Biomedical subjects

E C Titgemeyer

Publications and source records attributed to E C Titgemeyer.

At least 55 records · Page 3Linked to original sources

PubMed1999

Effects of different supplemental sugars and starch fed in combination with degradable intake protein on low-quality forage use by beef steers.

Twenty ruminally fistulated steers (Exp. 1, 448 kg and Exp. 2, 450 kg) were used in two consecutive randomized complete block experiments with five treatments in each experiment. The purpose was to evaluate the impact of feeding different supplemental sugars or starch in combination with supplemental degradable intake protein (DIP) on the utilization of low-quality tallgrass-prairie hay. In Exp. 1, steers were given ad libitum access to forage and, except for the negative control (NC), received a limited supply (insufficient to maximize forage use) of supplemental DIP (.031% BW/d, DM basis). In addition to the NC, this experiment included four supplementation treatments in which one of four carbohydrate (CHO) sources (starch, glucose, fructose, or sucrose) was fed at .30% BW of DM/d. In Exp. 2, the treatment structure was identical except that the supplemental DIP level (.122% BW, DM basis) was near the level needed to maximize forage use. Forage OM intake (FOMI) was not affected (P> or =.26) by supplementation in Exp. 1 but was increased (P = .05) in Exp. 2. However, no difference (P> or =.46) in FOMI occurred among CHO sources in either experiment. Total OM and digestible OM intakes were increased (P<.01) by supplementation in both experiments. In Exp. 1, no difference (P>.26) in OM digestion (OMD) occurred among treatments. In Exp. 2, supplementation increased (P<.01) OMD. Additionally, sugars yielded a higher (P = .04) OMD than starch, and the monosaccharides yielded a higher (P = .02) OMD than sucrose. In Exp. 1, NDF digestion (NDFD) was decreased (P = .02) by supplementation, but no differences (P> or =.21) occurred among CHO sources. In Exp. 2, NDFD was increased (P = .03) by supplementation. Additionally, sugars led to higher (P = .05) NDFD than starch, and the monosaccharides led to higher (P = .03) NDFD than sucrose. In both experiments, discernible patterns were observable with regard to the effects of supplementation and type of supplemental CHO on ruminal fermentation characteristics. In conclusion, even though some consistency in fermentation profiles for different carbohydrate sources was evident in both experiments, forage intake and digestion responses were not consistent across experiments. This raises the possibility that carbohydrate source may interact with the amount of supplemental DIP fed and, as such, deserves additional investigation.

Animal Feed↗

PubMed1999

Effects of level and source of carbohydrate and level of degradable intake protein on intake and digestion of low-quality tallgrass-prairie hay by beef steers.

Ruminally fistulated steers (n = 13; 263 kg) were used in an incomplete Latin square with 13 treatments and four periods to evaluate the effects of level and source of supplemental carbohydrate (CHO) and level of degradable intake protein (DIP) on the utilization of low-quality, tallgrass-prairie hay. Steers were given ad libitum access to forage (5.7% CP, 2.6% DIP, and 74.9% NDF). The supplementation treatments were fashioned as a 2x3x2 factorial arrangement plus a negative control (NC; no supplement). The factors included two DIP levels (.031 and .122% BW) and three CHO sources (starch, glucose, and fiber) fed at two levels (.15 and .30% BW) within each level of DIP supplementation. The effect of supplementation on forage OM intake (FOMI) was dependent (P<.01) on level and source of CHO and level of DIP fed. When DIP was low, forage, total, and digestible OM intakes were generally greater for the starch treatment than for the nonstarch treatments. However, when the DIP level was high, intakes were greater for the nonstarch (i.e., fiber and glucose) treatments. Generally, FOMI decreased (P<.01) when more supplemental CHO was provided. Supplementation typically increased fiber digestion, but the response was dependent (P<.01) on level and source of CHO and level of DIP. Generally, supplements with low levels of CHO improved NDF digestion (NDFD). However, supplements with the high level of CHO decreased NDFD, except for fiber at the high level of DIP. Organic matter digestion was increased by supplementation, but the impact of increasing CHO was dependent (P<.01) on source of CHO and level of DIP. Supplementation treatments had significant impact on ruminal pH, NH3 N, and the total concentration of organic acids as well as their relative proportions. In conclusion, supplemental DIP enhanced the use of low-quality forage; however, the impact of supplemental CHO on low-quality forage use was dependent on source and level of CHO offered, as well as the level of DIP provided.

Animals↗

PubMed1999

Effects of ruminal administration of supplemental degradable intake protein and starch on utilization of low-quality warm-season grass hay by beef steers.

Hereford x Angus steers were used in a 13-treatment, four-period, incomplete Latin square design to examine the effects of starch and degradable intake protein (DIP) supplements on forage utilization and ruminal function. Steers were given ad libitum access to low-quality hay (4.9% CP) and were not supplemented (NS) or received different amounts of starch (cornstarch grits; 0, .15, and .3% of initial BW) and DIP (Na-caseinate; .03, .06, .09, and .12% of initial BW) administered via ruminal fistulae in a 3 x 4 factorial arrangement of treatments. Supplemented steers consumed more (P < .01) forage OM, total OM, NDF, and digestible OM (DOM) than NS steers. Forage OM, total OM, NDF, and DOM intakes increased linearly (P < .01) as the amount of supplemental DIP increased. The addition of starch to supplements linearly decreased ( P < .01) the intake of forage OM, NDF, and DOM. The digestion of DM, OM, and NDF increased linearly (P < .01) with supplemental DIP and decreased linearly (P < or = .06) with supplemental starch. Particulate and liquid passages generally increased with DIP; however, starch level influenced the nature of the response (P = .03 and .06, respectively). Similarly, ruminal acid detergent-insoluble ash content generally decreased as starch increased, but the effect was dependent on DIP level (P < .01). Supplementation increased (P < .01) ruminal NH3 and total VFA and decreased (P < .01) ruminal pH relative to NS. All treatments supported average pH values in a range (6.3 to 6.7) unlikely to inhibit fibrolytic bacteria. Ruminal NH3 concentration increased quadratically (P = .03) with DIP and decreased linearly (P = .02) with starch. As DIP increased, total VFA concentration increased linearly (P = .02). Providing supplemental DIP to steers fed low-quality forage increased OM intake and digestion, whereas addition of starch to supplements decreased forage intake and digestion.

Animal Feed↗

PubMed1998

Standardization of in situ techniques for ruminant feedstuff evaluation.

Over the last two decades, in situ techniques have been used extensively for measuring ruminal degradation of feedstuffs. Current predictive models put renewed emphasis on the need for quantitative information regarding rates and extents of ruminal degradation. However, in situ techniques suffer from tremendous variation, both within and among laboratories. A considerable number of studies have evaluated the influence of various factors on in situ-derived estimates of ruminal degradation. Factors that should be addressed in a standardized procedure include bag and sample sizes; bag material and pore size; sample processing; animal diet, feeding level, and frequency; bag insertion and removal procedures; location of bags within the rumen and containment procedures for the bags; rinsing procedures; microbial correction; incubation times; mathematical models; and numbers of replicate animals, days, and bags required to obtain repeatable estimates of ruminal degradation. Several recommendations that should increase the precision of in situ measurements are presented. Currently, the lack of standardization in rinsing techniques and the failure or inability to correct for microbial contamination of in situ residues seem to be the major sources of variability with in situ procedures.

Animal Feed↗

PubMed1998

Influence of dietary lysine on growth performance and carcass characteristics of late-finishing gilts.

We conducted two experiments evaluating the lysine requirement of 91- to 113-kg gilts. Gilts (PIC L326 x C-22) with initial body weights of 42 (Exp. 1) or 39 kg (Exp. 2) were blocked by weight in a randomized complete block design. Experiment 1 included 105 gilts, with seven gilts per pen and five replications (pens) per treatment. Experiment 2 included 125 gilts, with eight gilts per pen and four replications (pens) per treatment. Gilts were fed a corn-soybean meal diet (no crystalline lysine) containing 1.0% total lysine from 39 to 68 kg and .80% total lysine from 68 to 91 kg. In Exp. 1, when the average weight of gilts within a block reached 91 kg, gilts were fed corn-soybean meal diets containing .40, .55, or .70% total lysine. Increasing dietary lysine increased (linear, P < .05) ADG, daily lysine intake (11.3, 15.1, and 19.8 g/d), gain/feed, plasma urea N, and carcass lean percentage but decreased 10th rib fat depth. Because of the linear responses in Exp. 1, Exp. 2 was conducted with corn-soybean meal diets containing .60, .70, .80, or .90% total lysine. Increasing total dietary lysine had no effect on ADG, gain/feed, 10th rib fat depth, or carcass lean percentage (P > .10). Daily lysine intake increased (linear, P < .01) with increasing dietary lysine (18.1, 21.1, 23.9, 26.5 g/d). Based on these results, the total dietary lysine requirement for 91- to 113-kg gilts is approximately .60% total lysine, which corresponds to approximately 18 g/d lysine intake.

Animal Nutritional Physiological Phenomena↗

PubMed1998

Performance, digestion, and mastication efficiency of Holstein steers fed whole or processed corn in limit- or full-fed growing-finishing systems.

We conducted two trials to examine the effects of restricted vs full feeding and of grain processing method on feedlot performance, digestion, and mastication efficiency by Holstein steers in different growing-finishing systems. In Trial 1, 272 Holstein steers (177 +/- 9.98 kg) were blocked by weight and assigned to growing phase diets based on corn silage (SIL), steam-flaked corn that was either limit-fed (SFLF) or full-fed (SFFF), or whole corn that was limit-fed (WCLF) or full-fed (WCFF). Limit-fed steers were fed at levels predicted to allow daily gain of 1 kg/d. On d 112, all steers were switched to WCFF or SFFF diets until the mean BW of each treatment group was 545 kg. Overall, steers fed WCLF and SFLF during the growing phase and finished on SF were 8.1 and 6.6% more efficient at converting dietary ME to gain (P = .02 and .04, respectively) than steers in the SFFF group. In Trial 2, three ruminally and duodenally cannulated Holstein steers were fed whole (WC) and rolled corn (RC) diets at FF and LF intake in an incomplete replicated 2 x 2 switchback design. Ad libitum access to feed resulted in higher (P = .02) ruminal starch digestibility than did limit-feeding, and calves had higher total tract DM (P = .05) and starch (P = .03) digestion at the heavier BW. Limit-feeding whole corn resulted in increased particle size of masticate (P = .06) compared with full-feeding whole corn. Because of apparent differences in mastication efficiency between limit-fed and full-fed calves, grain processing method during periods of restriction and compensatory growth may be important considerations for managing growth in systems that incorporate limit-feeding.

Animal Feed↗

PubMed1998

Influence of dietary total sulfur amino acids and methionine on growth performance and carcass characteristics of finishing gilts.

We conducted three experiments to determine the sulfur amino acid (SAA) and methionine requirements of finishing gilts. Gilts (PIC Line 326 x C-15, Exp. 1; Line 326 x C-22, Exp. 2 and 3) were blocked by initial weight in randomized complete block designs. In Exp. 1, 64 gilts (initially 54 kg) were fed diets containing either .56 or .44% apparent digestible lysine with increasing SAA levels (63, 70, and 77% of apparent digestible lysine) in a 2 x 3 factorial. A lysine x SAA interaction (P < .10) was observed for ADG and ADFI. Increasing SAA:lysine ratios from 63 to 70% in diets containing .56% apparent digestible lysine increased ADG and ADFI; however, increasing the SAA:lysine ratio in diets containing .44% apparent digestible lysine decreased ADG and ADFI. Pigs fed .56% apparent digestible lysine had higher (P < .05) ADG and gain:feed ratio (G/F) and lower 10th rib fat depth than pigs fed .44% apparent digestible lysine. Increasing the SAA:lysine ratio had no effect on G/F or carcass characteristics. In Exp. 2, 80 gilts (initially 74 kg) were fed diets containing .225, .25, .275, .30, or .325% apparent digestible SAA (45, 50, 55, 60, or 65% of .50% apparent digestible lysine, respectively). Increasing SAA concentrations decreased ADG and G/F (linear, P < .06). In Exp. 3, 105 gilts (initially 72 kg) were fed diets containing .20% apparent digestible cystine and .10, .125, or .15% apparent digestible methionine (20, 25, or 30% of .50% apparent digestible lysine). Increasing digestible methionine increased ADG, ADFI, plasma methionine concentrations (linear, P < .01), and G/F (quadratic, P < .03). The greatest increases in ADG and G/F were observed when apparent digestible methionine was increased from .10 to .125%. Based on these results, the apparent digestible methionine requirement is no greater than 25% of apparent digestible lysine, in diets containing excess cystine. This equates to an apparent digestible SAA:lysine ratio that is no greater than 50%.

Adipose Tissue↗

PubMed1997

Serum concentrations of trenbolone-17 beta and estradiol-17 beta and performance of heifers treated with trenbolone acetate, melengestrol acetate, or estradiol-17 beta.

The effects of the growth-promoting steroids estradiol-17 beta (E2), trenbolone acetate (TBA), and melengestrol acetate (MGA) in heifers on serum concentrations of E2 and trenbolone-17 beta (TBOH) were examined. Feed intake and growth performance were also measured. Serum concentrations of E2 and TBOH were measured on d 0, 1, 3, 5, 7, 13, 21, 28, 42, 56, 84, 112, and 140 in finishing heifers administered the following treatments: 1) control; 2) MGA, .5 mg per heifer daily; 3) Revalor-H (140 mg TBA + 14 mg E2); 4) Revalor-H + MGA; 5) Finaplix-H (200 mg TBA); and 6) Finaplix-H + MGA. Revalor-H implantation (Treatments 3 and 4) increased (P < .05) serum E2 concentrations; peak concentrations (67.5 pg/mL) occurred between d 21 and 56. Feeding MGA (Treatment 4) had no effect (P > .05) on this increase in serum E2 concentrations (63.3 pg/mL). From d 84 until d 140, serum E2 was greater (P < .05) for the Revalor-H treatment (average of 19 pg/mL) than for the control (7 pg/mL) or Finaplix-H treatments (6.5 pg/mL). Serum E2 concentrations increased numerically two- to threefold from d 56 to 140 in controls fed MGA, compared with controls not fed MGA. There was the expected increase in serum TBOH concentrations after TBA implantation in the Revalor-H and Finaplix-H treatments; concentrations were similar (P > .05) for Revalor-H (221 pg/mL) and Finaplix-H (280 pg/mL). After d 56, serum TBOH concentrations decreased in both treatments to 10 and 20% of these concentrations, respectively. Feeding MGA increased serum TBOH (P < .05). Dry matter intake by heifers did not differ among treatments. Feeding of MGA improved gains (P = .12) and efficiencies (P < .01) in nonimplanted heifers and had no effect (P > .4) on gains or efficiencies in Finaplix-implanted heifers.

Anabolic Agents↗

PubMed1997

Effects of dietary nitrogen source and concentration in high-grain diets on finishing steer performance and nutrient digestion.

Two experiments were designed to evaluate dietary N source and concentration on finishing steer performance and nutrient digestion. In Exp. 1, 100 steers were used in a randomized complete block design experiment with 2 x 2 + 1 factorially arranged treatments. Diets contained 1.93 or 2.24% N supplemented by urea or soybean meal (SBM), or 2.24% N supplemented by cottonseed meal (CSM). Steers fed SBM-supplemented diets gained 13% faster (P < .01) and were 9% (P < .01) more efficient converting feed to gain than steers receiving urea. Steers fed diets containing 2.24% N were 4% (P < .05) more efficient than those fed diets containing 1.93% N. Steers fed CSM-supplemented diets gained 6% (P < .10) less efficiently than steers receiving SBM. Increasing dietary N with urea from 1.93 to 2.24% decreased carcass weights 3%, whereas increasing dietary N with SBM increased carcass weights 3%. Carcass-adjusted gains were reduced 8% by increasing urea from .9 to 1.5% but increased 7% by increasing SBM from 6.1 to 10.5% of DM. In Exp. 2, four ruminally and duodenally cannulated steers (390 kg) were used in a 4 x 4 Latin square design experiment to evaluate urea and SBM supplementation on digestion. Diets contained no supplemental N, 1.84% N with urea or SBM as the supplement, or 2.16% N with SBM as the supplement. Total tract starch digestion, duodenal microbial N flow, and efficiency of microbial protein synthesis in the rumen were higher (P < .10) in steers fed SBM- than in those fed urea-supplemented diets. Supplementation with SBM increased metabolizable protein supply and dietary energy utilization.

Animals↗

PubMed1997

Effect of degradable and escape protein and roughage type on performance and carcass characteristics of finishing yearling steers.

We evaluated protein sources for finishing steers in two randomized complete block design experiments. Experiment 1 used 144 steers (334 kg) with 2 x 3 factorially arranged treatments. Basal diets contained .9% urea or 5.6% soybean meal (SBM) and were either not supplemented or supplemented with additional protein (2%) from blood meal-corn gluten meal (BMCG) or SBM. Steers fed urea-containing diets consumed 4.6% (P < .10) more feed than those fed SBM-supplemented basal diets. On the basis of carcass weights, steers fed diets containing SBM as the basal protein source were 3.8% (P < .10) more efficient than those fed urea-containing diets; supplying additional SBM improved gain efficiency (G/F) 4.3% (P < .10) compared with BMCG. In Exp. 2, 384 steers (367 kg) were fed diets containing 1.0% urea (DM basis) and 10% roughage as either sorghum silage (four diets) or alfalfa hay (two diets). Additional protein was either not provided or provided (2%) as SBM, sunflower meal (SFM), or a 50:50 (N basis) SBM:SFM blend in silage-containing diets; for diets containing alfalfa, additional protein was either not provided or provided (2%) as SBM. Averaged across roughage source, added SBM tended (P = .16) to increase ADG. Dressing percent decreased (P = .09) with added SBM but was higher (P = .04) with alfalfa as roughage source. Feeding alfalfa vs sorghum silage as the roughage source increased carcass adjusted ADG 4.3% (P = .06) and G/F 4.8% (P = .02). Supplementing high-grain diets with SBM enhanced diet utilization, but BMCG was of little value.

Aging↗

PubMed1997

Effect of amino acid supplementation on whole-body protein turnover in Holstein steers.

We used the [15N]glycine single-dose urea end-product technique to measure whole-body protein turnover in six Holstein steers (250 +/- 18 kg). Steers were implanted with Revalor-S and continuously infused abomasally with water (4 L/d) or amino acids (AA; in 4 L/d water) in a crossover experiment (two 14-d periods). The AA infusion contained the following (g/d): lysine (5.3), methionine (3.3), threonine (3.2), tryptophan (1.0), histidine (2.1), and arginine (5.5). Steers were fed a diet containing 85% rolled corn, 10% prairie hay, and 1.1% urea (DM basis) at 2.16% of body weight. Nitrogen retention tended (P = .15) to increase with AA infusion, from 27.9 to 32.9 g N/d. Amino acid infusion numerically increased whole-body protein turnover from 168.6 to 183.2 g N/d, protein synthesis from 152.6 to 169.3 g N/ d, and protein degradation from 124.7 to 136.4 g N/d. Enhanced protein accretion may have resulted from a larger increase in protein synthesis than in degradation. The tendency for increased N retention is interpreted to suggest that the implanted, lightweight Holstein steers fed a corn-urea diet in our study were able to respond to AA supplementation, suggesting that at least one of the infused AA was limiting in the basal diet. Protein turnover data suggest that cattle, like other animals, may increase protein synthesis and protein degradation in response to supplementation with limiting AA. The [15N]glycine single-dose urea end-product technique for measuring whole-body protein turnover in cattle may be useful.

Amino Acids↗

PubMed1997

Sulfur amino acid utilization by growing steers.

Studies were conducted to quantify sulfur amino acid requirements of growing steers. In Exp. 1, six steers (160 kg) were used to determine the methionine requirement in the presence of excess L-Cys. Treatments were abomasal infusion of water only or water plus 2, 4, 6, 8, or 10g/d of L-Met. Steers were fed 2.4 kg/d DM of a diet designed to minimize basal Met supply to the small intestine. Continuous ruminal infusions of VFA (506 g/d) and abomasal infusions of dextrose (150 g/d) increased energy supply to the abomasum. Break-point analysis estimated maximal N retention at 5.8 g/d supplemental L-Met. The basal absorbable Met supply was 2.1 g/d; therefore, the total Met requirement was 7.9 g/d when excess Cys was available. In Exp. 2, five steers (195 kg) were used to determine the efficiency of transsulfuration. Treatments were abomasal infusion of water only or water plus 1.62 or 3.25 g/d L-Cys or 2 o4 g/d L-Met. Diet and infusions were similar to those on Exp. 1, except the amino acid mixture was devoid of Cys and all steers received 4 g/d L-Met to make total sulfur amino acids, but not necessarily Met, limiting. Nitrogen retention increased in response to Met but not Cys infusion and was maximized at 2 g/d supplemental L-Met; thus, the total Met requirement was near 8.4 g/d when the Cys supply was 2.1 g/d. Supplemental Cys did not spare Met, suggesting that nonprotein functions of Met may be quantitatively important.

Abomasum↗

PubMed1997

Protein requirements of growing steers limit-fed corn-based diets.

In Exp. 1, six steers (254 kg) were used in a 6 x 4 incomplete Latin square to determine the effects of solvent-extracted soybean meal alone or in combination with rumen-protected methionine and lysine on N balance in steers limit-fed a high-corn diet to gain 1.1 kg/d. The basal diet contained (DM basis) 80% rolled corn, 15% alfalfa, and .9% urea (13.9% CP), and 2 or 4% soybean meal replaced corn to give CP concentrations of 14.8 and 15.6%, respectively. Each diet was fed with and without 5 g/d of Smartamine-ML (.75 and 2.0 g of rumen-protected methionine and lysine, respectively). Nitrogen retention increased linearly (P = .09) with level of soybean meal. Rumen-protected methionine and lysine had no effect on N balance. In Exp. 2, seven steers (233 kg) were used in a 7 x 4 incomplete Latin square experiment to investigate optimal levels and sources of CP for steers limit-fed to gain 1 kg/d. Treatments included a negative-control diet (urea; 11.7% CP) and six diets containing either 13.5, 15.4, or 17.2% CP with either solvent-extracted or expeller-processed soybean meal. Diets provided 75, 87.5, 100, or 112.5% of estimated CP requirement for a gain of 1 kg/d. The basal diet contained 83% rolled corn, 15% alfalfa, and .2% urea. Nitrogen retention increased linearly (P = .006) with soybean meal addition, and no differences were observed between CP sources. The CP system underpredicted the protein requirements of limit-fed steers under our conditions.

Animals↗

PubMed1997

Free amino acid supplementation to steers: effects on ruminal fermentation and performance.

Three studies were conducted to evaluate amino acid utilization by cattle. In Exp. 1, five steers (580 kg) were fed 86% rolled corn diets with mixtures of amino acids containing up to 6 g/d DL-Met, 24 g/d L-Lys, 6 g/d L-Thr, and 3 g/d L-Trp. Treatments had little effect on ruminal fermentation, diet digestibility, N flow to the duodenum, or microbial efficiency. Ruminal concentrations of Met and Lys increased linearly (P < .05) with amino acid supplementation, whereas Thr responded quadratically, and Trp was not altered. In Exp. 2, four steers (414 kg) were used to measure effects of dietary monensin or laidlomycin propionate in high-grain diets supplemented with amino acids. Ionophores had no significant effect on ruminal fermentation or outflows of amino acids from the rumen. In Exp. 3, 100 steers (287 kg initial BW) were fed diets containing 1% of a nonprotein N source. Treatments were 1) no supplemental N (UREA), 2) UREA plus soybean meal (SBM), 3) UREA plus 2 g/d DL-Met, 8 g/d L-Lys, 2 g/d L-Thr, and 1 g/d L-Trp, or 4) UREA plus 4 g/d DL-Met, 16 g/d L-Lys, 4 g/d L-Thr, and 2 g/d L-Trp. During the growing period (diets based on whole-plant milo silage), gains were higher for SBM-supplemented steers than for UREA steers and intermediate for steers supplemented with amino acids. Few significant differences in performance were observed among treatments during the finishing phase (diets based on dry-rolled corn) or for the entire experiment, but cattle fed SBM or amino acids tended to be fatter and have better marbling scores and quality grades. Amino acids did not greatly alter ruminal fermentation or cattle performance.

Amino Acids↗

PubMed1997

Effect of increasing proportion of supplemental nitrogen from urea on intake and utilization of low-quality, tallgrass-prairie forage by beef steers.

Five Angus x Hereford steers with ruminal and duodenal fistulas were used in a 5 x 5 Latin square to determine effects of increasing the proportion of urea in supplemental degradable intake protein (DIP) on intake, fermentation, and digestion. Steers had ad libitum access to low-quality, tallgrass-prairie forage (2.4% CP, 76% NDF). Supplemental DIP (380 g/d) was from sodium caseinate and(or) urea and was balanced with cornstarch to provide a final supplement (approximately 939 g DM/d) that contained 40% CP. The percentages of supplemental DIP from urea were 0, 25, 50, 75, and 100%. Intake of forage OM was not affected (P > or = .30) by urea level. Ruminal and total tract digestibilities of OM and NDF generally responded in a quadratic manner (P < or = .09) to increasing urea, with the lowest values observed at the highest urea level. As a result, digestible OM intake (DOMI) declined (linear, P = .03) with increasing proportions of urea and tended (quadratic, P = .14) to exhibit the largest proportional decline at the highest urea level. The effects of increasing urea on duodenal N flow, microbial efficiency, ruminal contents, and fluid dilution rate were minimal. Ruminal ammonia N and molar percent acetate increased linearly (P < or = .02), whereas most other VFA (except propionate) decreased (P < or = .05) with increasing urea. In conclusion, although forage OM intake was not altered, OM digestion, NDF digestion, and DOMI were lowest when all supplemental DIP was supplied as urea. Changes in fermentation characteristics reflected the change in source of available nitrogen.

Ammonia↗

PubMed1997

Urea in dry-rolled corn diets: finishing steer performance, nutrient digestion, and microbial protein production.

In Exp. 1, 88 yearling steers (332 kg) were fed dry-rolled corn finishing diets to evaluate effects of dietary urea level on performance and carcass characteristics. Diets contained 0, .5, 1.0, or 1.5% urea (DM basis), which supplied all supplemental N, and 10% chopped prairie hay. Gains (P = .10) and gain efficiency (G/F; P < .05) were increased by .5% urea, with little improvement by additional urea. Regression analysis estimated optimal dietary urea at .9% of DM for ADG and G/F. Fat thickness (P < .05) and yield grade (P < .10) increased linearly with dietary urea level. In Exp. 2, four ruminally and duodenally cannulated steers (557 kg) were fed the diets used in Exp. 1 to evaluate effects of dietary urea on site and extent of digestion. True ruminal OM and starch digestion were increased 25 and 37%, respectively, by .5% urea, but higher urea levels did not differ from .5%. Flows of total N and microbial N to the duodenum were not affected by urea level. In Exp. 3, 100 yearling steers (347 kg) were fed dry-rolled corn finishing diets that contained 10% alfalfa hay as the dietary roughage to evaluate effects of dietary urea level on performance and carcass characteristics. Urea levels were 0, .35, .70, 1.05, or 1.40% urea (DM basis), with no other supplemental N provided. Dry matter intake (P = .10), ADG (P < .05), and G/F (P < .05) increased with intermediate concentrations of urea but decreased with the highest concentration. Regression analysis indicated that the optimal dietary urea level was .5% of DM for ADG and G/F. Urea increased dietary energy utilization but not metabolizable protein supply.

Animals↗

PubMed1997

Intake, digestion, and nitrogen utilization by sheep fed tropical legumes with contrasting tannin concentration and astringency.

We conducted an experiment to determine the effects of concentration and astringency of extractable and bound condensed tannins (CT) in tropical legumes on intake, digestibility, and nitrogen (N) utilization by sheep. The test legumes (Desmodium ovalifolium and Flemingia macrophylla) had similar concentrations of extractable CT (90 g/kg DM) but different concentrations of bound CT and astringency of tannins. Chopped, sun-dried forage of each legume was sprayed with either water (control) or polyethylene glycol (PEG, 35 g/kg of DM) to bind extractable CT and fed daily (26 g/kg BW) to eight sheep with ruminal and duodenal cannulas. The sheep also received starch-extracted cassava meal intraruminally (4 g/kg BW) as a constant source of readily fermentable carbohydrates. Intake of the two legumes was not different (P > .05), but it increased an average of 10% (P < .01) when extractable CT were reduced from 90 to 50 g/kg of DM with PEG. Ruminal and total tract digestibilities of OM, NDF, and ADF were greater (P < .01) with D. ovalifolium than with F. macrophylla and increased for both legumes with the addition of PEG. Greater (P < .01) N flow to the duodenum, N absorbed from the intestine, and fecal N were observed with F. macrophylla than with D. ovalifolium. Extraction of CT with PEG resulted in less (P < .05) ruminal escape protein and less (P < .01) fecal N with both legumes, but apparent postruminal N digestion was not affected. Changes in the concentration of extractable CT in tropical legumes can significantly affect forage intake, digestion, and N utilization by sheep.

Animals↗

PubMed1997

In vitro determination of ruminal protein degradability of alfalfa and prairie hay via a commercial protease in the presence or absence of cellulase or driselase.

Ruminal protein degradation of alfalfa (2.62% N, 49.6% NDF, and in vivo undegradable intake protein [UIP] = 16.4% of CP) and prairie hay (.88% N, 69.4% NDF, and in vivo UIP = 44.5% of CP) was estimated using the Streptomyces griseus protease (SGP) in vitro method with or without pretreatment with two carbohydrases: cellulase from Penicillium funiculosum or driselase from Basidiomycetes. Driselase is a broad-spectrum carbohydrase. Incubating forage samples for 48 h with cellulase or driselase at a concentration of 800 mg/g per g of hay nearly maximized ADF and NDF disappearances. This concentration and incubation time then were used to pretreat hay samples. A 2-h pretreatment was included to evaluate the potential for reducing the analysis time. Other sets of samples were or were not pretreated with acetate buffer alone. Following pretreatment, samples were subjected to SGP for .25, .5, 1, 2, 4, 8, 12, 24, and 48 h. Pretreatment altered the sizes of protein pools and their degradation rates. When the UIP contents of the forages were estimated using SGP and a single-pool, first-order, kinetic model, cellulase (48 h) or driselase pretreatments yielded UIP predictions that were more similar to in vivo values. Some carbohydrase and protease combinations also yielded single time-point estimates of UIP that were similar to in vivo values. Similarly, when sufficient time was permitted for protease incubation, single time-point estimates derived from protease alone were similar to in vivo values.

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