Abstract
BackgroundIt is unknown which metabolites are responsible for propylene glycol (PG)-induced toxicosis, and a better understanding of the underlying mechanisms explaining incidences of abnormal behaviour of dairy cows fed PG is therefore needed.MethodsThe study included three cows of which one developed PG toxicosis. In order to investigate how the metabolism of PG differed in the cow developing toxicosis, proton nuclear magnetic resonance (NMR) spectroscopy was applied on ruminal fluids and blood plasma samples obtained before and after feeding with PG.ResultsPG toxicosis was characterized by dyspnea and ruminal atony upon intake of concentrate containing PG. The oxygen saturation of arterial blood haemoglobin and the oxygen pressure in arterial blood decreased along with the appearance of the clinical symptoms. NMR revealed differences in plasma and ruminal content of several metabolites between the cow responding abnormally to PG and the two control cows.ConclusionIt is concluded that PG-toxicosis is likely caused by pulmonary vasoconstriction, but no unusual metabolites directly related to induction of this condition could be detected in the plasma or the ruminal fluid.
Highlights
It is unknown which metabolites are responsible for propylene glycol (PG)-induced toxicosis, and a better understanding of the underlying mechanisms explaining incidences of abnormal behaviour of dairy cows fed PG is needed
The present study is based on a test-feeding trial with a pelleted concentrate containing PG, which is under development for use in very early lactation. Feeding this concentrate induced unexpectedly a condition in one out of three cows resembling PG toxicosis and the present study aimed to investigate the metabolites responsible for PGinduced toxicosis using proton nuclear magnetic resonance (NMR) spectroscopy
Comparison of the NMR spectra of ruminal fluid samples obtained 0.5 h after feeding revealed significantly lower intensities of signals assigned to isopropanol and isobutyrate (1.18 ppm), lactate (1.38 ppm and 4.35 ppm), acetate (2.08 ppm), acetone (2.63 ppm) and citrate (2.88, 2.90, 3.04 and 3.06 ppm) in the metabolite profile of the cow responding abnormally to PG compared with the two control cows (Figure 7)
Summary
It is unknown which metabolites are responsible for propylene glycol (PG)-induced toxicosis, and a better understanding of the underlying mechanisms explaining incidences of abnormal behaviour of dairy cows fed PG is needed. Propylene glycol (PG) has been used as a glucogenic feed supplement for ruminants for decades [1]. Acta Veterinaria Scandinavica 2009, 51:25 http://www.actavetscand.com/content/51/1/25 observation of shallow breathing, ataxia, salivation, somnolence and depression when adding PG to the feed of dairy cows [3]. In a field trial involving 7 dairy herds, cows were fed either 0, 150, 300 or 450 g PG/d from 20 to 14 d antepartum [4]. In 3 out of the 7 herds approximately 36% of the cows reacted during the first few days of application by signs described as hyperventilation and somnolence
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