Effects of Adding Coated Urea on in vitro Gas Production of Dairy Cow

Published by Oriental Scientific Publishing Company © 2018 This is an Open Access article licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License (https://creativecommons.org/licenses/by-nc-sa/4.0/ ), which permits unrestricted Non Commercial use, distribution and reproduction in any medium, provided the original work is properly cited. Effects of Adding Coated Urea on in vitro Gas Production of Dairy Cow

Urea is a small organic compound that is very rich in N (44.96%N) that is used to supply degradable intake protein (DIP) to ruminants, which is cost-saving as compared with true protein feeds (Pfeffer et  ).However, the amount of urea that can be used is limited because of the rapid hydrolysis to ammonia (NH 3 ) in the rumen (Galo et al. 2003;Golombeski et al. 2006).Urea is broken down to ammonia in the rumen under the action of bacterial urease (Satter and Slyter, 1974).Microorganisms in the rumen are able to utilize the resulting ammonia to form amino acids which then become available to the host when microbial bodies are digested and absorbed post ruminally (Loosli et al., 1949).
The reasons for using urea over other sources of DIP is that urea N is cheaper on a per N basis than any other feedstuff and transportation and storage are cheaper and easier due to the concentrated nature of urea (McPherson and Witt, 1968).However, urea is used rather inefficiently by ruminants compared with other sources that contain true protein (Broderick et al., 2009), and this is due to the fact that the rate at which urea is degraded in the rumen is more rapid than the rate of utilization of the resulting ammonia by rumen bacteria leading to ruminal accumulation and absorption of ammonia and subsequent excretion of urea in the urine (Golombeski et al., 2006;Highstreet et al., 2010).Therefore utilizing urea as a DIP source may lead to excessive excretion of N in the urine.Nitrogen excretion from cattle operations has become a matter of increasing public concern over the last decade (VandeHaar and St-Pierre, 2006) and therefore reducing N excretion from cattle operations has become an increasing priority for ruminant nutritionists.One strategy for improving the utilization of urea by ruminants is to more closely time the fermentation of energy and the availability of ammonia in the rumen (Johnson, 1976).This may be done by increasing the degradability of the carbohydrates in the diet, or alternatively, by reducing the degradation rate of urea.A number of slow release urea products have been developed for this purpose (Deyoe et al., 1968;Fonnesbeck et al., 1975;Owens et al., 1980).Therefore, the objectives of this study was to develop Paraffin-sulfur Coated Urea and determine this Effects on in vitro gas production of dairy cows.

Materials and Method
Coating urea in rotary drum: A rotary drum coater was used to coat the urea particles.The rotary drum coater was made from stainless steel and was 50 cm in diameter.Urea granules with a nitrogen content of 46%, was previously sieved to 1 mm in diameter were weighed and fed into the rotary drum rotating at 12 rpm.The materials selected as coating mixture were paraffin and sulfur15:1.Coating mixture was frequently applied onto the surface of the tumbling urea.Coated particles were collected after 20 min for analysis.(international patent number: A01K5/00, inventor: Mitra Mazinani) Evaluate the kinetics of NH3-N release: NH 3 -N release of each Optigen and PSCU were tested in sex liquid phase included (distilled water, TCA (Ph = 6.2), buffer solution, buffered rumen fluid, Free cell rumen fluid (centrifugation at 7000 rpm), Free cell buffered rumen fluid).Each of the tow N-sources was isonitrogenous (equivalent 20mg urea) and added to a 100-ml glass syringe.Ruminal fluid was obtained from three ruminallyfistulated Holstein cows fed a similar SBM basal diet.Then 30 ml of solution (consisting distilled water, TCA, buffer solution, buffered rumen fluid, Free cell rumen fluid or Free cell buffered rumen fluid) were pipette into each syringe followed by incubation in a water bath at 39°C.Three syringes for each treatment diet were incubated.At 0, 30 min and 2, 4 and 6 h time points, the syringes were taken out and Residual solid part was taken for determination of NH3-N release using the Kjeldahl N methods (AOAC, 2005).
In vitro gas production: To determine the gas production of each N-Sources (four N-Sources in triplicate) was tested in 4 different feed mixtures (straw + 3% N-Sources, barley flour + 3% N-Sources, barley flour + molasses as additives + 3% N-Sources, a dairy ration formulated to + 3% N-Sources), Each of the N-sources was isonitrogenous (equivalent 18 mg urea).Rumen fluid was obtained from two fistulated dairy cows fed twice daily with a diet containing forage (60%) and concentrate (40%).Equal volumes of ruminal fluid from each cow collected 2 h before the morning feeding squeized through four layers and mixed with McDougall (1948) buffer pre warmed to 39° C. The inoculums was dispensed (20 mL) per syringe into 100 mL serum syringe (containing of 200 mg sample per vial) which had been warmed to 39° C and flushed with oxygen free CO2.The syringes were sealed immediately after loading and were gently mixed and then mixed three times every 3h.Syringes for each time point, as well as blanks (containing no substrate), were prepared in triplicate.Triplicate syringes were removed after 2, 4, 6, 8, 10, 12, 16, 24, 36, 48, 72 and 96 h of incubation.The gas production was recorded at 2, 4, 6, 8, 12, 18, 24, 48, 72 and 96 h of incubation.
Cumulative gas production data were fitted to the model of Orskov and McDonald (1979).P=a+b(1-e"ct) that a=The gas production from the immediately soluble fraction (mL), b=The gas production from the insoluble fraction (mL), c=The gas production rate constant for the insoluble fraction (b), t=The incubation time (h) and P=The gas production at the time t.
Laboratory Analyses: CP analyzed with the Kjeldahl N methods (AOAC, 2005) at the Ferdowsi University of Mashhad and for ADF, NDF, and ash (AOAC, 2005).
Calculations and Statistical Analysis: Data were analyzed as a completely randomized design using a general linear model (GLM) procedure of SAS, with Duncan's multiple range test used for the comparison of means.

result and discussion
According to figure 1, proportion of primary nitrogen to secondary nitrogen in the PSCU after 360 minutes of exposure to liquid was %48.26 ,compared to %72.19 for optigen.The residual nitrogen at all times except 10 minutes had the significant difference, and PSCU degradation Rate was higher.Result of NH3-N release of Optigen and PSCU in sex liquid phase showed in figure 2.
Based on Figure 2, the NH3-N release of Optigen and PSCU in all liquid phases except buffered rumen fluid Freicell was significantly different (P<005).The difference in the residual nitrogen under the effect of different liquid phases showed Optigen had greater NH3-N release in acidic conditions, while PSCU in the acidic  condition and effect of rumen microorganisms increased react and release.In both experiments have not brought up the results of urea culture as a source of urea was quick degradable (100% solution) and as soon as enter in any liquid phase, immediately dissolved (in less than 2 minutes).DiLorenzo and DiCostanzo (2007) evaluate the kinetics of NH 3 -N release in bath culture.they showed at 6 h, deamination from SBM protein begins to be significant, as NH 3 -N accumulates relative to the Blank (p=0.02).from 8 to 24 h, Urea led to greatest (P<005) NH 3 -N release, and greater (P<001) NH3-N release when compared to that elicited by NTS (Balchem Encapsulates, New Hampton, NY) at all times.From 4 to 24 h, biuret had the lowest (P<005) NH 3 -N concentrations of all NPN source, this could be do to a reduced biruetase activity in the rumen since the rumen fluid source steer was not adapted to biuret.Nitrogen utilization by rumen microorganisms can be reflected by ruminal ammonia-N concentration (Hungate, 1966).Prokop and Klopfenstein (1977), found that slow-release urea (combination of urea and formaldehyde) could decrease ruminal ammonia-N concentration by 25.3% compared to urea.A similar result was found in the report of Galo (2003), in which urea release from a polymer-coated urea was 83% as extensive as uncoated urea after 1 h incubation with distilled water.Cass and Richardson (1994) made a comparison in an in vitro study and observed that a urea-calcium combination produced slower ammonia nitrogen release rate than regular urea.Ammonia-N concentrations began to increase at 8 h for the FGU diet, which indicates that bacterial autolysis may occur.Based on this results, urea is often degraded rapidly in the rumen by the action of urease and the resulting ammonia supply may exceed the capacity of rumen bacteria to assimilate it into amino acids (Huber and Kung, 1981).This  NS: not significant rapid release of ammonia may result in inefficient N utilization in the rumen.Therefore slow-release urea improve ammonia assimilation in the rumen.
Gas Production: results showed the cumulative gas production (96 hours) influenced by diets and N-source treatments was different, which was higher gas production in formulated TMR diets for dairy cow and least gas production in wheat straw.The result indicated that Optigen (90.82) and then PSCU (90.81) the highest gas producer in the formulated TMR diets for dairy cow and the canola meal (69.04) and urea (69.43) had the least gas production in wheat straw (P<005) (table 2).Since the in vitro gas production technique has been used as a measurement of ruminal degradation of feed (Menke and Steingass 1988;Poungchompu et al. 2009) or hay (Karabulut et al. 2007), high gas production indicated high digestibility of substrates.In the current study, it was found that slow-release urea treatments had higher gas production.That was agree to other researches.

conclusions
In this trial Optigen and PSCU were used as slow release urea.Rate of NH3-N release in Optigen as shown in figure 1,was %72.19 after 6 hours in bath culture It can be concluded, according to time that each ingredient remain in gastrointestinal tract, a large part of Optigen without being used, be excreted.PSCU had faster release rate and after 6 hours, NH3-N remaining was 48.26 percent.As a result, degradation rate should be considered as indicators to identify the sources of slow release urea.
In conclusion, final goal in dairy farms is maintained milk production and animal health.These experiments demonstrate that SRU can be utilized as an N supplement to modulate the appearance of N in the rumen and can provide equal performance to urea supplements without the potential hazards associated with feed-grade urea, and decrease feed cost and milk production price.

Fig. 1 .Fig. 2 .
Fig. 1.The percentage of nitrogen remaining in optigen and Coated urea following liquid phase effect removal

table 2 .
Gas production in dietary samples containing different nitrogen sources row with different superscripts differ(P<0.05).