246 Evaluation of Live Growth Performance and Carcass Characteristics of Late Finishing Phase Beef Cattle with Varying Degrees of Pulmonary Hypertension
Authors: Markel Chase D , Holt Timothy N , Lake Scott L , Woodruff Kelly L , Mills Bryson , Bedke Clayton , Gifford Cody , Cunningham-Hollinger Hannah C 
Published: November 2023

Abstract
Late feedlot death caused by congestive heart failure has been quantified extensively through epidemiological studies however, these models do not consider losses or gains associated live growth performance, carcass quality, and consumer rejection of meat products. To address these gaps in the literature, we conducted two studies to characterize effects of pulmonary hypertension on four populations of feedlot cattle. In study one, reproductively intact (INT, n = 19), and ovariectomized (OVX, n = 18) yearling Sim-Angus heifers were selected on heart failure risk according to their pulmonary arterial pressure. Heifers were gradually transitioned onto a feedlot ration and fed to an acceptable harvest body composition determined using both 12th rib subcutaneous fat and body weight. Cattle were weighed biweekly and ADG was calculated by regressing body weight by days on feed (DOF). Pulmonary arterial pressure (PAP) was measured approximately every 3 months by a qualified veterinarian. Cattle were harvested at a commercial harvesting facility where carcass data and muscle samples were collected. In study two, weaned sim-angus steers (n = 41) were selected on heart failure risk categories using the same methodology outline above. Twenty steers were administered a steroidal growth promoting implant upon receiving (IMP) and twenty were untreated (NAT). Steers were fed to an average of 610 kg and data were collected using the same methodology outlined above. Data were analyzed using ANOVA, linear model, and Pearson correlation functions in R statistical software where PAP was used as a fixed continuous variable. Data were analyzed by study with the exception of live growth performance regression and correlations where data were combined. Linear regression within the combined datasets showed that initial mean PAP (P &lt; 0.001), diastolic pressure (P &lt; 0.001), and sex (P &lt; 0.001) positively influenced ADG throughout the duration of the finishing period. Furthermore, initial PAP was moderately correlated with ADG (R = 0.38, P &lt; 0.001). Gain to feed (G:F) was positively correlated with initial diastolic PAP (R = 0.31, P &lt; 0.006). Neither initial mean PAP nor diastolic pressures impacted dry matter intake (DMI; P &gt; 0.90), but sex was associated with DMI where steers had significantly decreased DMI (P = 0.003). Within study two, longissimus muscle objective color values were influenced by PAP where a* (redness; P &lt; 0.001) and b* (yellowness; P &lt; 0.04) values were negatively correlated with final PAP. These data begin to demonstrate the close relationship between live growth performance and pulmonary hypertension. More research is needed to better understand how cellular energy metabolism is potentially contributing to increased growth performance but negatively influencing muscle health in the form of oxygen binding capacity and inflammation.