Pre-and post-feeding plasma gastrin-17 and insulin concentrations and feed intake in female goats during different physiological stages

Gastrin (GAS) and insulin (INS) play a significant role in the regulation of feed intake, as well as in the homeorhetic adaptations to different physiological stages, nutrient supply and requirements. The aim of the study was to verify if plasma GAS and INS concentrations in adult does are affected by the physiological state, change in response to the meal and are correlated with feed intake and energy balance. Dry matter intake (DMI) and pre and post-prandial plasma concentrations of gastrin-17 and insulin were recorded in 21 female goats fed hay and different quantities of concentrate (maize grain) twice daily in different physiological states. DMI was lower during the week of oestrous activity, compared to the period of anoestrus - progressively decreasing during pregnancy and increasing during the post-partum period, without significant differences between early and late lactation. Plasma GAS concentrations were significantly affected by physiological status, being higher (P < 0.05) during lactation than during pregnancy. Overall plasma GAS concentrations increased (P < 0.01) from pre-feeding levels (169 +/- 24 pg/ml), to 30 min after feed ingestion (185 +/- 29 pg/ml). The increase occurred 10 and 20 min (P < 0.05) after feeding, regardless of the diet composition. Both pre- and post-prandial GAS concentrations were related to DMI (P < 0.001), but not to the energy intake. Plasma INS on the other hand was not significantly affected by the physiological status. The pre-feeding plasma INS concentration, across all physiological states, was 1.36 +/- 0.32 ng/ml and increased (P < 0.01) to 1.45 +/- 0.38 ng/ml 30 min after feeding. Pre-feeding INS, but not post-prandial INS, increased with increasing proportions of maize in the diet and energy intake (P < 0.05). Overall INS was negatively correlated (P < 0.05) to DMI. It was concluded that cephalic reflexes are efficient stimula for both GAS and INS release in adult goats fed twice daily. Plasma GAS concentrations were related to hay intake and total DMI, thus with the volume of ingesta and presumably the time spent eating. GAS concentrations were not affected by the type of feed, nor the energy intake or the flux into the abomasum. Pre-feeding plasma INS was mainly dependent on the energy intake, while the post prandial increase was not dependent on the size or quality of the meal, or on the energy intake. Dietary manipulation and feed ingestion can thus affect the circulatory levels of these two main endocrine factors.