Available at: https://digitalcommons.calpoly.edu/theses/3220
Date of Award
12-2025
Degree Name
MS in Agriculture - Animal Science
Department/Program
Animal Science
College
College of Agriculture, Food, and Environmental Sciences
Advisor
Zachary McFarlane
Advisor Department
Animal Science
Advisor College
College of Agriculture, Food, and Environmental Sciences
Abstract
Feed efficiency in beef cattle is a complex trait shaped by physiological, behavioral, and social factors that influence how animals access and utilize feed resources. This study examined feed efficiency classification and how it is influenced by feeding behavior, competitive interactions, and bunk approach patterns in yearling Angus bulls housed in a drylot over two years. Bulls were grouped into high and low feed efficiency categories using residual feed intake and feed conversion ratio within pen and year (n = 40 per year; n = 40 per treatment). Continuous electronic monitoring quantified feeder visitation, feeding duration, intake, and rate. A subset of bulls (n = 20) was evaluated for competitive behavior through video analysis of displacement events at the feed bunk. Low efficiency bulls visited the feeder more frequently, spent more time feeding, and consumed greater amounts of feed across the day compared with high efficiency bulls (P ≤ 0.01). These differences were driven by increased visit frequency rather than longer visit duration or faster eating rates, as visit length and intake per visit did not differ between efficiency groups (P ≥ 0.61). Both groups exhibited pronounced circadian feeding rhythms, with shared peaks during morning and afternoon feed delivery. There were no efficiency group × hour interactions for feeding duration or intake (P ≥ 0.85). Latency to approach the bunk after feed delivery did not differ by efficiency group (P = 0.77) but was shorter in the morning than in the afternoon (P = 0.001), indicating a time-of-day effect on feeding motivation. Competitive behavior revealed a contrasting pattern. High efficiency bulls initiated more displacements per day than low efficiency bulls (P = 0.05) and showed a higher competition index, indicating greater success in winning competitive encounters (P = 0.03). Reactor rate tended to be higher in efficient bulls (P = 0.06), suggesting increased social activity overall. These findings indicate that low efficiency bulls achieve greater intake through higher feeding frequency and cumulative feeding time, compared to high efficiency bulls which displayed a more energy efficient feeding strategy supported by greater competitive ability. Collectively, the results highlight the interplay between feeding behavior, social dynamics, and feed efficiency, emphasizing the value of integrating behavioral metrics into feed efficiency evaluations and selection programs. Identifying bulls with higher feed efficiency will help in selecting the best breeding stock.