The effect of breed and days on feed on feedlot performance, ultrasound and meat quality traits, and dissected body composition of British, European and Bos indicus steers

Abstract

The global population is rapidly growing, increasing protein requirements and thus, driving the beef feedlot industry to optimise efficiency and productivity. Accurately determining the time of slaughter to achieve the optimal carcass endpoint of cattle is integral to achieving the maximum carcass yield and minimising feed and fat wastage. Whole body and carcass composition of feedlot cattle is affected by several factors including diet, breed, and feeding length, amongst others, which in turn determine the optimal carcass endpoint. Physical dissection is used to determine whole body and carcass composition, but such data is limited due to the immense labour, infrastructure and cost. The literature review revealed that existing prediction models for animal growth and nutrition utilise decades old data with narrow breed diversity (e.g. British breeds), thus the accuracy of these models for modern beef genetics are unknown. Therefore, there is a need of detailed animal performance and body composition data of growing feedlot cattle to understand the rate of muscle and fat deposition in different depots of the main biotypes of cattle. This information is essential to target and achieve market specifications and optimise carcass value. The general objective of the present thesis was to determine the effect of breed and days on feed (DOF) on the feedlot performance, feed efficiency, whole body and carcass composition, and carcass yield and quality. The general hypothesis was that breed and DOF affect all aspects outlined in the general thesis objective.