The influence of increased protein content in the diet on renal functions in calves

Abstract

The aim of this work was to study the effect of feeding calves in the neonatal period a diet with increased protein content on their renal function. The experiment was carried out in 3 phases on 10 clinically healthy black and white calves. The diet fed to calves in phase 2 was enriched with 25% casein compared to standard diet fed in phases 1 and 3. Studies on kidney functions in calves were perfomed using clearance methods in phase 1, further 7 and 14 days after introducing phase 2, and 7 days after return to standard diet (phase 3), using inulin and PAH (para-aminohippuric sodium salt) as testing substances. Glomerular filtration rate (GFR) and PAH clearance (ERPF Effective Renal Plasma Flow) were defined on the basis of inulin and PAH elimination rate from blood. Effective renal blood flow (ERBF) and filtration fraction (FF) were also calculated. Additionally the blood plasma electrolyte concentrations (Na, K,Cl), total protein content and urea concentration were also determined. Increased protein amount in the diet did not affect the total protein and urea concentration in plasma. At the same time, the Na+ concentration increased and the K+ concentration decreased. However, there were no significant changes in Cl-concentration and in plasma osmolality. Further, an increase of renal blood and plasma flow, increase of glomerular filtration rate (GFR) and filtration fraction were observed. These changes were statistically significant (P < 0.01). The results show that intake of a protein-rich diet modifies the renal functions in calves during their early postnatal period. Seven-day long period of feeding the animals a diet with casein supplement caused the renal blood and plasma flow to increase, and FF was higher, too. One may presume that it was the expression of mobilizing the adaptation mechanisms to effectively remove protein metabolism products from the organism. Renal hemodynamics changes induced by the protein-rich diet involved first of all the glomerular area as a prerequisite for plasma hyperfiltration.