The development of intraruminal boluses for cattle and sheep

Lawson, Donald C. (1992) The development of intraruminal boluses for cattle and sheep. PhD thesis, University of Glasgow.

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This thesis is principally concerned with the construction and development of a sustained release bolus system supplying a range of trace elements to ruminant livestock. The system is a patented invention of the University of Glasgow.

Section 1 describes the technology of construction. A compressed mixture of common inorganic salts in cylindrical form (25 mm diameter, 40-100 mm length) is coated by dipping in a polyester resin leaving one flat end uncoated. Release of material into the reticulo-rumen is partly by dissolution and partly by mutual erosion of two boluses administered together. The initial prototype contained copper oxide, manganese sulphate, zinc oxide, zinc sulphate, sodium selenite, cobalt sulphate and potassium iodide with Vitamins A, D3 and E.

Section 2 presents results of the examination of a range of factors which might affect the rate of release of nutrients from the bolus. These included the number of coats of resin and the initial length of the bolus. The compositional specification of zinc oxide (a major ingredient) was found to be of great importance and strict control was necessary to produce the required overall release rate. Changes in the inclusion of zinc sulphate could also markedly affect the dissolution/erosion characteristics. An increased number (1-3) of boluses simultaneously administered and the presence of metallic residues (end weights, tubes, cylinders) from other bolus systems was demonstrated to greatly increase the rate of release of material from the bolus.

Section 3 describes a series of trials at different sites with grazing cattle judged by the local veterinary surgeons to require supplementation with one or more of the trace elements. The adequacy of supplementation was assessed by the measurement of blood parameters in comparison with untreated animals and/or animals given alternative supplementation as injections or alternative boluses. It was concluded that the bolus system provided adequate copper and selenium to cattle (130-500 kg liveweight) as judged by the responses in plasma copper and glutathione peroxidase activity and that these responses were as favourable as those found by injection of copper and/or selenate containing products. No sound conclusions regarding the effectiveness of the bolus system in supplying cobalt could be made due to the possible limitations of the assay method (and its interpretation) for Vitamin B12. There were no indications of cobalt inadequacy in the cattle.

Section 4 of the thesis examined the possibility that the bolus construction with a modified matrix might be capable of providing a constant release of a variety of medicaments. Limited exploratory trials were conducted to examine the possible inclusion of materials such as levamisole hydrochloride, ivermectin, oxfendazole, laidlomycin propionate and Vitamin E. Distinct possibilities were found but much further work would be required to establish formulations giving appropriate and constant release of materials in the normally accepted therapeutic range.

Section 5 examined the possibilities for the development of a comparable, but smaller (19 mm diameter) bolus appropriate for use in sheep. Regurgitation was a major problem but was effectively eliminated by increasing the overall density to 3.0 g/ccm. The cost of manufacture would be such as to allow the use of only a single bolus. The absence of loss by mutual erosion between two boluses was found to lead to little further weight loss in prototypes after about 60 days. Nevertheless, analyses of faeces and of livers recovered at slaughter demonstrated the effectiveness of the copper contained in the bolus. These were such as to give concern about the possibility of potential copper toxicity.

In Section 6 an assessment was made of the effectiveness of a high density carbo-wax matrix as a carrier for avoparcin in an alternative bolus system. Comparisons were made by evaluation of the avoparcin concentrations in faeces with that resulting from a constant daily in-feed addition of avoparcin. Assessment of faecal output indirectly by estimation of the chromium content of faeces resulting from constant addition of the inert marker to the constant diet given to all cattle showed the experimental bolus construction to be irregular and erratic in relation to the direct inclusion in feed.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Subjects: S Agriculture > SF Animal culture > SF600 Veterinary Medicine
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Biodiversity, One Health & Veterinary Medicine
Supervisor's Name: Ritchie, Dr. N.S.
Date of Award: 1992
Depositing User: Mrs Marie Cairney
Unique ID: glathesis:1992-40918
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 10 Jan 2019 13:04
Last Modified: 10 Jan 2019 13:04

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