Elite three-day event horses are over-supplemented during competition

The objective of this study was to analyse the daily intake of vitamin E and some minerals fed or supplemented to horses competing in the Jersey Fresh CCI two-star and CCI three-star (n = 35) Three-Day Event. Riders gave informed consent to use their horses and nutritional information prior to the start of the study. Concentrate, hay and bran were weighed and each horse's body weight and body condition score were taken. Total nutrient intake was calculated using information provided by the manufacturer or from the NRC (2007). Recommended daily intakes were calculated for each horse in very heavy exercise using NRC (2007) equations. Differences between nutrient intake and requirement were determined using a Student's t-test. Average number of supplements fed on a regular basis was 4.3 ± 0.6. The most administered type of oral supplement was electrolytes (89%) followed by salt (69%) and oral joint supplements (63%). The intake of vitamin E was higher than recommended (1667 ± 282 vs. 1065 ± 93 IU/d; p = 0.03). Intake amounts of several minerals were also higher than recommended including potassium (248.4 ± 15.7 vs. 56.4 ± 4.9 g/d; p < 0.0001), phosphorus (57.9 ± 4.2 vs. 31.0 ± 2.7 g/d; p < 0.0001), calcium (110.5 ± 42.4 vs. 42.5 ± 3.7 g/d; p < 0.0001), and magnesium (35.5 ± 2.0 vs. 15.9 ± 1.4 g/d; p = 0.0004). Sodium intake, excluding the amount received from an ad libitum salt or mineral block, was not different from the daily recommended amount (43.5 ± 28.7 vs. 43.6 ± 3.8 g/d, respectively; p = 0.49). While vitamin E, calcium, and magnesium were in excess of the daily recommended amounts, they did not reach toxic levels. Average potassium intake exceeded the toxic levels, which could cause cardiac arrhythmias and muscle tremors in intensely exercising horses. The excess phosphorus would not be harmful unless it lowered the recommended calcium:phosphorus ratio of 2:1. While over-supplementation of horses can be harmful to their health, it is also an economic burden that is unnecessary. Lastly over-supplementation of horses should be avoided to reduce the environmental impact of excess nutrients excreted in urine and faeces.