Feeding leghorn chicks during simulated transport as an early feeding strategy and the benefits of a single spray probiotic application

This study examined early, interrupted, or no feeding, with (P) or without (N) a spray-on probiotic (Lactobacillus reuteri), on chick stress, growth, gastrointestinal tract (GIT) development, microbiota, and gene expression during and after simulated transport (ST; 24 Hz vibration, 25°C, uncontrolled humidity). Lohmann LSL-Lite chicks (n = 1520) underwent 24 h of ST (5 h post-hatch) with either 24, 16, 8, or 0 h of feed access (FA) during ST with P or N treatment (trt). Following ST, birds were housed in pens for 14 d (5 replications/trt). Body weight, blood chemistry and heterophil-to-lymphocyte (H/L) ratio, relative length, weight and histomorphology of the GIT, quantitative PCR for ileum expression of genes related to inflammation and gut-barrier function, and microbiome analysis were assessed. At d 7 and 14, P birds were heavier. On d 1 (post-ST), H/L ratios were higher in the P trt, possibly from immunostimulation. Blood pH was lowest, and ionized calcium was highest in the 8-h trt. Glucose was higher in the N trt, and more dehydration occurred in the 0- and 8-h trt. The 0-h trt had reduced small intestine length and weight, and jejunum weight was highest in the P trt on d1. On d 7, duodenum and ileum weight were lowest for 8 h and N, respectively. Histomorphology revealed interactions in the ileum and cecum, suggestive of P preventing delayed gut development with interrupted FA. On d 1, ileum IL-6 expression was greater for 0 compared to 24 h. The P trt had a lower microbiome diversity but may have improved gut development with interrupted FA and prevented dehydration in the 0- and 8-h trt. Interrupting FA after 8 h had more negative effects than 0-h FA. With 0-h FA during ST, GIT development was delayed and could have contributed to ileum inflammation. Early FA had a positive effect on leghorn chick health, gut development, and growth. One post-hatch spray application of P may improve chick well-being over long transport durations.