EFFECT OF PROPYLENE-GLYCOL SUPPLEMENTATION AROUND PARTURITION ON MILK-YIELD, REPRODUCTION PERFORMANCE AND SOME HORMONAL AND METABOLIC CHARACTERISTICS IN DAIRY-COWS

Thirty-nine multiparous Holstein cows were used to measure the effect of propylene glycol treatment around parturition on milk yield, reprod uctive efficiency and some hormone and metabolite concentrations. Cows were assigned randomly to control (n = 19) or propylene glycol treate d (n = 20) groups. Propylene glycol (300 g) was administered directly mixed with the diet from day 10 prior to the expected calving date unt il parturition (day 0) and orally after dilution in 1 l water on days 3, 6, 9 and 12. Blood samples were collected on days -20, -5, 0, 3, 10 , 25 and 50 while milk samples were taken weekly until 13 weeks post p artum. Body condition scores, recorded on days -20, 15 and 50, were no t affected by propylene glycol administration. Propylene glycol did no t significantly affect milk yield or composition but linear somatic ce ll score measured from the first 13 weeks post partum was reduced by p ropylene glycol administration (P < 0.01). Moreover, propylene glycol reduced milk urea (-25 mg/l, P < 0.05), especially during the first 9 weeks post partum. Plasma insulin concentrations were similar in both groups during the experiment while insulin-like growth factor I (P < 0 .05) and insulin-like growth factor-binding protein 3 (P < 0.001) leve ls were higher on days 10, 25 and 50 post partum in the propylene glyc ol group. Propylene glycol administration decreased plasma non-esterif ied fatty acid concentrations (P < 0.05 to P < 0.01) but increased tot al cholesterol levels (P < 0.01) after parturition while 3-hydroxybuty rate levels were unaffected by the treatment. Changes in the hormone a nd metabolic concentrations after propylene glycol administration in t he last few days of gestation and the first week of lactation seem to indicate that energy balance in the treated group was probably more po sitive than in the control group. There was also evidence that propyle ne glycol administration prevented fatty liver syndrome and hastened t he resumption of oestrous cycles (P < 0.001).