Effect of vasoactive intestinal polypeptide infusion on feed intake, digesta flow and nutrient digestion in sheep with access to feed for limited time

Abstract

. 2000. Effect of vasoactive intestinal polypeptide infusion on feed intake, digesta flow and nutrient digestion in sheep with access to feed for limited time. Can. J. Anim. Sci. 80: [105][106][107][108][109][110][111][112]. Two experiments were conducted to test the hypothesis that vasoactive intestinal polypeptide (VIP) infusion into the gastric artery increases feed intake, duodenal flow and amino acid supply to the small intestine of sheep. Four sheep in exp. 1 and five sheep in exp. 2 were fistulated with rumen and duodenal cannulae. Sheep in exp. 2 also had an ileal cannula. In both experiments animals were fed a diet of alfalfa pellets ad libitum for 8 h per day in a thermoneutral environment (20 ± 2°C) and had free access to water and mineralized salt blocks. In exp. 1, VIP was infused at 1 nmol min -1 through a gastric-artery catheter for 10 min duration each hour for 3 h each day for 4 consecutive days. In exp. 2, VIP was infused at 1.5 nmol min -1 for 10 min duration each half-hour for 3 h each day for 7 consecutive days. Control sheep were infused with saline. Vasoactive intestinal polypeptide infusion increased (P < 0.05) feed intake by 14.3 and 26.1% in exp. 1 and exp. 2, respectively. In exp. 2, there was a positive regression (P < 0.01) between intake and duodenal passage of dry matter (DM) (n = 5, r 2 = 0.67), organic matter (OM) (n = 5, r 2 = 0.68), and amino acids (AA) (n = 5, r 2 = 0.85). The present results suggest that VIP may play a role as a physiological regulator of feed intake in sheep and also has potential to increase the supply of nutrients to the animal. Can. J. Anim. Sci. 80: 105-112. Deux expériences ont servi à vérifier l'hypothèse voulant que l'infusion de polypeptide intestinal vasoactif (PIV) dans l'artère gastrique produisse une augmentation de l'ingéré alimentaire, du taux transit duodénal et de l'apport d'acides aminés à l'intestin grêle du mouton. Quatre moutons dans la première expérience et cinq dans la seconde étaient munis de fistules ruminale et duodénale. Les moutons de l'expérience 2 avaient, en plus, une fistule iléale. Les animaux pouvaient consommer des agglomérés de luzerne à volonté 8 h par jour dans un milieu exposé à une température normale (20 ± 2°C), avec accès libre en tout temps à l'eau et à des blocs de sel minéralisé. Dans l'expérience 1, le PIV était infusé par un cathéter introduit dans l'artère gastrique à raison de 1 nmol min -1 3 heures par jour pendant 10 min, durant 4 journées consécutives. Dans l'expérience 2, l'infusion à la dose de 1,5 nmol min -1 se faisait 10 min par demi-heure, 3 heures par jour, durant 7 journées consécutives. Les moutons témoins recevaient une infusion de soluté salin. L'infusion de PIV produisait des accroissements respectifs (P < 0,05) de l'ingéré de 14,3 % dans l'expérience 1 et de 26,1 % dans l'expérience 2. Dans l'expérience 2, il y avait une régression positive (P < 0,01) de l'ingéré alimentaire sur le transit duodénal de m.s. (n = 5, r 2 = 0,67), de m.o. (n = 5, r 2 = 0,68) et d'acides aminés (n = 5, r 2 = 0,85). ...

Effect of vasoactive intestinal polypeptide and environmental temperatures on feed intake, digesta flow and nutrient digestion in sheep

“…While the clearance rates in the liver and lung are reported to be very high (Bernhard et al 1989), it is not known whether enough VIP would escape degradation to induce a central or broader systemic response. The significant effect of VIP on 8 h feed intakes observed in a previous study (Li et al 2000) suggests that its effect was of short duration because the stimulation of feeding was apparently not sustained for the longer feeding duration of 24 h used in this study. Short-term effects of VIP include a longer duration of opening of the ROO (Okine and Mathison 1996) with potential effects on digesta passage (Mathison et al 1995).…”

“…In a previous study (Li et al 2000), VIP was shown to increase DMI when sheep had feed available for 8 h per day. Extending the duration of feed availability to 24 h from the 8 h used in previous experiments appeared to reduce the likelihood of observing an effect of the brief, intermittent infusions of VIP on DMI.…”

“…Relaxation of the ROO mediated by neurological and endocrinological systems and other determinants of passage from the reticulo-rumen might be involved in the regulation of digesta passage rate . Li et al (2000) reported that infusion of VIP into the gastric artery of sheep increased feed intake when the animals were given access to feed for a limited time (8 h) each day. Vasoactive intestinal polypeptide has also been shown to regulate exchange of ions and water (Chikhlssa et al 1992;Nassar et al 1995) and amino acid absorption in the rat (Nassar et al 1995).…”

“…The short half-life of VIP likely limits its influence on gastrointestinal motility, digesta flow and intake behaviors to a relatively short term, particularly to the period of infusion or release. During the experiments in which feed availability was limited to 8 h per day (Li et al 2000), the duration of VIP administration (intermittent infusion over 3 to 4 h per day) covered a large proportion (37-50%) of available feeding time (8 h) and produced a significant change in intake. In the current experiments, the intermittent infusions covered a smaller proportion (12.5%) of the potentially available feeding time (24 h).…”