Evaluation of Beef Cattle Range Supplements Containing Urea and Biuret

Transcription

1 University f Nebraska - Lincln DigitalCmmns@University f Nebraska - Lincln Panhandle Research and Extensin Center Agricultural Research Divisin f IANR 176 Evaluatin f Beef Cattle Range Supplements Cntaining Urea and Biuret Ivan G. Rush Panhandle Experiment Statin, irush1@unl.edu R. R. Jhnsn University f Tennessee Rbert Ttusek Oklahma State University Fllw this and additinal wrks at: Part f the Agriculture Cmmns Rush, Ivan G.; Jhnsn, R. R.; and Ttusek, Rbert, "Evaluatin f Beef Cattle Range Supplements Cntaining Urea and Biuret" (176). Panhandle Research and Extensin Center This Article is brught t yu fr free and pen access by the Agricultural Research Divisin f IANR at DigitalCmmns@University f Nebraska - Lincln. It has been accepted fr inclusin in Panhandle Research and Extensin Center by an authrized administratr f DigitalCmmns@University f Nebraska - Lincln.

2 EVALUATION OF BEEF CATTLE RANGE SUPPLEMENTS CONTAINING UREA AND BIURET 1,2 Ivan G. Rush 3, R. R. Jhnsn 4 and Rbert Ttusek s Oklabma Agricultural Experiment Statin, Stillwater SUMMARY Tw winter trials were cnducted with 304 lactating range cws n dry grass t evaluate nn-prtein-nitrgen (NPN) in 30% prtein supplements cntaining biuret (pure and feed grade), urea and extruded grain-urea. The NPN surces cntributed ne-half f the supplemental nitrgen with natural 15 and 30% prtein supplements serving as negative and psitive cntrls. Winter weight lss f cws was greater (P~.02) n the negative than n the psitive cntrl in bth trials. The apparent utilizatin f all NPN surces was lw and the utilizatin f urea and extruded grain-urea was less than pure r feed grade biuret. Rumen biuretlytic activity was apparent within 6 days and reached and maintained a high level f activity 20 days after the initiatin f feeding biuret, even with intermittent supplementatin. Apparent value f NPN supplements was slightly imprved with 40% dehydrated alfalfa but nt with methinine-hydrxy-analgue (MHA). Palatability f supplements was lwered by urea and especially 1 Jurnal Article 2814 f the Agricultural Experiment Statin, Oklahma State University, Stillwater. 2The authrs express appreciatin t R. K. Jhnsn and J. V. Whiteman fr assistance in statistical analysis and Bill Sharp and Ray Heldermn fr care f experimental animals. Grateful acknwledgement is als expressed t Dw Chemical, Midland, Michigan, fr feed grade biuret and partial financial supprt; E. I. dupnt de Nemurs and Cmpany, Wilmingtn, Delaware, fr a surce f methinine-hydrxy-analgue and partial financial supprt; Far-Mar-C., Inc., Hutchinsn, Kansas, fr a surce f extruded ureagrain and partial financial supprt; Nipak, Pryr, Oklahma fr urea and pure biuret, and Triple "F" Feeds, Des Mines, Iwa fr a surce f extruded urea-grain. 3Presently District Extensin Livestck Specialist, Panhandle Experiment Statin, Scttsbluff, Nebraska. 4 Presently Head, Animal Science Department, University f Tennessee, Knxville S Department f Animal Sciences and Industry, Oklahma State University, Stillwater by MHA and extruded grain-urea. In a third trial with yearling heifers fed prairie hay, gains were similar n natural prtein and supplements cntaining urea r extruded grain-urea t prvide ne-half f the nitrgen. When the heifers were fed the same supplements but lw quality winter harvested range grass, NPN utilizatin appeared t be lw. (Key Wrds: Urea, Biuret, MHA, Alfalfa, Wintering Cws.) INTRODUCTION Urea is the mst cmmn NPN surce used in range supplements. Because urea is rapidly hydrlyzed, much f the ammnia prduced in excess f available energy supplied by lw quality frage is lst (Blmfield et al., 160) and animal perfrmance is ften lwer than desired. Utilizatin f NPN in lw quality rughage ratins may pssibly be increased with biuret (Jhnsn and Clemens, 173) r extruded grain-urea (Helmer et al., 170) t prvide slwer ammnia release. Labratry studies indicate rumen micrflra must adapt t biuret befre develping biuretlytic activity (Clemens and Jhnsn, 173; Gilchrist et al., 168; Jhnsn and Clemens, 173). Apparent utilizatin f urea has been imprved with dehydrated alfalfa (Karr et al., 165). Milk prductin was imprved by MHA fed t dairy cws (Griel et al., 168) and beef cws (Varner et al., 173) with ratins f all natural prtein. The purpse f this research was t determine (1) the apparent utilizatin f biuret (pure and feed grade), urea and extruded grain-urea in range cattle supplements, (2) the value f MHA and a high level f dehydrated alfalfa in range cattle supplements cntaining high levels f biuret and urea, and (3) the rate and extent f biuret adaptatin by cattle under range cnditins. 127 JOURNAL OF ANIMAL SCIENCE, Vl. 42, N. 5, 176

3 128 RUSH, JOHNSON AND TOTUSEK EXPERIMENTAL PROCEDURE Trial 1. Trial 1 was cnducted during the winter n the Lake Carl Blackwell Range in Central Oklahma n dry native range grass. Predminant frages are f the tallgrass prairie type with climax species cnsisting f little bluestem (Andrpgn scrparius), big bluestem (Andrpgn gerardi), Indian grass (Srghastrum nutans), and switch grass (Panicum virgatum). Dry range grass was abundant; prairie hay was fed nly several days when ice r snw cvered the grass. A ttal f 140 experimental cws included 3 mature Herefrd cws, 43 mature Angus cws and 58 first-calf Herefrd heifers. Mature cws calved either shrtly befre r after the trial started while first-calf Herefrd heifers calved during early fall befre the experiment started. Cws were randmly assigned within breed and age t nine supplement treatments. The wintering trial was initiated December 27 and was terminated March 27, an 88-day perid. Ingredient makeup f supplements is shwn in table 1. Supplements 1, 2, 3, 4, 5, 6A, 7A, 8 and were fed in trial 1. Supplements 1 and 2, frmulated t cntain 15 and 30% CP, cntained all natural prtein and served as negative and psitive cntrls, respectively. The remaining seven supplements were frmulated t cntain 30% CP (0% DM basis), with ne-half f the CP frm NPN surces. All supplements were frmulated t cntain 1.25% phsphrus,.5% calcium and a nitrgen:sulphur rati f 14:1. MHA was added (supplements 6A, 7A) t prvide 10 and 20 g per head daily befre and after calving, respectively. Supplements were prcessed int.8 mm (88 in.) pellets. Cws, allwed t graze in a cmmn pasture, were gathered t a central feeding area in the mrning 6 days each week, placed in m stalls and individually fed their supplement. Twenty minutes were allwed fr cnsumptin f supplements; feed refusals were recrded. Supplement ffered per cw each feeding was.7 and 1.5 kg fr mature cws and 1.06 and 2.12 kg fr first-calf heifers, befre and after calving, respectively. Severe weather prevented feeding f supplements n 6 f the 88 days. Cws and calves were weighed after being gathered at daybreak and withheld frm feed and water fr apprximately 6 hurs. Calves were weighed shrtly after birth. Cnditin lss f cws was estimated by scring the cws fr cnditin at the initiatin and cnclu- sin f the trial. Scres f 1 t were used, with 1 being the thinnest and the fattest. Since the number f mature cws which calved previus t the trial was disprprtinate amng treatments, initial weight f cws that calved befre the trial was adjusted t a pregnant weight basis. The regressin equatin used t crrect initial cw weight was (Ewing et al., 166 and unpublished data): Adjusted initial weight (kg) Actual initial weight + (calf birth wt 1.67) Calves ut f mature cws were sired by Charlais bulls while calves ut f first-calf heifers were sired by Herefrd bulls. Weaning weights were adjusted t a 205-day, steer basis; adjusted 205-day weights f heifers were multiplied by Dehydrated alfalfa pellets (alfalfa, aerial pt. dehy grnd, mn.17 prtein (1) ) were prvided fr calves in a creep during the latter part f the trial. Data were analyzed by least squares regressin analysis with the F-test used t test fr significant treatment differences, and students' t-test fr differences between any tw treatments. Trial 2. Trial 2 was cnducted at the same lcatin as trial i during the fllwing winter. Cws were managed in the same manner, including the supplementatin f cws in individual stalls. A ttal f 164 experimental cws cnsisted f 81 Herefrds, 44 Angus and 3 Angus x Hlstein crssbreds. They calved either shrtly befre r after the trial started. Initial weights f cws that calved befre the experiment started were adjusted t a pregnant basis as in trial 1. Supplements were frmulated as in trial 1 but thse cntaining MHA (6A and 7A) were replaced. In supplement 6B the NPN fractin was a mixture f urea (50%) and biuret (50%) while in supplement 7B urea, present in an extruded grain-urea mixture, cntributed nehalf f the crude prtein. Amunts f daily supplement ffered per cw were 1.05 and 2.12 kg fr Herefrd and Angus cws and 1.5 and 2.65 kg fr crssbred cws, befre and after calving, respectively. The weather during trial 2 was mre severe and prevented the feeding f supplements 22 days f the 112-day feeding trial. When supplements were nt fed, prairie hay was fed daily. In additin, the 30% natural prtein supplement was grup-fed at the rate f

4 UREA AND BIURET FOR RANGE BEEF CATTLE kg per head per day when the experimental supplements had nt been fed fr 3 cnsecutive days. Cws were weighed after vernight cnfinen'aent in crrals withut feed r water fr 12 hurs. Statistical analysis f the data was cnducted as in trial 1, except analysis f cvariance was used t adjust the initial weight f the Herefrd cws t an equal basis (Snedecr and Cchran, 167). Since trial treatment, breed f cw treatment and age f cw x treatment interactins were nt significant (P>.10), t~'eatments 1, 2, 3, 4, 5, 8 and were pled fr trials 1 and 2, and the pled data were analyzed in the same manner as in each individual trial. Biuret Adaptatin Trials. Nine mature steers, equipped with rumen cannulas, were used t measure the rate and extent f adaptatin f rumen micrrganisms t biuret under range cnditins. The steers were allwed t graze in the same pasture as the cws during the first 74 days f trial 2, and were fed and managed in the same manner as the cws. They were randmly alltted t supplemental treatments 2, 4 and 8 (table 1) and were individually fed 1.5 kg f the supplement per day. Rumen samples frm each steer were btained n days 0, 4, 6, 17, 20, 28, 34, 4 and 74 f the experiment. Biuretlytic activity f the rumen cntents was determined by prcedures described by Jhnsn and Clemens (173). These data were analyzed with analysis f variance with the F test utilized t test significant differences. Differences between means were determined by the LSD methd (Snedecr and Cchran, 167). Trial 3. A grwth trial was cnducted in drylt during a 3-day perid during the summer t cmpare the apparent utilizatin f supplemental nitrgen frm natural prtein, urea and urea in an extruded grain-urea mixture (supplements 2, 5 and 10, table 1). A ttal f 27 yearling heifers (nine Herefrd and 18 Herefrd Angus-Hlstein) was blcked accrding t breed and weight and randmly assigned t three treatment grups f nine heifers each. Nine heifers (three frm each treatment) were maintained in each f three lts. Tallgrass prairie frage was fed ad libitum. Hay (native plants, mid west, hay, s-c, mid-blm (1) ) fr the first phase (44 days) had been cut in mid-july and was f mderate quality. Hay (native plants, mid west, hay, s-c, ver ripe (1) ) fr the secnd phase (44 days) had been cut in early April and resembled late-winter dry range grass. Crude prtein cntent f the tw hays was 5.0 and 3.%, respectively. Supplements were fed in individual stalls twice daily at the rate f 454 g per feeding (08 g/day). Heifers were weighed after a 14-hr shrink withut feed r water. Change in cnditin was estimated in the same manner as in trials 1 and 2. Hay intake f each treatment grup was measured fr 5 days at the end f each phase Of the experiment. During this time supplemental feeding cntinued as befre, but each treatment grup was maintained in a separate lt which allwed daily measurement f hay intake. Analysis f variance was used t test fr significance and the LSD multiple range test was used t test fr significant differences between treatment means (Snedecr and Cchran, 167). RESULTS AND DISCUSSION Treatments 6 and 7 were different in trials 1 and 2 and will be discussed within each trial; the results and discussin f treatments 1, 2, 3, 4, 5, 8 and will be based n the pled data f trials 1 and 2. Trial I, Effects f MHA. The results f trial 1 are shwn in table 2. Cws receiving the negative cntrl (15% natural prtein)supplement lst mre weight (P~,.02) than cws cnsuming the psitive cntrl (30% natural prtein) indicating that prtein was deficient in the negative cntrl and prviding validity fr the experimental design fr evaluating supplements. Additin f MHA lwered palatability and cnsequently intake f supplements. Effects f MHA n palatability were prbably mre prnunced in this trial than in previus research (Chandler et al., 170; Lfgreen, 170; Plan et al., 170) because f the high levels f NPN and the higher percentage f MHA in the cncentrate prtin. Lack f cmpetitin amng individually fed cws may have cntributed t lw intake f supplements cntaining MHA and/r urea, since lactating cws grazing similar frage were grup-fed the urea cntaining supplement with n intake prblems (Rush and Ttusek, 173). The effect f MHA in urea r biuret supplements n cw weight lss was small. Weight lss f cws receiving biuret, biuret + MHA, urea and urea + MHA was nt different (P>.05); hwever, the cws cnsuming the supplement

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9 1304 RUSH, JOHNSON AND TOTUSEK cntaining urea + MHA had the largest weight lss. Analysis f cvariance (Snedecr and Cchran, 167) was used t crrect cw weight lss means t differences in supplement intake. Adjusted weight lsses (kilgrams r percent) f cws receiving biuret, biuret + MHA and urea were nt different (P~.10), but they were greater (P~.05) than weight lss f cws receiving urea + MHA. Treatment did nt affect cnditin change f cws (P~.6) r summer cw gain (P~.SS). Since treatment did nt affect daily gain f calves frm birth t end f treatment (P~.75) and adjusted weaning weight (P~-.7), milk prductin f cws was apparently nt affected by MHA. This lack f lactatin respnse t MHA is in cntrast t results with beef cws (Varner et al., 173) and dairy cws (Plan et al., 170). These wrkers cmbined MHA with natural prtein, but MHA significantly increased bacterial nitrgen and cellulse digestin, and lwered ammnia levels with urea in vitr (Gil et al,, 173). Trial 2, Effects f Biuret + Urea and Extruded Grain-Urea. Supplements 6B and 7B in trial 2 cntained urea + biuret (equal nitrgen frm each) and an extruded grain-urea mixture, respectively. The results f trial 2 are shwn in table 3. As in trial 1 cws n the negative cntrl lst mre (P~.01) winter weight than thse n the psitive cntrl A cmbinatin f urea + biuret was almst as palatable as biuret alne (4.2% f the supplement refused), but weight lss f cws receiving urea + biuret was nt different (P~.05) frm that f cws receiving biuret r urea alne. Weight lsses f cws cnsuming extruded grain-urea and ther NPN supplements were nt different (P>.05). The large weight lss f cws n extruded grain-urea was cnceivably a reflectin f lw intake f the less palatable supplement. Hwever, crrecting weight lss means fr supplement intake indicated little difference between urea and extruded grain-urea; utilizatin f urea was apparently lw in bth supplements and nt imprved by extruding with grain. Treatment effects (urea, biuret, extruded grainturea) n cnditin lss f the cws were similar t thse bserved fr cw weight lss. Treatment did nt affect daily gain f calves while n treatment (P~.58) r adjusted weaning weight (P~.77). 0 ~ ~d C~ L~e~ r~ v C~ bo L~ ~d ;.d ~A ~d ~a 0 0 u u I- e~ II- I- II '~ :1 A " " AA V,.~... ~+ ~ -~ ~ O e~ g O

10 UREA AND BIURET FOR RANGE BEEF CATTLE 1305 Trials i and 2 Pled. Since a treatment x trial interactin was nt detected (P>.10), treatments cmmn t trials 1 and 2 were pled fr analysis. Results f the pled data are shwn in tables 4 and 5. Cws fed the negative cntrl supplement lst mre winter weight (P~.001) and mre cnditin than thse n the psitive cntrl. Weight and cnditin lss f cws fed NPN supplements were greater (P.05) than fr the cws fed the psitive cntrl. Cws fed biuret lst fewer kilgrams weight (P~.05), less percent weight (P~.07) and tess cnditin (P~.06) than cws fed urea. Cws fed urea refused 10.8% f the supplement and cnsumed.14 kg less than cws fed biuret. Hwever, analysis f cvariance (Snedecr and Cchran, 167) shwed the b and r values were apprximately zer, s n adjustment fr supplement intake was made. The advantage fr biuret may be due t slwer hydrlysis with ammnia release at a rate mre cmparable t the rate f energy release frm the mature frage. The greater apparent utilizatin f biuret is in agreement with Tllett et al. (16) and Raleigh and Turner (168) but in cntrast t results f Clantn (170), Turner and Raleigh (16) and Turner et al. (170). Feed grade biuret was nt different (P>.05) than biuret in any trait measured (P>.50 fr cw winter weight lss). Apparently the cmbinatin f NPN surces in feed grade biuret (including 15% urea) was withut affect. The additin f 40% dehydrated alfalfa t the urea supplement was beneficial in terms f cw weight lss (P~.01), in agreement with Karr et al. (165), Nelsn et al. (157) and Clantn (170). Palatability als appeared t be imprved slightly (6.2 vs 10.8% refusal). The biuret supplement was nt benefited by 40% alfalfa in terms f cw weight lss (P~.4); weight lss n biuret and urea supplements with 40% alfalfa was cmparable. The NPN supplements did nt affect calf daily gain while n treatment (P~.58) r adjusted weaning weight (P~.77). Biuret Adaptatin Trial. The biuretlytic activity bserved in the rumen fluid f steers supplemented with the psitive cntrl, biuret and biuret + alfalfa (40%) is shwn in figure 1. N appreciable activity was apparent n days 0 r 4. By day 6 biuretlytic activity f biuret supplemented steers was greater (P,05) than that f natural prtein steers. Adaptatin was g 3c ~_~ 2c!!... IC f, ~, i 4 z//i/~///~ ~ I Day Of Experiment Figure 1. Biuretlytic a~tivity f steers fed range supplements cntaining natural prtein, biuret and biuret + 40% alfalfa. (Shaded areas indieate days biuret supplements were nt fed). nt lst when biuret supplements were nt fed fr nine cntinuus days after day 7; rumen samples were taken n day 17, 1 day after supplemental feeding was reinitiated. Biuretlyric activity increased t 88% n day 4 althugh the steers were nly supplemented 4 f the preceding 14 days. The biuret steers cntinued well adapted n days 56 and 74 f the trial. Steers supplemented with natural prtein did nt develp appreciable biuretlytic activity and degraded less biuret (P.01) than biuret fed steers frm day 20 t the end f the trial. Biuretlytic activity f steers fed the tw biuret supplements was nt different (P>.10) fr any f the sampling days. This agrees with results f Gilchrist et al. (168) and Jhnsn and Clemens (173). The rate f develpment f biuretlytic activity was faster than reprted previusly (Jhnsn and Clemens, 173), r indicated by nitrgen balance (Hatfield et al., 15; Oltjen et al., 16; Tmlin et al 167). Hwever, Clemens and Jhnsn (173) and Wyatt (173) recently fund marked biuretlytic activity in 3 t 4 days in lambs fed high rughage diets. The lw prtein (3% CP) f the majr prtin f the steers' diet (dry range grass) in this trial may have facilitated the shrt adaptatin perid (Schrder and Gilchrist, 16). Clemens and Jhnsn (173), Jhnsn and Clemens (173) and Schrder and Gilchrist (16) fund a rapid lss (4 days) f biuretlyric activity when biuret was remved frm the diet. Biuretlytic activity was nt lst n day 17 f this trial even thugh supplemental

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12 UREA AND BIURET FOR RANGE BEEF CATTLE 1307 biuret was nt fed f the previus 10 days. Biuret was fed 24 hr prir t sampling, a rather shrt time fr develpment f biuretlytic activity if it were lst the previus days, The high biuretlytic activity (88%) n day 4 als was unexpected due t the previus intermittent and irregular feeding pattern. These data indicate that either cmplete biuretlytic activity was nt lst during the intermittent feeding perid r the rumen micrflra were able t readapt t biuret at a faster rate than reprted by Schrder and Gilchrist (16). Perhaps previusly adapted animals "readapt" faster than animals never previusly fed biuret (Clemens and Jhnsn, 173). These data als prvide supprt fr the apparent utilizatin f sme biuret by cws in trials 1 and 2. Trial 3. Results f trial 3 are shwn in table 6. Weight gain f heifers appeared t be nly slightly affected (P~.18) by nitrgen surce when mderate quality hay was fed; calves that received the all natural prtein supplement had the highest gain. There was a difference (P~.01) in treatments when harvested winter range grass was fed during the secnd phase f the experiment. Heifers cnsuming the natural 30% prtein supplement lst less weight (P~.05) than the heifers receiving the urea cntaining supplements. A treatment phase interactin was nt detected (P>.10) s the tw phases were pled fr statistical analysis; heifers fed the 30% natural supplement gained mre (P.01) than the heifers fed either urea supplement. Gains f heifers fed the tw urea supplements were nt different (P>,40). Heifers fed the natural prtein supplement maintained their cnditin during the trial while the tw urea grups lst in cnditin (P~-.32). Hay intake was nt affected by supplement (P>.50) during either phase f the trial. The extruding f grain with urea apparently failed t increase nitrgen utilizatin frm urea as indicated by bdy weight and cnditin, in agreement with Clantn (170) but in cntrast with results f Tucker and Harbers (172), Tucker et al. (172), Helmer et al. (170) and Owen and Applemen (170). LITERATURE CITED Blmfield, R. A., G. B. Garner and M. E. Muhrer Kinetics f urea metablism in sheep. J. Anita. Sci. 1:1248, (Abstr.). Clantn, D. C Nn-prtein-nitrgen in range supplements. Prc. Texas Nutritin Cnference, 2J~131. Clemens, E. T. and R. R. Jhnsn Biuretlytie activity f rumen micrrganisms as influenced by the frequency f feeding biuret supplement. J. Anita. Sci. 37:1027. Chandler, P. T., C. E. Plan and D. P. Shaw Mel;hinine hydrxy analgue and lipid,metablism in the lactating cw. J. Dairy Sci. 53:376. (Abstr.). Ewing, S. A., Larry Smithsn, Dwight Stephens ~nd Derald McNutt Weight lss patterns f beef cws at calving, Okla. Agr. Exp. Sta. Misc. Pub. 78~64. Gil, L, A., R. L. Shirley and J. E. Mre Effect f methinine hydrxy analg n bacterial prtein synthesis frm urea and glucse, starch r cellulse by rumen micrbes, in vitr. J. Anita. Sci. 37:15. Gilchrtst, F. M. C., E. Ptgieter and J. B. N. Vss The biuretlytic activity f ruminal flra f sheep fed practical ratins cntaining biuret. J. Agr. Sci. 70:157. Grid, L. C., Jr., R. A. Pattn, R. D. McCarthy and P. T, Chandler Milk prductin respnse t feeding methinine hydrxy analgue t lactating dairy cws. J. Dairy Sci. 51 : Hatfield, E. E., U. S. Garrigus, R. M. Frbes, A, L. Neumann and W. Gaither. 15. Biuret--a surce f NPN fr ruminants. J. Anim. Sci. 18:1208. Helmer, L. G., E. E. Bartley and C. W. Deye Feed prcessing VI. Cmparisn f starea, urea and sybean meal as prtein surces fr lactating dairy cws. J. Dairy Sci. 53:883. Jhnsn, R. R. and E. T. Clemens Adaptatin f rumen micrrganisms t biuret as a NPN supplement t lw quality rughage ratin fr cattle and sheep. J. Nutr. 103:44. Karl M. R., U. S. Garfigus, E. E. Hatfield and H. W. Nrtn Factrs affecting the utilizatin f nitrgen frm different surces by lambs. J. Anim. Sei. 24:45. Lfgreen, G. P.!70. Methinine hydrxy analgue and/r sulfur in ratins cntaining urea. Calif. Feeders Day Rep Davis, Califrnia. Nelsn, A. B., M. B. Greeley, I. A. Miller and G. R. Waller Prtein supplements fr wintering beef catde. J. Anita. Sci. 16:1085. (Abstr.). Oltjen, R. R., E. E. Williams, Jr., L. L. Slyter and G. V, Richardsn. 16. Urea versus biuret in a rughage diet fr steers. J. Anita. Sci. 2:816. Owen, F. Y. and R. D. Applemen Value f a gelatinized mil-urea mixture and DEHY-100 (pelleted preparatin) as carriers f urea in lactatin ratins. Prc. XVIII Int. Dairy Cngr. Sidney, Australia. 1E~540. Plan, C. E., P. T. Chandler and C. M. Miller Methinine hydrxy analg: varying levels fr lactating cws. J. Dairy Sci. 53:607. Raleigh, R. J. and H. A. Turner.!68. Biuret and urea in range cattle supplements. Prc. West. Sec. Amer. Sc. Anim. Sci. 1: 301. Rush~ Ivan and Rbert Ttusek, 173. Frequency f feeding urea supplements. J. Anim. Sci. 37:355. (Abstr.). Schrder, H. H. E. and F. M. C. Gilchrist. 16. Adaptatin f vine ruminal flra t biuret. J. Agr.

13 1308 RUSH, JOHNSON AND TOTUSEK Sci. 72:1. Snedecr, G. W. and W. G. Cchran Statistical Methds (6th Ed.). Iwa State University Press, Ames. Tllett, J. T., R. W. Swart, R. M. Iset and J. A. Templetn. 16. Biuret as a surce f nitrgen fr wintering steers. Prc. West. Sec. Amer. Sc. Anita. Sci. 20: 325. Tmlin, D. C., L. E. Harris and J. E. Butcher Biuret digestin in sheep. J. Anita. Sci. 26:31. (Abstr.). Tucker, L. L. and L. H. Harbers Starea, urea and sybean meal as a prtein surce in grwing and finishing cattle ratins. Kan. Agr. Exp. Sta. Bull. 557:43. Tucker, L. L., L. H. Harbers and E. F. Smith Starea, urea and sybean meal cmpared in winter- ing ratins fr cws n bluestem pasture II. Effect n birth and weaning weight f prgeny and rebreeding perfrmance. Kan. Agr. Exp. Sta. Bull. 557:48. Turner, H. A. and R. J. Raleigh. 16. Biuret and urea fr grwing cattle. Prc. West. Sec. Amer. Sc. Anita. Sci. 20:331. Turner, H. A., R. J. Raleigh and R. L. Phillips Energy level and nitrgen surce fr fall calving cws. Prc. West. Sec. Amer. Sc. Anim. Sci. 21:75. Varner, L. W., R. A. Bellws and R. R. Oltjen Supplemental methinine hydrxy analg fr beef cws. J. Anim. Sci. 37:358. (Abstr.). Wyatt, Rger Daniel Factrs affecting biuret adaptatin by rumen micrrganisms in sheep. M. S. Thesis. Oklahma State University, Stillwater.