G. J. Judson

Factors associated with low vitamin D status of Australian alpacas

OBJECTIVE To investigate factors associated with low vitamin D status of alpacas at pasture in southern Australia. DESIGN A 2-year survey of alpacas from two farms in South Australia and three in Victoria. Blood samples were collected from 20 to 30 alpacas on each farm on five occasions each year. Breed, gender, age and fleece colour of animals were recorded. METHOD Blood samples were assayed for plasma 2.5-hydroxycholecalciferol (25-OH D(3)) and plasma inorganic phosphorus (Pi). Data sets from 802 animal samples were analysed by multiple regression to determine variables associated with low vitamin D status of alpacas. The relationship between plasma 25-OH D(3) and plasma Pi was also investigated. RESULTS Vitamin D status was significantly affected by month of sampling, with low values in late winter and high values in summer. Plasma vitamin D concentrations increased with age, were higher in alpacas with light fleeces than in those with dark fleeces and were also higher in the Suri than in the Huacaya breed. Plasma Pi concentrations were generally lower in alpacas with plasma 25-OH D(3) values < 25 nmol/L. CONCLUSIONS Young alpacas with dark fleeces are most at risk from vitamin D insufficiency in late winter in southern Australia. The present study indicates that plasma Pi values are not a reliable indicator of vitamin D status of alpacas as assessed by plasma 25-OH D(3) concentrations.

Blood mineral, trace-element and vitamin concentrations in Huacaya alpacas and Merino sheep grazing the same pasture

We aimed to determine whether the concentration of minerals and trace constituents in blood of Merino sheep and Huacaya alpacas grazing the same pasture differed with species and time of sampling. Blood samples and pasture samples were collected at frequent intervals over a period of 2 years for mineral and trace-nutrient assay. The concentration of the minerals and trace nutrients in the grazed pasture usually met the dietary needs of sheep at maintenance, apart from potassium, sulfur, cobalt and Vitamin E in occasional samples. Restricted maximum likelihood mixed model analysis indicated a significant (P < 0.001) species by month by year interaction for all blood constituents assayed, a significant (P < 0.05) species by coat shade interaction for plasma Vitamin D, E and B12 and a significant (P < 0.001) species by month by Vitamin D interaction for plasma phosphorus concentrations. In general, plasma calcium concentrations were greater in sheep than in alpacas but plasma magnesium concentrations were greater in alpacas than in sheep. There was no consistent difference between the two species in plasma phosphorus concentrations although low values were recorded in individual sheep and alpacas. Plasma Vitamin D concentrations were more responsive to increasing hours of sunlight in alpacas than they were in sheep. Sheep had consistently higher concentrations of plasma copper, zinc and Vitamin B12 and higher concentrations of blood selenium but lower concentrations of plasma selenium and Vitamin A, than did alpacas. No consistent difference was observed between the two species in plasma Vitamin E concentrations.

Depot injection of barium selenate for long‐term prevention of selenium inadequacy in beef cattle

In southern Australia, cattle at risk from selenium (Se) deficiency can be given an oral dose of supplements that are effective in maintaining adequate Se status for between 9 and 12 months. The present study was undertaken to assess the duration of the effect of parenteral barium selenate (BaSe) in raising the Se status of cattle at pasture in an area of marginal Se deficiency. The BaSe was given subcutaneously to Hereford heifers, using an 18-gauge needle. Cattle had regular blood sampling to assay Se, from 8 days before dosing to 1155 days afterwards. Results show that a single injection of BaSe was effective in elevating blood and plasma Se concentrations to normal values for at least 2 to 3 years, when given to beef cattle of low normal Se status. We suggest that a prophylactic dosage of 0.5 mg Se/kg body weight as BaSe should be given every 2 years to prevent Se inadequacy in beef cattle grazing pasture of marginal Se content.

Evaluation of controlled-release devices for providing chromium sesquioxide and zinc in Huacaya alpacas at pasture: Evaluation of controlled-release devices for providing chromium sesquioxide and zinc in Huacaya alpacas at pasture

OBJECTIVE To assess the effectiveness of controlled-release devices (CRDs) for providing zinc and for estimating faecal output in alpacas and sheep at pasture. METHODS The study groups of 10 alpacas and 10 sheep at pasture were paired within species and allocated at random to receive by mouth either one CRD containing chromium sesquioxide designed to function for at least 21 days or two CRDs, one containing chromium sesquioxide and the other zinc oxide designed to release over a nominal 60-day period. Faecal concentrations of chromium, zinc and ash, blood and plasma concentrations of zinc and plasma activity of alkaline phosphatase (ALP) were measured over a period of 117 days after treatment. RESULTS The mean faecal chromium excretion profiles suggested that the CRDs performed in a similar manner in both species, releasing chromium for nearly 30 days in alpacas and for slightly more than 30 days in sheep. Using a common predetermined release rate of chromium from the CRDs, the daily faecal outputs of alpacas and sheep were estimated to be 0.54 kg dry matter and 0.33 kg dry matter, respectively. The CRD containing zinc oxide provided after 1 week an estimated daily release rate of 40 mg zinc with a lifetime of between 60 and 70 days in both species. The additional zinc did not elicit a response in blood zinc concentrations or in plasma ALP activity. CONCLUSION The CRDs were retained in the gastrointestinal tracts of the alpacas and sheep and both types functioned as expected. The CRD delivering chromium sesquioxide at a known release rate provided an estimate of faecal dry matter output over a period of almost 3 weeks and the CRD formulated to deliver supplementary zinc did so at the nominal release rate over a period of approximately 60 days in both species. These data indicated that the standard sheep CRD is applicable for use in alpacas.