Pasture intake and digestibility by young and non-breeding adult sheep: the extent of genetic variation and relationships with productivity

Abstract

The objectives of this study were to estimate the genetic variation in pasture intake and digestibility of the selected diet by young and by adult sheep, and to determine the genetic relationships between pasture intake and productivity traits. The pasture intakes of groups of young and adult sheep, each containing sheep from 11 bloodlines, were measured using the paired alkane technique. The wool grown, and its fibre diameter, over the intake measurement period were also estimated, as were liveweight and fat depth. Differences in pasture intake between bloodlines were largely related to liveweight in both groups of sheep, and were repeatable ( t=0.8) between the groups. The repeatability of wool growth and wool growth efficiency was a little higher ( t>0.9). Combining all the known estimates improved the precision of the genetic parameter estimates. The pooled estimates of heritability of DOMI, wool growth, wool growth efficiency and fibre diameter were 0.12±0.04, 0.37±0.05, 0.25±0.05 and 0.66±0.08, respectively. The genetic relationships of wool growth efficiency with wool growth and fibre diameter were 0.84±0.20 and −0.03±0.12, respectively, while those for feed intake (as DOMI) with wool growth and fibre diameter were −0.02±0.17 and 0.40±0.15.