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Monday, August 29, 2011

Diet may affect sex of lambs


Diets with more omega-6 fatty acids increase the number of female lambs from sheep.
Research at Wagga Wagga revealing diet may affect the sex ratio of lambs by up to 15 per cent may lead to a breakthrough in sheep reproduction, NSW Department of Primary Industries (NSW DPI) research leader Dr Ed Clayton said today.

“The results are the exciting culmination of a number of years work and have the potential to change the way producers' manage reproduction in ewe flocks,” Dr Clayton said. 

The research, which is being carried out through the EH Graham Centre, an alliance between Charles Sturt University (CSU) and NSW DPI, recently received a funding boost of $310,000 from Meat and Livestock Australia across a two-and-a-half year period.

The research is being undertaken by CSU PhD student Catherine Gulliver and involves the study of the ratio of omega-3 and omega-6 fatty acids in the diet of ewes and the effect it has on the sex ratio of lambs.

Ms Gulliver is the recipient of a scholarship from the Australian Postgraduate Award scheme and the Future Farm Industries Cooperative Research Centre. 

Dr Clayton said the research was conducted in open-air pens at the Wagga Wagga Agricultural Institute and involved 300 first-cross ewes split into two groups.

“The first group was fed omega-6 sourced from oat grain (now fondly referred to as 'grain for girls') and the second group was fed omega-3 sourced from a diet of pea silage,” Dr Clayton said.

“Ewes were fed the two diets for six weeks prior to joining to Dorset rams and three weeks after joining. 

“After lambing, the lambs were tagged, and we identified a 15 per cent increase in the number of female lambs from sheep fed high omega-6 (grain) compared with those fed high omega-3 (pea silage) diets. 

“We were very surprised that the different diets could have such a profound influence on the sex of lambs.

“For a self-replacing ewe flock or for first-cross ewe breeders, to increase the number of female lambs relative to the number of male lambs, a diet high in omega-6 could be fed at joining. 

“Alternatively, if producers wanted more male lambs (castrated male lambs develop more quickly and have more muscle) for prime lamb production systems, they might consider feeding a diet high in omega-3 at joining.”

Dr Clayton said a further trial now underway, involving 300 first-cross ewes and 320 Merinos, focuses on whether the skewing effect was pre or post-conception and if the effect is similar in first-cross ewes and Merinos.

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