Urea Rations Research Articles

Abomasal Nitrogen in Steers Fed Soybean Meal, Urea or Urea Plus Two Levels of Molasses

The quantity and quality of nitrogen reaching the abomasum of steers fed SBM, urea, urea and 2.5% molasses or urea and 10.0% molasses were determined using four abomasal fistulated steers in a 4×4 latin square. Total nitrogen reaching the abomasum, estimated by nitrogen:chromic oxide ratios was determined and separated into protein, bound-amino and free-amino nonprotein nitrogen and purine-pyrimidine nitrogen. Quantitative estimates revealed that only 79.4% as much nitrogen reached the abomasum in steers fed urea as in steers fed SBM. Addition of 2.5% molasses to urea increased daily abomasal nitrogen to 92.5% of that from SBM feeding, and addition of 10.0% molasses to urea was of no benefit over 2.5% molasses. While differences between means were not statistically significant (P>.05), significant treatment effects were recorded at P<.2. Abomasal nitrogen composition was similar on all rations with the urea ration showing somewhat lower quantities of purine-pyrimidine nitrogen. There were no differences due to ration treatment in the amino acid composition of abomasal contents.

Effect of Dehydrated Alfalfa, Molasses and Pelleting on Utilization of Urea Rations

Digestion trials determined the effect of including in the supplement, dehydrated alfalfa and molasses and of pelleting on utilization of urea-containing rations. All possible combinations of these three variables were tested. The basal ration contained 57% corn and 25% corn cobs. The supplement supplied the total ration with 1% urea, additional vitamins and minerals and sufficient soybean meal to equilibrate ration nitrogen. Dehydrated alfalfa and molasses were each tested in the supplements to supply 5% of the total ration. Ground corn was included to complete the supplements and to facilitate pelleting. Eight steers were employed in digestion-metabolism trials according to a 2×2×2 factorial plan of two 4×4 quasi-Latin squares.Dehydrated alfalfa did not influence digestion of ration components or affect nitrogen retention. Dehydrated alfalfa tended to detract from palatability. Molasses appeared to improve acceptance of the alfalfa containing supplements whereas pelleting had no effect. Molasses tended to increase dry matter and ether extract digestibility, but had no apparent effect on digestion of other components or nitrogen retention. Pelleting significantly decreased digestibility of dry matter and crude protein and also tended to depress nitrogen-free extract digestibility but had no effect on nitrogen retention. None of the factors evaluated, nor their interactions, significantly improved utilization of the ration.

Feed Processing. VII. Effect of an Expansion-processed Mixture of Grain and Urea (Starea) on Rumen Metabolism in Cattle and on Urea Toxicity1,2

Starea was compared with several other feed processing treatments for utilization of urea. It is an expansion-processed mixture of gelatinized grain starch and urea. All rations contained about 5% urea, and the grain was sorghum.In a first experiment 2 pairs of identical twin cattle were fed rations of urea and grain that had been a) cracked, b) finely ground and pelleted, c) expanded or d) made into Starea. The rations were changed each week, consequently after 4 weeks the individual animal had been fed all 4 rations. The sequence was repeated once. Finely ground pelleted grain, expanded grain and Starea were not different from one another in their effect on rumen ammonia concentration. However, all 3 rations compared with cracked grain lowered rumen ammonia concentration (P<.01). Starea was eaten more readily than the 3 other rations.In a second experiment, Starea and the cracked grain plus urea ration (control) were fed to the 2 pairs of identical twin cattle. The total quantity and concentration of bacterial and protozoal nitrogen were significantly greater in the rumen contents of the Starea-fed animals than in those of the controls. The rumen ammonia concentration of the Starea-fed animals was lower than that of the controls. These differences approached statistical significance (P<.05) in the 1-and 2-hr samples.

Amino and urea nitrogen levels in lambs receiving different nitrogen sources and injections of lysine and methionine.

Two trials were conducted to study changes in plasma urea and amino nitrogen of lambs fed different nitrogen sources. In the first trial, zein, zein and urea, or urea were fed as the only dietary nitrogen sources. Nitrogen balance data indicated the superiority of the zein–urea ration. Plasma amino acid concentrations were lower at 4 h after feeding than just before feeding. The concentration of total plasma amino acids was greatest when zein was fed and least when the zein–urea ration was fed. Lysine injections into the systemic blood caused a steady decline in total amino acid concentration up to 60 min after injection when zein was fed. Increases in total concentrations were noted after injection when urea had been fed. Intermediate values resulted in lambs fed the zein–urea ration. Lysine appeared to be the limiting amino acid required for maximum tissue protein synthesis when zein was fed. In the second trial, zein, purified soy protein, urea plus sulfur, and urea without sulfur were fed. Plasma collected from lambs fed zein contained less urea nitrogen at every collection period than those fed the other three nitrogen sources. Urea nitrogen decreased from time of feeding to 4 h after feeding zein and soy but increased after feeding both urea rations. Plasma amino nitrogen decreased from time of feeding to 4 h after feeding all rations. Neither urea nitrogen nor amino nitrogen was affected by intravenous amino acid injections.

Effect of Soybean Meal, Raw Soybeans, Corn Gluten Feed, and Urea on the Concentration of Rumen Fluid Components at Intervals After Feeding

Trials utilizing three fistulated steers, in two Latin-square designed experiments, were conducted with five rations equal in digestible protein and containing cottonseed hulls, plus one of the following protein supplements: soybean meal, raw soybeans, corn gluten feed, urea, or urea + soybean meal.In the first experiment, soybean meal, raw soybeans, and corn gluten feed were fed. The corn gluten feed ration was associated with the highest concentrations of total nitrogen (N) and protein N in the rumen fluid; the ration of raw soybeans was associated with the lowest concentrations; and the soybean meal ration with intermediate concentrations. Concentrations of ammonia-N were highest with soybean meal and the lowest with raw soybeans. Total volatile fatty acids (VFA) were similar for soybean meal and corn gluten feed.Soybean meal, urea, and urea + soybean meal were fed in the second experiment. The soybean meal ration was associated with the highest concentrations of total N and protein N; the urea ration with the lowest concentrations; and the urea + soybean meal ration with intermediate concentrations. Concentrations of ammonia-N were highest with urea and lowest with soybean meal. The urea ration was associated with a significantly lower (P<0.01) total VFA concentration and more alkaline pH.

Ammonia Anabolism in Ruminants

Ruminal concentrations of ammonia, alpha-ketoglutaric acid, glutamic acid, and glutamine were determined in two feeding periods (alfalfa pellet only and alfalfa pellet + urea) by using fistulated Corriedal sheep. By addition of urea, the ammonia concentration exhibited significant increases. Glutamic acid decreased in contrast to glutamine in concentration, but the differences between the rations were not significant. In the urea ration period, alphaketoglutaric acid decreased but the differences were not significant. Urea increased plasma glutamine and amino-nitrogen increased significantly, whereas plasma ammonia did not.Nicotinamide adenine dinucleotide (NAD)-linked glutamic acid dehydrogenase (GAD) activity was demonstrated in the rumen mucosa and also in the mucosa of the reticulum and omasum. The NAD-linked GAD activity was also demonstrated by rumen protozoa and bacteria.Glutamine was hydrolyzed by the rumen mucosal homogenate to liberate ammonia. The cell free preparation of the rumen protozoa-rich fraction or bacteria also produced ammonia from glutamine.At high rumen ammonia concentrations, ammonia was incorporated into glutamic acid by reduction of alpha-ketoglutaric acid; furthermore, a part of the glutamic acid entered into the circulation through the rumen wall after it was converted to glutamine. These synthetic reactions should be carried out in the stomach mucosa and the rumen microorganism.

Influence of Dietary Nitrogen on Nitrogen Metabolism in the Rumen1,2

Summary In vivo trials, utilizing four fistulated steers in a Latin-square design, were conducted with four rations: casein + basal, urea + basal, soybean meal + basal, and cottonseed hulls (basal). Nitrogenous constituents, volatile fatty acids (VFA), and pH values were determined on rumen liquor taken at various intervals after feeding. Levels of urea nitrogen were determined on the jugular blood. The concentration of ammonia present in the rumen over a 12-hr period from the urea or casein ration was significantly higher (P Total VFA were influenced by nitrogen substrate. The casein ration was associated with greater quantities of propionic, butyric, and valeric acids than that observed when the other rations were fed, whereas the urea ration was associated with the highest quantity of acetic acid.

The Utilization of Dicyandiamide and Urea by Lactating Dairy Cows1

Twenty-four cows were used in a lactation study to evaluate soybean oil meal, urea and dicyandiamide as nitrogen sources in low-protein concentrate mixtures. Each nitrogen source supplied approximately one-third of the nitrogen in the concentrate mixture. All cows were limited to a protein inake of 90 to 100% of Morrison's minimum protein standards. A medium-quality timothy hay was fed as the sole roughage. No significant differences in milk production were observed on a lactation basis or during a comparison period of 196-days in length beginning on the 30th day of lactation. The average daily milk yields during this period were 24.4, 22.3 and 22.2 lb. per cow daily for the soybean oil meal, urea and dicyandiamide rations, respectively. Significant differences were observed between rations in respect to body weight losses and blood and milk urea nitrogen levels. During the 196-day period the cows fed the ration containing soybean oil meal averaged 3 lb. gain in weight, whereas the cows in the urea group lost 28 lb. and those fed the dicyandiamide ration lost 86 lb. The difference between the soybean oil meal and dicyandiamide rations was highly significant. Cows fed the soybean oil meal and urea rations had significantly higher blood and milk urea nitrogen values than cows fed the dicyandiamide ration. No significant differences in coefficients of apparent digestibility were observed between the rations, but coefficients of all nutrients with the exception of ether extract were lower for the dicyandiamide ration than the other two rations. Data obtained in this study show that the non-protein nitrogen compound, dicyandiamide, was not used efficiently by dairy cows. Studies are in progress to study this problem further.

The Utilization of Urea Nitrogen by Young Dairy Calves1

Thirty-six, 2-day-old male and female calves (18 Jerseys and 18 Holsteins) were raised to 86 days of age on a limited milk-hay-starter system to study the value of urea as a source of nitrogen for young dairy calves. Three experimental starters were used: Starter 1 (low protein) 6.7% protein; starter 2 (urea supplement) 15.1% protein equivalent; and starter 3 (conventional-protein supplement) 15.2% protein. Urea supplied 54.2% of the nitrogen in starter 2. All groups of calves grew at comparable rates for the first 6 weeks during which time whole milk was being fed. When whole milk feeding was discontinued, the urea-supplemented and conventional-protein groups grew at a significantly faster rate than the low-protein group. These two groups consumed significantly more feed and had significantly higher feed efficiency values than the low-protein group. Differences between the conventional protein group and the urea-supplemented group in average daily gain, starter consumption or pounds of feed required per pound of gain, were not significant. Calves on the low-protein ration digested a significantly smaller percentage of protein and crude fiber and retained less nitrogen than either of the other two groups. Calves on the urea ration digested a lower percentage of crude fiber than those on the conventional protein ration. The results show that a portion of the nitrogen requirements of the young calf can be supplied in the form of urea. Cud inoculation of calves had no value as measured by growth, feed consumption, apparent digestibility or nitrogen retention.

Value of Added Methionine in Low-Protein and Urea Rations for Lambs

Value of Added Methionine in Low-Protein and Urea Rations for Lambs

The Comparative Value of Urea and Linseed Meal for Milk Production

Summary 1. Twenty-four Holstein cows were involved in a study of the possibility of substituting urea nitrogen for linseed oil meal nitrogen in milk production. Fifteen of the cows completed a lactation on each of the basal, urea, and the linseed meal rations. Six of the cows were involved in a study of the effect of corn molasses on urea utilization. Each completed a lactation on a urea, a urea-molasses, and a urea ration. 2. On the basal ration the protein level in the concentrate mixture was about 10 per cent. With the added urea or linseed meal it was 18 per cent protein equivalent. Timothy hay and corn silage constituted the roughage. 3. In milk production some cows led on the linseed meal ration while others led on urea with average differences favoring linseed meal in too small a degree to be statistically significant. On the basal ration, with its lower protein content, less milk was generally produced than on either of the other two rations and the cows failed to keep up their live weight as well as on either the linseed meal or urea rations. It appears that with this species and a suitable ration in respect to carbohydrate content, urea can function as a source of nitrogen as effectively as can oil meal. 4. In respect to weight of calves and breeding history, one ration appeared as efficient as the other. 5. The composition of the milk, the flavor of the milk, and the composition of the blood were not different on the two rations. 6. There was no sustained and positive evidence that molasses feeding on a grain ration improved the utilization of urea. With the starches of the grains available, sugar is rapidly produced in the rumen and serves as a suitable substrate for the organisms. 7. Urea (46 per cent nitrogen) should not be fed at a rate greater than about 1 per cent of the dry matter of the ration or 3 per cent of the concentrate mixture. In dairy sections where hay, silage, and home grown grains are available, a suitable nitrogen level in the concentrate mixture can be secured by the addition of 3 pounds of urea to 97 pounds of the grain mixture.