RESUMEN
The objective of the present work was to assess the influence of partial replacement of oats with dried unmolassed sugar beet pulp (SBP) and/or maize oil on nutrient utilisation in horses fed a traditional hay and concentrate diet. The total tract digestibility of nutrients, urinary excretion and plasma parameters were studied in a 4 x 4 Latin-square design experiment with purebred Arabian geldings. Horses fed the SBP diets responded with a reduced (P<0.05) apparent digestibility of crude protein and feeding of maize oil resulted in an increased (P<0.05) apparent digestibility of crude fat. The apparent energy digestibility was unaffected by the replacement of oats with SBP, but increased (P<0.05) when maize oil replaced part of the oats. The urinary excretion of nitrogen increased (P<0.05) when maize oil replaced oats and the excretion of energy was higher (P<0.05) on the diets where oats were replaced by maize oil and SBP. There was a significant (P<0.05) effect across treatments of postprandial blood sampling time on plasma glucose and insulin concentrations. Also, plasma concentrations of glucose and insulin tended to be higher on the oats than on the SBP diets. In conclusion, the limited effects on the digestibility of nutrients and energy suggest that it should be possible to partially replace oats with maize oil and/or SBP in diets for horses without any impairing effects on the overall nutrient utilisation. However, the dietary-induced changes in the urinary excretion of energy and on plasma glucose and insulin levels, indicate a possible influence of dietary carbohydrate composition on nutrient utilisation at the organ level, which requires further study.