STUDY OF GROWTH AND CARCASS TRAITS MEASURED BY ULTRASOUND IN TWO GENETIC GROUPS OF HEIFERS

Abstract

The aim of this work was to study the effect of genetic group on body weight (BW), hip height (HH), chest girth (CG), longissimus muscle area (LMA), backfat thickness (BF), rump fat thickness (RF), and muscle index (MI=100×LMA/BW), and the relationship between them by using correlation and regression analyses. The records were obtained on 120 heifers at 14 months of age, from two genetic groups: 60 animals Braunvieh × (Santa Gertrudes × Nelore) and 60 animals Santa Gertrudes × Nelore. The genetic group significantly affected BW, CG and LMA. The estimates of phenotypic correlation between BW and HH, and between BW and CG were 0.49 and 0.79, respectively. The correlation between carcass traits and BW, CG and HH were of moderate to low magnitude, and between LMA and subcutaneous fat deposition were close to zero. All correlation estimates between MI and the others traits were negative and close to zero, except the correlation between MI and LMA, which was positive and high, as expected. Thus, the results of this study indicate that the genetic group with the greatest proportion of a continental breed genes showed higher LMA, BW and CG than the genetic group containing only genes of British and Zebu breeds. Furthermore, the growth traits are not good quantitative indicators of LMA and/or subcutaneous fat thickness, at least in phenotypic terms.

KEY WORDS: Body measurements, crossbreed, longissimus muscle area, morphologic traits, subcutaneous fat thickness.