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Effect of Time of Birth Within the Spring Calving Season on Performance and Carcass Traits of Beef Calves Fed in the Iowa Tri-County Steer Carcass Futurity. G.D. Fike 1 , M.E. King 1 , L.R. Corah 1 and W.D. Busby 2 1 Certified Angus Beef LLC 2 Iowa Tri-County Steer Carcass Futurity
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Effect of Time of Birth Within the Spring Calving Season on Performance and Carcass Traits of Beef Calves Fed in the IowaTri-County Steer Carcass Futurity G.D. Fike1, M.E. King1, L.R. Corah1 and W.D. Busby2 1Certified Angus Beef LLC 2Iowa Tri-County Steer Carcass Futurity 2010 Annual ASAS Meeting
Introduction and Background • Larson, et al., (2010) found that calves born during the first 21 d calving period had greater HCW, marbling scores and greater % grading premium Choice and higher carcass values than calves born in the 2nd or 3rd 21 d intervals; however, no differences were found in ADG
Objectives • Does age of calf and time of birth within the calving season affect: • Feedlot performance • Marbling score and, ultimately, USDA quality grade • Certified Angus Beef ® (CAB®) acceptance rate
Materials and Methods • Data were analyzed on 1,369 calves from a single, central Missouri ranch for a six-year period (2002-2007) • Genetics were Angus/Simmental-based, rotating sires among different years • All cattle were fed a common dietary energy level and administered similar health and implant treatments in a southwest Iowa feedlot • All cattle were weighed, sorted, vaccinated, implanted, disposition scored and body conditioned scored within 4 days of arrival
Materials and Methods • Calves were sorted and harvested when visually determined to have one cm of fat cover • Only cattle with full, detailed carcass and performance information were included in the study • Calves were divided into four sequence groups: • Early – born d 1-21 of calving season (E) • Mid-early – born d 22-42 (ME) • Mid-late – born d 43-63 (ML) and • Late – born d>63 (L)
Materials and Methods • Statistical analyses: • Continuous outcomes were quantified using one-way analysis of variance (ANOVA) • For rate analyses, Chi-square was employed
Percent Angus of the Calf by Birth Sequence Within the Spring Calving Season a abcMeans with unlike superscripts differ (P<0.05)
Disposition Score1 of the Calf by Birth Sequence Within the Spring Calving Season a 1Disposition score: 1=docile; 6=very aggressive abMeans with unlike superscripts differ (P<0.05)
Feedlot Delivery Weight, Adjusted Final Weight, Harvest Age and HCW by Birth Sequence Within the Spring Calving Season abcdMeans within a row with unlike superscripts differ (P<0.05)
Carcass Merit by Birth Sequence Within the Spring Calving Season a bMeans within a row with unlike superscripts differ (P<0.05) 1Marbling score: 400=Small0; 500=Modest0
Quality Grade by Birth Sequence Within the Spring Calving Season
Conclusions • The oldest calves were/had: • Heavier at feedlot delivery • Heavier at harvest and greater HCW • Greater marbling scores • Higher percentage of calves grading USDA Choice and CAB® • Greater carcass value per head • Than their latest born counterparts