A SYNOPSIS OF GROWTH AND CARCASS COMPOSITION IN ANGUS X HOLSTEIN HEIFERS AND AKAUSHI CATTLE WITHIN THE FEEDYARD FINISHING PHASE

The objective of this study was to evaluate the effect of days on feed (DOF) on performance and carcass characteristics of Angus x Holstein heifers (n = 3,676). At time of arrival (d 0), heifers from a single source were placed into large (~300 animal) pens at two commercial feedlot locations in the Texas Panhandle. At administration of final implant (Revalor 200; d 240), heifers, within pen, were randomly assigned to one of four smaller pens, creating a block (location A block n = 6, location B block n = 7). Pens within blocks were randomly assigned to treatment (323, 344, 365, or 386 DOF). Data were analyzed using DOF as the fixed effect; block was nested within location as a random effect. Linear and quadratic effects were also tested; pen was experimental unit (n = 52). Heifer dry matter intake (DMI) did not differ across DOF (P = 0.72). Heifer average daily gain decreased linearly (1.52, 1.37, 1.31, and 1.27 kg/d; P ≤ 0.01) as DOF increased. Heifer hot carcass weight (HCW; 372, 387, 401, and 414 kg), longissimus dorsi muscle area (88.63, 89.55, 90.80, and 91.95 cm2), and marbling score (modest35, modest53, modest63, and modest94) linearly increased (P ≤ 0.01) as DOF increased. Percentage of USDA Prime carcasses (6.6, 11.2, 12.8, and 19.0 %) increased (P ≤ 0.01) with increasing DOF. Frequency of liver scores (edible, minor, or major abscess) did not change with increasing DOF (P ≥ 0.82). Frequency of ideal heart score decreased with increasing DOF (53.0, 44.3, 25.7, and 15.0 %; P ≤ 0.01). Frequency of USDA yield grade (YG) 3 did not change (P = 0.68), however YG 4 increased with increasing DOF (6.2,12.0, 14.0, and 22.5 %; DOF P ≤ 0.01). Data collected in this trial indicate that increasing DOF led to increased HCW, LM area, marbling, YG, and QG with minimal changes to DMI or liver scores for Angus x Holstein heifers. The second study evaluated Comfort (COMF; Ralco Agriculture; Marshall, MN) as a feed additive that contains essential oils and capsicum which are antioxidants and selectively antimicrobial. The objective of this study was to evaluate the influence of COMF on growth, feedyard performance, and ultrasound parameters in Akaushi and Akaushi crossbred steers and heifers during the feedlot phase. Steers and heifers (283.50 ± 27.01 kg; n = 56) were shipped to the West Texas A&M University research feedyard (Canyon, TX); weighed, ultrasound scanned upon arrival, and allocated to treatment. Treatments were a negative control that received no COMF and a COMF treatment, received 0.23 kg/hd/d top-dressed on the ration. An equal number of steers and heifers were allocated to each treatment. Data were analyzed using treatment and sex as the fixed effect and repeated measures were day. Pen was the experimental unit. Statistical analysis was ran in SAS 9.4 utilizing PROC MIXED. Animal final BW was not different between treatments (422 COMF vs. 427 kg control; P = 0.57). Animal average daily gain (ADG) was not different between treatments (1.07 vs. 1.06 kg/d; P = 0.58). There was a significant interaction between treatment × sex for REAU (P = 0.04; 73.68 for CON steers, 74.67 for COMF steers, 78.16 for CON heifers, and 74.63 cm2 for COMF heifers). Percentage IMF, fat thickness, nor rump fat was different between the treatments (P ≥ 0.19). Data collected in this trial indicate that COMF had minimal effect on final BW, ADG, DMI, IMF, FT, and rump fat and COMF negatively affected REAU in heifers.