7 Evaluation of Finishing Performance and Carcass Characteristics of Beef Heifers with Variable Degrees of Heart Failure Risk and Differing Reproductive Tract Type

Abstract Tremendous economic loss is attributed to high altitude disease mortality of calves in the Mountain West and Great Plains region. Additional economic losses may be associated with changes in feed efficiency and carcass quality in animals at higher risk of heart failure during the finishing phase. Thus, the objective of the current study is to evaluate economically relevant traits throughout the finishing period to determine inefficiencies associated with variable levels of heart failure risk and reproductive tract type of beef heifers. Both intact reproductive tract (n = 19) and ovariectomized (n = 18) heifers were stratified by risk category, where initial pulmonary arterial pressure (PAP) levels at or below 42 mmHg were designated as low risk and those above 42 mmHg as moderate/high risk. Heifers were fed a grain-based diet for 125 d before transportation to the harvest facility on d 126. All heifers were weighed in 2 wk intervals. Heifers were PAP tested by a qualified veterinarian in approximately 3 mo intervals during the feeding period. Feed intake data was collected for the last 55 d prior to harvest using the Vytelle SENSETM bunk system. Time of harvest was determined based on live weight and final ultrasound 12th rib fat thickness. Data were analyzed using the ANOVA function of R with tract type and risk as fixed effects. Comparisons were tested using a significance level of α = 0.05 and 0.05 (P ≤ 0.10) were considered tendencies. There were no interactions of risk category and tract type on performance or carcass characteristics (P ≥ 0.14). There was a tendency for higher total intake (P = 0.07) and relative growth rate (P = 0.04) among moderate/high risk heifers compared to the low-risk category. Hot carcass weight, marbling score, ribeye area, and USDA yield grade were not impacted (P ≥ 0.16) by risk category. Intact heifers had greater (P = 0.02) total gain than their ovariectomized contemporaries. However, marbling scores were higher (P = 0.04) among ovariectomized heifers compared to those from intact heifers. These data suggest that risk category and tract type minimally influence performance and carcass characteristics in a population that selects sires with low PAP scores. It remains unclear if more initial divergence in PAP scores would elicit greater impacts on performance and carcass characteristics in feedlot heifers.