Effects Of Yucca Extract On Production Performance, Digestive, Metabolic, And Immune Functions In Broilers

Effects of yucca extract (YE) on growth performance, slaughter performance, meat quality, small intestinal morphology, activity of chyme digestive enzymes, apparent metabolic rates, and immune function were studied to explore the influence of YE and provide a theoretical basis for determining its suitable level in broiler diet.Single factor completely randomized experimental design was adopted. One hundred and twenty-eight one-day-old birds were selected, and randomly assigned to 4 dietary treatments with 4 replicates of 8 chicks after a two-week pre-feeding period with basal diet. The control birds were provided the basal diet, and the birds in other three dietary treatments were fed on the basal diet supplemented with 100,200, and 300 mg/kg YE powder, respectively. The whole study was divided into the former period (15～28 day) and latter period (29～42 day), and contained five experiments as following:Experiment 1, effects of YE on growth performance and growth-related hormones in broilers. Live body weight of each bird and feed consumption were recorded when they are 15,28 and 42 days old, then the average daily gain (ADG), average daily feed intake (ADFI) and feed to gain ratio (F/G) were calculated. Two broilers were chosen randomly from each replicate group at 28 and 42 day of age, and the wing vein blood was collected and centrifuged at 4,000 r/min for 15 min. The serum was transferred for analysis of growth hormone (GH) and insulin-like growth factor-1 (IGF-1).Experiment 2, effects of YE on slaughter performance and meat quality in broilers. Body weights of 42 day-old birds were recorded after fasting for 12 h, and then the birds were slaughtered by bleeding the left jugular vein. Epilate the feather and separate the breast muscle, leg muscle and abdominal fat, and weights of carcass, semi-evisceration, evisceration, breast muscle, leg muscle and abdominal fat were measured,. then the dressing percentage (DP), semi-eviscerated percentage (SEP), eviscerated percentage (EP), percentage of breast muscle (PBM), percentage of leg muscle (PLM) and percentage of abdominal fat (PAF) were calculated. The meat color (brightness value of L*, red value a* and yellow b*), pH (45 min and 24 h), pressure loss (PL), drop loss (DL), cooked rate (CR) and shear force (SF) of breast muscle were determined.Experiment 3, effects of YE on small intestinal morphology and activity of chyme digestive enzymes in broilers. Two broilers were chosen randomly from each replicate group at 28 and 42 day of age, and front parts of their duodenum, jejunum and ileum were removed after slaughter, then rinsed with 0.9% saline, fixed with formalin, and made paraffin sections in order to observe the villus height (VH) and crypt depth (CD), and villus height/crypt depth (VH/CD) was calculated. Homogenate of 0.5 g chyme and 4.5 mL 0.9% saline was centrifuged at 2,500 r/min for 10 min, and then the supernatant was transferred and analyzed activity of trypsin (TRY), chymototrypsin (CHY), lipase (LPS) and amylase (AMY).Experiment 4, effects of YE on apparent metabolic rates of nutrients in broilers. One bird which had approximately average weight of each replicate was chosen for metabolic experiment in metabolic cages when they were 5 weeks old, and the diet and water were available ad libitum. All the three days’feces was collected, and feed consumption and feces output was recorded, then the apparent metabolic rates of dry matter (DM), crude protein (CP), ether extract (EE), calcium (Ca) and phosphorus (P) were measured.Experiment 5, effects of YE on immune function in broilers. On day 28 and 42, two broilers were chosen randomly from each replicate group, their blood samples were collected from wing vine, and then the serum samples were prepared for determining the concentrations of immunoglobulin G (IgG), immunoglobulin A (IgA), immunoglobulin M (IgM), soluble CD4 antigen (sCD4), and soluble CD8 antigen (sCD8) using Elisa kits. Then the broilers were slaughtered, and their thymus, spleen, and bursa of Fabricius were removed and weighed for calculating the immune organ index.The results were concluded as follows:1. The values of ADFI were not affected by supplement of YE (P>0.05), but ADG increased (P<0.01) by 6.30 or 5.61 percentage, and F/G decreased (P<0.05) by 8.84 or 7.18 percent of the whole period for chicks fed diets containing 100 or 200 mg/kg YE respectively, as compared to the control diet. In addition, the level of 42 day-old birds’ serum GH increased significantly by feeding 100 mg/kg YE (P<0.05).2. Supplementation of 200 mg/kg YE increased DP of 42 day-old birds, and 300 mg/kg treatment decreased PBM (P<0.05).3. Diets added 100 mg/kg YE brought higher VH of 28 day-old broilers’jejunum, as well as VH and VH/CD of 42 day-olds’duodenum (P<0.05). TRY and LPS of ileum, as well as LPS of duodenum were increased by 200 mg/kg YE at 42 day (P<0.05).4. Apparent metabolic rates of DM and CP were increased by 200 mg/kg YE (P< 0.05), what’s more, Ca and P of 100 and 200 mg/kg treatments had trend to increase but 300 to decrease (0.05<P<0.10).5. The birds’IgG at 28 day and IgM at 42 day which fed 100 mg/kg YE were significantly increased (P<0.01), sCD4 and sCD8 were decreased at different degrees, but the differences were not significant (P>0.05). When the YE supplementation was 200 mg/kg, IgA was down but IgM was up (P<0.01), and the decrease of sCD4 and sCD8 were not significant (P>0.05). Addition of 300 mg/kg YE resulted in lower IgG (28 day) and IgA (28 and 42 day) (P<0.01), sCD4 at 28 day and sCD8 at 42 day tended to decrease (0.05<P<0.10).