The effects of increased level of protein in the diet with additive of propylene glycol on mammary metabolism and milk formation in goats
The experiment was performed on 6 goats in the phase of established lactation and was arranged as 2 (groups, n = 3) x 2 (periods with duration of 3 weeks) latin square. During equilibrating periods the goats were fed basal diet (BD) with recommended level of intestinally available protein (IAP) and metabolizable energy. During experimental periods additionally to basal diet sunflower oil cake (SC) was added aimed to increased IAP intake by 15% and SC + propylene glycol (PG) at a dose of 2.5 ml/kg BW<sup>0.75</sup> (SC+PG). The combined additive SC+PG increased the milk yield by 21,3% and milk protein yield by 22.9% compared to BD. During periods of BD, (BD+SC), (BD+SC+PG) the mammary blood flow, glucose concentration in milk and insulin level in blood were progressively increased, whereas arterio-venous concentration difference and efficiency of extraction from the blood for glucose and α-amino nitrogen were tended to decrease. The urea concentration in milk during period SC+PG was decreased in comparison to SC (P<0.05) indicating amelioration in productive utilization of amino acids.