Can we increase the proportion of female lambs by feeding oats at joining?

The proportion of female lambs was previously found to be higher when ewes were fed a diet based on oat grain and cottonseed meal (CSM) high in omega-6 fatty acids at joining. These results have now been confirmed in a number of studies, both with Border Leicester x Merino ewes and Merino ewes. The current paper presents results from the latest experiments conducted at the Wagga Wagga Agricultural Institute and further details of possible mechanisms underlying the observed effects. The time to lambing was significantly shorter when ewes were fed a diet high in omega-6 compared with omega-3 at joining. The shorter time to lambing appeared to be greatest when ewes were fed the high omega-6 diet both pre- and post-joining. In addition, the difference in the sex ratio between ewes fed a diet high in omega-3 or omega-6 fatty acids also appeared to be greatest when ewes were fed pre and post-conception. Additional research is required in order to determine the optimal amount of omega-3 or omega-6 to feed to ewes at joining in order to maximise the effect of maternal nutrition on the sex ratio of lambs.