03493naa a2200301 a 450000100080000000500110000800800410001902400250006010000150008524501830010026000090028350004970029252020740078965300160286365300240287965300320290365300330293565300110296865300130297965300160299265300080300870000150301670000180303170000190304970000160306870000140308477300930309810614182021-02-24       2020    bl uuuu     u00u1 u    #d7 a10.1071/AN196042DOI1 aCORREA, D.  aEffects of differences in level of post-weaning nutrition and in sire expected progeny differences for ribeye area on retail cuts yield in Hereford steers.h[electronic resource]  c2020  aArticle history: Received 25 October 2019, accepted 25 September 2020, published online 15 October 2020. Acknowledgements: The authors would like to thank INIA Uruguay for the funding which made this study possible. We would also like to acknowledge MARFRIG’s staff and the Uruguayan Hereford Association, especially to Diego Vila from Laguna Blanca farm. Also, we would like to thank Fiorella Cazzuli and Zully Ramos for their contributions. Corresponding author. Email: gbrito@inia.org.uy  aAbstract: Context. Uninterrupted nutrient uptake and the use of bulls with high genetic merit for carcass traits may increase the likelihood of producing high-quality retail cuts for different markets. Aim. The objective of this experiment was to evaluate the combined effects of level of nutrition during the 104-day post-weaning winter period (WADG; low-L: 0.2 vs high-H: 0.6 kg/calf per day) and level of expected progeny differences (EPD) for ribeye area (REA; high-H or average-Av) on carcass traits and retail cuts of Hereford steers. Methods. Three crops of calves (n = 317) were selected according to REA (H-REA vs Av-REA), blocked for weaning weight (WW) and randomly allotted to one of the two WADG treatments (L-WADG vs H-WADG) for 104 days. Experimental design was a completely random block and the treatments were the combination of two factors (2 · 2). After winter (L-WADG and H-WADG groups), all calves grazed on improved pastures (herbage allowance: 5% of liveweight (LW) per day). The finishing was done on a feedlot and started when the group average of animals reached a full LW (FLW) of 350  28 kg. Cattle were harvested at a constant final FLW of 525  40 kg. Key results. No interaction was observed (P > 0.05) between WADG and REA for carcass traits. Animals with H-WADG presented higher (P < 0.05) hot carcass weight (HCW) and dressing-out (%) than L-WADG. High REA and H-WADG steers showed higher weight (kg) in the rump and loin, striploin, sirloin, and lean component in the pistola cut (P < 0.01). Likewise, H-REA and H-WADG presented a greater proportion of rump and loin (P < 0.01) and lean (%) (P < 0.05) than Av-REA and L-WADG, respectively. Conclusions. The combined effects of greater post-weaning winter gains and high REA EPD allow slaughter of younger steer with greater lean proportion and retail cuts. Implications. No interaction between the REA and WADG allows producers to plan economic benefits through a higher WADG in the first winter phase as well as using superior bulls for carcass traits to achieve heavier retail cuts.  aBEEF CATTLE  aCARCASS COMPOSITION  aEXPECTED PROGENY DIFFERENCE  aGENETIC MERIT OF RIBEYE AREA  aGROWTH  aHEREFORD  aMEAT EXPORT  aREA1 aLEMA, O.M.1 aRAVAGNOLO, O.1 aCLARIGET, J.M.1 aLUZARDO, S.1 aBRITO, G.  tAnimal Production Science, 2020, 61(2), p. 172-178. DOI: https://doi.org/10.1071/AN19604