Influence of dietary urea level on digestive function and growth performance of cattle fed steam-flaked barley-based finishing diets

Abstract

Four Holstein steers (282 kg) with cannulas in the rumen and proximal duodenum were used in a 4 x 4 Latin square experiment to evaluate the influence of dietary urea level (0, 0.4, 0.8, and 1.2%, DM basis) in a steam-flaked barley-based finishing diet on digestive function. There were no treatment effects (P > 0.20) on ruminal digestion of OM and ADF. Increasing dietary urea level increased (linear, P < 0.01) ruminal starch digestion. Ruminal degradability of protein in the basal diet (no supplemental urea) was 60%. Increasing dietary urea level did not increase (P > 0.20) ruminal microbial protein synthesis or nonammonia N flow to the small intestine. There were no treatment effects (P > 0.20) on total-tract ADF digestion. Total tract digestion of OM (quadratic, P < 0.01) and starch (linear, P < 0.05) increased slightly with increasing urea level. Urea supplementation increased (linear, P < 0.01) ruminal pH 1 h after feeding; however, by 3 h after feeding, ruminal pH was lower (cubic, P < 0.05) with urea-supplemented diets. Urea supplementation did not affect (P > 0.20) ruminal molar proportions of acetate and propionate. One hundred twenty crossbred steers (252 kg; approximately 25% Brahman breeding) were used in an 84-d feeding trial (five pens per treatment) to evaluate treatment effects on growth performance. Daily weight gain increased (linear, P = 0.01) with increasing urea level, tending to be maximal (1.53 kg/d; quadratic, P = 0.13) at the 0.8% level of urea supplementation. Improvements in ADG were due to treatment effects (linear, P < 0.01) on DMI. Urea supplementation did not affect (P > 0.20) the NE value of the diet for maintenance and gain. Observed dietary NE values, based on growth performance, were in close agreement with expected based on tabular values for individual feed ingredients, averaging 100.4%. We conclude that with steam-flaked barely-based finishing diets, ruminal and total-tract digestion of OM and ruminal microbial protein synthesis may not be increased by urea supplementation. In contrast, ADG was optimized by dietary inclusion of 0.8% urea. Urea supplementation may not enhance the net energy value of steam-flaked barely-based finishing diets when degradable intake protein is greater than 85% of microbial protein synthesis.

Effects of a combining feed grade urea and a slow-release product on performance, dietary energetics and carcass characteristics of steers fed finishing diets

“…Cattle were weighed at the start of experiment, at day 35 and before the steers were harvested (day 73). Based that the better responses on microbial duodenal flows and digestible energy of diet was observed only when U and SRU was combined at same proportion (0.80% of each) in diets which proportion of S:ADF is about 4.5 (López-Soto et al 2014) and that previous reports (Milton et al 1997;Zinn et al 2003) have shown that supplemental U has more positive effects on growth performance or dietary energy utilization when the diet contains a ADF ratio of greater than 5.0, thus, to test our hypothesis, four treatments were formulated as follows. The treatment 1 (SRU) consisted in combining U and SRU product (Optigen II; a polymer-coated urea, Optigen, Alltech Mexico, Guadalajara, Jalisco).…”

“…It has been observed that in highgrain diets (a starch:ADF ratio of greater than 5.0:1), U can be supplemented at a level 50% higher than the (NRC 1984), EG is the daily energy deposited (Mcal/day) estimated by equation: EG = ADG 1.097 × 0.0557W 0.75 (NRC 1984), and DMI is the average daily dry matter intake (Zinn et al 2008). f Observed to expected dietary NE ratio was computed by dividing NE observed between expected diet NE, which was estimated based on tabular values for individual dietary ingredients (NRC 1996 recommended with positive effects on growth performance or in dietary energy utilization (Milton et al 1997;Zinn et al 2003). One possible advantage to higher U levels in finishing diets might be related to the buffering effects of U as a result of its hydrolysis to CO 2 and NH 3 and the potential buffering effects via ammonia (Galyean 1996), and/or because the synchrony of ruminal degradation rates between feed grade U and starch is maybe more favourable in these types of diets.…”

“…Previous reports (Milton et al 1997;Zinn et al 2003) have shown that supplemental U has more positive effects on growth performance or dietary energy utilization when the diet contains a starch:acid detergent fibre (S:ADF) ratio of greater than 5.0. However, as a result of the cost of grains, the replacement of grains by co-products (i.e., dried distillers grain with solubles) in feedlot diets is a common practice (Klopfenstein et al 2008).…”

Effects of dietary urea concentration on performance and health of receiving cattle and performance and carcass characteristics of finishing cattle

“…For finishing cattle diets using steam-flaked sorghum grain, it seems, overall, that there is no great advantage to using urea as the supplemental nitrogen source. Despite no statistical differences in performance or carcass characteristics in the present study, more work is needed to identify other potential mechanisms responsible for increased performance among different cereal grain diets with urea supplementation [e.g., corn, Milton et al (1997), barley, Zinn et al (2003)]. Cereal grains vary in both ruminal and total tract starch digestion (Galyean and Rivera 2003) with sorghum grain ranking lower than corn, barley and wheat.…”

Performance and metabolic pattern of feedlot lambs using soyabean hulls associated to different non-protein nitrogen sources

“…A restrição de proteína degradável no rúmen na dieta compromete o ganho médio diário, principalmente pelo menor consumo de matéria seca, pela menor digestão ruminal e menor síntese microbiana (Zinn et al, 2003). A alternativa, no intuito de corrigir esses níveis de proteína, é a utilização de fontes proteicas adicionais, por substituição tanto parcial como total da fonte de nitrogênio da dieta por uma fonte de nitrogênio não-proteico, como a ureia, o que pode reduzir o custo do nitrogênio e da suplementação protéica (Owens & Zinn, 1988).…”