Thoroughbred blood serum inorganic phosphate concentrations in relation to feeding regime and racing performance

Horses receiving a pelleted or cubed dietary supplementation with roughage, have serum inorganic phosphate (SIP) concentrations consistently below an accepted mean of 1,032 mmol l-1 or 3, 1 mg dl-1. Further, it has been reported that the best eight, two-year-old Irish Thoroughbred track performers of 51 horses tested over a 10 month period, had significantly lower SIP concentrations than the worst eight track performers. In an endeavour to assess any nutritive effect on SIP concentrations and also to assess any effect of SIP concentrations on track performance, metabolic blood profiles from 303 horses in training at the Summerveld Training centre in Natal, were evaluated for various blood parameters over a two year period. Of these 303 profiles, 264 were analysed for SIP concentrations. These horses were on three known feeding regimes viz. Feed 1--cube feeding plus hay; Feed 2--oats, wheaten bran and greens plus hay; Feed 3--Mixed feeding regime of feeds 1 and 2; Feed 4--unknown regime. Dry matter intake varied between 2 and 2.5% of estimated bodymass and in the Feed 1 regime, the proportion of cubed supplement in the diet was increased from 30 to 70% as the training programme progressed. Statistical analysis of SIP concentrations showed that horses on the Feed 1 regime had significantly lower SIP concentrations than horses on the other feed regimes. Of the 303 profiles, 224 could be identified with actual races.(ABSTRACT TRUNCATED AT 250 WORDS)