2159 Key words: Brahman, breed effects, carcass traits, heterosis, Romosinuano © 2012 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2012.90:2159–2166 doi:10.2527/jas2011-4471 ABSTRACT: The objectives of this work were to esti- mate heterosis and breed genetic effects for carcass quantity, quality, and palatability traits of steers (Bos spp.) produced from matings of Romosinuano, Brahman, and Angus cattle. Steers (n = 464) were weaned at 7 mo of age and transported to the Southern Great Plains where they grazed winter wheat for 6 mo and were then fed a finishing diet until serial slaughter after different days on feed (average 130 d). Carcass quality and quantity traits were measured; steaks (aged 7 d) were obtained for palat- ability evaluation. Heterosis was detected for BW, HCW, dressing percentage, LM area, and yield grade for all pairs of breeds. Generally, Romosinuano-Angus heterosis esti- mates were smallest, Romosinuano-Brahman estimates were intermediate, and Brahman-Angus heterosis esti- mates were largest. The direct Romosinuano effect was to decrease (P < 0.05) BW (–67 ± 16 kg), HCW (–48 ± 10 kg), dressing percentage (–1.4 ± 0.5 units), 12th rib fat thickness (–5.2 ± 0.8 mm), and yield grade (–0.9 ± 0.1), and to increase LM area per 100 kg HCW (3.6 ± 0.3 cm 2 /100 kg). Signi ficant Brahman direct effects were detected for BW (34 ± 17 kg), HCW (29 ± 10 kg), dressing percentage (1.6 ± 0.6 %), LM area per 100 kg HCW (–3.3 ± 0.4 cm 2 /100 kg), and yield grade (0.6 ± 0.1). Signi ficant Angus direct effects were to increase 12th rib fat thickness (3.8 ± 1 mm). Among sire breed means, Romosinuano had reduced (P = 0.002) marbling score (393 ± 9) than Angus, but greater mean sensory tenderness scores (5.8 ± 0.1), and reduced percentage Standard carcasses (10 ± 2%) than Brahman (P < 0.002). Angus sire breed means for marbling score (475 ± 10), overall tenderness (5.8 ± 0.1), and percentage Choice carcasses (75 ± 5%) were greater (P < 0.05) than Brahman sire breed means (360 ± 11, 5.4 ± 0.1, 31 ± 5%). From consideration only of characteristics of the end product of beef production, Romosinuano did not provide a clearly superior alternative to Brahman for U.S. producers, as they had some quality and palatability advantages relative to Brahman, but at lighter HCW. Genetic effects on carcass quantity, quality, and palatability traits in straightbred and crossbred Romosinuano steers 1,2 D. G. Riley,* 3 C. C. Chase, Jr.,* S. W. Coleman,* 4 W. A. Phillips,† M. F. Miller,‡ J. C. Brooks,‡ D. D. Johnson,§ and T. A. Olson§ *Subtropical Agricultural Research Station, USDA, ARS, Brooksville, FL 34601; †Grazinglands Research Laboratory, USDA, ARS, El Reno, OK 73036; ‡Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409; and §Department of Animal Sciences, University of Florida, Gainesville 32611 INTRODUCTION Brahman crossbred cows are adapted, superior per- formers and widely used by cow-calf producers in the Southern United States, primarily because of the harsh conditions in that region. The steer half-siblings of these females are often sent to the Great Plains for feeding until slaughter. The reputation for inadequate carcass quality and tenderness for both Brahman purebreds and crossbreds almost surely results in lower prices paid for calves with visible Brahman inheritance. Other cattle of the world are adapted to the conditions of the trop- 1 Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product to the exclusion of others that may also be suitable. 2 Appreciation is extended to E. L. Adams, E. J. Bowers, M. L. Rooks, V. E. Rooks, and all of the STARS staff for technical assistance and animal care. 3 Corresponding author: david-riley@tamu.edu 4 Current address: Grazinglands Research Laboratory, USDA, ARS, El Reno, OK, 73036 Received July 12, 2011. Accepted January 12, 2012. Published January 20, 2015