Biomedical subjects

P A Ludden

Publications and source records attributed to P A Ludden.

16 recordsLinked to original sources

PubMed2005

Effect of restricted forage intake on ruminal disappearance of bromegrass hay and a blood meal, feather meal, and fish meal supplement.

Two experiments were conducted to determine in situ disappearance of bromegrass hay and a ruminally undegraded protein (RUP) supplement in beef cattle fed restricted amounts of forage. Six Angus crossbred cattle (BW = 589 +/- 44.4 kg; three steers and three heifers) fitted with ruminal cannulas were fed chopped (2.54 cm) bromegrass hay (8.9% CP) at one of three percentages of maintenance intake (30, 55, or 80%; one steer and one heifer per treatment). In both experiments, the cattle were allowed 7 d for diet adaptation followed by 3 d of sample collection. In Exp 1, in situ bags (50 microm pore size) containing 4.1 g of brome-grass hay (OM basis) were inserted into the rumen and subsequently removed at 3, 6, 9, 12, 15, 18, 24, 36, and 48 h after insertion. Nonlinear regression models were used to determine the rapidly solubilized protein Fraction A, the potentially ruminal degradable protein Fraction B, the ruminally undegraded protein Fraction C, and protein degradation rate. Intake level did not affect (P = 0.15 to 0.95) forage protein remaining after in situ incubation or Fractions A, B, and C; however, effective ruminal degradation of hay protein tended to increase quadratically (P = 0.12) as forage intake increased. In Exp 2, 4.2 g (OM basis) of an RUP supplement (6.8% porcine blood meal, 24.5% hydrolyzed feather meal, and 68.7% menhaden fish meal) formulated to provide equal amounts of metabolizable protein across all levels of hay consumption was evaluated in a similar manner as in Exp 1. The undegraded protein fraction of the supplement did not differ (P = 0.16 to 0.74) across treatments at 3, 6, 9, and 18 h; however, increasing forage intake resulted in a linear increase (P < or = 0.06) in undegraded protein remaining at 12, 15, 24, 36, and 48 h. Dietary treatment had no affect (P = 0.30) on protein Fractions A, B, or C; however, protein degradation rate of the supplement decreased linearly (P = 0.03) as forage intake increased. Therefore, effective ruminal degradation of the supplement decreased linearly (P = 0.01) from 50.8 to 40.9% as forage intake increased from 30 to 80% of maintenance. Corresponding estimates of supplement RUP were 49.2, 56.5, and 59.1% for the 30, 55, and 80% of maintenance intake treatments, respectively. Restricting dietary intake can decrease the quantity of dietary protein that escapes ruminal degradation. Tabular estimates of RUP may not be appropriate for formulating diets to balance metabolizable protein in beef cattle consuming limited quantities of forage.

Animal Feed↗

PubMed2005

Supplementing a ruminally undegradable protein supplement to maintain essential amino acid supply to the small intestine when forage intake is restricted in beef cattle.

Twelve Angus crossbred cattle (eight heifers and four steers; average initial BW = 594 +/- 44.4 kg) fitted with ruminal and duodenal cannulas and fed restricted amounts of forage plus a ruminally undegradable protein (RUP) supplement were used in a triplicated 4 x 4 Latin square design experiment to determine intestinal supply of essential AA. Cattle were fed four different levels of chopped (2.54 cm) bromegrass hay (11.4% CP, 57% NDF; OM basis): 30, 55, 80, or 105% of the forage intake required for maintenance. Cattle fed below maintenance were given specified quantities of a RUP supplement (6.8% porcine blood meal, 24.5% hydrolyzed feather meal, and 68.7% menhaden fish meal; DM basis) designed to provide duodenal essential AA flow equal to that of cattle fed forage at 105% of maintenance. Experimental periods lasted 21 d (17 d of adaptation and 4 d of sampling). Total OM intake and duodenal OM flow increased linearly (P < 0.001) as cattle consumed more forage; however, OM truly digested in the rumen (% of intake) did not change (P = 0.43) as intake increased. True ruminal N degradation (% of intake) tended (P = 0.07) to increase linearly, and true ruminal N degradation (g/d) decreased quadratically (P = 0.02) as intake increased from 30 to 105%. Duodenal N flow was equal (P = 0.33) across intake levels, even though microbial N flow increased linearly (P < 0.001) as forage OM intake increased. Total and individual essential AA intake decreased (cubic; P < 0.001) as forage intake increased because the supply of nonammonia, nonmicrobial N flow from RUP was decreased (linear; P < 0.001) by design. Total duodenal flow of essential AA did not differ (P = 0.39) across these levels of forage intake. Although the profile of essential AA reaching the duodenum differed (P < or = 0.02) for all 10 essential AA, the range of each essential AA as a proportion of total essential AA was low (11.1 to 11.2% of total essential AA for phenylalanine to 12.3 to 14.3% of total essential AA for lysine). Duodenal essential AA flow did not differ (P = 0.10 to 0.65) with forage intake level for eight of the 10 essential AA. Duodenal flow of arginine decreased linearly (P = 0.01), whereas duodenal flow of tryptophan increased linearly (P = 0.002) as forage intake increased from 30 to 105% of maintenance. Balancing intestinal essential AA supply in beef cattle can be accomplished by varying intake of a RUP supplement.

Amino Acids↗

PubMed2004

Technical note: a procedure for the preparation and quantitative analysis of samples for titanium dioxide.

A procedure was developed for the rapid analysis of titanium dioxide (TiO2) concentrations in feed and fecal samples. Samples were digested in concentrated H2SO4 for 2 h, followed by addition of 30% H2O2, and absorbance was measured at 410 nm. Standards were prepared by spiking blanks with increasing amounts of TiO2, resulting in a linear standard curve. Complete analysis using this procedure can typically be accomplished within 4.5 h. This procedure was compared to a previously published dry-ash procedure for the analysis of TiO2 in bovine fecal samples. Three sources of OM devoid of TiO2 (a forage sample, a bovine fecal sample without Cr2O3, and a bovine fecal sample containing Cr2O3) were spiked with graded amounts (0, 2, 4, 6, 8, or 10 mg) of TiO2. With our procedure, TiO2 recoveries averaged 96.7, 97.5, and 98.5%, for the three OM sources, respectively, vs. 74.3, 83.8, and 53.1% for the same samples analyzed using the dry-ash method. These results suggest that our procedure is a rapid and accurate alternative to dry-ash procedures for the determination of TiO2.

Animal Feed↗

PubMed2004

Site and extent of digestion and amino acid flow to the small intestine in beef cattle consuming limited amounts of forage.

Eight Angus x Gelbvieh heifers (445 +/- 74.5 kg) fitted with ruminal and duodenal cannulas were used in a 4 x 4 Latin square double double-crossover designed experiment to assess the effect of restricted forage intake on site and extent of digestion and flow of essential AA amino acids to the small intestine. Heifers were fed chopped (2.54 cm) bromegrass hay (9.2% CP, 64% NDF on an OM basis) at one of four percentages of maintenance (30, 60, 90, and 120%). Experimental periods were 21 d in length, with 17 d of adaptation followed by 4 d of intensive sample collection, after which maintenance requirements and subsequent level of intake were adjusted for BW change. True ruminal OM, NDF, and N digestion (g/d) decreased linearly (P < 0.001) with decreasing forage intake. When expressed as a percentage of OM intake, true ruminal OM and N digestibility were not affected (P = 0.23 to 0.87), whereas ruminal NDF digestibility tended to increase (P = 0.09) as forage intake decreased. Total and microbial essential amino acid flow to the duodenum decreased linearly (P = 0.001) from 496.1 to 132.1 g/d and 329.1 to 96.0 g/d, as intake decreased from 120 to 30% of maintenance intake, respectively. Although the profile of individual essential amino acids in duodenal digesta (P = 0.001 to 0.07) and isolated ruminal microbes differed (P = 0.001 to 0.09) across treatment, the greatest difference noted for total and microbial essential amino acid profile was only 0.3 percentage units. Because total and microbial flow of essential amino acids to the small intestine decreased as OM intake decreased, but true ruminal degradability of individual essential amino acids (P = 0.17 to 0.99) and digesta essential amino acid profile were comparable across treatments, total essential amino acid supply to the small intestine was predicted using OM intake as the independent variable. The resulting simple linear regression equation was: total essential amino acid flow = (0.055 x OM intake) + 1.546 (r2 = 0.91). The model developed in this experiment accounted for more of the variation in the data set than the current beef cattle NRC model, which under-predicted total flow of essential amino acids to the duodenum. The prediction equation developed herein can be used to estimate the supply of essential amino acids reaching the small intestine when formulating supplements to compensate for potential amino acid deficiencies resulting from restricted forage intake.

Adaptation, Physiological↗

PubMed2002

Effects of oscillating dietary protein on nutrient digestibility, nitrogen metabolism, and gastrointestinal organ mass in sheep.

Twenty-four wether lambs (BW = 37.5 +/- 0.8 kg) were used in a 64-d randomized complete block design experiment to evaluate the effect of oscillating dietary CP with undegradable intake protein (UIP) on diet digestibility, N retention, and gastrointestinal (GI) organ mass. 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) and 35% corn-based supplement, and were formulated to contain the same amount of degradable intake protein (9.6% of dry matter), plus additional UIP (from SoyPLUS) to accomplish CP levels above 13%. Beginning on d 52, N balance collections were conducted for 8 d, after which lambs were killed on d 62 and 64 of the trial for measurement of GI organ mass. Because intake was restricted to 3.0% of initial body weight (dry matter basis), dry matter intake did not differ (P > or = 0.67) and no treatment effects (P > or = 0.36) on ADG, feed efficiency, or total tract DM digestibility were observed. Increasing dietary CP from 13 to 17% linearly increased (P = 0.0001) N digestibility, but lambs fed ACP had lower (P = 0.07) total tract N digestibility than those fed 15% CP daily. Although urinary N excretion increased linearly (P = 0.0001) with increasing CP, a linear increase (P = 0.07) was observed in N retention (g/d) with increasing dietary CP. Although the quantity of N retained by lambs fed ACP was not statistically different (g/d, P = 0.19; % of digested N, P = 0.23) from those fed 15% CP daily, N retention in lambs fed ACP was 42% lower than in those fed 15% CP daily (1.8 vs 3.1 g/d, respectively). Increasing CP linearly decreased (P < or = 0.09) weights of the reticulorumen, abomasum, and small intestine, but did not affect (P > or = 0.16) liver or omasum weights. Length of the small intestine was not affected (P > or = 0.45) by treatment, but lambs fed ACP had greater (P = 0.03) small intestine weights than those fed 15% CP daily. Increasing dietary CP linearly decreased (P = 0.03) total GI organ mass, and lambs fed ACP had a greater (P = 0.03) total GI organ mass than those fed 15% CP daily. Oscillating dietary CP may increase the weights of the GI organs, which may subsequently have negative effects on N and energy metabolism in the animal. Likewise, the potential for decreased GI organ mass in response to increased supply of CP with UIP deserves further investigation.

Animal Feed↗

PubMed2002

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.

Animal Feed↗

PubMed2001

Effect of forage:concentrate ratio on ruminal digestion and duodenal flow of fatty acids in ewes.

The objective of this study was to determine the forage:concentrate ratio that would provide the greatest duodenal flow of unsaturated fatty acids in ewes supplemented with soybean oil and to determine how diets differing in forage content affect flow of conjugated linoleic acid (CLA) and trans-vaccenic acid (18:1(trans-11)). Five mature ewes (66.5 +/- 12.8 kg) fitted with ruminal and duodenal cannulas were used in a 5 x 5 Latin square experiment. Diets were isonitrogenous and included bromegrass hay, cracked corn, corn gluten meal, urea, and limestone. Dietary fat was adjusted to 6% with soybean oil. Five ratios of forage:concentrate (18.4:81.6, 32.2:67.8, 45.8:54.2, 59.4:40.6, and 72.9:27.1) were fed at 1.3% of BW daily in equal allotments at 0630 and 1830. After 14 d, Cr2O3 (2.5 g) was dosed at each feeding for 7 d and ruminal, duodenal, and fecal collections were taken for the next 3 d. Duodenal flow of 18:0 increased linearly (P < 0.01) with dietary forage. Duodenal flow of 18:1(cis-9) and 18:2(cis-9,12) decreased (P < 0.001) but duodenal flow of 18:3(cis-9,12,15) increased (P < 0.01) with increased dietary forage. Biohydrogenation of dietary unsaturated fatty acids increased (P < 0.001) as dietary forage increased, which was concomitant with increased ruminal pH. Duodenal flow of 18:2(cis-9,trans-11) increased linearly (P < 0.01) with increased dietary forage but increased abruptly when forage was fed at 45.8%. Duodenal flow of the trans-10, cis-12 and cis-10, cis-12 CLA isomers decreased as dietary forage increased, but flow tended to increase on the highest-forage diet, resulting in both linear (P < 0.01) and quadratic (P < 0.01) effects. Duodenal flow of 18:1(trans-11) decreased from 8.28 g/d on the 18.4% forage diet to 5.47 g/d on the 59.4% forage diet then increased to 7.29 g/d on the highest-forage diet (quadratic, P < 0.1). Duodenal flow of 18:1(trans-11) was 27- to 69-fold greater than flow of CLA. We conclude that when ewes were fed a 6% crude fat diet duodenal flows of dietary fatty acids changed incrementally as dietary forage was increased, whereas changes in flows of CLA isomers seemed to be more abrupt. Biohydrogenation changes were gradual with diet, suggesting a gradual shift in ruminal microbial populations with increasing forage. Finally, the highest-concentrate diet supported the greatest duodenal flows of dietary unsaturated fatty acids, as well as the highest flow of 18:1(trans-11).

Animal Feed↗

PubMed2000

Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: I. In vitro urea kinetics and substrate digestion.

Two in vitro digestion experiments were conducted to evaluate the influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) on in vitro urea kinetics, substrate digestion, and fermentation characteristics. In Exp. 1, in vitro incubations were conducted in 50-mL test tubes containing .25 g of ground fescue hay to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, 10, 30, 60, 120, 240, and 360 min. Samples for VFA analysis were collected at 6 h, and incubations were continued through 48 h to estimate true digestibility (based on NDF analysis). Increasing the dose of NBPT tended (P < .12) to linearly depress the rate of urea hydrolysis and decreased (P < .0004) subsequent NH3 N formation. Although total VFA concentration at 6 h increased linearly (P < .03), acetate:propionate and estimated true digestibility decreased (P < .01) with increasing NBPT concentration. In Exp. 2, we compared in vitro urea kinetics and digestion of forage-only or mixed forage-grain substrates in response to addition of NBPT. In vitro incubations were conducted in 50-mL test tubes containing either .5 g of ground fescue hay or .5 g of a ground fescue hay and ground corn mixture (50:50, DM basis) to which 0, 6.5, 13, 26, or 52 mg of NBPT in a buffered ruminal fluid innoculum was added. Tubes were incubated in triplicate at 39 degrees C and replicated on consecutive days, with NH3 N and urea concentrations measured at 0, .5, 1, 2, 4, 8, 12, 24, and 48 h. At 48 h, samples for VFA analysis were collected and true digestibility (based on NDF analysis) was estimated. No (P > .10) NBPT dose x substrate interactions were detected. Increasing the dose of NBPT depressed (P < .003) the rate of urea hydrolysis and subsequent NH3 N formation, regardless of substrate. Although total VFA concentration was unaffected (P > .10), the acetate:propionate and estimated true digestibility decreased (P < .002) with higher NBPT addition. In both experiments, the rate of urea degradation was not different (P > .20) from zero for the 26 and 52 mg NBPT treatments, indicating that nearly complete inhibition of urease had been achieved. We conclude that NBPT can be used to reduce the rate of NH3 N release from dietary urea and, thereby, offers the potential to improve nonprotein nitrogen utilization in ruminants.

Animal Feed↗

PubMed2000

Influence of the novel urease inhibitor N-(n-butyl) thiophosphoric triamide on ruminant nitrogen metabolism: II. Ruminal nitrogen metabolism, diet digestibility, and nitrogen balance in lambs.

Three lamb metabolism experiments were conducted to investigate the effects of chronic administration of the novel urease inhibitor N (n-butyl) thiophosphoric triamide (NBPT) on ruminal N metabolism, fermentation, and N balance. In Exp. 1, ruminally cannulated wethers (n = 28; 45.0 +/- .9 kg) were administered one of seven doses of NBPT (0 [control], .125, .25, .5, 1, 2, or 4 g of NBPT daily) and fed a common cracked corn/cottonseed hull-based diet twice daily containing 2% urea at 2.5% of initial BW for the duration of the 15-d experiment. Overall, NBPT decreased (linear P < .0001; quadratic P < .001) ruminal urease activity, resulting in linear increases (P < .0001) in ruminal urea and decreases in ruminal NH3 N concentrations. However, the detection of an NBPT x day interaction (d 2 vs 15; P < .01) indicated that this depression in urea degradation diminished as the experiment progressed. Increasing NBPT linearly decreased (P < .01) total VFA concentrations on d 2 of the experiment, but it had no effect (P > .10) on d 15. Increasing NBPT had no effect (P > .10) on DM or ADF digestibilities, but it linearly decreased (P < .01) N digestibility. Supplementing NBPT produced a linear increase (P < .05) in urinary N excretion and a linear decrease (P < .01) in N retention. In Exp. 2, ruminally cannulated wethers (n = 30; 46.8 +/- .6 kg) were fed one of two basal diets (2.0 vs 1.1% dietary urea) at 2.5% of initial BW and dosed with either 0 (control), .25, or 2 g of NBPT daily for the duration of the 15-d experiment. There were no NBPT x dietary urea interactions (P > .10) for Exp. 2. Increasing NBPT depressed (linear and quadratic P < .0001) ruminal urease activity, producing linear (P < .0001) increases in urea N and linear decreases in NH3 N in the rumen. As in Exp. 1, an NBPT x day interaction (P < .05) was noted for urea, NH3 N, and total VFA concentrations; the maximum response to NBPT occurred on d 2 but diminished by d 15 of the experiment. Administration of NBPT did not influence (P > .10) DM, ADF, or N digestibilities in Exp. 2. In Exp. 3, wether lambs (n = 30; 26.4 +/- .7 kg) were subjected to the same treatment regimen as in Exp. 2 for a 14-d N balance experiment. Although several NBPT x dietary urea interactions (P < .05) were noted, increasing NBPT did not affect (P > .10) N digestibility. Administration of NBPT quadratically increased (P < .10) urinary N excretion, producing a linear decrease (P < .05) in N retention. These results suggest that although NBPT is capable of inhibiting ruminal urease short-term, the ruminal microflora may be capable of adapting to chronic NBPT administration, thereby limiting its practical use in improving the utilization of dietary urea.

Ammonia↗

PubMed1999

Fermentation substrate and dilution rate interact to affect microbial growth and efficiency.

The effect of dilution rate (D) on carbohydrate, fibrous and nonfibrous, and protein fermentation by ruminal microorganisms was studied using a single-effluent continuous-culture system. The diets of fibrous carbohydrate, nonfibrous carbohydrate, or protein were formulated with soybean hulls (FC), ground corn (NFC), or isolated soy protein (PR) as the primary ingredient, respectively. Six dilution rates (.025, .050, .075, .10, .15, and .20/h of fermenter volume) were used. Digestibilities of DM, OM, and CP for the three diets and of NDF and ADF for the FC diet decreased (P<.001) as D increased, although the response of the digestibility to D varied with diet. Increasing D resulted in an increase in pH (P<.001) and a decrease (P<.001) in ammonia concentration. Daily volatile fatty acid production increased (quadratic; P<.01) for the FC and NFC diets, but decreased (quadratic; P<.001) for the PR diet. Increasing D quadratically increased (P<.001) the molar percentage of acetate and propionate, but quadratically decreased (P<.001) butyrate and valerate for the FC and NFC diets. For the PR diet, the molar percentage of propionate and valerate increased (quadratic; P<.01), whereas acetate and butyrate decreased (linear; P<.001) in response to increasing D. Molar percentage of isobutyrate and isovalerate decreased (P<.01) with increasing D for all three diets. As D increased, daily microbial N production showed quadratic responses with maximum values achieved at .126, .143, and .187/h D for the FC, NFC, and PR diet, respectively. There was a positive correlation between microbial growth efficiency (MOEFF) and D. A quadratic model fit the data of MOEFF as affected by D, and maximum MOEFF of 37.3, 59.6, and 71.4 g of bacterial N/kg OM truly fermented were calculated to be achieved at .177, .314, and .207/h D for the FC, NFC, and PR diet, respectively. Dilution rate significantly influenced the ruminal microbial fermentation of fibrous and nonfibrous carbohydrates and proteins, and was positively related to microbial yield and growth efficiency. In addition, microbial nitrogen composition, and therefore efficiency, was affected by substrate fermented.

Animal Feed↗

PubMed1998

Amino acid and energy interrelationships in growing beef steers: II. Effects of energy intake and metabolizable lysine supply on growth.

We conducted three experiments to determine the optimal metabolizable Lys:net energy ratio for growth of beef calves. The single basal diet fed contained corn (56.1%), soybean hulls (18%), cottonseed hulls (15%), animal fat (4.25%), and corn gluten meal (5.6%). In Exp. 1, 54 steers were individually fed the basal diet at 1.5, 2.25, and 3.0 times NEm requirement; rations were top-dressed with 3.4 g of rumen-stable (RS) Met and either 0, 2, 4, 6, 8, or 12 g of RS-Lys daily. An additional 18 steers were fed the same three levels of energy and supplemented with 125 g of blood meal per steer. In Exp. 2, 68 crossbred steers were subjected to the same experimental protocol, with the exception that only the two highest levels of energy were used. Of these steers, 48 were fed individually and received the RS-Lys treatments; the remaining 20 steers received 125 g of blood meal per steer. No interaction (P > .10) was detected between level of supplemental Lys and energy intake in Exp. 1 or 2. Supplementation with RS-Lys improved (P < .01) ADG in Exp. 1, but it had no effect (P > .10) on growth in Exp. 2. The Lys requirement estimates were 44.3 and 51.3 g/d, corresponding to maximal growth rates of 1.21 and 1.64 kg/d for the 2.25 and 3.0 times maintenance treatments, respectively. Comparing the growth rates of steers fed supplemental Lys with those of steers fed blood meal in Exp. 1 and 2 revealed an ADG advantage (P < .03) with blood meal supplementation. To confirm the blood meal response, Exp. 3 used 75 crossbred steers fed the basal diet at 3.0 times NEm requirement plus either 3.4 g RS-Met, 3.4 g RS-Met and 12 g RS-Lys, or 125 g of blood meal per steer. Blood meal supplementation improved (P < .01) growth of steers over those fed supplemental Met or Met plus Lys. Although a distinct relationship between amino acid requirements and energy supply may exist, Lys and Met were not first-limiting in these experiments, or selective supplementation with undegradable protein may have provided some factor that enhanced performance beyond that detected with Lys and Met alone.

Animals↗

PubMed1997

Amino acid and energy interrelationships in growing beef steers: I. The effect of level of feed intake on ruminal characteristics and intestinal amino acid flows.

Five cannulated Holstein steers (538 +/- 35 kg) were used in a 4 x 4 Latin square design experiment with extra observations to examine the influence of level of feed intake on postruminal flow and intestinal disappearance of N and amino acids (AA). Treatments consisted of a single diet fed at four levels of energy intake (1.5, 2.0, 2.5, and 3.0 times NEm requirement). The diet was formulated on a DM basis to contain 13.25% CP using cracked corn (56.1%), soybean hulls (18%), cottonseed hulls (15%), soybean oil (4.25%), and corn gluten meal (5.6%). Increasing feed intake linearly increased (P < .0001) the quantity of OM truly digested in the stomach but tended to decrease (P = .11) OM digestion as a percentage of intake. Level of feed intake had no effect (P > .10) on ruminal pH, NH3 N, or peptide concentration or on particulate and fluid passage rates. However, total VFA concentration increased linearly (P < .0001) and the acetate: propionate ratio decreased linearly (P < .0001) as feed intake increased. Flows of microbial and nonmicrobial N at the duodenum linearly increased (P < .002) with increasing intake but did not differ (P > .10) as a percentage of intake. Level of feed intake did not affect (P > .10) microbial efficiency, N disappearance from the small intestine, or total tract N digestibility. With the exception of tryptophan, flows of all individual AA increased linearly (P < .01) with increasing intake. As a percentage of duodenal flow, AA digestion in the small intestine did not differ (P > .10), leading to a linear increase (P < .10) in the net quantity of individual (with the exception of tryptophan) and total AA disappearing from the small intestine as feed intake increased. Likewise, the profile of AA (except tryptophan) disappearing from the small intestine was unaffected (P > .10) by level of feed intake. When compared with predicted requirements for a 227-kg growing beef steer, Arg, Met, His, and Lys were suggested to be the most limiting AA for growth when this diet is fed. We conclude that altering energy intake by restricting intake of a single diet has only minor effects on the profile of digestible AA or other nutrients presented to the animal.

Amino Acids↗

PubMed1996

Influence of source and amount of dietary protein on milk yield by cows in early lactation.

The purpose of this research was to examine the effects of various amounts of CP and RUP on AA flow to the small intestine and milk yield of lactating dairy cows. The first trial was a 5 x 5 Latin square design using five ruminally and duodenally cannulated multiparous cows. Diets contained chopped alfalfa hay, corn silage, high moisture corn, solvent-extracted soybean meal, and specially processed soybean meal (60.2% RUP). Soybean meal replaced high moisture corn to increase dietary CP from 14.5 to 16.5 or 18.5%, and specially processed soybean meal replaced solvent-extracted soybean meal in diets containing 16.5 or 18.5% CP to provide 6.2, 7.3, 6.7, and 8.3% RUP. Increasing dietary CP increased the flows of all AA to the duodenum. Increasing dietary RUP increased flows of Arg, His, Lys, Phe, Asp, and Glu to the duodenum. In a second trial, 36 cows were fed diets similar to those used in trial 1. Increased amounts of RUP in diets tended to increase milk yield because of improved protein status, improved intake of metabolizable energy, or both.

Amino Acids↗

PubMed1995

Supplemental protein sources for steers fed corn-based diets: I. Ruminal characteristics and intestinal amino acid flows.

Five cannulated Holstein steers (302 +/- 23 kg) were used in a 4 x 4 Latin square design experiment with extra observations to evaluate the effect of supplemental protein source on postruminal flow and intestinal disappearance of N and amino acids (AA). Diets were formulated to contain 12.5% CP using cracked corn (70%), ground corn cobs (15%), and supplement (15%). Except for an all-urea supplemented control diet, 40% of the total dietary CP was supplied by soybean meal (SBM), a high ruminal escape soybean meal (SoyPLUS; SP), or a corn gluten meal/blood meal combination (CB; 50:50 on a CP basis). The steers were fed twice daily and DMI was restricted to 2.0% of initial BW. Supplementation with CB increased (P < .10) non-microbial N flow at the duodenum but tended to decrease microbial N flow such that no differences (P > .10) in total N flows at the duodenum were detected among treatments. The efficiency of microbial protein synthesis was not affected by treatment but was greatest for urea/and tended to decrease when SP and CB were fed (21.8, 20.5, 19.5, and 15.7 g of N/kg of OM truly digested for urea, SBM, SP, and CB, respectively). A possible shortage of ruminally degradable N, as evidenced by low ruminal NH3 N concentrations (3.6, 4.2, 3.9, and 2.1 mg/dL for urea, SBM, SP, and CB respectively), or other factors, may have limited microbial protein synthesis. However, microbial N flows averaged 60.0% of duodenal N flow across treatments. Duodenal flow of essential, nonessential, and total AA were similar (P > .10) among treatments and averaged 293, 361, and 653 g/d, respectively). Lysine and methionine flows did not differ (P > .10) and averaged 41.6 and 13.3 g/d, respectively. The source of supplemental protein had no impact (P > .10) on small intestinal disappearance of AA or total tract N disappearance. Feeding proteins resistant to ruminal degradation may have limited microbial protein production, resulting in a shift in the proportion of metabolizable protein arriving at the small intestine from dietary and microbial origins. These results suggest that corn-based diets may be limiting in ruminally degradable N, especially when high ruminal escape protein sources are fed as supplemental CP.

Amino Acids↗

PubMed1995

Supplemental protein sources for steers fed corn-based diets: II. Growth and estimated metabolizable amino acid supply.

Seventy Simmental-cross steers (average initial weight 301 +/- 24 kg) were individually fed in a 175-d completely randomized design experiment to evaluate the effects of source and level of protein in the diet on gain and feed efficiency. Steers were allotted to 1 of 10 treatments (seven steers per treatment) in a 3 x 3 factorial arrangement of treatments plus a urea-supplemented control diet. Main factors were source of supplemental protein (soybean meal [SBM], a high ruminal escape soybean meal [SP; SoyPLUS], or a combination of corn gluten meal and blood meal [CB; 50:50 on a nitrogen basis]) and level of each protein source (20, 30, or 40% of total dietary CP). Based on 18-h in situ ruminal incubation, escape N content of the protein sources was 66.0, 82.5, and 90.8% of total N and metabolizable amino acid (MAA) content was 29.1, 33.4, and 67.8 g/100 g of DM for SBM, SP, and CB respectively. The steers were fed 12.5% CP diets based on cracked corn (70%) on d 0 through 70 and were switched to a common 11.5% CP urea-supplemented cracked corn diet (80%) on d 71. The steers were housed in individual confinement stalls and had ad libitum access to feed. Replacing urea with SBM or SP increased (P < .05) 28- and 70-d ADG and DMI and increased (P < .05) 28-d efficiency (kg of gain/100 kg of feed). Replacing urea with CB did not improve (P > .05) 28- or 70-d ADG or DMI but did increase (P < .05) 28-d efficiency. The growth rate of steers at 28 and 70 d was correlated to a greater degree with ME intake (r2 = .83 and .85, respectively) rather than MAA supply, suggesting that the MAA supply was not first-limiting for growth. The source of supplemental protein fed during d 0 through 70 had no effect (P > .05) on 175-d DMI or efficiency; however, feeding SBM increased (P < .05) 175-d ADG compared with feeding urea, SP, or CB. Increasing supplemental true protein tended to linearly increase ADG and DMI at 28 and 70 d, but overall, ADG, DMI, and efficiency were not affected (P > .05) by treatment. Replacing urea with SBM or CB in the first 70 d decreased (P < .05) carcass quality grade, dressing percentage, and longissimus muscle area.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acids↗

PubMed1995

The value of soybean hulls as a replacement for corn in beef cattle diets formulated with or without added fat.

One hundred twenty crossbred yearling steers (average weight = 445 +/- 32 kg) were used in an 84-d randomized complete block design experiment to determine the value of soybean hulls (SH) as a replacement for corn in concentrate diets formulated with or without added fat (lard). The steers were blocked by weight and alloted to one of eight treatments in a 4 x 2 factorial arrangement of treatments. The main factors were amount of SH (0, 20, 40, or 60% of diet DM) and amount of added fat (0 or 5% of diet DM). The basal diet without added fat or SH contained cracked corn (80%), a urea-based protein supplement (15%), and ground corn cobs (5%). Replacing corn with SH linearly (P = .03) decreased ADG, increased DMI (linear, P = .003; quadratic, P = .06), and linearly (P < .001) decreased gain efficiency. Fat addition tended (P = .08) to improve efficiency; ADG and DMI were unaffected (P > .05) by fat addition. Similar diets were fed to 16 wethers (average weight = 47 +/- 2.3 kg) in a randomized complete block design experiment to determine digestibility of NDF and dietary concentration of DE. Replacing corn with SH linearly increased DMI (P = .001) and NDF (P < .001) and linearly decreased (P < .001) the digestibility of DM. The digestibility of NDF tended to increase with increased SH. The digestibility of energy linearly (P = .0001) decreased with increased SH. The amount of fat had no effect (P > .05) on DMI or intake of NDF or digestibilities of these nutrients. The addition of fat tended (P = .07) to improve the intake of DE.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗