Estimates of genetic parameters in turkeys. 2. Body weight and carcass characteristics

Data were taken from 1,088 individuals--504 females (F) and 584 males (M)--produced by 34 sires and 168 dams from a randombred control line (RBC2) of turkeys maintained at the Ohio Agricultural Research and Development Center, Wooster, OH. Turkeys were used to estimate genetic and phenotypic parameters among 16-wk body weight and a number of body composition characteristics. Heritabilities (h2) were estimated from sire components of variance for 16-wk weights of muscles of breast (BM: F = .08, M = .35); thigh (TM: F = .12, M = .17); and drum (DM: F = .30, M = .44); weights of leaf fat (LF: F = .13, M = .51) and total abdominal fat (AF: F = .21, M = .55); and total percentage carcass fat (%F:F = .06, M = .24), percentage protein (F = .07, M = .20), and percent moisture (F = nonestimable, M = .11). The h2 of percentage carcass ash was nonestimable from both data sets due to negative estimates of the sire variance components. Due to the non-normal distributions of some of the fat measures, the fat measure data were converted to natural logarithms. Genetic estimates from the transformed data were similar to those from the nontransformed data. Genetic correlation (rG) estimates indicated a positive genetic association between body weight (BW) and all the fat characteristics measured. The BW was highly correlated with BM (F = .48, M = .86), TM (F = .81, M = 1.01), and DM (F = 1.04, M = .70). However, BW was correlated to a lesser degree with LF (F = .02, M = .27), AF (F = .25, M = .32), and %F (F = .93, M = .50). The BM was only moderately correlated with TM (F = .43, M = .28) and DM (F = .73, M = .27). The TM and DM were highly correlated (F = 1.02, M = .84). The existence of these correlations, which are less than unity, indicate that selection for BW alone will lead to increasing levels of fat in commercial turkeys, and to disproportionate increases in breast vs. leg muscles.