J. Anim. Sci. 2005. 83:2696-2704
© 2005 American Society of Animal Science
Grazing and feedlot performance of yearling stocker cattle integrated with spring- and fall-calving beef cows in a year-round grazing system1
N. A. Janovick Guretzky2,
J. R. Russell3,
D. R. Strohbehn and
D. G. Morrical4
Department of Animal Science, Iowa State University, Ames 50011
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Abstract
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Effects of calving season and finishing system on forage and concentrate consumption and carcass characteristics of calves were compared. In each of 3 yr, two replicates of three growing and finishing systems were compared including 1) spring calves finished on a high-grain diet in a feedlot immediately post-weaning (WF); 2) spring calves backgrounded on a hay-corn gluten diet over winter for 179 ± 18 d after weaning, grazed for 98 ± 9 d in cool-season grass-legume pastures, and finished on a high-grain diet in a feedlot (SGF); and 3) fall calves backgrounded on a hay-corn gluten feed diet over winter for 69 ± 31 d after weaning, grazed for 98 ± 9 d in cool-season grass-legume pastures, and finished on a high-grain diet in a feedlot (FGF). During the grazing phase, calves on the SGF and FGF treatments were equally stocked with spring-calving cow-calf pairs before grazing by pregnant fall-calving cows in a first-last rotational stocking system at a rate of 1.9 standard livestock units/ha. As designed, retained calves in the FGF system spent 110 fewer days in the drylot during backgrounding than retained calves in the SGF system (P = 0.01), resulting in less feed provided during winter. A greater (P < 0.01) quantity of hay was fed to SGF calves after weaning over winter (1,305 kg of DM per calf) than the quantity fed to FGF calves (305 kg of DM per calf). Quantity of grain (including commercial starter) fed to SGF calves after weaning did not differ (P = 0.28) from that fed to FGF calves (126 vs. 55 kg of DM per calf); however, calves in the FGF system required 80 and 71 kg of DM per calf more concentrate to finish to an equivalent external fat thickness compared with SGF and WF calves, respectively (P = 0.02). Average daily gains in the feedlot were greater (P < 0.01) for SGF and FGF calves than for WF calves during all 3 yr. There were no differences (P = 0.69) in carcass quality grades among calves in all groups, but SGF calves had greater (P < 0.01) hot carcass weight and LM area measurements at slaughter than FGF or WF calves. Although calves in the FGF system were 25 kg lighter than calves in the WF system at slaughter (P = 0.03), and had a lower dressing percent (P = 0.03), other carcass characteristics did not differ between these two groups. Lower stored-feed requirements and similar carcass quality characteristics made retention of a fall calf crop advantageous over retention of a spring calf crop for use as stocker animals before finishing.
Key Words: Animal Production • Cattle • Finishing Systems • Integrated Systems
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Introduction
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Retention of calves after weaning for use as stocker cattle in summer pastures improves profit to beef cow-calf operations by increasing the value of calves (Allen et al., 1992a
). Retaining a weaned calf crop over winter, however, requires feeding stored feeds (Allen et al., 1996; Hersom, 1999) before animals graze summer pastures. Unless corn crop residues (Fernandez-Rivera and Klopfenstein, 1989) or stockpiled forages can be grazed, stored feed costs will increase production costs of retained calves. Even so, these costs could be offset in the finishing period. Ridenour et al. (1982) demonstrated that grazing calves before finishing decreased days in the feedlot and increased feed efficiency in the feedlot. Therefore, we hypothesized that use of grazing management strategies for weaned calves has potential to decrease the amount of concentrate fed during the finishing stage.
Another benefit of retaining a weaned calf crop is that it is a means to increase stocking rates early in the grazing season, at least temporarily, and to control excess forage growth of cool-season forage pastures (Olson et al., 1993; Hersom, 1999), resulting in the potential for more efficient utilization of forage by the beef herd. Because the majority of BW gains by stocker cattle on cool-season pastures occurs by mid-summer (Tucker et al., 1989), stockers can be removed before summer pasture growth slows and finished in a feedlot, providing a unique marketing time for these animals. Total animal production from integrated systems such as these has been evaluated in Virginia (Allen et al., 1992a,b; 1996; 2000); however, data are needed in areas such as Iowa to determine whether similar systems are practical in a more northern climate. Our objective was to compare production measurements of spring and fall calf crops retained after weaning and grazed before finishing with spring calves finished immediately after weaning in an integrated grazing system in the upper Midwest.
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Materials and Methods
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Finishing Systems
All protocols for animal use were reviewed and approved by the Institutional Animal Care and Use Committee at Iowa State University. A 3-yr study was conducted at the Iowa State University McNay Research and Demonstration Farm near Chariton, IA, using three replicated growing and finishing systems to compare the effects of calving season and production system on the amount of forage and concentrate consumed by calves to reach an equivalent carcass quality grade and on the carcass characteristics of finished cattle (Figure 1). Calves in Year 1 were produced in the last year of a previous experiment (Hersom, 1999). In Years 2 and 3, calves were produced by cows managed in one of two forage management systems described in Janovick et al. (2004). In both forage management systems, all bull calves were castrated within 3 d of birth, and all calves were vaccinated for respiratory diseases (IBR, BVD, PI3, and BRSV; Grand Laboratories, Novartis Animal Vaccines, Inc., Larchwood, IA) at weaning. Calves produced from each of the systems in Janovick et al. (2004) were retained in their respective system through finishing. Therefore, calves were assigned randomly to treatment groups in the present study based on the calving season in which they were born. On November 11, 1998 (Year 1), October 28, 1999 (Year 2), and October 17, 2000 (Year 3), 12 Angus-sired crossbred spring calves (mean BW = 227 ± 9.9, 248 ± 3.5, and 236 ± 10.4 kg; mean age = 5.3 ± 0.7, 6.1 ± 0.4, and 6.4 ± 0.4 mo in Years 1, 2, and 3, respectively) were weaned and assigned to one of two pens in a feedlot (wean-finish system; WF). Simultaneously, a second group of 12 Angus-sired crossbred spring calves (mean BW = 219 ± 16.3, 250 ± 12.0, and 234 ± 18.0 kg; mean age = 5.3 ± 0.5, 6.3 ± 0.05, and 6.7 ± 0.2 mo in Years 1, 2, and 3, respectively) were weaned and assigned to one drylot (spring-background-graze-finish systems; SGF).
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Figure 1. Calf and stocker management in the wean-finish, spring-wean-graze-finish, and fall-wean-graze-finish systems.
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Calves in the WF system were fed a high-grain diet (Tables 1 and 2) ad libitum until slaughter, when approximately 50% of the cattle were estimated to achieve a USDA quality grade of low Choice based on an estimated external fat thickness of 1 cm. Calves in the SGF system were fed endophyte-free tall fescue (Festuca arundinacea Schreb. cv. Johnstone)-red clover (Trifolium pratense cv. Arlington) or smooth bromegrass (Bromus inermis var. Barton)-red clover hay as large round bales ad libitum plus pelleted corn gluten feed or corn grain to achieve a rate of gain of approximately 0.2 kg/d until initiation of summer grazing. Simultaneous to assignment of spring calves to the feedlot pens and drylot, 12 Angus-sired crossbred fall calves grazed with cows in replicated 6.1-ha stockpiled tall fescue-red clover pastures and were weaned on March 2, March 3, and January 17 (heavy snow and ice cover in January prevented cows from accessing stockpiled forage; therefore, calves were weaned early) in Years 1, 2, and 3 respectively (Janovick et al., 2004). In Year 1, fall calves entered the project at approximately 2 mo of age, but because of lack of birth records, variability in age at weaning could not be determined. At weaning, fall calves (mean BW = 189 ± 5.7, 213 ± 14.1, and 187 ± 26.1 kg; mean age = approximately 5.6, 6.1 ± 0.5, and 4.4 ± 0.2 mo in Years 1, 2, and 3, respectively) were placed in one drylot (FGF) and fed endophyte-free tall fescue-red clover or smooth bromegrass-red clover hay as large round bales at an ad libitum level with corn gluten feed to allow 0.2 kg of gain/d (based on results from a previous study; Hersom, 1999) until the initiation of summer grazing.
At the initiation of summer grazing on April 22, April 26, and May 2 in Years 1, 2, and 3, respectively, the 12 calves from the SGF (mean BW = 303 ± 6.2, 334 ± 3.9, and 318 ± 9.3 kg in Years 1, 2, and 3, respectively) and 12 calves from the FGF (mean BW = 229 ± 0.2, 250 ± 2.7, and 223 ± 14.0 kg in Years 1, 2, and 3, respectively) systems were assigned by calving season to one of two 8.1-ha smooth bromegrassorchardgrass (Dactylis glomerata var. Napier)-birdsfoot trefoil (Lotus corniculatus var. Norcen) pastures to graze as stocker cattle (six fall and six spring calves per pasture) for an average of 98 ± 9 d. Stocker cattle were rotationally stocked in paddocks with six spring-calving Angus-sired crossbred cow-calf pairs at 1.9 standard livestock units (SLU)/ha, assuming that one SLU equals 1 nonlactating 500-kg cow (Minson and Whiteman, 1989) to a grazing efficiency of approximately 33% based on the forage mass estimated with a falling plate meter (4.8 kg/m2) and estimated DMI of 3.5% BW per cow-calf pair and 3% BW per stocker (Hermann et al., 2002). Six gestating fall-calving Angus x Jersey x Simmental cows were stocked in paddocks following movement of spring-calving cows and calves and stockers to the next paddock in a first-last stocking system using a combined stocking rate of 2.68 SLU/ha and an estimated total grazing efficiency of 50%, assuming a DMI of 2.5% BW. On June 17, June 21, and June 18 in Years 1, 2, and 3, respectively, the spring-calving cow-calf pairs and fall-calving cows were moved to graze other pastures during the breeding season of the spring-calving cows (Janovick et al., 2004). Stocker cattle remained in the smooth bromegrass-orchardgrass-birdsfoot trefoil pastures to graze by rotational stocking at 1.03 SLU/ha to an estimated grazing efficiency of 50% until August 5, August 2, and July 30 in Years 1, 2, and 3, respectively. After grazing, stocker animals from the SGF and FGF systems were removed from the pasture, separated by age and placed in replicated pens in a feedlot for finishing on a high-grain diet (Table 1
) until a minimum of 50% of the cattle in an age group were estimated by one experienced individual to have achieved a USDA carcass quality grade of low Choice. Complete details of summer pasture management (Janovick, 2002) and stocking management (Janovick et al., 2004) have been discussed. Hay fed to weaned calves in the drylot period was harvested from the summer grazing systems (Janovick et al., 2004). Feedlot diets were kept as similar as possible between groups of calves and over the 3-yr period. As a result of limited feed storage capacity at the research farm, dietary ingredients were not identical among seasons and years. For example, soybean meal and corn silage were not fed to calves in Year 3.
Calves in all systems were sequentially implanted with Synovex S and Synovex H (Hoechst-Roussel Vet, Somerville, NJ) and Revalor S and Revalor H (Hoechst-Roussel Vet) implants for steers and heifers, respectively. Wean-finish calves were implanted at weaning, then after 100 d in the feedlot. Spring-graze-finish calves were implanted as they were put into pastures, then as they were put into the feedlot. Fall-graze-finish calves were implanted in June while on pasture, then after 60 d in the feedlot.
Measurements
Feedlot diets (total mixed rations) were delivered to bunks with a mixer wagon. While in the feedlot, feed offered and feed refused were recorded to determine the quantity of feed disappearance. While in the drylot, during grazing of summer pastures, and finishing in the feedlot, calves were weighed monthly without feed withdrawal. In the drylot, hay bales and supplement were weighed at the time of feeding to determine the amount of DM fed/consumed. No adjustment was made for wasted hay. Calves were slaughtered at a commercial packing plant. At slaughter, carcasses were weighed, LM area and backfat thickness were measured by tracing a ribbed section onto acetate paper, and marbling score, quality grade, and yield grade were determined by a USDA grader. In Year 1, LM area and backfat thickness data were not available for the WF calves. Feed efficiencies were calculated by dividing the total amount of BW gain for a finishing period by the total DM or concentrate consumed for that period.
Statistical Analyses
In this study, the smallest unit to which treatments were applied was the pasture of animals or pen in the feedlot; therefore, each replicate of cattle groups was the experimental unit. The length of the drylot, grazing and finishing phases for calves, BW gains during all phases, forage and concentrate consumed during the drylot and finishing phases, and carcass characteristics for this study were analyzed as a completely randomized design with the GLM procedure (SAS Inst., Inc., Cary, NC) for the effects of year, treatment, and the year x treatment interaction, using replicate within year and treatment as the error term. In the SGF and FGF groups, calves were moved through the drylot and pasture phases of finishing on the same dates; therefore, for these analyses, years were replications of treatment, and the interaction between group treatment and year could not be tested.
Three a priori questions concerning feeding phase lengths, feed use, animal production, and carcass characteristics were investigated with contrast statements. These were: 1) the difference between retaining a fall and a spring calf crop and grazing them before finishing (FGF vs. SGF), 2) the difference between retaining a fall calf crop and grazing them before finishing and finishing calves immediately after weaning (FGF vs. WF), and 3) the difference between retaining a spring calf crop and grazing them before finishing and finishing calves immediately after weaning (SGF vs. WF). Significance for all tests for differences among means was declared at a probability of < 0.05.
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Results
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Because calves in the FGF and SGF systems were used as stocker animals in summer pastures in the grazing season following their birth, they were retained 137 and 208 d longer, respectively, than calves from the WF system (P < 0.01; Table 3) from the time of weaning to the time of slaughter. As designed, the FGF and SGF groups grazed the same number of days each season on pasture before finishing. Because calves in the WF system were finished immediately after weaning, the total days on feed and days in the feedlot were synonymous. Calves in the FGF group were maintained for an average of 110 fewer days in the drylot over winter than SGF calves (P < 0.01), but they required 38 d more to reach a similar carcass quality grade during the finishing stage in the feedlot (P = 0.02).
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Table 3. Length of finishing phases and amount of concentrate, forage, and total DM fed to calves in each treatment group while in the drylot and feedlot over 3 yr
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The mean quantity of hay fed to calves in the SGF system in the drylot was nearly 1,000 kg of DM per calf greater than the amount fed to the FGF calves, but the quantities of concentrate fed to calves in these systems did not differ (P = 0.28; Table 3). The quantities of hay fed in the drylot to calves in the FGF and SGF systems were 492 and 1,542 kg of DM per calf in Year 3 compared with 173 and 1,243 kg of DM per calf in Year 1 and 249 and 1,128 kg of DM per calf in Year 2. Although year effects could not be tested for these data because calves were fed in the same drylot, the difference observed in amounts of hay fed among years was most likely a result of colder weather conditions and greater snowfall and ice cover, which required that fall calves be weaned 43 d earlier in Year 3 than either Year 1 or 2.
Total quantity of DM fed in the feedlot to calves in the SGF and WF system did not differ (P = 0.29), whereas calves in the FGF system required 92 and 126 kg of DM per calf more than calves in the SGF and WF systems, respectively (P < 0.01). Similarly, although there were no differences in the quantities of concentrate DM fed per calf during the feedlot phase between calves in the WF and SGF systems, the quantities of concentrate DM fed to calves in the FGF system were greater (P < 0.01) than that fed to calves in either the WF or SGF systems. Year and a year x system interaction affected the amounts of forage and concentrate fed during the feedlot phase (P < 0.01). Mean quantities of concentrate (1,470 kg of DM per calf) and forage (379 kg of DM per calf) fed in Year 3 were greater than quantities fed in Year 1 (1,327 and 263 kg of DM per calf) and Year 2 (1,397 and 295 kg of DM per calf). In Year 3, WF calves required more forage and concentrate than FGF calves (P < 0.01; P = 0.01), respectively and SGF calves (P < 0.01; P < 0.01), respectively.
Because of the quantity of hay needed during the drylot phase, calves in the SGF group required 987 and 1,347 kg of DM per calf more total forage (P < 0.01) than calves in the FGF and WF systems over all feeding phases to reach an equivalent external fat thickness at carcass harvest. Year affected the total quantity of forage fed to all calves (P < 0.01) and tended to affect the total quantity of concentrate fed (P = 0.06). More concentrate (1,543 kg of DM per calf) and forage (1,057 kg of DM per calf) was fed in Year 3 than in Year 1 (1,403 and 735 kg of DM per calf) or Year 2 (1,428 and 754 kg of DM per calf). In Year 1, SGF and FGF calves required more concentrate (312 and 582 kg of DM per calf, respectively) than the WF group (P < 0.01); however, the total quantity of concentrate DM required to finish calves over all phases did not differ between SGF and WF groups (system; P 
0.01).
Compared with calves in the SGF system, calves in the FGF system had greater (P < 0.01) daily BW gains in the drylot but lower (P = 0.02) daily BW gains while grazing smooth bromegrass-orchardgrass-birdsfoot trefoil pastures during the summer (Table 4). Average daily BW gains during the feedlot phase for fall and spring calves that were backgrounded during the winter and grazed during the summer were greater (P < 0.01) than calves in the WF system. Whereas the feeding of hay and concentrate was designed to yield daily BW gains of 0.2 kg/d during the drylot phase, gains by calves in the FGF and SGF systems were 3.5 and 2 times greater than experimentally designed. Total BW gains of calves in the FGF system were less than those of calves in the SGF system during the drylot phase (P < 0.01) and tended (P < 0.07) to be lower during the grazing phase. Total BW gained while in the drylot for FGF and SGF calves were 40 and 50 kg; 38 and 97 kg; and 56 and 64 kg in Years 1, 2, and 3, respectively (system, P < 0.01; year, P < 0.01). Subsequent total BW gains while on pasture for FGF and SGF calves were 71 and 62 kg; 59 and 78 kg; and 36 and 52 kg in Years 1, 2, and 3, respectively (year; P < 0.01). Despite the difference in daily BW gains, mean total BW gained in the feedlot did not differ between FGF and WF calves (P = 0.09). Nonetheless, in Years 1 and 2, calves in the FGF system required more total weight gain in the feedlot to reach a similar finishing condition than spring calves in the SGF and WF systems (system x year; P < 0.01).
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Table 4. Average daily gain and total BW gain for calves and stocker steers and heifers in the drylot, on pasture, or in the feedlot each year
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The average BW and ages at the initiation of the finishing period for each group of calves were 286, 380, and 250 kg (SE = 3.6) and 11.8, 16.4 and 6.1 mo (SE = 0.21) for calves in the FGF, SGF, and WF systems, respectively. Over the 3 yr, BW gain per unit of total feed during finishing in the feedlot for calves in the FGF system and calves in the WF system was greater (P < 0.05) than calves in the SGF system (Table 5). In Year 1, no difference in total BW gain per unit of feed was observed across calf groups (P = 0.67). In Years 1 and 3, no difference in the quantity of concentrate fed per unit of gain was observed among all groups of calves (P = 0.58 and 0.21, respectively), and in Year 2, efficiency for the FGF or WF calves was 0.06 units more than that of SGF calves (P = 0.03). No year or year x system interactions were observed for feed efficiency expressed either as total DM or total concentrate consumed in the feedlot phase. Over the drylot and feedlot phases, both FGF and SGF calves used total concentrate fed more efficiently for gain than the WF group (P < 0.01). Colder winter temperatures during finishing in Year 3 (year; P < 0.01) contributed to less efficient feed utilization in this year than in other years for all groups of calves. Calves in the SGF system used total DM fed more efficiently for gain than either FGF or WF calves (P < 0.01). Except for Year 2, FGF calves were more efficient in use of concentrates than SGF or WF calves (P < 0.05). Calves in the FGF and SGF system had higher efficiency of concentrate use in all three years of the trial than WF.
As designed, the percentage of calves achieving a quality grade of low Choice or greater based on external fat thickness did not differ between systems (Table 6). Spring and fall calves in the SGF and FGF systems, respectively, had greater (P < 0.05) live and hot carcass weights at slaughter than calves in the WF system. Similarly, live and hot carcass weights at slaughter were greater (P < 0.05) for calves in the SGF system than for calves in the FGF system. Although dressing percentages of calves in the FGF system were lower (P < 0.03) than those of calves in the WF or SGF systems, percentage retail product did not differ (P = 0.58) among systems. Calves in the SGF system had greater (P < 0.01) LM areas than calves in the FGF or WF systems in the 2 yr that could be compared; however, backfat thickness, marbling score, and yield grade did not differ among systems.
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Table 6. Mean final weight, hot carcass weight, and carcass characteristics for finished steers and heifers over 3 years
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Discussion
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Several benefits exist for retaining calves after weaning. First, no stocker animals need to be purchased for the following grazing season (Allen et al., 1992a), decreasing the costs and increasing annual beef production (Allen et al., 2000). Second, the price of beef at the time of slaughter is seasonal (May et al., 1999); therefore, delaying slaughter by allowing calves to graze as stockers before finishing would provide a supply of calves for slaughter several months after the traditional slaughter period for spring-born calves. Third, the inclusion of stocker animals into the grazing system used in this study increased the annual beef production per cow by 27 kg per cow during grazing in comparison with a system in which cow-calf pairs grazed without stocker cattle (Janovick et al., 2004). Previous studies also have reported increased annual beef production by 76 kg per cow (Hersom, 1999) and 37 kg per animal (Lewis et al., 1990b) compared with finishing calves immediately after weaning.
Improved feed efficiency observed during compensatory growth in the feedlot following grazing (Meyer et al., 1965; Horton and Holmes, 1978) also has potential to decrease the quantity of concentrates that are fed during finishing. Optimum use of grazing in the growing phase of the ruminant animal further improves feed efficiency in the feedlot (Ridenour et al., 1982). In the present study, the amount of hay fed to fall calves was less than that fed to spring calves because the weaning date was delayed until late winter. However, 5.3 and 8.0 kg of DM per calf daily were fed as hay and concentrate to fall and spring calves after weaning over winter, resulting in BW gains that were 2 to 3.5 times greater than the desired value of 0.2 kg/d. Considering the greater than desired gain, less stored feed was likely needed than was used for feeding the calves in the drylot phase. In a previous study, spring calves were weaned and maintained for 188 d over winter at an ADG of 0.19 kg/d before grazing in pastures (Hersom, 1999). These calves were fed 6.2 kg of DM per calf per day and required 316 kg of concentrate DM per calf less than the present study to reach desired carcass characteristics. There are other feeding strategies that can be employed to decrease the quantity of hay fed further. Over-wintering stockers on stockpiled tall fescue and grazing in summer before finishing decreased the number of days that hay was fed over winter by >50% and decreased the amount of hay fed by 1,184 kg per system (Allen et al., 2000). Grazing calves on corn crop residues also has been an effective way to maintain stocker animals over winter (Klopfenstein et al., 1987; Lewis et al., 1990a, b).
Lewis et al. (1990a) observed that BW gains during winter that were >0.28 kg/d decreased pasture gains by 81g for each 100-g increase in winter daily gain. Daily BW gains of calves in the FGF and SGF systems in the present study on pasture and in the feedlot were inversely related to gains in the drylot. Previous studies showed that the compensatory gain in the feedlot was inversely related to the gain in periods preceding it (Lewis et al., 1990a; Baker et al., 1992; Allen et al., 1996; Hersom, 1999). Although calves in the SGF system had greater ADG in the feedlot than calves in the WF system, they were less efficient at utilizing feed for gain compared with either calves in the WF system or calves in the FGF system. This decreased feed efficiency was likely caused by their greater BW at the initiation of finishing, which increased the proportion of energy used for maintenance (Lewis et al., 1990a). Ridenour et al. (1982) estimated that the quantity of concentrates fed to cattle during finishing could be decreased by grazing if cattle reached 50% of their final BW on pasture because of increased feed efficiency at lower BW. In the present study, calves in the FGF and WF systems had reached 50 and 49% of their final BW at the initiation of finishing; however, calves in the SGF system had reached 62% of their final BW at the time that finishing was initiated, which may further explain the decrease in feed efficiency observed in the feedlot for calves in this system.
Forage allowance also has affected daily BW gains of growing animals grazing pastures. Marsh (1979) observed that available forage allowances <10 kg/100-kg animal decreased growing animal performance. In contrast, NRC (1996) suggested that 5 kg forage/100 kg of BW was the level at which forage availability became limiting to intake and could be expected to affect animal performance. In the present study, forage allowances were 7 to 10 kg of DM/100-kg animal, which might have limited forage intake and daily gain.
In conclusion, the length of time calves are maintained after weaning directly affected the quantity of stored feed required to maintain them in this and other studies. A greater than desired daily weight gain during the winter period before grazing likely resulted in lower gains on pasture and, therefore, less gain over winter might have resulted in less stored feed being offered, as well as potentially better gains on pasture. Compensatory gain during finishing for spring and fall calves that were grazed before finishing was not readily evident in this study, although calves in the FGF system were more efficient at using feed resources than calves in the SGF and WF systems. In this study, BW at finishing seemed to influence the efficiency attained in the feedlot. Calves in the SGF system weighed more than either FGF or WF calves at initiation of finishing and had lower efficiency during finishing. As a result of the excessive quantities of hay fed and greater ADG than desired during the drylot phase and greater quantity of grain fed during finishing, there was no decrease in the amount of feed required to finish calves in the FGF or SGF systems compared with the WF system.
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Footnotes
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1 Journal paper of the Iowa Agric. and Home Econ. Exp. Stn., Ames. Project No. 3810 supported by Hatch Act and State of Iowa funds. The project was funded, in part, by a grant from the Leopold Center for Sustainable Agriculture, Iowa State Univ., Ames. 
2 Present address: Dept. of Anim. Sci., Univ. of Illinois, Urbana-Champaign 61801.
4 The authors gratefully acknowledge the assistance of L. J. Secor, D. R. Maxwell, M. L. Hermann, M. J. Hersom, and the animal caretakers at the McNay Research and Demonstration Farm for assistance in conducting this experiment, and acknowledge P. M. Dixon for assistance in statistical analysis.
3 Correspondence: 337 Kildee Hall (phone: 515-294-4631; fax: 515-294-3795; e-mail: jrussell{at}iastate.edu).
Received for publication December 7, 2004.
Accepted for publication July 6, 2005.
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Abstract
Introduction
