Reis de Souza, C. Betancourt, M. Cárdenas


Two in vivo metabolic challenges were conducted to assess the changes in glucose metabolism during three intervals prepartum (-6, -4, -2 weeks) and three postpartum (+2, +4, +6 weeks) in six multiparous pregnant Nubian goats. Challenges consisted of intravenous administration of 1) glucose (62.5 g/goat) and 2) L-epinephrine (0.7 mg/kg body weight). Blood samples were collected via jugular cannula from 30 min pre-injection (basal concentrations) to four hours post-injection. Response variables for glucose challenge were glucose concentration at zero time (to) glucose disappearance rate (t½), insulin and NEFA concentrations; for the epinephrine challenge glucose, NEFA and insulin integrated responses were determined through the four hours of sampling. Data were analyzed according to a repeated-measures design. Dry matter intakes (1.8±0.07 kg/d) were not different throughout the study (P>0.1). Average milk production (649±69 g/d) was not different among periods (P>0.1). Basal glucose and insulin concentrations were not different (P>0.1) between pregnancy and lactation, with means (± standard error) of 77.9±3.7mg/dl, and 0.264±.034ng/dl, respectively. Basal NEFA concentrations were greater (P<0.001) during weeks 2 and 4 postpartum (0.40±0.2 and 0.57±0.3 mmol/l) and lowest during prepartum periods. Responses to glucose challenge did not differ throughout periods evaluated, with means for to of 289±17 mg/dl (P>0.1) and for t½ of 31±15 min (P>0.1). Insulin responses were similar for all periods (63.3±8.2 ngml-1min) (P>0.1). The epinephrine challenge resulted in similar changes in glucose and insulin integrated responses throughout the periods evaluated (P>0.1), with corresponding means for glucose of 3886.5±318 mgml-1min, and 21.6±7.7 ngml-1min, but elicited a significant (P<0.001) increase in plasma NEFA concentrations during weeks 2 and 4 postpartum (1.24±0.6 and 1.40±0.3 nmol.l-1min), but not during the prepartum periods. Metabolic responses of dairy goats to exogenous glucose and epinephrine markedly influenced by physiological stage, mainly with onset of lactation.  


Energy metabolism, dairy goat, metabolic challenge, glucose, insulin, NEFA.


Copyright (c)