349 The relationship of heart score with hot carcass weight and fat depth in Angus cattle

Abstract Congestive Heart Failure (CHF) is a cardiopulmonary condition observed in cattle raised in feedlots situated at elevations above 800 m. This condition leads to right-sided heart failure caused by increased pulmonary vessel pressures and cardiopulmonary remodeling, known as pulmonary hypertension (PH). In cattle experiencing PH, pulmonary arterial pressure (PAP) becomes abnormally high, increasing heart muscle load. This load stretches muscle fibers and enlarges the right side of the heart which can lead to heart failure and death. To assess the severity of PH, animals are assigned a heart score (HS) on a scale ranging from 1 to 5 at harvest. A score of 1 represents a normal heart, while a score of 5 indicates extreme heart remodeling. Understanding the relationship between hot carcass weight (HCW), fat depth (FD), and HS in Angus cattle will provide useful information on the impacts of this condition on feedlot performance and profitability. The objective of this study was to determine if a phenotypic relationship between HCW and FD with HS in Angus-influenced cattle. For this experiment, a total of 798 black, Angus-influenced cattle were used (245 steers, 553 heifers) that were fed near Greeley, CO. The HCW, FD, and HS data from each animal were recorded at harvest. Three general linear models were used to estimate the effects of HS on HCW and FD. Mean HCW and FD were 393.1 kg, (SD = 90.9) and 0.66 mm, (SD = 0.18), respectively, with an average HS of 2.08 (SD = 0.77). For all models, HCW and FD were fit as dependent variables, while lot and HS were included as fixed effects. Model 1 included all HS categories independently. Model 2 divided HS into 2 groups of normal (HS = 1 or 2) or remodeled (HS = 3+). For model 3 HS 3 was removed leaving only HS of 4 or 5 in the remodeled group. For both HCW and FD in Model 1, the overall effect of HS was not significant (P = 0.82 and P = 0.40, respectively). However, when comparing individual scores, animals with a HS = 4 were 15.0 kg lighter for HCW than individuals with a HS = 1 (P < 0.05). Conversely for FD, a non-significant difference (P = 0.74) of -0.33 mm was observed between animals with a HS = 4 versus a HS = 1. Grouping HS into 2 categories in Model 2 did change the outcome, yielding non-significant HCW and FD differences. However, when eliminating the HS = 3 data, a significant reduction in HCW of 16.9 kg (P = 0.05) was observed between the 2 HS groups, whereas non-significant effects on FD remained. These data suggest that at extreme levels of heart remodeling HCW may be extremely impacted negatively.