Effect of Age at Weaning and Post-Weaning Management on Performance and Carcass Characteristics of Angus and Charolais-Angus Steers John F. Grimes County Extension Educator, ANR OSU Extension – Highland Co.

HISTORY AT SOUTHERN ARS Early weaning work began in the mid-1980s. Most recent study began with purchase of bred heifers in Replacement females came from one additional female purchase and retained heifer calves. First four calf crops were sired by Angus bulls. Last two calf crops were sired by Charolais bulls.

INVESTIGATORS John F. Grimes, OSU Extension-Highland Co. Francis L. Fluharty, OSU Dept. of Animal Sciences, Wooster Thomas B. Turner, OSU Dept. of Animal Sciences, Columbus Henry N. Zerby, OSU Dept. of Animal Sciences, Columbus Gary D. Lowe, OSU Dept. of Animal Sciences, Wooster

STUDY OBJECTIVE To examine the effects of different calf management systems on live animal performance and carcass merit.

Days on Feed Determines Marbling Smith (1995) predicted that cattle needed to be on feed 167 to 236 days, and be 835 to 945 pounds before lipogenesis begins, but the cattle were 265 d. of age when they started in the feedlot, which meant that they had to be 14 to 16 months old before they were predicted to begin marbling.

Days on Feed Determines Marbling HOWEVER, Myers et al. (1999) weaned steers at 117 days of age, and fed them a high-concentrate diet for 268 days before they were slaughtered at 394 days of age (13 months of age). The cattle graded 89% low choice or higher, with 56% in the upper 2/3 of the choice grade or higher.

Days on Feed Determines Marbling Fluharty (2000) weaned steers at 103 days of age, and fed them a high- concentrate diet for 282 days before they were slaughtered at 385 days of age (13 months of age). The cattle graded 85% low choice or higher, with 60% in the upper 2/3 of the choice grade or higher.

Days on Feed Determines Marbling Research has shown that cattle can grade choice anywhere from 13 to 26 months of age. Diet, management, and genetics determine whether an animal will grade choice within this age range. Many of the papers that have reported that cattle needed to be a certain age to grade choice already started with yearlings.

Days on Feed Determines Marbling In fact, many animals that do not grade choice at an advanced age probably would have graded choice at a younger age under management and diet strategies that used a high concentrate diet earlier in life. University of Illinois research shows that yearlings need 1/4 inch more backfat to achieve the same marbling score as early weaned calves harvested at the same marbling end point.

USDA Quality Grades Slight = USDA Select Small = USDA Low Choice Modest = USDA Avg. Choice Moderate = USDA High Choice Sl. Abundant = USDA Low Prime Mod. Abundant = USDA Avg. Prime

TREATMENTS 1. Early wean (EW) at approximately 100 days, fast-track feeding, harvest at months of age. 2. Normal wean (NW) at approximately 200 days, fast-track feeding, harvest at months of age. 3. Normal wean at approximately 200 days, stocker (YR) to lbs., finish and harvest at months of age.

MATERIALS AND METHODS Calving season of approx. 90 days in early Feb. to early May & 2002 calf crops were sired by Angus bulls & 2004 calf crops were sired by Charolais bulls. No calves received creep feed while nursing their dams.

MATERIALS AND METHODS Once the entire calf crop was born, the average birth date was established. Steer calves were alternately assigned into the three treatment groups based on chronological birth order. Once placed into their treatment groups, calves were alternately assigned to replication groups based on chronological birth order.

MATERIALS AND METHODS All calves were fed a high-gain diet during the finishing phase. Harvest time for the steers was determined by a combination of visual appraisal and monitoring the weight and average daily gain for each steer. All steers were processed at The OSU Animal Science Dept.s Meat Laboratory in Columbus.

RESULTS Harvest weight increased as age at feedlot entry increased: EW: 1143 lbs., NW: 1164 lbs., and YR: 1216 lbs. (P<.01) Dressing % decreased as age at feedlot entry increased: EW: 63.6%, NW: 62.8%, and YR: 60.9% (P<.01) Backfat decreased as age at feedlot entry increased: EW:.70, NW:.59, and YR:.52 (P<.01)

RESULTS The percentage of carcasses grading USDA Average or High Choice was higher for EW (75.9%) and NW (75.9%) than YR (45%). (P<.05) The percentage of carcasses grading USDA Prime was higher for EW (15.8%) and NW (8.3%) than YR (0%). Yield Grades tended to be numerically higher with the EW cattle than the other 2 groups. No clear trends in tenderness emerged in this study.

RESULTS Age at harvest: EW days, NW – 408 days, YR – 535 days Feed conversion (lbs. feed per lb. gain): EW – 5.1, NW – 5.7, YR – 6.4

RESULTS Harvest weight increased as age at feedlot entry increased: EW: 1163 lbs., NW: 1179 lbs., and YR: 1280 lbs. (P<.01) Dressing % decreased as age at feedlot entry increased: EW: 63.4%, NW: 62.8%, and YR: 61.3% (P<.01) Backfat decreased as age at feedlot entry increased: EW:.54, NW:.45, and YR:.39 (P<.01)

RESULTS The percentage of carcasses grading USDA Average or High Choice trended higher for EW (49.2%) and NW (40.3%) than YR (38.1%). The percentage of carcasses grading USDA Prime was higher for EW (4.2%) than NW (0%) and YR (0%). Yield Grades were numerically higher with the EW (3.2) than the NW (3.1) or YR (3.0) cattle. (P<.05)

RESULTS Age at harvest: EW days, NW – 419 days, YR – 559 days Feed conversion (lbs. feed per lb. gain): EW – 5.3, NW – 5.4, YR – 6.6 Feed conversion (lbs. feed per lb. gain): EW – 5.3, NW – 5.4, YR – 6.6

SIRE DIFFERENCES Charolais-sired calves had less backfat at harvest: EW: -.16 in., NW: -.15 in., YR: -.13 in. Charolais-sired calves had more rib eye area at harvest: EW: 1.0 in., NW:.6 in., YR: 1.0 in. Charolais-sired calves had numerically lower Yield Grades: EW: -.7, NW: -.5, YR: -.6

SIRE DIFFERENCES Angus-sired calves had higher Quality Grades (% Avg. Choice and higher): EW: +26.7%, NW: +35.6%, YR: +6.9% Both sire groups had similar feed conversion rates across treatment groups