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Topic:Copper

Copper is an essential trace mineral that plays a significant role in various physiological processes in horses. It is involved in the formation of connective tissue, the maintenance of the nervous and immune systems, and the synthesis of hemoglobin. Copper is also a component of several enzymes, including those responsible for antioxidant defense and energy production. Horses obtain copper through their diet, and its levels can be influenced by factors such as soil composition and feed quality. Deficiencies or imbalances in copper can lead to health issues, such as developmental orthopedic disease in young horses and anemia. This page compiles peer-reviewed research studies and scholarly articles that explore the metabolism, dietary requirements, and health implications of copper in equine nutrition and management.
Cytotoxic activity of extracts from Hypochaeris radicata.
Toxicon : official journal of the International Society on Toxinology    May 9, 2013   Volume 70 194-203 doi: 10.1016/j.toxicon.2013.04.023
MacKay RJ, Wyer S, Gilmour A, Kongara K, Harding DR, Clark S, Mayhew IG, Thomson CE.Pasture-associated stringhalt is an acquired equine disease characterized by peripheral neuropathy and hyperflexion of the pelvic limbs. The disease occurs most commonly during periods of drought in horses grazing pastures heavily contaminated by Hypochaeris radicata. We hypothesized that stringhalt is caused by neurotoxins elaborated by H. radicata in response to the stress of drought conditions. Supernates were collected from H. radicata that were stressed (or not) by immersion in copper chloride solution, then extracted with ethyl acetate and dried. Dilutions of extracts from stressed (SE) ...
Determination of Zn-, Cu- and Mn-glycinate complexes in feed samples and in-vitro and in-vivo assays to assess their bioaccessibility in feed samples.
Talanta    April 6, 2013   Volume 113 14-18 doi: 10.1016/j.talanta.2013.03.083
Vacchina V, Ionescu C, Oguey S, Lobinski R.A method was developed for the quantification of Zn-, Cu- and Mn-glycinates in supplemented feed samples. The coupling of capillary electrophoresis (CE) with ICP MS detection after purification of the extract by ultrafiltration was shown to be efficient for the quantitative recovery of glycinates. The method developed was then applied to evaluate the bioaccessibility of glycinates using a sequential enzymolysis approach. The data obtained indicated a strong bioaccessibility of each element (79-94%). A new complex was also found to be formed during the digestion process. Bioavailability was the...
Antioxidant trace elements in serum of draft horses with acute and chronic lower airway disease.
Biological trace element research    July 6, 2012   Volume 150, Issue 1-3 123-129 doi: 10.1007/s12011-012-9471-0
Youssef MA, El-Khodery SA, Ibrahim HM.The aim of the present study was to evaluate the oxidative stress level and antioxidant trace elements status associated with lower airway disease in draft horses. For this purpose, venous blood samples were obtained from draft horses exhibiting signs of lower respiratory tract disorders (n = 83) and from control group (n = 20). Serum trace elements including selenium (Se), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) were assayed. Serum malondialdehyde (MDA) and low-density lipoprotein (LDL) levels as well as plasma hydrogen peroxides (H₂O₂) concentration and activity of ...
Copper-associated hepatic cirrhosis in a Friesian horse.
Tijdschrift voor diergeneeskunde    June 7, 2012   Volume 137, Issue 5 310-314 
Ankringa N, Wijnberg ID, Boerma S, Ijzer J.A 6-year-old Friesian stallion was examined because of signs of exercise intolerance, stiff gait and symmetrical hind weakness, and increased serum liver enzymes. On presentation, the horse showed muscle atrophy of the hindquarters. Neurological investigation showed no abnormalities. Laboratory findings revealed a prolonged prothrombin time and increased levels of alkaline phosphatase (AF), aspartate aminotransferase (ASAT), gamma-glutamyl-transferase (GGT), lactate dehydrogenase (LDH), and bile acids. Histological evaluation of the liver revealed severe cirrhosis and intracytoplasmic greyish ...
A genetic variant near the equine interleukin 6 gene associated with copper:zinc ratio.
Veterinary journal (London, England : 1997)    February 16, 2011   Volume 190, Issue 2 e143-e145 doi: 10.1016/j.tvjl.2010.12.028
Beghelli D, Giacconi R, Mocchegiani E, Cipriano C, Malavolta M, Renieri C.The aim of this study was to validate an A/T single nucleotide polymorphism (SNP) corresponding to a LINE2 sequence located ∼1.1kb downstream of the IL-6 gene (SNP BIEC2-911738) and to determine if this variant is correlated with interleukin 6 (IL-6) modulation or with different plasma concentrations of Zn, Cu, Se and Fe. The frequency of the newly described variant T ranged from 0 to 23.1% among different breeds of horses. SBIEC2-911738 was not associated with changes in IL-6 plasma levels. Increased Cu:Zn ratios were observed in horses carrying the AT genotype independently of breed when s...
Copper and zinc balance in exercising horses fed 2 forms of mineral supplements.
Journal of animal science    November 12, 2010   Volume 89, Issue 3 722-728 doi: 10.2527/jas.2010-2871
Wagner EL, Potter GD, Gibbs PG, Eller EM, Scott BD, Vogelsang MM, Walzem RL.Studies comparing the absorption and retention of various forms of trace minerals in horses have yielded mixed results. The objective of this study was to compare Cu and Zn absorption and retention in exercising horses where the mineral was supplemented in the sulfate or organic chelate form. Nine mature horses were used in a modified switchback design experiment consisting of seven 28-d periods. Horses were fed a diet consisting of 50% concentrate and 50% hay that was balanced to meet the energy, protein, Ca, and P requirements for horses performing moderate-intensity exercise. Horses were su...
Changes in serum mineral concentrations, biochemical and hematological parameters in horses with pica.
Biological trace element research    March 9, 2010   Volume 139, Issue 3 301-307 doi: 10.1007/s12011-010-8660-y
Aytekin I, Onmaz AC, Aypak SU, Gunes V, Kucuk O.The aim of this study was to compare hematological, some biochemical parameters, and serum trace element concentrations in horses with or without pica. Fifteen horses with pica (group I) and another 15 healthy horses without pica (group II) were used. The hematological parameters were not changed between the two groups. In group I, hemoglobin values were lower than those of group II. However, the difference in hemoglobin values between the two groups was not significant (P > 0.05). Serum iron and copper concentrations and the copper/zinc ratio were lower in group I than those of group I...
Effect of diet on mechanical properties of horse’s hair.
Acta of bioengineering and biomechanics    February 6, 2010   Volume 11, Issue 3 53-57 
Kania M, Mikołajewska D, Marycz K, Kobielarz M.The aim of this research was to assess the effect of diet supplementation with zinc and copper, in different chemical forms (organic and inorganic), on the mechanical properties of the hair of healthy English thoroughbred horses. Hairs were taken from 18 horses which had been fed with oats and hay for a period of 110 days. Twelve of the horses had been additionally given a daily dose of 700 g of highquality 44-ingredients Fohlengold St-Hippolyt muesli made by Muhle Ebert Dilheim. Six of them had received the muesli-containing organic zinc and copper (OS), while the other six horses had receive...
Heavy metal concentration in coat hair and hoof horn in stabled and reserve Polish Konik horses.
Polish journal of veterinary sciences    November 5, 2009   Volume 12, Issue 3 369-377 
Stachurska A, Wałkuska G, Chałabis-Mazurek A, Jaworski Z, Cebera M.The objective of the study was to determine if there were differences in Cr, Mn, Cu, Cd, Pb and Ni levels in coat hair and hoof horn between Polish Konik horses maintained in stabled and reserve systems in Roztocze National Park in Poland. Summer and winter feeding seasons (seasons of the year in case of hooves) and age of horses were taken into account. 107 samples of hair and hooves, as well as all kinds of feed and sources of water available for the horses were examined. The results of the study indicate that the concentration of the elements in the coat hair, hoof horn, feeds and water is ...
Mineral absorption in tapirs (Tapirus spp.) as compared to the domestic horse.
Journal of animal physiology and animal nutrition    January 13, 2009   Volume 93, Issue 6 768-776 doi: 10.1111/j.1439-0396.2008.00865.x
Clauss M, Lang-Deuerling S, Kienzle E, Medici EP, Hummel J.To test whether mineral recommendations for horses are likely to guarantee adequate mineral provision for tapirs (Tapirus spp.), we investigated the apparent absorption (aA) of macro and micro-minerals in 18 tapirs from five zoological institutions in a total of 24 feeding trials with total faecal collection. Samples of feeds and faeces were analysed for Ca, P, Mg, Na, K, Fe, Cu and Zn. The resulting aA coefficients and the linear relationships of apparently absorbable dietary mineral content to total dietary mineral content (per 100 g dry matter) were compared with data for domestic horses. W...
Effects of vitamin E and selenium on serum trace and major elements in horses.
Biological trace element research    September 17, 2008   Volume 125, Issue 3 223-228 doi: 10.1007/s12011-008-8109-8
Yur F, Dede S, Deger Y, Kilicalp D.The combined effects of vitamin E and selenium were studied in native Anatolian horses subject to strenuous exercise. The concentrations of copper, zinc, iron, calcium, potassium, and magnesium were determined in serum by atomic absorption spectrometry in two study groups (n = 25 each), one of which served as untreated controls. After exercising the horses by running 1,500 m in about 7 min, only the copper level and the copper/zinc ratio significantly increased (p < 0.05), but the concentrations of calcium, potassium, iron, and magnesium remained unchanged. In horses treated with vitamin E ...
Plasma levels of zinc, copper, copper/zinc ratio, and activity of carbonic anhydrase in equine piroplasmosis.
Biological trace element research    August 3, 2008   Volume 125, Issue 1 41-45 doi: 10.1007/s12011-008-8136-5
Dede S, DeÄŸer Y, DeÄŸer S, Tanritanir P.We have determined the plasma concentrations of copper, zinc, copper/zinc ratio, and carbonic anhydrase activity in horses infected with Babesia equi. The study was conducted in 14 horses with the disease and 10 healthy animals that served as controls. The infection was confirmed by the clinical manifestations of the disease and by Giemsa staining of thin blood smears showing the parasites inside red blood cells. The horses with piroplasmosis had lower plasma levels of zinc, elevated copper, and increased activity of carbonic anhydrase. Consequently, the copper/zinc ratio was also higher than ...
Comparative activities of semicarbazide-sensitive amine oxidase (SSAO) in five domestic species.
Polish journal of veterinary sciences    June 11, 2008   Volume 11, Issue 1 63-66 
Al-Wabel NA.Semicarbazide-sensitive amine oxidase (SSAO) activity was measured spectrophotometrically using benzylamine as a substrate, in the serum of healthy males and females of horses, camels, cattle, sheep and goats. The animals were born and raised in the same area, and the blood collection was made on the same day to avoid variations. Also the concentrations of protein and copper were measured in the same samples. There were no significant gender-related differences in SSAO activity between the tested animals regardless of species. Activities of SSAO in either male or female of horse were significa...
Serum concentration of copper, zinc, iron, and cobalt and the copper/zinc ratio in horses with equine herpesvirus-1.
Biological trace element research    September 13, 2007   Volume 118, Issue 1 38-42 doi: 10.1007/s12011-007-0023-y
Yörük I, Deger Y, Mert H, Mert N.The serum concentrations of copper, zinc, iron, and cobalt and copper/zinc ratio were investigated in horses infected with equine herpesvirus-1 (EHV-1). Nine horses were naturally infected with the virus and nine healthy horses served as controls. The concentrations of copper, zinc, iron, and cobalt were determined spectrophotometrically in the blood serum of all horses. The results were (expressed in micrograms per deciliters) copper 2.80 +/- 0.34 vs 1.12 +/- 0.44, zinc 3.05 +/- 0.18 vs 0.83 +/- 0.06, iron 2.76 +/- 0.17 vs 3.71 +/- 0.69, cobalt 0.19 +/- 0.37 vs 0.22 +/- 0.45, and copper/zinc ...
Relationship between hair elements and severity of atrioventricular block in horses.
Biological trace element research    July 13, 2007   Volume 115, Issue 3 255-264 doi: 10.1007/BF02686000
Suzuki K, Yamaya Y, Asano K, Chiba M, Sera K, Matsumoto T, Sakai T, Asano R.The aim of this study was to investigate the relationships between the mean concentrations of trace elements and the severity of the second-degree atrioventricular (AV) block in the mane hair of horses. Electrocardiographs of horses were continually recorded for 6 h using a holter cardiac monitor to determine dropped ventricular beats (DVBs) which can be used as an indicator of the severity of the AV block. Mane hair Ca, Cu, Mg, and Zn concentrations were measured by the particle-induced X-ray emission method. The Zn/Cu ratio and Ca concentration in mane hair were significantly and positively ...
Mineral absorption in the black rhinoceros (Diceros bicornis) as compared with the domestic horse.
Journal of animal physiology and animal nutrition    May 23, 2007   Volume 91, Issue 5-6 193-204 doi: 10.1111/j.1439-0396.2007.00692.x
Clauss M, Castell JC, Kienzle E, Schramel P, Dierenfeld ES, Flach EJ, Behlert O, Streich WJ, Hummel J, Hatt JM.To test whether mineral recommendations for horses are likely to guarantee adequate mineral provision for black rhinoceroses (Diceros bicornis), we investigated the apparent absorption (aA) of macro- and microminerals in eight black rhinoceroses from three zoological institutions in a total of 32 feeding trials with total faecal collection, with additional data from three unpublished studies (18 feeding trials). Feeds and faeces were analysed for Ca, P, Mg, Na, K, Fe, Mn, Cu, Zn and Co. The resulting aA coefficients, and the linear relationships of apparently absorbable dietary mineral content...
Investigation of blood oxidant/antioxidant markers in healthy competition horses of different breeds.
Equine veterinary journal. Supplement    April 4, 2007   Issue 36 239-244 doi: 10.1111/j.2042-3306.2006.tb05546.x
Kirschvink N, de Moffarts B, Farnir F, Pincemail J, Lekeux P.There is increasing evidence that the equine athlete is exposed to exercise-induced changes of its oxidant/antioxidant balance and antioxidant supplementation is frequently recommended. However, it is unknown whether there is a specific need for antioxidants according to performance, breed, gender or age. Objective: To assess whether breed-, gender- and age-related differences of blood oxidant/antioxidant markers occur in competition horses. Methods: Healthy horses (n = 493) underwent oxidant/ antioxidant blood marker determination. Vitamin E, lipophilic antioxidant capacity (ACL), ascorbic ac...
Effects of exercise and oral antioxidant supplementation enriched in (n-3) fatty acids on blood oxidant markers and erythrocyte membrane fluidity in horses.
Veterinary journal (London, England : 1997)    November 15, 2006   Volume 174, Issue 1 113-121 doi: 10.1016/j.tvjl.2006.06.001
De Moffarts B, Portier K, Kirschvink N, Coudert J, Fellmann N, van Erck E, Letellier C, Motta C, Pincemail J, Art T, Lekeux P.The aim of this study was to investigate in a placebo-controlled field study the effect of a (n-3)-vitamin supplementation on erythrocyte membrane fluidity (EMF), oxidant/antioxidant markers and plasmatic omega3/omega6 fatty acid ratio (FAR) in 12 eventing horses. Venous blood was sampled at rest before (PRE) and after (POST) a three week treatment period with either the supplement (group S, n=6) or a placebo (group P, n=6) as well as after 15min (POST E15') and 24h (POST E24h) after a standardised exercise test. The following markers were analysed: EMF, plasma antioxidant capacity of water an...
Relationship between trace elements status in mane hair and atrial fibrillation in horse.
The Journal of veterinary medical science    August 8, 2006   Volume 68, Issue 7 769-771 doi: 10.1292/jvms.68.769
Asano K, Suzuki K, Chiba M, Sera K, Asano R, Sakai T.To investigate the relationships between trace elements concentrations in hair and atrial fibrillation (AF) in horses, concentrations of nineteen trace elements were detected in hair using the particle induced X-ray emission (PIXE) method. The horses were assigned to either control (n=22, no abnormalities) or AF groups (n=5) based on electrocardiograph findings. The mean concentrations of Ca and Zn in the hair of the AF group were significantly higher than those in the control group. The Zn/Cu ratio of the hair in the AF group (29.8 +/- 5.5) was significantly higher than that in the control gr...
Macromineral absorption in the black rhinoceros (Diceros bicornis) compared with the domestic horse.
The Journal of nutrition    June 15, 2006   Volume 136, Issue 7 Suppl 2017S-2020S doi: 10.1093/jn/136.7.2017S
Clauss M, Castell JC, Kienzle E, Schramel P, Dierenfeld ES, Flach EJ, Behlert O, Hatt JM, Streich WJ, Hummel J.No abstract available
Evaluation of the risk of motor neuron disease in horses fed a diet low in vitamin E and high in copper and iron.
American journal of veterinary research    January 24, 2006   Volume 67, Issue 1 120-126 doi: 10.2460/ajvr.67.1.120
Divers TJ, Cummings JE, de Lahunta A, Hintz HF, Mohammed HO.To determine whether equine motor neuron disease (EMND) could be induced in adult horses fed a diet low in vitamin E and high in copper and iron. Methods: 59 healthy adult horses. Methods: Horses in the experimental group (n = 8) were confined to a dirt lot and fed a concentrate low in vitamin E and high in iron and copper in addition to free-choice grass hay that had been stored for 1 year. Control horses (n = 51) were fed a concentrate containing National Research Council-recommended amounts of copper, iron, and vitamin E. The hay fed to control horses was the same as that fed to experimenta...
Determination of some enzymes and macro- and microelements in stallion seminal plasma and their correlations to semen quality.
Theriogenology    January 4, 2006   Volume 66, Issue 2 307-313 doi: 10.1016/j.theriogenology.2005.11.015
Pesch S, Bergmann M, Bostedt H.Seminal plasma is very important for sperm metabolism as well as sperm function and survival and transport in the female genital tract. Analysis of enzyme activities and concentrations of elements can estimate integrity and function of sperm cell membranes. In man much data are available about biochemical analyses of seminal plasma. However, not many studies have been conducted in horses yet. We collected ejaculates from 72 stallions, measured the volume, obtained seminal plasma by centrifugation and examined spermatozoa with light microscopy for motility, concentration, for dead sperm and mor...
Correlation between 25 element contents in mane hair in riding horses and atrioventricular block.
Biological trace element research    December 6, 2005   Volume 108, Issue 1-3 127-136 doi: 10.1385/BTER:108:1-3:127
Asano K, Suzuki K, Chiba M, Sera K, Matsumoto T, Asano R, Sakai T.The influence of atrioventricular block (AV-block) on the trace elemental status in a horse hair was studied. The particle-induced X-ray emission (PIXE) method has provided a reliable, rapid, easy, and relatively inexpensive diagnostic method. Twenty-five elements (Al, Br, Ca, Cl, Co, Cu, Cr, Fe, Hg, K, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, S, Se, Si, Sr, Ti, Y, and Zn) in mane hair and serum were measured by the PIXE method. A horse hair with first- and second-degree AV-block contained significantly greater amounts of Br, Ca, Sr, and Zn than those of horses without electrocardiographic abnormalities...
Articular / epiphyseal osteochondrosis in Thoroughbred foals at 5 months of age: influences of growth of the foal and prenatal copper supplementation of the dam.
New Zealand veterinary journal    December 1, 2005   Volume 53, Issue 6 448-456 doi: 10.1080/00480169.2005.36591
Gee EK, Firth EC, Morel PC, Fennessy PF, Grace ND, Mogg TD.To determine the influence of copper (Cu) supplementation by injection of mares in late gestation on the frequency and severity of osteochondrosis (OC) lesions in their foals at around 160 days of age. To determine if there was any influence of the concentration of Cu in the liver, growth rate, birthweight, weight at 160 days of age, fatness, sex, or year of birth of the foal on the frequency and severity of OC lesions. To determine the influence of dam's age, and sex and birthweight of the foal on the growth rate from birth to 160 days of age, and weight at 160 days of age. Methods: Thirty-th...
Enlargements of the distal third metacarpus and metatarsus in Thoroughbred foals at pasture from birth to 160 days of age.
New Zealand veterinary journal    December 1, 2005   Volume 53, Issue 6 438-447 doi: 10.1080/00480169.2005.36590
Gee EK, Firth EC, Morel PC, Fennessy PF, Grace ND, Mogg TD.To assess the relationship between the radiographic and microscopic appearance of the physeal regions of the distal third metacarpal (Mc3) and metatarsal (Mt3) bones of Thoroughbred foals at 160 days of age, and to clinically assess changes in contour of the distal Mc3 and Mt3 physeal regions from birth to 160 days of age. To assess relationships between maximum clinical physis scores and age, time of year, foal's sex, condition score, growth rate, copper (Cu) concentration in the liver of the foal, and supplementation of the dam with Cu in late gestation. Methods: Dams were given Cu (n=5 and ...
Osteochondrosis and copper: histology of articular cartilage from foals out of copper supplemented and non-supplemented dams.
Veterinary journal (London, England : 1997)    November 28, 2005   Volume 173, Issue 1 109-117 doi: 10.1016/j.tvjl.2005.09.015
Gee E, Davies M, Firth E, Jeffcott L, Fennessy P, Mogg T.Copper (Cu) supplementation of dams in late gestation may be protective against articular cartilage abnormalities in foals. Articular cartilage was harvested from 22 Thoroughbred foals at 160 days of age, at sites predisposed to osteochondrosis (OC), and examined for evidence of early cartilage abnormalities and established dyschondroplastic (DCP) lesions to determine if there were any significant differences due to mare Cu supplementation by injection during late gestation, or foal liver Cu concentration. Cu supplemented mares received calcium Cu edetate injections in late gestation (250 mg a...
Twenty-eight element concentrations in mane hair samples of adult riding horses determined by particle-induced X-ray emission.
Biological trace element research    October 12, 2005   Volume 107, Issue 2 135-140 doi: 10.1385/BTER:107:2:135
Asano K, Suzuki K, Chiba M, Sera K, Asano R, Sakai T.The concentrations of 28 elements (Al, Br, Ca, Cl, Co, Cu, Cr, Fe, Ga, Hg, K, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, S, Se, Si, Sr, Ti, V, Y, and Zn) were measured in mane hair by the particle-induced X-ray emission method. Except for Br, Cl, K, S, and P, the trace element concentrations in mane hair of horses are similar to literature values for human hair. The values obtained are not dependent on the horse's age, breed, and sex and could be used as reference values in the assessment of diseases and nutritional status in equines.
Association of pneumonia in foals caused by Rhodococcus equi with farm soil geochemistry.
American journal of veterinary research    October 7, 2005   Volume 63, Issue 1 95-98 doi: 10.2460/ajvr.2002.63.95
Martens RJ, Cohen ND, Chaffin MK, Waskom JS.To quantify and compare geochemical factors in surface soils from horse-breeding farms with horses with pneumonia caused by Rhodococcus equi (affected farms) and horse-breeding farms with no history of pneumonia caused by R equi (unaffected farms). Methods: Soil from 24 R equi-affected farms and 21 unaffected farms. Methods: Equine veterinary practitioners throughout Texas submitted surface soil samples from areas most frequented by foals, on R equi-affected and unaffected horse-breeding farms in their practice. Soil samples were assayed for the following factors: pH, salinity, nitrate, phosph...
Formation of a cytochrome c-nitrous oxide reductase complex is obligatory for N2O reduction by Paracoccus pantotrophus.
Dalton transactions (Cambridge, England : 2003)    September 23, 2005   Issue 21 3501-3506 doi: 10.1039/b501846c
Rasmussen T, Brittain T, Berks BC, Watmough NJ, Thomson AJ.Nitrous oxide reductase (N2OR) catalyses the final step of bacterial denitrification, the two-electron reduction of nitrous oxide (N2O) to dinitrogen (N2). N2OR contains two metal centers; a binuclear copper center, CuA, that serves to receive electrons from soluble donors, and a tetranuclear copper-sulfide center, CuZ, at the active site. Stopped flow experiments at low ionic strengths reveal rapid electron transfer (kobs=150 s-1) between reduced horse heart (HH) cytochrome c and the CuA center in fully oxidized N2OR. When fully reduced N2OR was mixed with oxidized cytochrome c, a similar rat...
Digestible energy intake, dry matter digestibility and mineral status of grazing New Zealand Thoroughbred yearlings.
New Zealand veterinary journal    July 21, 2005   Volume 50, Issue 2 63-69 doi: 10.1080/00480169.2002.36252
Grace ND, Gee EK, Firth EC, Shaw HL.To measure the nutritive value of pasture in terms of digestible energy intake (DEI) and dry matter (DM) digestibility, and to determine the effect of Ca, P, Cu, Zn, and Se supplementation on growth rate and degree of physeal swelling in Thoroughbred yearlings grazed on pasture. Methods: Fourteen yearling horses were randomly allocated to 1 of 2 groups and rotationally grazed on a ryegrass/white clover pasture for 7 months. One group was supplemented daily with a mineral mix. Liveweight changes were recorded at fortnightly intervals and pasture mineral composition determined at monthly interva...