Inheritance of an in vivo leg conformation score in Texel lambs and its association with growth, ultrasonic measurements and muscularity

This study investigated the genetic relationships of in vivo measures of shape and muscularity with eight week weight, scan weight, ultrasonic measures of the depth of muscle (UMD) and fat (UFD) and body dimensions at twenty weeks of age. Data were recorded in two purebred Texel flocks that were managed in a common environment and selected for either lean tissue growth rate or conformation of the hind limb (LSC). A muscularity score (MUSC) was derived as UMD/body length. Estimates of direct heritabilities were 0.07, 0.19, 0.20, 0.32, 0.32 and 0.62 for eight week weight, scan weight, UMD, logUFD, MUSC and LSC respectively. Maternal genetic effects were not significant for logUFD, MUSC and LSC and were 0.10, 0.09 and 0.04 for eight week weight, scan weight and UMD respectively. The genetic correlation between LSC and MUSC was 0.61 and both traits tended to be negatively correlated with live weights (-0.09 to -0.36±0.17) and uncorrelated with logUFD. The heritabilities of body dimensions ranged from 0.11 for hook width to 0.55 for shoulder height and all measurements were strongly correlated genetically to scan weight (0.52 to 0.89). LSC was negatively correlated (-0.58) to shoulder height and body length. These results suggest that LSC could be used to select for improved muscularity in Texel sheep.