An evaluation of a slow release trace element fertiliser for the prevention of copper deficiency in sheep

Forsyth, Wilson M (1989) An evaluation of a slow release trace element fertiliser for the prevention of copper deficiency in sheep. PhD thesis, University of Glasgow.

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Copper (Cu) deficiency in ruminants continues to be a common trace element disorder in Great Britain despite the fact that its existence was first recognised over 50 years ago. As the direct treatment of animals is demanding, the convenience and simplicity of a soil treatment to raise herbage Cu status is an attractive proposition. However previous studies have indicated that soil application of Cu compounds although increasing plant uptake of Cu were seldom dependable in overcoming long term livestock deficiencies. The objective of this work was to evaluate a novel slow release trace element fertiliser (Cu fertiliser) for the prevention of Cu deficiency in sheep. The Cu fertiliser is an unrefined and unprocessed byproduct of the brass manufacturing industry and is not a specially formulated fertiliser. Chemical and physical characterisation of the Cu fertiliser have shown that it contains approximately 2% Cu which is distributed throughout a wide particle size range. In addition the Cu fertiliser is only sparingly soluble in water. The characterisation studies suggested that the Cu fertiliser when applied to soil should act as a slow release source of Cu to plants. The fertiliser was also found to contain zinc, lead, iron, cadmium, nickel and manganese. Application of the Cu fertiliser, both incorporated into the soil and broadcast onto an established sward increased herbage Cu concentrations. Both pot and field trials showed that increasing the Cu fertiliser application rate produced significant increases in herbage Cu concentraton. A similar effect was shown for zinc. These increases were not accompanied by detectable increases in herbage Pb, Fe, Cd, Cr, Ni or Mn concentrations. In the case of the field trial these results were maintained in three successive years after a single application in December 1985. Glasshouse pot trials showed that lowering the soil pH caused significant increases in herbage Cu concentrations of supplemented soils. These results were not repeated in the field. The increased herbage Cu concentrations in the pot trials occurred on four different soil types. Waterlogging had no effect on the rate of release of Cu from the fertiliser. In a field trial with ewes and lambs grazing a sward with known low Cu availability a single application of the Cu fertiliser (370 kg/ha) was successful in raising and maintaining plasma Cu concentrations above the deficiency threshold in ewes throughout pregnancy, lambing and weaning, and in their lambs. The single application elevated plasma Cu concentrations within six weeks and was effective for two years, during which time its effect was comparable to two annual oral administrations of Cu needles. In the third year the mean plasma Cu concentration of ewes on treated pasture, although still higher than that of the control ewes, dropped below the deficiency threshold. Tissue analysis from dead ewes in the second year of the trial showed that ewes on the Cu fertiliser treated pasture had a much higher Cu concentration in their liver than those on untreated pasture. Herbage analysis from the animal response trial showed Cu concentrations above the phytotoxic threshold and up to ten times those found in pot and herbage trials in the first 6 months after application of the Cu fertiliser. These data suggested that the Cu fertiliser was contaminating the herbage and was thus available for ingestion. Lead adherence and ingestion trials demonstrated that the Cu fertiliser can adhere to herbage and when ingested by sheep at 10 g/day does increase plasma Cu concentrations without any known deleterious or toxic effects on the animal. A second field trial using a lower Cu fertiliser application rate (250 kg/ha), and hence reducing the potential for surface adherence, resulted in a comparable increase and maintenance of the plasma Cu concentrations of sheep grazing the treated pasture to that found in the first trial. The replacement of the 20 sheep originally on the treated pasture by 20 new sheep, one year after the Cu fertiliser application also resulted in an increase in their plasma Cu concentrations.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Animal diseases.
Colleges/Schools: College of Medical Veterinary and Life Sciences
Supervisor's Name: Smith, Dr. C.A. and MacPherson, Dr. A.
Date of Award: 1989
Depositing User: Enlighten Team
Unique ID: glathesis:1989-72643
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 11 Jun 2019 11:06
Last Modified: 15 Jun 2021 15:37

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