Effect of ruminal protein degradability on growth and N metabolism in growing beef steers

The objective of two experiments was to correlate plasma levels of urea N (PUN) and the percentage of urine N in the form of urea (UUN) to weight gain in response to different dietary protein regimens for growing Angus steers. In Exp. 1, 60 steers (302 kg BW) were assigned to various levels of dietary N (control plus supplemental N to provide from 100 to 400 g more crude protein daily) within two sources of supplemental N (soybean meal [SBM] or a mixture of two parts corn gluten meal:one part blood meal [CGM:BM]). In Exp. 2, 27 steers (229 kg BW) were fed two levels of SBM, and half of the steers received growth-promoting implants. Steers were housed in groups of 12 and fed individually for 84 d in both experiments. Corn silage was fed at a restricted rate to minimize orts. Jugular blood and urine samples were collected during the experiments. In Exp. 1, maximal ADG of steers fed SBM (1.0 kg) was reached with 671 g/d total crude protein, or 531 g/d metabolizable protein. Maximal ADG of steers fed CGM:BM (0.91 kg) was reached with 589 g/d total crude protein, or 539 g/d metabolizable protein. The DMI was higher (P < 0.07) for steers fed SBM (6.37 kg/d) than for steers fed CGM:BM (6.14 kg/d). Increasing ruminal escape protein from 36% (SBM) to 65% (CGM:BM) of CP decreased (P < 0.05) endogenous production of urea, as evidenced by lower concentrations of urea in blood and lower UUN. In Exp. 2, increasing supplemental protein from 100 to 200 g/d increased (P < 0.05) ADG and PUN. Implants lowered (P < 0.05) UUN, particularly at the higher level of supplemental protein. Protein supplementation of growing steers can be managed to maintain acceptable ADG yet decrease excretion of urea in the urine.     

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.     

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.     

Performance and digestibilities of beef cattle fed diets supplemented with either soybean meal or roasted soybeans and implanted with Synovex.

Two 160-d feedlot experiments, each consisting of 20 Angus-Hereford steers (216 +/- 5 kg BW, Exp. 1; 258 +/- 5 kg BW, Exp. 2) and 20 Angus-Hereford heifers (208 +/- 5 kg BW, Exp. 1; 236 +/- 5 kg BW, Exp. 2), were used to investigate the effects of supplementing diets with either roasted soybeans (RSB, roasted at 127 degrees C for 10 min) or soybean meal (SBM) and implanting or not implanting with an estrogenic growth promoter (SYN; Synovex-S, 20 mg of estradiol benzoate plus 200 mg of progesterone or Synovex-H, 20 mg of estradiol benzoate plus 200 mg of testosterone) on performance. The cattle were fed a basal diet of 15% orchardgrass silage, 15% corn silage, and 70% corn-based concentrate. Treatments were 1) no SYN and fed a SBM-supplemented diet, 2) no SYN and fed a RSB-supplemented diet, 3) SYN and SBM, and 4) SYN and RSB. Cattle in the SYN groups were reimplanted at 80 d. Four additional Angus-Hereford steers were used in a digestion and nitrogen balance experiment conducted during the first half of Exp. 1. For the total 160-d feedlot experiments, DMI for RSB compared with SBM was lower (P < .01; 8.5 vs 9.2 kg/d, SEM = .07) and ADG/DMI tended to be higher (P < .10; 165 vs 157 g/kg, SEM = 1.3). Final BW of steers fed RSB was similar (P > .10) to that of steers fed SBM (473 vs 478 kg, SEM = 5.6), as was ADG (1.39 vs 1.43 kg/d, SEM = .02). Dry matter intake for SYN-implanted steers was higher (P < .01) than for steers not implanted (9.2 vs 8.5 kg/d). Likewise, final BW (491 vs 460 kg) and ADG (1.49 vs 1.33 kg/d) were higher (P < .01), and ADG/DMI (166 vs 157 g/kg) tended to be higher (P < .10), for SYN-implanted steers than for steers not implanted. During the more rapid muscle growth period (0 to 80 d), DMI for RSB compared with SBM was lower (P < .01; 7.8 vs 8.6 kg/d, SEM = .07) and ADG/DMI was similar (P > .10; 181 vs 172 g/kg, SEM = 1.8). Dry matter intake for SYN-implanted steers was higher (P < .05) than for steers not implanted (8.4 vs 8.0 kg/d), as was ADG/DMI (P < .01, 182 vs 171 g/kg). During this more rapid growth period, the supplement x implant interaction for ADG was significant (P < .05; 1.35, 1.36, 1.59, and 1.44 kg/d for Treatments 1, 2, 3, and 4, respectively, SEM = .04). There were no differences in digestibilities or N balance. The results suggest that there is no improvement in performance under feedlot conditions when RSB replaces SBM in the diet of beef cattle, and, in young cattle, RSB may reduce the response expected by an estrogenic growth promoter.     

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.     

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.     

Intestinal supply of amino acids in sheep fed alkaline hydrogen peroxide-treated wheat straw-based diets supplemented with soybean meal or combinations of corn gluten meal and blood meal

The intestinal supply of amino acids (AA) in sheep fed alkaline hydrogen peroxide-treated wheat straw (AHPWS)-based diets supplemented with soybean meal (SBM) or corn grain plus combinations of corn gluten meal (CGM) and blood meal (BM) was measured in a 5 X 5 latin square. Sheep (avg wt 45 kg) with ruminal, duodenal and ileal cannulas were fed diets containing 65% AHPWS supplemented with the following protein sources: soybean meal (SBM), corn gluten meal (CGM), blood meal (BM), 2/3 CGM:1/3 BM and 1/3 CGM:2/3 BM. Total nitrogen (N) flow at the duodenum was not affected (P greater than .05) by protein source. Flows of bacterial N and AA increased (P less than .05) and flows of nonbacterial N and AA decreased (P less than .05) when wethers were fed SBM vs corn plus other protein sources. When diets contained SBM, quantities of total AA at the duodenum were lower (P less than .05) and the profile of AA supplied to the intestine was altered substantially. Total flows of AA at the duodenum and total quantities of AA disappearing from the small intestine were similar (P greater than .05) for all diets containing BM and CGM, but flows and disappearance of valine, histidine, lysine and arginine increased linearly (P less than .05), whereas flows and disappearance of leucine, isoleucine and methionine decreased linearly (P less than .05) as BM replaced CGM in the diets. Results suggest that quantities of individual AA flowing to the duodenum and disappearing from the intestine of wethers fed AHPWS-based diets can be altered by source of dietary protein. Furthermore, feeding protein sources resistant to ruminal degradation in combination may improve the profile of AA supplied to the intestine.     

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.     

Optimizing nitrogen utilization in growing steers fed forage diets supplemented with dried citrus pulp

Our objectives were to compare the effects of sources of supplemental N on ruminal fermentation of dried citrus pulp (DCP) and performance of growing steers fed DCP and bahiagrass (Paspalum notatum) hay. In Exp. 1, fermentation of DCP alone was compared with that of isonitrogenous mixtures of DCP and solvent soybean meal (SBM), expeller soybean meal (SoyPLUS; SP), or urea (UR). Ground (1 mm) substrates were incubated in buffered rumen fluid for 24 h, and IVDMD and fermentation gas production kinetics and products were measured. Nitrogen supplementation increased (P < 0.10) ruminally fermentable fractions, IVDMD, pH, and concentrations of NH3 and total VFA, but reduced the rate of gas production (P < 0.10) and the lag phase (P < 0.01). Supplementation with UR vs. the soy-based supplements increased ruminally fermentable fractions (P < 0.05) and concentrations of total VFA (P < 0.10) and NH3 (P < 0.01), but these measures were similar (P > 0.10) between SBM and SP. In Exp. 2, 4 steers (254 kg) were fed bahiagrass hay plus DCP, or hay plus DCP supplemented with CP predominantly from UR, SBM, or SP in a 4 x 4 Latin square design, with four 21-d periods, each with 7 d for DMI and fecal output measurement. Nitrogen-supplemented diets were formulated to be isonitrogenous (11.9% CP), and all diets were formulated to be isocaloric (66% TDN). Intake and digestibility of DM, N, and ADF were improved (P < 0.05) by N supplementation. Compared with UR, the soy-based supplements led to greater (P < 0.05) DM and N intakes and apparent N and ADF digestibilities. Plasma glucose and urea concentrations increased (P < 0.10) with N supplementation and were greater (P < 0.01) for the soy-based supplements than for UR. Intake, digestibility, and plasma metabolite concentrations were similar (P > 0.1) for SBM and SP. In Exp. 3, 24 steers (261 kg) were individually fed bahiagrass hay plus DCP (control), or hay plus DCP supplemented with CP predominantly from UR or SBM. Over 56 d, DMI and ADG were greatest (P < 0.05) in steers fed SBM. Nitrogen supplementation increased (P < 0.05) DMI, ADG, and G:F. However, SBM supplementation produced greater (P < 0.05) DMI and ADG and similar (P > 0.05) G:F compared with UR supplementation. We conclude that supplemental N is important to optimize ruminal function and performance of growing steers fed forage diets supplemented with DCP. Diets with supplemental N mainly from SBM improved diet digestibility and animal performance beyond that achieved by UR.     

Effect of alkali pretreatment of wheat straw on the efficacy of exogenous fibrolytic enzymes

The effects of pretreating wheat straw with alkali on the efficacy of exogenous fibrolytic enzymes for improving straw digestibility were studied in vitro, in situ, and in vivo. In Exp. 1, untreated straw (US); alkali-treated (5% NaOH, wt/wt) straw (AS); and autoclaved, alkali-treated straw (AAS) were sprayed with 0 or 1.5 mg/g DM of enzyme mix (xylanase, beta-glucanase, carboxymethylcellulase, and amylase) and incubated for 30 h in buffered ruminal fluid (3 x 2 factorial arrangement). Enzymes increased (P < 0.001) gas production and the incorporation of 15N into microbial N at 4 h, more so with AS or AAS than with US (P < 0.001 for gas; P < 0.05 for 15N). In Exp. 2, US and AS were sprayed with enzymes at 0, 0.15, or 1.5 mg/g DM (2 x 3 factorial) and incubated ruminally in nylon bags for up to 80 h to determine the in situ DM disappearance (ISDMD). Interactive effects (P < 0.05) of pretreatment and enzymes were observed on all ruminal degradation parameters. Alkali increased the rate (P < 0.01) and extent (P < 0.001) of ISDMD irrespective of enzymes. Enzymes applied to US did not affect the extent of ISDMD, but they increased (P < 0.01) the extent of ISDMD when applied to AS. Substrates from Exp. 1 and 2 were incubated in acetate buffer for 24 h to measure the hydrolytic loss of DM and release of reducing sugars and phenolic compounds. Alkali pretreatment and enzymes each increased (P < 0.001) DM loss and the release of reducing sugars and, in combination, exerted synergistic effects (P < 0.001). Enzymes did not affect the release of phenolic compounds from the straw. In Exp. 3, total-tract digestibility of untreated and enzyme-treated (100 mL/kg DM) ammoniated straw was assessed using 32 beef cows in eight pens. Wrapped straw bales were injected with NH3 (3% [wt/wt], DM basis) 4 mo before the study; enzymes were applied immediately before feeding. Applying enzyme to ammoniated straw increased (P < 0.05) digestibilities of DM, OM, and total N but did not affect the intake of DM or digestibility of ADF. Pretreatment of straw with alkali enhanced the efficacy of exogenous enzymes, presumably by breaking esterified bonds and releasing phenolic compounds and/or by swelling the crystalline cellulose and enhancing enzyme penetration. Including enzymes that mimic alkali hydrolysis (e.g., esterases) in commercial feed additives could substantially improve the value of these products for ruminants.     

Supplementation of ammoniated wheat straw: performance and forage utilization characteristics in beef cattle receiving energy and protein supplements.

Two experiments were conducted to evaluate performance and forage utilization characteristics of beef cattle fed ammoniated wheat straw (AWS) unsupplemented except for minerals or supplemented with energy and protein. In Exp. 1, 194 crossbred beef cows (BW = 472 kg) in late gestation were allotted by weight, breed type, and age during two consecutive winters to 12 drylot pens (three pens/treatment) for a 60-d feeding trial. The AWS (3% NH3 wt/wt) was tubground through a 7.6-cm screen, and cows were allowed ad libitum access to the AWS. In Exp. 2, 16 ruminally fistulated Angus x Hereford steers (BW = 300 kg) were blocked by weight and randomized to treatments in a 35-d intake-digestion trial. Daily supplementation treatments in both experiments were Control, no supplemental energy or protein; LSG, 1.36 kg of sorghum grain (SG); HSG, 2.72 kg of SG; and SG + SBM, 1.02 kg of SG + .34 kg of soybean meal (SBM). All animals received .23 kg of mineral mixture formulated to meet a pregnant cow's mineral requirements. Supplements LSG and SG + SBM were fed to provide the same daily ME, and HSG and SG + SBM were fed to provide the same daily CP. Cows were managed as one group during and after calving. In Exp. 1, all supplements increased gain (P less than .01) vs Control, and cows fed SG + SBM had higher (P = .05) gains than those fed LSG. The SG + SBM supplement increased (P less than .01) change in cow body condition score compared with LSG.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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)     

Effects of starch and protein sources on starch disappearance in the gastrointestinal tract of Hanwoo (Korean native) steers

Hanwoo (Korean native) steers (274.8 ± 4.6 kg) with ruminal and duodenal cannulae were used in a 4 × 4 Latin square design experiment to examine the effects of dietary treatments on starch disappearance in the gastrointestinal tract. Dietary treatments consisted of concentrate that were based on ground corn with soybean meal (C‐SBM), ground corn with corn gluten meal (C‐CGM), ground barley with soybean meal (B‐SBM) and ground barley with corn gluten meal (B‐CGM). Although the intakes of starch and protein for steers fed experimental diets were different, it did not change ruminal pH and total volatile fatty acid concentrations. Average duodenal CP flow and quantity of CP apparently digested post‐ruminally was higher (P = 0.001) for CGM‐based diets than SBM‐based diets. There were increases in quantity (P < 0.001) and percentage (P < 0.001) of corn starch digested post‐ruminally compared to barley starch. Synchronized diets showed higher percentages (P = 0.03) of starch apparently digested post‐ruminally than asynchronization. Hanwoo steers fed a corn‐based diet with a large quantity of starch reaching the duodenum and fed C‐CGM supplying great amounts of protein to the small intestine may have contributed to increased post‐ruminal starch digestion.     

Steam-rolled wheat diets for finishing cattle: effects of dietary roughage and feed intake on finishing steer performance and ruminal metabolism

Two experiments were conducted to determine the influence of dietary roughage concentration and feed intake on finishing steer performance and ruminal metabolism. In Exp. 1, 126 steers (334 kg) were used in a completely randomized design and fed (120 d) diets of steam-rolled wheat without roughage or containing 5, 10 or 15% roughage (50% alfalfa hay:50% corn silage). Steers fed 5 or 10% roughage gained faster (quadratic, P less than .05) and were more efficient (quadratic, P less than .05) than steers fed 15% or no roughage. In Exp. 2, six ruminally cannulated steers (447 kg) were used in a 6 x 6 latin square design and fed (twice daily) diets of steam-rolled wheat without roughage or containing 5 or 15% alfalfa hay at twice or three times NE required for maintenance. Increasing dietary roughage increased (linear, P less than .01) ruminal liquid passage 38%, indigestible ADF passage 63%, Yb-labeled wheat passage 75% and fiber fill 31%. The rate of in situ starch digestion tended to increase (linear, P = .16), and ruminal VFA concentration was 40 mM higher (P less than .01) at 4 h after feeding with increased roughage. Increased feed intake increased (P less than .05) ruminal starch fill, fiber fill, liquid fill and liquid passage 23%, Yb-labeled wheat passage 50% and Dry-labeled hay passage 20%. It reduced protozoa five- to sixfold (P less than .01) but doubled total bacterial counts (P less than .01). Ruminal NH3N was lower (P less than .01) and total VFA concentration was 50 mM higher (P less than .01) at 4 h after feeding. The acetate:propionate ratio was reduced from 2.3 to 1.3 (P less than .01) with increased intake. Adding roughage to a steam-rolled wheat diet increased passage and tended to increase rate of starch digestion; increased feed intake with its associated effects on ruminal fill and passage dramatically shifted the microbial population and fermentation end products.     

The effect of roasted soybeans in the diet of feedlot steers and Synovex-S ear implants on carcass characteristics and estimated composition.

Beef steer carcasses from three 2 x 2 factorial feeding experiments (Exp. 1, 20 carcasses; Exp. 2 and 3, 19 carcasses each) were evaluated to study the influence of supplementing with roasted soybeans (RSB; 127 degrees C for 10 min) vs soybean meal (SBM) and implanting with the estrogenic growth promoter Synovex-S (SYN, 20 mg estradiol benzoate and 200 mg progesterone) on carcass merit, composition of dissected 9-10-11th rib section, estimated edible carcass composition, and cooking characteristics of strip loin steaks. In all experiments, steers were fed diets consisting of 15% corn silage, 15% orchardgrass silage, and 70% corn-based concentrate. There were no treatment interactions found in this study. Final BW averaged 480.4, 498.5, and 500.7 kg for Exp. 1, 2, and 3, respectively, and hot carcass weights averaged 288.4, 296.4, and 309.1 kg. Across experiments, hot carcass weight was 8.3 kg less (P < .03) for RSB steers than for SBM steers. Fat weight (P < .01) and percentage of fat (P < .01) were less and percentage of bone (P < .04) was greater in the 9-10-11th rib section of RSB steers than of SBM steers. Estimated percentage of fat (P < .02) was less and percentage of bone (P < .04) was greater in edible carcass of RSB steers than in that of SBM steers. Total 9-10-11th rib section weight tended to be less for RSB steers (P < .08) than for SBM steers. Carcass merit measurements were not affected (P > .10) by supplement, but numerically the percentage of kidney, pelvic, and heart fat was 11% greater for RSB steers than for SBM steers in Exp. 2 and 3. Final BW and carcass weight were 38.7 and 22.6 kg greater (P < .01), respectively, for SYN-implanted steers than for steers not implanted. Longissimus muscle area was greater (P < .01), percentage of kidney, pelvic, and heart fat (P < .02) was less, USDA quality grade tended to be less (P < .09), and shear force of strip loin was greater (P < .01) for SYN-implanted steers than for steers not implanted. The 9-10-11th rib section and estimated carcass compositions were not different (P > .10) between SYN-implanted steers and steers not implanted but reflected a somewhat leaner carcass. The authors conclude from this study that in feedlot steers, either implanted or not implanted, there is no benefit from supplementing with RSB in place of SBM, and that the use of RSB in place of SBM in feedlot diets may reduce the amount of edible carcass.     

Effects of Dietary Acetate and Propionate on Nutrient Digestibility,Ruminal Characteristics,and Performance by Steers Fed Diets Containing All-Concentrate or 20% Roughage

Four experiments were conducted to evaluate the effects of dietary volatile fatty acids (VFA) on nutrient digestibility, ruminal characteristics, and growth performance by finishing steers. Diets were based on sorghum grain in Exp. 1 and 2, and corn in Exp. 3 and 4. Experiment 1 was a digestibility study with eight steers used in two 4 x 4 latin square arrangements of steers and diets. Diets in the first square were all-concentrate (C) with 1 or 2% acetate (A) or 2% propionate (P), and diets in the second square were 20% rice straw (RS) with 1 or 2% A or 2% P. In Exp. 2, steers (four per treatment) were individually fed C or RS basal diets with 1.72% A or 5.00% P added to the C diet, and 1.14% A or 3.33% P added to the RS diet based on expected intake. In Exp. 3 and 4, C diets were diluted with 1.65 or 0.55% A, respectively. These diets were further diluted with 20% rice hulls (RH) in Exp. 3, and 20% RH and 20% RS in Exp. 4. The C diet was also diluted with 20% RS in Exp. 3 and considered a positive control. Adding A, P, or RS to C diet based on sorghum grain had no effect (P>0.10) on energy digestibility or N retention. In Exp. 2, P reduced (P<0.05) DMI and ADG, compared with A. Acetate improved (P<0.05) DMI of C and RH diet in Exp. 3, but only the RH diet in Exp. 4. Likewise ADG and, in most cases, carcass weights were improved (P<0.05) by A in C and RH diets, but not in RS diets. Dietary P reduced (P<0.05) ruminal acetate levels and increased (P<0.05) ruminal propionate in Exp. 2. Acetate may have potential to improve DMI and ADG of steers consuming diets containing all-concentrate or poorly digestible roughage.     

Hydrolyzed feather meal as a protein source for growing calves

Growth, digestion and in situ studies were conducted to determine the protein value of hydrolyzed feather meal (Fth) for growing ruminants. Dacron bags containing blood meal (BM), Fth, corn gluten meal (CGM) and soybean meal (SBM) were suspended in the rumen of two steers for 12 h to estimate escape protein. The escape protein value for Fth, 69.1%, was less than that for BM (82.8%) and CGM (80.4%; P less than .05) but greater than that for SBM (26.6%; P less than .05). Apparent protein digestion by lambs was similar (P greater than .10) for isonitrogenous diets containing urea (U), BM, Fth, CGM and SBM. Amino acid contents of the protein sources before vs after a 12-h ruminal in situ digestion were similar (P greater than .10). In a growth study, a basal diet of 80% ensiled corncobs and 20% alfalfa was fed to 60 individually fed crossbred steers (215 kg BW). Steers were supplemented with U, BM, Fth, 1/2 BM:1/2 Fth, 1/2 BM:1/2 CGM and 1/3 BM:1/3 Fth:1/3 CGM (protein basis). Protein sources were fed at 30, 45 and 60% of the supplemental N with urea supplying the remainder. Protein efficiency was calculated using the slope ratio technique. Protein efficiency was similar (P greater than .10) for BM- and Fth-supplemented calves. Protein efficiencies were similar (P greater than .10) for BM:CGM, BM:Fth and BM:Fth:CGM combinations. These data indicate the Fth is a digestible high escape protein source that is useful in diets for growing ruminants.     

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)     

Comparative feeding value of steam-flaked corn and sorghum in finishing diets supplemented with or without sodium bicarbonate.

A feedlot growth-performance trial involving 64 yearling steers and a metabolism trial involving four steers with cannulas in the rumen, proximal duodenum, and distal ileum were conducted to evaluate the comparative feeding value of steam-flaked corn (SFC, density = .30 kg/liter) and sorghum (SFS, density = .36 kg/liter) in finishing diets supplemented with or without .75% sodium bicarbonate (BICARB). No interactions between BICARB and grain type proved to be significant. Supplemental BICARB increased ADG 5.9% (P less than .10) and DMI 4.6% (P less than .05) but did not influence (P greater than .10) the NE value of the diet. Supplemental BICARB increased ruminal pH (P less than .01) and total tract fiber digestion (P less than .05). Differences in ruminal and total tract OM, starch, and N digestion were small (P greater than .10). Replacing SFC with SFS decreased (P less than .05) ADG 6.1% and increased (P less than .01) DMI/gain 9.7%. Corresponding diet NEm and NEg were decreased (P less than .01) 7.0 and 9.3%, respectively. Ruminal digestion of OM and starch tended to be lower (11.8 and 7.2%, respectively, P less than .10) for SFS. Ruminal degradation of feed N was 31% lower (P less than .05) for the SFS diets. Total tract digestibility of OM, N, DE, and ME were 3.3, 10.8, 4.4, and 5.5% lower (P less than .05), respectively, for the SFS vs SFC diets. In conclusion, 1) SFS had 92% the NEm of SFC; 2) differences in total tract starch digestibility were small and cannot explain the higher feeding value of SFC; 3) the low ruminal degradation of sorghum N (roughly 20%) should be considered in diet formulation to avoid a deficit in ruminally available N; and 4) .75% BICARB supplementation increased DMI and ADG of cattle fed highly processed grain-based diets.