Oral magnesium supplementation and its effects on magnesium balance in horses

Research output: Other contribution to conferenceAbstractpeer-review


Oral magnesium (Mg) is commonly used in mineral supplements that help fortify or balance equine diets. It is also frequently included in products aimed at positive behavioural support. However, little is known about the effect of supplementation on magnesium balance and homeostasis in the equine. As a part of a larger study into the potential efficacy of oral Mg supplementation on flight reaction speed, the effects of Mg supplementation on Mg balance were investigated.Materials and methods: Six mature Standardbred geldings (mean BW 415 ± 39.53 kg) being rested from harness racing (for at least 2 months prior to study) were used in a randomised latin square design with 3 x 7 day periods. Each horse acted as its own control. The base ration comprised 300 g of low energy pellets 11.0 MJ/kg (Cool Conditioner, Coprice), plus clover/rye grass hay fed at 2% BW (as fed basis). Three dietary treatments were evaluated. Base ration (total mean daily Mg intake 15.5 ± 0.586g), base ration with 2.5g added Mg (total mean daily Mg intake 17.83 ± 0.586g) and base ration with 10g added Mg (total mean daily Mg intake 25.8 ± 0.586g). Horses were fed each ration divided into 2 daily meals over the 7 days. On Day 6, total urine collections were made in order to monitor Mg urinary excretion; urine was freely voided on demand (previously trained to urinate on a whistle) and collected at many time points over the 24 hours. No urination occurred between these time points for any horse, as nappies collected urine when not freely voided. For faecal sample collection, horses wore equine nappies. The nappies were emptied as needed, samples were weighed and subsampled and then pooled for each horse. All horses were kept in individual dry lots that allowed free exercise and were fully accustomed to wearing the nappies. Environmental conditions were temperate. Samples were analysed for Mg concentration using ICP–OES (Inductively Coupled Plasma-Optical Emission Spectroscopy: limit of detection < 0.1 ppb for Mg). Magnesium balance was calculated using the equation: Mg balance = [(Mg intake – (Faecal Mg + Urinary Mg)]. Sweat and other evaporative losses were estimated to be low and excluded. For statistical data analysis, SPSS 20 (SPSS, Inc) was used. A generalized linear model was fitted and P <0.05 considered to be of significance.Results: Despite marked individual variability there was a significant positive effect of Mg supplementation on magnesium balance, with a significant difference found between the Base ration and 10 g groups (P=0.012). Mean Mg balance (g/horse/day) ± sem for each treatment group was: Base ration, (-1.3 ± 2.77 g/h/day); 2.5g added Mg (3.5 ± 2.77 g/h/day); 10g added Mg (8.5 ± 2.77 g/h/day). However, even at the highest Mg intake (mean ~26g vs ~6. g as recommended by the NRC for a 415kg horse) one of the horses was still not in a positive balance (compared with 2 out of the 6 on the lower intakes).Discussion and conclusion: In this study although increasing the Mg intake helped to increase Mg status, there were significant individual differences in apparent requirements to maintain positive balance, at least in this short term study. Further work is obviously needed in this area.Acknowledgement: This study was funded by WALTHAM Centre for Pet Nutrition.
Original languageEnglish
Number of pages1
Publication statusPublished - 2017
Event21st European Society of Veterinary and Comparative Nutrition Congress - Royal Agricultural University, Cirencester, United Kingdom
Duration: 20 Sept 201723 Sept 2017


Conference21st European Society of Veterinary and Comparative Nutrition Congress
Abbreviated titleAnimal nutrition
Country/TerritoryUnited Kingdom
Internet address


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