title: Metabolism of propionate and 1,2-propanediol absorbed from the washed reticulorumen of lactating cows.
abstract: To investigate the metabolism of 1,2-propanediol (PPD) in lactating cows independently of normal rumen microbial metabolism, three ruminally cannulated lactating Holstein cows were subjected to three experimental infusion protocols under washed reticulo-ruminal conditions in a Latin square design. Reticulo-ruminal absorption rates were maintained for 420 min by continuous intraruminal infusion of VFA and PPD. With the control treatment, 1,246 +/- 39 mmol/ h of acetate and 213 +/- 5 mmol/h of butyrate were absorbed from the reticulorumen. With the propionate treatment, 1,148 +/- 39 mmo/h of acetate, 730 +/- 23 mmol/h of propionate and 196 +/- 5 mmol/h of butyrate were absorbed from the reticulorumen. With PPD treatment, 1,264 +/- 39 mmol/h of acetate, 220 +/- 5 mmol/h of butyrate and 721 +/- 17 mmol/h of PPD were absorbed from the reticulorumen. Glucose irreversible loss rate (ILR), as well as the relative enrichment of plasma lactate and alanine, were determined by primed continuous infusion of [U-13C]glucose in a jugular vein. Treatments did not affect (P > 0.10) the plasma concentrations of glucose (4.2 +/- 0.1 mmoVL), alanine (0.14 +/- 0.01 mmol/L), or insulin (80 +/- 25 pmol/L). The plasma concentration of lactate was higher (P < 0.05) with both propionate (0.84 +/- 5 mmol/L) and PPD treatment (0.81 +/- 5 mmol/ L) compared with the control treatment (0.29 +/- 0.5 mmol/L). The plasma concentration of pyruvate was higher (P < 0.05) with the propionate treatment (0.09 +/- 0.01 mmol/L) compared with the control treatment (0.03 +/- 0.01 mmol/L). The plasma concentration of 3-hydroxybutyrate was lower (P < 0.05) with the propionate treatment (0.15 +/- 0.03 mmol/L) compared with the control treatment (0.40 +/- 0.03). With the PPD treatment, the plasma concentrations of pyruvate and 3-hydroxybutyrate were in between the other treatments and tended (P < 0.10) to be different from both. The plasma concentration of PPD increased throughout the infusion period with the PPD treatment and reached a concentration of 4.9 +/- 0.6 mmol/L at 420 min. The ILR of glucose was not affected (P > 0.10) by treatments (441 +/- 35 mmol/h). The relative 13C enrichment of plasma lactate compared with that of glucose decreased (P < 0.05) with the PPD treatment compared with the control treatment (44 to 21 +/- 3%). It was concluded that PPD has a low rate of metabolism in cows without a normal functioning rumen, although about 10% of the absorbed PPD was metabolized into lactate.
authors.affiliation: Danish Institute of Agricultural Sciences, Department of Animal Nutrition and Physiology, Tjele. nielsb.kristensen@agrsci.dk
authors.forename: N B
authors.initials: NB
authors.lastname: Kristensen
authors.forename: A
authors.initials: A
authors.lastname: Danfaer
authors.forename: B A
authors.initials: BA
authors.lastname: Røjen
authors.forename: B M L
authors.initials: BM
authors.lastname: Raun
authors.forename: M R
authors.initials: MR
authors.lastname: Weisbjerg
authors.forename: T
authors.initials: T
authors.lastname: Hvelplund
mesh_terms: D000042:Absorption; D000818:Animals; D002417:Cattle / Q000378:metabolism*; D004734:Energy Metabolism; D005232:Fatty Acids, Volatile; D005260:Female; D005947:Glucose / Q000378:metabolism; D007263:Infusions, Parenteral / Q000662:veterinary; D007773:Lactates / Q000378:metabolism; D007774:Lactation; D011422:Propionates / Q000378:metabolism / Q000493:pharmacokinetics*; D019946:Propylene Glycol / Q000378:metabolism / Q000493:pharmacokinetics*; D012417:Rumen / Q000187:drug effects / Q000378:metabolism*
chemical_list: D005232:Fatty Acids, Volatile; D007773:Lactates; D011422:Propionates; D019946:Propylene Glycol; D005947:Glucose