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The effect of lupinosis on reproduction and wool growth of the merino ewe

Barnes, Anne LouiseORCID: 0000-0002-7227-230X (1993) The effect of lupinosis on reproduction and wool growth of the merino ewe. PhD thesis, Murdoch University.

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Lupinosis, a mycotoxicosis caused by phomopsins produced on lupin plants (Lupinus spp.) by Phomopsis leptostromiformis, is a disease of economic importance in W estem Australia. Preliminary studies and anecdotal reports indicated detrimental effects of lupinosis on reproduction and wool growth of ewes. The research described in this thesis was conducted to confirm experimentally the existence and magnitude of these effects on production, and to determine the stages of the reproductive cycle sensitive to phomopsin intoxication.

Mice were used to assess the effects of phomopsins on ovulation rate and on the early preimplantation embryo. Administration of phomopsins to female mice before ovulation reduced the number of mice mating and the number of embryos recovered. Culture of two-cell mouse embryos in medium containing phomopsins reduced the number developing to the blastocyst stage, with the embryos most sensitive to the effects of phomopsins before compaction and formation of the blastocoele.

Ovulation rate was depressed and wastage of ova was increased by the administration of phomopsins to ewes for 14 days before and 14 days after oestrus, resulting in 39 less lambs produced per 100 ewes than in the control groups.

The survival and growth of embryos/foetuses was reduced in ewes injected with phomopsins from approximately day 8 to 58 of pregnancy. Lamb marking rates were 10-20% less from phomopsin-treated ewes than from control ewes.

The wool production of ewes was significantly depressed by lupinosis. Length growth rate and mean fibre diameter were reduced after administration of phomopsins, and took up to 69 days to recover. The annual wool growth of the ewes was variable, and pregnancy and lactation reduced the quality and quantity of wool grown. There were reductions in clean fleece weight, yield, mean fibre diameter and staple strength, and changes in position of break attributable to administration of phomopsins.

Phomopsin intoxication significantly depressed the reproductive performances of ewes at all stages of the reproductive cycle examined, and reduced the quantity and quality of wool grown by the ewes.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): School of Veterinary Studies
Supervisor(s): Costa, Nick and Wales, Ray
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