Effects of polymer-coated slow-release urea on performance, ruminal fermentation, and blood metabolites in dairy cows

Abstract

-The objective of this experiment was to quantify the effects of feeding polymer-coated slow-release urea on nutrient intake and total tract digestion, milk yield and composition, nutrient balances, ruminal fermentation, microbial protein synthesis, and blood parameters in dairy cows. Sixteen Holstein cows (580±20 kg of live weight (mean ± standard deviation); 90 to 180 days in milk (DIM); and 28 kg/d of average milk yield) were used in a replicated 4 × 4 Latin square experimental design. The animals were assigned to each square according to milk yield and DIM. The animals were randomly allocated to receive one of the following experimental diets: 1) control (without urea addition); urea (addition of 1% on the diet DM basis); polymer-coated slow release urea 1 (addition of 1% on the diet DM basis); and polymer-coated slow release urea 2 (addition of 1% on the diet DM basis). All diets contained corn silage as forage source and a 50:50 forage:concentrate ratio. Milk and protein yield, production of volatile fatty acids, and propionate decreased when cows were fed diets containing urea. Addition of urea decreased nitrogen efficiency and nitrogen excreted in the feces. However, the diets did not change the cows' microbial protein synthesis, ruminal pH, or ammonia concentration. The inclusion of urea in cow diets decreases milk and protein yield due to lower production of volatile fatty acids. No advantages are observed with supplementation of polymer-coated slowrelease urea when compared with feed-grade urea.

Effects of replacing soybean meal with slow-release urea on milk production of Holstein dairy cows

“…Miranda et al (2019) reported that there were no differences in most of the blood parameters when cows were fed various urea sources. Similar results were observed by Calomeni et al (2015), who recorded no differences in blood parameters when SBM was replaced partially with protein sources such as yeastderived microbial protein or SRU.…”

Influence of polymer-coated slow-release urea on total tract apparent digestibility, ruminal fermentation and performance of Nellore steers

“…Nevertheless, we did not detect differences on microbial protein synthesis agreeing with [28] who reported no differences in purine derivatives production of Nellore steers fed the urea sources of the current study. In addition, Calomeni et al [9] found no differences in DM intake, apparent digestibility and microbial protein synthesis of dairy cows fed the same polymer-coated SRA as used in this study or feed grade urea, but the authors added 0.9 g/kg DM of the commercial products.…”

“…These effects are related to the fact that several cellulolytic bacteria use N from ammonia to grow in rumen [7]. However, other studies have reported no effects of replacing feed grade urea by SRU on ruminal fermentation [8], nutrient digestibility and N excretion [9]. …”

Designing and evaluation of urea microcapsules in vitro to improve nitrogen slow release availability in rumen

“…Starea, biuret and complexes of urea with formaldehyde or molasses have been used in the rumen to avoid ammonia‐N toxicity; yet slow release rates have failed to improve N utilization in in vitro trials . Other commercial products based on urea used to reduce the degradation of N in the rumen are Rumapro® and Optigen®; the ruminal degradation rate of these products is comparable to vegetable protein concentrates .…”