Estimation of genetic and phenotypic parameters in a closed ...

51
to phenotypic correlations in most cases although the genetic correlations
were higher. Several values outsíde the theoretical range (rG , 1 o,
tG ' - 1) were found, i.e. mid-back fat with shoulder fat, loin fat
and total fat, carcass length with loin eye area, grade índex with three
back faË thickness measurenents and total fat thickness and loin eye
area' mid-back fat with percent predÍcted yíeld.
coefficients are high in standard error.
Most genetic
The back fat thÍckness measurements at three different points were
highly positively correlated with each orher. A si_milar finding has
been reported by smith et a1. (L962). selection for 1or¿er back faË
thickness at one location will reduce thickness at other areas and
average back fat.
Carcass length had moderately negative correlations with shoulder
fat, loÍn faÈ, total fat and age to markeË weight. The correlations
betr¿een carcass length and ham surface area and percent predicted yield
were highly negarive. snith er a1. (Lg62), smith and Ross (1965),
Jensen et al. (1967), Flock (L970), siers and Thomson (L972), Enfield
and I^Ihatley (1961) and Roy eÈ a1. (196g) also showed that negarive
correlatÍons existed between carcass length and carcass back fat and
percent lean cuts. Loin eye area was positively correlated Ì,¡ith loin
fat which suggested that selection for lower back fat at loin would
reduce loin eye area simultaneously. This result is not in agreement
wÍth reports from previ-ous research.
Percent han weight \474s negatively correlated with a1l three back
fat thickness measurements and 1oÍn eye area and the values ranged from
medium to hÍgh, but it was positively correlated with ham surface area,