Apparent digestibility of mixed feed rich in by-products in horse diets

The apparent digestibilities of hay or hay plus concentrate (60:40) rich in by-products including soja hulls were determined by means of two in vivo digestibility trials, each performed on 6 saddle horses weighting about 506 kg and 503 kg, respectively, over a 6 day faeces total collection period with a previous 14 day adaptation period. The diets were based on first cut meadow hay, whose digestibility was estimated in the first trial, and on the same hay with a mixed feed in the second trials at a feeding level close to maintenance. The apparent digestibility of the dry matter, organic matter, gross energy, crude protein, NDF and ADF were measured by the ingesta/excreta procedure using a suitable device. The apparent digestibility of the concentrate was calculated from the above data. The data from two of the six horses resulted aberrant and, consequently, the paper refers to the results coming from four horses only. The results showed that the addition of the mixed feed to the hay improves the digestibility of the ration only for the crude protein, while the digestibilities of NDF and ADF were lower than those of hay alone and digestibilities of dry matter, organic matter and gross energy were steady. These results could mainly be ascribed to a negative effect of some by-products on the microflora activity in the large intestine.