Associations of rumen parameters with feed efficiency and sampling routine in beef cattle

Area of Science:

• Animal Science
• Ruminant Nutrition
• Feedlot Cattle Management

Background:

• Understanding feed efficiency in cattle is crucial for optimizing livestock production and sustainability.
• Ruminal parameters are fundamental to feed utilization, but their relationship with feed efficiency requires further characterization.
• Sampling routines can influence the assessment of ruminal parameters, necessitating a comparison between on-farm and at-slaughter data.

Purpose of the Study:

• To evaluate microbial and volatile fatty acid (VFA) profiles, rumen papillae epithelial thickness, and rumen pH (RpH) and temperature (RT) in feedlot cattle with varying feed efficiency.
• To compare ruminal parameters between efficient and inefficient cattle based on residual feed intake (RFI).
• To investigate the impact of sampling time (on-farm vs. at slaughter) on the assessment of ruminal parameters and their correlation with feed efficiency.

Main Methods:

• Forty-eight feedlot cattle (32 steers, 16 bulls) were assessed for residual feed intake (RFI) using performance traits.
• Rumen fluid and tissue samples were collected at slaughter, along with RpH and RT data from inserted loggers.
• Microbial populations (bacteria, methanogens), VFA profiles, rumen papillae thickness, RpH, and RT were analyzed and compared between efficient and inefficient groups.

Main Results:

• Efficient cattle consumed less dry matter while maintaining similar productive performance compared to inefficient cattle.
• Efficient cattle exhibited higher ruminal bacteria and lower methanogen populations at slaughter, but not on-farm.
• Increased rumen epithelium thickness and greater time spent in acidotic and optimal RpH ranges were observed in efficient cattle.

Conclusions:

• Superior feed efficiency in cattle is associated with specific ruminal features, including microbial abundance and rumen epithelial histomorphology.
• Rumen pH, microbial populations, and epithelial thickness may serve as reliable indicators for predicting feed efficiency in cattle.
• Discrepancies between on-farm and at-slaughter measurements highlight the importance of considering sampling methodology when developing feed efficiency proxies.