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© 2008 Plant Management Network. Bermudagrass Hay Intake of Beef Cattle Supplemented with Corn or Soybean Hulls David G. St. Louis, Research Animal Scientist, South Mississippi Branch, Mississippi State University, Poplarville 39470; and Michael E. McCormick, Resident Coordinator, Dairy Scientist, Louisiana State University Agricultural Center, Southeast Research Station, Franklinton 70438 Corresponding author: David G. St. Louis. stlouis@ra.msstate.edu St. Louis, D. G., and McCormick, M. E. 2008. Bermudagrass hay intake of beef cattle supplemented with corn or soybean hulls. Online. Forage and Grazinglands doi:10.1094/FG-2008-0519-01-RS. Abstract Three supplementation trials were conducted to test the accuracy of National Research Council dry matter intake (DMI) predictions. Alicia bermudagrass (Cynodon dactylon) hay was fed ad libitum with cracked corn (Zea mays) or soybean hulls (Glycine max) as energy supplements. Three treatments in each trial were: bermudagrass hay plus cracked corn at 0.8% of body weight (BW) (BG + C); bermudagrass hay plus soybean hulls at 1.6% of BW (BG + H); and a control treatment of hay alone (BG). Diets BG + C and BG + H were predicted to provide equal amounts of energy because supplements were expected to substitute for DMI of hay. In the three trials, using cows and heifers and hay of two different qualities, diets were not equal in energy because supplements were mostly additive to hay DMI. In Trial 1, cow DMI of hay was 1.82, 1.63, and 1.79% BW for BG + C, BG + H, and BG, respectively. In Trial 2, DMI for cows was 1.14, 1.15, and 1.23% BW for BG + C, BG + H, and BG, respectively. Heifers in Trial 3 had similar DMI as cows. The Beef NRC equations, from which these diets were formulated, overestimated DMI of hay alone and were not accurate in predicting the additive and substitutive effects of supplementation. Introduction Bermudagrass typifies the hay and summer pasture that most farmers in the southeastern United States grow to feed their cattle. It is generally inadequate in protein and/or energy to meet nutrient requirements of growing or lactating ruminants (13). Therefore, supplementation with grains and grain by-products is often necessary to enhance animal performance and farm profits. Farmers should be able to use resources such as National Research Council (NRC) requirements for beef cattle (14) to guide decision making about which feedstuffs and amounts to use as supplements for animals consuming low-quality forages, but in some cases these resources fail to accurately predict forage intake when grasses like bermudagrass are fed with various supplements (4,5,8). When starch is the primary energy form in supplements, the digestibility of warm-season grasses often is decreased resulting in lesser forage DMI and animal performance than expected (4,5,8). Reduced forage fiber digestion and intake have been observed when low-quality forage is supplemented with a rapidly degraded energy feed stuff such as corn or molasses (4,5,6,8,16). Supplements with slower energy degradation such as soybean hulls may not substantially decrease forage digestibility or intake (10,17). The objective of this study was to test the accuracy of the Beef Cattle NRC (14) intake predictions when animals fed low-quality forages received corn or soybean hulls as energy supplements. Animals and Environment Three trials were conducted at the South Mississippi Experiment Station, Poplarville, MS (30°47'N, 89°41'W) to measure ad libitum intake of Alicia bermudagrass hay when supplementing with cracked corn or soybean hulls. Animals were housed in tree-shaded pens from June through September for Trial 1 and from August through November for Trials 2 and 3. Intake of weeds and grass in the pens was prevented by applications of glyphosate herbicide. Mud problems were negligible as feeders were moved when necessary. At this location, the 30-year monthly minimum temperatures range from 41°F to 71°F and maximum temperatures range from 63°F to 92°F. Mature 1100-lb, commercial, mixed breed, non-lactating, non-pregnant beef cows with body condition scores (BCS) ranging from 4 to 7 (9-point scale) were used in Trials 1 and 2 while growing 650-lb, commercial, mixed breed, non-pregnant, beef heifers (BCS 4 to 5) were used in Trial 3. The fields used to produce hay for these trials were fertilized with 85, 50, 100, and 24 lb/acre of N, P2O5, K2O, and S, respectively, in April. Soil pH was approximately 5.8. Weeds were controlled with paraquat (0.25 lb/acre) in March and Grazon P + D (Dow Chemical Co., Midland, MI) (2 pints formulation/acre) in April. The first cuttings, taken in June for all trials, were baled into small square bales and stored in a barn until feeding. Diet Formulation Hay DM digestibility was 57.5% for Trial 1 and 52.8% for Trials 2 and 3 with NDF digestibilities 65.1 and 53.9%, respectively (15). Using the Beef NRC (14), intake equations and nutrient analyses of the hay, corn, and soybean hulls (Table 1), the goal for Trial 1 was to provide energy and protein to meet 161% of maintenance requirements, the nutrient requirements of a lactating beef cow during the time when need for supplementation is greatest and is most critical to efficient production. Three treatments were: bermudagrass hay plus corn (BG + C); bermudagrass hay plus soybean hulls (BG + SH); and a control treatment of hay alone (BG). Table 1. Nutrient composition (%, DM) of cracked corn, soybean hulls, soybean meal, and bermudagrass hay fed to cattle for different treatments
* NDF = neutral detergent fiber, ADF = acid detergent fiber, CP = crude protein, NEm = net energy for maintenance (Mcal/kg), NEg = net energy for gain (Mcal/kg). In Trial 1, mature cows were supplemented with 9 lb of corn or 18 lb of soybean hulls in BG + C or BG + SH, respectively. These amounts of supplements are predicted by Beef NRC (14) to provide equal amounts of energy to the BG + C and BG + SH diets when feeding bermudagrass hay free choice. These supplements are predicted to have large substitutive and minimal additive effects to hay DMI. Because the bermudagrass hay in Trials 2 and 3 was deficient in protein, digestible intake protein (DIP) requirements were met by adding soybean meal so that DIP would not be a confounding factor in intake of bermudagrass hay. Trials 2 and 3 were able to compare two classes of animals with the same hay. Although hay was of lower quality, energy supplementation was not increased over that of Trial 1 because substitutive effects on hay DMI might increase with more supplementation and become a confounding factor in comparing Trials 1 and 2. Mature cows in Trial 2 were supplemented with 8.1 lb of corn plus 0.9 lb soybean meal (SBM) or 16.2 lb of soybean hulls plus 1.8 lb SBM in BG + C or BG + SH, respectively. Growing heifers in Trial 3 were supplemented with 4.8 lb of corn plus 0.5 lb SBM or 9.6 lb of soybean hulls plus 1.1 lb SBM in BG + C or BG + SH, respectively, approximately 161% of maintenance. Measurements Animals were pen-fed each morning with 4 animals per pen of mature cows and 6 animals per pen of growing heifers. After 32 days of acclimation to the diet and facilities, intake of hay and supplements was determined daily for 10 days by subtracting orts (feed left over) from feed offered the previous day. Solid steel covered self-feeders, similar to grain self-feeders except without tapered sides, were custom designed and built for feeding unchopped hay. Spillage and wastage were negligible. Supplements were consumed completely, but hay was fed in excess to result in 5% orts. Samples were taken daily for dry matter (DM) determination of hay offered and hay refused. Intake was expressed in DM as a percent of shrunk body weight, determined after withholding feed and water for 24 h. Statistical Analysis Trial 1 was a 3 Χ 3 Latin rectangle design with treatment arrangement different for the two replicates to test for dietary carryover effects (Table 2). Trials 2 and 3 were each 3 Χ 3 Latin squares with the same treatment arrangement with time periods and groups of animals forming squares. Inherent in the Latin square design are the period/groups that serve as replicates of the treatments. Data were analyzed using the MIXED procedure of SAS (V9.1, SAS Institute Inc., Cary, NC) with fixed periods and treatments and random groups of animals. There were no carryover effects (P = 0.42) as animals in Trial 1 were rotated among treatments, indicating that a 32-day acclimation period was sufficient and replication of the Latin square (Latin rectangle) was not necessary in Trials 2 and 3. Table 2. Arrangement of treatments in the 3 Χ 3 Latin rectangle design of Trial 1.*
* Treatments are bermudagrass hay plus corn (BG + C), bermudagrass hay plus soybean hulls (BG + SH), and a control treatment of hay alone (BG). In Trials 2 and 3, arrangement of treatments was the same as Replicate 1 above. Associative Effects When feeding forages to beef cattle and supplementing with other feeds, associative effects are characterized as either substitutive or additive. Substitution occurs when total nutrients from the forage (dry matter, energy, protein) are reduced by supplementation. Additive effects are the difference between total diet nutrients and forage alone. Associative effects between supplements and forages on intake, digestibility, and subsequent animal performance are affected by many factors (digestion rates of carbohydrates and protein, particle size, feed density, etc.). This study found cracked corn, when fed at approximately 0.8% of body weight (BW), and soybean hulls, when fed at approximately 1.6% of BW, to have mostly additive effects on dry matter intake (DMI) when used as supplements to cattle receiving ad libitum intake of bermudagrass hay (Table 3). These findings do not agree with those of other researchers (1,2,3,6,8,16) who observed reduced forage intake when low-quality forage was supplemented with a rapidly degraded energy feedstuff such as corn or molasses. Table 3. Cattle body weight (BW) and observed dry matter intake (DMI) of diet ingredients for different treatments.*
x Within rows, means not followed by a common letter differ (P < 0.01). Treatments are bermudagrass hay plus corn (BG + C), bermudagrass hay plus soybean hulls (BG + SH), and a control treatment of hay alone (BG). y Shrunk BWs are the average of 4 cows in Trials 1 and 2 and the average of 6 heifers in Trial 3. However, the findings of this study do agree with those of other researchers (4,5,10,17) who observed that supplements with slower energy degradation such as soybean hulls do not substantially decrease forage digestibility or intake. Orr et al. (15) in digestion trials, also observed that DMI of bermudagrass hay and digestibility of the diets were the same when comparing soybean hull and corn supplements when fed at 0.46 and 0.61% BW, respectively. The intake equations from the NRC (14) used to formulate the diets predicted DMI of hay alone to be more than observed in the BG treatment (Fig. 1). The NRC prediction equations for DMI are based solely on the energy in the diet and do not account for rumen fill, passage rate, and other factors. There are many equations and models for predicting DMI (9,11,12), but few of them are accurate for low-quality forages, particularly warm-season perennial grasses. In addition, they do not accurately account for additive and substitutive associative effects on intake.
In this study, there was a large decline in hay DMI observed from 1.79% BW in Trial 1 to 1.23% BW in Trial 2 for cows consuming hay alone. The other treatment diets had similar declines in DMI. Since DIP was not limiting and animal characteristics and environment were similar, the quality-related characteristics of the hays likely explain this reduced DMI. Hay DM digestibility was 57.5% for Trial 1 and 52.8% for Trials 2 and 3, and NDF digestibilities were 65.1 and 53.9%, respectively (15). Intake of these hays likely is not limited by the energy demand of the animals, as NRC (14) assumes, but by physical and physiological mechanisms of intake that affect fill and passage rate (9,11,12). Further research is needed with bermudagrass hays varying in quality to quantify relationships between advancing maturity and intake of supplemented cows. Conclusions The DMI of bermudagrass hay fed free choice, without supplementation, was less than predicted by NRC (14). Supplementing with corn at approximately 0.8% of BW or soybean hulls at approximately 1.6% of BW did not substantially reduce DMI of hay as NRC (14) predicted. Instead, supplements had mostly additive effects (Fig. 1). While formulating beef cattle diets with low-quality hay, this study suggests that DMI be determined for hay alone then supplements added up to 0.8% of BW for starch-based supplements and 1.6% for soybean hulls. Supplementation above these amounts may be substitutive to DMI (8,16). Also, the substitutive effects are likely to increase as hay quality increases (7). More research is needed to determine if other supplements that have high quantities of rapidly digested fiber, such as rice bran, will respond as well as soybean hulls. Acknowledgments The authors acknowledge B. J. Rude and A. I. Orr from Mississippi State University, Department of Animal and Dairy Sciences, for their important contributions to this research. Literature Cited 1. Bodine, T. N., Purvis, H. T., II, Van Koevering, M. T., and Thomas, E. E. 1999. Effects of supplement source on intake, digestion and ruminal kinetics of steers fed prairie hay. Pages 216-221 in: Anim. Sci. Res. Rep. P-973. Oklahoma Agric. Exp. Stn., Stillwater, OK. 2. Bodine, T. N., Purvis, H. T., II, and Ackerman, C. J. 1999. Effects of supplementing prairie hay with two levels of corn and four levels of degradable intake protein. I. Intake and digestion by steers. Pages 229-234 in: Anim. Sci. Res. Rep. P-973. Oklahoma Agric. Exp. Stn., Stillwater, OK. 3. Bodine, T. N., Purvis, H. T., II, and Ackerman, C. J. 1999. Effects of supplementing prairie hay with two levels of corn and four levels of degradable intake protein. II. Ruminal parameters of steers. Pages 235-240 in: Anim. Sci. Res. Rep. P-973. Oklahoma Agric. Exp. Stn., Stillwater, OK. 4. Brown, W. F. 1990. Ammoniation or cane molasses supplementation of tropical grass hay. J. Prod. Agric. 3:377-381. 5. Brown, W. F., and Johnson, D. D. 1991. Effects of energy and protein supplementation of ammoniated tropical grass hay on the growth and carcass characteristics of cull cows. J. Anim. Sci. 69:348-357. 6. Chase, C. C., and Hibberd, C. A. 1987. Utilization of low quality native grass hay by beef cows fed increasing quantities of corn grain. J. Anim. Sci. 65:557-566. 7. Galloway, D. L., Sr., Goetsch, A. L., Forster, L. A., Jr., Patil, A. R., Sun, W., and Johnson, Z. B. 1993. Feed intake and digestibility by cattle consuming bermudagrass or orchardgrass hay supplemented with soybean hulls and(or) corn. J. Anim. Sci. 71:3087-3095. 8. Garces-Yepez, P., Kunkle, W. E., Bates, D. B., Moore, J. E., Thatcher, W. W., and Sollenberger, L. E. 1997. Effects of supplemental energy source and amount of forage intake and performance by steers and intake and diet digestibility by sheep. J. Anim. Sci. 75:1918-1925. 9. Illius, A. W., and Allen, M. S. 1994. Assessing forage quality using integrated models of intake and digestion of ruminants. p. 869-890 in: Forage Quality, Evaluation, and Utilization. G. C. Fahey, Jr., ed. ASA, CSSA, SSSA, Madison, WI. 10. Martin, S. K., and Hibberd, C. A. 1990. Intake and digestibility of low-quality native grass hay by beef cows supplemented with graded levels of soybean hulls. J. Anim Sci. 68:4319-4325. 11. Mertens, D. R. 1994. Regulation of forage intake. p. 450-493 in: Forage Quality, Evaluation, and Utilization. G. C. Fahey, Jr., ed. ASA, CSSA, SSSA, Madison, WI. 12. Minson, D. J., and Wilson, J. R. 1994. Prediction of intake as an element of forage quality. Pages 533-563 in: Forage Quality, Evaluation, and Utilization. G. C. Fahey, Jr., ed. ASA, CSSA, SSSA, Madison, WI. 13. Moore, J. E., Brant, M. H., Kunkle, W. E., and Hopkins, D. I. 1999. Effects of supplementation on voluntary forage intake, diet digestibility, and animal performance. J. Animal Sci. 77:122-136. 14. NRC. 1996. Nutrient Requirements of Beef Cattle, 7th Edn. Natn'l Acad. P., Washington, DC. 15. Orr, A. I., Nguyen, V. T., Webb, A. S., St. Louis, D. G., and Rude, B. J. 2007. Supplementing corn or soybean hulls to cattle fed bermudagrass hay I: Intake, apparent digestion, and utilization. J. Anim. Vet. Adv. 6:1343-1350. 16. Sanson, D. W., Clanton, D. C., and Rush, I. G. 1990. Intake and digestion of low-quality meadow hay by steers and performance of cows on native range when fed protein supplements containing various levels of corn. J. Anim. Sci. 68:595-603. 17. Wheeler, J. S., Lalman, D. L., Lents, C. A., and Redmon L. A. 1999. Supplemental protein requirement for beef cows grazing stockpiled bermudagrass. Pages 92-95 in: Anim. Sci. Res. Rep. P-973. Oklahoma Agric. Exp. Stn., Stillwater, OK. |
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