Effects of algal supplementation on broiler chicken growth performance, gut development, blood leukocyte counts and antibody levels.

Brown macroalgae contains complex polysaccharides including laminarins that have shown prebiotic potential. The aim of this study was to investigate if feeding algal products from Saccharina latissima to either broiler breeders or directly to their chickens could affect growth performance, gut- and immune development in the chickens. A total of 45 hens of the parent line of Ross 308 were used to obtain fertilised eggs. The hens were fed one of three experimental diets, a control, the addition of 0.6% algal meal or addition of 0.08% algal extract. The progenies of those hens were followed in an experiment using a split-plot design where eggs from the three hen treatments were distributed into 24 modules. Half of the modules were assigned a control diet, and half of the modules were a diet supplemented with 725 ppm algal extract. A total of 255 chicks remained after hatching and individual marking, they were weighed at hatch, on days 3, 7, 14, and 37 and blood samples for determination of leukocyte counts and serum antibody levels were drawn on days 3, 7 and 12. Chickens were killed to assess organ development at days 7, 14 and 37, and histological examination of ileal tissue was performed on day 7. The results showed that chicks fed the algal extract diet had higher (P < 0.05) BW on days 3, 7 and 37, a higher proportion of serum immunoglobulin Y (IgY) and a lower proportion of maternal antibodies to infectious bronchitis virus on day 12 (P < 0.05). Chicks fed algal extract showed higher numbers (P < 0.05) of CD4+CD8- helper T-cells and total T-cell receptor (TCR)γ/δ+ T-cells, and among the TCRγ/δ+ T-cell subpopulations, the TCRγ/δ+CD8- T-cells were increased, and lower (P < 0.05) numbers of cluster of differentiation (CD)4+CD8αα+ and TCRγ/δ+CD8αβ+ T-cells in the circulation. Feeding algal extract to the breeders resulted in higher chick BW on day 7, and the villus height-to-crypt depth ratio was higher (P < 0.05) for chicks from hens fed algal extract than for chicks from hens fed algal meal. In conclusion, feeding algal extract from Saccharina latissima directly to the chicken improved growth performance throughout the growing period and altered the composition of T-cell populations in the circulation and may have enhanced the chicks' IgY production. Maternal supplementation of algal extract to breeder hens had positive effects on the chickens' early growth performance and gut architecture. However, no synergistic effects of both maternal feeding and direct supplementation to the chicken were found.