EFFECTS OF PROPYLENE GLYCOL OR GLYCEROL SUPPLEMENTATION OF THE DIET OF DAIRY COWS ON FEED INTAKE, MILK YIELD AND COMPOSITION, AND INCIDENCE OF KETOSIS

Abstract

In two experiments designed to test the antiketogenic properties of propylene glycol and glycerol, concentrate mixtures containing 3, 6, or 9% propylene glycol or 3 or 6% glycerol were fed for the first 8 wk of lactation to a total of 120 cows. In the first experiment there were no significant effects (P > 0.05) of supplementation on milk yield and composition, feed intake, or energy balance. The cows fed a concentrate mixture containing 6% glycerol appeared to lose less body weight than the control cows or those fed concentrate containing either 3% glycerol or 3% propylene glycol. Cows fed the unsupplemented concentrate mixture were apparently less efficient in utilizing metabolizable energy than cows receiving either of the three supplemented rations but these differences were not significant (P > 0.05). There were no incidences of clinical ketosis and only 14 occurrences of positive ketone reactions in the milk (five on control, three on the 3% propylene glycol, four on 3% glycerol, and two on 6% glycerol). In the second experiment cows were subjected to slightly greater nutritional stress, which resulted in elevated ketone levels in 31 samples of milk from control cows, six from cows fed 3% propylene glycol, two for cows fed 6% propylene glycol, and three for cows fed 9% propylene glycol. Four cows, all on the control ration, developed clinical ketosis requiring glucose therapy. There were no consistent effects of propylene glycol on feed intake, body weight change, or efficiency of ration utilization. Propylene glycol supplementation appeared to increase milk yield at the 3 and 6% level and caused a slight decrease in milk fat and an increase in milk lactose percent.