Comparison of the effects of three methods of harvesting and storing alfalfa on nutrient digestibility by lambs and feedlot performance of steers

Two lamb digestion and three steer growth experiments were conducted to study the feeding value of alfalfa harvested as direct-cut silage (DCS) with grain added prior to ensiling or as low-moisture silage (LMS) or hay with grain added at feeding. In all experiments, alfalfa-grain mixtures contained approximately 50% alfalfa and 50% concentrate (dry matter [DM] basis). In Exp. 1, lambs fed DCS alone consumed less DM than lambs fed LMS or hay alone or any of the alfalfa-grain mixtures. Apparent digestibilities of DM and fiber components were higher (P less than .05) for DCS than for LMS or hay. Lambs that were fed LMS digested more (P less than .05) DM and fiber components than lambs fed hay. Addition of grain resulted in increased (P less than .05) DM digestibility and decreased (P less than .05) digestibilities of neutral detergent fiber and acid detergent fiber. In Exp. 2, growing steers (271 kg) fed DCS-grain had increased (P less than .05) weight gains compared with steers fed hay-grain. Steers fed any of the alfalfa-grain mixtures gained weight more rapidly (P less than .05) than steers fed corn silage (CS)-based diets. In a third experiment, finishing steers (283 kg) fed DCS-grain, LMS-grain, hay-grain or CS-based diets performed similarly (P greater than .05), although steers fed DCS-grain had higher (P less than .05) dressing percentages and yield grades than steers that were fed the other three diets and were fatter (P less than .05) than those fed LMS-grain or CS. In Exp. 4, lambs fed DCS-grain or LMS-grain had higher (P less than .05) apparent DM and organic matter digestibilities than lambs fed CS-based diets with similar forage:grain proportions. In Exp. 5, finishing steers (326 kg) fed DCS-grain gained similarly (P greater than .05) to steers fed LMS-grain or an 85% concentrate diet based on high-moisture corn. Steers fed CS diets had lower (P less than .05) gains and increased (P less than .05) feed per gain compared with steers fed DCS-grain, LMS-grain or high-moisture corn.     

Influence of dietary alfalfa:orchardgrass hay and lasalocid on in vitro estimates of dry matter digestibility and volatile fatty acid concentrations of cecal contents and rate of digesta passage in sows

Four mature crossbred sows were fistulated in the cecum, with two sows fed a corn-alfalfa:orchardgrass hay (46%) diet (CH) and two fed a corn-soybean meal diet (CS). Four experiments were conducted to evaluate buffers, incubation times, buffer pH and substrate and inocula sources in an in vitro, anaerobic, mixed-culture system. In vitro dry matter digestibility (IVDMD) and substrate solubility in buffer (SS) were determined. In Exp. 1, substrates were CH and CS diets with cecal inocula obtained from CH- and CS-fed sows. The bicarbonate (B) buffer resulted in lower (P less than .01) and less variable SS for all treatments. In vitro dry matter digestibility was higher (P less than .01) for the CS diet at both 24 and 48 h incubation. Use of the B buffer also resulted in higher (P less than .001) IVDMD values. In Exp. 2, substrates were either as in Exp. 1 or were freeze-dried cecal contents (CC) from CH- or CS-fed sows. In vitro dry matter digestibility of CC was lower (P less than .006) than IVDMD of diet, while IVDMD was higher (P less than .02) with cecal inocula than fecal inocula. In Exp. 3, substrate-inocula treatments were CH-CH, CH-CS, CS-CH and CS-CS. Substrate solubility was lower (P less than .05) at pH 5.8 than at pH 6.8. In vitro dry matter digestibility was higher when substrate and inocula were from the same source and at pH 5.8. In Exp. 4, CC and inocula were from sows fed CH and CS diets with or without lasalocid. In vitro dry matter digestibility was higher with CC from lasalocid-fed sows and inocula from sows fed no lasalocid. The CH diet resulted in higher acetate (Ac) and lower propionate (Pr) molar proportions than did the CS diet, while lasalocid increased molar proportion Pr and decreased molar proportion Ac in cecal contents from sows fed either diet. Corn-alfalfa:orchardgrass hay-fed sows had a faster rate of digesta passage and shorter cecal retention time than did CS-fed sows.     

Lysocellin effects on growth performance, ruminal fermentation, nutrient digestibility and nitrogen metabolism in steers fed forage diets

Studies were conducted to determine the effects of lysocellin on growth performance and metabolism of steers fed forage-based diets. Treatments in all experiments consisted of 1) control, 2) 100 mg lysocellin/d, 3) 200 mg lysocellin/d and 4) 200 mg monensin/d. In each of two 90-d performance studies, 24 Hereford steers were individually fed greenchop (fungus-free tall fescue and Coastal and Tifton-44 bermudagrass) ad libitum and .91 kg/d of a corn-trace mineral salt supplement. In Exp. 1, tall fescue was fed from d 1 to 45 and bermudagrass from d 46 to 90. Bermudagrass was offered during d 1 to 45 and tall fescue during d 46 to 90 in Exp. 2. Lysocellin improved gain (Exp. 1, P less than .01) and feed conversion (Exp. 1 and 2 combined, P less than .05), decreased total VFA concentrations (P less than .05), increased molar proportions of propionate, isobutyrate and isovalerate (P less than .01), decreased molar proportions of acetate and butyrate (P less than .01) and lowered acetate:propionate (P less than .01). Two metabolism studies involving a total of 16 Hereford steers were conducted. Steers were fed tall fescue greenchop and .91 kg/d supplement for a 34-d adjustment period followed by a 5-d total collection period. Lysocellin increased N digestibility (P less than .01) and N retention (P less than .06) but did not (P greater than .05) affect DM, NDF or ADF digestibility. Data indicate that lysocellin results in major alterations in ruminal fermentation and can increase growth performance and N retention in steers fed forage-based diets.     

Rice mill feed as a replacement for broiler litter in diets for growing beef cattle

The efficacy of replacing broiler litter with rice mill feed was evaluated in four experiments. In Exp. 1, 40 predominantly Angus steers (initial BW = 277+/-18.2 kg) were fed four dietary treatments for 112 d (five steers per pen; two pens per diet). Dietary treatments (DM basis) were as follows: 1) 47% broiler litter:53% corn; 2) 60% rice mill feed:40% corn; 3) 50% rice mill feed:50% corn; and 4) 40% rice mill feed:60% corn. All diets, along with bermudagrass hay, were fed free choice. Daily gains were faster (P < 0.10) for the 50:50 and 40:60 diets (1.26 and 1.30 kg/d, respectively) than for the broiler litter diet (0.89 kg/d). Daily DMI was less (P < 0.10) by steers consuming rice mill feed-based diets than by those consuming broiler litter-based diets. In Exp. 2, 16 Angus x Charolais steers (initial BW = 277+/-22.7 kg) were fed the same four diets used in Exp. 1 while housed in individual metabolism stalls for determination of nutrient digestibility. Daily DMI was not different (P > 0.10) among diets. Nutrient digestibilities did not differ among diets (P > 0.10). In Exp. 3, 40 Continental cross steers (initial BW = 257+/-21.3 kg) were fed one of four dietary treatments for 112 d (five steers per pen; two pens per diet). On a DM basis, diets were as follows: 1) 47% broiler litter:53% soyhulls; 2) 70% rice mill feed:30% soyhulls; 3) 60% rice mill feed:40% soyhulls; and 4) 50% rice mill feed:50% soyhulls. All diets, along with bermudagrass hay, were fed free choice. Daily gains were less (P < 0.05) for the broiler litter diet than for the 60:40 and 50:50 diets (1.05, 1.16, and 1.28 kg/d, respectively), and steers fed the broiler litter diet consumed less DM than did steers fed the varying rice mill feed-based diets (P < 0.10). In Exp. 4, 16 Angus x Charolais steers (initial BW = 292+/-21.1 kg) were fed the same four diets as in Exp. 3 while housed in individual metabolism stalls for determination of nutrient digestibility. Daily DMI was less (P < 0.01) for the broiler litter diet (5.0 kg/d) than for the 70:30, 60:40, and 50:50 diets (7.8, 7.9, and 7.9 kg/ d, respectively). Digestibilities for DM, OM, and ADF did not differ (P > 0.10) among treatments; however, CP digestibility was greatest (P < 0.10) for the 60:40 diet, and NDF digestibility was least (P < 0.10) for the 70:30 diet. Rice mill feed can be used to replace broiler litter to formulate low-cost diets for stocker calves. Soyhulls and corn can be blended with rice mill feed to produce acceptable backgrounding diets for growing beef calves.     

Effects of supplement type on animal performance, forage intake, digestion, and ruminal measurements of growing beef cattle

Two experiments were conducted to determine the effects of supplement type on the rate of gain by heifers grazing bermudagrass and on the intake, apparent total-tract OM digestibility, ruminal fermentation, digesta kinetics, in situ DM digestibility, and forage protein degradation by steers fed prairie hay. In Exp. 1, 45 heifers (284+/-24 kg) grazed a bermudagrass pasture for 91 d in the late summer to determine the effects of no supplement (CON), or one of four individually fed monensin-containing (150 mg/[heifer x d]) supplements (MINCS; 0.1 kg of mineral mix with 0.2 kg [DM] of cottonseed hulls as a carrier/[heifer x d]), a pelleted protein supplement (PROT; 1 kg of DM, 242 g of degradable intake protein [DIP]/[heifer x d]), or high-fiber (HF) and high-grain (HG) (2 kg of DM, 243 and 257 g of DIP, respectively/[heifer x d]) pelleted energy supplements. In Exp. 2, four ruminally cannulated steers (311+/-22 kg) with ad libitum access to low-quality (4% DIP, 73% NDF, 40% ADF) prairie hay were individually fed monensin-containing (200 mg/[steer x d]) treatments consisting of 1) mineral mix + corn (MINCR; 0.1 kg of mineral and 0.4 kg of cracked corn [DM] as a carrier, 19 g of DIP/[steer x d]), 2) PROT (1.4 kg of DM, 335 g of DIP/[steer x d]), 3) HF, or 4) HG (2.9 kg of DM, 340 and 360 g of DIP, respectively/[steer x d]) in a 4 x 4 Latin square with 14-d adaptation and 6-d sampling periods. In Exp. 1, the HF-, HG-, and PROT-supplemented heifers had greater (P < 0.01) rates of gain than CON heifers, and the HF- and HG-supplemented heifers tended (P < 0.11) to gain more weight than those fed PROT. In Exp. 2, steers fed PROT consumed more (P < 0.05) hay OM than HF and HG, or MINCR. Total OM intake was greater (P < 0.01) by supplemented steers than MINCR-fed cattle. Hay OM digestibility was not affected (P = 0.19) by treatment, but total diet OM digestibility was greater (P < 0.01) for HF- and HG- than for MINCR- or PROT-fed steers. The rate of in situ DM digestibility was greater (P < 0.01) for HF, HG, and PROT than for MINCR. Results from these studies indicate that feeding milo- vs fiber-based energy supplements formulated to provide adequate DIP did not result in different forage intake, OM digestibility, or in situ DM digestibility, whereas both increased ADG in heifers consuming low-quality forages compared with unsupplemented or mineral- or protein-supplemented cattle. An adequate DIP:TDN balance decreased the negative associative effects often observed when large quantities of high-starch supplements are fed with low-quality hay.     

Effects of rapeseed silage variety and dietary level on digestion and growth performance of beef steers

A digestion and ruminal fermentation trial involving five ruminally cannulated steers assigned to a 5 x 5 Latin square with a 2 x 2 + 1 arrangement of dietary treatments was conducted to evaluate the effects of variety of rapeseed silage (RS) containing either a high (HG) or a low (LG) glucosinolate concentration when fed at 100 or 50% of diet DM. A bromegrass hay-corn-soybean meal mixture, which was expected to be isocaloric and isonitrogenous with the RS, was used as the control (C) treatment and replaced RS in the 50% diets. In situ disappearance of substrate from both RS varieties was measured in ruminal environments created by each diet. No dietary treatment x RS substrate interactions were observed for any in situ variable. Total tract digestibility and extent of in situ disappearance of both DM and NDF were greater (P less than .01) for HG than for LG. In situ DM and NDF disappearance at 8, 16 and 24 h was greater (P less than .01) for RS than for the C diet. Similarly, total tract DM digestibility was greater (P less than .01) for RS (61.0%) vs C (56.0%) diets. Diets with 50% RS had greater (P less than .01) NDF digestibility (50.4%) than 100% RS (43.6%) diets. Variety of RS had no effect on particulate passage rate. In a 77-d growth trial with 60 beef steers, ADG was greater (P less than .01) for HG vs LG (.46 vs .36 kg), 50 vs 100% (.52 vs .31) and C vs RS (.64 vs .41) diets.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of cattle age, forage level, and corn processing on diet digestibility and feedlot performance

Three experiments were conducted to determine the effects of cattle age and dietary forage level on the utilization of corn fed whole or ground to feedlot cattle. In Exp. 1, 16 steers were used to investigate the effects of cattle age and corn processing on diet digestibility. Two cattle age categories were evaluated (weanling [254 +/- 20 kg BW] and yearling [477 +/- 29 kg BW]; eight steers per group), and corn was fed either ground or whole to each cattle age category. Cattle age and corn processing did not affect (P > 0.10) diet digestibility of DM, OM, starch, CP, NDF or ADF, and no interactions (P > 0.10) between these two factors were detected. In Exp. 2, the effects of forage level and corn processing on feedlot performance and carcass characteristics were evaluated. One hundred eighty steers (310 +/- 40 kg BW) were allotted to 24 pens, and were fed one of the following diets: high-forage (18.2% corn silage) cracked corn (HFCC); high-forage shifting corn (whole corn for the first half of the trial, then cracked corn until harvest; HFSC); high-forage whole corn (HFWC); low-forage (5.2% corn silage) cracked corn (LFCC); low-forage shifting corn (LFSC); and low-forage whole corn (LFWC). For the high-forage diets, steers fed cracked corn had 7% greater DMI than those fed whole corn, whereas for the low-forage diets, grain processing did not affect DMI (interaction; P = 0.02). No interactions (P > 0.10) between forage level and corn processing were found for ADG and G:F. Total trial ADG and G:F, and percentage of carcasses grading USDA Choice, and carcass yield grade were not affected (P > 0.10) by corn processing. Cattle with fewer days on feed grew faster and more efficiently when cracked corn was fed, whereas cattle with longer days on feed had greater ADG and G:F when corn was fed whole (interaction; P < 0.10). In Exp. 3, the effects of forage level and corn processing on diet digestibility were evaluated. The high-forage cracked corn, high-forage whole corn, low-forage cracked corn, and low-forage whole corn diets used in Exp. 2 were fed to 16 steers (350 +/- 27 kg BW) in a digestion trial. No interactions (P > 0.10) between forage level and corn processing were detected for starch digestibility. Forage level and corn processing (grinding) did not affect (P > 0.10) diet DM, OM, starch, CP, and NDF digestibility. Processing corn did not provide additional benefits to feedlot cattle performance under these experimental conditions.     

Utilization of alkaline hydrogen peroxide-treated wheat straw in cattle growing and finishing diets.

Two experiments were conducted to evaluate alkaline hydrogen peroxide-treated wheat straw (AHPWS) in cattle growing (Exp. 1) and finishing (Exp. 2) diets. In Exp. 1, 162 crossbred steers (257 kg) were fed 66% roughage diets in an 84-d growth trial to compare AHPWS to corn silage (CS) and to evaluate different supplemental CP sources and levels. A completely randomized design with a 3 x 3 factorial arrangement of treatments was used. Factors were roughage source (CS, a 1:1 mixture of CS:AHPWS [MIX] and AHPWS) and CP treatment (13 and 11% CP with supplemental CP provided by soybean meal [13-SBM] and [11-SBM] and 11% CP with a combination of urea, corn gluten meal, and fish meal [UGF]). Lasalocid was fed at the rate of 200 mg per steer daily. Steers fed AHPWS had decreased (P less than .01) DMI compared with steers fed MIX and CS. This may be due to increased dietary Na from residual Na in AHPWS. With each incremental increase in AHPWS, ADG and gain/feed decreased (P less than .01). Dry matter intakes (kg/d), ADG (kg), and gain/feed for CS, MIX, and AHPWS were 8.0, 1.56, and .19; 8.2, 1.33, and .16; and 7.5, 1.08, and .14, respectively. Decreased performance by steers fed AHPWS may be due, in part, to a negative interaction between the lasalocid and dietary minerals. There were no differences in performance due to CP supplementation. In Exp. 2, AHPWS was compared to alfalfa hay (AH) and CS at 10 and 20% of dietary DM (2 x 3 factorial) in a 127-d finishing trial with 108 crossbred steers (341 kg).(ABSTRACT TRUNCATED AT 250 WORDS)     

Physiological and pathological effects of feeding high levels of magnesium to steers

The effects of feeding high levels of Mg were evaluated in a 130-d study with 24 steers. Six steers were allotted to each of four diets supplemented with MgO to attain .3, 1.4, 2.5 or 4.7% Mg, DM basis. Chromic oxide was used as digesta marker; fecal grab samples were collected once daily during nine consecutive 10-d periods. Steers fed 2.5 and 4.7% Mg refused some feed during the study, so their respective dietary Mg intakes were 2.4 and 3.7% (DM basis). Severe diarrhea and a lethargic appearance were observed in steers fed the two higher Mg levels. Fecal DM and apparent DM digestibility decreased linearly (P less than .01) with increased dietary Mg. Apparent Mg absorption (g/d) increased linearly (P les than .01) and apparent Ca and P absorption (g/d) decreased linearly (P less than .01) with addition of Mg to the diet. Increasing dietary Mg linearly elevated blood serum and erythrocyte Mg (P less than .01; P less than .05, respectively) and serum inorganic P (P less than .05) and linearly decreased serum Ca (P less than .01). Magnesium concentration in liver, kidney, skeletal muscle and rib-bone and P in skeletal muscle all increased linearly (P less than .05) with dietary Mg. Increasing dietary Mg in the steers caused a progressive degeneration of the stratified squamous epithelium of rumen papillae. A progressively more serious Mg toxicosis condition developed over time in steers fed diets containing 2.4 and 4.7% Mg.     

Effect of diet composition and feed intake level on diet digestibility and ruminal metabolism in growing lambs.

Lambs (29 +/- 2.5 kg) were fed three diets at various intakes to determine whether diet composition or level of intake was reflected in changes in diet digestibility or ruminal fluid characteristics. In Exp. 1, a 90% concentrated, pelleted diet or a whole shelled corn diet with a pelleted protein supplement was fed at three levels of intake: ad libitum and 92.5 and 85% of ad libitum (n = 15). Exp. 2 compared the 90% concentrate diet with diets in which the energy density was diluted to 55 or 72.5% concentrate by including alfalfa hay as a possible method of restricting energy intake (n = 6). Lambs were adapted to diets for 13 d; feces were collected for 6 d and ruminal fluid was collected 0, 3, and 6 h after feeding on the day following fecal collection. Restricting intake in Exp. 1 did not affect DM digestibility or digestibility of CP or starch. Digestibility of ADF was increased (P less than .10) by restricting intake. Ruminal fluid pH, ammonia concentration and VFA concentrations were affected little by either restricted intake level. Digestibility of DM was 4% higher (P less than .001) and starch 5% higher (P less than .001) for the whole shelled corn diet than for the pelleted, high-concentrate diet. Ruminal pH of lambs fed the whole shelled corn diet was higher and fluctuated less than the ruminal pH of lambs fed the high-concentrate, pelleted diet. In Exp. 2, diet digestibility was reduced (P less than .01) and ruminal pH was increased (P less than .002) by addition of hay. Restricted feeding of lambs did not seem to increase diet digestibility or alter ruminal conditions.     

Effect of dietary level of barley-based supplements and ruminal buffer on digestion and growth by beef cattle

Six ruminally cannulated beef steers were used in a 6 x 6 Latin square experiment with a 3 x 2 factorial arrangement of treatments to evaluate the effects of barley supplementation (BS; 10, 30 or 50% of diet DM) and ruminal buffer (RB; Na sesquicarbonate at 0 or 4% of BS DM) addition to bromegrass hay-based diets on digestion. When early- (boot) and late- (full maturity) havested bromegrass and wheat straw substrates were incubated in situ, no interactions (P greater than .10) involving substrate with dietary BS or RB were observed, indicating that forages differing in fermentability responded similarly to different ruminal environments. Averaged across substrates, RB had no effect with 10% BS and a positive effect with 30% BS, but a negative effect with 50% BS diets (BS x RB, quadratic; P less than .05) for in situ DM and NDF disappearance for 18 and 24 h of incubation and for rate of disappearance of potentially degraded DM and NDF. Intakes of DM and digested DM were greater (P less than .01) for RB diets; however, RB had no effect (P greater than .10) on total tract DM and NDF digestibility. Intake and digestibility of DM increased linearly (P less than .01), whereas NDF digestibility decreased linearly (P less than .01) as BS percentage was increased in the diet. Sixty beef steers (avg initial wt 302 kg) were fed the same dietary treatments in a growth experiment. A numerical improvement in DM intake (P = .20) and ADG (P = .06) was observed when RB was provided with the 50% BS diet. Results of these experiments indicate that RB may moderate negative effects occurring on ruminal fiber digestion when grains are used to supplement forage-based diets; however, improvements in ruminal digestion were not translated effectively to improved animal productivity.     

Influence of grazing dormant native range or winter wheat pasture on subsequent finishing cattle performance, carcass characteristics, and ruminal metabolism

A winter grazing/feedlot performance experiment repeated over 2 yr (Exp. 1) and a metabolism experiment (Exp. 2) were conducted to evaluate effects of grazing dormant native range or irrigated winter wheat pasture on subsequent intake, feedlot performance, carcass characteristics, total-tract digestion of nutrients, and ruminal digesta kinetics in beef cattle. In Exp. 1, 30 (yr 1) or 67 (yr 2) English crossbred steers that had previously grazed native range (n = 38) or winter wheat (n = 59) for approximately 180 d were allotted randomly within previous treatment to feedlot pens (yr 1 native range = three pens [seven steers/pen], winter wheat = two pens [eight steers/pen]; yr 2 native range = three pens [eight steers/pen], winter wheat = four pens [10 or 11 steers/pen]). As expected, winter wheat steers had greater (P < 0.01) ADG while grazing than did native range steers. In contrast, feedlot ADG and gain efficiency were greater (P < 0.02) for native range steers than for winter wheat steers. Hot carcass weight, longissimus muscle area, and marbling score were greater (P < 0.01) for winter wheat steers than for native range steers. In contrast, 12th-rib fat depth (P < 0.64) and yield grade (P < 0.77) did not differ among treatments. In Exp. 2, eight ruminally cannulated steers that had previously grazed winter wheat (n = 4; initial BW = 407 +/- 12 kg) or native range (n = 4; initial BW = 293 +/- 23 kg) were used to determine intake, digesta kinetics, and total-tract digestion while being adapted to a 90% concentrate diet. The adaptation and diets used in Exp. 2 were consistent with those used in Exp. 1 and consisted of 70, 75, 80, and 85% concentrate diets, each fed for 5 d. As was similar for intact steers, restricted growth of cannulated native range steers during the winter grazing phase resulted in greater (P < 0.001) DMI (% of BW) and ADG (P < 0.04) compared with winter wheat steers. In addition, ruminal fill (P < 0.01) and total-tract OM digestibility (P < 0.02) were greater for native range than for winter wheat steers across the adaptation period. Greater digestibility by native range steers early in the finishing period might account for some of the compensatory gain response. Although greater performance was achieved by native range steers in the feedlot, grazing winter wheat before finishing resulted in fewer days on feed, increased hot carcass weight, and improved carcass merit.     

Influence of decoquinate on ruminal fermentation, diet digestibility and cattle performance

Three experiments utilizing three Holstein steers (235 and 299 kg avg body weight for Exp. 1 and 2, respectively) were conducted to evaluate the effects of decoquinate, a synthetic coccidiostat, on ruminal fermentation, diet digestibility and performance of steers fed a finishing diet containing monensin and tylosin. Experiment 1 utilized a 70% forage diet, whereas Exp. 2 utilized a 20% forage diet. Each experiment was a 3 X 3 Latin-square design with treatments being 0, .5 and 5 mg decoquinate/kg body weight. Ruminal fermentation characteristics, water kinetics and blood constituents were measured on d 11 of each period, and zero-time volatile fatty acid (VFA) production was measured at 3 and 6 h post-feeding on d 12 to 14. No changes were seen in plasma glucose or L-lactate, ruminal pH, NH3-N or ruminal L-lactate for either experiment. Dry matter digestibility was depressed (P less than .05) at the .5- and 5-mg levels of decoquinate in Exp. 1, but dry matter digestibility was not affected in Exp. 2. No changes were seen in ruminal volume, outflow or total VFA concentration for either experiment. Molar proportions of VFA were not affected in Exp. 1, but the proportions of isobutyrate and butyrate decreased (P less than .05) at the 5-mg level of decoquinate in Exp. 2. Volatile fatty acid production was not changed in Exp. 1, but butyrate production was decreased (P less than .05) at the 5-mg level in Exp. 2. Experiment 3 involved 135 crossbred steers (259 kg avg initial wt), which were stratified by weight into 12 pens.(ABSTRACT TRUNCATED AT 250 WORDS)     

Supplementation of dormant tallgrass-prairie forage: I. Influence of varying supplemental protein and(or) energy levels on forage utilization characteristics of beef steers in confinement

Three experiments were conducted to evaluate effects of supplemental protein vs energy level on dormant forage intake and utilization. In Exp. 1, 16 ruminally cannulated steers were blocked by weight (avg wt = 242 kg) and assigned randomly to a negative control or to one of three isocaloric supplement treatments fed at .4% BW: 1) control, no supplement (NS); 2) 12% CP, low protein (LP); 3) 28% CP, moderate protein (MP); 4) 41% CP, high protein (HP). In Exp. 2 and 3, 16 ruminally cannulated steers were blocked by weight (avg wt = 332 kg, Exp. 2; 401 kg, Exp. 3) and assigned randomly to a 2 x 2 factorial arrangement of treatments. The treatments contrasted low (LP) and high (HP) levels of supplemental protein (.66 g CP/kg BW vs 1.32 g CP/kg BW) with low (LE) and high (HE) levels of supplemental ME (9.2 kcal/kg BW vs 18.4 kcal/kg BW). In Exp. 1, forage DMI as well as ruminal DM and indigestible ADF fill at 4 h postfeeding were greater (P less than .10) with the MP and HP steers than with control and LP steers. Total DM digestibility increased (P less than .10) for supplemented steers (35.5% for control vs 47.3 for supplemented steers); however, LP depressed (P less than .10) NDF digestibility. In Exp. 2, forage DMI, indigestible ADF flow and liquid flow were depressed (P less than .10) in LP-HE supplemented steers. In Exp. 3, HP steers had greater (P less than .10) forage DMI, indigestible ADF fill values (4 h postfeeding), liquid volume and tended (P = .11) to have greater ruminal DM fill (4 h postfeeding). In summary, increased levels of supplemental protein increased intake and utilization of dormant tallgrass-prairie forage (less than 3% CP). Increasing supplemental energy without adequate protein availability was associated with depressed intake and digestibility.     

Effects of restricted and ad libitum intake of diets containing wheat middlings on site and extent of digestion in steers

A 5 x 5 Latin square design was used to determine the effects of restricted and ad libitum intake of diets containing wheat middlings on the site and extent of digestion compared to ad libitum intake of a corn-based diet and ad libitum intake of chopped alfalfa hay. Five ruminally and duodenally cannulated Angus steers (519 +/- 41.5 kg BW) were used to compare five dietary treatments. The five treatments were as follows: ad libitum access to a corn-based finishing diet (control), the control diet with 25 percentage units of the corn and soybean meal replaced with wheat middlings offered ad libitum (WM), the WM diet restricted to 75% of predicted ad libitum intake (RWM), the RWM diet with wheat middlings replaced with ammoniated wheat middlings (RNWM), and ad libitum access to a chopped alfalfa hay diet. Although RWM steers were fed to consume 75% of ad libitum intake, RWM steers consumed 15.5% less DM than WM. Steers fed ad libitum hay consumed 28.6, 31.7, and 37.2% less (P < 0.01) DM, OM, and nitrogen than RWM steers. No differences in apparent or true ruminal digestibility were observed among steers fed the control vs WM, WM vs RWM, RWM vs RNWM, or RWM vs hay diets. However, the steers fed the hay diet had 32.5, 33.4, and 36.9% lower (P < 0.01) apparent total tract digestibilities of DM, OM, and N than those fed the RWM diet. Average ruminal pH was lower (P < 0.01) for control steers than those fed the WM diet and for those fed RWM compared to the hay diet. The acetate:propionate ratio was higher for cattle fed hay vs the RWM diet. Microbial DM and OM flow to the small intestine was higher (P < 0.02) for steers fed the RWM diet than those fed the hay diet. In addition, bacterial N flow to the small intestine was higher (P < 0.01) for cattle receiving the RWM diet than the hay diet. Feeding diets containing 25 percentage units of wheat middlings at 75% ad libitum intake had no effect on ruminal digestibility.     

The effects of lysocellin and varying calcium levels on performance and ruminal and plasma characteristics of growing beef steers fed corn silage

Twenty-four steers initially averaging 221 kg BW were used to evaluate the effects of lysocellin and calcium (Ca) level on performance and ruminal and plasma characteristics. Lysocellin at 0 or 22 mg/kg of diet and Ca at .3 or .6% were fed in a 2 X 2 factorial arrangement of treatments. Steers in individual pens had ad libitum access to a diet consisting of 80% corn silage and 20% (DM basis) of a protein, mineral and vitamin supplement. Ruminal fluid and blood samples were collected on d 42 and 85 of the 113-d trial. Steers fed the .6% Ca diet gained faster and required less feed/unit of gain than those fed the .3% Ca diet (P less than .05). There was a tendency for a lysocellin X Ca interaction for gain and feed efficiency (P less than .10). Lysocellin tended to depress performance when fed with .3% Ca, but it tended to improve gain and feed efficiency when fed with .6% Ca. Molar proportions of propionate were higher and those of acetate were lower (P less than .01) for steers fed lysocellin. Ruminal-soluble Zn, Fe and Cu levels were higher (P less than .01) in steers fed lysocellin. Ruminal-soluble Ca (P less than .01) was higher and ruminal-soluble P and Na were lower (P less than .01) in steers fed .6% Ca. Plasma K was higher (P less than .05) in steers fed .6% Ca but it was lower (P less than .05) in steers fed lysocellin. Results of this study indicate that dietary Ca affects certain metabolic responses to lysocellin in growing cattle.     

Effects of the inclusion of yeast culture (Saccharomyces cerevisiae plus growth medium) in the diet of dairy cows on milk yield and forage degradation and fermentation patterns in the rumen of steers

The effects of including yeast culture (YC; Saccharomyces cerevisae plus growth medium; 5 x 10(9) organisms/g) in diets for ruminants was examined in two experiments. In Exp. 1, 32 multiparous Friesian dairy cows were fed between wk 7 to 12 of lactation one of four completely mixed diets based on either hay or straw plus rolled barley (mixed to give concentrate:forage ratios of either 50:50 or 60:40, respectively) with or without 10 g YC/d in a 2(3) factorial design. Supplementation with YC increased DM intake of the cows by a mean of 1.2 kg/d (P less than or equal to .062) and increased milk yield by 1.4 liters/d (corrected to 4% butterfat; P less than or equal to .05). There was an interaction (P less than .05) between diet composition and YC addition; effects of YC were greatest in diets containing 60:40 (concentrate:forage) ratio. In Exp. 2, three steers were fed a diet of 50% hay and 50% rolled barley (DM basis). Hay was available for the major part of the day but barley was fed in two meals/d. Addition of YC to the diet increased (P less than .05) ruminal pH for 4 h after the barley meal. This elevation in pH probably was due to a reduction (P less than or equal to .01) in the concentration of L-lactate in the ruminal liquor of steers given YC (1.43 vs 3.55 mM; P less than or equal to .01). Peak ruminal L-lactate concentration (7.75 mM) in the controls coincided with time of minimum pH values (2 h after the meal of barley); this peak was absent in steers given YC. YC had no effect on the concentration of VFA in ruminal liquor, but the ratio of acetate to propionate was reduced (P less than or equal to .01) from 3.3:1 to 2.8:1 in steers given YC. The extent of DM degradation of hay incubated in the rumen of steers fed the hay and rolled barley diet was increased (P less than .05) in the presence of YC at 12 h of incubation, but degradation was similar in all treatment groups after 24 h of incubation. Presence of yeast culture in the rumen had effects on ruminal stoichiometry. An increased rate of forage degradation may have increased forage intake and productivity of these dairy cows.     

Influence of forage level on passage rate, digestibility and performance of cattle

Two trials (feedlot and metabolism) were conducted to evaluate the influence of level of chopped tall fescue hay (FH) in high concentrate diets on average daily gain (ADG), liquid and particulate passage rates, digestibility and in situ digestibility of corn. In the feedlot trial, 36 Hereford steers were fed diets containing 15, 30 and 50% FH in combination with 74, 59 and 39% whole shelled corn (WSC) and a soybean meal supplement. Steers offered 15, 30 and 50% FH consumed 9.0, 9.0 and 7.6 kg dry matter (DM) per d; gained 1.19, .89 and .67 kg; and had DM to gain ratios of 7.6, 10.1 and 11.5, respectively. A negative correlation was observed between fecal pH and ADG (r = -.52) and between fecal pH and fecal starch (r = -.40). In a 4 X 4 Latin-square trial, four cannulated steers were fed 4, 8, 16 or 24% FH in combination with 86, 82, 74 or 66% WSC and a soybean meal supplement. After 14 d of adaptation, steers were offered ytterbium (Yb)-labelled WSC and were ruminally pulse-dosed with chromium ethylenediaminetetraacetic acid (Cr-EDTA) on the first day of the collection period. Steers fed 4, 8, 16 or 24% FH had the following particulate passage rates: 2.3, 2.7, 2.7 and 2.9%/h from fecal analyses; 2.3, 1.7, 2.4 and 2.8%/h from ruminal analyses; 6.0, 5.3, 6.3 and 8.1%/h for liquid, respectively. With increasing FH level, liquid passage rate exhibited linear and quadratic effects (P less than .05), while particulate passage rate (rumen sampling) showed linear and cubic effects (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Performance and digestibility characteristics of finishing diets containing distillers grains, composites of corn processing coproducts, or supplemental corn oil

Three experiments evaluated the lipids in distillers grains plus solubles compared with corn or other sources of lipid in finishing diets. Experiment 1 utilized 60 individually fed yearling heifers (349 +/- 34 kg of BW) fed treatments consisting of 0, 20, or 40% (DM basis) wet distillers grains plus solubles (WDGS), or 0, 2.5, or 5.0% (DM basis) corn oil in a finishing diet based on high-moisture corn (HMC) and dry-rolled corn. Cattle fed 20 and 40% WDGS had greater (P < 0.10) G:F than cattle fed 0% WDGS. Cattle fed the 5.0% corn oil had less overall performance than cattle fed the other diets. Results from Exp. 1 indicated that adding fat from WDGS improves performance, whereas supplementing 5.0% corn oil depressed G:F, suggesting that the fat within WDGS is different than corn oil. Experiment 2 used 234 yearling steers (352 +/- 16 kg of BW) fed 1 of 5 treatments consisting of 20 or 40% (DM basis) dry distillers grains plus solubles, 1.3 or 2.6% (DM basis) tallow, or HMC. All diets contained 20% (DM basis) wet corn gluten feed as a method of controlling acidosis. No differences between treatments for any performance variables were observed in Exp. 2. The dry distillers grains plus solubles may be similar to tallow and HMC in finishing diets containing 20% wet corn gluten feed. Experiment 3 used 5 Holstein steers equipped with ruminal and duodenal cannulas in a 5 x 5 Latin square design. Treatments were a 40% WDGS diet, 2 composites, one consisting of corn bran and corn gluten meal; and one consisting of corn bran, corn gluten meal, and corn oil; and 2 dry-rolled corn-based diets supplemented with corn oil or not. Cattle fed the WDGS diet had numerically less rumen pH compared with cattle fed other treatments. Cattle fed WDGS had greater (P < 0.10) molar proportions of propionate, decreased (P < 0.10) acetate:propionate ratios, greater (P < 0.10) total tract fat digestion, and a greater (P < 0.10) proportion of unsaturated fatty acids reaching the duodenum than cattle fed other treatments. Therefore, the greater energy value of WDGS compared with corn may be due to more propionate production, greater fat digestibility, and more unsaturated fatty acids reaching the duodenum.     

Effect of intake level and alfalfa substitution for grass hay on ruminal kinetics of fiber digestion and particle passage in beef cattle

Two experiments were conducted to evaluate digestion kinetics of alfalfa (Medicago sativa L.) substitution for grass hay in beef cattle. In Exp. 1, forage combinations evaluated in situ consisted of 0% alfalfa-100% big bluestem (Andropogon gerardi Vitman), 25% alfalfa-75% big bluestem, 50% alfalfa-50% big bluestem, and 100% alfalfa-0% big bluestem. Nonlinear regression was used to determine the immediately soluble fraction A, the potentially degradable fraction B, the undegraded fraction C, and the disappearance rate of DM and NDF. Dry matter fraction A increased linearly (P = 0.03), and DM and NDF fraction B decreased linearly (P = 0.01) with increasing alfalfa substitution. Rate of DM and NDF disappearance increased linearly (P /= 0.23) on total tract apparent digestibility of all nutrients except CP. Steers fed orchardgrass plus alfalfa had 33% greater (P = 0.01) total tract apparent digestibility for CP than those fed orchardgrass alone. Lag time of DM and NDF disappearance was not affected (P >/= 0.20) by alfalfa supplementation or intake level. Rate of DM and NDF disappearance of orchardgrass was faster (P 相似文献