Protein and amino acid metabolism in the gastrointestinal tract of young bulls. 3. Flow of NH3-free raw protein into the duodenum

The amount of NH3-free crude protein getting into the duodenum corrected by the endogenous crude protein quota was determined on the basis of 28 differently composed rations for growing bulls in the live weight range of 140-460 kg provided with duodenal re-entrant cannulae. The experimental results were generalized by means of regression analysis and can be summarized as follows: The amount of NH3-free crude protein getting into the duodenum can partially be calculated with the regression equation (Formula: see text) resp. NH3-free crude protein D = 155 app. dig. org. matter + 0.262 pure protein +/- 42. The remaining dispersion amounts to +/- 6% of the mean value. The coincidence between the values calculated with these equations and those measured experimentally is very good. There is an interaction between the pure protein of feed getting into the duodenum in % of pure protein intake (y) and the bacteria crude protein D/kg app. dig. org. matter (x) characterized by the equation y = 116.8-0.52 x +/- 12.9. The amount of NH3-free crude protein duod. is not influenced by the flow rate (kg digesta/kg intake of org. matter) and not by the "dilution rate' (g bacteria free org. matter duod./kg live weight 0.75/h) either at a DM intake adequate to the production level. Apart from the partial estimation of the NH3-free crude protein duod. a evaluation based on the crude protein and pure protein concentration in app. dig. org. matter of the ration is possible.     

Protein and amino acid metabolism in the intestinal tract of growing young bulls. 7. Protein estimation and evaluation of protein supply in growing ruminants by the apparently digestible total protein in the duodenum based on rations

The following values were derived from experimental studies of the crude protein (CP) and amino acid (AA) metabolism of growing fattening bulls, the detailed results of which were described in installments 1-6, for the ascertainment of the content of apparently digestible total protein at the duodenum (ADTPD): a) partial method: Degradation quotaCP = NPN + 0.69 X g pure protein/CP; g AD feed PD = g CP (1 -decomposition quotaCP) X 0.72 or g AD feed PD = 0.31 X g pure protein X 0.72; g ADBPDE = 0.149 X g AD org. matter X 0.80 X 0.72 (ADBPDE = apparently digestible pure bacteria protein at the duodenum, dependent on energy release in the reticulo-rumen; g ADBPDN = g CP X (degradation quotaCP) X 0.80 X 0.72 (ADBPDN = apparently digestible pure bacteria protein at the duodenum, dependent on CP supply of rumen microbes); g AD total PD = g AD feed PD + ADBPDE g AD total PD = g AD feed PD + ADBPDN; b) summarizing method: AD total PD = 0.429 + 10.9 X 0.80/CP in % AD org. matter X (CP intake) X 0.72; AD total PD = 0.196 + 16.6 X 0.80/pure protein % AD org. m. X pure pr. intake X 0.72. The requirement of AD total PD was calculated under consideration of the endogenous urine N, skin N and hair N losses as well as protein retention per kg live weight assuming a utilization of 0.70 for this partial performance. The practical application of this balance method is demonstrated in comparison to the digestible CP-system.     

Protein and amino acid metabolism in the digestive tract growing young bulls. 1. Flow of bacterial raw protein in the duodenum determined by 2,6-diaminopimelic acid as a marker

The influence of the composition of the rations on the content of diamino pimelic acid (DAP) and N in the bacteria dry matter and on the flow of bacteria crude protein into the duodenum, determined with DAP as marker, was determined on the basis of experimental investigations with young bulls provided with duodenal cannulae and with 28 different rations whose details are described. At a production level corresponding to dry matter intake and a variation range of the crude fibre content of between 11.3 and 29.1% in the DM, a content of N-free extractives between 50.9 and 77.4% in the DM, a content of soluble carbohydrates ibetween 5.3 and 6.4% in the DM, a crude protein content of between 6.4 and 17.1% in the DM and a pure protein content of between 4.9 and 15.5% in the DM, the DAP content of the bacteria DM amounts the 0.350 g 100 g DM +/- 0.090 the N-content of the bacteria DM amounts to 7.37 +/- 1.08 g/100 g DM, there are no relations between DAP- and N-content in the bacteria DM and the content of the individual carbohydrate fractions of the ration, there are positive relations between DAP- and N-content of the bacteria DM, the flow of bacterial crude protein into the duodenum amounts to 133 +/- 14 g/kg truly fermentable organic matter or 130 +/- 14 g/kg apparently digestible organic matter, there is a negative relation between bacteria crude protein at the duodenum (BCPD)/kg truly fermentable organic matter and the crude fibre content of the ration, there is a positive relation between BCPD/kg truly fermentable organic matter and N-free extractives and soluble carbohydrate content as well as the digestibility of the organic matter of the ration, there is no specific influence of the flow rate (kg digesta/kg intake of org. matter) or the dilution rate (g bacteriafree org. matter D/kg LW075/b) on BCPD/kg truly fermentable org. matter, there is a dependence of BCPD/kg truly fermentable org. matter on crude protein concentration in the ration in the concentration range of 6.4-9.0% crude protein in the ration (provided endogenous CP equivalents are used).     

Protein and amino acid metabolism in the digestive tract of growing bulls. 6. Apparent digestibility of the amino acids entering the duodenum and of amino acid from feed

After studies with young bulls provided with duodenal cannulas the apparent digestibility (AD) of the individual amino acids getting into the duodenum (AAD) was ascertained on the basis of 28 different rations. The AD of the AAD is defined as follows: AAD--AAfaeces/AAD X 100. The results thus obtained show a relative constancy, only insignificantly impaired by the consideration of the dependence of the AD of the AAD on the AA concentration in the ration. The average value for the AD of the sigma AAD was 72.5 +/- 4.9%. The dependence of the AD of the sigma AAD on the sigma AA concentration in the ration is: y = 67.8 + 0.51x +/- 4.6; r = 0.355x. In addition, the relation between AD AAD and AD AAfeed protein' each in % of AA intake and AA concentration in the ration, was studied and reported on.     

Protein and amino acid metabolism in the digestive tract of growing young bulls. 2. Feed protein flow into the duodenum determined with 2,6-diaminopimelic acid as a marker for crude bacterial protein

The experimental ascertainment of the pure feed protein flowing into the duodenum on the basis of the calculation of the difference between the NH3-free crude protein flowing into the duodenum and the bacterial crude protein determined by means of DAPA showed the following results after the testing of 28 different rations at a dry matter intake adequate to the production level: With a variation of the pure protein in the crude protein content of the ration between 40 and 90%, the quota of feed protein flowing into the duodenum is 52.5%, and with a variation of the pure protein in the crude protein content between 80 and 90% it is 40.6%. The quota of feed protein flowing into the duodenum shows a negative correlation to the apparent digestibility of the organic matter (y=231.7 -2.52x +/- 14.5). With a DM-intake adequate to the production level the quota of feed protein flowing into the duodenum is neither influenced by the flow rate (kg digesta/kg DM-intake) nor by the 'dilution rate' (g bacteria-free DMD/kg live weight 0.75/h).     

Effects of increasing crude protein level on nitrogen retention and intestinal supply of amino acids in lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw.

The effects of increasing dietary CP level on N retention (Exp. 1) and intestinal supply of amino acids (AA; Exp. 2) were studied in lambs fed diets based on alkaline hydrogen peroxide-treated wheat straw (AHPWS). Soybean meal (SBM) was substituted for corn to increase CP level in both experiments. In Exp. 1, an incomplete design for the two-way elimination of error was used to allot 24 ram lambs (mean BW = 25 kg) within breed to six CP levels (6, 8, 10, 12, 14, and 16% of DM). Neutral detergent fiber digestibility and N retention increased quadratically (P = .06 and P less than .01, respectively) with increasing CP level. Nitrogen retention, expressed as a percentage of N intake, was greatest for lambs fed 12% CP (20.7%) but was greatest for lambs fed 14% CP when expressed as grams per day (4.0 g/d). In Exp. 2, five multicannulated St. Croix lambs (34 kg) were used in a 5 x 5 Latin square design. Treatments were 8.5, 11, 13.5, 16, and 18.5% dietary CP. Chromic oxide was used as a digesta flow marker and purines were used as a bacterial marker. Protein level had no effect on extent of dietary CP degradation in the rumen (69 +/- 3.2%). True ruminal OM digestibility increased (P less than .01) linearly and ruminal fluid NH3 N concentration increased (P less than .01) quadratically with increasing CP level. Total, bacterial, and nonbacterial N and AA flows to the duodenum increased (P less than .05) linearly with increasing CP level. Duodenal AA profile (g/100 g total AA) was altered slightly. The essential AA valine, isoleucine, phenylalanine, lysine, and arginine increased (P less than .05) and methionine decreased (P less than .05) in proportion to other AA with increasing CP level. Flows of all essential AA increased with increasing CP level. Apparent small intestinal N and AA disappearance increased linearly (P less than .05) and apparent total tract N digestibility increased (P less than .01) quadratically with increasing CP level. These data are interpreted to indicate that maximal N retention and fiber digestibility in diets based on AHPWS are obtained at 12% CP, even though the intestinal supply of AA continues to increase with increasing CP level. Supplementation of diets based on AHPWS with an extensively degraded protein source (SBM) does not substantially alter the profile of AA entering the duodenum compared to the AA profile of bacterial protein.     

Joint research on the precise determination of the energy and protein requirements of fattening pigs. 2. Energy and nitrogen metabolism of fattening hybrids in the fattening range of 30 to 120 kg

In 3 experiments a total of 242 total metabolism experiments with ad libitum feeding (experiment 1), 75% (experiment 2) and 62% (experiment 3) of the energy level of the 1st experiment and approximately equal protein and amino acid doses in experiments 1-3 were carried out with 8 castrated male fattening hybrids each (large white X land race pig) X line 150) in the live weight range between 30 and 120 kg. On average, feed intake over the whole live weight range was 2.24; 1.79 and 1.50 kg/animal and day, the corresponding daily live weight gain was 729, 533 and 396 g. With regard to the digestibility of the energy and the nutrients and the metabolisable energy in % of the gross energy there was no relation to the development of the animals. The intake of metabolisable energy per kg live weight decreased with ad libitum feeding and with the advancing development at the end of the experiment in contrast to the beginning of the experiment to 53%, energy retention to 56%. The utilisation of metabolisable energy for body energy retention, taking account of a maintenance requirement of 450 kJ/kg live weight 0,62 on the average of the 3 experiments was 68.4 +/- 1.9, 70.3 +/- 2.0 and 64.3 +/- 2.6%. Energy retention in experiments 1 to 3 amounted to 8.6, 6.8 and 5.3 MJ at the beginning and to 18.1, 12.2 and 8.0 MJ per animal and day at the end of the experiment. Protein energy retention of the pigs (live weight 40 kg) was 26% of the total energy retention in experiments 1 and 2 and 49% in experiment 3. In experiments 1 and 3 protein retention decreased to 15% of the total energy retention, in experiment 2 protein retention remained constantly at 22% between 60 and 110 kg live weight and then decreased to 18%. Consequently, the N-balances were 23-16 g, 16-20 g and 16-9 g/animal and day. The chemical composition of the carcasses was strongly influenced by the level of nutrition. At the beginning of the experiment the protein content averaged between 49 and 57% and the total fat content between 31 and 38% of the dry matter. At the end of the experiment the carcasses of the animals from experiments 1-3 had crude protein contents of 28, 33 and 42% and total fat contents of 66, 61 and 50% of the dry matter.     

Effects of oscillating dietary protein on ruminal fermentation and site and extent of nutrient digestion in sheep

Eight cannulated wethers (BW = 52.5 +/- 5.7 kg) were used in a replicated 4 x 4 Latin square designed experiment to evaluate the effects of oscillating dietary protein concentrations on ruminal fermentation, site and extent of digestion, and serum metabolite concentrations. Four treatments consisted of a 13, 15, or 17% CP diet fed daily or a regimen in which dietary CP was oscillated between 13 and 17% on a 48-h basis (ACP). All diets consisted of 65% bromegrass hay (10.5% CP, 61.9% NDF, 37.2% ADF) plus 35% corn-based supplement and were formulated to contain the same amount of degradable intake protein (9.6% of DM) plus additional undegradable intake protein (SoyPLUS, West Central Cooperative, Ralston, IA) to accomplish CP levels above 13%. Each of four experimental periods were 16 d in duration with 12 d for diet adaptation followed by 4 d for sample collection. All wethers were fed at 3.0% of initial BW (DM basis) throughout the experiment, resulting in an average organic matter intake of 1.39 kg/d across treatments. When compared to the 15% CP daily treatment, feeding ACP had no effect (P > or = 0.10) on ruminal or lower tract N, NDF, ADF, or OM digestion. True ruminal OM digestion responded quadratically (P = 0.07) to increasing dietary CP, reaching a maximum of 52.0% of OM intake with the 15% CP treatment. Sheep fed ACP tended to have lower (P = 0.08) ruminal NH3 N concentrations and an overall higher (P = 0.0001) molar proportion of acetate compared to those fed 15% CP daily. Total VFA concentrations were not affected (P > or = 0.45) by increasing dietary CP. Microbial efficiency did not differ (P > or = 0.55); thus, bacterial N flow at the duodenum responded quadratically (P = 0.04) to increasing dietary CP. Nonbacterial N (P = 0.001) and total N (P = 0.01) flows at the duodenum and total tract N digestibility (P < or = 0.04) increased linearly as dietary CP increased. Wethers fed ACP maintained a lower (P = 0.002) serum glucose and lower (P = 0.0006) serum urea N compared to those fed 15% CP daily. Because the CP content of the diet was increased at the expense of corn, the response to increased CP observed in this experiment is most likely due to negative associative effects of supplemental starch on ruminal fermentation and microbial growth. Oscillating the CP content of the diet on a 48-h basis has little effect on digestion or N utilization in sheep compared with feeding the same quantity of protein on a daily basis.     

Studies on the evaluation of feed protein for ruminants. 1. Passage of nitrogen fractions to the duodenum of dairy cows fed different protein and carbohydrate sources

The duodenal passages of non-ammonia nitrogen (NAN), amino acid N (AA-N) and microbial N (MN) were measured in seven duodenal fistulated dairy cows (6130 kg FCM/305 d) during lactation receiving 30 different rations similar to those used in dairy practice. The rations consisted of roughage (protein-rich silages, hay) and concentrate mixture (corn, barley, oat) in a ratio of 60:40 on a DM basis or roughage/concentrate mixture/fodder beets in the proportions 60:20:20 or 60:0:40 respectively. N supplements consisted of soya bean meal and peas meal (untreated or treated with formaldehyde in each case), rapeseed meal, fish meal and urea. DM intake varied between 9.6 and 19.1 kg/d, the crude fibre content between 166 and 270 g/kg DM, the crude protein (CP) content between 111 and 184 g/kg DM, the AA content (N basis) of the CP between 51 and 82%, the unfermentable CP content of the CP between 23 and 49% and the organic matter digestibility between 70 and 79%. The duodenal passage of NAN was 24.2 +/- 2.7 g/kg DM intake, 34.9 +/- 4.1 g/kg apparently digestible organic matter (in total tract, DOM), 43.3 +/- 5.5 g/kg apparently digestible carbohydrates or 4.2 +/- 0.5 g/MJ net energy fat, (y +/- s, n = 90). The value measured for AA-N was 16.8 +/- 2.9 g/kg DM intake, and that for RNA-labelled microbial CP was 146 +/- 26 g/kg DOM. NAN passage (g/kg DM intake) correlated more closely with the duodenal digesta flow rate (DFR) (kg digesta/kg DM intake) as an intrinsic animal factor (r = 0.78) and with the rumen content dilution rate (RDR) (passage of microbial-free organic matter at duodenum/kg BW0.75.h) as a ration dependent factor (r = 0.64) than with the UDP fraction (% of ration CP) (r = 0.50) or other ration parameters. It was concluded that the specific effect of protein concentrates in mixed rations on duodenal NAN yields in lactating dairy cows is lower than hitherto assumed. The duodenal NAN yield of a single feedstuff or ration (g/kg DM) in cows is dependent on animal and feeding factors. The DFR could represents a suitable target for breeding activities.     

控释尿素对藏羊瘤胃氨氮和微生物蛋白质的影响

作者旨在探讨控释尿素对藏羊瘤胃氨氮和微生物蛋白质合成的影响。试验选4只2岁藏羊，安装永久性瘤胃瘘管，分期定量饲喂不同粗蛋白质日粮：含尿素日粮（粗蛋白质含量为10.79%）、无尿素日粮（粗蛋白质含量为10.75%）、控释尿素日粮（粗蛋白质含量为10.73%）。结果表明，含尿素日粮瘤胃pH和氨氮浓度在一天中变化较快，而无尿素日粮和控释尿素日粮变化较为平缓，控释尿素日粮微生物蛋白质合成量虽然变化幅度较大，但能量与氨氮释放同步，微生物蛋白质合成量较大，充分把食用氮转化为微生物蛋白质。控释尿素日粮与含尿素日粮、无尿素日粮存在极显著差异（P<0.01），且控释尿素在瘤胃pH、氨氮浓度和微生物蛋白质含量方面均优于含尿素日粮和无尿素日粮，从而表明采用控释尿素日粮对藏羊补饲具有良好的效果，是反刍家畜安全、高效的粗蛋白质营养日粮。     

Methodologic studies on protein metabolism and bioenergetics of protein deposition in growing animals. 4. Energy metabolism in chickens in connection with measurement of parameters of protein metabolism

In connection with the measuring of parameters of the protein metabolism in parallel experiments, the energy metabolism of 6 chickens (origin Tetra B) in the live weight range between approximately 100 and 1,800 g was determined under conditions of restricted energy supply. 3 animals each received a feed mixture containing 20% (animal group 1) and 38% (animal group 2) crude protein. The amount of feed was daily increased by 1.5 g DM. The digestibility of energy and nitrogen was independent of the age. 66.3 +/- 3.3% and 64.0 +/- 5.0% resp. of the metabolisable energy were utilised for protein and fat retention. The energy maintenance requirement, determined at a live weight of 2,000 g, was independent of protein supply and averaged in the two animal groups 434 +/- 40 kJ metabolisable energy/kg live weight 0.75 . d. The result of multiple regression was, for the growth period investigated, an energy maintenance requirement of 403 +/- 32 kJ metabolisable energy/kg live weight 0.75 . d. 1.77 and 1.38 J metabolisable energy resp. were required for 1 J protein or fat retention. The energy requirement for protein retention was independent of the degree of protein supply. The results from the measuring of energy metabolism are discussed in connection with the kinetic parameters of protein metabolism ascertained in parallel experiments.     

Efficacy of laidlomycin propionate in low-protein diets fed to growing beef steers: effects on steer performance and ruminal nitrogen metabolism

We conducted two experiments to evaluate the effect of the ionophore laidlomycin propionate (LP) on steer performance and ruminal N metabolism. Experiment 1 was a 91-d growth study evaluating the growth and ruminal characteristics of steer calves consuming supplemental LP. Steers (n = 96; 255 +/- 3 kg; four steers/pen; six pens/treatment) were used in a randomized complete block design with a 2 x 2 factorial arrangement of treatments consisting of two levels of dietary CP (formulated to be 10.5 and 12.5% of DM) with and without LP (11 mg/kg diet DM). Ruminal fluid was collected via stomach tube on d 91 from one steer randomly selected from each pen. No CP x LP interactions were observed with performance data (P > .64). Final weight and total gain were greater (P < .07) for 12.5% CP and LP compared with 10.5% CP and control steers, respectively. Also, DMI was increased (P = .08) with 12.5% CP but not with LP supplementation (P = .36). In addition, ADG and gain:feed ratio were greater (P < .03) for both 12.5% CP and supplemental LP. Ruminal NH3 N concentration was greater (P < .09) with 12.5% CP and LP. Total VFA concentration and molar proportion of acetate were not affected by treatment (P > .11). However, propionate concentration was increased (P < .09) with 12.5% CP and LP, and acetate:propionate was lower (P = .02) with LP supplementation. In Exp. 2, six steers were used in a replicated 3 x 3 Latin square design to compare ruminal fermentation and protein degradation in steers without ionophore feeding or adapted to LP or monensin. In vitro deamination of amino acids by adapted ruminal microbes was also assessed. Ionophore supplementation decreased (P = .07) ruminal NH3 N concentration compared with control steers, and LP increased (P = .02) ruminal NH3 N compared with monensin. Molar proportion of acetate was decreased (P = .02) and propionate increased (P = .01) with ionophore treatment. Consequently, ionophore supplementation depressed the acetate:propionate ratio (P = .01). In situ degradation rate of soybean meal (SBM) CP was greater (P = .09) with ionophore treatment, but estimates of SBM undegradable intake protein were not altered by treatment (P > .25). Microbial specific activity of net NH3 N release and alpha-amino N degradation were decreased (P < .04) with ionophores. Based on this study, LP and monensin did not affect the extent of ruminal degradation of SBM CP but decreased amino acid deamination.     

Relationship between fecal crude protein concentration and diet organic matter digestibility in cattle

The positive relationship between fecal CP concentration and diet OM digestibility in cattle, which is based on increasing undigested microbial CP and decreasing fecal OM as OM digestibility increases, may be used as an indirect method for estimating diet OM digestibility from fecal CP concentration. Results of digestibility trials (445 individual observations) conducted at Hohenheim and Braunschweig, Germany, and at Gumpenstein, Austria, were used to study the relationship between CP concentration in feces (x, g/kg OM) and OM digestibility (y, %). The best fit was obtained with the curvilinear relationship y = ai -107.7e(-0.01515 x x), with a1 = 79.76 and a2 = 72.86 (R2 = 0.82; residual SD = 2.7; SE = 0.13), which takes into account the effects of location (i = 1 for Braunschweig and Hohenheim, and i = 2 for Gumpenstein). Dietary CP and crude fat concentration, and DMI had no effect on fecal CP content, whereas crude fiber content, proportion of concentrate in the diet, and forage type significantly affected CP concentration in feces; however, the magnitude of these effects was less than 2 percentage units, and the direction of the effect of proportion of concentrate in the diet was not uniform. The curvilinear relationship between fecal CP concentration (observed range, 100 to 300 g/kg of OM) and diet OM digestibility (observed range = 57 to 80%) may be used to estimate diet OM digestibility, particularly for field trials, as it requires no feed samples and does not physically restrict the animal.     

Ammonia,volatile fatty acids,phenolics, and odor offensiveness in manure from growing pigs fed diets reduced in protein concentration

The objective of this study was to investigate whether reducing dietary CP concentration decreases fecal VFA, manure ammonia (NH3) emission and odor, and urinary phenolic metabolites. Six barrows were allotted to one of six dietary treatments in a Latin square design. Treatments consisted of four corn-soybean meal based diets containing 15, 12, 9, and 6% CP, a casein-based diet containing 15% CP, and a protein-free diet (0% protein). Crystalline AA were included in the 12, 9, and 6% CP diets. The casein-based and protein-free diets were used to determine basal endogenous contribution of VFA, phenolics, NH3, and manure odor. Pigs were housed individually in metabolism cages to allow total collection of feces and urine. Feces and urine were collected and pooled within pig and period. Feces and urine were analyzed for VFA and phenolic metabolite concentrations, respectively. Feces and urine were then mixed, stored, and fermented at room temperature for 30 d. For NH3 determination, headspace air was sampled from manure slurries at 24, 48, and 72 h after fermentation. Slurry samples were placed into vials, capped, and randomized before odor panel evaluation. Odor offensiveness was classified on severity: 1 = non-offensive; 2 = mildly offensive; 3 = moderately offensive; 4 = strongly offensive; and 5 = extremely offensive. Reducing dietary CP increased (P < 0.05) fecal VFA concentrations but did not affect phenolic concentrations in urine. Manure NH3 emission was reduced (P < 0.05) as dietary CP concentration decreased from 15 to 0%. The 15% diet had the least offensive manure slurry with odor qualitative ranking of 2.58 (i.e., mild-moderately offensive). Compared with the 15% CP diet, manure from the 9 and 6% CP diets was found to be more offensive (P < 0.05), with qualitative rankings of 2.92 and 3.10, respectively. Odor qualitative rank for the 12% CP, protein-free diet, and casein-based diet did not differ from that of the 15% CP diet. These results indicate that reduction in dietary CP concentrations decreases manure NH3 emission, but it does not diminish manure odor offensiveness and fecal VFA concentrations.     

Effects of crude protein concentration and degradability on performance, carcass characteristics, and serum urea nitrogen concentrations in finishing beef steers

Two experiments were conducted at two locations to determine the effects of dietary CP concentration and source on performance, carcass characteristics, and serum urea nitrogen (SUN) concentrations of finishing beef steers. British x Continental steers were blocked by BW (357 +/- 28 and 305 +/- 25 kg initial BW; n = 360 and 225; four and five pens per treatment in Exp. 1 and 2, respectively). Steam-flaked corn-based diets were arranged in a 3 x 3 factorial with three CP concentrations (11.5, 13, or 14.5% of DM) and three sources of supplemental CP (N basis): 100% urea; 50:50 blend of urea and cottonseed meal; or 100% cottonseed meal. Steers in both experiments were initially implanted with Ralgro and reimplanted with Revalor-S on d 56. Performance and carcass data were pooled across locations. Crude protein concentration x source interactions were not observed (P = 0.22 to 0.93) for performance and carcass data. Crude protein concentration affected ADG (P = 0.02) and carcass-adjusted (to a common dressing percent within location) ADG quadratically (P = 0.06). Increasing the concentration of supplemental urea linearly increased carcass-adjusted ADG and G:F (P < 0.05) and carcass-adjusted G:F (P < 0.001). Dry matter intake was not affected (P = 0.93) by either CP concentration or source. Hot carcass weight (HCW; P = 0.02), LM area (P = 0.05), and dressing percent (P = 0.03) increased linearly with increasing urea concentration, whereas increasing CP concentration quadratically affected HCW (P = 0.02), with a maximum at 13% CP. Differences in backfat thickness and yield grade were negligible across treatments. Neither marbling score nor percentage of carcasses grading USDA Choice was affected by CP concentration or source. At all times measured, SUN concentrations increased (P < 0.05) with increasing CP concentration, but effects of CP source were small and variable across time. Results indicate that increasing CP concentrations from 11.5 to 13% slightly increased ADG and carcass-adjusted ADG, whereas increasing the proportion of supplemental urea increased carcass-adjusted ADG, G:F, and carcass-adjusted G:F and increased HCW, LM area, and dressing percent. A CP concentration above 13% seemed detrimental to ADG and HCW. Serum urea N increased over time, with CP concentration having a greater effect than CP source.     

Energy and protein concentration of broiler rations in Cuba. 4. Female broilers in the summer

A total of 1,900 female broilers of the variety White Plymouth Rock was tested with 4 energy concentrations (10.5, 11.5, 12.6 and 13.6 MJ metabolizable energy/kg feed) and 4 protein concentrations (15.0, 17.5, 20.0 and 22.5% CP) in their first 56 days of life in 16 test groups. The animals were kept in cages and were directly exposed to the natural Cuban summer temperatures from their 15th day of life onwards. As every test group was run with 6 repetitions, the results could be variance analytically calculated. In a comparison of male and female broilers in summer one can state that the female animals achieved a lower intake of feed, energy and crude protein as well as a lower live weight than the male animals. In winter the female broilers consumed between 15.7 and 36.4% more feed and achieved a live weight gain between 11.1 and 43% higher than in summer. It could be shown that the maximum live weight of the female broilers could be achieved in summer if rations containing 12.6 MJ metabolizable energy and 20% CP are fed in a one-phase feeding system.     

Ruminal protein degradation and protein value of feeds

The relationship between dry matter (DM) degradation and crude protein (CP) degradation in the dairy cow's rumen was determined with a view to defining the protein value of feeds for ruminants. The nylon bag technique was applied for these studies. For all the feeds investigate (green fodder and preserves from cocks-foot, ryegrass, alfalfa/grass and meadow grass, as well as alfalfa, extracted soybean meal) a significantly positive relationship was found to exist between the levels of DM and CP degradation (r = 0.73 to 1.0). The regression coefficient b1 (CP degradation as regressor) was found to average 0.87. The positive relationship between DM degradation and CP degradation implies that microbial protein amount and unfermented feed protein at the duodenum are negatively correlated. Model calculations show that, on account of the compensation between microbial protein and feed protein at the duodenum, in feeds with a CP concentration below 200 g/kg DM, the extent of ruminal protein degradation does not exert a marked influence on duodenal protein passage. The partial calculation of the duodenal protein supply on the basis of undegraded feed protein and microbial protein, as practiced in the new models of protein evaluation, leads to systematic errors unless the relationship between DM degradation and CP degradation is considered.     

Manure composition of swine as affected by dietary protein and cellulose concentrations

An experiment was conducted to investigate the effects of reducing dietary CP and increasing dietary cellulose concentrations on manure DM, C, N, S, VFA, indole, and phenol concentrations. Twenty-two pigs (105 kg initial BW) were fed diets containing either 14.5 or 12.0% CP, in combination with either 2.5 or 8.7% cellulose. Pigs were fed twice daily over the 56-d study, with feed intake averaging 2.74 kg/d. Feces and urine were collected after each feeding and added to the manure storage containers. Manure storage containers were designed to provide a similar unit area per animal as found in industry (7,393 cm2). Before sampling on d 56, the manure was gently stirred to obtain a representative sample for subsequent analyses. An interaction of dietary CP and cellulose was observed for manure acetic acid concentration, in that decreasing CP lowered acetic acid in pigs fed standard levels of cellulose but increased acetic acid in pigs fed greater levels of cellulose (P = 0.03). No other interactions were noted. Decreasing dietary CP reduced manure pH (P = 0.01), NH4 (P = 0.01), isovaleric acid (P = 0.06), phenol (P = 0.05), and 4-ethyl phenol (P = 0.02) concentrations. Increasing dietary cellulose decreased pH (P = 0.01) and NH4 (P = 0.07) concentration but increased manure C (P = 0.03), propionic acid (P = 0.01), butyric acid (P = 0.03), and cresol (P = 0.09) concentrations in the manure. Increasing dietary cellulose also increased manure DM (P = 0.11), N (P = 0.11), and C (P = 0.02) contents as a percentage of nutrient intake. Neither cellulose nor CP level of the diet affected manure S composition or output as a percentage of S intake. Headspace N2O concentration was increased by decreasing dietary CP (P = 0.03) or by increasing dietary cellulose (P = 0.05). Neither dietary CP nor cellulose affected headspace concentration of CH4. This study demonstrates that diets differing in CP and cellulose content can significantly impact manure composition and concentrations of VFA, phenol, and indole, and headspace concentrations of N(2)O, which may thereby affect the environmental impact of livestock production on soil, air, and water.     

Determination of kinetic parameters of protein metabolism in growing rats in conjunction with the measurement of energy metabolism. 2. Determination of the energy requirement for protein retention in conjunction with measurement of the protein synthesis rate at different levels of protein supply

Energy metabolism-by means of indirect calorimetry-and kinetic parameters of the protein metabolism on the basis of the 3-compartment model were measured with 4 groups of 4 or 5 male Wistar rats in the growth range of between 70 and 230 g live weight in a total of 5 alternately successive periods at the feeding levels growth and energy maintenance as well as 4 different levels of protein supply (6, 10, 17 and 26% crude protein in the feed). The partial energy requirement values for protein retention (bp) for every animal and every period are calculated from the data of energy metabolism. On an average of the 3 growth periods they amounted to 1.75 +/- 0.37 kJ/kJ. A statistically significant linear relation with a slope of approximately 1 could be derived regressively between the protein synthesis rate and the protein retention rate, including all 5 test periods. There was no proven relation between the bp values and the corresponding individual values of the ratio of protein synthesis rate-diminished by the regressively derived protein synthesis rate in the N balance-to the protein retention rate. The results do not permit proven statements on the quantitative relations between protein turnover and energy requirement for protein retention, which is first of all due to methodical shortcomings in measuring both protein metabolism and energy metabolism. They indicate, however, that the heat production from protein synthesis has only a relatively low share in the additional energy expenditure for protein retention and does not considerably surpass the necessary minimal cost for the synthesis of the deposited protein in growing rats.     

Influence of rumen protein degradability and supplementation frequency on steers consuming low-quality forage: II. Ruminal fermentation characteristics

Seven ruminally and duodenally cannulated steers (264 +/- 8 kg BW) consuming low-quality forage (5% CP; 61% NDF; 31% ADF) were used to determine the influence of CP degradability and supplementation frequency (SF) on ruminal fermentation characteristics. Treatments included an unsupplemented control and degradable intake protein (DIP) or undegradable intake protein (UIP) provided daily, every 3 d, or every 6 d. The DIP treatments (18% UIP) were calculated to provide 100% of the DIP requirement, while the UIP treatments (60% UIP) were provided on an isonitrogenous basis compared with DIP. Ruminal NH3-N was increased on the day all supplements were provided with supplemental CP (P = 0.04) and for DIP compared with UIP (P < 0.01). Also, because ruminal NH3-N increased at a greater rate with DIP compared with UIP as SF decreased, a linear effect of SF x CP degradability interaction (P = 0.02) was observed. In addition, NH3-N was greater on the day only daily supplements were provided for supplemented treatments (P = 0.04), and decreased linearly (P < 0.01) as SF decreased. Concentration of total VFA increased linearly (P = 0.02) as SF decreased on the day all supplements were provided, whereas on the day only daily supplements were provided, total VFA were greater for UIP compared with DIP (P = 0.01), and decreased linearly (P < 0.01) as SF decreased. An interaction concerning the linear effect of SF and CP degradability (P = 0.02) was observed for ruminal liquid volume on the day all supplements were provided. This was the result of an increase in liquid volume with DIP as SF decreased compared with a minimal effect with UIP. In contrast, there was no influence of supplementation on liquid volume the day only daily supplements were provided. Ruminal liquid dilution rate was greater (P = 0.02) with CP supplementation on the day all supplements were provided. We did observe a quadratic effect of SF x CP degradability interaction (P = 0.01) for dilution rate because of a quadratic response with DIP (greatest value with the every-third-day treatment) compared with a decrease as SF decreased for UIP. On the day only daily supplements were provided, ruminal liquid dilution rate decreased linearly (P = 0.02) as SF decreased. These results suggest that DIP and UIP elicit different effects on ruminal fermentation when supplemented infrequently to ruminants consuming low-quality forage while not adversely affecting nutrient intake and digestibility.