Early access to feed, water and <i>Neurospora intermedia</i> in broiler starter diet (part II) – caecal microbiota, antibody production and blood leukocyte counts

1. This study examined the effects of providing feed and water immediately post hatch in combination with inclusion of <i>Neurospora intermedia</i> biomass in chick starter diet, as a source of protein and bioactive compounds. Variables monitored were caecal microbiota, total levels of IgY, specific antibody responses to vaccination and blood leukocyte counts.2. Ross 308 chicks were subjected to two hatching treatments - immediate access to feed and water, or delayed access at 48 h. In addition, three starter diets were fed until d 10: a control diet (C), a diet with inclusion of 10% <i>N. intermedia</i> (N) or diet N followed by diet C (NC).3. Chicks were vaccinated against avian pneumovirus (APV) and focal birds were repeatedly blood sampled for quantification of total IgY and antibodies specific to APV in serum. Birds fed starter diet C were sampled for measures of blood leukocyte counts. Caecal microbiota were studied in birds sacrificed on d 5, 9 and 43, respectively.4. With age, microbial richness in caeca increased and there was a shift in composition, but no effects of hatching treatment or starter diet were observed.5. Neither the starter diet nor the hatching treatment affected the total IgY in serum or specific antibody responses to APV vaccination. Late-fed chicks had a significant decrease in the total amount of IgY in serum from d 2 to d 8, likely a consequence of dehydration at d 2. Early feeding did not affect any of the leukocyte populations monitored.6. In conclusion, there were no effects of early feeding or inclusion of <i>N. intermedia</i> on gut microbiome or the immune traits monitored. However, the absence of adverse effects of a starter diet with the fungal biomass suggested that <i>N. intermedia</i> is a source of high-quality protein.