Genetic parameters for frame size and carcass traits in Nellore cattle

Area of Science:

• Animal Genetics
• Quantitative Genetics
• Beef Cattle Production

Background:

• Genetic improvement of carcass quality is crucial in beef cattle production.
• Frame size is a potential, yet under-evaluated, selection criterion.
• Ultrasound technology offers non-invasive carcass trait measurements.

Purpose of the Study:

• To assess frame size (FRAME) as a genetic selection criterion in Nellore cattle.
• To determine the association between visual scores and ultrasound-measured carcass traits.
• To evaluate the genetic improvement potential for carcass quality.

Main Methods:

• Variance components were estimated using restricted maximum likelihood (REML).
• Traits analyzed included thoracic perimeter (TP), FRAME, yearling weight (YW), visual scores (body structure, muscularity, precocity), and carcass traits (loin eye area, backfat, rump fat, intramuscular fat).
• Genetic correlations between traits were calculated.

Main Results:

• Heritability estimates for the studied traits were moderate to high.
• FRAME showed strong positive genetic correlations with YW (0.82) and body structure (0.62), but negative correlations with muscularity (-0.34) and precocity (-0.50).
• Positive genetic correlation was observed between FRAME and loin eye area (0.26), with near-zero correlations for fat deposition traits.

Conclusions:

• Frame size can be a useful parameter for selecting precocious beef cattle.
• Thoracic perimeter is positively correlated with growth and muscularity traits.
• Further studies are required to establish the ideal frame size biotype for diverse production systems.