Abstract
Abstract Global climate change has had, and will continue to have, a negative impact on cattle production. With the global population expected to exceed 9 billion people by 2050, improving production efficiency is imperative to optimizing use of available land and natural resources. One potential method of doing so is to increase the percentage of Bos indicus (BI) genetics in the US beef herd. Compared with Bos taurus (BT) cattle, BI influenced cattle are better adapted to nutritional stress, consume less water, are more heat resistant, and have increased resistance to parasites. The objective of this study was to examine the phenotypic and genotypic outcomes of introducing BI genetics into a BT herd in a temperate climate setting. This study included a live animal trial that utilized a total of 115 steers of two different breeds: Angus (AN; n = 83; 100% BT) or Santa Gertrudis influenced (SG; n = 32; 19% BI, 81% BT). All steers were fed a typical feedlot ration for the area in pens equipped with Vytelle units, weighed every 28 d throughout the trial, and harvested at a commercial facility once industry backfat standards were achieved. Breed did not have an effect (P >0.10) on dry matter intake, average daily gain, gain to feed, ribeye fat thickness, hot carcass weight, or USDA yield grade. Intramuscular fat was increased (P = 0.002) in AN steers, and there was a tendency (P = 0.09) for SG steers to spend more time with their heads down during bunk visits. To better examine the genomic differences between the two beef breeds, DNA from 88 (AN = 58, SG = 30) of the 115 steers was isolated. A Bovine GGP 100k assay was completed commercially, and data were analyzed using Excel and the Multi-Locus Mixed Model of SVS. The traits that were analyzed include average daily gain, gain to feed, dry matter intake, hot carcass weight, marbling score, cold camera ribeye size, ribeye fat thickness, and cold camera yield grade. For each trait, further evaluation was done on SNP markers with the greatest P-values. Differences in allelic combinations that contributed to statistical significance was observed in data attained from dry matter intake, hot carcass weight, marbling score, and cold camera yield grade. Further analysis suggested a potential breed effect on marbling score, cold camera yield grade, and cold camera ribeye size. Additional research is warranted to better understand the relationship between genetics and the observed phenotypic traits, as well as conducting similar analysis on feeding behavior characteristics.