Feedlot Phase Research Articles

Effect of phase-feeding crude protein on performance and carcass characteristics of crossbred beef bulls: an application to reduce nitrogen compounds in beef cattle diets

Beef cattle (24) with an average initial body weight of 417 ± 54 kg were assigned in a 2 × 2 factorial design with six repetitions. The factors studied were two levels of CP: 11 (low CP) or 13 % (high CP) in the initial feedlot phase (days 1 - 36) and in the final phase (days 37 - 72). After 36 days, half of the bulls fed with each level of CP were selected to reverse the CP level. No interaction was observed (P > 0.05) between the level of protein in the initial and final phases on the intake of the nutrients evaluated. There was no effect (P > 0.05) of the protein levels in the initial and final phases on intake of dry matter, organic matter, CP, non-fiber carbohydrates, and total digestible nutrients. No differences were observed among treatments (P > 0.05) for average daily gain (X = 1.99 kg/day) and carcass traits. We conclude that it is possible to feed Holstein-Zebu crossed bulls with an average daily gain of approximately 2 kg using a fixed level of 11 % CP during the entire feedlot period, and this diet is economically viable and environmentally sound.

Evaluation of response to bovine viral diarrhea virus type 2 vaccination and timing of weaning on yearling ultrasound body composition, performance, and carcass quality traits in Angus calves1,2,3

There are concerns about antagonisms between immunity and animal productivity in livestock production. The objective of this study was to evaluate the effect of antibody levels through a response to vaccination protocol, weaning timing, and their interaction on performance and carcass quality traits in Angus beef cattle. Final antibody level and response to vaccination were based on neutralizing serum antibodies against bovine viral diarrhea virus type 2 (BVDV2). Calves were followed through development and the feedlot phase, with collection of yearling ultrasound (n=957), preharvest (n=762), and carcass (n=673) data. In this study, 48% of the animals were observed to have positively responded to the vaccine, as evidenced by higher final antibody levels compared to prevaccination antibody levels. Increased final antibody levels were significantly (P<0.05) associated with increased yearling weight and increased subcutaneous fat over the rump. An interaction between final antibody level and weaning time also was associated (P<0.05) with Warner-Bratzler shear force (WBSF) and meat pH, with a favorable, negative relationship between final antibody and WBSF in calves weaned at initial vaccination. Overall antibody response by wean time interaction had a significant (P<0.05) association with ADG and meat pH, with calves weaned at initial vaccination having a favorable, positive relationship between overall antibody response and ADG. Under both the final antibody and overall antibody response models, animals weaned at initial vaccination had significantly (P<0.05) lower intramuscular fat at yearling time and conversely higher harvest weight than animals weaned at the booster vaccination. When antibody response was grouped (none, low, high), a significant interaction (P<0.05) between antibody response group and weaning time was identified for ADG, harvest weight, and HCW. Animals weaned at the initial vaccination in the high antibody response group had the advantage for ADG, harvest weight, and HCW compared to animals in the high-response group that were weaned at booster vaccination. Linear increases in antibody response generally did not have negative effects on performance or carcass quality traits in finished cattle (P>0.05). Therefore, producers should not be concerned about decreased production or quality attributes as a result of developing a robust antibody response to vaccination for BVDV2 in beef cattle.

Supplementation strategy during late gestation alters steer progeny health in the feedlot without affecting cow performance

Implementation of minimal supplemental strategies during late gestation has been reported to potentially increase post-weaning progeny health in the feedlot. Therefore, to investigate the effects of nutritional management strategies during late gestation on cow and subsequent steer progeny performance, 103 gestating cows grazing dormant winter range were utilized at Corona Range and Livestock Research Center, Corona, NM. Cows were supplemented with (1) a 36% crude protein (CP) supplement (CSM) fed 3×/wk at a rate of 454gcow−1d−1, (2) self-fed supplement comprised of 50% corn gluten meal and 50% mineral (SMP; 28% CP), or (3) cows fed no protein supplement during late gestation (NS). Cows were supplemented for 60 d from December until 2 wk prior to calving. Supplement consumption was 0.45, 0.17, and 0.00kg/d for CSM, SMP, and NS. After weaning, steers were preconditioned for 45 d and were received and treated as custom-fed commercial cattle at a feedlot in mid-November. Cow BW and BCS were not influenced (P≥0.55) by late gestation management strategy throughout the study. Prepartum supplementation strategies did not influence (P=0.75) subsequent pregnancy rates. Calf BW at weaning, during the feedlot phase, and HCW were not different (P≥0.52) among dam prepartum treatments. A greater percentage of steers from dams fed CSM and NS were treated for sickness than SMP steers (P=0.05). Death loss in the feedlot was greater (P=0.02) for steers from CSM dams. Steer carcass traits and quality were not different (P≥0.17) among prepartum management strategies. Net profit in the feedlot was decreased (P=0.05) in steers from CSM dams compared to steers from SMP and NS dams. In this study, the non-supplement treatment was as effective as SMP treatment for cow performance and profitability in the feedlot. This study indicates that feeding a high ruminally undegradable protein self-fed supplement during late gestation increases calf feedlot health in the feedlot compared to a traditional hand-fed, oilseed-based supplement.

On the relationships between glucocorticoids and feed efficiency in beef cattle

Improvement in the utilization of feed in livestock is an important target of breeding and nutritional programs. Recent evidence indicates a potential association between feed efficiency and fecal cortisol metabolites, which could eventually be used as an indirect assessment of this trait. This evidence is more comprehensively evaluated in here with samples for plasma cortisol (PC; ng/ml) and fecal cortisol metabolites (FCM; ng/ml) collected more often during the entire finishing phase in beef steers. Individual daily feed intake of 112 steers fed a high-moisture corn-based and haylage diet was measured over 168d. Body weight, blood and fecal samples were collected every 14d and ultrasound measures of backfat thickness and longissimus muscle area were taken every 28d. Four productive performance traits were calculated: daily dry matter intake (DMI), average daily gain (ADG), feed to gain ratio (F:G) and residual feed intake (RFI). At the end of the feedlot phase, steers were ranked according to RFI and samples were analyzed for PC and FCM from the 32 steers with greatest and 32 steers with lowest feed efficiency. In addition, a sub-group of 12 steers from each of these two groups with divergent feed efficiency were subjected to hourly blood sampling for 24h. Less efficient steers had greater DMI, F:G and consumed 1.5kg/d more DMI (P<0.05) than steers with improved feed efficiency. No differences (P>0.10) in PC over the 12 biweekly sampling periods between steers with divergent feed efficiency were observed. However, a trend toward significance between 19:00 and 02:00h over the hourly sampling evaluation was noticed, with the sub-group of more feed efficient steers presenting higher levels of PC in this period of the day (P=0.08). On the other hand, FCM levels displayed a distinct pattern between RFI groups over the biweekly sampling period, with more efficient cattle presenting greater levels of these metabolites (P<0.05). This study reinforces the positive association between improved feed efficiency and FCM levels over the finishing phase; and the lack of association between feed efficiency and PC when single samples are collected every two weeks through a single jugular venipuncture performed after handling the cattle for sampling. Further studies to develop sampling protocols for assessing FCM as an indicator trait for feed efficiency are warranted, as well as, studies to understand the role of endogenous glucocorticoids in the performance of the bovine.

Effect of forage type in the stocker phase and its effect on subsequent feedlot performance and carcass characteristics of beef steers

ABSTRACT The focus of most research on beef weaning programs is to evaluate effects of age and diet on calf performance with a particular interest on preconditioned health program to maximize BW gain. In support of the forage-based production system, research needs to be conducted to evaluate the potential of different forages to facilitate weaning and continuation into forage-based development programs. In each of 2 yr, 48 weaned beef steers were used to evaluate performance when grazing monocultures of endophyte-free tall fescue [Lolium arundinaceum (Schreb.) S.J. Darbyshire = Festuca arundinacea Schreb.; TF] and alfalfa (Medicago sativa L.; ALF) and the effect of these stocker treatments on subsequent performance and carcass characteristics. Forages were not limiting in terms of mass produced and nutritive value. The greater nutritive value of ALF resulted in greater performance and pounds of beef produced per hectare compared with steers grazing TF. Steers grazing ALF tended to be heavier at the beginning of the feedlot phase, and the difference resulted in heavier (P

Effect of increasing distillers grains inclusion on performance and carcass characteristics of early-weaned steers1

Dried distillers grains with solubles (DDGS) contain elevated concentrations of CP, oil, and S, which can negatively impact performance and carcass characteristics in steers weaned at 205 d of age. Early weaned (EW) cattle, however, consume less DM and require increased CP. Furthermore, the energy required to dispose of excess N may actually decrease excessive fat accumulation, which can occur in EW cattle. Thus, we hypothesized that feeding diets with increased concentrations of DDGS to EW steers for the first 99 d would decrease fat thickness and increase harvest weights, and would not inhibit performance or marbling deposition. To test this hypothesis, 90 Angus × Simmental steers (199.7 ± 12.2 kg) were weaned at 134 d of age (EW) and allotted to 3 high concentrate diets (20% corn silage) containing either 0%, 30%, or 60% DDGS (15.7%, 15.8% and 21.7% CP, respectively). Dietary treatments were fed for 99 d, after which steers were placed on a common diet containing no DDGS (12.9% CP) until harvest at a common weight of 599 kg. Concentration of dietary DDGS did not affect ADG, DMI, or G:F during the growing phase (P > 0.41), did not produce any carryover effects on ADG, DMI, or G:F during the finishing phase (P > 0.26), and resulted in similar overall performance (P > 0.52). Dressing percentage (P < 0.05), HCW (P = 0.06), fat thickness (P = 0.10), and % KPH (P = 0.08) responded quadratically to early DDGS supplementation, increasing from 0 to 30% DDGS inclusion and decreasing from 30 to 60% DDGS inclusion, respectively. Marbling score was not affected (P > 0.46) by DDGS inclusion, but there was a tendency (P = 0.08) for the ratio of subcutaneous (SC) to intramuscular (IM) fat to be altered by DDGS inclusion. The ratio of IM to SC fat decreased from 0 to 30% DDGS inclusion and increased from 30 to 60% DDGS inclusion. These data suggest that inclusion of increased concentrations of dietary DDGS early in the feedlot phase does not negatively impact growth and performance of EW cattle, but does partition energy from carcass to noncarcass components. However, increased concentrations of DDGS did not negatively impact IM fat deposition. Utilization of energy for disposal of excess N may be responsible for changes in carcass weight and SC fat deposition.

Growth-promoting technologies decrease the carbon footprint, ammonia emissions, and costs of California beef production systems1

Increased animal performance is suggested as one of the most effective mitigation strategies to decrease greenhouse gas (GHG) and ammonia (NH(3)) emissions from livestock production per unit of product produced. Little information exists, however, on the effects of increased animal productivity on the net decrease in emission from beef production systems. A partial life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate GHG and NH(3) emissions from representative beef production systems in California that use various management technologies to enhance animal performance. The IFSM is a farm process model that simulates crop growth, feed production, animal performance, and manure production and handling through time to predict the performance, economics, and environmental impacts of production systems. The simulated beef production systems compared were 1) Angus-natural, with no use of growth-enhancing technologies, 2) Angus-implant, with ionophore and growth-promoting implant (e.g., estrogen/trenbolone acetate-based) application, 3) Angus-ß2-adrenergic agonists (BAA; e.g., zilpaterol), with ionophore, growth-promoting implant, and BAA application, 4) Holstein-implant, with growth implant and ionophore application, and 5) Holstein-BAA, with ionophore, growth implant, and BAA use. During the feedlot phase, use of BAA decreased NH(3) emission by 4 to 9 g/kg HCW, resulting in a 7% decrease in NH(3) loss from the full production system. Combined use of ionophore, growth implant, and BAA treatments decreased NH(3) emission from the full production system by 14 g/kg HCW, or 13%. The C footprint of beef was decreased by 2.2 kg carbon dioxide equivalent (CO(2)e)/kg HCW using all the growth-promoting technologies, and the Holstein beef footprint was decreased by 0.5 kg CO(2)e/kg HCW using BAA. Over the full production systems, these decreases were relatively small at 9% and 5% for Angus and Holstein beef, respectively. The growth-promoting technologies we evaluated are a cost-effective way to mitigate GHG and NH(3) emissions, but naturally managed cattle can bring a similar net return to Angus cattle treated with growth-promoting technologies when sold at an 8% greater premium price.

Carbon footprint and ammonia emissions of California beef production systems1

Beef production is a recognized source of greenhouse gas (GHG) and ammonia (NH(3)) emissions; however, little information exists on the net emissions from beef production systems. A partial life cycle assessment (LCA) was conducted using the Integrated Farm System Model (IFSM) to estimate GHG and NH(3) emissions from representative beef production systems in California. The IFSM is a process-level farm model that simulates crop growth, feed production and use, animal growth, and the return of manure nutrients back to the land to predict the environmental impacts and economics of production systems. Ammonia emissions are determined by summing the emissions from animal housing facilities, manure storage, field applied manure, and direct deposits of manure on pasture and rangeland. All important sources and sinks of methane, nitrous oxide, and carbon dioxide are predicted from primary and secondary emission sources. Primary sources include enteric fermentation, manure, cropland used in feed production, and fuel combustion. Secondary emissions occur during the production of resources used on the farm, which include fuel, electricity, machinery, fertilizer, and purchased animals. The carbon footprint is the net exchange of all GHG in carbon dioxide equivalent (CO(2)e) units per kg of HCW produced. Simulated beef production systems included cow-calf, stocker, and feedlot phases for the traditional British beef breeds and calf ranch and feedlot phases for Holstein steers. An evaluation of differing production management strategies resulted in ammonia emissions ranging from 98 ± 13 to 141 ± 27 g/kg HCW and carbon footprints of 10.7 ± 1.4 to 22.6 ± 2.0 kg CO(2)e/kg HCW. Within the British beef production cycle, the cow-calf phase was responsible for 69 to 72% of total GHG emissions with 17 to 27% from feedlot sources. Holstein steers that entered the beef production system as a by-product of dairy production had the lowest carbon footprint because the emissions associated with their mothers were primarily attributed to milk rather than meat production. For the Holstein system, the feedlot phase was responsible for 91% of the total GHG emission, while the calf-ranch phase was responsible for 7% with the remaining 2% from transportation. This simulation study provides baseline emissions data for California beef production systems and indicates where mitigation strategies can be most effective in reducing emissions.

Evaluation of tropically adapted straightbred and crossbred cattle: Postweaning BW gain and feed efficiency when finished in a temperate climate1,2

Beef cows in the subtropical USA must be adapted to the stressors of the environment, typically supplied by using Brahman (Br) breeding. Calves produced in the region, however, are usually grown and finished in more temperate regions, and have a perceived reputation for poor ADG and feed efficiency during finishing. Compromised fertility and carcass quality often associated with the Br have increased interest in tropically adapted Bos taurus breed types. The objective of this study was to evaluate 3 breeds [An = Angus (Bos taurus, temperate); Br (B. indicus, tropical); and Ro = Romosinuano (B. taurus, tropical)] and all possible crosses during various segments of post-weaning growth, and for feed efficiency during the finishing phase. Steer calves (n = 473) born over 3 yr were weaned in late September, backgrounded for at least 21 d (BKG), shipped 2,025 km to El Reno, OK, in October, fed a preconditioning diet for 28 d (RCV), grazed wheat (Triticum aestivum L.) pasture from November to May (WHT), finished on a conventional feedlot diet (FIN), and serially harvested after approximately 95, 125, and 150 d on feed. Body weight and ADG during each segment were tested using a mixed model that included calf age at weaning, year (Y), breed of sire (SB), breed of dam (DB), and interactions. In addition, winter treatment (continuous wheat or reduced grazing of wheat with supplement) was included for the wheat and feedlot phases. Sire within SB × SB [and pen (barn × year) for feedlot phase] were considered random. The SB × DB interaction was significant for all traits (P < 0.01) except exit velocity taken at weaning and ADG during FIN, but both traits were affected by 3-way interactions with Y or harvest group. Tropically-adapted purebred steers had greater (P < 0.01) ADG than AnAn through weaning and BKG in FL but the reverse was true during the RCV and WHT segments. Similar, but less pronounced results were noted for F(1) steers with 100% tropical influence compared with those with only 50%. Heterosis was numerically greater for most traits for An × Br (11 to 64%) compared with An × Ro and Br × Ro (3 to 42%), which were similar. In a subset of the steers (n = 261), G:F was not influenced by level of tropical breeding, but tropically adapted steers were more efficient (P < 0.05) by residual feed intake. No heterosis was evident. These data show that in temperate zones, winter is the period when productivity of tropically adapted cattle is compromised.

Performance of finishing beef cattle fed different diets containing whole-crop maize silage or sugarcane silage

The objective of the present study was to evaluate the performance of beef cattle in feedlots fed diets containing either whole-crop maize silage or sugarcane silage, and with different formulations. Five diets were evaluated: MSF - diet containing whole-crop maize silage, with fixed formulation during feedlot period; MSV- diet containing whole-crop maize silage, with variable formulation according to feedlot phase; SCSF - diet containing sugarcane silage with fixed formulation; SCSV- diet containing sugarcane silage, with variable formulation; SCSV/MSV- SCSV diet in initial half of fedlot and MSV diet in final half of feedlot period, respectively. It was used a complete random experimental design, with five treatments and three replicates (pens). It was used 285 steers at 36 months of age, with an initial body weight of 362.4 kg. Diets with whole-crop maize silage promoted greater intake of dry matter (10.5 kg and 2.4% BW) compared with diets containing sugarcane silage (10.1 kg and 2.3% BW). There was no effect of the silages on average daily gain (1.348 kg/animal/day) and live weight at slaughter (481.2 kg BW). SCSV/MSV diet promoted the worst feed conversion (8.0 kg DM/kg BW). Animals fed diets composed of whole-crop maize silage presented greater weight of hot carcass, of carcass yield and subcutaneous fat thickness (262.1 kg, 54.1% and 6.2 mm) compared with the animals fed sugarcane silage (252.5 kg, 52.7% and 4.8 mm). The use of sugarcane silage in diets for finishing beef cattle is feasible and the adjustment of formulation during confinement period does not influence performance of the animals. Replacement of sugarcane silage by whole-crop maize silage during the feeding period affects negatively feed conversion.

An economic case study of entire male grain-fed beef from a north-western Queensland production system

Assessing the differences in gross margins for a north-western Queensland beef-production system was undertaken using herd-budgeting software. The analysis reviewed the viability of producing beef for the domestic market from either a steer or bull production system. A hypothetical herd of 1200 breeders was created for the case study evaluation. An integrated beef production system from breeding to feedlot finishing was found to be less profitable for bull beef production than for steers at the current market prices. Although bull production was more profitable than steer production during the feedlot phase, the production of bulls in this phase failed to compensate for the earlier economic losses in the weaning phase of –AU$24.04 per adult equivalent for bulls. During the feedlot phase, bull production systems had lower break-even sale prices than did steer production systems. In reviewing two pricing scenarios for bulls, it was found that marketing bulls at the same price as steers was the most profitable production system. We conclude that the production of bull beef from a north-western Queensland production system can be profitable only if bulls can be sold without discount relative to steers.

Influence of Angus and Belgian Blue bulls mated to Hereford × Brahman cows on growth, carcass traits, and longissimus steak shear force1,2

Steers and heifers were generated from Angus (A) and Belgian Blue (BB) sires mated to Brahman x Hereford (B x H) F(1) cows to characterize their growth, carcass traits, and LM shear force. A total of 120 B x H cows purchased from 2 herds and 35 bulls (14 A and 21 BB) produced calves during the 5-yr project. After the stocker phase, a representative sample of A- and BB-sired heifers and steers were transported to the Iberia Research Station to be fed a high-concentrate diet. The remaining cattle were transported to a commercial feedlot facility. Each pen of cattle from the commercial feedlot was slaughtered when it was estimated that heifers and steers had 10 mm of fat or greater. The BB-sired calves were heavier at birth (P < 0.01) than the A-sired calves. During the feedlot phase, the A-sired calves gained more BW (P < 0.05) than the BB-sired calves. The BB-sired calves had heavier (P < 0.01) carcass weights than the A-sired calves. This was due to a combination of a heavier final BW and greater dressing percent. Because of their greater muscling and reduced (P < 0.01) fat, carcasses from BB-sired calves had greater yield (P < 0.01) compared with carcasses from A-sired calves. Carcasses from A-sired calves had a greater (P < 0.01) marbling score and greater (P < 0.01) USDA quality grade than carcasses from BB-sired calves. Tenderness, as measured by shear force of the steaks aged for 7 d, was similar for A- and BB-sired calves. However, steaks aged for 14 d from the A-sired calves had a reduced shear force (P < 0.01) compared with steaks from the BB-sired calves. Steer calves were heavier (P < 0.01) at birth and weaning, and had more total BW gain in the feedlot, which resulted in a heavier final BW and HCW compared with the heifers. Steer carcasses also had greater marbling scores and quality grades, whereas the heifer carcasses had larger LM area per 100 kg of carcass weight. In conclusion, the BB-sired calves had heavier carcass weights and greater cutability, whereas the A-sired calves had a greater degree of marbling and greater quality grade, and steaks from carcasses of A-sired calves were more tender as measured by shear force at 14 d.

Preweaning feed exposure and different feed delivery systems to enhance feed acceptance of sheep

Prior exposure of sheep to a novel feed has been shown to expedite the acceptance of that feed later in life. This study was designed to investigate the benefits of early social transmission of feed recognition for productivity and feeding behaviour of sheep in a feedlot. On a research farm near Armidale, Australia, 175 12-week-old Merino × Dorset lambs, together with their dams, were exposed to one of three preweaning treatments: (i) no exposure to feedlot pellets, (ii) offered feedlot pellets on the pasture, or (iii) offered feedlot pellets in feed troughs. The feedlot pellets were offered on two occasions at a rate of 200 g/dam, 1 month before weaning. After weaning, from 18 weeks of age, the lambs were observed for feeding behaviour and their growth during a 50-day feedlot finishing phase. Preweaning exposure to the pellets and the feed delivery system increased the rate of feed acceptance; however, there was no difference in the growth of lambs between the preweaning treatments at the end of the feedlot phase. The difference in percentage of lambs not eating between treatment groups was most pronounced during the first 2 days of the feeding period, with the differences gradually diminishing over the initial week of the feedlot phase. It is considered that differences in feedlot performance due to rate of acceptance of novel feeds are more likely under commercial conditions where pen densities are higher and feed ration transitions may be more rapid.

Outcomes of Synchronization and Timed Insemination Coupled with Retained Ownership in a Commercial Beef Cattle Operation

GnRH-based estrous synchronization programs have allowed for outstanding success in getting cows pregnant with timed insemination (TAI). This technology allows pregnancy rates approximating those of natural service to a single insemination. The system minimizes the requirement for estrus detection with its attendant error rates and high demand for labor. The overall method allows producers to select semen from superior sires with known progeny performance to meet the outcomes that are most economical for their operations. These outcomes include traits that provide for desirable parturition outcomes, high rates of growth and feed efficiency, and the production of carcasses that are sold for a premium because they receive desirable quality and yield grades.&#x0D; Retained ownership beef cattle production schemes are different from traditional beef cattle management approaches wherein calves change ownership from the cow/calf operation to the growing phase and finally to the finishing or feedlot phase. Retained ownership through the feedlot and then marketing finished cattle through a value-based program allows the cow/calf producer to be compensated for the actual value of the beef produced. Because most calf marketing schemes tend to value cattle based on industry averages, there is the potential to augment income through retained ownership if cattle have characteristics that result in performance and end-product that is superior to industry average.

Growth and carcass characteristics of Wagyu-sired steers at heavy market weights following slow or rapid growth to weaning

Two groups of Wagyu × Hereford steers grown slowly (slow preweaning group, n = 14, mean average daily gain = 631 g/day) or rapidly (rapid preweaning group, n = 15, mean average daily gain = 979 g/day) from birth to weaning were backgrounded on improved, temperate pasture to equivalent group liveweights (543 v. 548 kg, s.e. = 8.8 kg), then finished in a feedlot for 120 days. At weaning, the slow preweaning group was 79 kg lighter than the rapid preweaning group. They required an additional 43 days of backgrounding to reach the same feedlot entry weight as the rapid preweaning group. The slow preweaning group grew more rapidly during backgrounding (630 v. 549 g/day, s.e. = 13.7 g/day) but tended to grow more slowly during feedlotting (1798 v. 1982 g/day, s.e. = 74.9 g/day) than their rapid preweaning counterparts, with overall growth rates from weaning to feedlot exit not differing between the 2 groups (rapid 763 g/day v. slow 772 g/day, s.e. = 17.5 g/day). At slaughter, following the feedlot phase, carcass weights of the 2 groups did not differ significantly (rapid 430 kg v. slow 417 kg, s.e. = 7.2 kg). There was a tendency for the steers grown slowly to weaning to have a higher dressing percentage (57.6 v. 56.6%, s.e. = 0.33%), but there were no significant differences in carcass compositional characteristics between the 2 groups. The slow preweaning steers did have a greater eye muscle area than the rapid preweaning steers (106.6 v. 98.9 cm2, s.e. = 1.87) when carcass weight was used as a covariate. These findings demonstrate that cattle grown slowly to weaning have similar composition at slaughter as those grown rapidly during the same period when backgrounded on pasture to the same feedlot entry weight. Furthermore, marbling was not adversely affected by slow growth to weaning.

Influence of Live Weight Gain During the Winter Grazing Period on Subsequent Grazing and Feedlot Performance

Crossbred steer (n = 297) and heifer (n = 125) calves were used in three experiments to determine the impact of restrictive ADG during the winter grazing period on subsequent BW gains. Calves were born in the spring, weaned in the fall, and transported from Northwest Arkansas (360 km; Experiments 1 and 2) or Southwest Texas (880 km; Experiment 3) to Central Oklahoma for grazing and finishing. Upon arrival, calves were assigned to one of the following treatments: 1) grazing winter wheat pasture, 2) grazing dormant tallgrass native prairie plus supplemental CP, or 3) limit fed a high-energy diet (Experiment 3 only). In March, winter stocker treatments (121 d) were ended, and calves grazed cool season grasses (76 d) until June when the feedlot phase began. In the feedlot phase, calves were either assigned to a conventional total confinement finishing system or to a warm-season grass pasture managed under intensive early stocking (9.9 calves/ha) followed by ad libitum access to a high-energy diet. In Experiments 1 and 2, calves on dormant native pasture gained less (P<0.01) BW during the winter than calves on wheat pasture (15.8 vs 97.2kg). Restricting winter ADG did not affect BW gains during the spring grazing period, but did increase (P<0.01) feedlot ADG by 23.5%. Performance of calves used in Experiment 3 was similar to that observed for Experiments 1 and 2. Calves finished on pasture had greater (P<0.01) net returns than calves finished in confinement (-$34.45 vs -$51.62 per calf). Restricting winter ADG of stocker calves increased ADG and feed efficiency during the feedlot phase. A production system that includes intensive early stocking of warm-season grass pastures followed by ad libitum access to a high-energy diet can be used to produce finished beef carcasses more economically than under total confinement.

Comparisons of economic values with and without risk for livestock trait improvement

This paper investigates the effect of incorporating risk in the derivation of economic values for livestock trait improvement. Two ways of obtaining economic values were contrasted, without consideration of risk (traditional economic values) and with incorporation of variance of profit and risk attitudes of livestock producers (risk-rated economic values). Traditional economic values were derived using a profit model, whereas risk-rated economic values were derived using a risk-rated profit model. A simplified example was considered for selection for the feedlot phase of beef production. One output trait (average daily gain) and one input trait (daily dry matter intake) and one management variable were considered. Risk was defined as the variance of profit and producer’s risk attitude. Traditional economic values and risk-rated economic values differed in both absolute and relative terms. When relative economic values were considered, differences between traditional economic values and risk-rated economic values increased with risk premium. Differences were greater without optimisation of management than with optimisation, although in the example used there was limited impact on expected responses to selection in the component traits. Including risk preferences in breeding goals affects the cost–benefit analysis of breeding programs and might affect directions for selection.

Effect of age at feedlot entry on performance and carcass characteristics of bulls and steers1

Seventy Angus × Simmental calves (BW = 166.3 ± 4.2 kg) were used in a 3 × 2 factorial arrangement to determine the effect of age at feedlot entry and castration on growth, performance, and carcass characteristics. At 82 d of age, steers were castrated. Calves were placed in the feedlot at 111 (early-weaned), 202, or 371 (yearling) d of age. Steers were implanted with Synovex-S followed 93 d later with Revalor-S. Calves were harvested on an individual basis when fat thickness was estimated to be 1.27 cm. During the feedlot phase, yearlings gained faster (P < 0.01) than calves placed in the feedlot at 202 or 111 d of age (1.88, 1.68, and 1.62 kg/d, respectively); however, from 111 d of age until harvest, ADG was greatest for early-weaned calves, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for yearlings (1.62, 1.47, and 1.21 kg/d, respectively; P < 0.01). Early-weaned calves spent the most days in the feedlot, followed by calves placed in the feedlot at 202 d of age; yearlings spent the fewest days in the feedlot (221, 190, and 163 d, respectively; P < 0.01). Total DMI when in the feedlot was similar (P = 0.22) among age groups; however, daily DMI was lowest for early-weaned calves, intermediate for calves placed in the feedlot at 202 d of age, and the highest for yearlings (7.1, 8.1, 10.5 kg/d, respectively; P < 0.01). Early-weaned calves were the most efficient, followed by calves placed in the feedlot at 202 d of age; yearlings were the least efficient (227, 207, 180 g gain/kg feed, respectively; P < 0.01). Weight at harvest (682, 582, 517 kg, respectively; P < 0.01) and hot carcass weight (413, 358, 314 kg, respectively; P < 0.01) were greatest for yearlings, intermediate for cattle placed in the feedlot at 202 d of age, and lowest for early-weaned calves. Early-weaned calves had the smallest longissimus area, followed by calves placed in the feedlot at 202 d of age; yearlings had the largest longissimus area (77, 86, 88 cm2, respectively; P < 0.01). Calves placed in the feedlot at 111 and 202 d of age had lower yield grades (3.2, 3.1, 3.5, respectively; P < 0.04), and produced fewer select carcasses than yearlings (25, 13, 48%, respectively; P < 0.01). Bulls and implanted steers both had an ADG of 1.7 kg/d when in the feedlot; however, bulls had a greater (P < 0.09) hot carcass weight (370 vs 354 kg) and a larger (P < 0.01) longissimus area (85.8 vs 81.3 cm2) than steers. Earlier feedlot placement resulted in greater quality grades but lower carcass weights.

Evaluation of Ralgro® on pasture and subsequent feedlot performance and carcass merit of Mexican crossbred steers (2001)

A pasture/feedlot field study was conducted to evaluate the effects of a single Ralgro implant during the stocker phase on steer grazing performance and subsequent feedlot performance and carcass merit. A total of 2,764 steers of Mexican origin averaging 449 lb were assembled in Texas and shipped to Kansas, where they grazed on three intensively-early-stocked Flint Hills pastures. At initial processing, the steers were individually weighed and randomly assigned to either a non-implanted control group or a Ralgro implant group. Ralgro steers gained more (23 lb; P<0.01) than controls during the 82to 93-day grazing phase. Following the grazing phase, all steers were shipped to a commercial feedlot in southwestern Kansas where steers from each pasture were individually weighed and given a single Component E-S implant. Immediately after processing, steers from each pasture were sorted into either a lightor heavy-weight pen, regardless of pasture implant treatment, resulting in six feedlot pens. Days on feed ranged from 127 to 197. Control steers gained faster (P<0.01) during the feedlot phase; however, Ralgro steers had higher cumulative weight gains across the combined pasture and feedlot phases (P<0.01) and averaged three fewer days on feed (P<0.05). There were no significant differences for marbling, fat thickness, ribeye area, KPH fat, or yield grade. Ralgro steers had lower (P<0.05) quality grades because of a higher incidence (P<0.001) of steers with B and C carcass maturities.

Genotype x environment interactions for postweaning performance in crossbred calves grazing winter wheat pasture or dormant native prairie.

Data from 403 calves from Angus, Brahman, and reciprocal-cross cows sired by Polled Hereford bulls were used to evaluate the impact of postweaning backgrounding forages on postweaning BW, gains, and carcass traits. Calves were born (spring of 1991 through 1994) and reared on either endophyte-infected tall fescue or common bermudagrass pastures. After weaning, calves were transported 360 km to the Grazinglands Research Laboratory, west of El Reno, OK, and, within breed and preweaning forage, were assigned to one of the following winter stocker treatments: 1) winter wheat pasture or 2) dormant native prairie plus supplemental CP. In March, winter stocker treatments were ended and calves were grazed as a single group on cool-season grasses until early July (1992, 1993, and 1994) or late May (1995), when the feedlot phase began. In the feedlot, calves were fed a high concentrate diet for an average of 120 d until a backfat thickness of > 10 mm was reached. Calves were shipped in truck load lots to Amarillo, TX (350 km), for processing and collection of carcass data. Averaged over calf breed group, calves wintered on wheat pasture gained faster (P < 0.01) during the stocker phase (0.71 vs 0.43 kg); had heavier (P < 0.01) final feedlot weights (535 vs 512 kg); lower feedlot (P < 0.01) ADG (1.37 vs 1.53 kg); heavier (P < 0.01) carcass weights (337 vs 315 kg); larger (P < 0.01) longissimus muscle (84.9 vs 81.8 cm2); higher percentage (P < 0.01) of kidney, heart, and pelvic fat (2.32 vs 2.26); and higher (P < 0.01) dressing percentage (62.2 vs 61.3) than calves backgrounded on native prairie. Maternal heterosis for stocker ADG was evident in calves backgrounded on native prairie but not on winter wheat (P < 0.10), but the two environments were similar in maternal heterosis for feedlot ADG and carcass traits. Calves wintered on native prairie were restricted in growth and expressed compensatory gain during the feedlot phase but not during the spring stocker phase. Dormant native grasses can be used to winter stocker calves excess to the winter wheat pasture needs, but ownership of these calves would have to be retained through the feedlot phase to realize any advantage of built-in compensatory gain. Finally, these data suggest that expression of maternal heterosis for weight gain is more likely in calves backgrounded on native prairie than in calves grazed on winter wheat.