Chronic metabolic responses of postpartal dairy cows to subcutaneous glucagon injections, oral glycerol, or both

Abstract

We examined the long-term effects of daily subcutaneous injections of 15 mg of glucagon during the first 14 d postpartum with or without coadministration of 400 mL of pure glycerol orally on blood metabolites and hormones and liver composition of Holstein dairy cows during early lactation. Fourteen multiparous cows with body condition score of >or=3.5 points (1-5 point scale) were assigned randomly to one of 4 treatment groups-saline, glucagon, glycerol, or glucagon plus glycerol. Fatty liver syndrome was induced by feeding cows a dry-cow ration supplemented with 6 kg of cracked corn daily during the last 6 wk of the dry period. Compared with saline treatment (n=3), coadministration of glucagon and glycerol (n=4) increased plasma glucose and insulin and decreased plasma nonesterified fatty acid concentrations in both treatment weeks, whereas glucagon alone (n=3) produced similar changes plus a decrease in plasma beta-hydroxybutyrate in the second week only. No significant changes were observed for the glycerol alone treatment (n=4). We conclude that a single daily dose of glycerol for the first 14 d postpartum may potentiate the action of glucagon in the first treatment days to alleviate some symptoms of fatty liver syndrome, such as the increase in plasma nonesterified fatty acids and the decrease in plasma glucose and insulin, in Holstein dairy cows after parturition.

Effect of peripartum dietary energy supplementation on thyroid hormones, insulin-like growth factor-i and its binding proteins in early lactation dairy cows

“…Group 3 compounds, the alcohols, do not have these disadvantageous properties and seem to be the most promising for general application. Consumed orally, glycerol is metabolized in the rumen and liver to intermediates of gluconeogenesis and glycolysis with the potential to alleviate postpartal NEB (Osman et al, 2010).…”

Effects of glucagon, glycerol, and glucagon plus glycerol on gluconeogenesis, lipogenesis, and lipolysis in periparturient Holstein cows

“…Lower glycerol release rates in postpartal versus prepartal stage can be attributed to the low responsiveness of adipose tissue to epinephrine in late pregnancy and early postpartum compared with mid-lactation times . On the other hand, elevated BHBA concentrations in plasma in the first pospartal week in saline group (Osman et al, 2010) may inhibit lipolysis in the pospartal stage. In vitro incubation of bovine adipose tissue with BHBA significantly decreased glycerol release rate (Metz et al, 1974).…”

“…In his recent study, Osman et al (2010) investigated the chronic effects of subcutaneous injections of glucagon oral administration of glycerol for 14 days to dairy cows starting as early as calving rather than at day 2 postpartum. The early postpartal glucagon injections increased plasma glucose and plasma glucagon concentrations and decreased plasma NEFA concentrations but did not affect plasma TAG concentrations.…”

“…It was concluded that glycerol actually potentiates the glucagon effect, and thus glucagon plus glycerol is a more efficient treatment than glucagon injection alone. In addition, acute effects of glucagon injections and glycerol administration also were measured (Osman et al, 2010) Serial blood samples were collected during 8-hr period after starting glucagon and/or glycerol treatment. The early postpartal glucagon injections increased plasma glucose and plasma glucagon concentration and decreased plasma NEFA concentration and increased plasma glucose concentration; however, plasma glucagon concentration decreased.…”

“…and pyruvate kinase in early lactating cows (Bobe et a., 2009). When co-administered with glucagon subcutaneous injections, oral glycerol potentiates glucagon preventive action (Osman et al, 2008;Osman et al, 2010). Orally administered glycerol is metabolized in the rumen and liver to VFA and in liver to intermediates of gluconeogenesis and glycolysis (Remond et al, 1993;Goff and Horst, 2001;Osman et al, 2008).…”