Sheep deficient in vitamin E preferentially select for a feed rich in vitamin E

Doraid Amanoel

Research output: ThesisMaster's Thesis

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Abstract

In Mediterranean environments, vitamin E deficiency is common in young weaner sheep during summer and autumn due to shortages of green feed. Vitamin E deficiency can cause diseases and death in severe cases. To rebalance vitamin E levels, it is possible to offer food rich in vitamin E such as saltbush. However, it is not known if the deficient animals will actively select the vitamin E rich food amongst other feed sources. It was hypothesised that sheep experiencing a vitamin E deficiency would voluntarily select more of vitamin E enriched feed compared with non-deficient sheep. Fifty six Dohne-Merino ewe lambs aged eight months, with an average live body weight of 37.5 kg, were selected. Two groups (n=28 per group) were constituted after a depletion/enrichment phase (40 days), one group with high concentrations of vitamin E (α-tocopherol) in the plasma and the other with low concentrations. In preparation for a 15 days preference testing phase, each group was randomly sub-divided into two sub-groups (n=14 per sub-group). Animals in the four sub-groups were presented a choice between pairs of vitamin E enriched and deficient feeds that were offered ad libitum. Each feed type was flavoured with either strawberry or orange so that the animals were able to learn to associate the vitamin E status of the feed with a particular flavour. The experimental design was balanced so that two sub-groups (high and low plasma vitamin E) were offered vitamin E enriched feed flavoured with strawberry and deficient feed flavoured with orange and in the other two sub-groups the flavourings were reversed. There was a significant three way interaction between the high and low vitamin E treatment groups × vitamin E content and type of flavour in the feed × time (days) suggesting that preference for vitamin E enriched feed with an orange flavour changed with time differently to the strawberry flavoured vitamin E enriched feed. Sheep with a vitamin E deficiency modified their relative intake and preferentially selected more of the vitamin E rich feed compared to non-deficient sheep. Self-learning by the low vitamin E group could explain that they overcame the aversive effect of the orange flavour to consume more vitamin E to compensate for the deficiency. The results of this study demonstrated that sheep deficient in vitamin E will voluntarily alter their preference over time and select for vitamin E rich feed, presumably to remediate the deficiency.
Original languageEnglish
QualificationMasters
Publication statusUnpublished - 2013

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