Effects of Dietary Protein Upon Concentrations of Urea in Peripheral Plasma and Uterine Fluid in Dairy Cattle

Abstract

There have been concerns that elevated urea nitrogen concentrations in uterine fluid had significant effects on bovine spermatozoal motility and survival. However, it is still uncertain whether dietary protein has any effects upon concentration of urea nitrogen and ammonia in the peripheral plasma and uterine fluid in dairy cattle. The objectives of the study were to investigate the effects of dietary protein intake on concentrations of (i) urea nitrogen in the uterine fluid, (ii) ammonia in the blood and (iii) urea nitrogen in the peripheral plasma. Six lactating, non-pregnant and normally cycling Friesian cows were used in two randomly divided equal groups, receiving either a low or high dietary protein intake. Uterine fluids and blood samples were collected from each cow and uterine urea nitrogen; blood ammonia and plasma urea nitrogen concentrations were measured. The study showed that the cows fed the high protein (HP) diet had significantly higher uterine urea nitrogen, blood ammonia and plasma urea nitrogen concentrations than cows fed the low protein (LP) diet. The results revealed that the concentration of urea nitrogen in the uterine fluid were higher in cows fed HP diet compared with those fed a LP diet. These results suggested that high concentrations of urea in the plasma could diffuse into the uterine lumen and might create a sub-optimal environment in the uterus, which might act as an antagonist to fertility. The high level of blood ammonia and plasma urea nitrogen concentration in the HP fed cows, which could occur due to high protein intake, may affect the viability of sperm, ova and embryos and the growth and survival of the foetus by producing biochemical, endocrionological and tissue derangement. Therefore, it is likely that excessive concentration of urea nitrogen in peripheral plasma and uterine fluid and plasma ammonia of high protein fed lactating cows may be detrimental to the viability of sperm, ova, embryos or foetus.