Effects on plasma insulin of intermittent infusions of propionic acid, glucose or casein into the alimentary tract of non-lactating cows maintained on a liquid diet

Abstract

1. An experiment was conducted using three non-lactating cows completely maintained by infusions of volatile fatty acids into the rumen, and casein into the abomasum. Plasma insulin responses to propionic acid, glucose or casein were recorded. Further information was obtained using protein-free infusions.2. When part of the propionic acid was infused into the rumen in a twice-daily 3 h dose and the remainder infused continuously with acetic and butyric acids and casein, there were large increases in the concentrations of propionic acid and insulin in the jugular blood. When glucose, corresponding in energy to that supplied by the intermittent propionic acid infusions was similarly infused, the plasma levels of glucose and insulin were increased. Glucose appeared to stimulate a greater increase in insulin than did propionic acid. Casein infused into the abomasum in intermittent doses produced a rise in plasma insulin, but smaller than that observed with propionic acid or with glucose.3. The protein-free infusion was characterized by a lower concentration of insulin in the blood plasma, a reduction in plasma urea and free amino nitrogen and unchanged plasma glucose.Glucose, volatile fatty acids (VFA) and amino acids (AA) are generally considered to be potential stimuli for insulin secretion in the ruminant. There are various reports of intravenous infusion of glucose or VFA having produced elevation in plasma insulin concentration (Manns & Boda, 1967; Horino et al. 1968). Similar rises were not observed when these nutrients were infused into the abomasum and rumen respectively, so as to ensure more normal absorption and metabolism (Sterm et al. 1970;Bassett, 1972).The present experiment was designed to measure plasma insulin and metabolites in cattle when glucose, propionic acid or casein were infused as intermittent doses or continuously into the rumen or abomasum. Information on metabolites in the blood plasma of ruminants maintained on protein-free diets is not easy to interpret, since protein of rumen microbial origin is still digested and absorbed in the small intestine. A study was made when the animals were maintained on a protein-free infusion. E X P E R I M E N T A L Animals and treatmentsThree non-lactating Friesian cows, each fitted with a rumen cannula and with an abomasal catheter, were used. Their initial and final average live weights were 517 and 576 kg respectively. They were infused as described by MacLeod et al. (1982). No solid food was offered. The infusion room temperature was maintained at approximately 22" and the level of infusion was calculated to be approximately 1.5 x maintenance energy from an estimated requirement of 0450 MJ/kg live per d. The cows were allocated to a randomized sequence of six treatment periods, each of 7 d duration. When increased amounts of VFA or different mixtures were required for consecutive treatments, the change was effected gradually over 2 d. Vtdnnaires, 45,

Autonomic regulation of plasma insulin, glucagon and growth hormone responses to feeding in sheep fed a diet supplemented with calcium propionate

“…Physiological doses of propionate infusion into the rumen and blood increased plasma insulin and glucagon concentrations in ruminants (De Jong 1982;Istasse et al 1987;Sano et al 1993). In the present study, propionate supplementation also appeared to enhance the postprandial release of insulin and glucagon ( Fig.…”

“…La libération de l'insuline se fait par l'entremise de l'activation du système nerveux parasympathique, encore que dans nos travaux les réponses n'étaient pas significatives, alors que la libération du glucagon passe par l'activation, à la fois du système nerveux parasympathique (SNP) et par les (-récepteurs adrénergiques du système nerveux sympathique (SNS). Ces observations n'apportent aucun appui à l'hypothèse d'une éventuelle intervention du système nerveux autonome dans la régulation de la libération de GH.Mots clés: Système nerveux autonome, insuline, glucagon, hormone de croissance, propionate, moutonIn ruminants, volatile fatty acids (VFA) produced in the rumen may alter the release of insulin, glucagon and growth hormone (GH) (De Jong 1982;Istasse et al 1987;Matsunaga et al 1997). Propionate is the second most abundant VFA after acetate in the rumen and blood.…”

“…In ruminants, volatile fatty acids (VFA) produced in the rumen may alter the release of insulin, glucagon and growth hormone (GH) (De Jong 1982;Istasse et al 1987;Matsunaga et al 1997). Propionate is the second most abundant VFA after acetate in the rumen and blood.…”

The effect of supplemental propionate on insulin responsiveness to glucose and tissue responsiveness to insulin in relation to feeding in sheep

“…Moreover, intraruminal and intravenous infusions of propionate have been shown to increase plasma insulin concentrations in ruminants [2,5,11]. Therefore, supplemental propionate seemed to influence glucose metabolism in the whole-body and its endocrine control.…”

“…Deux techniques de clamp glycémique ont été utilisées pendant 6 h, à partir de 2 h avant le début de la prise d'aliments pour étudier l'effet d'un supplément alimentaire de propionate sur la réaction insulinique et la réaction tissulaire à l'insuline en rapport avec l'alimentation chez des béliers. Les [2,5,11]. The VFA molar ratio in the rumen has previously been changed by switching from low to high concentrate diets in lambs [10].…”