Nutrient digestibility of veal calves fed large amounts of different solid feeds during the first 80 days of fattening

The study aimed at evaluating nutrients apparent digestibility in veal calves fed 3 feeding plans based on milk-replacer plus large amounts of solid feeds differing in their composition during the first 80 days of fattening. Twelve Polish Friesian male calves (70.6 +/- 1.9 kg) were randomly assigned to one of the following feeding treatments:i) milk-replacer plus corn grain (CG); ii) milk-replacer plus 80:20 mixture (as fed basis) of corn grain and wheat straw (CGS); and iii) milk-replacer plus 72:20:8 mixture of corn grain, wheat straw and extruded soybean (CGSES). Calves received the same milk-replacer but the daily amount was restricted (96%) for CGSES calves to balance dietary protein. Total dry matter intake from milk-replacer and solid feeds was similar among treatments, but CGSES calves showed better growth performance than CG ones. Calves were introduced into a metabolism stall (1/pen) during week 9 of fattening for a 3-day adaptation period and a 4-day digestibility trial. Calves fed CG showed the greatest DM, NFC, and ash digestibility while CGSES calves showed the lowest CP digestibility. Haemoglobin concentrations measured at day 5, 31 and 80 were similar among feeding treatments and significantly decreased over time. In CGSES treatment, the combination of milk-replacer with solid feed closer to a complete diet for ruminants led to better calves' growth performance. However, the reduced protein digestibility with CGSES indicates that protein quality becomes a key factor when formulating diets for veal calves using alternatives to dairy sources.