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Effects of energy, mineral supplementation, or both, in combination with monensin on performance of steers grazing winter wheat pasture¹

B. G. Fieser^*, G. W. Horn^*,2 and J. T. Edwards

^* Department of Animal Science, and Department of Plant and Soil Sciences, Oklahoma Agricultural Experiment Station, Stillwater 74078

	Abstract

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
A 2-yr study was conducted during the 2004 to 2005 (YR1) and 2005 to 2006 (YR2) winter wheat grazing seasons to determine the effects of supplementation strategies and delivery methods on supplement intake and growth performance of grazing steers (YR1, n = 253, initial BW 255 ± 25 kg; YR2, n = 116, initial BW 287 ± 14 kg). The 5 treatments were as follows: 1) negative control (NC), no supplemental nutrients; 2) free-choice, nonmedicated mineral (MIN); 3) free-choice, medicated mineral with 1,785 mg of monensin/kg of mineral mixture (RMIN); 4) RMIN and soybean hulls (SH-RMIN); and 5) a soybean hull-based energy supplement containing 165 mg of monensin/kg (GRNGOLD). Energy supplements were hand-fed on alternate days (average daily intake = 0.91 kg/steer). Inclusion of monensin in the free-choice mineral mixture decreased intake of the mineral mixture by 63% in YR1 and 55% in YR2 when no other supplement was offered. Consumption of RMIN provided from 129 to 161 mg of monensin/steer on average, whereas GRNGOLD provided 150 mg of monensin/d. Compared with NC, MIN did not affect ADG in YR1 (P = 0.38) but increased (P = 0.01) ADG by 0.22 kg/steer in YR2. Conversely, ADG of RMIN steers was greater (P = 0.03) than that of MIN steers during YR1 (0.72 vs. 0.55 kg/steer) but not different (P = 0.35) in YR2. Providing supplemental energy increased ADG by 0.13 kg/steer (0.85 vs. 0.72 ± 0.053) in YR1 compared with RMIN, but no increase in ADG was observed in YR2. No difference (P > 0.24) was observed in ADG between SH-RMIN and GRNGOLD in either year. Conversion of the energy supplements (kg of as-fed supplement divided by kg of additional ADG) was excellent in YR1, resulting in 1 kg of BW gain for each 3.1 kg of supplement consumed. However, due to smaller increases in ADG with the energy and monensin supplements in YR2, supplement conversion for YR2 averaged 17.6. The absence of a difference (P > 0.24) in ADG between steers that received SH-RMIN and GRNGOLD suggests that the method of delivery (separate packages vs. a single package) for energy, monensin, and mineral supplementation is not important.

Key Words: energy supplementation • mineral supplementation • monensin • wheat pasture

	INTRODUCTION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Growing cattle on winter wheat pasture is an important facet of the beef cattle industry in Oklahoma and the southern Great Plains, with as many as 6 to 7 million cattle annually grown on wheat pasture. Supplementation of stocker cattle grazing wheat pasture serves to 1) improve efficiency of production by correcting nutrient deficiencies; 2) provide feed additives such as ionophores, antibiotics, or bloat preventatives; 3) substitute for forage to increase stocking rate or extend available forage supplies; and 4) enhance cattle management (Lusby and Horn, 1991; Horn and Paisley, 1999; Horn et al., 2005). Because of the large amounts of ruminally degradable N in wheat forage and to decrease the incidence and severity of bloat, much of our previous research (Horn et al., 2005) focused on developing self-limited and hand-fed monensin-containing energy supplements for growing cattle on wheat pasture. The hand-fed supplement has been designated the Oklahoma Green Gold supplementation program, and the specifications of the supplement were reported by Horn (2006). With greater fuel and labor costs, our recent approach (Gibson, 2002) has been to deliver monensin via a free-choice mineral mixture.

The objective of this study was to compare strategies for delivering supplemental minerals, energy, and monensin concerning supplement intake and steer performance. Additionally, a new strategy for supplementation on wheat pasture, in which monensin was provided in a free-choice mineral mixture and supplemental energy was provided in the form of a commodity feedstuff (soybean hulls) was investigated.

	MATERIALS AND METHODS

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Study Site and Treatments

One hundred forty hectares of clean-tilled winter wheat at the Oklahoma State University Wheat Pasture Research Unit near Marshall, OK, was divided into 18 pastures during the winter wheat grazing seasons of 2004 to 2005 (YR1) and 2005 to 2006 (YR2). All pastures were planted to hard red winter wheat (Triticum aestivum, variety Jagalene; AgriPro, Berthoud, CO) on September 3 and 4, 2004, and September 6 and 7, 2005. Pastures were seeded at the rate of 134 kg/ha and were fertilized before planting according to soil tests. Nitrogen, P, and K were applied in amounts for production goals of 3,360 kg of forage DM/ha and a 3,360 kg/ha wheat grain crop. The five treatments were as follows: 1) negative control (NC), no mineral or any other supplement; 2) free-choice, nonmedicated mineral (MIN); 3) free-choice, medicated mineral containing 1,785 mg of monensin/kg (RMIN); 4) RMIN and soybean hulls (SH-RMIN); and 5) a monensin-containing energy supplement formulated to the Oklahoma Green Gold supplement specifications containing 165 mg of monensin/ kg (GRNGOLD; Horn et al., 2005, 2006). Mineral mixtures in YR1 and YR2 (both MIN and RMIN) were manufactured by ADM Alliance Nutrition Inc., Quincy, IL, and North American Nutrition Companies Inc., Lewisburg, OH, respectively. Energy supplements were hand-fed at the rate of 1.81 kg/steer every other day to achieve a target average daily intake of 0.91 kg/steer. Both supplements were fed pelleted (0.5-cm pellet).

Each year, the pastures were blocked by location within the wheat field (4 blocks), and treatments were randomly assigned within block with the restriction that no treatments were in adjacent pastures. One block had only 3 pastures, and the RMIN, SH-RMIN, and GRNGOLD treatments were randomly assigned within that block. Steer BW gain was measured from November 5, 2004, to February 4, 2005 (91 d), and from November 15, 2005, to March 8, 2006, (113 d). During the YR1 grazing season, steers continued grazing until February 22, 2005, when the wheat reached the first-hollow stem stage of maturity, as is recommended in a dual-purpose winter wheat system (Redmon et al., 1996; Fieser et al., 2006a). However, due to low forage availability (the result of cumulative effects of wet weather and trampling of wheat by steers), steer growth performance after February 4, 2005, was not used in BW gain analysis in the YR1 data set.

Cattle

The Oklahoma State University Institutional Animal Care and Use Committee approved the use of animals and research procedures used in this study.

YR1. Two hundred fifty-three predominantly black, crossbred steers (initial BW 255 ± 25 kg) that originated from a single ranch in north central Nebraska (Ainsworth) grazed winter wheat pastures in YR1. All steers were shipped directly from the ranch of origin and had not been previously comingled with cattle of any other source. Within 24 h of arrival, all steers were weighed and vaccinated for infectious bovine rhinotracheitis, bovine virus diarrhea, parainfluenza 3, bovine respiratory syncytial virus (Titanium 5, Agri Laboratories Ltd., St. Joeseph, MO), as well as treated with an injectable dewormer (Ivomec, Merial Ltd., Duluth, GA). From arrival until turnout on wheat pasture, all steers were held in a drylot and fed Bermudagrass hay and a 40% CP, Deccox (Alpharma Inc., Fort Lee, NJ) containing supplement at the daily rate of 0.91 kg/steer. Steers were stratified by arrival BW and allotted to pastures to minimize differences in BW between pastures at the initiation of the experiment. All steers were weighed and implanted with Component E-S with Tylan (Vet-Life, West Des Moines, IA) on the day they were placed on wheat pasture (November 5, 2004). To minimize risk of bloat at turnout, the initial BW was taken when steers were full, and a 2% pencil shrink was used to determine initial BW. Subsequent BW measures were taken following an overnight withholding of feed and water on February 4 and 22, 2005. Eighteen steers (1 steer/pasture) were added on December 2, 2004, but were not included in BW gain determination. These additional steers were added to utilize the excess forage available before turn-out and during the early part of the grazing season, in accordance with forage clipping data (i.e., adjustments in stocking densities were made to maintain similar forage allowances for all pastures within a block). The weighted average stocking density for all pastures over the course of the 91-d experimental grazing period during YR1 was 1.74 steers/ha.

YR2. One hundred sixteen predominantly black, crossbred steers (initial BW = 287 ± 14 kg) that originated from a single ranch in northeast Colorado (Yuma) grazed winter wheat pastures in YR2. The cattle shipping, feeding, and vaccination protocol was the same as described previously for YR1. Steers were weighed full and implanted with Component E-S with Tylan (VetLife) at turnout (November 15, 2005). Initial BW was calculated with a 2% pencil shrink as described previously. Subsequent BW measures were taken on December 22, 2005, and February 10 and March 8, 2006, following an overnight withholding of feed and water. Originally, 155 steers were turned out on November 15, 2005, but 33 steers (approximately 2 steers/ pasture) were removed on December 22, 2005, based on declining forage availability. Additionally, on February 10, 2006, two steers were removed from pastures 1, 9, and 18 based on clipping data indicating lower forage availability in these pastures than other pastures within their block. The weighted average stocking density for all pastures during the 113-d experimental grazing period of YR2 was 0.94 steers/ha.

Sample Collection and Preparation

Wheat forage mass was determined by hand-clipping forage to ground level inside 0.19-m² quadrants (10 random locations within each pasture). Clipping was done on 4 dates within each grazing season: October 28 and December 15, 2004, and January 25 and February 22, 2005, for YR1 and November 10 and December 14, 2005, and January 24 and March 7, 2006, for YR2. At collection, care was taken to ensure minimal soil contamination of the forage samples. Clipped samples were dried to a constant weight in a forced-air oven at 50°C and weighed for DM determination. Forage mass was calculated by taking the grams of DM per 0.19 m² from the clipped sample and extrapolating that to kilograms of DM on a per-hectare basis in each pasture. Forage allowance was calculated as kilograms of DM/ steer and kilograms of DM/100 kg of BW. This was determined using the number and BW of steers in each pasture on the date of clipping or weigh date in closest proximity to the clipping date. The November 10, 2005, and March 7, 2006, forage samples were retained for characterization of forage quality. Forage samples were composited by pasture within clipping date. During each year, energy supplements and mineral mixtures were sampled weekly. All supplement and mineral mixture samples were composited monthy within each year and analyzed for monensin concentration at a commercial laboratory (Eurofins Scientific, Memphis, TN). At the end of each year, supplement samples were composited. Composited forage and supplement samples were ground to pass through a 2-mm screen in a Wiley mill (Thomas Scientific, Philidelphia, PA) for determination of DM, OM, CP, NDF, ADF, ether extract, neutral detergent insoluble CP, and acid detergent insoluble CP (AD-ICP), as well as macro- and microminerals. Total digestible nutrient value was determined according to the equations of Weiss et al. (1992).

Laboratory Analyses

Dry matter and ash content were determined by oven-drying at 100°C for 24 h, followed by ashing at 500°C for 6 h in a muffle furnace. A combustion method (Leco CN-2000, St. Joseph, MI) was used in accordance with AOAC (1996) to determine N content. Forage and supplement NDF, ADF, and ADL concentrations were determined sequentially, as described by Van Soest et al. (1991), without the addition of sodium sulfite, using an Ankom200 Fiber Analyzer and F57 filter bags (Ankom Technology, Macedon, NY). Neutral detergent insoluble CP and ADICP were determined by performing nonsequential NDF and ADF procedures and removing the residue from the filter bags and determining N concentration of the residue by the combustion method described above. Ether extract concentration was determined at a commercial laboratory (SDK Laboratories, Hutchinson, KS). Mineral content (Ca, P, Mg, K, S, Na, Zn, Fe, Mn, and Cu) of wheat forage, supplements, and mineral mixtures was also determined at a commercial laboratory (Servi-Tech Laboratories, Dodge City, KS).

Supplements and Mineral Mixtures

Ingredient and nutrient composition of the energy supplements (soybean hulls and GRNGOLD) are shown in Table 1. Rumensin 80 (Elanco Animal Health, Indianapolis, IN) was added to the GRNGOLD supplement to result in a target monensin concentration of 165 mg of monensin/kg of supplement on an as-fed basis. Actual analyzed concentration of monensin in the GRNGOLD supplement was 155 ± 4 mg of monensin/kg on an as-fed basis for YR1 and 150 ± 12 mg of monensin/kg in YR2. Formulated monensin concentration of RMIN was 1,785 mg of monensin/kg of mineral mixture (as-fed). Actual analyzed concentrations were 1,914 ± 225 and 1,680 ± 117 mg of monensin/kg of mineral mixture (as-fed) for YR1 and YR2, respectively. Because the analyzed monensin concentrations were considered to be within the analytical error for monensin determination, the formulated monensin concentrations from RMIN and GRNGOLD were used to calculate monensin intake for the RMIN, SH-RMIN, and GRNGOLD treatments.

Individual steer growth performance measures were averaged by pasture (pasture = experimental unit) and analyzed as a randomized complete block design using the MIXED procedure (SAS Inst. Inc., Cary, NC), with pasture location within the field used as the blocking factor. The model included the main effect of treatment and used the Satterthwaite procedure to determine degrees of freedom. Due to the different environmental conditions between YR1 and YR2, each year was analyzed independently using the following nonorthogonal contrast statements: 1) NC vs. MIN, 2) MIN vs. RMIN, 3) RMIN vs. average of SH-RMIN and GRNGOLD, and 4) SH-RMIN vs. GRNGOLD. Average daily gain least squares means were adjusted using a covariate (P < 0.01) of forage allowance on February 4, 2005, in YR1 (forage allowance at end of BW gain measures). Ending forage allowance was considered as a covariate during YR2 but was not used (P = 0.44). Forage allowance measures, nutrient concentrations, and supplement and mineral intakes are presented as means and SD without further statistical analysis.

	RESULTS AND DISCUSSION

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 
Forage Availability and Quality

Temperature and rainfall data for the 2 yr of this study, as well as normal temperatures and precipitation, are shown in Table 3. Monthly average temperature in each of the 2 yr was generally at or above the normal monthly average temperature. These 2 yr were drastically different concerning total precipitation. The first year was characterized by excessively wet conditions early in the growing season, whereas YR2 was one of the most significant drought seasons in Oklahoma history, with only 18 mm of precipitation from November through the end of February (most of the duration of the grazing season). In YR1, August, October, and November were particularly wet, with at least 100 mm of total precipitation in each month. However, the next 4 mo (remainder of grazing season) received only 129 mm of total precipitation.

Mineral Mixture and Supplement Intake

Intake of MIN is shown in Figure 1. Average daily intake of MIN was 193 g/steer during YR1 and 183 g/ steer in YR2. During the last 4 wk of the YR1 grazing season, MIN was hand-fed daily at the rate of 181 g/ steer. This was done to control increasing levels of MIN consumption, which had been increasing throughout the grazing season and topped 300 g·steer^–1·d^–1 the previous week (wk 9). During YR2, steers had continuous access to MIN for the duration of the grazing season. In both years, MIN intake increased steadily from turn-out until about 8 to 10 wk into the grazing season. Daily mineral mixture intake greater than 180 g/steer is likely more than economically feasible in production settings. Although intake of MIN was high, it is less than the 2-yr average daily intake of 227 g/steer reported by Gibson (2002) for a nonmedicated, free-choice mineral mixture. High MIN intake in our studies may be due to the location of the mineral feeder near the only water source in each pasture, as well as near a windbreak where steers spent time loafing. Additionally, pasture size ranged from 7.3 to 9.7 ha, so steers were in much closer proximity to mineral feeders than they might be in more extensive production environments.

View larger version (11K): [in this window] [in a new window]   Figure 1. Average daily intake (mean ± SD) of free-choice, nonmedicated mineral mixture (MIN) as measured weekly during the 2004 to 2005 (YR1) and 2005 to 2006 (YR2) winter wheat grazing seasons.

View larger version (13K): [in this window] [in a new window]   Figure 2. Average daily intake (mean ± SD) of free-choice, monensin-containing mineral mixture (RMIN; 1,785 mg of monensin/kg) as measured weekly during the 2004 to 2005 (YR1) and 2005 to 2006 (YR2) winter wheat grazing seasons.

View larger version (15K): [in this window] [in a new window]   Figure 3. Average daily intake (mean ± SD) of free-choice, monensin-containing mineral mixture (RMIN; 1,785 mg of monensin/kg) when offered in conjunction with 1.81 kg of soybean hulls, as fed every other day during the 2004 to 2005 (YR1) and 2005 to 2006 (YR2) winter wheat grazing seasons.

Steer Performance

Growth performance of steers is shown in Table 6. Initial BW of the steers was relatively large, and ADG during YR1 was substantially less than the 1.0 kg commonly observed for steers fed MIN at the Oklahoma State University Wheat Pasture Research Unit (Kaitibie et al., 2003). Treatment influenced ADG (P < 0.01) in both years. In YR1, MIN did not increase ADG (P = 0.38) as compared with the NC but did increase ADG (P = 0.01) by 0.22 kg in YR2. The increased ADG by MIN in YR2 is possibly due to correction of a slight mineral deficiency in wheat pasture as previously discussed. Because of the lower ADG in YR1, wheat forage alone may have adequately met the mineral requirements without MIN for the observed level of performance. A 2-yr wheat pasture study reported by Gibson (2002) also included the NC, MIN, and RMIN treatments. If data of that study are included with this study (i.e., combined 4-yr data set), MIN increased ADG (P < 0.01) of steers grazing wheat pasture from 0.71 to 0.82 kg (G. W. Horn; C. P. Gibson, Oklahoma State University, Stillwater; and B. G. Fieser, unpublished data).

Daily gains were increased (P = 0.05) by providing supplemental energy in addition to the monensin-containing mineral mixture (i.e., contrast of RMIN vs. SH-RMIN and GRNGOLD) in YR1; however, this contrast was not significant (P = 0.87) in YR2. An explanation for the lack of response to the additional energy as soybean hulls or GRNGOLD, which was predominantly soybean hulls, in YR2 could be an actual dilution of overall dietary energy intake due to supplementation. Because the calculated TDN value of the supplements was less than the calculated TDN of wheat forage (62.4, 57.8, and 64.9% average TDN for soybean hulls, GRNGOLD, and wheat forage, respectively), the supplements may have decreased overall dietary energy intake. However, the TDN of by-product feeds like soybean hulls is highly variable and often underestimated. Additionally, our calculated TDN for wheat forage is lower than other digestibility estimates for wheat forage (Reuter and Horn, 2000). Lippke et al. (2000) found that supplementing steers on wheat pasture with cottonseed hulls and cottonseed hulls plus corn decreased OM digestibility and did not increase OM intake. Cravey et al. (1992) reported substitution ratios for wheat pasture averaged 0.86 for high-starch and high-fiber monensin-containing energy supplements (i.e., each kg of supplement decreased forage DMI by 0.86 kg). In the studies conducted by Cravey et al. (1992), forage allowances were low and averaged 104 kg of DM/100 kg of BW. Fieser and Vanzant (2004) reported a substitution ratio of 0.61 for either cracked corn or soybean hulls for growing steers fed vegetative fescue hay (17.4% CP). The lack of a difference (P > 0.24) in ADG between steers that received SH-RMIN and GRNGOLD suggests that the method of delivery (separate packages vs. a single package) for energy, monensin, and mineral supplementation is unimportant.

Although not included in our contrasts, the GRNGOLD supplement increased ADG by 0.34 kg in YR1, as compared with MIN, but a similar response was not observed in YR2. In 3 of 4 studies reported by Horn et al. (2005), the monensin-containing energy supplements very consistently increased ADG of growing cattle on wheat pasture by about 0.18 kg as compared with MIN. Rouquette et al. (1982) reported that a monensin-containing ground corn supplement (220 mg of monensin/kg) fed at 0.91 kg/d to growing cattle on rye and ryegrass pastures increased ADG by 0.21 kg as compared with MIN. In our studies that lead to the GRNGOLD supplementation program, the energy supplements consisted of about 65% ground sorghum grain and 21% wheat middlings. A combination of energy feedstuffs may provide a more favorable synchrony concerning rates of ruminal starch, OM fermentation, or both, and the CP fractions of wheat forage. This may result in a more consistent BW gain response to supplementation as compared with a high-fiber commodity feedstuff like soybean hulls. Horn et al. (1995) supplemented growing cattle on wheat pasture with high-starch (79% ground corn) or high-fiber (47% soybean hulls and 42% wheat middlings) energy supplements, and type of supplement did not influence (P > 0.45) ADG. However, mean daily supplement consumption was 0.65% BW, which is much greater than the targeted intake for GRNGOLD.

Supplement Conversion

Supplement conversion (expressed as kg of as-fed supplement divided by kg of additional ADG compared with MIN) is shown in Table 6. Supplement conversions were excellent in YR1 and were 3.5 and 2.7 for SH-RMIN and GRNGOLD, respectively. Because of the much smaller ADG response to the energy supplements in YR2, these conversions were much greater. In previous work, conversions for the GRNGOLD supplement, containing about 65% ground sorghum grain and 21% wheat middlings and fed at the same rate as the current study, have been much more consistent and ranged from 4.4 to 5.2 (Horn et al., 2005). At similar supplement intakes to this study, calculated supplement conversions of 3.9 and 4.9, respectively, for 141 and 170 d grazing were observed by Rouquette et al. (1982). A modification of the GRNGOLD supplement in which the amount fed was cut in half (i.e., 0.91 kg every other day vs. 1.82 kg every other day, and monensin intake was similar to the current study) resulted in supplement conversion of 3.6 (Fieser et al., 2003). However, rate of consumption of the supplement was slowed, which would be of concern on days of inclement weather. Fieser et al. (2005) found that increasing daily monensin intake from 100 to 188 mg (target of 200) improved supplement conversion from 5.2 to 3.9. In 1 yr of the study reported by Horn et al. (1981), addition of 110 mg/kg of monensin to an energy supplement fed at a daily rate of 0.91 kg/head to light-BW heifers grazing wheat pasture decreased supplement conversion from 9.8 to 4.3. Additional data are needed relative to the effect of forage mass, allowance, or both on conversion of energy supplements fed to growing cattle on wheat pasture. However, in general, the data indicate that supplement conversion is improved as the amount of supplement fed is decreased and that the effect of monensin on supplement conversion is important in evaluating the economics of supplementation programs.

Delivery of efficacious amounts of technologies such as ionophores, antibiotics, and bloat-preventive compounds is a very real and important challenge in beef cattle grazing programs. Inherent with this challenge is development of specific supplementation programs that include amount and type of supplement to be fed. In this study, inclusion of monensin in a free-choice mineral mixture decreased intake of the mineral mixture by about 60%. Daily BW gain of RMIN steers was greater (P < 0.05) than MIN in YR1 (0.72 vs. 0.55 ± 0.053 kg/steer) but was not different (P = 0.35) in YR2. Three different delivery methods that included a free-choice monensin-containing mineral mixture, the same free-choice monensin-containing mineral mixture plus hand-fed soybean hulls (SH-RMIN), and a hand-fed monensin-containing, soybean hull-based energy supplement (GRNGOLD) resulted in monensin intakes of about 146 mg/d with very small differences for monensin intake among delivery methods. The absence of a difference (P > 0.24) in daily gain between steers that received SH-RMIN and GRNGOLD suggests that the method of delivery (separate packages vs. a single package) for energy, monensin, and mineral supplementation is not important. Relative cost of products, location, and accessibility of pastures, fuel costs, and opportunity cost for labor all influence decisions relative to method of delivery of technologies in grazing programs.

	Footnotes

 
¹ This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, USDA, under agreement no. 2003-34198-13358. We express our appreciation to Jim Kountz (Department of Animal Science), for his expert assistance in cattle management and data collection. We also appreciate the assistance of Richard Austin (Department of Plant and Soil Sciences) for forage sampling and data collection and to Mark Payton and Carla Goad (Department of Statistics) for statistical consultation.

² Corresponding author: gerald.horn{at}okstate.edu

Received for publication February 28, 2007. Accepted for publication August 11, 2007.

	LITERATURE CITED

Top Abstract INTRODUCTION MATERIALS AND METHODS RESULTS AND DISCUSSION LITERATURE CITED

 


AOAC. 1996. Official Methods of Analysis. 16th ed. Assoc. Off. Anal. Chem., Arlington, VA.

Beck, P. A. 1993. Development of a self-limited monensin-containing energy supplement for growing cattle on wheat pasture. MS Thesis. Oklahoma State Univ., Stillwater.

Brazle, F. K., and S. B. Laudert. 1998. Effect of feeding Rumensin in a mineral mixture on steers grazing native grass pastures. Pages 123–125 in 1998 Kansas State Cattlemen’s Day Proc. http://www.oznet.ksu.edu/library/lvstk2/srp804.pdf Accessed Oct. 31, 2006.

Cravey, M. D., G. W. Horn, F. T. McCollum, and P. A. Beck. 1992. Effect of high-starch vs. high-fiber energy supplements on forage intake of steers grazing wheat pasture. J. Anim. Sci. 70(Suppl. 1):89. (Abstr.)[Abstract]

Fieser, B. G., G. W. Horn, J. T. Edwards, and E. G. Krenzer Jr. 2006a. Timing of grazing termination in dual-purpose winter wheat enterprises. Prof. Anim. Sci. 22:210–216.[Abstract/Free Full Text]

Fieser, B. G., G. W. Horn, and J. R. Kountz. 2005. Effect of increasing levels of monensin in an energy supplement for cattle grazing winter wheat pasture. http://www.ansi.okstate.edu/research/2005rr/2005rr/18/18.htm Accessed Oct. 31, 2006.

Fieser, B. G., G. W. Horn, J. R. Kountz, and S. A. Schaefer. 2003. A modification of the Oklahoma Green Gold Supplementation Program: Supplement intake and performance of wheat pasture stocker cattle. http://www.ansi.okstate.edu/research/2003rr/01/01.htm Accessed Oct. 31, 2006.

Fieser, B. G., G. W. Horn, and E. G. Krenzer Jr. 2006b. Effects of planting date and forage allowance on steer growth performance and grain yield in a dual-purpose winter wheat system. Prof. Anim. Sci. 22:424–431.[Abstract/Free Full Text]

Fieser, B. G., and E. S. Vanzant. 2004. Interactions between supplement energy source and tall fescue hay maturity on forage utilization by beef steers. J. Anim. Sci. 82:307–318.[Abstract/Free Full Text]

Gibson, C. P. 2002. Mineral supplementation with or without ionophores and phosphorus accretion in growing beef cattle grazing winter wheat pasture. MS Thesis. Oklahoma State Univ., Stillwater.

Horn, F. P. 1984. Chemical composition of wheat pasture. Pages 47–54 in Natl. Wheat Pasture Symp. Proc. G. W. Horn, ed. Oklahoma Agric. Exp. Stn., Stillwater.

Horn, G. W. 2006. Growing cattle on winter wheat pasture: Management and herd health considerations. Vet. Clin. Food Anim. 22:335–356.[CrossRef]

Horn, G. W., P. A. Beck, J. G. Andrae, and S. I. Paisley. 2005. Designing supplements for stocker cattle grazing wheat pasture. J. Anim. Sci. 83:E69–E78.[Abstract/Free Full Text]

Horn, G. W., M. D. Cravey, F. T. McCollum, C. A. Strasia, E. G. Krenzer Jr., and P. L. Claypool. 1995. Influence of high-starch vs. high-fiber energy supplements on performance of stocker cattle grazing wheat pasture and subsequent feedlot performance. J. Anim. Sci. 73:45–54.[Abstract]

Horn, G. W., T. L. Mader, S. L. Armbruster, and R. R. Frahm. 1981. Effect of monensin on ruminal fermentation, forage intake, and weight gains of wheat pasture stocker cattle. J. Anim. Sci. 52:447–454.[Abstract/Free Full Text]

Horn, G. W., and S. I. Paisley. 1999. Developments in the management and supplementation of stocker cattle on wheat pasture. Pages 48–54 in Proc. 1999 Plains Nutr. Counc. Spring Conf., San Antonio, TX. Texas A&M Res. Ext. Center, Amarillo.

Kaitibie, S., F. M. Epplin, G. W. Horn, E. G. Krenzer Jr., and S. I. Paisley. 2003. Dual-purpose winter wheat and stocker steer grazing experiments at the wheat pasture research unit, Marshall, Oklahoma. Bulletin B-816. Oklahoma Agric. Exp. Stn., Stillwater.

Large, E. C. 1954. Growth stages in cereals. Illustration of the Feekes scale. Plant Pathol. 3:128–129.[CrossRef]

Lippke, H., T. D. A. Forbes, and W. C. Ellis. 2000. Effect of supplements on growth and forage intake by stocker steers grazing wheat pasture. J. Anim. Sci. 78:1625–1635.[Abstract/Free Full Text]

Lusby, K. S., and G. W. Horn. 1991. Supplementation programs for high-intensity grazing systems and high-quality forages. A. Review. Prof. Anim. Sci. 7:43–48.

Moore, J. E., M. H. Brant, W. E. Kunkle, and D. I. Hopkins. 1999. Effects of supplementation on voluntary forage intake, diet digestibility, and animal performance. J. Anim. Sci. 77(Suppl. 2):122–135.[Abstract/Free Full Text]

Morrison, I. M. 1980. Changes in the lignin and hemicellulose concentrations of ten varieties of temperate grasses with increasing maturity. Grass Forage Sci. 35:287–293.[CrossRef]

NRC. 1996. Nutrient Requirements of Beef Cattle. 7th ed. Natl. Acad. Press, Washington, DC.

NRC. 2001. Nutrient Requirements of Dairy Cattle. 7th ed. Natl. Acad. Press, Washington, DC.

Redmon, L. A., E. G. Krenzer Jr., D. J. Bernardo, and G. W. Horn. 1996. Effect of wheat morphological stage at grazing termination on economic return. Agron. J. 88:94–97.[Abstract/Free Full Text]

Reuter, R. R., and G. W. Horn. 2000. Changes in growth performance of steers and nutritive value of wheat pasture from fall/winter grazing to graze-out. http://www.ansi.okstate.edu/research/2000rr/05.htm Accessed Oct. 25, 2006.

Rouquette, F. M., Jr., J. V. Davis, and M. J. Florence. 1982. Influence of monensin on gain of stocker calves grazing cool-season annual grasses. Pages 5–13 in Forage Research in Texas. Texas Agric. Exp. Stn., College Station.

Stewart, B. A., D. L. Grunes, A. C. Mathers, and F. P. Horn. 1981. Chemical composition of winter wheat forage grown where grass tetany and bloat occur. Agron. J. 73:337–347.[Abstract/Free Full Text]

Van Soest, P. J., J. B. Robertson, and B. A. Lewis. 1991. Methods for dietary fiber, neutral detergent fiber, and non-starch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74:3583–3597.[Abstract]

Weiss, W. P., H. R. Conrad, and N. R. St. Pierre. 1992. A theoretically-based model for predicting total digestible nutrient values of forages and concentrates. Anim. Feed Sci. Technol. 39:95–110.[CrossRef]

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