Effects of Phenolic-Rich Onion (Allium cepa L.) Extract on the Growth Performance, Behavior, Intestinal Histology, Amino Acid Digestibility, Antioxidant Activity, and the Immune Status of Broiler Chickens

Abstract

The effect of phenolic-rich onion extract (PROE), as a feed additive, was evaluated on the growth, carcass traits, behavior, welfare, intestinal histology, amino acid ileal digestibility "AID%," and the immune status of broiler chicks for 35 days. A total number of 400, 1-day-old broiler chicks (45.38 g ± 1.35) were allocated to four different treatments with 10 replicates each (100 chicks/treatment) consisting of: T1, basal diet without additives (control treatment) (PROE0); T2, basal diet + phenolic-rich onion extract (1 g/kg diet) (PROE1); T3, basal diet + phenolic-rich onion extract (2 g/kg diet) (PROE2); and T4, basal diet + phenolic-rich onion extract (3 g/kg diet) (PROE3). An increase in the final body weight "FBW," bodyweight gain "BWG," and feed consumption was observed (P < 0.05) at different PROE levels. Also, the thymus and bursa percentages were increased in the PROE2 and PROE3 treatments (P < 0.05). The chicks fed on PROE supplemented diets had increased frequency of feeding and drinking and showed comfortable behavior (P < 0.05) with lesser aggression (P < 0.05). Additionally, an increase was observed in the antioxidant enzyme activity, phagocytic %, phagocytic index, and serum lysozyme activity in PROE supplemented treatments, with the best outcome reported in the PROE3 treatment (P < 0.01). IgM was increased in the birds fed with PROE2 and PROE3 diets (P < 0.01). PROE supplementation increased the AID% of lysine and methionine (P <0.01), PROE3 treatment increased the AID% of threonine (P < 0.05), and PROE2 and PROE3 treatments increased the AID% of leucine and isoleucine (P < 0.05). Besides, PROE2, and PROE3 treatments increased the villus height and width, mucosal thickness, and goblet cell count from the duodena, jejuna, and ilea (P < 0.05) compared to control treatment. Based on these results, we concluded that the dietary addition of phenolic-rich onion extracts can improve the growth rate of broiler chicken by improving the AID% of amino acids and intestinal histology. Also, it can improve the welfare, antioxidant enzymes activity, and immune status of the birds. Phenolic-rich onion extracts can be used as a natural growth promoter in the poultry feed for good health and improved performance.

Keywords: behavior; broiler—chicken; growth performance; gut histomorphology; immunity; onion extract.

Figure 1

Representative images showing normal (A), mild (B), moderate (C), and marked (D) phagocytic activities in PROE0, PROE1, PROE2, and PROE3 treatments, respectively.

Figure 2

A representative photomicrograph of 40× magnification H&E stained small intestine sections of the broiler chickens. The sections from the duodenal segments from PROE0group showed separate tall and arranged intestinal villi with (arrow) free lumen (A), the duodenal segments from PROE1 group showed apparently separated tall and arranged intestinal villi with free lumen (B), the duodenal segments from PROE2 group revealed marked active intestinal villi and crypts which characterized by limited goblet cells metaplasia (star)' increased sizes and rows of enterocytes (thick arrow) with arranged lamina propria beside some desquamated villi (small arrow) (C). Chicken fed on PROE3 diet revealed marked thin, tall, and separate villi with mild goblet cell proliferations (star) (D).

Figure 3

A representative photomicrograph of 40× magnification H&E stained small intestine sections of the broiler chickens. The sections from the jejunal segments of PROE0 group showed free lumen with nearly normal villus structures (A), the sections from the jejunal segments of PROE1 group showed free lumen, a few denuded villi tips with increase intestinal crypt layer depth (towheads arrow) besides partial fusion (arrow) (B), and the jejunal segments from PROE2 group showed separate tall villi and marked serrated surfaces (arrows) with goblet cell metaplasia (star) beside partial fusion some villus (C). In addition to, increased intestinal glands layer besides partial destructed villi with some fusion's villi (star) were observed in PROE3 group (D).

Figure 4

A representative photomicrograph of 40× magnification H&E stained small intestine sections of the broiler chickens. The sections from the ileal segments of PROE0 group showed free lumen and nearly normal limit gut associated lymphoid follicles (star) with a few denuded villi (arrow) (A), the sections from ileal segments of PROE1 group showed thickened and serrated (arrow) of villi due to enterocytes and goblet cell metaplasia (stars) with narrowing of the lamina propria (B). The sections from PROE2 group showed marked hyperplastic intestinal gut associated lymphoid follicles (star) (C). The sections from PROE3 showed marked fusion villi due to increase enterocytes proliferations and goblet cells metaplasia (star) (D).