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Impact of low-quality soybean meal and live coccidiosis vaccination on performance, relative organ weights, and heterophil:lymphocyte ratio in broiler chickens

Coles, M., A. Forga, K. Teague, R. Wolfenden, J. Liu , J. Latorre, G. Tellez-Isaias, B. Hargis and B. Graham
2024

Dietary soybean meal (SBM) quality can negatively impact intestinal health and performance in broiler chickens. The purpose of the present study was to develop a model to compare the effects of dietary SBM quality and live coccidiosis vaccine cycling on organ weights and performance in broiler chickens. At day of hatch (DOH), chicks were randomly assigned to one of two groups (n=12 pens/group): 1) high-quality (HQ) SBM or 2) low-quality (LQ) SBM. Group 1 received HQ SBM diet formulated to meet or exceed requirements. Group 2 received LQ SBM diet designed to induce inflammation resulting in lower body weight (BW) and decreased feed conversion ratio (FCR). The LQ SBM was produced using a 1:1:1 mixture of uncooked SBM, normal SBM, and overprocessed SBM (autoclaved ~125C for 60 minutes). Chicks were orally gavaged with a 1X dose of a commercial live coccidiosis vaccine containing E. acervulina, E. tenella and E. maxima at DOH. Pen weights were recorded at DOH and weekly thereafter to determine average BW and BW gain. Feed was weighed weekly to calculate feed conversion ratio (FCR) and feed intake (FI). On D15, D28, and D42, individual organ weights were recorded (n=24 chickens/treatment) to calculate relative organ weights (%). Blood was also collected (n=10 chickens/treatment) to assess heterophil:lymphocyte ratio (H:L ratio). Data were analyzed using Analysis of Variance with significantly (P≤0.05) different means separated using Student’s T-test. Average BW (g) was significantly higher in the HQ group than the LQ group at D7, D21 and D28. At D42, the HQ group had an average BW significantly higher than the LQ group. Both average BWG (g) and FCR were significantly improved from D0-D42 for the HQ group compared to the LQ. Additionally, the LQ group had significantly higher relative whole gut and pancreas weight (%) than the HQ group on D15, D28 and D42, whereas the HQ group had markedly (P ≤ 0.05) higher liver and spleen weights (%) on D15. There were no statistical differences between the two groups at any time point evaluated for H:L ratio.

These results indicate that the LQ SBM diet reduced overall performance and impacted organ development in broiler chickens. The impact of these dietary treatments on the gut microbiome is currently being evaluated.