|MCKIBBEN, HEATHER - University Of Wyoming|
|NOTTER, DAVID - Virginia Polytechnic Institution & State University|
|STEWART, WHITNEY - University Of Wyoming|
|MEANS, WARRIE - University Of Wyoming|
|Taylor, Joshua - Bret|
Submitted to: Translational Animal Science
Publication Type: Proceedings
Publication Acceptance Date: 5/31/2019
Publication Date: 12/19/2019
Citation: Mckibben, H.N., Notter, D.R., Stewart, W.C., Means, W.J., Pierce, N.L., Taylor, J.B. 2019. Comparison of new composite breeds with the Suffolk breed as terminal sires in an extensive production system: Carcass characteristics. Translational Animal Science. 3(suppl. 1):1701-1704. https://doi.org/10.1093/tas/txz061.
Interpretive Summary: Not required.
Technical Abstract: The objective of this study was to compare the carcass characteristics of lambs produced by U.S. Sheep Experiment Station terminal-sire composite (TSC), Siremax composite, and Suffolk rams, when used as terminal sires mated to range-type ewes. We hypothesized that crossbred lambs produced by the composite sire breeds would have similar consistency and carcass yield to Suffolk-sired crossbreed lambs. Crossbred lambs were produced in 2015, 2016, and 2017 by single-sire mating of Suffolk (n = 24), Siremax (n = 24), and TSC (n = 24) rams with mature (2 to 7-year–old) Targhee (n = 213), Polypay (n = 206), and Rambouillet (n = 208) ewes. After weaning, lambs of the same sire breed and sex were fed in replicated feedlot pens. Lambs were blocked by dam breed, with approximately equal numbers of lambs by each dam breed in each pen. Within each pen and dam breed, lambs were randomly assigned to 1 of 3 slaughter groups and targeted for slaughter at mean BW of 56, 61 and 66 kg. A total of 755 lambs were harvested across 3 years. Lambs were harvested in a single commercial abattoir. Hot carcass weights (HCW) were determined, and yield grades were estimated based on image analysis of unribbed carcasses. After images were obtained and carcasses were chilled at 2 to 4C for approximately 24 h, carcasses were ribbed and longissimus muscle area (LMA), 12th-rib fat depth, and body wall thickness were determined. Sire breed did not affect LMA (P = 0.07) or image-based yield grade (P = 0.60), but sire breeds differed (P < 0.001) for HCW, 12th-rib fat depth (P =0.04), body wall thickness (P = 0.02), calculated percentage of boneless closely trimmed retail cuts (%BCTRC; P = 0.02), estimated boneless closely-trimmed retail-cut weight (EstBCTRCwt; P = 0.00), and calculated yield grade (P = 0.04). Suffolk-sired lambs had 1.66-kg heavier (P = 0.001) HCW than composite-sired lambs. The HCW did not differ (P = 0.73) between TSC- and Siremax-sired lambs. Sire breed affected (P = 0.02) EstBCTRCwt. Suffolk-sired lambs had 0.63 kg (4.2%) heavier (P = 0.001) EstBCTRCwt than composite-sired lambs, with no difference (P = 0.89) between TSC- and Siremax-sired lambs. Results from this study indicated that Suffolk-sired lambs had heavier HCW and EstBCTRCwt, compared with lambs sired by the TSC and Siremax composite breeds, while TSC- and Siremax-sired lambs were similar in all traits measured.