Effects of implants on daily gains of steers wintered on dormant native tallgrass prairie, subsequent performance, and carcass characteristics

Fall-weaned crossbred steer calves (n = 300; 184 +/- 2.9 kg) received either no implant (Control) or were implanted with Synovex-C (SC = 10 mg estradiol benzoate + 100 mg progesterone), Synovex-S (SS = 20 mg estradiol benzoate + 200 mg progesterone), or Revalor-G (RG = 8 mg estradiol-17beta + 40 mg trenbolone acetate) to determine the effects of implants on weight gain during winter grazing on dormant tallgrass prairie, subsequent grazing and finishing performance, and carcass characteristics. Steers grazed two dormant tallgrass prairie pastures from October 16, 1996, until March 29, 1997 (164 d), and received 1.36 kg/d of a 25% CP supplement that supplied 100 mg of monensin/steer. Following winter grazing, all steers were implanted with Ralgro (36 mg zeranol) and grazed a common tallgrass prairie pasture until July 17 (110 d). After summer grazing, all steers were implanted with Revalor-S (24 mg estradiol-17beta + 120 mg trenbolone acetate), and winter implant treatment groups were equally allotted to four feedlot pens. Steers were harvested November 17, 1997, after a 123-d finishing period. Daily gains during the winter grazing phase averaged .28, .32, .32, or .35 kg/d, respectively, for Control, SC, SS, or RG steers and were greater (P < .01) for implanted steers than for Controls. Summer daily gains were similar (1.05 +/- .016 kg/d; P > or = .61) for all treatment groups. Feedlot daily gains were also similar (1.67 +/- .034 kg/d; P > or = .21), with implanted steers weighing 14 kg more than Control steers (P = .05) at harvest, despite similar management during summer grazing and feedlot phases. Control steers tended (P = .06) to have lower yield grades. There were no differences (P = .99) in marbling between implanted and nonimplanted steers. Steers implanted during the wintering phase had increased skeletal and overall (P < .01) carcass maturities compared with nonimplanted steers, which resulted in more "B" and "C" maturity carcasses. Because carcass maturity score affects quality grade, the increased maturities of implanted steers resulted in a $9.04 decrease in carcass value/100 kg (P < .01) compared with Controls. The results of this study indicate that growth-promoting implants are efficacious for cattle wintered on dormant native range despite low daily gains. This increased weight is maintained through the summer grazing and feedlot phases; however, the benefit of the increased weight may be offset by decreased carcass quality grade and value due to increased carcass maturity.     

Effect of supplementation frequency and supplemental urea level on dormant tallgrass-prairie hay intake and digestion by beef steers and prepartum performance of beef cows grazing dormant tallgrass-prairie

Effect of supplementation frequency and supplemental urea level on forage use (Exp. 1) and performance (Exp. 2 and 3) of beef cattle consuming low-quality tallgrass-prairie were evaluated. For Exp. 1 and 2, a 2 x 2 factorial treatment structure was used, such that two supplements (30% CP) containing 0 or 30% of supplemental degradable intake protein (DIP) from urea were fed daily or on alternate days. In Exp. 1 and 2, supplement was fed at 0.41% BW daily or at 0.83% BW (DM basis) on alternate days. For Exp. 3, a 2 x 4 factorial treatment structure was used, such that four supplements (40% CP) containing 0, 15, 30, or 45% of supplemental DIP from urea were fed daily or 3 d/wk. Supplements were group-fed at 0.32% BW daily or at 0.73% BW (DM basis) 3 d/wk. In Exp. 1, 16 Angus x Hereford steers (initial BW = 252 kg) were blocked by BW and assigned to treatment. Urea level x supplementation frequency interactions were not evident for forage intake, digestion, or rate of passage. Forage OM intake (OMI) and total digestible OMI (TDOMI) were not significantly affected by treatment. Total-tract digestion of OM (P = 0.03) and NDF (P = 0.06) were greater for steers supplemented daily. In Exp. 2, 48 Angus x Hereford cows (initial BW = 490 kg) grazing winter tallgrass prairie were used. Significant frequency x urea interactions were not evident for BW and body condition (BC) change; similarly, the main effects were not substantive for these variables. In Exp. 3, 160 Angus x Hereford cows (initial BW = 525 kg) grazing dormant, tallgrass prairie were used. Supplement refusal occurred for cows fed the highest urea levels, particularly for cows fed the supplement with 45% of the DIP from urea 3 d/wk, and supplement refusal increased closer to calving. A frequency x urea interaction (P = 0.02) was observed for prepartum BW changes. As supplemental urea level increased, prepartum BW loss increased quadratically (P = 0.02); however, a greater magnitude of loss occurred when feeding supplements containing > or = 30% of DIP from urea 3 d/ wk. Cumulative BC change followed a similar trend. In conclusion, moderate protein (< or = 30% CP) supplements with < or = 30% of supplemental DIP from urea can be fed on alternate days without a substantive performance penalty. However, infrequent feeding of higher protein (> 30% CP) supplements with significant urea levels (> 15% of DIP from urea) may result in decreased performance compared with lower urea levels.     

Pregnancy and lactation in beef heifers grazing tallgrass prairie in the winter: influence on intake, forage utilization, and grazing behavior.

Six ruminally and eight bifistulated (ruminal and esophageal) Hereford x Angus heifers were used to determine effects of pregnancy and early lactation on forage intake and utilization under grazing conditions. Three ruminally and three bifistulated heifers were bred (pregnant/lactating; P/L; average calving date was February 11, 1989); remaining heifers served as controls (C). The experiment consisted of three periods (P1 = average of 55 d before parturition; P2 = average of 12 d before parturition; P3 = average of 26 d after parturition). All heifers grazed the same 24-ha Flint Hills range pasture. Dehydrated alfalfa pellets were supplemented at .5% BW/heifer daily prepartum and at .8% BW/heifer daily postpartum. Treatment x period interactions were noted (P less than .10) for forage OM intake, ruminal capacity, indigestible ADF (IADF) fill, and grazing time but not for OM digestibility or IADF passage rate (P greater than .10). In P1 and P3, P/L heifers had greater (P less than .10) forage OM intake than C heifers, whereas no differences were noted (P greater than .10) in P2. Pregnant/lactating heifers spent less time (P less than .10) grazing than did controls in P2 and more time (P less than .10) than controls in P3. Ruminal IADF fill and ruminal capacity, as measured by water fill, tended (P = .14 and .16, respectively) to differ between the two groups in P2. Digestibility of OM was unaffected (P greater than .10) by physiological status, whereas IADF passage rate was greater (P less than .10) in P/L heifers. Only minor differences were noted for the chemical composition of diets selected by the two groups. Ruminal fermentation patterns shifted only slightly; the largest effects were in P3, when P/L heifers had greater (P less than .10) propionate and less (P less than .10) acetate (mol/100 mol) than C heifers. In summary, during the period just before parturition, differences in forage OM intake between P/L and C heifers disappeared, and ruminal fill and capacity tended to be lower for P/L heifers. Intake was 16% greater for P/L than for C heifers during the early postpartum period. Organic matter digestibility was not influenced by physiological status, even though IADF passage rates were greater for P/L heifers.     

Effects of ruminally degradable and escape protein supplements on steers grazing summer native range.

One experiment was conducted during 1989 to determine whether a deficiency exists for either ruminally degradable or escape protein in steers grazing summer native range. Increasing levels of ruminally degradable (.15, .27, and .37 kg/d) and escape protein (.07, .14, and .21 kg/d) replaced a cornstarch and molasses (energy control) supplement. Supplements were isoenergetic and fed individually to steers (.88 kg/d). No response to the degradable protein supplement (P = .15) was observed; however, a linear gain response (P less than .01) was observed in steers fed escape protein in addition to ruminally degradable protein. An in vitro study indicated that more (P less than .01) microbial protein was synthesized from the energy supplement than from the degradable protein; this finding presumably relates to the numerical decrease in weight gains observed for steers fed degradable protein supplements. Analyses of esophageal extrusa samples indicated that CP was relatively constant for the 1989 growing season compared with the 1988 growing season (P less than .05). Escape protein values differed (P less than .01) between years and among months within year. Forages that were apparently grazed in 1989 were never deficient in degradable protein. Additional gain observed from feeding escape protein would indicate that microbial protein synthesis may be insufficient to satisfy the metabolizable protein requirement, which probably limited gains by steers grazing summer native range.     

Effects of supplemental protein percentage and feeding level on intake, ruminal fermentation, and digesta passage in beef steers fed prairie hay.

Twelve ruminally cannulated steers (average initial BW 357 kg) were allotted to four treatments (three steers per treatment) in a replicated 4 x 4 Latin square design with 21-d periods (12 d for adaptation and 9 d for collection) to compare the effects of protein supplements that differed in percentage of CP and feeding level on low-quality forage utilization. Treatments were 1) control (C), ad libitum access to 5.6% CP prairie hay, 2) C +600 g of DM.steer-1.d-1 of a 43% CP supplement based on cottonseed meal (PS), 3) C + 1,200 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (GS), and 4) C + 600 g of DM.steer-1.d-1 of a 22% CP supplement based on corn grain and cottonseed meal (LS). Ruminal total VFA concentrations were increased 8% (P less than .07) by PS vs GS 1 h after supplementation. Among supplemented steers, ruminal acetate (mol/100 mol) was decreased 1.2 mol/100 (P less than .03) by GS vs PS and LS; however, supplementation did not affect (P greater than .10) acetate proportions compared with C. Neither propionate nor butyrate was affected (P greater than .10) by supplementation, but among supplemented steers, butyrate proportions were 8% greater (P less than .03) for GS than for PS and 5% less (P less than .10) for LS than for the average of GS and PS. Ruminal pH did not differ (P greater than .10) among treatments. Ruminal ammonia concentrations were increased 1.4 to 4.8 mg/100 mL (P less than .07) by supplementation and typically were less for LS than for PS and GS at most sampling times. Prairie hay DMI (average = 16.3 g/kg BW) was not affected (P greater than .10) by supplementation. Fluid dilution rate was 8% faster (P less than .01) when steers were supplemented than when they were not fed supplement, and fluid dilution rate was increased 4% (P less than .04) by GS compared with PS. Particulate digesta passage rate was not affected (P greater than .10) by treatment, but total tract retention time was decreased (P less than .01) 10% by supplementation. Extent and rate of prairie hay NDF digestion in situ were not greatly affected by supplementation, but in situ disappearance of supplement N was 6 to 10 percentage units less (P less than .06) for GS than for PS and 2 to 6 percentage units less for LS than for the average of PS and GS supplements.(ABSTRACT TRUNCATED AT 400 WORDS)     

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

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

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.     

Effects of supplemental silage on forage intake and utilization by steers grazing wheat pasture or bermudagrass

Seven trials were conducted to determine the effects of increasing amounts of silage (corn, wheat or sorghum) on forage intake, gastrointestinal tract fill, fecal output and ruminal flow and degradation of forage by cattle grazing wheat pasture or bermudagrass. In each of 3 yr, 24 steers grazed a common wheat or bermudagrass pasture and were randomly allocated to four treatments (0, .35, .70 or 1.05 kg silage DM.100 kg body weight-1.d-1). Intake and ruminal flow of forage were measured by feeding a single pulse dose of Yb-labeled forage followed by collection of fecal samples for 4 to 5 d and fitting Yb concentrations to a one-compartment, age-dependent model. Ruminal digestion kinetics of wheat forage were estimated in situ using eight ruminally cannulated steers fed 0 or .55 kg sorghum silage DM.100 kg body weight-1.d-1. Supplemental silage decreased wheat forage (P less than .10) and bermudagrass (P less than .01) intake linearly. However, total forage intake of bermudagrass plus silage increased linearly (P less than .05). Each kilogram of added silage DM decreased DM intake of wheat forage by .66 +/- .25 and of bermudagrass by .63 +/- .17 kg. Flow and turnover of wheat forage or bermudagrass were not altered (P greater than .15) by supplemental silage. Silage consumption increased extent of ruminal degradation of wheat forage DM (P less than .05; 63.1 vs 52.5%), indicating a positive associative effect of silage on wheat forage utilization.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of dietary energy level and supplemental protein source on performance of growing steers and nutrient digestibility and nitrogen balance in lambs

Four experiments were conducted to evaluate three crude protein (CP) sources (urea, U; soybean meal, SBM; corn gluten meal, CGM) in diets based on corn silage (high energy) or grass hay (low energy). In Exp. 1 and 2, growing steers were fed all combinations of energy and protein source at 10.5 or 12% CP. Steers fed high energy diets or 12% CP had improved (P less than .05) daily gains and feed:gain over 84 d. Protein source had no effect (P greater than .05) on performance except that steers fed U consumed more (P less than .05) feed than those fed CGM. Steers were fed experimental diets to a common weight and switched to an 85% concentrate diet for finishing. During finishing, steers fed low energy diets in the growing period consumed more (P less than .05) feed and had increased (P less than .05) feed:gain compared with those fed high energy diets. Growing lambs were fed the same diets as steers. At 10.5% CP, lambs fed high energy diets had higher (P less than .05) digestibilities of dry matter (DM), organic matter (OM), nitrogen (N) and fiber components, and retained more (P less than .05) N. For lambs on 12% CP, high energy diets had higher (P less than .05) DM and OM digestibilities and lower (P less than .05) N digestibilities. At 12% CP, energy level had no effect (P greater than .05) on N retained. Protein source had no effect (P greater than .05) on N retention. There appeared to be no advantage in supplementing with ruminally undegradable proteins, i.e. CGM, in these experiments.     

Effects of salinomycin on ruminal characteristics and performance of grazing beef steers

Grazing trials were conducted for 2 yr using weanling Brahman crossbred beef steers to evaluate graded levels of salinomycin (0, 50, 100 or 150 mg. head-1.d-1) for 161 d and to evaluate salinomycin in a free-choice mineral supplement (99 d). The 40 and 48 steers in trials 1 and 2 had average initial weights of 198 and 285 kg, respectively. In trial 1, steers were group-fed to consume either 0, 50, 100 or 150 mg of salinomycin.head-1.d-1 in .9 kg ground corn while grazing bermudagrass pastures. Both linear (P less than .01) and quadratic (P less than .05) effects were observed for steer performance as salinomycin level increased from 0 to 150 mg.head-1.d-1. Linear increases (P less than .01) in ruminal NH3-N (mg/100 ml) and in the molar proportion of propionate and decreases (P less than .01) in butyrate and acetate/propionate were detected. In trial 2, mineral supplements with and without salinomycin were fed free-choice to steers on bermudagrass pasture. The mean salinomycin intake of 38 mg.head-1.d-1 was lower than anticipated as a result of the instability of salinomycin in the mineral supplement and the slightly lower intake (65 g/d) than anticipated (75 g/d). Performance of steers was not influenced by salinomycin supplementation in trial 2. The ionophore salinomycin at intakes over 50 mg.head-1.d-1 appears to increase the performance of steers grazing bermudagrass pasture.     

The effects of several supplementation frequencies on forage use and the performance of beef cattle consuming dormant tallgrass prairie forage

Two experiments were conducted to quantify the impact on forage use and performance of varying supplementation frequency of cattle consuming forage diets across a range of frequencies. In both experiments, a common supplement was used that contained a relatively high concentration of CP (43%) and was fed at the following frequencies: 1) 2 d/wk; 2) 3 d/wk; 3) 5 d/wk; and 4) 7 d/wk. In Exp. 1, 120 Hereford x Angus cows (BW = 537 kg) grazing winter tallgrass-prairie range were supplemented at the various frequencies from December 7 until calving (average calving date = 3/7/99). All treatments provided the same quantity of supplement on a weekly basis (12.74 kg, as-fed) but divided the amount delivered on a given day equally among the number of supplementation events for that treatment. Less BW was lost from December 7 through calving (linear effect, P = 0.02) as frequency of supplementation increased, but the magnitude of difference in weight change was relatively small. Body condition responded similarly through early February (linear effect, P = 0.02), although treatment effects were not as distinct at calving (cubic effect, P = 0.11). In Exp. 2, 16 ruminally fistulated Hereford x Angus steers (BW = 257 kg) were blocked by weight and assigned to one of the four frequencies of supplementation. Steers were offered tallgrass prairie hay (73.5% NDF, 4.8% CP) ad libitum and were supplemented at a rate (relative to BW) similar to that of the cows in Exp. 1. Increasing frequency of supplementation increased (linear effect, P < or = 0.02) forage OM intake, OM and NDF digestion, and digestible OM intake. However, the most prominent differences in forage OM intake tended (cubic effect, P = 0.07) to occur with the two extreme frequencies of supplementation. In conclusion, forage use was improved with an increased frequency of supplementation, but the impact on performance is not likely to be large unless extreme differences in frequency occur.     

Ruminal degradation kinetics,intake, digestibility,and feeding behavior of beef steers offered annual or perennial grass-hay with or without supplementation

Effects of dried distillers grains plus solubles (DDGS) on ruminal fermentation, degradation kinetics, and feeding behavior of steers offered annual (Eragrostis tef; TEFF) or perennial (Bothriochloa bladhii; OWB) grass hay were evaluated. Ruminally cannulated Angus crossbred steers (n = 6; body weight [BW] = 304 ± 11 kg) were assigned to a 4 × 6 unbalanced Latin square design with four treatments arranged as a 2 × 2 factorial: hay type (OWB or TEFF) and DDGS supplementation (0% or 0.5% BW [dry matter {DM} basis]). Steers had ad libitum access to hay. Periods consisted of a 14-d adaptation followed by 7 d of collection. Residues from the in situ incubations (0, 3, 6, 12, 24, 36, 48, 72, and 96 h post-feeding) were fitted to a first-order kinetics model using the NLIN procedure of SAS. The DDGS decreased (P < 0.01) TEFF DM intake (DMI) by 11.3%, while not affecting DMI of OWB. The greatest DMI was observed for steers supplemented with DDGS, regardless of forage, and least in steers consuming OWB without DDGS (hay type × DDGS; P = 0.03). Non-supplemented steers spent more (P < 0.01) time eating hay. Digestibility of DM tended (P = 0.06) to increase with DDGS supplementation. A hay type × DDGS interaction was observed (P ≤ 0.05) on ruminal effective degradable fractions. The rate of degradation, soluble fraction, and the potentially degradable fraction of organic matter (OM), neutral detergent fiber, and acid detergent fiber (ADF) increased (P ≤ 0.05), while the undegradable fraction of all components decreased (P ≤ 0.01) when steers were offered TEFF compared to OWB. Ruminal DM, OM, and ADF degradation lag-time increased (P ≤ 0.02) in steers offered OWB. Ruminal degradation kinetics were not (P ≥ 0.17) independently affected by DDGS supplementation. Average ruminal pH of steers offered TEFF (P < 0.01) and those offered DDGS (P < 0.01) were lower than OWB and non-supplemented steers. Total concentration of VFA tended (P = 0.09) to increase when DDGS was provided with OWB, while decreasing when TEFF was offered. The acetate:propionate increased (P < 0.01) with DDGS supplementation due to a decrease (P = 0.03) in propionate. Ruminal NH₃-N was greater (P = 0.03) in steers offered TEFF compared to OWB, and those supplemented with DDGS (P = 0.03). An annual, in place of a conventional, perennial hay improved intake and digestion of nutrients, without affecting feeding behavior. The supplementation with DDGS appears to affect forage intake, ruminal degradation, and feeding behavior, although not independent of forage quality.     

Effect of energy source and ruminally degradable protein addition on performance of lactating beef cows and digestion characteristics of steers

Two trials were conducted to determine the effect of energy source (ENG) and ruminally degradable protein (RDP) on lactating cow performance and intake and digestion in beef steers. In Trial 1, 78 cow-calf pairs were used in a 2 x 2 factorial design to determine the effect of ENG (corn or soyhulls; SH) and RDP (with our without sunflower meal) to a forage diet for lactating beef cows. The basal diet consisted of 75% grass hay (11.5% CP) and 25% wheat straw (7.4% CP). Supplement treatments and predicted RDP balances were corn (-415 g of RDP/d); SH (-260 g of RDP/d); corn plus RDP (0 g of RDP/d); or SH plus RDP (0 g of RDP/d). Data were analyzed as a split-plot in time, with pen as the experimental unit (two pens per treatment). No interaction between ENG and RDP was present (P > 0.08) for any response variable. No differences (P > 0.39) due to ENG or RDP were noted for BW, BCS, or milk yield; however, final calf weight tended to increase with ENG (P = 0.06). In Trial 2, a 5 x 5 Latin square was used to determine effects of ENG and RDP on intake and digestion in steers (686 +/- 51 kg BW). Treatments were arranged as a 2 x 2 plus one factorial and comprised a control (CON; grass hay, 7% CP), grass hay plus 0.4% BW SH, grass hay plus 0.4% BW SH and 0.15% BW sunflower meal, grass hay plus 0.4% BW corn, and grass hay plus 0.4% BW corn and 0.2% BW sunflower meal. Preplanned contrasts included main effects of ENG and RDP, ENG x RDP interaction, and CON vs. supplemented (SUP) treatments. Supplementation increased total DMI compared with CON (P = 0.001), but forage DMI was greater (P = 0.001) for CON than for SUP. An ENG x RDP interaction occurred for forage DMI (P = 0.02); addition of RDP to corn decreased forage intake, whereas addition of RDP to SH had no effect. There was an ENG x RDP interaction (P = 0.001) for ruminal pH; pH tended to increase with RDP addition to SH (P = 0.07), but decreased with RDP addition to corn (P = 0.001). Supplementation increased ruminal ammonia compared with CON (P = 0.001). Likewise, RDP increased ruminal ammonia (P = 0.001). An interaction occurred for OM disappearance (OMD; P = 0.01). The RDP addition to SH numerically decreased OMD (P = 0.23), whereas RDP addition to corn numerically increased OMD (P = 0.14). Intake and digestion seem to respond differently to RDP addition depending on supplemental energy source. Both corn or SH seem to be suitable supplements for the quality of forage used in this trial. Addition of supplemental protein did not improve cow or calf performance.     

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

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

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 residual and reapplied biosolids on performance and mineral status of grazing beef steers

An experiment was designed to assess the mineral status of 60 Angus yearling beef steers grazing bahiagrass pastures fertilized with large amounts of biosolids from three sources: Baltimore, MD; Tampa, FL; and Largo, FL. Biosolids were classified as exceptional quality and thus had no regulatory restrictions on loading rate. They differed primarily in concentration of Mo (12 to 56 mg/kg of DM). Residual treatments (biosolids applied only the previous year) for Baltimore biosolids were applied at 22.4 and 44.8 t/ha, and Tampa biosolids were either 16.8 or 33.6 t/ ha. The reapplied treatments (applied in consecutive years) for both Baltimore and Tampa sludges were applied at 22.4, 44.8, 16.8 , and 33.6 t/ha, respectively. The two Largo biosolids treatments were either 56 or 112 t/ha and were applied only in the 2nd yr. Liver biopsies and blood samples were collected on d 1, 95, and 180. Liver and plasma were analyzed for minerals and blood was analyzed for hemoglobin, hematocrit, and superoxide dismutase of polymorphonuclear neutrophils. Experimental animals were generally adequate in macromineral status and Co, Fe, and Mn throughout the experiment. Copper deficiency was evident based on the clinical signs of hair coat discoloration, very low plasma Cu at d 95, and the continuous decline in liver Cu over 180 d. A sharp decline in plasma Cu was observed for all treatments from d 1 to 95, after which Cu concentrations rebounded to normal concentrations (> 0.65 microg/mL) by d 180. Liver Mo was well below concentrations indicating toxicity (> 5.0 mg/kg). The steep decline in liver Cu over the first 95 d reflects the dietary Cu deficiency and the possibility of high forage S (0.26 to 0.52%) interfering with Cu metabolism. Biosolids application to bahiagrass pastures was not detrimental to mineral status except for declining Cu stores; however, the controls likewise declined, but to a lesser degree.     

Effects of different grazing and feeding periods on performance and carcass traits of beef steers

Over three consecutive years, 180 (60/yr) fall-born steer calves were weaned in May (average initial BW = 238 kg, SD = 36.2 kg) and allocated to one of three groups: 1) calf-fed steers that entered the feedlot at weaning; 2) short yearlings that grazed irrigated pasture for another 4 mo and entered the feedlot in September; and 3) long yearlings that grazed with short yearlings during the summer, remained on annual California foothills range through the fall, winter, and spring, and entered the feedlot the following May. All steers were fed until the average group backfat (BF), determined by ultrasound, reached 11 to 12 mm. On pasture, short- and long-yearling steers gained weight in the summer; long yearlings then slightly lost weight in the fall and winter, and then gained weight again the following spring. Average days in the feedlot were 188, 158, and 94 (P < 0.10) for calves, short yearlings, and long yearlings, respectively. Feedlot DMI increased with age (and weight) at feedlot entry, with no difference among groups in gain:feed ratio. The gain of BF was nil on pasture, even when animals were gaining weight, and then increased rapidly when animals were placed on a high-energy diet. Final body weights were heaviest (P < 0.10) in long yearlings, followed by short yearlings and then calves, indicating that a prolonged growing period increases the apparent mature size of the animal. Moreover, total carcass fat contents and percentage of Choice or above were all lower (P < 0.10) in cattle that were older at feedlot entry (i.e., long yearlings) compared with the other groups. In conclusion, increasing the backgrounding period decreased time and total concentrate requirements in the feedlot of Angus-Hereford steers. Older cattle reached 10 mm of BF at heavier weights. Grazing animals gained weight without increasing BF; however, BF increased rapidly in the feedlot. Prolonged grazing may decrease quality grade, either by impairing the ability of the animal to deposit intramuscular fat or by decreasing the time during which dietary energy supply is adequate for intramuscular fat deposition to occur.     

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.     

Influence of condensed tannin on intake, digestibility, and efficiency of protein utilization in beef steers fed high concentrate diet

This trial was conducted to evaluate if the effect of condensed tannin (CT) is associated with a true protein source on intake, ruminal and total digestibility, ruminal digestion rate, protein efficiency, and microbial efficiency in beef steers fed high concentrate diet (87% of DM). Four Bos indicus steers (407 ± 12 kg of BW) fitted with rumen cannula were assigned to a 4 × 4 Latin square design, arranged in a 2 × 2 factorial arrangement. Treatments consisted of either inclusion (0.4% of DM) or exclusion of condensed tannin (CT) from quebracho extract (76% of CT) with or without the use of soybean meal (SBM) as source of true protein. The level of inclusion was calculated to provide a daily intake of 1 g/10 kg of BW of CT. Intake of DM and nutrients was not affected (P > 0.10) by CT inclusion. However, there was an effect (P < 0.10) of CT inclusion on ether extract digestibility. An interaction (P < 0.10) was observed between CT and SBM on ruminal digestibility and digestion rate of crude protein (CP): when mixed with soybean meal, CT decreased the ruminal digestibility and, consequently, reduced the digestion rate of CP. Intake of CP increased (P < 0.10) with the inclusion of SBM. No differences in DM passage rate were observed (P > 0.10) among treatments. Effects of the interaction (P < 0.10) between CT and SBM were observed on flux of rumen undegradable protein (RUP), metabolizable protein (MP), and on the ratio MP:CP. In the presence of soybean meal, the addition of CT increased (P < 0.10) the flux of RUP and MP, and improved the ratio MP:CP. The yield of microbial protein on the abomasum and the microbial efficiency did not differ among treatments (P > 0.10). There was no difference (P > 0.10) on the pH, VFA, and ruminal ammonia (N-NH₃) with the addition of condensed tannin. The N-NH₃ increased and the ruminal pH decreased with the inclusion of soybean meal (P < 0.10). The utilization of condensed tannin as an additive in beef cattle diets with high level of concentrate and soybean meal as a source of true protein implies positive effects on crude protein utilization, decreasing digestion rate and ruminal digestibility of crude protein and consequently increasing the levels of metabolizable protein, with no changes in the ruminal fermentation parameters.