Effect of a commercial anionic dietary supplement on urinary pH and concentrations of electrolytes and pH in blood of horses.

Aims: To compare urine urinary pH, blood pH and concentration of electrolytes in blood of healthy horses fed an anionic salt supplement to achieve diets with a dietary cation-anion difference (DCAD) of -40 or 0 mEq/kg DM, with horses a fed a diet with a DCAD of 85 mEq/kg DM.Methods: Eight healthy horses received each of three diets in a randomised crossover design. Diets consisted of grass hay and concentrate feed, with a varying amount of an anionic supplement to achieve a DCAD of 85 (control), 0 or -40 mEq/kg DM. They were fed for 14 days each with a washout period of 7 days between. Urine pH was measured daily and blood samples were collected on Days 0, 7 and 14 of each study period for the measurement of pH and concentration of electrolytes.Results: Four horses voluntarily consumed the anionic supplement with their feed, but four horses required oral supplement administration via dose syringe. During the study period mean urine pH was lower in horses fed diets with a DCAD of 0 (6.91; SD 0.04) and -40 (6.83; SD 0.04) mEq/kg DM compared to the control diet (7.30; SD 0.04). Compared with horses fed the control diet, mean urine pH was lower in horses fed the 0 and -40 mEq/kg DM diets on Days 1-12 and 14 (p < 0.05) of the study period. On Day 13 it was only lower in horses fed the -40 mEq/kg DM diet (p < 0.01). Urine pH was similar for horses fed the 0 and -40 mEq/kg DM diets (p = 0.151). The DCAD of the diet had no effect on blood pH, ionised Ca or anion gap. Mean concentrations of bicarbonate in blood were affected by diet (p = 0.049); they were lower when horses were fed the 0 mEq/kg diet relative to the control diet on Day 14.Conclusions and clinical relevance: The anionic supplement reduced urine pH in horses fed diets with a DCAD of 0 or -40 mEq/kg DM compared with 85 mEq/kg DM. However as urinary pH did not fall below pH 6.5, the pH below which calcium carbonate uroliths do not form, this reduction in urine pH is unlikely to be clinically significant. The supplement was variably palatable and showed minimal promise as an effective urinary acidifier at the doses administered in this study.

Probiotic supplementation in trained trotter horses: effect on blood clinical pathology data and urine metabolomic assessed in field.

The attention of sports community toward probiotic supplementation as a way to promote exercise and training performance, together with good health, has increased in recent years. This has applied also to horses, with promising results. Here, for the first time, we tested a probiotic mix of several strains of live bacteria typically employed for humans to improve the training performance of Standardbred horses in athletic activity. To evaluate its effects on the horse performance, we measured lactate concentration in blood, a translational outcome largely employed for the purpose, combined with the study of hematological and biochemical parameters, together with urine from a metabolomics perspective. The results showed that the probiotic supplementation significantly reduced postexercise blood lactate concentration. The hematological and biochemical parameters, together with urine molecular profile, suggested that a likely mechanism underlying this positive effect was connected to a switch of energy source in muscle from carbohydrates to short-chain fatty acids. Three sulfur-containing molecules differently concentrated in urines in connection to probiotics administration suggested that such switch was linked to sulfur metabolism. NEW & NOTEWORTHY Probiotic supplementation could reduce postexercise blood lactate concentration in Standardbred horses in athletic activity. Blood parameters, together with urine molecular profile, suggest the mechanism underlying this positive effect is connected to a switch of energy source in muscle from carbohydrates to short-chain fatty acids. Sulfur-containing molecules found in urines in connection to probiotics administration suggested that such switch was linked to sulfur metabolism.

Pharmacokinetics of inorganic cobalt and a vitamin B12 supplement in the Thoroughbred horse: Differentiating cobalt abuse from supplementation.

BACKGROUND: While cobalt is an essential micronutrient for vitamin B12 synthesis in the horse, at supraphysiological concentrations, it has been shown to enhance performance in human subjects and rats, and there is evidence that its administration in high doses to horses poses a welfare threat. Animal sport regulators currently control cobalt abuse via international race day thresholds, but this work was initiated to explore means of potentially adding to application of those thresholds since cobalt may be present in physiological concentrations. OBJECTIVES: To devise a scientific basis for differentiation between presence of cobalt from bona fide supplementation and cobalt doping through the use of ratios. STUDY DESIGN: Six Thoroughbred horses were given 10 mL vitamin B12 /cobalt supplement (Hemo-15® ; Vetoquinol, Buckingham, Buckinghamshire, UK., 1.5 mg B12 , 7 mg cobalt gluconate = 983 µg total Co) as an i.v. bolus then an i.v. infusion (15 min) of 100 mg cobalt chloride (45.39 mg Co) 6 weeks later. Pre-and post-administration plasma and urine samples were analysed for cobalt and vitamin B12 . METHODS: Urine and plasma samples were analysed for vitamin B12 using an immunoassay and cobalt concentrations were measured via ICP-MS. Baseline concentrations of cobalt in urine and plasma for each horse were subtracted from their cobalt concentrations post-administration for the PK analysis. Compartmental analysis was used for the determination of plasma PK parameters for cobalt using commercially available software. RESULTS: On administration of a vitamin B12 /cobalt supplement, the ratio of cobalt to vitamin B12 in plasma rapidly increased to approximately 3 and then rapidly declined below a ratio of 1 and then back to near baseline over the next week. On administration of 100 mg cobalt chloride, the ratio initially exceeded 10 in plasma and then declined with the lower 95% confidence interval remaining above a ratio of 1 for 7 days. For two horses with extended sampling, the plasma ratio remained above one for approximately 28 days after cobalt chloride administration. The effect of the administration of the vitamin B12 /cobalt supplement on the urine ratio was transient and reached a peak value of 10 which then rapidly declined. However, a urine ratio of 10 was exceeded, with the lower 95% confidence interval remaining above a ratio of 10 for 7 days after cobalt chloride administration. For the two horses with extended sampling, the urine ratio remained above 10 for about 18 days (442 h) after cobalt chloride administration even though the absolute cobalt urine concentration had dropped below the international threshold of 100 ng/mL after 96 h. MAIN LIMITATIONS: Only one vitamin B12 /cobalt product was evaluated, a limited number of horses were included, the horses were not in full race training and the results may be specific to this population of horses. CONCLUSIONS: The results provide the basis for a potential strategy for allowing supplementation with vitamin B12 products, while controlling the misuse of high doses of cobalt, through a combination of international thresholds and ratios of cobalt to vitamin B12 , in plasma and urine.

Mouldy feed: A possible explanation for the excretion of anabolic-androgenic steroids in horses.

To ensure fair competition and to protect the horse's welfare, horses have to compete on their own merits, without any unfair advantage that might follow the use of drugs. Therefore, regulatory authorities list all substances that are not allowed in competition, including most anabolic-androgenic steroids. As zero-tolerance is retained, the question arose whether the consumption of mouldy feed could lead to the excretion of steroids, due to the biotransformation of plant phytosterols to steroids. A rapid ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) analytical method, previously validated according to AORC (Association of Official Racing Chemists) and EC (European Commission) guidelines, was used to measure steroids in different sample types. Multiple mouldy feed samples were tested for the presence of steroids. The effect of digestion was tested by in vitro simulation of the horse's hindgut in batch incubations. In most feed samples no steroids were detected, even when the products were mouldy. Mouldy corn however showed to contain up to 3.0 ± 0.4 µg/kg AED (4-androstenedione), the main testosterone precursor. This concentration increased when mouldy corn (with added phytosterols) was digested in vitro. An herbal phytosupplement also showed to contain α-testosterone. These results demonstrate that it is important to caution against the consumption of any feed or (herbal) supplement of which the detailed ingredients and quantitative analysis are unknown. The consumption of mouldy corn should especially be avoided, not only from a horse health and welfare point of view, but also to avoid possible inadvertent positive doping results. Copyright © 2016 John Wiley & Sons, Ltd.

Controlling the misuse of cobalt in horses.

Cobalt is a well-established inducer of hypoxia-like responses, which can cause gene modulation at the hypoxia inducible factor pathway to induce erythropoietin transcription. Cobalt salts are orally active, inexpensive, and easily accessible. It is an attractive blood doping agent for enhancing aerobic performance. Indeed, recent intelligence and investigations have confirmed cobalt was being abused in equine sports. In this paper, population surveys of total cobalt in raceday samples were conducted using inductively coupled plasma mass spectrometry (ICP-MS). Urinary threshold of 75 ng/mL and plasma threshold of 2 ng/mL could be proposed for the control of cobalt misuse in raceday or in-competition samples. Results from administration trials with cobalt-containing supplements showed that common supplements could elevate urinary and plasma cobalt levels above the proposed thresholds within 24 h of administration. It would therefore be necessary to ban the use of cobalt-containing supplements on raceday as well as on the day before racing in order to implement and enforce the proposed thresholds. Since the abuse with huge quantities of cobalt salts can be done during training while the use of legitimate cobalt-containing supplements are also allowed, different urinary and plasma cobalt thresholds would be required to control cobalt abuse in non-raceday or out-of-competition samples. This could be achieved by setting the thresholds above the maximum urinary and plasma cobalt concentrations observed or anticipated from the normal use of legitimate cobalt-containing supplements. Urinary threshold of 2000 ng/mL and plasma threshold of 10 ng/mL were thus proposed for the control of cobalt abuse in non-raceday or out-of-competition samples.

Disposition and metabolic profile of the weak androgen Dehydroepiandrosterone (DHEA) following administration as part of a nutritional supplement to exercised horses.

In order to ensure the welfare of performance horses and riders as well as the integrity of the sport, the use of both therapeutic and illegal agents in horse racing is tightly regulated. While Dehydroepiandrosterone (DHEA) is not specifically banned from administration to racehorses in the United States and no screening limit or threshold concentration exists, the metabolic conversion of DHEA to testosterone make its presence in nutritional supplements a regulatory concern. The recommended regulatory threshold for total testosterone in urine is 55 and 20 ng/mL for mares and geldings, respectively. In plasma, screening and confirmation limits for free testosterone (mares and geldings), of no greater than 0.1 and 0.025 ng/mL, respectively are recommended. DHEA was administered orally, as part of a nutritional supplement, to 8 exercised female thoroughbred horses and plasma and urine samples collected at pre-determined times post administration. Using liquid chromatography-mass spectrometry (LC-MS), plasma and urine samples were analyzed for DHEA, DHEA-sulfate, testosterone, testosterone-sulfate, pregnenolone, androstenedione, and androstenediol. DHEA was rapidly absorbed with maximal plasma concentrations reaching 52.0 ± 43.8 ng/mL and 32.1 ± 12.9 ng/mL for DHEA and DHEA sulfate, respectively. Free testosterone was not detected in plasma or urine samples at any time. Maximum sulfate conjugated testosterone plasma concentrations were 0.98 ± 1.09 ng/mL. Plasma testosterone-sulfate concentrations did not fall below 0.1 ng/mL and urine testosterone-sulfate below 55 ng/mL until 24-36 h post DHEA administration. Urine testosterone sulfate concentrations remained slightly above baseline levels at 48 h for most of the horses studied.

The effect of long-term oral L-carnitine administration on insulin sensitivity, glucose disposal, plasma concentrations of leptin and acylcarnitines, and urinary acylcarnitine excretion in warmblood horses.

BACKGROUND: Insulin resistance in horses is an emerging field of interest as it is thought to be a contributing factor in the pathogenesis of many equine conditions. OBJECTIVES: The objectives of the present study were to determine the effects of long-term oral administration of L-carnitine on insulin sensitivity, glucose disposal, plasma leptin concentrations and acylcarnitine spectrum both in plasma and urine. ANIMALS AND METHODS: Six 3-year-old healthy warmblood geldings were used. In a double blind 2 × 2 Latin square design at a dosage of 100 mg/kg body weight (BW)/day for 28 days the effects of oral supplementation of L-carnitine (as fumarate) were assessed. Glucose disposal and insulin sensitivity were measured by means of the euglycemic-hyperinsulinemic clamp technique. Radioimmunoassays were used to determine plasma leptin and insulin concentrations. Electrospray tandem mass spectrometry was used to assess acylcarnitines both in plasma and urine. Statistical analysis was performed using a linear mixed-effects model and P values <0.05 were considered significant. RESULTS: Long-term L-carnitine administration did not affect insulin sensitivity. Plasma leptin and free carnitine concentrations in plasma and urine increased significantly (P = 0.047 and 0.000, respectively) following L-carnitine administration as well as short-chain acylcarnitines in plasma and urinary excretion of short- and medium-chain acylcarnitines. CONCLUSION AND CLINICAL RELEVANCE: Given the effects of oral administration of L-carnitine further clinical study is necessary in order to assess the potential beneficial effects in equine patients suffering from metabolic myopathies such as acquired multiple acyl-CoA dehydrogenase deficiency. IMPACT FOR HUMAN MEDICINE: The current study supports the treatment rationale of short-chain acyl-CoA dehydrogenase deficiency in humans with L-carnitine at an oral dosage of 100 mg/kg BW/day.

Influence of high phosphorus intake on salivary and plasma concentrations, and urinary phosphorus excretion in mature ponies.

This study addressed the question whether the concentration of phosphorus (P) in saliva of ponies is influenced by P intake. Six ponies were fed a diet high in P (HP treatment), providing 21 g P/day, and a diet low in P (LP treatment), supplying 7 g P/day. The two diets provided approximately 21 g calcium (Ca) and 6 g magnesium (Mg)/day. The experiment had an A-B-A design with treatment periods of 30 days. The ponies first received the HP diet (HP1), followed by the LP treatment and were then fed again the HP diet (HP2). Urinary P excretion was increased in both HP feeding periods and equalled approximately 7% of P intake vs. 0.5% on the LP diet. Plasma P concentration was higher for the HP treatment. The salivary P concentration ranged from 0 to 1.01 mmol P/l between ponies and there was no effect of P intake. It is suggested that saliva is not an important excretion route of P. The percentage of Ca and Mg in urine (% of intake) was higher for the LP treatment than for the HP treatments. The results of this study suggest that salivary Mg may contribute to Mg homeostasis.

Digestibility and nutrient retention of perennial peanut and bermudagrass hays for mature horses.

Mature horses were used to determine apparent DM, OM, NDF, and CP digestibility values of 2 bermudagrass (BG; Cynodon dactylon) hays, Coastal (CB) and Tifton 85 (T85), and Florigraze perennial peanut (PP; Arachis glabrata) hay. In addition, N, Ca, and P balances were determined in horses fed those hays. Five mature Thoroughbred geldings and 1 Quarter Horse gelding (mean initial BW = 542 +/- 37 kg) were used (5 horses for the last period) in a 3 x 3 repeated Latin square design, with 2 horses per hay and 3 adjustment and collection periods. Horses were randomly assigned to pairs and the initial hay to be fed. Each period consisted of a 10-d adjustment phase, followed by a 4-d total fecal and urine collection phase. Horses were fed at 1.5 (period 1), 1.7 (period 2), or 2% (period 3) of their BW daily (DM basis). The 2 BG were grown under similar conditions, with CB and T85 being cut at 4 and 5 wk of regrowth, respectively, and PP being of a late first cutting. The compositions (DM basis) of PP, CB, and T85, respectively, were 93, 94, and 93% DM; 92, 94, and 94% OM; 46, 73, and 77% NDF; 34, 37, and 42% ADF; 11, 10, and 8% CP; 1.10, 0.28, 0.27% Ca; and 0.19, 0.15, and 0.19% P, respectively. Least squares means (pooled SE) for apparent digestibility of PP, CB, and T85, respectively, were 65, 53, and 52% (1) DM digestibility; 67, 53, and 52% (1) OM digestibility; 44, 50, and 46% (4) NDF digestibility; and 66, 60, and 57% (1) CP digestibility. Digestibility values of DM and OM were greater (P < 0.001) for PP than for the BG. Digestibility of CP was greater (P = 0.001) for PP than for CB or T85, with no difference (P = 0.37) between PP and BG hays in NDF digestibility. There were no differences between CB and T85 for DM digestibility (P = 0.67), OM digestibility (P = 0.59), CP digestibility (P = 0.11), and NDF digestibility (P = 0.48). Nitrogen (P = 0.01) and P balances (P = 0.04) were greater for PP than BG hays, whereas N balance of CB was greater (P = 0.01) than that of T85. There were no differences among all hays in Ca balance (P = 0.54) and between the BG in P balance (P = 0.34). Results indicated that PP, CB, and T85 are suitable forages for horses.

Mineral balance in horses fed two supplemental silicon sources.

Numerous studies suggest that silicon (Si) supplementation is beneficial for mineral metabolism and bone health. Mineral balance studies have not been performed in horses to determine how these supplements affect absorption of other minerals. The purpose of these studies was to investigate the effects of two different Si supplements on mineral absorption and retention in horses. Eight geldings were randomly placed in one of two groups: control (CO) or supplemental Si, which was provided by one of two supplements. The first, sodium aluminium silicate (SA), contains a bioavailable form of Si and is high in aluminium (Al). The second supplement contains oligomeric orthosilicic acid (OSA). All horses received textured feed and ad libitum access to hay. Supplemented horses received either 200 g of SA or 28.6 ml of OSA per day. Following a 10-day adaptation period, the horses underwent a 3-day total collection. Blood samples were taken on days 0 and 13. The two balance studies were conducted 4 months apart to reduce carryover effects. Intakes of Al and Si were greater with SA supplementation (p < 0.05). Sodium aluminium silicate increased faecal and urinary Si excretion (p < 0.05). Calcium retention and apparent digestion were increased by SA (p < 0.05). It also maintained plasma Si compared with the CO which tended to have a decrease in plasma Si (p = 0.08). Supplemental OSA increased retention of Ca and B (p < 0.05) and apparent digestion of B (p < 0.01). Orthosilicic acid tended to increase Si retention (p = 0.054), apparent digestion (p < 0.065), and also increased plasma Si. Both supplements were able to alter Ca retention and B metabolism, however, only OSA was able to alter Si retention, digestibility and plasma concentration. Orthosilicic acid, an Si supplement without substantial Al, appears to be a viable option for Si supplementation as it increased Si retention and digestibility.

The effect of ambient temperature and saline loading on changes in plasma and urine electrolytes (Na+ and K+) following exercise.

In this study 4 Standardbred geldings (age 3-8 years, weight 431-531 kg) were used. The horses were fed a hay and oat diet and the total sodium intake was about 32 mg/kg bwt (690 mmol/day). An exercise test (ET) which contained 3 phases was performed. Phase I consisted of 23.5 min of mainly submaximal exercise, Phase 2 of 2 h of box rest and Phase 3 of 26 min of exercise including an intensive trot over 2600 m at 90% of VO2max. The ET was repeated 3 times: the first at 20 degrees C (30-40% RH), the second at 35 degrees C (30-40% RH) and the third at 35 degrees C (30-40% RH) after a nasogastric administration of 10 litres of 0.9% NaCl solution (35 degrees C and saline load [+ F]). Blood samples were taken before, during and after exercise. To measure fluid loss, horses were weighted before and after the ETs. Total urine output was determined 2 days before the ET (control), throughout the exercise day and for 2 days after (recovery days). There were an increase in blood and rectal temperatures after both exercise phases and a significant higher blood temperature was observed after exercise at 35 degrees C compared to 20 degrees C. The horses lost about 2% of their bodyweight (bwt) during the ETs. The plasma protein concentration increased during the exercise phases and remained elevated 2 h after exercise at both 20 degrees C and 35 degrees C, even though the horses had free access to water. The plasma protein concentration had returned to pre-exercise levels 26 h post exercise. After the saline load, total plasma protein concentration fell and increased only at the end of each exercise phase. The major mechanism regulating fluid balance after exercise seemed to be a lowered urinary excretion since water intake did not increase significantly. Urinary potassium excretion was positive throughout the experiment. During control days there was a positive sodium balance, shown by a urinary sodium excretion of 260 mmol/day. Post exercise urinary sodium excretion fell and remained very low until the second day of recovery, except after saline loading. In addition, plasma sodium was lowered 26 h after exercise at 35 degrees C. This study shows that with a daily salt intake of 38 g it will take several days to compensate for a sodium loss caused by sweating. Therefore, it is recommended that extra salt be given during the exercise day. In the experimental situation, pre-exercise saline supplementation was beneficial since the recovery time was shortened.

Urinary indices of horses after intravenous administration of crystalloid solutions.

Saline or glucose solution was infused for approximately 4 hours into six healthy mares in two separate experiments to determine the effect of infusion of crystalloid solutions on fractional excretion (FE) of sodium (Na), chloride (Cl), potassium (K), and phosphorus (P), ratio of urinary creatinine to serum creatinine (UCr/SCr), and ratio of urinary osmolality to serum osmolality (Uosm/Sosm). After intravenous infusion of either saline or glucose solution, FENa, FECl and FEP were significantly increased, whereas UCr/SCr and Uosm/Sosm were significantly decreased. In addition, FEK was significantly increased after infusion of glucose solution. It was concluded that urinary indices were altered by intravenous infusion of crystalloid solutions in healthy mares and that fluid therapy may interfere with the use of these indices for diagnostic purposes.

Equine urine pH: normal population distributions and methods of acidification.

Our investigation of the urine of grazing horses at the University of Kentucky shows that the mean pH level is about 7.9, and if their diet is supplemented with grain, it is about 7.4. There appears to be no significant effect of time of day or year on urine pH levels in horses. However, horses taken from pasture and supplemented with grain in a stalled environment show a slight decrease in urine pH. Additionally, we investigated the effects of storage on pH levels. Equine urine samples appear to be quite stable with regard to pH for 48h, but then show a marked increase. Urine pH can have a great effect on the urine concentration of some drugs and therefore, uncertainties can arise when data generated in grazing horses are compared or extrapolated to racing horses whose urine pH can be quite low. In an effort to simulate the drop in urine pH seen in some racing horses, we examined the effects of ammonium chloride, ascorbic acid, lactic acid and methionine on urine pH in research horses. Both oral and intravenous routes of administration were used. Although all agents tested showed varying degrees of efficacy, oral administration of ascorbic acid proved to be the safest and most effective agent to model the rapid acidification of urine seen in post race samples.

24-hour renal clearance and excretion of endogenous substances in the mare.

Urine samples were obtained from 6 healthy mares. During a 2-day acclimation period, mares were kept in stalls, fed sweet feed and mixed grass hay, and allowed free access to water and trace mineral salt. The mares were crosstied in their stalls within reach of hay, salt, and water for 24 hours during which urine was obtained by constant flow via indwelling Foley catheters. Twenty-four-hour urine production was 7,649 to 11,904 ml/day (mean = 9,212 +/- 1,9285) or 14.7 to 25.1 mlg/day. (mean = 19.3 +/- 4.1). Urinary excretion and clearance of electrolytes and protein were determined from aliquots of well-mixed, pooled 24-hour urine samples. These values were sodium (Na) = 0 to 1.7 mEq/kg/day (mean = 0.4 +/- 0.7), chloride (Cl) = 2.0 to 4.2 mEq/kg/day (mean = 3.0 +/- 0.8), phosphorous (P) = 0.03 to 0.12 mg/kg/day (mean = 0.07 +/- 0.3), potassium (K) = 3.7 to 6.5 mEq/kg/day (mean = 5.3 +/- 1.4), and creatinine (Cr) = 32.1 to 53.9 mg/kg/day (mean = 40.3 +/- 8.5). Fractional excretions of electrolytes were Na = 0% to 0.46% (mean = 0.1 +/- 0.2), Cl = 0.48% to 1.64% (mean = 1.14 +/- 0.45), P = 0.04% to 0.16% (mean = 0.08 +/- 0.04), and K = 23.9% to 75.1% (mean = 51.7 +/- 17.3). Average clearances (ml/hr/kg) were Na = 0.12 +/- 0.19, K = 64.1 +/- 17.1, Cl = 1.21 +/- 0.33, and P = 0.09 +/- 0.51. Average endogenous Cr clearance (ml/min/kg) was 1.92 +/- 0.51.(ABSTRACT TRUNCATED AT 250 WORDS)

Assessment of the calcium and phosphorus nutrition in horses by analysis of urine.

Studied were made to determine if a practical assessment of the calcium and phosphorus nutrition of horses could be obtained from an analysis of urine samples. The concentrations of Ca and P in urine samples changed markedly when groups of 4 mares were fed diets containing from 1.0 to 3.9 g Ca/kg and from 1.5 to 6.1 g P/kg, but serum concentrations of Ca and P remained relatively constant. The concentrations in single urine samples were considered unreliable indicators of excretion of the minerals because of variations in water excretion, and two methods to overcome this problem were examined. In one method, the creatinine clearance ratios (%Cr) of Ca and P were calculated. The other method was simpler, and concentrations of the minerals were expressed as the ratio of the total solute concentration. Both of these methods appeared to give reliable estimates of the excretion of Ca and P in urine, and there were significant relationships between the values obtained for horses fed diets containing a wide range of Ca and P. When the horses were fed adequate Ca, the Ca-%Cr was greater than 2.5% and P-%Cr was less than 4%. The corresponding ratios of mineral concentration to solute concentration were greater than 15 mumole Ca/mosmole and less than 15 mumole P/mosmole. When a low Ca (1.0 g/kg) and high P (4 g/kg) diet was fed, the excretion of Ca and P had changed markedly after 3 days and could be monitored in single samples of urine by either method. It was concluded that a practical assessment of the Ca and P nutrition of horses could be obtained from an analysis of urine samples to determine if the diet is either low, adequate or high in Ca, and high in P.

An examination of the calcium and phosphorus nutrition of thoroughbred racehorses.

The calcium and phosphorus nutrition of thoroughbred racehorses was assessed by analysis of serum and urine samples collected from 90 horses in 1975 and 139 horses in 1980-81 at racetracks in Melbourne. Horses that were excreting greater than 15 mumole Ca/mosmole and which had a calcium to creatinine clearance ratio greater tha 2.5% were considered to have adequate Ca intake. Horses that were excreting greater than 15 mumole P/mosmole and which had a phosphorus to creatinine clearance ratio greater than 4% were considered to have excessive phosphorus intake. Sixty-percent of the horses sampled had adequate Ca intake, and 44% had excessive intakes of P. Twenty-five percent of the horses were excreting more P in urine than Ca. This would indicate these horses were subjected to nutritional secondary hyperparathyroidism, and horses entered in races by 53 of 99 trainers were in this category. It may be concluded that a high proportion (40%) of thoroughbred racehorses receive inadequate calcium nutrition while they are fed high-grain diets during racing.