Dietary alfalfa hay or lipid-soluble alfalfa extract may improve broiler growth, but fiber presence may be detrimental during Eimeria vaccine challenge

Abstract

Lipid-soluble components in late-cutting alfalfa are linked to beneficial immune and microbiota responses in mouse challenge models; therefore, responses in a comparative poultry Eimeria challenge model were investigated. The study objective was to evaluate performance, immunity, and the cecal microbiota in broilers fed ground hay or lipid-soluble extract from late (fifth) cutting alfalfa during Eimeria challenge. At hatch, 432 Ross 708 broilers were placed in 24 floor pens (18 birds/pen) and assigned to 3 isocaloric/isonitrogenous dietary treatments consisting of control, 5% ground hay, or 0.25% lipid-soluble extract for a 42-d trial divided into 14 d starter, grower, and finisher periods. On d 14, 4 birds/treatment were euthanized to collect blood and cecal contents before half the remainder were inoculated with 10X Merck Coccivac-B52 (Kenilworth, NJ). Tissue samples were collected at 3, 7, 14, and 28 d postinoculation (pi; 4 birds/diet×Eimeria group) with body weight (BW) and feed intake (FI) recorded weekly. Immune populations within peripheral blood mononuclear cells were characterized by flow cytometry while cecal microbial communities were profiled by 16S rRNA gene amplicon sequencing. Data were normalized when appropriate and analyzed to evaluate the effects of diet, Eimeria challenge, and timepoint (SAS 9.4; P ≤ 0.05). Before challenge, dietary alfalfa hay or extract increased FI 6.9 to 8.0% and increased CD3+ T cells 19.3 to 24.9% compared to control-fed birds (P ≤ 0.007). Alfalfa did not significantly affect post-Eimeria performance, but Eimeria-challenged birds fed hay showed the greatest numeric reduction in final BW compared to their unchallenged counterparts (0.17 kg) vs. control and extract-fed birds (0.02-0.04 kg). Immune cell changes did not indicate recruitment from peripheral blood to local infection sites; however, alfalfa hay may have accelerated Bu-1+ B cell development by 7 d in unchallenged birds (P < 0.0001). During Eimeria-challenge, dietary alfalfa extract preserved alpha diversity measures related to species richness (P ≤ 0.007). Collectively, these results indicate potential benefits of feeding lipid-soluble extract from late cutting alfalfa to broilers during Eimeria challenge.