Time of daily supplementation for steers grazing dormant intermediate wheatgrass pasture.

To compare the effects of time of daily protein supplementation on grazing behavior, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites, 12 ruminally cannulated Holstein steers (449 and 378 kg average initial and final BW, respectively) were allotted to three groups. Treatments consisted of CON = no supplement, AM = cottonseed meal (.25% of BW) at 0600, and PM = cottonseed meal (.25% of BW) at 1200. Steers grazed a dormant (1.1% N) intermediate wheatgrass (Thinopyrum intermedium Host) pasture. Sampling trials occurred in December, January, and February. Supplementation altered (P = .01) time spent grazing; CON steers grazed approximately 1.5 h longer than supplemented steers. Supplemented steers lost less (P = .02) BW (-40 kg) than CON steers (-75 kg) did. Supplementation did not alter (P greater than .15) forage OM intake; however, total OM intake was greater (P = .01) for supplemented steers (22.3 g/kg of BW) than for CON (18.4 g/kg of BW) steers. Supplementation did not affect (P greater than .15) digesta kinetics. Extent of in situ NDF (96 h) and rate (%/h) of disappearance for supplemented steers was greater (P = .01) than for CON steers. Across all periods, ruminal NH3 N and total VFA concentrations were lower (P = .01) for CON steers than for supplemented steers. Serum insulin (ng/mL) concentration was lower (P = .03) and concentration of serum growth hormone (ng/mL) was higher (P = .02) for CON steers than for supplemented steers. Cottonseed meal supplementation enhanced utilization of intermediate wheatgrass; however, supplementation time had minimal effects on the variables measured.     

Effects of base ingredient in cooked molasses blocks on intake and digestion of prairie hay by beef steers

Twelve steers (332 kg) were used in three simultaneous 4 x 3 incomplete Latin squares to evaluate effects of beet molasses (BEET), cane molasses (CANE), or concentrated separator by-product (CSB) as base ingredients in cooked molasses blocks on intake and digestion of prairie hay and ruminal characteristics. All steers had ad libitum access to prairie hay (5.9% CP and 69.4% NDF; DM basis). The four experimental treatments included a control (no supplement) and three cooked molasses blocks, based on BEET, CANE, or CSB, fed daily at .125% of BW (.42 kg/d as-fed, .13 kg/d CP). Forage OM, NDF, and N intakes; digestible OM, NDF, and N intakes; and total tract OM and N digestibilities (percentage of intake) were greater (P < .05) for steers fed cooked molasses blocks than for control steers. Total tract OM digestibility was greater (P < or = .06) for steers fed BEET blocks (54.0%) than for those fed CSB (52.1%) or CANE blocks (52.2%). Digestion of NDF was greatest (P < .05) for steers fed BEET blocks (51.9%) and tended to be greater (P < .07) for steers fed CANE (49.3%) or CSB blocks (49.3%) than for control steers (46.9%). Ruminal ammonia concentrations were greater (P < .05) for steers fed cooked molasses blocks (.89 mM) than for control steers (.21 mM); this was primarily due to increases to 4.6 mM at 2 h postfeeding for steers fed blocks. Concentrations of total VFA in ruminal fluid were greater (P < .05) for steers fed BEET (92.7 mM) and CSB (88.1 mM) blocks than for control steers (80.3 mM), whereas concentrations for steers fed CANE blocks were intermediate (85.4 mM). Steers supplemented with cooked molasses blocks had greater molar percentages of butyrate than did control steers, particularly shortly after feeding. In summary, supplementation with cooked molasses blocks increased forage intake and digestion. The three base ingredients elicited similar responses, although steers fed BEET had slightly greater OM and NDF digestibilities than those fed CANE or CSB.     

Effects of increasing level of supplemental barley on forage intake, digestibility, and ruminal fermentation in steers fed medium-quality grass hay

Objectives of this research were to evaluate effects of increasing level of barley supplementation on forage intake, digestibility, and ruminal fermentation in beef steers fed medium-quality forage. Four crossbred ruminally cannulated steers (average initial BW = 200 +/- 10 kg) were used in a 4 x 4 Latin square design. Chopped (5 cm) grass hay (10% CP) was offered ad libitum with one of four supplements. Supplements included 0, 0.8, 1.6, or 2.4 kg of barley (DM basis) and were fed in two equal portions at 0700 and 1600. Supplements were fed at levels to provide for equal intake of supplemental protein with the addition of soybean meal. Forage intake (kg and g/kg BW) decreased linearly (P < 0.01), and total intake increased linearly (P < 0.03) with increasing level of barley supplementation. Digestible OM intake (g/kg BW) increased linearly (P < 0.01) with increasing level of barley supplementation; however, the majority of this response was observed with 0.8 kg of barley supplementation. Treatments had only minor effects on ruminal pH, with decreases occurring at 15 h after feeding in steers receiving 2.4 kg of barley supplementation. Total-tract digestibility of DM, OM, NDF, and CP were increased (P < 0.04) with barley supplementation; however, ADF digestibility was decreased by 1.6 and 2.4 kg of barley supplementation compared with controls. Ruminal ammonia concentrations decreased linearly (P < 0.01) at 1 through 15 h after feeding. Total ruminal VFA concentrations were not altered by dietary treatments. Ruminal proportions of acetate and butyrate decreased (P < 0.10) in response to supplementation. Rate, lag, and extent (72 h) of in situ forage degradability were unaffected by treatment. Generally, these data are interpreted to indicate that increasing levels of barley supplementation decrease forage intake, increase DM, OM, and NDF digestibility, and indicate alteration of the ruminal environment and fermentation patterns.     

Effects of supplementing prairie hay with corn and soybean meal on intake, digestion, and ruminal measurements by beef steers

Prairie hay supplemented with various amounts of corn and soybean meal was fed to steers in two experiments. Effects of supplementation on hay OM intake, digestion, and ruminal fermentation and kinetics were measured. A preliminary study was conducted to attain accurate values for OM intake and digestibility of prairie hay to be used in ration formulation using the NRC (1996) level 1 model. Ten steers (284 +/- 9 kg) given ad libitum access to chopped prairie hay (75% NDF, 6% CP) were supplemented with dry-rolled corn (0.75% of BW/d) plus soybean meal (0.25% of BW/d). Hay OM intake was 1.85% of BW and hay OM digestibility was 48%. Based on results from the preliminary study, eight ruminally cannulated beef steers (317 +/- 25 kg) received a sequence of eight different supplementation combinations (2 x 4 factorial arrangement of treatments). These supplements consisted of dry-rolled corn at either 0 or 0.75% of BW (DM basis) daily combined with one of four amounts of added soybean meal to provide between 0 and 1.3 g of degradable intake protein (DIP)/kg of BW. After supplements had been fed for 10 d, feces were collected for 4 d. Intake of hay and total OM increased quadratically (P < 0.01) in response to added DIP with or without supplemental corn. Hay OM digestibility increased quadratically (P = 0.03) as DIP was added when corn was fed in the supplement. Intake of digestible OM was greater (P < 0.01) with than without corn supplementation. Increasing DIP increased (P < 0.01) digestible OM intake regardless of whether corn was fed. Inadequate ruminally degraded protein in grain-based supplements decreased forage intake, digestibility, and energy intake of cattle fed low-quality prairie hay. Providing adequate supplemental DIP to meet total diet DIP needs seemed to overcome negative associative effects typically found from supplementing low-quality forages with large quantities of low-protein, high-starch feeds.     

Effects of protein concentration and source on nutrient digestibility by mature steers limit-fed high-concentrate diets.

Five ruminally fistulated 3-yr-old mature Holstein steers (average BW 691+/-23 kg) were used in a 5 x 5 Latin square experiment with a 2 x 2 + 1 fact orial arrangement of treatments. Effects of protein concentration and protein source on nutrient digestibility, excretion of DM and fecal N, ruminal fluid volume and dilution rate, ruminal characteristics, and in situ DM disappearance of whole shelled corn, ground corn, and orchardgrass hay were measured in steers limit-fed high-concentrate diets at 1.5% of BW. A negative control basal diet (NC; 9% CP) was supplemented to achieve either 11 or 14% CP; supplemental CP was either from soybean meal (11 and 14% SBM) or a 50:50 ratio of CP from urea and soybean meal (11 and 14% U). Dry matter and OM digestibilities were 5% greater (P < .07) for steers fed the SBM diets than for those fed the U diets. Starch digestibility did not differ (P > .10) among steers fed any of the diets. Nitrogen source did not affect (P > .10) apparent N digestibility or fecal N excretion; however, steers fed the NC diet had the lowest (P < .10) apparent N digestibility compared with those fed all other diets. Ruminal fluid volume was lower (P < .06) when steers were fed the NC diet compared with all other diets; there were no differences (P > .74) among diets for ruminal fluid dilution rate. In general, ruminal ammonia N and VFA molar proportions were not affected by protein source or concentration. Although CP concentration affected (P < .06) in situ DM disappearance of ground corn, CP concentration did not (P > .48) affect total tract digestion of DM or OM. This indicates that CP concentration may have affected site of digestion, but not extent of digestion. When mature ruminants were limit-fed a corn-based diet to meet primarily a maintenance function, protein source and concentration had little effect on measures of nutrient digestion.     

High-moisture corn utilization in finishing cattle

Two finishing trials, one laboratory trial and one metabolism trial were conducted with the following objectives: 1) to determine the associative effects of feeding high-moisture corn (HMC) with either dry-rolled grain sorghum (DRGS) or dry-rolled corn (DRC) and 2) to evaluate HMC when harvested at different moisture levels, stored in different structures, or fed as whole or rolled HMC. In Trial 1, yearling steers (BW, 328 kg) were fed diets containing mixtures of HMC and DRGS. As level (0, 33, 100%, as percentage of grain DM) of DRGS increased, ADG (P less than .03) and gain/feed (P less than .001) decreased linearly; gain/feed tended to be affected quadratically (P = .14). In Trial 2, yearling steers (BW, 382 kg) fed HMC, stored whole in an upright, oxygen-limiting silo and rolled coarsely before feeding, gained faster (1.46 vs 1.36 kg/d) and more efficiently (.142 vs. .131 gain/feed) than steers fed whole HMC (P less than .01). In Trial 3, as length of storage of bunker HMC increased, in vitro rate of starch digestion and soluble N content increased (20.4 and 36.8%, respectively) and grain pH decreased (10.9%). In Trial 4, steers fed HMC or a mixture of 75% HMC with 25% DRGS had similar ruminal pH throughout a grain adaptation period, but total ruminal VFA were greater (P less than .005) for steers fed HMC alone. These data are interpreted to suggest that feeding a mixture of HMC, ground and stored in a bunker or silo bag, with DRGS will result in a 3.2% associative effect. However, no associative effects were measured when a mixture of HMC, stored whole and fed whole or rolled, and DRC were fed.     

Effect of field peas, chickpeas, and lentils on rumen fermentation, digestion, microbial protein synthesis, and feedlot performance in receiving diets for beef cattle

Two experiments were conducted to evaluate the use of pulse grains in receiving diets for cattle. In Exp. 1, 8 Holstein (615 +/- 97 kg of initial BW) and 8 Angus-crossbred steers (403 +/- 73 kg of initial BW) fitted with ruminal and duodenal cannulas were blocked by breed and used in a randomized complete block design to assess the effects of pulse grain inclusion in receiving diets on intake, ruminal fermentation, and site of digestion. Experiment 2 was a 39-d feedlot receiving trial in which 176 mixed-breed steers (254 +/- 19 kg of initial BW) were used in a randomized complete block design to determine the effects of pulse grains on DMI, ADG, and G:F in newly received feedlot cattle. In both studies, pulse grains (field peas, lentils, or chickpea) replaced corn and canola meal as the grain component in diets fed as a total mixed ration. Treatments included 1) corn and canola meal (control); 2) field pea; 3) lentil; and 4) chickpea. Preplanned orthogonal contrasts were conducted between control vs. chickpea, control vs. field pea, and control vs. lentil. In Exp. 1, there were no differences among treatments for DMI (11.63 kg/d, 2.32% of BW daily, P = 0.63) or OM intake (P = 0.63). No treatment effects for apparent ruminal (P = 0.10) and total tract OM digestibilities (P = 0.40) were detected when pulse grains replaced corn and canola meal. Crude protein intake (P = 0.78), microbial CP flow (P = 0.46), total tract CP digestibility (P = 0.45), and microbial efficiency (P = 0.18) were also not influenced by treatment. Total-tract ADF (P = 0.004) and NDF (P = 0.04) digestibilities were greater with field pea vs. control. Total VFA concentrations were lower for field pea (P = 0.009) and lentil (P < 0.001) compared with control. Chickpea, field pea, and lentil had lower (P < or = 0.03) acetate molar proportion than control. Ruminal pH (P = 0.18) and NH3 (P = 0.14) were not different among treatments. In Exp. 2, calves fed chickpea, field pea, and lentil had greater overall DMI (7.59 vs. 6.98 kg/d; P < or = 0.07) and final BW (332 vs. 323 kg; P < or = 0.04), whereas chickpea and lentil had greater ADG (1.90 vs. 1.71 kg/d; P < or = 0.04) than control. Gain efficiency (P = 0.18) did not differ among treatments. Steers fed pulse grains had similar CP and OM digestibilities compared with a combination of corn and canola meal in receiving diets. Pulse grains are a viable alternative for replacement of protein supplements in receiving diets for beef cattle.     

Supplemental corn grain for steers grazing native rangeland during summer

Effects of supplemental corn grain on forage OM intake (FOMI), digesta kinetics, ruminal fermentation patterns, in vitro OM digestibility (IVOMD), and in situ OM digestion were examined in steers grazing summer blue grama rangeland in northeastern New Mexico during July and August 1988. Sixteen ruminally cannulated steers (average BW 507 kg) were allotted to four treatments and individually fed whole-shelled corn at 0, .2, .4, and .6% of BW in a complete random design with repeated measurements over time. Forage OMI decreased linearly (P = .02) with increasing levels of supplemental corn; however, a tendency toward greater FOMI, as well as faster particulate and fluid passage, was observed when corn was fed at .2% of BW compared with 0, .4, or .6% of BW. Molar proportions of butyrate increased (P less than .10) but molar proportions of acetate and propionate, ruminal pH, and total VFA concentration did not change (P greater than .10) with added corn. Added corn linearly decreased (P less than .10) ruminal ammonia N concentrations in July, but patterns were inconsistent in August. A cubic response (P less than .05) for in situ OM disappearance with added corn was noted after 24, 72, and 96 h of incubation. Supplemental whole corn fed at .2% of BW had no detrimental effects and tended to increase FOMI. However, supplemental corn fed at .4 or .6% of BW decreased FOMI compared with 0 or .2% of BW.     

Intake and digestion of wheat forage by stocker calves and lambs

Because wheat forage contains high concentrations of N, NPN, digestible DM, and water, beef cattle and sheep require an adaptation period before positive BW are seen. The objective of the present experiment was to determine the impact of length of exposure of lambs and steers to wheat forage on BW gains, N retention, and forage digestibility. Sixteen steer calves (average BW = 210 +/- 12 kg) and 20 wether lambs (average BW = 31.5 +/- 2.0 kg) were randomly assigned to 1 of 2 treatment groups. Group 1 grazed a wheat pasture for 120 d during the winter, whereas group 2 was wintered on dormant warm-season grass pastures plus warm-season grass hay and plant-based protein supplements. In the spring (April 5), all lambs and steers grazed wheat pasture for 14 d and were then housed in metabolism stalls and fed freshly harvested wheat forage to determine forage digestibility and N metabolism. Data were analyzed for lambs and steers separately as a completely randomized design, using the individual animal as the experimental unit. Lambs and steers grazing wheat pasture for the first time in the spring had less ADG during the first 14 d than lambs (80 vs. 270 g, respectively; P = 0.01) and steers (1.06 vs. 1.83 kg, respectively; P = 0.09) that had grazed wheat pastures all winter. Digestibility of DM, NDF, and ADF fractions and N metabolism of freshly harvested wheat forage by lambs and steers were not different (P > 0.10) between the 2 treatment groups. Less ADG during the first 14 d of wheat pasture grazing is most likely the result of less DMI by nonadapted animals and is not due to diet digestibility or N metabolism.     

The effects of grazing, liquid supplements, and implants on feedlot performance and carcass traits of Holstein steers

In each of 2 yr, 20 Holstein steers (185+/-7 kg initial BW) were allocated to each of three treatments: pastured for 4.5 mo on grass/legume pastures and then fed 80% corn diets (DM basis) until slaughter; pastured for 4.5 mo on grass/legume pastures with ad libitum access to molasses-based protein supplements and fed 80% corn diets until slaughter; and placed in a feedlot and fed only 80% corn diets until slaughter (FEEDLOT). Half of the steers in each treatment were initially implanted with Revalor-S and not reimplanted. Supplemented steers on pasture had greater (P < 0.05) ADG than unsupplemented steers, and FEEDLOT steers gained faster and were fatter (P < 0.05) after 4.5 mo. Implanted steers had greater (P < 0.05) ADG with no significant treatment x implant status effect. Supplement intake was variable and related to ambient temperature. During the feedlot phase, steers previously on pasture had greater DMI and ADG (P < 0.05) but were not more efficient than FEEDLOT steers. Percentage of USDA Choice carcasses, fat thickness, dressing percentage, yield grade, and final weight were greater (P < 0.05) for FEEDLOT steers than for steers on other treatments. Implanting increased ADG of all steers but did not affect carcass traits, carcass composition, or feedlot performance during the finishing phase. Holstein steers consuming supplemented and unsupplemented pasture before slaughter will be leaner, have lower carcass weights, and have generally lower quality grades than those fed exclusively in a feedlot when slaughtered at similar ages.     

Effects of restricted versus conventional dietary adaptation on feedlot performance,carcass characteristics,site and extent of digestion,digesta kinetics,and ruminal metabolism

Three experiments were conducted to determine effects of restricting intake of the final finishing diet as a means of dietary adaptation compared with diets increasing in grain over a period of 20 to 22 d on overall cattle performance, carcass characteristics, digestibility, digesta kinetics, and ruminal metabolism. In Exp. 1, 84 Angus x Hereford yearling steers (initial BW = 418 +/- 29.0 kg) were fed for 70 d. Restricting intake during adaptation had no effect (P > 0.10) on overall ADG:DMI, but decreased (P < 0.05) DMI compared with ad libitum access to adaptation diets, which resulted from differences during the initial 28 d of the experiment. In Exp. 2, 150 mixed crossbred steer calves (initial BW = 289 +/- 22.9 kg) were fed for an average of 173 d. Restricting intake decreased (P < 0.01) overall daily gain (1.51 vs 1.65 kg/d) and DMI (8.68 vs 9.15 kg/d) compared with ad libitum fed steers; however, ADG:DMI was not influenced (P > 0.10) by adaptation method. Experiment three used eight ruminally and duodenally fistulated steers (initial BW = 336 +/- 20 kg) in a completely random design. Total tract digestibility, digesta kinetics and ruminal metabolism were determined. Restricting intake reduced (P < 0.10) daily DMI variation from d 1 through 7, 8 through 14, and 22 through 28 compared with ad libitum feeding of three adaptation diets. Restricted steers had reduced (adaptation method x period interaction, P < 0.05) intakes and fecal excretions of ADF and greater OM digestibilities on d 4 through 7, 11 through 14, and 18 through 21. Digesta kinetics and ruminal metabolism were generally not affected (P > 0.10) by adaptation method. Our results suggest that restricted-feeding of the final diet as a means of dietary adaptation can be used in finishing cattle with few problems from acidosis or related intake variation. In light-weight steers (Exp. 2), disruptions in intake during the adaptation period might have resulted in restriction for an extended period, which decreased (P < 0.01) hot carcass weight compared with calves fed ad libitum. Effects of limit feeding during the initial 28 d of the feeding period on site and extent of digestion, digesta kinetics, and ruminal metabolism were minimal, supporting few differences in performance across the finishing period for yearling cattle.     

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 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.     

Duodenal nutrient flow and digestibility in Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silage at two intakes

Formaldehyde- and formic acid-treated alfalfa or orchardgrass silage were fed at 65 and 90 g DM/kg BW.75.d) to growing Holstein steers (209 +/- SE = 35 kg) fitted with permanent ruminal and duodenal cannulas in a 4 x 4 latin square. Alfalfa had higher (P less than .01) concentrations of cell solubles, total N and rumen-soluble N than did orchardgrass. Digestible energy (Mcal/d), total N and soluble N intake (g/d) were higher (P less than .05) for steers fed alfalfa than for those fed orchardgrass. Total duodenal OM, DM, NDF, N and non-NH3-N flows were greater (P less than .001) for steers fed alfalfa than for those fed orchardgrass and were greater (P less than .001) at high vs low intake. Duodenal bacterial N flow (g/d) was greater (P less than .001) for steers fed alfalfa than for those fed orchardgrass, and bacterial N synthesis (g/kg DM truly digested in the rumen) was 58 and 32, respectively (P less than .001). Ruminal concentrations of NH3-N (P less than .001) and VFA (P less than .05) were greater for steers fed alfalfa than for those fed orchardgrass. Total tract DM, energy and N digestibilities were higher (P less than .05) for steers fed alfalfa vs orchardgrass, whereas total tract NDF digestibility was lower (P less than .01). Tissue N retention tended to be greater (P less than .1) for steers fed alfalfa than for those fed orchardgrass. Regression analysis indicated that duodenal non-NH3-N flow was related to intake of metabolizable energy and soluble N (R2 = .939). Improved performance and higher efficiency of use of ME for tissue gain by steers fed alfalfa rather than orchardgrass is related to lower ruminal acetate:propionate, higher microbial efficiency and greater duodenal DM and N flows.     

Source and level of energy supplementation for yearling cattle fed ammoniated hay

Brahman x British crossbred steers were used in growth and digestion trials to evaluate the response of source (corn, sugar cane molasses, or soybean hulls) and feeding rate (0, 1.4, or 2.8 kg DM per steer daily in the growth trials; 0, 15, or 30% of the ration DM in the digestion trial) of energy supplementation in cattle fed ammoniated (4% of forage DM) stargrass (Cynodon nlemfuensis Vanderyst var. nlemfuensis) hay. Cattle on all treatments were fed 0.5 kg cottonseed meal daily. In the growth trials, steers grazed dormant bahiagrass (Paspalum notatum) pasture. Increasing the levels of supplementation decreased hay intake but increased total dietary intake for all diets (P < 0.07). Daily gain and feed efficiency of steers were improved (P < 0.03) with supplementation. Steers supplemented with corn or soybean hulls at 2.8 kg DM/d had a higher ADG (0.92 kg) and gain/feed (0.103) than steers supplemented with molasses (0.78 kg, 0.08, respectively) at the same level. Seven crossbred steers (200 kg) were used in a five-period digestion trial to evaluate apparent OM, NDF, ADF, and hemicellulose digestibility. Apparent OM digestibility of all diets increased linearly (P = 0.02) as the level of supplementation increased. Apparent NDF and ADF digestibility decreased (P < 0.03) as the level of supplementation with corn or molasses increased, whereas increasing the level of soybean hulls in the diet increased (P < 0.06) apparent NDF and ADF digestibility. Four ruminally fistulated crossbred steers (472 kg) were used in a 4 x 4 latin square design to investigate ruminal characteristics with energy supplementation at 30% of ration DM. Ruminal pH in steers supplemented with soybean hulls or corn declined after feeding. Ruminal pH decreased more rapidly with corn supplementation and remained below 6.2 for a longer period of time than with the other diets. Ruminal pH did not change within 24 h after feeding for steers fed the control or molasses diets. No change in total VFA concentration was observed in steers fed molasses or corn. Total ruminal VFA concentration in steers supplemented with soybean hulls increased initially after feeding and then declined within 24 h after feeding. Soybean hulls produced fewer negative associative effects than corn when fed with ammoniated stargrass hay at 2.8 kg DM/d. The reduced gain/feed of steers supplemented with molasses compared to soybean hulls or corn indicates that molasses was not utilized as efficiently as the other energy sources.     

Evaluation of various nitrogen supplements in starter diets for growing Holstein steers and their effects on ruminal bacterial fermentation in continuous culture

Concurrent in vivo and in vitro studies were conducted to evaluate urea (U), soybean meal (SBM), ground soybeans (RAW), extruded soybeans (ES) or extruded soybeans plus urea (ES + U) as primary supplemental N sources in starter diets for Holstein steers. Three groups of 48 Holstein steers each were fed five different starter diets to 181 kg BW in three experimental periods over 2 yr. Average daily gains were similar (P greater than .05) for steers fed ES + U (1.12 kg), ES (1.08 kg) and SBM (1.09 kg) but lower (P less than .05) for those fed U (1.00 kg) or RAW (.97 kg) diets. Feed/gain was similar (P greater than .05) for ES-fed steers vs those fed other diets except U. From 181 to 477 kg, all steers were fed the same diet. Steers fed the RAW starter diet had the lowest (P less than .05) ADG for the entire period. The starter diets were used as substrates for ruminal microbial metabolism in eight dual-flow continuous culture fermenters. True OM digestion was higher and NDF and ADF digestion was lower (P less than .05) for the ES + U diet than for the ES diet. Dietary protein degradation was lowest (P less than .05) for the ES diet (64.4%). Total bacterial N flow was higher (P less than .05) with the ES + U, SBM and U diets than with the ES diet. Lysine flow was higher (P less than .05) for the ES + U diet than for all other diets except ES. Results of these experiments indicate that ES as a protected ruminal escape N source with or without added urea did not improve steer performance above that obtained from SBM in starter diets.     

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.     

Energy components of growth in Holstein steers fed formaldehyde- and formic acid-treated alfalfa or orchardgrass silages at equalized intakes of dry matter

Energy retention was compared in Holstein steers fed either alfalfa or orchardgrass silages for 164 d at either 65 or 90 g DM/kg.75 BW daily in a 2 x 2 factorial. Energy retention was estimated by slaughter-balance using an initial kill of eight steers at 216 kg and a final kill of eight steers per treatment at 326 kg. The ADG was not affected (P greater than .05) by silage, but steers fed alfalfa gained less (P less than .001) gut fill (they lost gut fill) and gained more (P less than .001) of the following than steers fed orchardgrass: empty body, 23%; fat, 50%; fat-free matter, 18%; protein, 16%; water, 17%; ash, 43%; gross energy, 31%; and carbon, 38%. With retained energy at 1.15 Mcal/d, retained energy was equally distributed between fat and protein. Increments of daily retained energy greater than 1.15 Mcal were deposited as 76% to fat and 24% to protein; this distribution was not affected by silage. The energy requirement for maintenance, with BW adjusted to equal gut fill, was not different (P greater than .05) at 130 kcal ME/kg.75 BW for steers fed alfalfa vs 125 for steers fed orchardgrass. Although not significant (P greater than .05), retained energy/ME intake above maintenance was 13% greater for steers fed alfalfa (.261) than for steers fed orchardgrass (.230), which supports the difference observed by calorimetry. The difference in dietary protein (25.6 vs 20.5%) did not contribute to the difference in energy retention because the differences in fat and protein retention could be explained totally by differences in daily energy deposition. The higher NDF of orchardgrass, or other fiber components, seems to be the most probable cause of its somewhat lower partial energetic efficiency relative to alfalfa.     

Grazing methods and stocking rates for direct-seeded alfalfa pastures: II. Pasture quality and diet selection

A 2-yr study was conducted to determine the effects of two grazing methods (GM) and two stocking rates (SR) on alfalfa (Medicago sativa L. var. WL225) pasture quality and diet selection by Holstein steers. Eight pasture plots (.76 ha) were seeded in 1988 and divided into two blocks of four pastures each. Pastures were managed to allow a 36-d rest period with an average grazing season of 105 d. Before steers entered the next paddock, canopy heights (CH) of alfalfa plants were determined and pasture-forage samples were collected. Forage samples were analyzed for DM, OM, CP, and in vitro OM digestibility (IVOMD). At 12-d intervals beginning with the second grazing cycle, extrusa samples were collected from steers with esophageal fistulas. Extrusa samples were frozen, freeze-dried, and analyzed for OM, CP, IVOMD, in situ ruminal DM degradation, and ruminal undegradable protein. There were no effects of GM on alfalfa CH or pasture DM, OM, CP, and IVOMD. Increasing the SR increased pasture CP content in both years and increased DM, OM, and IVOMD in the 2nd yr. There was no effect of GM or SR on the quality of forage selected by esophageally fistulated steers. Esophageally fistulated steers selected forage that had greater OM, CP, and IVOMD than the average nutrient content of the forage. Although forage quality was greater when stocking rates were increased, the quantity of forage available per animal may have limited gains.     

Feeding high-moisture corn instead of dry-rolled corn reduces odorous compound production in manure of finishing beef cattle without decreasing performance

We hypothesized that feeding steers ground high-moisture ensiled corn (HMC) in lieu of dry-rolled corn (DRC) would reduce the amount of starch being excreted in the manure and the associated odorous compound production. One hundred forty-eight crossbred steers (363 +/- 33 kg of BW) were fed a DRC-or HMC-based diet in a feeding trial, and 8 Charolais-sired steers (447 +/- 22 kg of BW) were used in a nutrient balance study. Steers fed HMC tended to have a slightly lower DMI (P = 0.09), ADG (P = 0.06), and yield grade, but G:F, final HCW, and quality grade did not differ (P > or = 0.23) between treatments. Compared with feeding DRC, feeding HMC decreased (P = 0.02) starch intake from 5,407 to 4,846 g/d, decreased (P < 0.01) fecal excretion of starch from 448 to 292 g/d, and increased (P = 0.03) starch digestibility from 91.7 to 94.1%. Nitrogen intake was greater (P < 0.01) for steers fed DRC than HMC in both studies, but N retention did not differ (P = 0.55). Heat production and energy retention did not differ between the 2 treatments (P > or = 0.55). In manure slurries incubated for 35 d with soil and water, total VFA concentration was lower (P < 0.01) in manure from steers fed HMC (1,625 micromol/g of DM) compared with steers fed DRC (3,041 micromol/g of DM). Lower initial (d 0) starch concentrations and greater initial pH was also observed in the slurries from the HMC manure. By d 3 of slurry incubation, there was an increase (P < 0.01) in free glucose and l-lactic acid in the DRC slurries but not in the HMC slurries. During manure incubation, alcohol and VFA content increased (P < 0.01) and pH declined, but to a lesser extent (P < 0.01) in the HMC slurries. However, branched-chain VFA increased more (P < 0.01) in the HMC slurries than in the DRC slurries. These data suggest that feeding HMC instead of DRC decreased fecal starch and production of some potentially odorous compounds in a finishing cattle system but had little impact on animal productivity.