Yearling mating management

On many farms in New Zealand, the reproductive performance of young hinds has been disappointingly low. This has largely been seen as high rates of non-pregnancy at scanning.

Why should mating management of yearling hinds differ from that of adult hinds?

One consideration often discussed during the 90’s was the possibility that young hinds are more prone to social stress during their first mating season, and considered as ‘shy breeders’ when confronted with aggressive adult stags. In reality, there is no strong evidence that this is the case and a large body of research points to the fact that a very high proportion of young hinds that fail to breed during their second year actually fail to reach puberty due to low body weight.

However, yearling hind mating systems do tend to differ to those of adult hinds due to perceptions around their social naivety and submissiveness. 

Don’t mix adult and yearling hinds for mating

There is evidence that yearling hinds are often aggressively dominated by adult hinds during the mating season, and occasionally pushed to the periphery of the hind group. This may make them more prone to be overlooked by the stags when they are in oestrus (heat). The easiest way to avoid issues around hind dominance hierarchies is to separate yearling hinds from adult hinds for mating. This is usually convenient for farmers anyway, as the younger hinds are generally already in a separate group over the previous calving period.

The yearling stag mating system

The most common mating system for yearling hinds is to simply join them with yearling stags generally at ratios of 1 stag: 8-12 hinds. The high ratio of stags is necessary due to their rutting naivety and generally lower libido than adult stags. Also, the joining dates are often in February, considerably earlier than for adult hinds and adult stags. This is seemingly to socialise the sexes before the onset of mating. Given that the young hinds do not have calves at foot, there are generally no problems with such early joining management. It is a very simple system.

But does it work? While there is no actual evidence that yearling stag mating systems actually improve pregnancy rates of yearling hinds, they are certainly no worse than for systems that use adult stags to cover yearling hinds.and generally easier to manage.

Using adult stags for mating yearling hinds

Some farmers have moved back to systems of joining yearling hinds with older stags with no apparent loss in pregnancy rates. The principles are much the same as for older hinds but with no mixing of the hind age groups.

Stags are joined at ratios of 1 stag: 35-45 hinds.

Why are yearling hinds later to conceive?

Generally, but not always, younger hinds conceive (and calve) 1-2 weeks later than adult hinds in any given year. We are not sure why this should happen. It may simply be a body weight effect. Smaller adult hinds generally conceive later than larger adult hinds.

However, there appears to be as much variation in conception dates amongst groups of yearling hinds as there is with adult hinds. Thus, there may be opportunities to select young hinds for early calving traits by foetal ageing, as is the case for adult hinds (see DEERSelect).