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The effects of forage type and antagonists on copper metabolism in sheep

Hussein, A.A. (2017) The effects of forage type and antagonists on copper metabolism in sheep. Doctoral thesis, Harper Adams University.

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Abstract

Three in vivo and two in vitro experiments were carried out to investig ate the effect of forage type and dietary antagonists molybdenum (Mo) and sulfur (S) on Cu metabolism in sheep. In experiment 1, dried grass pellets or maize silage without or with added dietary Mo and S were fed to Texel growing lambs to investigate the e ffect of forage type and antagonists on Cu status and performance. The maize silage fed lambs had a higher weight gain and rumen pH , but a lower liver Cu concentration compared wit h the dried grass pellets fed lambs. The addition of antagonists significant ly reduced liver Cu status, but blood Cu parameters were not affected by dietary treatment. In experiment 2, grass haylage vs. maize silage were used to investigate the effect of forage type and antagonists on Cu metabolism in Swaledae growing lambs. The m aize silage fed lambs had a higher weight gain and liver Cu status but a lower rumen pH compared w ith the grass haylage fed lambs . Liver Cu status, Pl - Cu concentration, and Cp activity were decreased by the inclusion of Mo and S, while Cp: Pl - Cu ratio was n ot aff ected by antagonists. In experiment 3, the involvement of the rumen digesta fractions on Cu metabolism in forages used in experiment 1 and 2 plus grass silage was investigated. Cu, Mo, and S were found mainly (above 85%) associated with the solid pha se of the fermented rumen digesta, at the expense of supernatant fraction . Additional Mo and S significantly reduced Cu distribu tion in the supernatant fraction due to increasing Cu inc orporation into the solid phase. In experiment 4, the effect of forage preservation on rumen pH and their interaction between Cu and antagonists we re investigated. Rumen pH in grass silage fed lambs tended to be lower compared with lambs fed other forages. Lambs fed urea and fermented WCW were heavier than lambs fed grass sil age. Liver Cu status was higher in lambs offered urea WCW or grass silage compared with fermented WCW. Additional antagonists substantially reduced liver Cu status, but had a small effect on blood Cu par ameters. N o effect of Cu antagonists were observed on liver Cu retention in lambs fed fermented WCW, whereas they significantly reduced liver Cu retention in lambs on urea WCW and grass silage. Blood Cu parameters were slightly affected by dietary treatment. In experiment 5, the effect of preservation of fre sh grass as hay or silage on Cu distribution in rumen fluid following in vitro fermentation was investigated . Preservation of fresh grass as hay or silage had no effect of Cu distribution in the fermented rumen liquor or after pepsin - HCl digestion. These s eries of studies showed the effect of forage type on Cu metabolism. In addition, it confirms that dietary Mo and S are potent Cu antagonists and this potency may be reduced at a lower acidic rumen environment.

Item Type: Thesis (Doctoral)
Divisions: Animal Production, Welfare and Veterinary Sciences
Depositing User: Ms Kath Osborn
Date Deposited: 22 Aug 2018 15:19
Last Modified: 22 Aug 2018 15:19
URI: http://hau.collections.crest.ac.uk/id/eprint/17322

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