Influence of source of origin and region of finishing on growth performance and carcass characteristics of finishing heifers fed in the United States.

Abstract

The objective was to evaluate growth performance and carcass traits of finishing beef heifers sourced and finished in different regions in the U.S. Heifers (n = 190; initial body weight [BW] 483 ± 0.4 kg and 425 ± 1.9 kg for South Dakota [SD] and TX sourced, respectively) were used in a 2 × 2 factorial arrangement of origin state (SD vs. TX) and finishing state (SD vs. TX) was used. Heifers were allotted on day -1 to: 1) sourced from SD and finished in SD (SD-SD), 2) sourced from SD and finished in TX (SD-TX), 3) sourced from TX and finished in SD (TX-SD), and 4) sourced from TX and finished in TX (TX-TX). Heifers were weighed on d -1, 3, 15, 28, 56, 78 (TX-TX and SD-TX) and 90 (SD-SD and TX-SD). On day 0, SD-TX and TX-SD heifers were shipped to their respective finishing locations. The following morning (day 1), SD-TX and TX-SD heifers were individually weighed to determine transit shrink. To monitor transit stress effects, vaginal temperature probes were used on all SD-TX and TX-SD heifers and a portion of SD-SD and TX-TX heifers on day -1 and removed on day 3. Clinical attitude scores (CAS) were recorded on days -1, 0, 1, 2, and 3 for bovine respiratory disease symptoms. Transported heifers had decreased temperatures (P ≤ 0.01) during transit and post-transit and increased (P ≤ 0.01) vaginal temperature during loading and unloading compared to non-transported heifers. On days 0, 1, and 3 there was a shift in the distribution of heifers that had a CAS score greater than 0 for TX-TX, SD-TX, and TX-SD. Heifers endured elevated ambient temperatures (temperature-humidity index > 75) for 54% and 18% of the feeding period for TX and SD. Growth performance and carcass trait interactions were significant (P < 0.01) except for day -1 BW, percent shrink during transit, average daily gain, dressing percent, ribeye area, and liver abscess severity, which did not differ (P > 0.30). A shift in the distribution (P < 0.02) towards a greater proportion of Yield Grade (YG) 1 and Select carcasses was observed for TX versus SD. Overall, heifers transported to higher ambient temperatures had improved overall YGs but decreased dry matter intake, quality grades (QG), and limited growth recovery (45 kg lighter) following transit than non-transported heifers. Heifers transported to lower ambient temperatures recovered growth and had improved QG (P < 0.02) at the same thickness of rib fat compared to non-transported heifers but had decreased overall yield and yield grades.