Australian Livestock Scanning Services Group

The results and recommendations from 23 years of on-property R&D with commercial sheep and cattle producers. We specialise in precision scanning for pregnancy, twinning, and ageing of foetus in sheep and cattle and in helping to raise lamb survival and cow fertility in stud and commercial breeding enterprises.

mob: 0428 667 567, email: fowler.doug@bigpond.com

20. Use hybrid vigour to increase lamb survival rates

When Merino ewes are mated to rams of different bloodlines, there may be hybrid vigour in the first cross progeny. The amount of hybrid vigour depends on a variety of factors, however, the performance of the first cross of the two bloodlines will be halfway between the performance of the two pure bloodlines if there is no hybrid vigour and greater than this where there is hybrid vigour.

The effect of hybrid vigour on fibre diameter and other wool quality traits is close to zero. However, for other traits the values are, fleece weight, 5%, body weight, 3%, and lambs per ewe mated, 7%.

What will be the outcome of changing to a new bloodline if the first cross progeny are 14% higher for lambs per ewe mated relative to the pure bred progeny of the present bloodline in the evaluation?

To calculate the outcome, reduce the 14% improvement in lambs per ewe mated by the level of hybrid vigor, 14% - 7% = 7%. Double this value to account for the situation when there has been a full infusion of the new bloodline and the final result is a 14% lift in lambs per ewe mated.

What will be the outcome of changing to a new bloodline if the first cross progeny are 7 % higher for lambs per ewe mated relative to the pure bred progeny of the present bloodline in the evaluation?

The calculations are simple (7% - 7 % = 0 %; 0 % x 2 = 0 %). Clearly there will be no improvement following the full infusion of the new bloodline.

What will be the outcome of changing to a new bloodline if the first cross progeny are 7 % lower for lambs per ewe mated relative to the pure bred progeny of the present bloodline in the evaluation?

Once again, the calculations are simple (-7 % - 7 % = -14%; -14 % x 2 = - 28 %. Clearly the effect of the full infusion of the new bloodline would be disastrous.

Hybrid vigour can be a powerful force to increase or even decrease the reproductive performance of sheep. Any infusion of a new bloodline to an existing bloodline needs to be evaluated and pregnancy scanning is an ideal way to quickly learn the benefits or otherwise of a move in this direction. ALSS will help you to implement an evaluation exercise.