Restricting Intake of Forages: An

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1 The rofessional Animal Scientist 21 (2005): Restricting Intake of Forages: An Alternative Feeding Strategy for Wintering Beef Cows T. C. CUNNINGHAM, D. B. FAULKNER 1,AS,A.J.MILLER,andJ.M.DAHLQUIST Department of Animal Science, University of Illinois, Urbana Abstract In Experiment 1, 72 Simmental cows with calves were used to evaluate restricting time of access to high quality hay stored inside. Four replications were used to evaluate three treatments relative to access to hay: restricted to 4, 8, or 24 h/d. Final cow BW (=0.06) tended to be heavier as hay access times increased. Calf performance did not differ. Manure production (kg DM/d per head) increased (=0.002) with increasing access to hay. Nitrogen disappearance (kg/d per head) increased linearly (=0.01) and quadratically (=0.02) with increasing access to hay. In Experiment 2, 72 Simmental cows in the third trimester of gestation were used to evaluate four treatments: ground hay (7.6-cm screen) fed to meet 90% of NRC (1996) recommendations for maintenance and access to hay restricted to 3, 5, or 7 h/d. Cows on all treatments in this experiment were fed average quality hay that was stored outside. Cow BW change increased linearly (=0.04) with increasing time allowances. Manure production (kg DM/d per head) tended to increase linearly (= 0.08) as access time increased. In Experiment 3, 108 Simmental cows with calves were used to evaluate three feeding levels of ground hay: [100, 90, or 80% 1 To whom correspondence should be addressed: danb@uiuc.edu of NRC (1996) requirements for maintenance]. No differences in cow performance, calf BW gain, or manure production were observed. Amounts of N (= 0.11) and (=0.09) in the manure (kg/ d per head) tended to be reduced with restricted intake. These results indicate that restricting intake of at least average quality forages results in a desirable level of cow performance and reduces hay waste, manure production, and manure nutrient output. (Key Words: Restricted Intake, Forages, Hay, Beef Cows.) Introduction Reducing winter feed costs for beef cows is important to cow-calf producers throughout the US. According to Standardized erformance Analysis records (Miller et al., 2001), feed costs account for >60% of beef producers annual cow costs, with over one-half of these costs attributed to winter feed expenditures. Wintering beef cows utilizing large round bales of hay is a common practice for many cow-calf operations. However, there are several economic concerns with feeding large round bales of hay for ad libitum intake. These include hay waste, overconsumption, and costs of production and storage. Finding alternative methods of feeding hay has become the focus of current cow-calf production research. Limit-feeding of high concentrate feedstuffs and other least-cost diets have been well researched and established as viable alternatives to feeding hay for ad libitum intake (Loerch, 1996; Schoonmaker et al., 2003). Extensive work evaluating limit-fed, high concentrate diets has shown improvements in feed efficiency and depressed ADG for growing cattle in the feedlot (Hicks et al., 1987; Loerch, 1990). These findings led to further investigation of the effect limit-feeding has upon DM digestibility. Work by Murphy et al. (1994) with growing lambs and by Loerch (1990) with steers showed that limit-fed, high concentrate diets improved DM digestibility. This may partially explain the increases observed in feed efficiency. More recently, Loerch (1996) reported limit-feeding high concentrate diets to beef cows has resulted in similar performance when compared with cows fed hay for ad libitum intake. Many producers still rely upon hay as their main feedstuff for wintering cows. Therefore, the goals of this research involved identifying feeding systems using hay as the primary feedstuff for wintering beef cows. Research to evaluate the effects of restricting intake of forages for wintering beef cows is limited. The research presented herein evaluates restricting forage intake by limiting time of access or restricting intake of forage based diets. These alternative

2 Restricting Intake of Forages 183 forage-feeding strategies reduce hay waste, manure output, and cow costs, while maintaining acceptable cow performance. Materials and Methods All experiments were conducted at the Orr Beef Research Center, Baylis, Illinois. While on the study, all cows were kept in dry lot pens with southfacing, open-fronted ( m) shelters. Overall pen dimensions were m. en surfaces were concrete, which allowed pen cleanings with little contamination. All manure was collected, sampled, and weighed from the pens to establish manure production. All cows were removed from feed and water for 16 h prior to taking initial and final BW. A common diet was fed to all cows 5 d before taking final BW to minimize fill differences. Access to shelter and water were available at all times during the trial period. Each pen was equipped with round bale feeders, which were gated to allow access as desired. This allowed cows to have access to hay for their given time allotments and prevented consumption the remainder of the time. Round bale feeders were 3.7 m in length and allowed adequate feeding space for six head per pen (0.6 m per head). Additionally, pens were equipped with fenceline bunks (7.3 m in length) that had adequate bunk space for 12 head (0.6 m per head). All ground hay was processed in a tub grinder and was ground to pass a 7.6- cm screen. All samples of manure collected from pens were analyzed for DM and nutrient output (Iowa Testing Laboratories, Inc., Eagle Grove). Experimental procedures were approved by the Laboratory Animal Care Advisory Committee, University of Illinois at Urbana-Champaign. Experiment 1. Seventy-two Simmental cows (616.7 ± 28.3 kg) with calves were used to compare the effects of 24-h access to round bales of hay vs access restricted to 4 h and access restricted to 8 h. Twelve pens were used, which resulted in six cows TABLE 1. Hay analysis (DM basis) for Experiments 1 through 3. Item Experiment 1 Experiment 2 Experiment 3 C, % ADF, % NDF, % TDN, % a NE l, Mcal/kg a NE g, Mcal/kg a NE m, Mcal/kg a RFV b Ca, % , % Mg, % K, % S, % a Calculated values from near infrared spectroscopy results. b RFV = relative feed value. per pen with four replications. Hay utilized in this study was high quality (legume and grass mix) round bales of hay that were stored inside (Table 1). Hay samples were analyzed by wet chemical methods by the Rock River Laboratory (Watertown, WI). Each bale was weighed prior to being fed, and individual bale core samples were collected (sample depth = 30 cm) and composited for DM and nutrient analysis (Rock River Laboratory). Orts were collected, weighed, and sampled for DM analysis. Cows and calves were randomly allotted to treatment within 24 h after parturition. Initial cow BW and body condition scores (BCS) were taken prior to allotment, and calf birth BW were used as initial calf BW. Milk production estimates were determined by the 12-h weighsuckle-weigh technique on all cows on d 62 of the trial. Chromium oxide was fed to three of the four replications at a rate of 10 g/d per head along with 0.9 kg of cracked corn used as a carrier. Chromium oxide was fed for a 10-d period beginning on d 52 of the trial. The other replication in this experiment received individual chromium oxide bolus capsules containing 10 g/d. Chromium oxide was bolused to this one replication to develop a correction factor for chromium recovery. On d 10 of the chromium oxide feeding period, individual fecal grab samples were collected from all cows and composited by pen at 8-h intervals over a 24-h period for laboratory analysis and the determination of fecal output. ens were cleaned on d 42 of the study and at the conclusion of the study. All manure was weighed and analyzed for N,, and K concentrations (Iowa Testing Laboratories, Inc.). Experiment 2. Seventy-two Simmental cows (593 ± 18.6 kg) in the third trimester of gestation were used to compare four treatments: ground hay fed at 90% NRC requirements (1996) (balanced for energy and protein) for maintenance (7.5 kg/d per head) and access to round bales of hay restricted to 3, 5, or 7 h/d. Experiment 2 was conducted in the fall of 2001 and utilized average quality hay (analyzed by near infrared spectroscopy; Iowa Testing Laboratories, Inc.) (Table 1) stored outside for all treatments. Duration of the trial was 91 d. Hay feeding procedures were conducted as outlined in Exp. 1. Cows were blocked by BW and assigned to 12 pens, resulting in six cows per pen and three pens per treatment. Initial and final BCS were taken. Manure

3 184 Cunningham et al. samples were collected for DM and N,, and K analysis (Iowa Testing Laboratories, Inc.). Chromium oxide was fed at a rate of 10 g/d per head for a 10-d period. On d 10 of the chromium oxide feeding period, individual fecal grab samples were collected and composited by pen every 8 h over a 24-h period. Fecal output was determined using the chromium marker. Experiment 3. Experiment 3 was conducted in the spring of 2002 utilizing average quality hay stored outside (analyzed by near infrared spectroscopy; Iowa Testing Laboratories, Inc.) (Table 1) to evaluate how limit-fed ground forages affect cow-calf performance, manure production, and nutrient output. One-hundred eight Simmental cows (614 ± 30.0 kg) with calves were used in four replications to evaluate three treatments: limit-fed ground hay fed at 100% NRC (1996) requirement (14 kg DM/d per head), limit-fed ground hay at 90% NRC (12.7 kg DM/d per head), and limitfed ground hay at 80% NRC (11.2 kg DM/d per head). Diets were fed once daily and supplemented with 200 mg of Rumensin (Elanco Animal Health, Indianapolis, IN) along with 0.9 kg of cracked corn and 0.11 kg of mineral as a carrier during the 75-d trial. Cows were adjusted to treatment, which was increased gradually until hay allotments were completely consumed. Cows were fed in fenceline bunks (7.3 m per 0.6 m per head) in each pen that had bunk space for 10 head. All cows had access to shelter and water at all times. Cows were fed 10 mg of chromium oxide for a 10-d period, and individual fecal grab samples were collected and composited by pen every 8 h for a 24-h period on d 10. Allotment and initial and final measurement procedures were conducted the same as in Experiment 1. Statistical Analysis. Effects of dietary treatment on cow-calf performance, manure production and fecal output, hay waste, and manure nutrient output (Experiments 1 through 3) were analyzed using the GLM proce- TABLE 2. Effects of feeding round bales of hay for time restrictions of 4, 8, or 24 h on cow and calf performance and milk production (Experiment 1). Item 4 h 8 h 24 h SE Linear Quadratic Initial BW, kg Initial BCS a Final BW, kg Final BCS a BW Change, kg BCS Change Initial calf BW, kg b Final calf BW, kg Calf ADG, kg/d Milk production, kg c a BCS = body condition score (1- to 9-point scale). b Calf birth BW was used as calf initial BW. c Milk production estimate was obtained using 12-h weigh-suckle-weigh technique. dure of SAS (SAS Inst. Inc., Cary, NC) for a completely random design, with pen as the experimental unit. Linear and quadratic contrasts were used for analyzing time allotments (Experiments 1 and 2) and/or feeding level (Experiment 3). Contrast coefficients were developed for unequal treatment spacing using SAS for orthogonal polynomial contrasts. For Experiment 2, 3-, 5- and 7-h time allowances were analyzed for linear and quadratic effects, and a separate comparison was made for the 5-h access vs the 90% NRC (1996) ground hay treatment. Results and Discussion Experiment 1. Initial cow BW and BCS did not differ (>0.10) for the three treatments (Table 2). Final cow BW and cow BW change were greater (=0.06 and =0.08, respectively) as time of access increased. Cows on the 4-h treatment lost an average of 37 kg more BW than did cows on the 24-h treatment. Improvements for final BCS (=0.04) and BCS change (= 0.01) were observed with increasing time allowed for consumption. On average, cows on the 24-h treatment finished the trial with an advantage of nearly 0.8 in BCS compared with cows on the 4-h treatment. Loerch (1996) observed no differences in performance when cows received either ad libitum hay or were limit-fed corn during gestation and postpartum. However, diets used by Loerch (1996) were designed to provide similar energy intake across treatments. This study observed decreased performance caused by decreasing levels of energy intake with increased time restriction. These losses in BW and BCS were acceptable for the lactating cows in this study. Average pen final BCS (5.6 ± 0.48) ranged from 4.9 to 6.4 across all treatments for individual cows. This is acceptable body condition for breeding. Calf performance was not affected by time of access to hay. Final calf BW and calf ADG were similar across treatments (=0.72 and =0.77 respectively). Similarly, milk production was not affected by dietary treatment. These findings suggest that although cow performance was reduced for cows on the 4-h and 8-h treatments, subsequent calf performance was not altered. Hay disappearance for cows on the 4-h treatment was 37% less than for

4 Restricting Intake of Forages 185 TABLE 3. Effects of feeding round bales of hay for time restrictions of 4, 8, or 24 h on hay disappearance, manure production, calculated fecal output, and calculated hay waste (Experiment 1). Item 4 h 8 h 24 h SE Linear Quadratic Hay disappearance, kg DM/d per head Manure production, kg DM/d per head a Fecal output, kg DM/d per head b Hay waste, kg/d per head c Hay waste, % d a hysical collection of manure from pens, includes hay waste. b Calculated from chromium concentration in feces. c Calculated by subtracting fecal output from manure production. d Calculated by dividing hay waste amount by hay disappearance. cows on the 24-h treatment (Table 3). Linear (=0.001) and quadratic (= 0.007) increases were observed for hay disappearance (kg DM/d per head) for cows with longer time allowances to hay. Similarly, manure production (kg DM/d per head) linearly increased (=0.002) with increasing time allowance to hay. As expected, the corresponding fecal output, hay waste, and percentage of hay waste all had numerical tendencies to increase with longer time allowances to hay. ercentage of hay waste nearly doubled from the 4-h treatment (9.8%) to the 24-h treatment (18.1%), but because of variation, it was not significant (=0.43). Linear (=0.01) and quadratic (= 0.02) increase for N disappearance (kg/d per head) was observed with increased time allowance to hay (Table 4). This was expected, as DM disappearance was not similar across treatments. No effects among treatments for percentage of N,, or K in pen manure samples were observed. However, amounts of manure N,, and K (kg/d per head) all increased linearly (=0.01) with increasing time allowance to hay. Total N and total in manure (kg/d per head) were decreased approximately 40% when the 4-h treatment was compared with the 24-h treatment. Observed reductions in N and output concur with findings of Driedger and Loerch (1999), where similar reductions in N and were observed. However, diets used by the latter researchers were formulated to provide similar daily intakes of net energy of lactation, protein, vi- TABLE 4. Effects of feeding round bales of hay for time restrictions of 4, 8, or 24 h on nutrient manure (Experiment 1). tamins, and minerals according to NRC recommendations. Those researchers indicated that reductions of N and in limit-fed, high corn diets were likely due to a combination of decreased DMI and DM excretion. Similarly, in this trial, DMI and DM manure production were reduced (<0.002) for the restricted time treatments. Fifty to 90% of the excreted N can be volatilized to the atmosphere or lost by percolation and runoff, resulting in manure with a lesser N: compared with fresh manure (Stewart, 1970). Nitrogen losses are variable with time of year, with 60 to 70% of excreted N lost during the summer months and about 40% lost from November to May. Klopfenstein and Erickson (2001) noted that decreasing N inputs led to decreases in N excretion and volatilization. Although no direct measurements of volatilization or leeching were taken, the percentage of N recovered as a percentage of N disappearance was about 33%. Thus, the remaining two-thirds of the N was retained in the animal, partitioned to milk, or excreted where it was subject to volatilization or leeching. No differences in percentage of N recovered as a percentage of N disappearance were observed Item 4 h 8 h 24 h SE Linear Quadratic N Disappearance, kg/d per head a N, % N, kg/d per head b N Recovered, % c , % , kg/d per head b K, % K, kg/d per head b a Calculated from hay protein analysis and average pen hay disappearance data. b Nutrient output figures were calculated from average pen manure production. c Calculated as a percentage of N disappearance.

5 186 Cunningham et al. TABLE 5. Effects of feeding round bales of hay for time restrictions of 3, 5, or 7 h or ground hay fed at 90% of NRC requirements on cow performance (Experiment 2). Item 3 h 5 h 7 h 90% a SE Linear Quadratic 5 h vs 90% Initial BW, kg Initial BCS b Final BW, kg Final BCS b BW Change, kg BCS Change a Ground hay was fed at 90% of NRC requirements for energy and protein. b BCS = body condition score (1- to 9-point scale). among the differences in time allowance to hay. Cows in this study lost BW; therefore, we would assume that cows had very little lean tissue growth, which requires low amounts of N. However, protein in milk (3.4%) likely accounts for a considerable amount of N from the cow. It is then used for lean tissue growth in the calf or is excreted. Calf manure was included in the total pen manure collected, so it includes N excretion from calves. Experiment 2. Cow performance was analyzed for linear and quadratic effects among the 3-, 5-, and 7-h treatments and between the 5-h and the 90% treatment (Table 5). Initial BW (593.0 ± 18.6) and BCS (5.5 ± 0.16) were similar across treatments. No differences were observed in cow final BCS or BCS changes. In contrast, improvements in final cow BW (=0.08) and cow BW change (=0.04) were observed with increasing time allowances. Cows receiving the 7-h treatment gained nearly 25 kg more compared with cows on the 3-h treatment. The animal performance in this trial was similar to that observed in Experiment 1. Both trials show a trend for a lesser level of performance for cows with restricted time of access to hay. In Experiment 2, the 5-h treatment was compared with the 90% NRC ground hay treatment. This comparison was made because projected intake levels of the 5-h treatment would be similar to those of cows receiving the 90% NRC for maintenance ground hay treatment. For this comparison, no differences in cow performance were observed. Hay disappearance (kg DM/d per head) decreased (=0.01) as access time decreased (Table 6). Cows allowed access for 3 h consumed approximately 23% less hay than cows on the 7-h treatment. Manure production (kg DM/d per head) tended to increase (=0.08) for the three time-restricted treatments; however, fecal output tended to show a quadratic effect (=0.09). Manure production (= 0.09) and fecal output (=0.03) were less (<0.10) for the 90% NRC ground hay treatment compared with the 5-h restricted treatment; however, no differences were observed in cow performance among the different lengths of time allowance to hay. These differences were likely due to reduced intake of the 90% treatment or to reduction in particle size with grinding, resulting in more efficient utililization of the hay for cows. Reducing particle size of forages by fine grinding results in increased rate of passage of particulate matter from the rumen and subsequently decreases digestibility of OM and fiber (Thompson and Beever, 1980; Fahey et al., 1993). Alwash and Thomas (1971) reported the depression in digestibility of finely ground material (0.32-cm screen) compared with more coarsely chopped forage is negligible at maintenance intakes. Although hay in this study was more coarsely ground (7.6- cm screen), if intakes are restricted and rate of ruminal turnover is slowed because of less OM in the rumen, it is logical that forage of a smaller particle size is more efficiently used when compared with long-stem hay. This increase in efficiency may be due to increased surface area available to cellulolytic bacteria. No differences in hay waste or percentage of hay waste were observed; however, all hay was fed at restricted levels with small differences in time of access. ercentages for N,, and K in manure were similar for all treatments (Table 7). Nitrogen disappearance (kg/ d per head) linearly increased with increasing time allowances. In agreement with Experiment 1, linear treatment effects for N (=0.001), (=0.001), and K (=0.02) amounts (kg/d per head) were observed. Additionally, N and amounts in manure were significantly reduced for the 5-h vs the 90% NRC treatment (=0.02 and =0.04, respectively). These results are interesting, as the 90% NRC treatment had numerically lower DM disappearance (7.5 vs 8.0 kg/d per head) and significantly lower manure production (=0.08) and fecal output (=0.03) when compared with the 5- h treatment. These results agree with observations of Hutchinson and Mor-

6 Restricting Intake of Forages 187 TABLE 6. Effects of feeding round bales of hay for time restrictions of 3, 5, or 7 h or ground hay fed at 90% of NRC requirement on hay disappearance, manure production, calculated fecal output, and calculated hay waste (Experiment 2). Item 3 h 5 h 7 h 90% a SE Linear Quadratic 5 h vs 90% Hay disappearance, kg DM/d per head Manure production, kg DM/d per head b Fecal output, kg DM/d per head c Hay waste, kg/d per head d Hay waste, % e a Ground hay was fed at 90% of NRC requirements for energy and protein. b hysical collection of manure from pens, includes hay waste. c Calculated from chromium concentrations in feces. d Calculated by subtracting fecal output from manure production. e Calculated by dividing hay waste amount by hay disappearance. ris (1936) and Hironaka et al. (1970). Those researchers indicated trends for increased N excretion with increased DMI and DM excretion. ercentage of N recovered as a percentage of N disappearance linearly increased (=0.02) with increasing time allowance to hay. Additionally, cows receiving the 90% NRC treatment had a significantly reduced (=0.01) percentage of N recovery, indicating that a difference in volatilization or utilization ex- ists between the ground and long hay fed at restricted levels. These results do not agree with the results of Experiment 1, where no differences in percentage of N recovery were observed with restricted forage intake. However, in this trial, cows were gestating and were more restricted, which allowed for more efficiently utilized N as it was partitioned for fetal growth and late gestation maintenance requirements. Experiment 3. Initial BW and BCS did not differ (Table 8), and no differences in cow or calf performance were observed when hay was fed at 80, 90, or 100% of NRC. Final cow BW and BW change were similar across treatments, and final BCS and BCS change did not differ. Calf performance also did not differ significantly across treatments. As designed, a linear effect (= 0.001) was observed for hay disappear- TABLE 7. Effect of feeding round bales of hay for time restrictions of 3, 5, or 7 h or ground hay fed at 90% of NRC requirements on nutrient output of manure (Experiment 2). Item 3 h 5 h 7h 90% a SE Linear Quadratic 5 h vs 90% N Disappearance, kg/d per head b N, % N, kg/d per head c N Recovered, % d , % , kg/d per head c K, % K, kg/d per head c a Ground hay was fed at 90% of NRC requirements for energy and protein. b Calculated from hay protein analysis and average pen hay disappearance data. c Nutrient output figures were calculated from average pen manure production. d Calculated as a percentage of N disappearance.

7 188 Cunningham et al. TABLE 8. Effects of feeding ground hay at restricted levels (80, 90, or 100% of NRC requirements) on cow and calf performance (Experiment 3). Item 80% 90% 100% SE Linear Quadratic Initial BW, kg Initial BCS a Final BW, kg Final BCS BW Change, kg BCS Change Initial calf BW, kg b Final calf BW, kg Calf ADG, kg/d a BCS = Body condition score (1- to 9-point scale). b Calf birth BW was used as calf initial BW. ance (kg DM/d per head) (Table 9). Although manure production (kg DM/d per head) numerically increased with increasing amounts of intake, it was not significant (=0.36). Results of this study were different from Experiment 1. Cow performance did not differ for cows fed restricted levels of ground hay. In contrast, a linear treatment effect was observed for final cow BW and BCS change in Experiment 1 when cows had increasing time allowances to hay. One factor that might have contributed to the success of the cows in the present ex- TABLE 9. Effects of feeding ground hay at restricted levels (80, 90, or 100% of NRC requirements) on hay disappearance, manure production, calculated fecal output, and calculated hay waste (Experiment 3). Item 80% 90% 100% SE Linear Quadratic Hay disappearance, kg DM/d per head Manure production, kg DM/d per head a DM Recovery, % b a hysical collection of manure from pens, includes hay waste. b Calculated as a percentage of DM disappearance. periment was the addition of the 200 mg/d of the ionophore monensin to the diet. The addition of monensin to the high fiber diets has been shown to increase digestibility (ond and Ellis, 1979; ond et al., 1980; Faulkner et al., 1985) and performance (Oliver, 1975; Boling et al., 1977). The addition of monensin in all diets in this experiment and the effects of grinding hay previously discussed could explain differences in hay disappearance and cow performance observed in Experiments 1 and 2. ercentage of DM recovery as a percentage of DM disappearance was calculated for each pen from hay disappearance and manure production. Although a trend for decreasing percentage of DM recovery was observed with increased restriction, no statistical differences were observed. A trend for increased percentage of N(=0.06) in the manure was observed with increased consumption; however, no effect was noted for and K (Table 10). Nitrogen disappearance increased linearly (=0.01) with increasing feeding level. When nutrient percentages were used to calculate amount of nutrients in manure, a trend for increased N,, and K with increased feeding level was observed (=0.11, =0.09, and =0.21 respectively). These results agree with findings in the previous experiments, as linear diet effects were observed for nutrient output. These data also agree with results reported by Hutchinson and Morris (1936) and Hironaka et al. (1970), where increases in N excretion were a result of increased DMI or DM excretion. As was observed in Experiment 1, percentage of N recovered as a percentage of N disappearance did not differ among feeding level. These observations indicate similar utilization and volatilization for the lactating cows. Implications Restricting intake of forages is a feasible management alternative to feeding hay ad libitum and can decrease hay waste, manure production, and nutrient output. However, it should be noted that a hay analysis should be performed to ensure hay is at least average quality to prevent restricting intake of a poor quality forage and sacrificing cow performance. Although reduced intake of forages tended to decrease cow performance, acceptable levels of performance on the restricted treatments were achieved. Hay waste was numerically decreased for cows receiving shorter access times to round bales. Restricting intake of forages was shown

8 Restricting Intake of Forages 189 TABLE 10. Effects of feeding ground hay at restricted levels (80, 90, or 100% of NRC requirements) on nutrient output of manure (Experiment 3). Item 80% 90% 100% SE Linear Quadratic N Disappearance, kg/d per head a N, % N, kg/hd/d c N Recovered, % d , % , kg/d per head c K, % K, kg/d per head c a Calculated from hay protein analysis and average pen hay disappearance data. b Nutrient output figures were calculated from average pen manure production. c Calculated as a percentage of N disappearance. Hutchinson, J. C. D., and S. Morris The digestibility of dietary protein in the ruminant. I. Endogenous nitrogen in starvation. Biochem. J. 30:1682. Klopfenstein, T. J., and G. E. Erickson Effects of manipulating protein and phosphorus nutrition of feedlot cattle on nutrient management and the environment. J. Anim. Sci. 79 (Suppl. 1):97. Loerch, S. C Effects of feeding growing cattle high-concentrate diets at a restricted intake on feedlot performance. J. Anim. Sci. 68:3086. Loerch, S. C Limit-feeding corn as an alternative to hay for gestating beef cows. J. Anim. Sci. 74:1211. Miller, A. J., D. B. Faulkner, R. K. Knipe, D. R. Strohbehn, D. F. arrett, and L. L. Berger Critical control points for profitability in the cow-calf enterprise. rof. Anim. Sci. 17:295. Murphy, T. A., S. C. Loerch, and F. E. Smith Effects of feeding high-concentrate diets at restricted intakes on digestibility and nitrogen metabolism in growing lambs. J. Anim. Sci. 72:1583. to reduce manure production, and N,, and K output. From these results, restricting intake of forages may be an effective tool for producers wishing to achieve a desired level of performance. otential benefits would include reducing hay needs, hay waste, manure production, and nutrient output. Factors such as mature cow size, cow condition, hay quality, and environmental conditions are important variables that would determine whether this program could be utilized. Literature Cited Alwash, A. H., and. C. Thomas The effect of the physical form of the diet and the level of feeding on the digestion of dried grass by sheep. J. Sci. Food Agric. 22(12):611. Boling, J. A., N. W. Bradley, and L. D. Campbell Monensin levels for growing and finishing steers. J. Anim. Sci. 44:867. Driedger, L. J., and S. C. Loerch Limitfeeding corn as an alternative to hay reduces manure and nutrient output by Holstein cows. J. Anim. Sci. 77:967. Fahey, G. C., Jr., L. D. Bourquin, E. C. Titgemeyer, and D. G. Atwell ostharvest treatment of fibrous feedstuffs to improve their nutritive value. In Forage Cell Wall and Digestibility. H. G. Jung, D. R. Buxton, R. D. Hatfield, and J. Ralph (Eds.). p 15. ASA-CSSA- SSSA, Madison, WI. Faulkner, D. B., T. J. Klopfenstein, T. N. Trotter, and R. A. Britton Monensin effects on digestibility, ruminal protein escape and microbial synthesis on high fiber diets. J. Anim. Sci. 61:654. Hicks, R. B., F. N. Owens, D. R. Gill, J. J. Martin, and C. A. Strasia Effects of controlled feed intake on performance and carcass characteristics of feedlot steers and heifers. J. Anim. Sci. 68:233. Hironaka, R., C. B. Bailey, and G. C. Kozub Metabolic fecal nitrogen in ruminants estimated from dry matter excretion. Can. J. Anim. Sci. 50:55. NRC Nutrient Requirement of Beef Cattle. (7th Ed.). National Academy ress, Washington, DC. Oliver, W. M Effect of monensin on gains of steers grazed on coastal bermudagrass. J. Anim. Sci. 41:999. ond, K. R., and W. C. Ellis The effects of monensin on intake, digestibility, and rate of passage in cattle grazing coastal bermuda pasture. J. Anim. Sci. 49 (Suppl. 1):32. ond, K. R., W. C. Ellis, and J.. Telford Monensin effects on intake, digestibility, and rate of passage or ryegrass grazed by cattle. J. Anim. Sci. 51 (Suppl. 1):32. Schoonmaker, J.., S. C. Loerch, J. E. Rossi, and M. L. Borger Stockpiled forage or limit-fed corn as alternatives to hay for gestating and lactating beef cows. J. Anim. Sci. 81:1099. Stewart, B. A Volatilization and nitrification of nitrogen from urine under simulated cattle feedlot conditions. Environ. Sci. Technol. 4:579. Thompson, D. J. and D. E. Beever In Digestive hysiology and Metabolism in Ruminants. Y. Ruckebusch and. Thivends (Eds.). p 291. AVI ublishing Co., Westport, CT.