Replacing Soybean Meal with Urea in Diets for Heavy Fattening Lambs: Effects on Growth, Metabolic Profile and Meat Quality

Abstract

Simple SummaryThere is a renewed interest on the potential inclusion of urea in ruminant diets, reducing the contribution of vegetable protein supplements. This study was designed to evaluate the effect of replacing soybean meal with different proportions of urea in protein-rich diets for heavy fattening lambs (from 29 to 50 kg of live body weight). Our results suggest that 39% of soybean meal of such diets can be replaced with urea reducing the feeding costs without any adverse effects on feed efficiency, rumen fermentation, or carcass and meat quality. Nevertheless, urea supplementation even at levels of 1% of dry matter may trigger mild metabolic acidosis that can affect animal health in the long term.AbstractThirty-six Assaf male lambs (29.4 ± 3.10 kg body weight (BW)) were used to study the feasibility of including urea (at 0, 0.6 or 0.95% of dry matter for Control, Urea1, and Urea2 diets, respectively) in substitution of soybean meal in fattening diets. Animals were individually penned and feed intake was recorded daily. Blood samples were taken at days 35 and 63 of the experimental period to determine the acid-base status and the biochemical profile. At the end of the experiment (nine weeks), lambs were slaughtered, ruminal contents were collected and carcass and meat quality were evaluated. There were not differences (p > 0.05) among treatments in dry matter intake, animal performance, ruminal fermentation pattern, and carcass and meat parameters. Serum albumin concentration was higher and concentration of HCO3 and total CO2 in blood were lower in Urea2 compared to Urea1 and Control lambs. These results, together with the tendency to lower (p = 0.065) blood pH in this group might suggest a moderate metabolic acidosis. Partial replacement of soybean meal with urea did not impair growth rate in heavy fattening Assaf lambs (from 29 to 50 kg body weight), reduced feeding costs and had no adverse effects on feed efficiency, rumen fermentation and carcass and meat quality.

Effects of urea supplementation on ruminal fermentation characteristics, nutrient intake, digestibility, and performance in sheep: A meta-analysis

“…Ruminal NH 3 -N is an equilibrium between dietary N degradation, microbial protein synthesis utilization, and N absorption. Greater NH 3 -N production from dietary sources is not necessarily reflected in a higher ruminal NH 3 -N concentration [14]. The current meta-analysis shows urea supplementation had a minor effect on the microbial N supply and total protozoa population.…”

“…Ammonia accumulation from urea degradation may increase ruminal pH [13]. The rate of ureagenesis determines the disposal of bicarbonate and affects the maintenance of pH homeostasis [14].…”

Dietary Administration of L-Carnitine During the Fattening Period of Early Feed Restricted Lambs Modifies Ruminal Fermentation but Does Not Improve Feed Efficiency

“…Additionally, 3 g of ileal content was mixed with 6 ml of purified Milli-Q water and then acidified using 0.25 ml of sulfuric acid solution. NH 3 -N concentration in the rumen content was determined by a modified colorimetric method ( Wheatherburn, 1967 ) and SCFAs in ruminal and ileal contents were determined according to Saro et al (2019) .…”

The effect of ammoniated maize stover inclusion in diets on growth performance, physiological characteristics and meat quality in lambs

“…Regardless of the AMS inclusion level in the diets, no differences were observed in terms of the three meat colour coordinates. According to Saro et al (2019), diet is one of the extraneous factors affecting carcass characteristics and meat quality parameters. El bukhary (2005) also indicated that meat colour is affected by diet.…”