Abstract
Our objective was to determine the relationship between polyethylene glycol feeding and blood secretion of insulin and progesterone in lactating dairy cows. Thirty lactating Holstein cows were studied from 3 days before in heat till day 9 of sexual cycle (all together 12 days). Treatment cows were fed 850 ml of propylene glycol a day. All cows were fed similar TMR ration. Intake of feed and production of milk per cow were measured twice daily. Blood samples were taken 3 times a day. Concentrations of insulin were determined in blood sampled 3 times along the trial, progesterone were determined in blood sampled every day. Milk yield was higher in treatment group before starting the trial. The treatment did not affect milk yield. The differences between the groups have been retained along the treatment. The difference in insulin concentrations as a function of cycle day, were significant p <0.05. It was found that the concentration of insulin in the treatment group increased after six days of treatment (4 day class). This difference was retained even after eleven days of treatment (cycle day 9). The results found in plasma progesterone concentration from day 4 of the sexual cycle show significant difference which grew from day 9 of the cycle till last day of measurement p <0.05. Short-term treatment (9 days of treatment) of feeding propylene glycol prior to insemination of high producing dairy cows caused a clear increase in peripheral blood insulin concentrations. The treatment is also found to be effective for increasing plasma level of progesterone significantly.