Growing great two-tooths

By Rachel Joblin

In Livestock7 Minutes
A summer forage crop is a good option if faster growth is needed to reach the target two-tooth mating weight.

Producing a high-performing two-tooth generates significant value for the life of that sheep. The reality is a good two-tooth starts as a good ewe lamb and hogget.

What does experience tell us about getting a two-tooth flock that produces the maximum amount of lamb weight at weaning?

Setting liveweight targets and feeding to meet them is the foundation of sheep performance. With a target of 64kg at tupping time for a two-tooth, the monthly targets required to achieve this would look something like the table below for a traditional breed ewe. This is irrespective of whether ewe hoggets are put to the ram or not.

The targets are body weight – exclusive of wool and pregnancy-related weight. At mating ewes should be body condition score 3 or better. Hoggets should be 65% of their mature weight at mating time.

Weaning a good ewe lamb (over 28kg) makes reaching the targets more achievable.

What about keeping only twin-born ewe lambs? Ewes born and reared as twins may reach puberty at a similar age to single born lambs but at up to 3kg lighter. Research has shown that beyond hogget mating that bodyweight and condition score are more significant to achieving higher two-tooth scanning.

Breeding from well-grown hoggets provides benefits such as more lambs from the same number of sheep, faster generational turnover and the ability to use excess spring feed.

Massey University Professor Paul Kenyon’s research has demonstrated that ewes which showed hogget oestrus and/ or conceived have more lambs in their lifetime. The advantage may be up to 23 additional lambs/100 ewes over three matings, more than those that did not show oestrus as a hogget.

The potential 7.7 lambs/year/100 ewes is an opportunity that relies on achieving target liveweights and feeding through to two-tooth breeding.

As hoggets have less time between weaning and breeding as a two-tooth than mixed-aged ewes, consider weaning lambs at 60-70 days of age if lambs are 20kg or more. Hoggets under the target weight at weaning will have difficulty reaching target by two-tooth mating if fed poor quality summer pasture.

Gaining 10kg from weaning to two-tooth mating requires a growth rate of at least 120g/head/day. This is often difficult due to both the quantity and quality of feed available during summer and early autumn. If management practice is to run the two-tooths with mixed age ewes it is difficult to visually monitor the weight and body condition of the two-tooths during this time.

Utilise crop for improved growth

If faster growth is needed to reach the target two-tooth mating weight a summer forage crop should be considered. Some of the advantages of a crop include a bulk of feed, higher-quality feed, lower incidence of internal parasite larvae and toxins impacting ewe growth rates, health and fertility. Some client results have showed liveweight gains of 280g/ day are achievable on crop around mating time.

Does mating a portion of the lightest ewes on crop every year change how we plan and allocate crops?

Grazing out young sheep is an alternative. As well as ensuring you end up with a two-tooth that is up to weight it may provide the opportunity to divert the feed that they would otherwise have eaten to another class of stock. Depending on how the opportunity is used there may be a net zero cost or even better. Timing could be from weaning as a lamb and returning the following weaning, or in winter as a hogget and returning after weaning. This option comes into its own when there is no opportunity to grow crops on the home property, or it has unreliable growth patterns.

Two-tooth performance should not be affected by mating hoggets if they are well fed. Massey University has undertaken controlled studies that have shown either no effect or a positive effect on two-tooth breeding performance when two-tooths that lamb as a hogget are of a similar liveweight to those that did not lamb. The results highlight the importance of adequate feeding in pregnancy and lactation.

The potential performance of an animal is determined by its genetics. Management determines how the potential is expressed; ‘10% breeding, 90% feeding’ serves as a reminder that feeding and ewe condition are critical to getting the desired performance. Without a doubt top performance requires top animal health to support it. Create a robust annual plan, implement the plan, and modify it if your management changes.

To be a top performer requires more planning, monitoring and measuring, and reviewing.

Make a plan that allows flexibility around whether hoggets are mated and the subsequent feeding and weaning decisions. Set some lines in the sand about lamb growth rates and ewe condition as the driver of the weaning decision.

Select the best ewe lambs and prioritise feeding from when they are weaned until they are bred as two-tooths and you have the best chance of a great two-tooth entering your flock, whose potential lifetime contribution is maximised.

  • Rachel Joblin is an agribusiness consultant with BakerAg, Masterton.