Larger ewes may be desired by some breeders, but others are considering whether this increase in ewe mature size is detrimental to their flock, explains Signet breeding consultant Sion Parry.
This is particularly important as these large-framed animals tend to have higher feed requirements and increases in frame size may influence the ease with which prime lambs are finished.
There is no doubt performance recording has allowed pedigree sheep breeders to make substantial genetic gain in several commercially important traits, including growth rate.
However, as a consequence of the positive genetic relationship between lamb growth rate and ewe mature size, the size of the Texel ewes has tended to increase.
This is not solely due to the selection of faster growing lambs, breeders often select the largest stock ram at sales and there is a demand for larger ewes in some circles, particularly amongst those breeders aiming to breed ewes that will excel in the showring.
For those wishing to moderate mature size Signet provides a mature size EBV, based on weight measurements taken pre-tupping on shearling ewes.
This EBV allows information on ewe mature size to be used in breeding decisions, and will ultimately highlight ‘curvebender’ breeding lines – genetics for rapid lamb growth rates, but average ewe mature size. In commercial terms, where females are retained for breeding purposes – this could be a win-win situation.
Those breeders wishing to make use of the mature weight EBV should weigh shearling ewes pre-tupping and submit this information to Signet and, as with eight week weight and scan weight, shearling ewe weights can be allocated to different management groups.