Veal production and quality attributes of Holstein bull calves supplemented with dietary active dry yeast (Saccharomyces cerevisiae) during pre-weaning and finishing phases

: The study investigated the effects of active dry yeast (ADY) supplementation during pre- and post-weaning on diarrhoea occurrence, animal performance, carcass attributes, and meat quality of Holstein bull calves. At five days old, 39 calves (43.56 ± 3.43 kg at birth) were stratified according to birth weight and blood total protein, then allocated to a control diet (n = 19) or an ADY-supplemented diet (n = 20) in a random order and housed individually. During pre-weaning, calves received Saccharomyces cerevisiae var. boulardii with milk replacer at ≈1 × 109 CFU/calf/day, while post-weaning supplementation consisted of Saccharomyces cerevisiae mixed into pelleted feed at 150 g/t (1.5 × 109 CFU/kg). Fecal scores were monitored until 30 days of age while starter intake and body weight were recorded until slaughter at 156 ± 15 days. The longissimus thoracis et lumborum muscles were harvested 24 h post-slaughter. ADY significantly reduced diarrhoea among calves aged 11-15 days. Milk replacer and starter intake during pre-weaning were unaffected, although post-weaning starter intake was reduced (P ≤ 0.05) in ADY-fed calves. In either phase, ADG and weight gain-to-starter intake ratio were not influenced by ADY, though overall ADG tended to increase (P < 0.10). No treatment differences were observed in carcass characteristics, meat physicochemical attributes or lipid oxidation. Colour coordinates increased from days 1 to 3, stabilized by day 7, and changed minimally thereafter, while lipid oxidation remained stable throughout. Overall, ADY supplementation reduced early-life diarrhoea without affecting growth performance, carcass attributes, or veal quality.