Broiler Chicken Immune Response to Stevioside

The animal experiments were performed in accordance with the Animal Care and Use Committee of Nanjing Agricultural University, Nanjing, China (PZ2019064). A total of 192 one-day-old male Ross 308 broiler chicks with similar hatching weights were purchased from a local commercial hatchery. Broilers were randomly allocated to four treatments. Each treatment contained six replicates (cages) of eight broilers per replicate in each group. The present experiment lasted for 21 d (from 1 to 21 d of age). The basal diet used in this study was according to National Research Council (1994) (Table 1). The four experimental treatments were as follows: (1) non-challenged broilers fed a basal diet (CON); (2) non-challenged broilers fed a basal diet supplemented with 250 mg/kg stevioside (STE); (3) LPS-challenged broilers fed a basal diet (LPS); (4) LPS-challenged broilers fed a basal diet supplemented with 250 mg/kg stevioside (LPS + STE). Stevioside used in this study were purchased from Macklin Inc (Shanghai, China) with a purity of more than 98%. The supplemental stevioside level was optimized according to previous studies [11 (link),14 (link),19 (link)]. All broilers were housed in four-level cages in a temperature- and light-controlled room with continuous light in Nanjing Agricultural University. All broilers had ad libitum access to mash feed and water. The temperature of the room was maintained at 32 to 34 °C for a week, and it was then gradually decreased by 1 °C every 2 d until a final temperature of 26 °C was achieved. Furthermore, all broilers were inoculated with a Newcastle disease vaccine on 7 d and with an inactivated infectious bursal disease vaccine on 14 d. The experiment consisted of a 2 × 2 factorial design. The main factors were (1) Lipopolysaccharide (LPS)-challenge, injection with LPS or saline, and (2) diet, basal diet with 0 or 250 mg/kg stevioside. LPS from Escherichia coli (L2880, Sigma Aldrich Inc., St. Louis, MO, USA) was dissolved in 0.9% sterile saline solution. At 7:00 am of 17, 19, and 21 d, LPS-challenged groups received an intraperitoneal injection of LPS solution at a dose of 1 mg/kg, whereas the CON and STE groups received a sterile saline injection. The dosage and injection of LPS were referred to as available findings [2 (link),22 (link)]. At 17 d and 21 d, all broilers were weighed to calculate average daily gain (ADG). The feed consumption by the broilers in a replicate (cage) was recorded to calculate average daily feed intake (ADFI). The spilled feed was carefully collected and weighed in order to correct the final data of ADFI. Feed conversion rate (FCR) was defined as ADFI: ADG.
Provided the following % per kilogram in completed diet: vitamin A, 12,500 IU; vitamin D3, 2500 IU; vitamin E, 80 mg; vitamin K, 2.65 mg; vitamin B1, 2 mg; vitamin B2, 6 mg; nicotinic acid, 50 mg; pantothenic acid, 20 mg; vitamin B6, 4 mg; folic acid, 1.25 mg; vitamin B12, 0.025 mg; biotin, 0.0325 mg; folic acid, 1.25 mg; pantothenic acid, 12 mg; niacin, 50 mg; Fe, 80 mg; Zn, 75 mg; Mn, 100 mg; Cu, 8 mg; I, 0.35 mg; Co, 0.2 mg; and Se, 0.15 mg.