RUMINAL ENVIRONMENT CHARACTERISTICS IN STEERS SUPPLEMENTED WITH LOW SOLUBILITY UREA

Abstract

In order to evaluate the protein supplementation with low solubility urea on ruminal environment characteristics, we used two steers fitted with ruminal fistula, fed with Digitaria swazilandensis hay plus a concentrate mix. Thirty percent of the maintenance protein requirement was replaced by urea, highly soluble in the rumen (NASR) and low ruminal soluble urea (NBSR). Ruminal environment was evaluated at 0; 0.5; 1; 2; 4 and 6 hours post feeding, analyzing pH and ammonia nitrogen (NH₃-N) in rumen fluid and urea nitrogen (BUN) and glucose (BGL) levels in blood. Data were analyzed under a completely randomized block design with split plot arrangement and LSMEANS comparison. The pH was not affected by the type of urea (P>0,05), but by the sampling time (P<0,05). The average initial pH was 6,58, then it raised 6,80 one hour after feeding for NASR and two hours for NBSR and then decreased. The ruminal NH₃-N was different between treatment and sampling time (P<0,001) during the first two hours, showed high solubility NASR (24.6 mmol/L), suggesting loss of ruminal NH₃ level, proof of this was the BUN increase, reaching peak value after two hours post feeding (36,1 mg/dl). By supplementing NBSR, BGL levels were lower (P<0,01) and spent the first hour uniforms post feeding, promoting better synchrony between protein and energy for microbial protein synthesis, while no differences were reported between samplings post feeding (P>0,05). Using NBSR improved overall diet digestibility by 9%, leading to an increase in forage intake.