Glass Bolus Research Articles

Effect of pre and postpartum maternal supplementation of zinc and selenium via slow-release glass bolus or the element salts on feed intake and some blood parameters in ewes and their lambs

In late pregnancy and early lactation, ewe's demand increases for zinc (Zn), and selenium (Se) for scavenging of free radicals and due to transfer via placenta, colostrum or milk to lamb.This experiment was conducted to study the effect of slow-release bolus of Zn and Se on performance, and some blood parameters of pregnant ewes in the last third of pregnancy, and early lactation as well as their lambs. Twenty-one ewes were estrus synchronized in the breeding season by intra vaginal insertion of sponge containing medroxyprogesterone acetate. Forty-five days before the expected date of parturition, the pregnant ewes (3–4 years old and 55±5.2 kg in weight) were randomly assigned to one of the three groups: 1) control, 2) slow-release glass bolus with mean release of 20 mg Zn and 0.2 mg Se per day (Bolus), and 3) 20 mg Zn and 0.2 mg Se per day as sulfate and selenite, respectively via Daily feeding (Daily). Blood samples were obtained from ewes at 105th and 135th days of pregnancy, at parturition and 15th day postpartum and from lambs at 15 days of age. The results indicated that total feed intake of ewes increased (P = 0.03) in the Bolus and Daily groups than control. Supplementation of Zn and Se in both methodssignificantly increased Total Antioxidant Capacity (TAC) in the ewesand their lambs than the control group. Compared with the control, there was higher triiodothyronine (T3) in ewes and their lambs and lower tetraiodothyronine (T4) only in lambs in Bolus and Dailygroups. Increased T3 to T4 ratio in ewes (at days 135 of pregnancy and at parturition) and their lambs was recorded in Bolus and Daily than the control group. An increased level of alkalinephosphatase (ALP) in ewes was observed in the Bolus and Daily groups compared with the control. Alanine amino transferase (ALT) activity on day 135 of pregnancy was significantly reduced by Zn and Se supplementation in both methods. Bolus and Daily groups of ewes had lower creatinephosphokinase (CPK), and their lambs had lower aspartate amino transferase (AST), ALT, CPK, and gamma-glutamyltransferase (GGT) than the control group. Regardless of the supplementation method, Zn and Se increased glucose (P = 0.02) and decreased triglyceride (P = 0.06) in ewes. In the ewes supplemented with Zn and Se, creatinine concentration significantly decreased in parturition day compared to control. Total protein, albumin, globulin and ratio of albumin to globulin in ewes and their lambs were not different between treatments. As a result, Zn and Se improved antioxidant status and some blood parameters in ewes and their lambs. Efficacy of slow-release bolus of Zn and Se was similar with daily feeding of these elements.

The trace element and humoral immune response of lambs administered a zinc, cobalt and selenium soluble glass bolus

Zinc, cobalt and selenium are essential trace elements for ruminants and all have roles in immune function. The delivery of these elements to grazing livestock can be problematical.The aim of this trial is to determine the effect of the administration of an intraruminal soluble glass bolus to supply zinc, cobalt and selenium to growing lambs at pasture and to determine the effect on humoral immune response via the administration of a novel keyhole limpet haemacyanin (KLH) antigen.On days 0, 17 lambs each had a zinc (15.1% w/w), cobalt (0.52% w/w) and selenium (0.15% w/w) soluble glass bolus (∼33g) administered (bolused), whilst the 17 lambs received no bolus (control). All of the lambs were grazed together throughout the trial. Trace element status (selenium—erythrocyte glutathione peroxidise activity; cobalt—serum vitamin B12 concentration; zinc—plasma zinc concentration) and live weights were assessed on days 0, 20, 42 and 63, with immunisation with KLH on day 34 and assessment of IgG response by direct ELISA on days 20, 42, 49, 63. Lambs were slaughtered when commercially fit on either day 86 or 121 and livers analysed for copper and zinc concentrations and boluses recovered from the bolus group to assess dissolution rates.The bolused lambs had significantly increased serum vitamin B12 concentrations (p<0.001) and erythrocyte glutathione peroxidase activities (p<0.001) on all post-bolusing samplings. The bolused lambs had higher plasma zinc concentrations on day 42 (p<0.05) and day 63 (p<0.01). The humoral immune response was enhanced with the bolused lambs having significantly greater anti-KLH IgG levels on day 42 (p<0.05) and day 63 (p<0.01), although the two groups had a similar maximal value at day 49. There was no significant effect of the bolus on live-weight or liver zinc concentrations. The average bolus dissolution rate of the recovered boluses was 326mgglass/d (s.d.±30mg/d) giving a mean daily release of 49.3mg zinc, 1.7mg cobalt and 0.5mg selenium. The pasture mineral status was not assessed, but the bolus alone was able to fulfil recommended intake requirements for the elements.In conclusion, administration of a zinc, cobalt and selenium soluble glass bolus resulted in an increased antibody response and fulfilled the daily requirements for cobalt, selenium and zinc with an elevated status of these elements compared to unsupplemented controls grazing the same pasture.

Selenium profile in blood plasma of grazing sheep: A case study in specific ranch in Punjab, Pakistan

A survey was conducted in Southwestern, Punjab, Pakistan during two different seasons to assess the status of selenium of three different classes of grazing sheep. Blood plasma from lactating, non-lactating and male sheep were collected four times monthly in winter and summer seasons and analyzed for selenium concentration. Seasonal variations were found for plasma selenium concentration. Selenium concentration of plasma was higher in male sheep than those lactating and non lactating ewes during both the seasons as well as it were higher compared to the established critical value for blood plasma selenium for these ruminants. High incidence of deficiencies was found particularly for lactating ewes. These deficiencies in plasma selenium based on critical level were 35% to 15 % for lactating, 28% to 12% for non lactating ewes and 15% to 5% for male animals during winter and summer seasons, respectively. Although some differences among the three classes of sheep were found for selenium concentrations of blood plasma, but dramatic class differences could not be concluded based on this study. It was suggested based on the results obtained, pellets, glass bolus or mixture that contain selenium, should be used for supplementation for grazing sheep in the study area to maintain the plasma Se at optimum required level for the prevention of complication in livestock caused due to deficiency of this element.

The effect of a copper, selenium and cobalt soluble glass bolus on the trace element status of Bactrian camels

The effect of a copper, selenium and cobalt soluble glass bolus on the trace element status of Bactrian camels

Effect of a Copper, Selenium and Cobalt Soluble Glass Bolus Given to Grazing Yaks

Two field trials were carried out to evaluate the performance of a soluble glass copper, cobalt and selenium bolus for maintaining adequate levels of the three trace elements in yaks. Forty yaks were used in trial 1 and 60 yaks were used in trial 2. In each trial two commercial soluble glass boluses were administered to half of the yaks. Blood samples were taken from the jugular vein at day 0, 30, 60, 90 in trial 1 and at day 0, 45, 75 and 105 in trial 2. The samples were analysed for copper status (serum caeruloplasmin activity and copper concentration), cobalt status (serum vitamin B 12 concentration and cobalt concentration), selenium status (erythrocyte glutathione peroxidase activity and selenium concentration) and serum zinc concentration. The erythrocyte glutathione peroxidase activities, serum caeruloplasmin activities and serum vitamin B 12 concentrations for trial 1 and 2 were all significantly increased for the bolused yaks (p<0.001 or p<0.01) on all sampling days. The bolused yaks had a significantly higher selenium and copper status in serum than the control yaks on all sampling days in trial 1 and 2 (p<0.05 or p<0.01). There were no significant differences in zinc and cobalt concentrations between the bolused yaks and the controls.

Effect of soluble glass bolus administration on the blood selenium concentration in grazing Philippine goats under backyard conditions

ABSTRACTThe present study was conducted to determine the effects of selenium (Se) soluble glass bolus (SGB) on blood Se concentrations of mixed‐bred (native × Anglo Nubian) pregnant does weighing between 15 and 52 kg and grazing on natural pastures in the Philippines. The control group, consisting of 28 does, was not administered with SGB, while 23 does were administered with SGB every 6 months for a period of 12 months. Forage and blood samples in both groups were collected every 2 months. Their Se, sulfur, calcium, phosphorus, magnesium, copper and zinc concentrations were analyzed using the wet digestion method. The results showed that the grazed forage had concentrations of all these minerals that were far higher than the accepted critical lower levels. The Se concentration was higher (P &lt; 0.05) in the dry season than in the rainy season, especially in the whole blood collected from the does and newborn kids. In both groups the Se concentration in the kids tended to increase during the suckling period but decreased after weaning. Kids born to the SGB does had higher whole blood Se concentrations (P &lt; 0.05) than those born to the control does. However, the administration of SGB to the does did not affect any blood mineral concentrations except for Se in the grazing does and their kids. The animals did not exhibit any clinical signs of mineral deficiencies or toxicities during the experimental period.

Studies on rickets and osteomalacia in Bactrian camels ( Camelus bactrianus)

Epidemiological studies have indicated incidences of 32.9% and 27.8% for rickets and osteomalacia, respectively, in Bactrian camels ( Camelus bactrianus), but there is an increased incidence under drought conditions, sometimes reaching 75%. We have found that concentrations of phosphorus and copper in forage and soil samples in a drought affected area were significantly lower than in a control area or normal reference values ( P<0.01); the mean Ca:P ratio in the forages was 50:1. The phosphorus content of blood and hair from affected camels was significantly less than that in controls ( P<0.01) and concentrations of copper in the liver and kidney were significantly lower in affected camels than control animals ( P<0.01); the concentrations of triiodothyronine (T 3), thyroxine (T 4) and parathyroid hormone (PTH) in the serum from affected animals were significantly higher than those from healthy controls ( P<0.01); serum inorganic phosphorus and ceruloplasmin levels were lower than those in the controls ( P<0.01 or P<0.05); the concentrations of serum α-globulin and β-globulin were significantly higher in the affected camels than in the healthy controls ( P<0.01). The pathological changes seen in camels affected with rickets included porous, brittle, light, osteoporotic bones that were susceptible to fractures and had less resistance to cutting and sawing. Wrist joints were enlarged with an apparent bowing of the long bones in forelimb and with typical broadening of the epiphyses. In adult female camels, many enlarged scars were often seen in ribs indicating earlier fractures. The disease could be cured with supplementary bone meal, phosphate or mineral mixtures and in field investigations clinical signs disappeared within 15 days. Over the same period, the concentrations of phosphorus and alkaline phosphatase in blood returned to normal. The disease may be effectively prevented by use of mineral blocks (block salt licks) or dosing orally with copper, selenium and cobalt soluble glass boluses. We conclude that rickets and osteomalacia are mainly caused by phosphorus and copper deficiencies in the pasture.

Effects of three types of trace element supplementation on the fertility of three commercial dairy herds

The effects on the fertility of three commercial dairy herds of three types of copper- and seleniumcontaining mineral supplements was investigated. As the cows on each farm were dried off...

Effects of concentrate supplementation on blood mineral concentration of growing upgraded Philippine goats

ABSTRACTA total of 32 4‐month‐old‐upgraded Philippine goats with mean bodyweight of 13.5 kg were used to study the effects of concentrate supplementation on mineral status of growing goats. All animals received a basal diet comprised of different forage species. Twenty of the animals were supplemented with concentrate at a rate of 150–200 g dry matter/day while the remaining 12 animals were not supplemented. Blood sampling and bodyweight measurement were done every 2 weeks during the 5 months of experiment. Forage, concentrate and blood sulfur, calcium, phosphorus, magnesium, copper, zinc and selenium concentration were analyzed after wet digestion. Forage mineral contents, except for zinc and selenium, were sufficient for requirements of ruminants. Concentrate mineral contents were much higher than the requirements, but did not exceed the toxic levels. The concentrate supplementation resulted in high (P &lt; 0.05) plasma phosphorus, copper, zinc, whole blood selenium concentrations and bodyweight of growing goats, although some supplemented animals showed plasma zinc concentration below the lower critical level. It was recommended that pellets, glass bolus or capsules that contain deficient minerals, such as zinc and selenium, should be used in the study area.

The Effect of Cosecure® Supplementation on the Copper Status and Fertility of Grazing Holstein – Friesian Dairy Cattle

There are several studies concerning the relationship between copper status and the amount of molybdenum, sulphur in the diet ( Phillippo et al. 1987; Bremner et al. 1987; Hurley and Doane,1989; Moeini et al.1997; Mackenzi et al. 1998).These studies attempted to explore how copper deficiency influences the reproductive performance. The purpose of this study was to examine the effect of copper supplementation by means of a slow release soluble glass bolus (Cosecure) on the trace elements status and fertility of dairy cattle. Seventeen cows were bolused with two Cosecure boluses (Telsol Ltd.) while the remaining fifteen cows were unbolused (Control). The cattle were grazed at pasture, which has been shown to have high level of molybdenum (2.6 -3.2 mg/kgDM). Blood samples were taken monthly (for six months) to measure trace element status and detailed records of fertility were also maintained. Herbage samples were obtained throughout the grazing period and analysed for mineral Mo, Fe, S and Cu content by Inductive coupled plasma (ICP) and atomic absorption (AA) after wet digestion with nitric acid MAFF(1986). Trace element status was determined by the methods outlined by Mackenzie et al.(1996). Statistical analysis of the results was carried out using student T test and analysis of variance (GLM). The result showed that although in the cows given copper supplementation, the blood copper concentrations increased in comparison to the control groups but all the cows were in the normal range (>12 μmol/l). The blood copper concentrations were lower in both groups at grazing time with marked differences between plasma copper and TCA copper plasma indicating the extent of copper thiomolybdate production. Although the plasma copper, caeruloplasmin and super oxide dismutase activities were higher in treated cows until day 100, and bolused cows had significantly greater plasma copper on day 30 and 60 (p 2 g/kgDM) occurring during grazing time affects the animal copper status and reduces copper availability through the production of thiomolybdate in the body. The effect of Cosecure was likely to be due to the slow release of copper to stop thiomolybdate toxicity.

Effects of Intraruminal Soluble Glass Bolus on Blood Selenium and Plasma Mineral Level of Grazing Does under Backyard Conditions in Selected Areas in Nueva Ecija, Philippines

Soluble glass bolus with selenium (Se), copper (Cu) and cobalt (Co) was administered intraruminally to Philippine grazing does fed under backyard farming conditions to determine its effect on blood mineral status. Forty-five does were dosed with SGB intraruminally every 6 months, whereas 15 were without SGB during this experimental period of 10 months. Blood of does in both treatment groups were collected every other month and blood Se, plasma Cu, Ca, P and Mg were determined in this study. All does did not show clinical Se, Cu, Ca, P or Mg deficiency during this experimental period. Selenium concentration of treated does increased (p<0.01) after beginning of this experiment, whereas the level of control does decreased slowly (p<0.01). Two months after SGB administration, all treated does had higher blood Se than the lower limit of 20 µg/l suggested by NRC (1981), whereas some control does had lower blood Se concentration than the lower limit of 20 µg/l. On the other hand, plasma Cu concentration of treated does started to increase more remarkably than control does 4 months after this experiment had started although the difference was insignificant. There were no significant differences between plasma Ca, P or Mg concentration of does in both treatment groups. Soluble glass bolus had no harmful effects on plasma macro mineral concentrations of grazing does. This study showed that SGB was available as mineral supplement to improve imbalances of selected mineral of grazing goats in the traditional backyard conditions in Luzon Island, Philippines. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 2 : 189-197)

The effect of a zinc, cobalt and selenium soluble glass bolus on the trace element status of extensively grazed sheep over winter

AbstractThe effects of trace element deficiencies in lambs, particularly zinc, copper, cobalt and selenium, include decreased growth rates and increased mortality. However, trace element supplementation of sheep reared under extensive conditions has several logistical problems.Two trials were designed to investigate the effect of a zinc, cobalt and selenium soluble glass bolus on the trace element status of out-wintered ewe lambs. In trial 1 600 8-month-old ewe lambs (500 Scottish Blackface and 100 North Country Cheviots) were allocated to two treatment groups; 300 were treated with a zinc, cobalt and selenium soluble glass bolus (zinc) and 300 were untreated (control). In trial 2, 315 8-month-old Scottish Blackface ewe lambs were allocated to three treatments: 105 were treated with the zinc, cobalt and selenium soluble glass bolus (zinc), 105 were treated with a copper, cobalt and selenium soluble glass bolus (copper) and the remaining 105 were untreated (control). Blood samples were collected immediately prior to giving boluses and again after approximately 4 months. These were assessed for zinc (plasma zinc concentration), cobalt (serum vitamin B12concentration), selenium (erythrocyte glutathione peroxidase activity) and copper status (plasma copper concentration, caeruloplasmin, amine oxidase and superoxide dismutase activity and calculation of the ratio between the caeruloplasmin and plasma copper).The zinc bolus in both trials significantly increased the plasma zinc concentrations (P&lt; 0·001 andP&lt; 0·01 respectively), erythrocyte glutathione peroxidase activities (P&lt; 0·001) and serum vitamin B12concentrations (P&lt; 0·001). The copper bolus also significantly increased the erythrocyte glutathione peroxidase activities (P&lt; 0·001) and serum vitamin B12concentrations (P&lt; 0·001) when compared with the controls but were not significantly different from the zinc group. The copper bolus significantly increased all of the copper status indicators (P&lt; 0·01) when compared with the control and zinc groups. However, in trial 1 when only the zinc and control groups were compared, the zinc bolus significantly increased the ratio (P&lt; 0·001) and serum caeruloplasmin (P&lt; 0·001) and erythrocyte superoxide dismutase (P&lt; 0·01) activities. These responses were not observed in trial 2 with the erythrocyte superoxide dismutase being significantly reduced in the zinc group when compared with the control group (P&lt; 0·001).The zinc, cobalt and selenium soluble glass bolus increased the status of all three trace elements consistently for a period of at least 100 days. The increases of cobalt and selenium status were similar to those achieved using the copper, cobalt and selenium bolus, which also increased the copper status of the sheep.

Effect of a copper, cobalt and selenium soluble glass bolus given to grazing sheep

Three field trials were carried out to evaluate the performance of a sintered soluble glass copper, cobalt and selenium bolus for maintaining adequate levels of the three trace elements. Trial 1 used 34 growing lambs, trial 2 used 36 growing lambs whilst trial 3 used 50 year-old non productive female sheep. In each trial half the sheep had a bolus administered (bolused) and half remained as controls. Blood samples were taken immediately prior to bolus administration and then at regular intervals throughout each trial. The samples were analysed for copper status (serum caeruloplasmin activity and plasma copper concentration), cobalt status (serum vitamin B 12 concentration) and selenium status (erythrocyte glutathione peroxidase activity). For trial 1 the bolused sheep at all post treatment samplings (days 20, 42 and 63) were significantly increased in both cobalt and selenium status ( P<0.001) compared to the controls, however, there were no significant differences in any other blood parameter. For trial 1 liver copper concentrations were analysed on slaughter samples and were significantly increased for the bolused lambs ( P<0.001). In trial 2 the bolused sheep had significantly increased selenium and cobalt status ( P<0.001) for all samples (days 28, 51, 69, 91). In trial 3 the selenium status of the bolused sheep was significantly increased at all three samplings (day 21, P<0.05 and days 51 and 105, P<0.001), whilst the cobalt status was also significantly increased on all sample days (day 21, P<0.05; day 51, P<0.01 and day 105 P<0.001). The sintered soluble glass copper, cobalt and selenium bolus was able to prevent or correct deficient and/or marginal cobalt and selenium status of sheep throughout these trials. The bolus had little measured effect on the already adequate blood parameters of copper status, although the liver copper concentrations of the bolused sheep were higher in the trial for which they were analysed.

The effect of a zinc, cobalt and selenium soluble glass bolus on trace element status and semen quality of ram lambs

Supplemental zinc and selenium were administered to ram lambs grazed on pastures that were not considered to be deficient in either element. The breeding season and polygamy of the ram mean that his requirements for semen production will be relatively large over a short breeding season and this may induce a localised deficiency of zinc and/or selenium, thus resulting in a decrease in semen quality and production. Thirty-three 8-month-old ram lambs were kept at grass and fed a supplement of barley and peas, with ad libitum access to grass silage when grazing became restricted. On day 0, the rams were allocated to two groups by restricted randomisation of live weight. One group each had a zinc, cobalt and selenium soluble glass bolus (Zincosel®, Telsol) administered with the other group not receiving a bolus to act as a control. Blood samples were taken by jugular venipuncture at day 0 (prior to bolus administration) and at days 23, 44, 65 and 86. Blood samples were analysed for zinc status (plasma zinc concentration) and selenium status (erythrocyte glutathione peroxidase activity). Semen was collected once a week between days 44 and 86, by diversion during a natural mount. Semen quality was assessed by ejaculate volume, spermatocrit, sperm concentration, abnormal morphology, motility, percentage live (negrosin–eosin stain), membrane integrity (hypo-osmotic swelling test (HOS)) and seminal fluid glutathione peroxidase activity and zinc concentration. The bolused lambs had a significantly increased erythrocyte glutathione peroxidase activity ( P<0.01) on all samplings after bolusing and had significant increases in motility, proportion of live sperm and proportion of intact membranes indicated by the HOS. The bolused ram lambs had an increased selenium status and apparent improvement in semen membrane quality.

Induction of zinc deficiency in sheep and its correction with a soluble glass bolus containing zinc.

Balance studies were carried out on four Suffolk-cross lambs which were fed a diet containing only 1.2 mg zinc/kg dry matter; zinc deficiency was induced within three weeks. After a period during which the deficiency was relieved by a pica, the zinc deficient state was re-established. Each sheep was then treated with a soluble glass bolus containing zinc, cobalt and selenium. The plasma zinc concentration of the sheep rapidly increased and was maintained for between six and 10 weeks. The bolus was able to supply the daily requirement of the sheep for zinc, with no detrimental effect on their copper status.

The use of a soluble glass copper, cobalt and selenium bolus to supply selenium to sheep

Many sheep may require supplementation with cobalt or selenium, whilst many also require copper for the prevention of swayback. Often more than one are in short supply and blanket supplementation is often the answer, but this could result in problems of toxicity especially with copper in sheep. This trial was carried out on a flock known to be copper sufficient to investigate the supplementation of extra copper in the form of a sintered soluble glass bolus being used to supply selenium and cobalt to the flock.Two batches of Lleyn sheep were selected, the first were forty ewe lambs, whilst the second set were thirty gimmers. The ewe lambs were randomly split into two groups one being given a copper, cobalt and selenium bolus (Cosecure®, Telsol Ltd) with the other group remaining untreated as controls.

The use of a soluble glass zinc, cobalt and selenium bolus to correct zinc deficiency in sheep

Sub clinical zinc deficiency has been suggested to be involved in disease conditions such as broken mouth periodontitis, footrot and mastitis. However, although there is little risk of primary deficiency in the UK. there are large areas around the Mediterranean. Northern Africa and North America that are reported to be deficient in zinc. Therefore a method that could deleiver a long term continuous supply of zinc would be beneficial in these situations. This trial was designed to examine zinc availability from a zinc, cobalt and selenium soluble glass bolus administered to zinc deficient lambs fed on a low zinc diet throughout the trial.

Large scale field trials of a soluble glass zinc, cobalt and selenium bolus given to sheep

Many sheep in the United Kingdom are grazed on pastures deficient in cobalt and selenium. Proprietary products for selenium and cobalt supplementation often contain copper, which in certain breeds can induce copper toxicity. A soluble glass bolus has been manufactured to supply long term sustained release of cobalt and selenium similar to the commercially available Cosecure, but with the copper content being replaced by zinc. Sub clinical zinc deficiency has been suggested to be involved in disease conditions such as broken mouth periodontitis, footrot and mastitis. Therefore a long term continuous supply of zinc may be beneficial in these situations. This trial was designed to examine the effect of administering a zinc, cobalt and selenium soluble glass bolus on trace element status of over-wintered ewe lambs.

Large scale field trials of a soluble glass zinc, cobalt and selenium bolus given to sheep

Many sheep in the United Kingdom are grazed on pastures deficient in cobalt and selenium. Proprietary products for selenium and cobalt supplementation often contain copper, which in certain breeds can induce copper toxicity. A soluble glass bolus has been manufactured to supply long term sustained release of cobalt and selenium similar to the commercially available Cosecure, but with the copper content being replaced by zinc. Sub clinical zinc deficiency has been suggested to be involved in disease conditions such as broken mouth periodontitis, footrot and mastitis. Therefore a long term continuous supply of zinc may be beneficial in these situations. This trial was designed to examine the effect of administering a zinc, cobalt and selenium soluble glass bolus on trace element status of over-wintered ewe lambs.

The use of a soluble glass zinc, cobalt and selenium bolus to correct zinc deficiency in sheep

Sub clinical zinc deficiency has been suggested to be involved in disease conditions such as broken mouth periodontitis, footrot and mastitis. However, although there is little risk of primary deficiency in the UK. there are large areas around the Mediterranean. Northern Africa and North America that are reported to be deficient in zinc. Therefore a method that could deleiver a long term continuous supply of zinc would be beneficial in these situations. This trial was designed to examine zinc availability from a zinc, cobalt and selenium soluble glass bolus administered to zinc deficient lambs fed on a low zinc diet throughout the trial.