A methodological approach to the estimation of fecal and urinary losses in horses.

The aim of this work was to evaluate the urinary and faecal losses in horses fed three diets differing for forage/concentrate ratio (diet 1:100 % hay, diet 2: 75% hay + 25% of a mixed feed, diet 3: 50% hay + 50% of the same mixed feed) at a feeding level close to maintenance. The trials were performed on 4 saddle horses weighting about 550 kg, over a 6 day faeces and urines total collection period after a previous 14 day adaptation period. A horse diaper was utilised for the fecal and urine collection. Food consumption was recorded daily. Before analysis, the faecal and urinal samples were freeze-dried and ground. Analyses on all samples for dry matter and N were carried out according to the standard methods of Association of Official Analytical Chemists 1990 . The gross energy was determined with an adiabatic calorimeter bomb (IKA C7000, Staufen, Germany). The percentages of nitrogen retention and nitrogen digestibility, the metabolisable energy (ME) and digestible energy (DE) percentages on gross energy were measured by the ingesta/excreta procedure and by taking into account the urinary losses for all the rations. The nitrogen digestibility and retention increased (P < 0.01) with increasing amounts of the mixed feed in the ration; the same trend, even if not significant, was found for the metabolizable energy and digestibility of gross energy percentages. The urine energy was very low. The digestible crude protein of the diet 1 (100 % hay) determined by difference between nitrogen intake and nitrogen in the faeces was compared with the data obtained with the regression equations formulated by Martin-Rosset (1994), the result were found to be similar. The digestibility of energy of the diet 1, determined from digestibility of organic matter by the equations and the ME/DE ratio was also near to the one measured in the trial.