Increasing male lamb proportion by feeding ewes omega-3 fatty acids

Summary

Objectives of the project
To determine whether the proportion of female lambs was higher when Border Leicester x Merino ewes or Merino ewes were fed a diet high in omega-3 or omega-6 fatty acids and to determine whether the effect was greater when ewes were fed either pre or post-conception and whether these effects carry over into the second generation.
Methods
The project involved a series of intensive pen feeding studies with Border Leicester x Merino or Merino ewes and on-farm demonstration trials.  Ewes were fed a diet high in either omega-3 or omega-6 for 6 weeks pre-conception only or 6 weeks pre and 17 days post-conception.  Maiden ewes bred from Merino ewes were also fed omega-3 or omega-6 to determine the intergenerational effects of these diets.  Plasma fatty acids, the time to oestrus and joining as well as the sex ratio of lambs was determined.
Results
The proportion of female lambs was 14% higher when ewes were fed a diet high in omega-6 fatty acids both pre- and post-conception.  The time to oestrus and parturition was shorter when ewes were fed the High omega-6 diet.  The concentration of progesterone was lower when BL x Merino ewes, but not Merino ewes, were fed the High omega-6 diet.
Conclusions
Producers requiring high value breeding females may benefit from feeding omega-6 at joining, whereas those requiring males for meat production may benefit from feeding omega-3