Influence of supplemental nitrogen source on digestion of nitrogen, dry matter and organic matter and on in vivo rate of ruminal protein degradation

Seven Holstein steers (340 kg) fitted with ruminal, duodenal and ileal cannulae were used to measure the influence of supplemental N source on digestion of dietary crude protein (CP) and on ruminal rates of protein degradation. Diets used were corn-based (isonitrogenous, 12% CP on a dry matter basis, and isocaloric, 80% total digestible nutrients) with urea, soybean meal (SBM), linseed meal (LSM) or corn gluten meal (CGM) as supplemental N. Ruminal ammonia N concentrations were higher (P less than .05) in steers fed LSM than in those fed CGM, but did not differ from those in steers fed urea or SBM (11.7, 6.7, 9.1 and 9.2 mg/100 ml, respectively). Due to the high degradability of urea, ruminal digestion of dietary CP was greater (P less than .05) in steers fed urea than in those fed CGM, but intermediate in steers fed SBM and LSM (58.4, 48.8, 53.1 and 53.9%, respectively). Flow of bacterial nonammonia N to the duodenum was highest (P less than .05) in steers fed SBM or LSM, intermediate (P less than .05) for urea and lowest (P less than .05) for CGM (86.8, 86.1, 76.3 and 65.9 g/d, respectively). Efficiency of bacterial protein synthesis was lowest in steers fed CGM and differed (P less than .05) from SBM (15.6 vs 21.8 g N/kg organic matter truly digested, respectively). Rate of ruminal digestion for SBM-CP differed (P less than .05) from that of CGM-CP but not from that of LSM-CP (17.70, 5.20 and 10.13%/h, respectively). The slow rate of ruminal degradability of CGM resulted in increased amounts of dietary protein reaching the intestinal tract but lower amounts of bacterial protein, thus intestinal protein supply was not appreciably altered.     

Nitrogen utilization and ruminal fermentation in steers fed soybean meal treated with formaldehyde

Four rumen-fistulated steers averaging 400 kg in body weight were used in a 4 X 4 Latin square arrangement with 18-d periods to investigate the effect of treating soybean meal (SBM) with formaldehyde on nitrogen (N) utilization and ruminal fermentation. Experimental diets, on a dry matter basis, consisted of 42% corn silage, 48.5% cracked corn-mineral mixture and 9.5% SBM treated with 0, .3, .6 or .9% formaldehyde by weight. Dry matter and organic matter digestibilities were not affected by treatment. Formaldehyde treatment of SBM resulted in a linear decrease in N digestibility (P less than .005) and urinary N excretion (P less than .01) and a quadratic increase (P less than .05) in N retention. The depression in apparent N digestibility was small when SBM was treated with .3% formaldehyde. This level of formaldehyde treatment also had little effect on in vitro enzymatic hydrolysis of SBM. Ruminal ammonia-N concentrations were lower (P less than .05) in steers fed formaldehyde-treated SBM. Ruminal pH was lower (P less than .05) at 6 and 8 h postfeeding while volatile fatty acid concentrations were higher (P less than .05) at 8 and 12 h postfeeding for steers fed untreated SBM. Propionic acid (mol/100 mol) decreased linearly (P less than .05) with increasing level of formaldehyde treatment. Urea-N concentrations in plasma were decreased (P less than .001) and plasma-free essential amino acid concentrations were increased (P less than .10) by formaldehyde treatment. Ruminal disappearance of N from polyester bags containing the SBM supplements was greatly reduced (P less than .005) by formaldehyde treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protein supplementation of ammoniated roughages. III. Corncobs supplemented with a blood meal-corn gluten meal mixture--steer studies

Two factorial experiments were conducted to investigate site and extent of organic matter (OM) digestion, nitrogenous fractions flowing at the abomasum and rates-of-passage in steers fed 0, 2 or 4 g NH3/100 g dry matter of treated corncobs supplemented with either a corn or a blood meal-corn gluten meal (BM-CGM) supplement. Rumen and total tract OM digestion coefficients were quadratically increased (P less than .05) and dietary N was quadratically increased (P less than .07) due to the main effect of ammonia. The main effect of protein supplement increased (P less than .05) postruminal OM digestibility, nonammonia N and dietary-N flow. Quadratic protein X ammonia interactions were noted for fluid flow, total-N flow, total amino acid flow and ammonia-N flow. Linear protein X ammonia interactions were noted for bacterial-N flow, which appeared to indicate that N utilization of the ammoniated corn-cob was improved by the inclusion of BM-CGM in the diet. Diet dry matter intake, fluid volume, rate of fluid passage, particulate mass and rate of particulate passage in rumen-fistulated steers were unaffected by either main effect. However, rumen fluid pH of steers fed BM-CGM was lower than that from steers fed the corn supplement.     

Effects of supplemental energy and/or degradable intake protein on performance,grazing behavior,intake, digestibility,and fecal and blood indices by beef steers grazed on dormant native tallgrass prairie

To evaluate the effects of balancing total diet degradable intake protein with dietary total digestible nutrients (TDN), we conducted two studies during 2 yr with 100 (302 +/- 8 kg initial BW) mixed-breed yearling steers and 12 ruminally cannulated steers (526 +/- 28 kg). Steers individually received one of four supplements 5 d/wk while grazing dormant native tallgrass prairie. Supplements included: 1) corn and soybean meal, balanced for total diet degradable intake protein in relation to total diet TDN (CRSBM), 2) corn and soybean hulls, equal in supplemental TDN to CRSBM (CORN), 3) soybean meal, equal in supplemental degradable intake protein to CRSBM (SBM), or 4) a cottonseed hull-based control supplement (CONT). At each feeding (5 d/wk), steers consumed 13.6, 13.6, or 4.2 g of dry matter/kg of body weight, or 178 g of DM, respectively, of supplement. Steers fed CRSBM had greater (P < 0.01) average daily gain than cattle fed CORN or SBM. Feeding soybean meal (CRSBM, SBM) resulted in improved (P < 0.01) efficiency of supplement. Grazing time, intensity, and harvesting efficiency were reduced (P < 0.05) by corn supplementation (CRSBM and CORN), whereas the number of grazing bouts per day was increased (P < 0.08). Intake and digestibility of forage organic matter were reduced (P < 0.01) for steers supplemented with corn (CORN and CRSBM) vs cattle not fed corn (SBM and CONT). Total diet digestibility (P < 0.12) and digestible organic matter intake (P < 0.01) were greater for CRSBM-fed steers than for cattle fed either CORN or SBM. Steers fed CRSBM had greater (P < 0.01) fecal nitrogen and serum insulin than cattle fed CORN or SBM. Corn-fed cattle had lesser (P < 0.01) fecal pH and ADF concentrations than steers not consuming grain. Cattle fed supplements with soybean meal (CRSBM and SBM) had greater (P < 0.01) serum urea nitrogen than steers fed supplements without soybean meal (CORN, CONT). Supplemented steers grazing dormant tallgrass prairie had a greater rate of gain, with the greatest response in animal performance occurring when grain supplements were balanced for total diet degradable intake protein in relation to total diet TDN. These results lead us to suggest that grain-supplemented cattle grazing dormant tallgrass prairie require a balance of total diet degradable intake protein in relation to total diet TDN to optimize animal performance.     

Effects of dietary energy level and protein source on site of digestion and duodenal nitrogen and amino acid flows in steers

Six steers (468 kg) with ruminal and duodenal cannulas were fed diets formulated for two levels of energy containing three crude protein (CP) sources in a 6 X 6 Latin square with a 2 X 3 factorial arrangement of treatments. Energy levels were 2.17 and 2.71 Mcal metabolizable energy (ME)/kg dry matter (DM) provided by hay-corn (H) and corn silage-corn (CS) diets, respectively. Soybean mean (SBM), corn gluten meal-urea (CGM) and urea (U) provided 33% of dietary CP in 12% CP diets. Apparent organic matter (OM) digested in the stomach was not affected (P greater than .05) by energy level or CP source, but OM truly digested in the stomach was greater (P less than .05) when steers were fed the CS compared with the H diet. Duodenal flow of non-NH3 N was greater (P less than .05) when steers were fed CS compared with H and when fed SBM or CGM compared with U. Efficiency of bacterial protein synthesis and duodenal bacterial N flow were increased (P less than .05) when steers were fed CS, but non-NH3, nonbacterial N flow to the duodenum was increased (P less than .05) when steers were fed H. When steers were fed CS rather than H, flows (g/d) of bacterial amino acids were greater (P less than .05), but flows of nonbacterial amino acids tended (P less than .08) to be less. Total amino acid flows were not affected (P greater than .05) by energy level. Duodenal flows of total amino acids tended (P less than .06) to be greater when steers were fed CGM compared with SBM or U, due mainly to an increased (P less than .05) flow of nonessential amino acids.     

Effects of dietary energy level and supplemental protein source on performance of growing steers and nutrient digestibility and nitrogen balance in lambs

Four experiments were conducted to evaluate three crude protein (CP) sources (urea, U; soybean meal, SBM; corn gluten meal, CGM) in diets based on corn silage (high energy) or grass hay (low energy). In Exp. 1 and 2, growing steers were fed all combinations of energy and protein source at 10.5 or 12% CP. Steers fed high energy diets or 12% CP had improved (P less than .05) daily gains and feed:gain over 84 d. Protein source had no effect (P greater than .05) on performance except that steers fed U consumed more (P less than .05) feed than those fed CGM. Steers were fed experimental diets to a common weight and switched to an 85% concentrate diet for finishing. During finishing, steers fed low energy diets in the growing period consumed more (P less than .05) feed and had increased (P less than .05) feed:gain compared with those fed high energy diets. Growing lambs were fed the same diets as steers. At 10.5% CP, lambs fed high energy diets had higher (P less than .05) digestibilities of dry matter (DM), organic matter (OM), nitrogen (N) and fiber components, and retained more (P less than .05) N. For lambs on 12% CP, high energy diets had higher (P less than .05) DM and OM digestibilities and lower (P less than .05) N digestibilities. At 12% CP, energy level had no effect (P greater than .05) on N retained. Protein source had no effect (P greater than .05) on N retention. There appeared to be no advantage in supplementing with ruminally undegradable proteins, i.e. CGM, in these experiments.     

Induced non-enzymatic browning of soybean meal. III. Digestibility and efficiency of protein utilization by ruminants of soybean meal treated with xylose or glucose

Trials were conducted to evaluate effects of non-enzymatic browning of soybean meal (SBM) on efficiency of protein utilization and N digestibility. In trial 1, 48 Suffolk-Finnsheep lambs (22 kg) were fed 80 d to evaluate efficiency of protein utilization for growth when supplemental protein was fed as urea (U), commercial SBM (CS), or commercial SBM (pH 8.5, 83% dry matter) containing xylose (3 mol/mol SBM-lysine) and heated 30 min (XTS-30) or 55 min (XTS-55). Diets containing graded levels of N from CS, XTS-30 and XTS-55 were fed. Response criterion was efficiency of protein utilization, plotted as gains of lambs fed test proteins minus gain of lambs fed U vs supplemental test protein fed. Efficiencies of protein utilization were .62, 1.27 and .91 for CS, XTS-30 and XTS-55, respectively. Protein from XTS-30 was used more efficiently (P less than .05) than that from CS. In trial 2, apparent digestibility of N from CS (97%) was higher (P less than .01) than XTS-30 (77%) and XTS-55 (82%) by Suffolk-Finnsheep lambs (27 kg). In trial 3, 60 mixed-breed steers (218 kg) were fed individually for 105 d to evaluate glucose as a reducing sugar. Glucose-treated SBM (GTS) was prepared by mixing glucose (3 mol/mol SBM lysine) with SBM, adjusting pH and dry matter content to 8.5 and 80%, respectively, and heating at 150 C for 60 min. Supplemental N sources were U, CS, GTS and a 50:50 mixture (protein basis) of corn gluten meal and blood meal (CGM/BM).(ABSTRACT TRUNCATED AT 250 WORDS)     

Alternate day supplementation of corn stalk diets with soybean meal or corn gluten meal fed to ruminants.

Four experiments were conducted to determine the effect of adding corn gluten mean (CGM) or soybean meal (SBM) at 24- or 48-h intervals to diets based on corn stalks. In each experiment corn stalks was the primary diet ingredient fed to wethers or steers. Monensin was also fed to determine whether its effects on ruminal fermentation would improve the efficiency of N utilization under these conditions. Evaluation criteria included ruminal fermentation characteristics, DM intake and utilization, N balance in sheep, and steer feedlot performance. Ruminal ammonia nitrogen (NH3 N) concentrations measured over time were higher (P < .05) when diets contained SBM. Diet did not influence (P > .10) total VFA concentrations in ruminal fluid. Differences in diurnal shifts in ruminal NH3 N and total VFA due to protein source resulted in diet x hour interactions (P < .05). Dry matter intake response to protein source and frequency of supplement feeding was variable. Dry matter digestibility and nitrogen digestibility were not affected (P > .10) by protein source or feeding interval. The 48-h interval feeding of CGM was favorable compared with 24-h interval feeding (P < .05). The opposite response occurred with SBM, resulting in a diet x feeding interval interaction (P < .05). Nitrogen retention was greater (P < .05) when CGM was fed and with alternate day feeding. Diets that contained CGM supported higher (P < .05) ADG and gain/feed than diets that contained SBM when fed to steer calves. Alternate day feeding of supplements that contained monensin was detrimental to steer performance under the conditions of these experiments. Corn gluten meal is an effective substitute for SBM when alternate day protein supplementation is practiced.     

Effect of protein source and lasalocid on nitrogen digestibility and growth by ruminants

Protein supplements having either a high (soybean meal, SBM) or low (escape protein, EP) extent of ruminal N degradability with or without lasalocid (L) were evaluated in digestion and growth trials. The SBM supplement included soybean meal while EP was a combination of dehydrated alfalfa and distillers dried grains. Nitrogen digestibility of SBM supplements was consistently higher than EP supplements when evaluated with two lamb trials. Digestibility of N was improved 8% in trial one (64.9 vs 60.3%) and 27% in trial two (66.3 vs 52.3%) with SBM vs EP. The addition of L to the supplements improved N digestibility by 6% in trial one (64.5 vs 60.6%) and 13% in trial two (62.9 vs 55.7%). No interactions between protein source and L were measured in either trial. Dry matter digestibility was not changed by protein source or L in either trial. Rumen propionate was increased and acetate to propionate ratio decreased when L was fed. Plasma urea N was lower over a 24 h sampling period when lambs were fed EP supplements compared with SBM supplements (11.07 vs 16.44 mg/100 ml); however, L did not appear to consistently alter the values. When steers were supplemented with the same protein sources during a 105-d winter pasture trial daily gains were not affected (P greater than .10) by either protein source or L (.429, .495, .476 and .514 kg/d for SBM, SBM+L, EP and EP+L, respectively) although numerically there did not appear to be main effect improvements due to EP and L.(ABSTRACT TRUNCATED AT 250 WORDS)     

Feeding value of frost-damaged soybeans for lambs.

Three experiments were conducted to determine the relative feeding value of frost-damaged soybeans (FDS) for ruminants. Frost-damaged soybean ether-extract content was variable and differed (P less than .05) from mature soybeans. Isonitrogenous supplementation of corn silage diets with soybean meal (SBM), SBM+soybean oil (SBO), mature raw soybeans (MSB), and FDS was compared in sheep. Acid detergent fiber and apparent N digestion were lower (P less than .001) for supplements containing oil. Nitrogen retention was reduced (P less than .07) only for raw soybean supplements. Ruminal NH3 N and branched-chain VFA concentrations differed (P less than .01) between SBM and supplements containing oil. Maximum tolerable inclusion level of FDS in corn silage diets was tested in wethers using diets containing 0, 7, 14, or 21% FDS. Dry matter and ADF digestibility declined linearly (P less than .01) with increasing dietary FDS. Ether extract digestibility was unchanged due to treatment, but GE digestibility decreased quadratically (P less than .01). The most pronounced decline in GE digestibility occurred when FDS increased from 14 to 21% of the diet. The effects of FDS on corn silage utilization were similar to MSB effects. Oil content and antinutritional factors contributed to detrimental effects. Frost-damaged soybeans should not exceed 14% of corn silage diets fed to growing wethers.     

Evaluation of various nitrogen supplements in starter diets for growing Holstein steers and their effects on ruminal bacterial fermentation in continuous culture

Concurrent in vivo and in vitro studies were conducted to evaluate urea (U), soybean meal (SBM), ground soybeans (RAW), extruded soybeans (ES) or extruded soybeans plus urea (ES + U) as primary supplemental N sources in starter diets for Holstein steers. Three groups of 48 Holstein steers each were fed five different starter diets to 181 kg BW in three experimental periods over 2 yr. Average daily gains were similar (P greater than .05) for steers fed ES + U (1.12 kg), ES (1.08 kg) and SBM (1.09 kg) but lower (P less than .05) for those fed U (1.00 kg) or RAW (.97 kg) diets. Feed/gain was similar (P greater than .05) for ES-fed steers vs those fed other diets except U. From 181 to 477 kg, all steers were fed the same diet. Steers fed the RAW starter diet had the lowest (P less than .05) ADG for the entire period. The starter diets were used as substrates for ruminal microbial metabolism in eight dual-flow continuous culture fermenters. True OM digestion was higher and NDF and ADF digestion was lower (P less than .05) for the ES + U diet than for the ES diet. Dietary protein degradation was lowest (P less than .05) for the ES diet (64.4%). Total bacterial N flow was higher (P less than .05) with the ES + U, SBM and U diets than with the ES diet. Lysine flow was higher (P less than .05) for the ES + U diet than for all other diets except ES. Results of these experiments indicate that ES as a protected ruminal escape N source with or without added urea did not improve steer performance above that obtained from SBM in starter diets.     

Effects of dietary energy level and protein source on nutrient digestion and ruminal nitrogen metabolism in steers.

Four Simmental steers with ruminal, duodenal, and ileal cannulas were used to examine effects of dietary forage: concentrate ratio and supply of ruminally degradable true protein on site of nutrient digestion and net ruminal microbial protein synthesis. Steers (345 kg) were fed ammoniated corn cob (high forage; HF)- or corn cob/ground corn/cornstarch (low forage; LF)-based diets supplemented with soybean meal (SBM) or a combination of corn gluten meal and blood meal (CB). Diets were fed at 2-h intervals with average DM intake equal to 2.2% of BW. Feeding LF vs HF increased (P less than .05) OM digestion (percentage of intake) in the stomach, small intestine, and total tract. Efficiency of microbial CP synthesis (EMCP; g of N/kg of OM truly fermented) decreased (P less than .05) for LF vs HF (24.1 vs 26.8), but microbial N and total N flows to the small intestine were similar (P greater than .05) between energy levels (average 112 and 209 g/d, respectively). Total N flows to the small intestine were 13.1% greater (P less than .05) for CB than for SBM because of increased (P less than .05) passage of nonmicrobial N. Feeding SBM vs CB increased (P less than .05) EMCP (27.3 vs 23.3) and microbial N flow to the small intestine (127.5 vs 112.5 g/d), but these increases were not likely due to increased ruminal concentrations of ammonia N (NH3 N). Decreased (P less than .05) incorporation of NH3 N into bacterial N and slower turnover rates of ruminal NH3 N for SBM vs CB suggest that direct incorporation of preformed diet components into cell mass increased when SBM was fed. Results of this study suggest that the inclusion of ruminally degradable protein in the diet may increase the supply of products from proteolysis and that this can increase EMCP and microbial protein flow to the small intestine.     

Effects of corn gluten feed on forage intake, digestibility and ruminal parameters of cattle fed native grass hay

Thirty-two beef cows (467 kg) were individually fed native grass hay and supplement for two 14-d periods in each of 2 yr. Supplement treatments and amounts fed (kilograms/day) were negative control (NC), 0, or equal amounts of protein from soybean meal (SBM), .7; a blend of soybean meal and corn gluten feed (SBM/CGF), 1.0; or corn gluten feed (CGF) 1.6. Cows received supplement at 0645 and had ad libitum access to native grass hay from 0700 to 1130 and from 1530 to 2000. Compared with NC, all protein supplements increased (P less than .05) ruminal NH3, propionate and butyrate concentrations at 4 and 25 h postfeeding. Ruminal fluid pH, total VFA and acetate concentrations at 4 and 35 h postfeeding were not affected by supplements. All supplements increased (P less than .01) hay intake as well as hay, acid detergent fiber (ADF) and total diet dry matter (DM) digestibility. Compared to supplemental SBM, feeding CGF reduced (P less than .01) hay intake. Calculated daily intakes of metabolizable energy (ME) were 12, 17, 18, and 17 Mcal for NC, SBM, SBM/CGF and CGF, respectively. Hay intake, DM and ADF digestibility and ME intakes tended to be higher for SBM/CGF than for the average of SBM and CGF fed alone. Intakes of digestible DM and ADF were not altered by protein supplements, suggesting that intake responses were due to increased diet digestibility. Corn gluten feed appears to be an effective source of supplemental protein and energy for cows consuming low-quality roughage.     

Effects of heat and alcohol treatments of soybean meal on nitrogen utilization by sheep

Soybean meal (SBM) was treated with aqueous solutions of ethanol or propanol at room temperature or at 80 C to study treatment effects on SBM-N solubility and utilization by sheep. Soybean meal was soaked in an excess of 70% (v/v) ethanol at 80 C (ET-80), 70% ethanol at 23 C (ET-23) or 70% propanol at 80 C (PR-80). Nontreated SBM and nontreated SBM heated at 80 C without alcohol treatment (NT-80) served as controls. Nitrogen solubility in McDougall's buffer was lowest (P less than .05) for PR-80 and ET-80 (2.2 and 4.7% of total N, respectively), intermediate (P less than .05) for ET-23 (9.0%), greater (P less than .05) for nontreated SBM (36.2%) and highest for NT-80 (40.2%). In an situ study using three ruminally cannulated cows and two bags per treatment per animal per removal time, more (P less than .05) N remained in in situ bags after 3, 6, 9 and 12 h incubation for ET-23, ET-80 and PR-80 than for nontreated SBM and NT-80. A lamb metabolism trial, using 15 lambs in each of two periods, compared nontreated SBM, ET-23, ET-80, PR-80 and urea as N supplements. Nitrogen retention was higher (P less than .02) for lambs fed SBM treatments compared with urea. When the same N supplements were fed to wethers in a 5 X 5 Latin square experiment and duodenal N flow was measured, non-ammonia non-bacterial N flow was higher (P less than .07) for wethers fed SBM treatments than for wethers fed urea.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of soybean lipid on growth and ruminal nitrogen metabolism in cattle fed soybean meal or ground whole soybeans

Three experiments were conducted to determine the effect of soybean lipid on ruminal proteolysis of soybean meal (SBM) and ground whole soybeans (GSB). Experiment 1 was a 92-d growth experiment using 120 calves (206 kg) allotted to 12 pens of 10 calves each. Three replicate pens were assigned to each of the treatment supplements: low SBM (LSBM), low GSB (LGSB), high SBM (HSBM) and high GSB (HGSB). Calves received ad libitum amounts of corn silage top-dressed with the respective supplement (.81 kg/head). High protein supplements produced greater (P less than .05) gains than low protein supplements, with HSBM calves gaining faster (P less than .05) than HGSB calves and LSBM and LGSB calves having similar (P greater than .10) gains. In Exp. 2, 15 ruminally cannulated Angus X Hereford heifers (380 kg) fed corn silage were used to determine ammonia-N release from the treatment supplements: ground corn (control), GSB, SBM and SBM coated with soybean oil (SBMO). Heifers fed the control supplement had lower (P less than .05) ruminal NH3-N concentrations than those consuming soybean protein. Ruminal NH3-N concentrations were similar (P greater than .10) for GSB and SBM; whereas, SBMO had lower (P less than .10) concentrations than SBM through 3 h. In Exp. 3, two ruminally cannulated Angus X Jersey steers (250 kg) were used to determine in situ disappearance of SBM, GSB and SBMO. Total and feed N disappearances were greater (P less than .001) for GSB than SBM or SBMO.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nutritive value of ammoniated wheat straw fed to cattle

The effects of ammoniation of wheat straw on site and extent of digestion of nutrients by cattle and the nutritive value of the N added to the straw were studied using eight Hereford steers during three consecutive 21-d periods and analyzed in an incomplete block design with steers and periods as orthogonal blocking factors. The steers, approximately 30 mo old and weighing 360 +/- 24 kg, were cannulated in the rumen, duodenum and ileum. Diets consisted of untreated (US) or ammoniated (AS) wheat straw supplemented with a mineral-vitamin mixture. Steers fed US received four supplements in which the percentages of supplemental N from soybean meal (SBM) and urea were 0:100; 33:67; 67:33 or 100:0. Percentage of N and in vitro DM digestibility values were increased in US by the ammoniation process from .42 to 1.82 and 34.8 to 54.3, respectively. Total tract digestibility of OM consumed was similar among treatments, although total tract digestibility of dietary N was decreased by ammoniation. Ammoniation doubled (P less than .05) the synthesis of microbial N per unit of dietary OM truly fermented in the rumen. When SBM and urea were fed in combination they depressed (P less than .10) microbial N flow and synthesis of microbial N per unit of OM truly fermented more than each depressed flow and synthesis individually. The nutritive value of the increased N of AS was equivalent to between 67 and 100% of SBM N based on amounts (g/d) of non-ammonia N apparently digested in the small intestine.     

Manipulation of nitrogen digestion by sheep using defaunation and various nitrogen supplementation regimens

Five ruminally, duodenally, and ileally cannulated sheep (average BW 62 kg) were fed 65% roughage: 35% concentrate diets (CP = 15%) in a 5 x 5 Latin square design to study the applicability of using a combination of defaunation with N supplements (soybean meal [SBM], corn gluten meal [CGM], blood meal [BM], urea, and casein) with different extents of ruminal degradation to manipulate microbial protein synthesis and amount of ruminal escape protein. Diets were fed twice daily (1,759 g DM/d). Defaunation was accomplished with 30-ml doses of alkanate 3SL3 (active ingredient: sodium lauryl diethoxy sulfate)/sheep daily for 3 d with 2 d of fasting. Treatment 1 (control) involved feeding faunated sheep a diet in which the supplemental N (45% of total dietary N) was 67% SBM N and 33% urea N. Treatment 2 involved feeding defaunated sheep the same diet as the control. Treatments 3, 4, and 5 involved feeding defaunated sheep diets in which the supplemental N source was either 67% CGM-BM (1:1 N ratio) N:33% urea N, or 33% CGM-BM N:67% urea N or 33% CGM-BM N:33% urea N:33% casein N, respectively. Compared with the faunated control, defaunation decreased (P less than .05) ruminal ammonia concentration (19 vs 26 mg/dl) and increased (P less than .05) CP flow to the duodenum (253 vs 214 g/d) due to a trend for increases in both bacterial (BCP) and nonbacterial (NBCP) CP flows.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ruminal escape proteins and canola meal on nitrogen utilization by growing lambs

The effects of ruminal escape proteins and canola meal (CM) on N utilization by growing lambs were evaluated in two experiments. In both experiments, seven supplemental dietary protein treatments were fed. For each of these protein treatments a 3 x 3 Latin square metabolism trial was conducted, using two sets of three lambs and three periods. Within square treatments were 1.4, 1.7 and 2.0 times maintenance intake levels. In Exp. 1, protein treatments were control (7.0% CP, DM basis), urea fed at 9.5 or 12% dietary CP, CM fed at 9.5 or 12% dietary CP and a 50:50 (N basis) mixture of blood meal/corn gluten meal (BC) fed at 9.5 or 12% dietary CP. In Exp. 2, protein treatments were urea, 64% urea and 36% BC (all mixtures on a N basis), 36% urea and 64% BC, BC, 50% CM and 50% BC (CM/BC), CM and soybean meal (SBM), all at 10.5% CP. In Exp. 1, apparent N digestibility (AND) was lower for CM diets than for urea (P = .13) and BC (P less than .05) diets (49.0 vs 50.6 and 51.3%, respectively). Absorbed N was utilized with similar efficiencies for all supplemental protein sources. Dietary CP and digestible protein (DP) were closely related (DP = .879[CP%] -3.66; r2 = .91), indicating that for urea, CM and BC total tract N digestibility was not influenced by theoretical ruminal degradability. In Exp. 2, N balance and N utilization efficiency indicated that the optimal extent of ruminal protein degradation was about 50%. Nitrogen balance was similar for the CM, CM/BC and SBM treatments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of protein concentration and source on nutrient digestibility by mature steers limit-fed high-concentrate diets.

Five ruminally fistulated 3-yr-old mature Holstein steers (average BW 691+/-23 kg) were used in a 5 x 5 Latin square experiment with a 2 x 2 + 1 fact orial arrangement of treatments. Effects of protein concentration and protein source on nutrient digestibility, excretion of DM and fecal N, ruminal fluid volume and dilution rate, ruminal characteristics, and in situ DM disappearance of whole shelled corn, ground corn, and orchardgrass hay were measured in steers limit-fed high-concentrate diets at 1.5% of BW. A negative control basal diet (NC; 9% CP) was supplemented to achieve either 11 or 14% CP; supplemental CP was either from soybean meal (11 and 14% SBM) or a 50:50 ratio of CP from urea and soybean meal (11 and 14% U). Dry matter and OM digestibilities were 5% greater (P < .07) for steers fed the SBM diets than for those fed the U diets. Starch digestibility did not differ (P > .10) among steers fed any of the diets. Nitrogen source did not affect (P > .10) apparent N digestibility or fecal N excretion; however, steers fed the NC diet had the lowest (P < .10) apparent N digestibility compared with those fed all other diets. Ruminal fluid volume was lower (P < .06) when steers were fed the NC diet compared with all other diets; there were no differences (P > .74) among diets for ruminal fluid dilution rate. In general, ruminal ammonia N and VFA molar proportions were not affected by protein source or concentration. Although CP concentration affected (P < .06) in situ DM disappearance of ground corn, CP concentration did not (P > .48) affect total tract digestion of DM or OM. This indicates that CP concentration may have affected site of digestion, but not extent of digestion. When mature ruminants were limit-fed a corn-based diet to meet primarily a maintenance function, protein source and concentration had little effect on measures of nutrient digestion.     

Rumen fermentation characteristics, nitrogen balance and growth in lambs fed methane digester effluent

A laboratory silo trial, two lamb metabolism trials and a lamb growth trial were conducted to compare the nitrogen (N) value of swine methane digester effluent (MDE) to that of urea. Using laboratory silos (four/treatment), fermentation characteristics were measured for silages containing cracked corn, ground wheat straw and MDE added at levels of 0, 4, 8 or 12% of silage dry matter (DM). Lactic acid concentration increased linearly with up to 8% MDE addition, but then decreased (P less than .05; quadratic) with 12% MDE. Butyric acid was highest (P less than .05; linear) with 12% MDE, indicating an undesirable fermentation. In a metabolism study, DM, organic matter and N digestibilities and N balance were similar (P greater than .10) between urea and MDE, but DM digestibility was lower (P less than .05) for ensiled diets (52%) than diets fed fresh daily (59.4%). Mean ruminal volatile fatty acid, ruminal ammonia-N and plasma urea-N concentrations were similar (P greater than .10) between urea- and MDE-fed lambs. Plasma urea-N was higher (P less than .05) and ruminal isovaleric acid lower (P less than .05) in animals fed ensiled than fresh diets. In the second metabolism trial, digestibility of N was lowest (P less than .05) for MDE (51.2%) and highest for soybean meal (SBM; 71.8%), but N balance was similar among all diets.(ABSTRACT TRUNCATED AT 250 WORDS)