Biological and economic performance of early-weaned Angus steers.

Over 2 yr, 45 Angus-sired steer offspring of Angus and Angus crossbred females were used to determine the effects of early weaning on feedlot performance, carcass characteristics, and economic return to the cow-calf enterprise. Steers were assigned by birth date to one of two weaning treatments: 1) weaned at an average age of 100 d (early weaned) or 2) weaned at an average age of 200 d (normally weaned). Within 36 d of weaning, steers were given ad libitum access to a high-concentrate diet (90% dry, wholeshelled corn). Steers were harvested when 12th-rib fat thickness averaged 1.27 cm within treatment as estimated by ultrasound. Carcass measurements were taken 48 h postmortem and rib steak tenderness was determined at 14 d postmortem by Warner-Bratzler shear force. Early-weaned steers had greater ADG from time of early weaning to normal weaning than suckling normally weaned steers (1.27 vs. 0.86 kg/d, respectively; P < 0.001). However, early-weaned steers tended to have lower ADG for the entire finishing period than did normally weaned steers (1.33 vs. 1.39 kg/d, respectively; P = 0.08). Compared with normally weaned steers, early-weaned steers had lower daily DMI (7.40 vs. 5.95 kg/d, respectively; P < 0.001) and lower total DMI for the finishing period (1,618 vs 1,537 kg, respectively; P < 0.05). Early-weaned steers had greater gain:feed for the finishing period than normally weaned steers (0.223 vs 0.189, respectively; P < 0.001). Carcass weights were lighter for early-weaned steers than for normally weaned steers (277.9 vs. 311.2 kg, respectively; P < 0.001). There was no difference in yield grade (3.1 vs. 3.2; P < 0.10) between treatments. All carcasses graded Low-Choice or greater, and there was no difference in the percentage of carcasses grading Mid-Choice or greater (94.5 vs 83.9% for early- and normally-weaned, respectively; P > 0.10). Warner-Bratzler shear force values were similar between treatments. Early-weaned steers had a lower cost of gain than normally weaned steers ($ 0.82 vs. 0.91/kg, respectively; P < 0.001). However, due to lighter carcass weights, early-weaned steers generated less return to the cow-calf enterprise than normally weaned steers ($ 380.89 vs 480.08/steer; P < 0.001). The early weaning of steers at 100 d of age decreased total DMI, improved gain:feed, and lowered the cost of gain; however, return to the cow-calf enterprise was decreased due to lighter carcass weights.     

Effect of early weaning on the performance of three-year-old,first-calf beef heifers and calves reared in the subtropics

The objective of this study was to investigate the effectiveness of early weaning fall-born calves on heifer and calf performance in Florida. Over two consecutive years, 3-yr-old Braford and Brahman x Angus first-calf heifers were assigned randomly to one of two treatments; early-weaned (EW, n = 20 and 30 for yr 1 and 2, respectively) and normal-weaned (NW, n = 20 and 38 for yr 1 and 2, respectively). Calves were EW on January 23 and 3 for yr 1 and 2, respectively. Following EW, all first-calf heifers were returned to bahiagrass (Paspalum notatum) pastures with the mature cowherd. Early-weaned calves were maintained on annual ryegrass (Lolium multiflorum) pastures at 8.2 and 10.7 calves/ha for yr 1 and 2, respectively, and were provided supplemental grain mixture (14% CP) at 1.0% of BW daily. Normal-weaned calves remained with their dams in the mature cowherd on bahiagrass. Final calf BW was collected on April 17 (d 84) and April 24 (d 111) for yr 1 and 2, respectively. Early-weaned calves had a greater (P < 0.001) ADG (0.17 kg/d) in yr 1, but a lower (P < 0.001) ADG (-0.24 kg/d) in yr 2 compared with NW calves. Early weaning resulted in heavier first-calf heifers with greater BCS at the time of normal weaning (August 1; 491 vs. 452 kg, with BCS = 6.34 vs. 4.75 for EW and NW heifers, respectively; SEM = 5.0 and 0.07). Heifers with EW calves had a higher (P < 0.07) pregnancy rate during both years than normal-weaned heifers (89.5 vs. 50.0 and 96.7 vs. 80.0% pregnant during yr 1 and 2, respectively). Early-weaned, first-calf heifers also had a lower (P < 0.05) calving interval in yr 2 (384 vs. 404 d; SEM = 6.0). These data suggest that EW will improve body condition of first-calf heifers resulting in an increased pregnancy rate. Early-weaned calves maintained on winter ryegrass provide producers with the ability to optimize early-weaned calf performance, while capitalizing on low cost of gain and favorable spring markets.     

Effects of weaning age and diet on growth and carcass characteristics in steers

Two experiments were conducted to determine the effects of diet on growth of steers weaned at approximately 100 vs 205 d of age. In Exp. 1, a 2 x 2 x 2 factorial experiment was conducted using 78 Angus crossbred cow-calf pairs. The factors examined were age at weaning (early, at 103+/-3 d [EW] vs normal, at 203+/-3 d [NW]), feeding strategy (ad libitum vs postweaning programmed intake), and dietary CP concentration (100 vs 120% of NRC [1984] recommended levels). Early-weaned calves had a greater (P < .001) ADG than NW calves from 103 to 203 d and reached market weight at 385 d vs 418 d for NW calves (P < .001). Likewise, steers offered feed for ad libitum consumption reached market weight at 394 d, compared with 409 d for programmed-intake steers (P < .05). In Exp. 2, 64 Angus crossbred steers were either weaned at 93+/-3 d and fed one of four diets, weaned at 210+/-3 d without access to creep feed, or weaned at 210+/-3 d with access to creep feed for 60 d prior to weaning. Early-weaned calves were heavier (P < .01) than NW calves at 210 d if fed either 100 or 90% concentrate diets, and they had greater (P < .001) backfat thickness at 210 d but no difference (P > .10) in longissimus muscle area compared to EW calves fed a 60% concentrate diet. At slaughter, 80 to 100% of steers on all treatments graded low Choice or higher. Feeding high-concentrate diets to EW beef calves accelerated growth rate and fat deposition early in the feeding period and may be a way to provide young cattle for a high-quality beef market.     

Production systems comparing early weaning to normal weaning with or without creep feeding for beef steers

A 2-yr study was conducted to determine the effects of three weaning management systems on cow and steer performance. Cow-calf pairs were randomly assigned to one of three treatments, in which the steer calves were 1) early-weaned (yr 1, 177 +/- 9 d; yr 2, 158 +/- 21 d of age) and placed on a finishing diet (EW), 2) supplemented with grain for 55 d on pasture (yr 1, 177 to 231 d; yr 2, 158 to 213 d of age) while nursing their dams and then placed on a finishing diet (NWC), and 3) on pasture for 55 d while nursing their dams (yr 1, 177 to 231 d; yr 2, 158 to 213 d of age) and then placed on a finishing diet (NW). In yr 2, potential breed differences were evaluated using steers of three breed types: 1) Angus x Hereford (BRI); 2) Angus x Simmental (CON); and 3) Angus x Wagyu (WAG). In yr 1, EW steers gained 100% faster (P = .0001) than the average of NWC and NW steers, and NWC steers gained 32% faster (P = .02) than NW steers before weaning. In the feedlot, EW steers had lower intakes (7.70 vs 8.16 kg/d, P = .008) and better feed conversions (.170 vs .153, P = .002) than the average of NWC and NW steers. Marbling score was improved for EW steers compared with the average of NWC and NW steers (P = .003). In yr 2, EW steers had higher gains (P = .0006) during the entire study than the average of NWC and NW steers, and NWC steers had higher gains (P = .003) than NW steers. The EW steers had lower intakes (7.29 vs 7.68 kg/d, P = .0008) and better feed conversions (.160 vs .141, P = .0001) than the average of NWC and NW steers. The CON steers were heavier at slaughter than BRI steers (P = .01), and BRI steers were heavier than WAG steers (P =.0004). Early weaning improved the percentage of steers grading Average Choice or higher by 40%. The percentage of BRI steers grading Choice or greater was 21% higher and percentage of steers grading Average Choice or greater was 33% higher than CON. Cows with EW steers had higher ADG than cows with NW steers (.38 vs -.17 kg/d, P = .0001) before weaning. Cows with EW steers gained in body condition score (.23 vs .00, P = .04), and cows with NW steers did not change. Early weaning improved feed efficiency and quality grades of beef steers.     

The effect of early weaning on feedlot performance and measures of stress in beef calves

Forty crossbred steers (Brahman x English) were categorized into two groups: 1) early weaned (EW; n = 20); and 2) normal weaned (NW; n = 20). Calves were 89 and 300 d of age at the time of EW and NW, respectively; SEM = 4.4. Early-weaned calves were kept on-site (University of Florida, Ona), provided supplement (1% of BW), and grazed on annual and perennial pastures until NW. At the time of normal weaning, all calves were loaded on a commercial livestock trailer and transported to the North Carolina State University Research Feedlot in Butner (approximately 1,200 km). Upon arrival, calves were stratified by BW and randomly allotted to four pens per weaning age treatment. Individual calf BW and blood samples were collected at the time of normal weaning, on arrival at the feedlot (d 1; 24 h following weaning), and on d 3, 7, 14, 21, and 28 of the receiving period. Individual BW was collected at the start and end of the growing and finishing periods, and feed intake by pen was measured daily. As an estimate of stress during the receiving period, plasma was collected and analyzed for the acute-phase proteins, haptoglobin and ceruloplasmin. Early-weaned calves were lighter (P = 0.03) at normal weaning than NW calves (221 vs. 269 kg; SEM = 10.6). By d 28, EW calves tended (P = 0.12) to be lighter than NW calves (242 vs. 282 kg, respectively). Gain:feed was improved for EW compared with NW calves during both the receiving (G:F = 0.157 vs. 0.081) and growing (0.159 vs. 0.136) periods. There tended (P < 0.10) to be weaning age x day interactions for each acute-phase protein. Ceruloplasmin concentrations increased in NW, but not EW calves, and peaked on d 7 (27.6 and 34.2 mg/100 mL for EW and NW calves, respectively; P < 0.05). Haptoglobin concentrations increased in both groups and were greatest (P < 0.05) in NW calves on d 3 (7.63 vs. 14.86 mg of haptoglobin/hemoglobin complexing/100 mL). No differences in ADG or G:F were detected during the finishing phase; however, overall G:F was improved (P = 0.03) for EW vs. NW calves (0.155 vs. 0.136). Carcass measures, including backfat thickness, USDA yield grade, marbling score, and LM area, did not differ between treatments. These data imply that EW calves, which are maintained onsite before shipping, may be more tolerant to the stressors associated with transportation and feed yard entry. Early weaned calves, managed within the system described in this study, may have improved G:F.     

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

Seventy Angus x Simmental calves (BW = 166.3 +/- 4.2 kg) were used in a 3 x 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 feed-lot 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.     

Effect of source and amount of energy and rate of growth in the growing phase on performance and carcass characteristics of early- and normal-weaned steers

One hundred eighty-four Angus x Simmental steers (initial BW 161.7 +/- 3.4 kg) were used to determine whether different sources and amounts of energy in the growing phase could extend the growth curve and maintain high amounts of intramuscular fat deposition in early-weaned steers. Steers were allotted by source, age, and BW to one of four growing-phase (119 to 259 d of age) regimens. For three regimens, steers were weaned at 119 d of age and either 1) fed (DM basis) a 50% grain diet ad libitum (ALC); 2) limit-fed a 70% grain diet to achieve a gain of 0.8 kg/d from 119 to 192 d of age, and 1.2 kg/d from 193 to 259 d of age (LFC); or 3) fed a 60% haylage diet ad libitum from 119 to 192 d of age, and a 25% haylage diet ad libitum from 193 to 259 d of age (ALF). For the fourth regimen, steers were normal-weaned at 204 d of age and fed a silage diet from 205 to 259 d of age (NW). From 260 d of age to slaughter, all steers consumed a 70% grain (DM basis) diet. Limit-fed and ALF steers spent the most, and NW the least amount of time (P < 0.01) in the feedlot to achieve a target fat depth of 1.27 cm. Ad libitum-fed steers were the youngest (331 d), and NW the oldest (383 d) at slaughter (P < 0.01). Overall ADG was greatest for ALC and least for NW steers (P < 0.01). Overall, ALF steers consumed the most DM (P < 0.01). While in the feedlot, LFC and ALC steers were more efficient in converting feed to BW gain (P < 0.01) than ALF and NW steers. Normal-weaned had the least and ALC the greatest (P < 0.01) fat depth at 260 d of age. Consequently, NW steers produced the heaviest, and ALC the lightest (P < 0.01) carcasses at slaughter. Normal-weaned steers had the largest, and ALC and LFC steers had the smallest longissimus muscle area (P < 0.06). Growing phase dietary treatments did not affect (P > 0.20) yield grade. Marbling score did not differ (P > 0.35), but laboratory analysis revealed that ALC steers had the lowest percentage of fat (P < 0.02) in the longissimus muscle. Shear force was greatest (P < 0.08) for steaks from ALC and LFC steers, and least for steaks from ALF and NW steers. Feeding steers the ALC diet from 119 to 260 d of age hastened physiological maturity, decreased marbling scores, and decreased muscle tenderness compared with forage feeding (ALF, NW). Limit-feeding a high-grain diet also hastened physiological maturity and decreased muscle tenderness but did not decrease marbling scores. Source and amount of energy affected partitioning of fat deposition.     

Growth rate, body composition, and meat tenderness in early vs. traditionally weaned beef calves

One hundred forty spring-born Angus x Gelbvieh and purebred Angus steers were selected for study as early weaned (EW; average age at weaning = 90 +/- 30 d) or traditionally weaned (TW; average age at weaning = 174 +/- 37 d) steers that were non-implanted or implanted (Synovex-S, Fort Dodge Animal Health, Overland Park, KS). Initially, steers were sorted by age, sire, and farm, and then allotted randomly in a 2 x 2 factorial arrangement of treatments of EW implanted (EWI), EW nonimplanted (EWN), TW implanted (TWI), or TW nonimplanted (TWN). Ultrasound measurements (US) of LM area (LMA), 12th rib fat thickness (US-BF), and marbling (US-M) were collected every 28 d during the time that steers were on feed. At 202 d of age, EW calves had larger US-LMA, US-BF, and BW than TW calves (37.9 vs. 32.3 cm2, 0.38 vs. 0.26 cm, and 271.6 vs. 218.9 kg, respectively; P < 0.001). At slaughter, EW calves had heavier HCW (290.4 vs. 279.7 kg, respectively; P < 0.05) and greater USDA marbling scores (51.25 vs. 46.26, respectively; P < 0.05) than TW calves; more EW steers graded USDA Choice or greater (P = 0.05). However, no differences were detected in BW (P = 0.15), LMA (P = 0.39), BF (P = 0.45), or liver abscess scores (P = 0.41). Twenty-four implanted steers were selected from the original group of 140 and sorted into two slaughter groups of 12. Twelve implanted steers from each weaning group, matched in slaughter BW but differing in age, were subsampled at slaughter to assess the effect of weaning age and chronological age on muscle tenderness. Younger animals had lower Warner-Bratzler shear force values (P < 0.001) than older calves after 14 d of postmortem aging; however, no differences were found in tenderness after 21 d of aging. Furthermore, there was greater variance (P < 0.001) in Warner-Bratzler shear force values among younger, EW steers vs. older, TW steers. These data provide evidence that early weaning of beef calves may be used as a tool to more effectively manage the cow-calf production system without compromising the quality of the offspring.     

Age of calf at weaning of spring-calving beef cows and the effect on cow and calf performance and production economics

Over a 5-yr period, spring-calving cows were used in a carry-over design experiment to evaluate effects of calf age at weaning on cow and calf performance and production economics. Weaning management groups were early (n = 60, calf age 150 d, EW), traditional (n = 60, calf age 210 d, NW), and late (n = 60, calf age 270 d, LW). Cow body condition score (BCS) and weights at the last weaning date were different (P < .05) for EW (5.8, 583 kg), NW (5.5, 560 kg), and LW (5.2, 541 kg) management groups. Pregnancy rates among groups were similar. Days on feed for groups differed (P = .001) and was 247 for EW, 204 for NW, and 164 d for LW steers. Average daily gain in the feedlot differed (P = .01) among groups and averaged 1.5 kg for LW, 1.4 kg for NW, and 1.3 kg for EW steers. Dry matter intake while steers were in the feedlot was greater (P = .001) for LW than for NW and EW calves. Hot carcass weight was greater (P = .01) for EW (328 kg) and NW (332 kg) calves than for LW (321 kg) steers, and fat depth was greater (P = .05) for EW and NW steers than for LW steers. When carcass data for the NW and LW steers were adjusted to the fat depth of EW steers, carcass characteristics among groups were similar. Net income per steer at slaughter for the feedlot phase was greater (P < .001) for the EW ($75.36) and NW ($62.16) steers than for the LW ($10.09) steers. Again, when carcass data for the NW and LW steers were adjusted to the same fat depth of the EW steers, net income differences among groups were reduced. Replacement heifers were developed in a drylot and costs were higher (P < .001) for the EW than for NW and LW heifers. Annual cow costs were greater (P < .10) for the LW ($443.45) than for the EW ($410.09) and NW ($421.35) groups. Break-even for each system on a steer financial basis was not different between the NW and LW groups, and both the NW and LW groups had lower (P = .08) break-evens than the EW group. Age of the calf at weaning affects cow weight and BCS. Net income in each system is influenced by cow costs, month of the year that steer calves are purchased into the feedlot and finished steers are sold, month of the year cull cows are marketed, and replacement heifer development costs.     

Effects of repetitive use of hormonal implants on beef carcass quality,tenderness, and consumer ratings of beef palatability

Effects of repetitive use of anabolic implants on beef carcass quality, tenderness, and consumer ratings for palatability were investigated using crossbred steer calves (n = 550). Steers from five ranches were randomly allocated to one of 10 different lifetime implant strategies or to a nonimplanted control group. Cattle were implanted at some or all of five phases of production (branding, weaning, backgrounding, feedlot entry, or reimplant time). Carcasses from the control group had higher (P < 0.05) marbling scores than carcasses from steers in all other treatment groups. Implanting steers at branding, weaning, or backgrounding vs. not implanting steers at these production stages did not affect (P > 0.05) marbling scores. Steers implanted twice during their lifetime produced carcasses with higher (P < 0.05) marbling scores than did steers receiving a total of four or five implants. Steaks obtained from carcasses in the control group had lower (P < 0.05) shear force values and were rated by consumers as more desirable (P < 0.05) for tenderness like/dislike than steaks obtained from carcasses in all other treatment groups. Implanting steers at branding or weaning production stages did not affect (P > 0.05) steak shear force values, consumer ratings for like/dislike of steak tenderness, or percentage of consumers rating overall eating quality of steaks as satisfactory. Implanting steers at backgrounding vs. not implanting steers at this production stage increased (P < 0.05) steak shear force values, but did not influence (P > 0.05) consumer ratings for like/dislike of steak tenderness or percentage of consumers rating overall eating quality of steaks as satisfactory. Steaks from nonimplanted steers were rated as more desirable (P < 0.05) for overall eating quality than steaks from steers implanted two, three, four, or five times. Use of implants increased (P < 0.05) average daily gain by 11.8 to 20.5% from weaning to harvest compared with nonimplanted controls. Implant strategies increased (P < 0.05) hot carcass weight of steers by 8.9 to 13.8% compared with the control group. Use of implants also increased (P < 0.05) longissimus muscle area and decreased (P < 0.05) estimated percentages of kidney/pelvic/heart fat, but did not affect (P > 0.05) dressing percentage or adjusted fat thickness. Our findings suggest that beef quality, palatability, and production characteristics are influenced by lifetime implant protocols.     

Effects of preshipping management on measures of stress and performance of beef steers during feedlot receiving

Over 2 yr, a total of 96 steers (approximately 7 mo of age) were allocated to 1 of 4 weaning management strategies: 1) control: weaned on the day of shipping; 2) creep-fed: allowed free-choice access to concentrate before weaning and shipping; 3) preweaned: weaned and provided supplemental concentrate on pasture before shipping; and 4) early-weaned: weaned at 70 to 90 d of age and kept on pasture. On the day of shipping, steers were loaded together onto a commercial livestock trailer and transported 1,600 km over 24 h before being received into the feedlot. At the feedlot, steers were penned by treatment (4 pens/treatment) and provided access to free-choice hay and concentrate in separate feeding spaces. Samples of blood were collected on d 0, 1, 4, 8, 15, 22, and 29 relative to shipping. Steer performance was assessed over the receiving period, including DMI of hay and concentrate, ADG, and G:F. Predetermined contrasts included control vs. early-weaned, creep-fed vs. preweaned, and control vs. creep-fed and preweaned. Overall ADG was greater (P < 0.01) for early-weaned vs. control steers (1.39 vs. 0.88 kg). In wk 1, early-weaned steers consumed more concentrate and less hay compared with control steers (P < 0.03), and preweaned steers consumed more concentrate (P < 0.01) but a similar amount of hay (P = 0.75) compared with creep-fed steers. Average DMI was greater for preweaned compared with creep-fed steers (2.84 vs. 2.50% of BW; P = 0.01) and tended to be greater for early-weaned compared with control steers (2.76 vs. 2.50% of BW; P = 0.06). Feed efficiency of early-weaned steers was greater than that of control steers (G:F = 0.17 vs. 0.12; P < 0.01) but similar for preweaned compared with creep-fed steers (P = 0.72). Plasma ceruloplasmin concentrations were less (P < 0.05) in control vs. early-weaned steers on d 0, but increased sharply after shipping and were greater in control vs. early-weaned steers on d 15 and 22 (P < 0.05). Creep-fed steers also experienced greater (P < 0.05) plasma ceruloplasmin concentrations than preweaned steers on d 29. These data suggest that early-weaned steers have improved performance in the feedlot compared with steers weaned directly before transport and feedlot entry. Differences in preshipping management appear to significantly affect measures of the acute phase protein response in steers.     

Effect of muscle type, sire breed, and time of weaning on fatty acid composition of finishing steers

Thirty-three steer calves were used to determine the effect of sire breed (Angus or Charolais), time of weaning [normal weaned at approximately 210 d of age (NW) or late weaned at approximately 300 d of age (LW)], and muscle type [LM and semitendinosus muscle (STN)] on fatty acid composition. The whole plot consisted of a 2 (sire breed) × 2 (time of weaning) treatment arrangement, and the subplot treatment was muscle type. Body weights were recorded at 28-d intervals to determine animal performance. Muscle biopsies were collected on d 127 and 128 of finishing. All calves were slaughtered on d 138, and carcass data were collected. Angus-sired steers had lighter initial BW (271 vs. 298 kg; P = 0.02), and LW steers were heavier (351 vs. 323 kg; P = 0.03) on d 28, but no other differences in BW were noted. Charolais-sired steers had larger LM area (P = 0.03), reduced yield grades (P = 0.01), less 12th-rib fat (P < 0.01), and less marbling (P < 0.01) than Angus-sired steers. Carcass measures overall indicate Angus-sired steers were fatter. Hot carcass weight was heavier (348 vs. 324 kg; P = 0.04) in LW steers than NW steers. No other differences (P > 0.05) were observed for feedlot performance or carcass characteristics. Total lipids were extracted from muscle biopsies, derivatized to their methyl esters, and analyzed using gas chromatography. The LM had greater SFA (43.94 vs. 35.76%; P < 0.01) and decreased unsaturated fatty acids (UFA; 56.90 vs. 66.19%; P < 0.01) compared with the STN. Percent total MUFA was greater in STN than LM (51.05 vs. 41.98%; P < 0.01). Total SFA, UFA, and MUFA did not differ due to sire breed or time of weaning. Total PUFA differed (P = 0.04) due to a sire breed × time of weaning interaction but did not differ due to muscle type, with greater PUFA in NW Charolais than any other sire breed × time of weaning combination. Observed changes in percent MUFA may be a result of greater Δ(9)-desaturase activity. The calculated desaturase index suggests STN has a greater Δ(9)-desaturase activity than LM, but no differences (P > 0.05) between sire breed or time of weaning were observed. These results indicate that sire breed, time of weaning, and muscle type all affect fatty acid composition in beef. This information provides insight into factors for manipulation of beef fatty acids. More research is needed to identify beef cuts based on fatty acid profile and healthfulness.     

Effect of an accelerated finishing program on performance,carcass characteristics,and circulating insulin-like growth factor I concentration of early-weaned bulls and steers

Sixty-three Angus x Simmental calves were allotted to a bull or a steer group based on sire, birth date, and birth weight to determine effects of castration status on performance, carcass characteristics, and circulating insulin-like growth factor I (IGF-I) concentrations in early-weaned cattle. At 75 d of age, calves in the steer group were castrated. Calves were not creep-fed prior to weaning. All calves were weaned and weighed at an average age of 115 d and transported by truck to the OARDC feedlot in Wooster, OH. Performance and carcass characteristics were measured in three phases. Phase 1 was from 115 to 200 d of age, phase 2 was from 201 to 277 d of age, and phase 3 was from 278 d of age to slaughter. Before implantation, four bulls and four steers were selected for serial slaughter and carcass evaluation. Steers were implanted with Synovex-C at 130 d of age and with Revalor-S at 200 and 277 d of age. Serum samples were collected from all calves on the day of implantation, 28 and 42 d after implantation, and at slaughter and analyzed for circulating IGF-I concentration. Bulls gained 9.7% faster (1.75 vs 1.60 kg/d; P < 0.01), consumed 25 kg more DM (521 vs 496 kg; P = 0.11), and were 3.3% more efficient (282 vs 273 g/kg, P < 0.10) than steers in phase 1. However, steers gained 10.5% faster (1.62 vs 1.46 kg/d; P < 0.02), consumed similar amounts of DM, and were 6.5% more efficient than bulls (214 vs 201 g/kg; P < 0.06) in phase 2. Overall gains and efficiency were similar between bulls and steers; however, bulls consumed 140 kg more DM (P < 0.05), were 27 kg heavier (P < 0.05), and had to stay in the feedlot 18 more days (P < 0.05) than steers to achieve a similar amount of fat thickness. Implanted steers had greater concentrations of circulating IGF-I than bulls (P < 0.01), and the pattern of IGF-I concentration over time was affected by castration status (castration status x time interaction; P < 0.01). Synovex-C had a lower impact on circulating IGF-I concentration (implant effect, P < 0.01) than either Revalor-S implant. Eighty-five percent of both bulls and steers had marbling scores sufficient to grade low Choice or better. Bulls achieved their target fat thickness later, increased muscle growth, and deposited fat more favorably than steers, possibly due to a gradual increase in IGF-I concentration as the testicles grew rather than the large fluctuations in IGF-I concentration observed in steers following implantation.     

Effect of long-term corn by-product feeding on beef quality, strip loin fatty acid profiles, and shelf life

The objective of this study was to evaluate the meat quality and shelf life of steaks from steers fed dried distillers grains with solubles (DDGS) or dried corn gluten feed (CGF) compared with soybean meal with corn (SBM) as a protein supplement from weaning to slaughter. Angus cross steers (n = 81; BW = 306 ± 26.1 kg) were randomly assigned to pens (n = 9) and fed a stocker diet of corn silage (75% of DM) with DDGS, CGF, or SBM and ground ear corn. After 84 d of stockering, 12 steers (BW = 397 ± 15.3 kg) were randomly selected from each treatment and finished using the same protein supplement at 25% of DM for 100 d. Carcass data were collected (24 h) and the longissimus lumborum was fabricated into steaks at 48 h postmortem. Steaks were assigned to proximate analysis, Warner-Bratzler shear force (7-, 14-, or 21-d aging), and retail display (1, 3, 6, or 9 d). Protein source did not affect carcass yield, quality, or longissimus lumborum composition (P > 0.05). After 7 d of aging, DDGS and CGF steaks were more tender (P < 0.01) than SBM, but were similar (P = 0.30) after 14 and 21 d of aging. Feeding corn by-products did not influence subjective overall color acceptance (P = 0.17) in this study, but acceptance declined over time (P < 0.01). Subjective redness was similar (P > 0.05) among diets except SBM steaks were more red (P < 0.01) than DDGS after 9 d. On d 3 and 6 of retail display, CGF steaks exhibited more discoloration (P < 0.04) than SBM or DDGS steaks. However, after 9 d DDGS steaks were more discolored (P < 0.01) than CGF or SBM. Objective L* was lighter for CGF (P < 0.04) over 9 d of display, and all treatments became darker (P < 0.01) as time increased. Redness (a*) declined (P < 0.01) over time with SBM steaks maintaining more color in the red spectrum than CGF and DDGS after 6 d of display. Protein source did not affect (P > 0.05) the rate of lipid oxidation. Total SFA concentrations were similar (P > 0.05) among treatments; however, total MUFA were less (P < 0.05) and total PUFA concentrations were greater (P < 0.05) in DDGS steaks compared with SBM or CGF steaks. These data show that DDGS or CGF can be fed as a protein supplement at 25% DM from weaning until slaughter while maintaining meat quality when compared with steers fed soybean meal as a protein supplement.     

Effects of ractopamine supplementation and postmortem aging on longissimus muscle palatability of beef steers differing in biological type

Effects of ractopamine hydrochloride (RAC) supplementation and postmortem aging on palatability of beef from steers differing in biological type were evaluated using LM samples from British, Continental crossbred, and Brahman crossbred calf-fed steers (n = 98/type). Equal numbers of steers within each type were assigned to treatments of 0 or 200 mg.steer(-1).d(-1) of RAC fed during the final 28 d of the finishing period. Warner-Bratzler shear force (WBSF) was measured at 3, 7, 14, and 21 d postmortem, and trained sensory panel (TP) evaluation was conducted using LM samples aged for 14 d postmortem. A RAC x type interaction (P = 0.006) was detected for WBSF. Within each type, steers fed RAC produced steaks with greater (P < 0.05) WBSF values than steaks from control steers; however, the magnitude of the effect of RAC on WBSF was more pronounced among Brahman cross-breds (5.53 vs. 4.96 +/- 0.10 kg) than among Continental crossbred (4.16 vs. 3.96 +/- 0.10 kg) and British steers (4.10 vs. 3.75 +/- 0.10 kg). The effect of RAC on WBSF, though diminished slightly by aging (mean WBSF difference: 3 d = 0.49 kg; 21 d = 0.24 kg), was not completely mitigated by 21 d of postmortem storage (P(RAC x AGE) = 0.16). Steers fed RAC produced steaks that received lower (P < 0.05) TP ratings for tenderness (8.09 vs. 8.95 +/- 0.18) and juiciness (7.41 vs. 8.07 +/- 0.16 kg), along with slightly lower (P = 0.06) ratings for beef flavor (6.67 vs. 6.93 +/- 0.10 kg), compared with steaks from unsupplemented steers, regardless of biological type. Among the 3 biological types, Brahman crossbred cattle produced steaks with the greatest (P < 0.05) WBSF values at each aging period; WBSF values for steaks from British and Continental type steers did not differ (P > 0.05) at any aging time. Sensory panel ratings of tenderness, juiciness, and beef flavor were greatest (P < 0.05) for steaks from British steers, and least (P < 0.05) for steaks produced by Brahman-type steers. Results from this study suggest that RAC supplementation slightly decreases LM tenderness (WBSF and TP) of British, Continental crossbred, and Brahman cross-bred steers, and that the effect of RAC on WBSF may be more pronounced in steaks from Brahman crossbred cattle than among stenks from Continental type or British steers.     

Effect of pre- and postweaning zeranol implant on steer calf performance

One hundred ninety-five steer calves were assigned to five zeranol implant treatment (trial 1). Treatments were no implants (0000), two implants during the finishing period (00XX), three implants during growing and finishing periods (0XXX), one implant at 1 to 2 mo of age during the suckling period and two during the finishing period (X0XX) or four implants (XXXX). The growing period implant was administered at weaning. Weaning weights (211 vs 208 kg) of implanted and nonimplanted suckling calves were not different (P greater than .05). Calves implanted at weaning, before shipment to the feedlot, had greater (P less than .05) weight loss in shipment than nonimplanted calves. In the feedlot, finishing-period daily gains of steers implanted in the growing and finishing period (0XXX) were greater (P less than .05) than gains of steers that had received a suckling period implant (X0XX and XXXX). Nonimplanted steer gains were less (P less than .05) than gains of steers from the other four treatment groups. Postweaning daily gains and final weights were 1.18 and 517 (0000), 1.26 and 533 (00XX), 1.32 and 551 (0XXX), 1.26 and 540 (X0XX) and 1.25 and 533 kg (XXXX), respectively. Gains and final weights of nonimplanted steers were less (P less than .05) than gains of steers implanted only in the feedlot growing and finishing periods (0XXX). In a second trial, 82 steers were assigned either to a 0XXX or XXXX implant scheme. Weaning weights were 11 kg greater (P less than .05) for the implanted steers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of an early and normal weaning management system on cow and calf performance while grazing endophyte-infected tall fescue pastures

A 3-yr study used 16 cows and their spring-born calves (yr 1) and 48 first-calf heifers (yr 2, n = 24; yr 3, n = 24) and their spring-born calves in a completely randomized design. All cows and heifers were Angus x Beefmaster, and calves were sired by Angus bulls. Cow-calf pairs were assigned randomly to one of two management systems: 1) an early-weaning system, in which steer and heifer calves were weaned at 108 d of age and fed a postweaning growing diet (EW), or 2) a normal weaning system, in which calves were weaned at 205 d without supplementation (NW). Before early weaning and within each management system, calves and their dams were maintained in two 1.4-ha, endophyte-infected tall fescue pastures for 35 d (yr 1) or 14 d (yr 2 and 3). Early-weaned calves and cow-calf pairs were then randomly allotted to 1.4-ha, endophyte-infected tall fescue pastures with two (yr 1) or three (yr 2 and 3) calves or cow-calf pairs per pasture (four pastures per management system). Cow weights and BCS changes and calf gains were measured from early to normal weaning. Dietary intakes and nutrient digestibilities by EW and NW calves were determined during two periods of yr 1 and three periods of yr 2 and 3. Total gains and BCS changes were greater (P < 0.01) for cows that produced EW calves in all years. Calf ADG from early to normal weaning did not differ (P = 0.32). Similar to ADG, BW of calves at normal weaning were not different (P = 0.11). Forage intake was greater (P < 0.01) by NW calves during Periods 2 and 3 of yr 1 and Periods 1 and 2 of yr 2 and 3; however, total DM and CP intakes were greater (P < 0.01) for EW calves in Periods 2 and 3 of each year. Intakes of NDF tended (P = 0.11) to be greater by EW calves across all years. Estimates of CP and NDF digestibilities were higher (P < 0.01) for EW calves during yr 1 and 2; however, all components of the diet consumed by NW calves in yr 3 were more digestible (P < 0.05) than those consumed by EW calves. These results show the condition of cows with EW calves was improved by early weaning and gains by calves weaned at 108 d to pasture plus a commercial grower diet were comparable to those by calves continuing to nurse dams until weaned at 205 d.     

Effect of source of energy and rate of growth on performance,carcass characteristics,ruminal fermentation,and serum glucose and insulin of early-weaned steers

Seventy-three crossbred steers (initial BW = 170.5 +/- 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 +/- 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet.     

Growth implants reduced tenderness of steaks from steers and heifers with different genetic potentials for growth and marbling

The objective of this study was to evaluate the effect of growth implants on the carcass characteristics and tenderness of steers and heifers with different genetic potentials for growth, lean meat yield production, and marbling. Two experiments were conducted. Experiment 1 evaluated Angus steers sired by bulls with high EPD for retail product yield or marbling. Implant treatment was imposed randomly within sire groups. Loins (Institutional Meat Purchasing Specifications 180) were collected from each carcass and cut into three 2.54-cm steaks aged for 7, 14 and 21 d to evaluate tenderness. The second experiment evaluated steers and heifers of British and Continental breed descent. Steers and heifers were slaughtered after 120 d on feed. Loin sections were collected, and one 2.54-cm steak aged 7 d was used for tenderness analysis. When implants were used in Angus steers, HCW and LM area increased, whereas internal fat and marbling decreased (P < 0.01). In Angus steers, sire type did not affect shear force values of steaks; however, implant use significantly increased shear force values (P < 0.01). Carcasses from cattle of Continental breed descent were significantly heavier than carcasses of British breed descent with larger LM area, slightly less fat, and a reduced yield grade (P < 0.01). Also, steer carcasses were heavier than heifer carcasses with larger LM (P < 0.05), but no effect of sex on fat depth, internal fat, yield grade or marbling was observed. No significant interactions were seen between growth implant and breed or between growth implant and sex for shear force values. Shear force values were significantly less for steaks from steers and heifers of British decent compared with steers and heifers of Continental descent (P < 0.01). Steaks from implanted steers and heifers had significantly (P < 0.01) greater shear force values than steaks from steers and heifers not implanted. Use of growth implants in growing cattle resulted in significantly heavier carcass weights, larger LM area, and reduced internal fat. However, implant use also reduced the amount of marbling along with contributing to reduced tenderness. Complicating the tenderness issue is the increased shear force values reported for heifers as well as steers of Continental breed descent. Use of implants may contribute to tenderness variability because of different animal responses to implants.     

Cow-calf and feedlot performances of Brahman-derivative breeds

A study was conducted to compare Brangus, Beefmaster, Gelbray, and Simbrah breed influences for economically important traits. Brangus (9), Beefmaster (12), Gelbray (10), and Simbrah (7) sires were used in purebred and crossbred (Brahman x Hereford F1 cows) matings to generate calves (326) in eight breed groups. Beefmaster cows were of similar size (448 kg), Brangus and Gelbray cows were 11% heavier (501 and 503 kg), and Simbrah cows were 21% heavier (548 kg) compared to Brahman x Hereford F1 cows (452 kg). Calves sired by Brangus and Beefmaster bulls had lower birth weights (35 vs 38 kg; P < 0.05), preweaning growth rates (0.87 vs 0.91 kg x d(-1); P < 0.01), and weaning weights (206 vs 219 kg; P < 0.01) than Gelbray- and Simbrah-sired calves. Birth weights, preweaning ADG, and weaning weight and hip heights were similar between Brangus- and Beefmaster-sired calves. Simbrah-sired calves had greater preweaning growth rates (0.94 vs 0.88 kg x d(-1); P < 0.05), weaning weights (227 vs 211 kg; P < 0.01), and adjusted 205-d hip heights (126 vs 122 cm; P < 0.05) than Gelbray-sired calves. Straightbred Angus steers were introduced in the postweaning portion of the study. Steer calves were placed on feed at an average age of 14.5 mo. Steers were removed from the feedlot upon attaining a targeted 10 mm of backfat. Feedlot ADG did not differ among sire breeds. Brahman-derivative sired steers required an additional 54 d on feed (P < 0.01) and were 86 kg heavier (P < 0.01) at harvest than Angus steers. Continental-Brahman steers spent an additional 25 d on feed (P < 0.05) and were 35 kg heavier (P < 0.01) at harvest than British-Brahman steers. Simbrah-sired steers were 52 kg heavier (P < 0.01) at harvest than Gelbray-sired steers when fed for a similar number of days (211 vs 203 d). However, straightbred Simbrah steers required an additional 12 d on feed (P < 0.01) and weighed 47 kg more (P < 0.01) than Simbrah-sired crossbred steers. The economic value of the heavier calf weaning weights may be offset by the attendant larger cow size of the Continental-Brahman compared to the British-Brahman breeds. Similarly, the heavier weights of Continental-Brahman compared to British-Brahman steers, when harvested at a prescribed level of fatness may be viewed as a benefit, but the increased number of requisite days in the feedlot is a disadvantage.