Indigestible ADF Research Articles

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.

Technical note: sampling technique and drying method effects on chemical composition of tall fescue or fescue-ladino clover pasture samples.

Although esophageal extrusa is the most readily accepted representation of forage consumed by grazing ruminants, esophageal sampling is demanding from the standpoint of animal care and maintenance and extrusa processing. This experiment was conducted with a split-plot design to evaluate the effects of pasture type, pasture sampling technique and drying method on estimation of grazed forage composition. Ten esophageally fistulated steers grazed pastures of either tall fescue (Festuca arundinacea Schreb.) or tall fescue interseeded with ladino clover (Trifolium repens L.); steers were closely observed during four collection periods to determine their exact grazing location. Forage samples were collected either directly from the esophageal fistula (E) or hand-gathered (HG) from the immediate perimeter of the grazed area. Samples of E and HG from each steer were divided and oven-dried at 40 degrees C or lyophilized. Fescue samples had lower (P less than .01) N and ADF N concentrations than fescue-ladino clover samples, and E-collected fescue samples had lower (P less than .05) in vitro digestible OM than E-collected fescue-ladino clover samples. Sampling x drying method interactions were detected (P less than .01) for OM, NDF, ADF, hemicellulose (HEMI), ADL, alkaline peroxide lignin (APL), ADFN and indigestible ADF (IADF). Oven-dried E had higher (P less than .05) NDF, ADF, HEMI, ADL, APL and ADF N than lyophilized E; ADF N and IADF were higher from oven-dried HG than from lyophilized HG. In vitro digestible OM was not modified by oven drying. Hand-gathered samples, whether lyophilized or oven-dried, did not simulate E dried by lyophilization. Standardized collection techniques and drying procedures should be implemented to minimize damage to fibrous components.

Mefluidide treatment of tall fescue pastures: intake and animal performance.

Twelve Hereford heifers were used in a grazing experiment to determine intake and digestibility of tall fescue forage treated with the plant growth regulator mefluidide. Additionally, steer and heifer performance were evaluated after grazing tall fescue pastures or consuming hay harvested from pastures treated with mefluidide. Average forage OM intake by heifers was 47% greater (P less than .05) during July and 50% greater (P less than .05) during August for mefluidide-treated pastures than for untreated pastures. In vitro OM digestibility and indigestible ADF were compared for their ability to predict forage intake. The in vitro digestibility method produced more realistic intake data than the indigestible ADF method; however, trends in estimated forage intake were similar for both methods. Total tract particulate matter passage rates were similar (P greater than .10; 4.5 vs 4.1%/h), but mean retention times were shorter (P less than .05; 37.0 vs 46.9 h) when heifers grazed mefluidide-treated tall fescue. Steers grazing mefluidide-treated forage had greater (P less than .05) total weight gains than did steers grazing untreated tall fescue during a 168-d study (86 vs 69 kg). Heifers fed hay harvested from mefluidide-treated pastures also exhibited similar improvements in gain (49 vs 38 kg) because of increased (P less than .05) forage consumption (8.3 vs 7.3 kg/d) and greater (P less than .05) forage OM digestibility (65 vs 61%). Mefluidide treatment of tall fescue in early spring prolonged higher-quality herbage into midsummer and resulted in greater forage intake and animal 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.

Steam-rolled wheat diets for finishing cattle: effects of dietary roughage and feed intake on finishing steer performance and ruminal metabolism.

Two experiments were conducted to determine the influence of dietary roughage concentration and feed intake on finishing steer performance and ruminal metabolism. In Exp. 1, 126 steers (334 kg) were used in a completely randomized design and fed (120 d) diets of steam-rolled wheat without roughage or containing 5, 10 or 15% roughage (50% alfalfa hay:50% corn silage). Steers fed 5 or 10% roughage gained faster (quadratic, P less than .05) and were more efficient (quadratic, P less than .05) than steers fed 15% or no roughage. In Exp. 2, six ruminally cannulated steers (447 kg) were used in a 6 x 6 latin square design and fed (twice daily) diets of steam-rolled wheat without roughage or containing 5 or 15% alfalfa hay at twice or three times NE required for maintenance. Increasing dietary roughage increased (linear, P less than .01) ruminal liquid passage 38%, indigestible ADF passage 63%, Yb-labeled wheat passage 75% and fiber fill 31%. The rate of in situ starch digestion tended to increase (linear, P = .16), and ruminal VFA concentration was 40 mM higher (P less than .01) at 4 h after feeding with increased roughage. Increased feed intake increased (P less than .05) ruminal starch fill, fiber fill, liquid fill and liquid passage 23%, Yb-labeled wheat passage 50% and Dry-labeled hay passage 20%. It reduced protozoa five- to sixfold (P less than .01) but doubled total bacterial counts (P less than .01). Ruminal NH3N was lower (P less than .01) and total VFA concentration was 50 mM higher (P less than .01) at 4 h after feeding. The acetate:propionate ratio was reduced from 2.3 to 1.3 (P less than .01) with increased intake. Adding roughage to a steam-rolled wheat diet increased passage and tended to increase rate of starch digestion; increased feed intake with its associated effects on ruminal fill and passage dramatically shifted the microbial population and fermentation end products.