Increasing the proportion of female lambs by feeding Merino ewes a diet high in omega-6 fatty acids around mating

E. H. Clayton, M. A. Friend, J. F. Wilkins

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6 Scopus citations

Abstract

In previous experiments, the proportion of female lambs was higher when BL × Merino ewes were offered a diet high in omega-6 (n-6) than when offered one low in n-6 around joining. The aim of the current study was to determine whether the proportion of female lambs increases when Merino ewes are fed a diet high in n-6 and to further test the effect of time of feeding relative to mating. Ewes were fed a low n-6 (ryegrass silage) or high n-6 (oats and cottonseed meal) diet for ∼40 days pre-mating or 40 days pre- and 17 days post-mating. Liveweight, fat score, plasma fatty acid status and lamb sex were determined. The concentration of plasma n-6 was higher (P < 0.001) and the time to oestrus shorter (P < 0.001) when ewes received the high n-6 compared with the low n-6 diet. The proportion of female lambs was higher when ewes were fed the high n-6 compared with the low n-6 diet either pre-mating only (71.3% vs 48.7%, P ≤ 0.017) or both pre- and post-mating (69.6% vs 37.3%, P < 0.001). The sex ratio differed from an expected 50:50 when ewes were fed the high n-6 diet (P < 0.001), but not the low n-6 diet (P ≤ 0.223). The effect of the high n-6 diet on the sex ratio of lambs in Merino ewes may act pre-conception, as the effect of the diet was not greater when ewes were fed both pre- and post-mating. Altering diet to increase female lamb proportions may be economically viable to producers of first-cross ewes.

Original languageEnglish
Pages (from-to)1174-1184
Number of pages11
JournalAnimal Production Science
Volume56
Issue number7
DOIs
StatePublished - 2016
Externally publishedYes

Keywords

  • conception
  • mating
  • omega-3
  • plasma fatty acid
  • sex ratio
  • time of joining

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