Fecal nitrogen excretion in dairy cows supplemented with feed additive containing active dry yeast

Abstract

The aim of the study was to determine the fecal excretion of N (TN and NH4 +-N) in dairy cows receiving the feed supplement Biolife® (Eurovix S.p.A., Italy) containing active dry yeast Saccharomyces cerevisiae. Two groups of 14 Holstein cows (B – experimental; C – control) at tie-stalled breeding participated in the experiment. Group B received the feed supplement through the total mixed ration (TMR). Fresh feces samples from both groups were collected on d 7, 14, 21, 28, 35 from the start of supplementation. Mean values of fecal pH and excreted DM did not differ between groups. The concentration of NH4 +-N in the fecal samples of group B was reduced by 28.05%, average for the entire studied period (P<0.05). In the period d 21-35, this reduction was 35% (P=0.095). Excreted TN, averaged over the entire period, was reduced by 16.18% in group B, but the difference was not statistically significant. The reduction of TN content in feces from group B was more pronounced in the period d 21-35, when the reduction was 31.99% compared to group C (P=0.084). A period of at least 14 days is required for adaptation to the supplement and for an occur effect on N excretion.