| The trial was conducted to study the effects of different zinc levels added in corn-soybean meal basal diet without fishmeal on growth performance, antioxidant function, hormone metabolism and immune organ(thymus, spleen, bursa of fabricius) development of caged egg-type ducklings(1～28days), and to determine the best level of zinc adding in the meal of Jinding egg-type ducklings.Used a single factor completely randomized design, a total of180one-day-old Jinding egg-type ducklings were randomly assigned to5groups with6replicates per group, and each replicate contained6ducks. All the egg-type ducklings were fed corn-soybean meal basal diet(33.3mg Zn/kg diet) supplemented with0,20,40,60and80milligram zinc per kilogram diet (mg/kg) in the form of reagent grade ZnSO4·7H2O, respectively. The trial period lasted for4weeks. It weighed the initial weight of each repeat ducklings at the beginning of the trial, then it weighed once every week, and stop feeding at eve of weighing, and fasting weighed at the next morning. It recorded feed consumption every week, and recovered the residual feed to calculate the average daily feed intake, average daily gain and feed-meat ratio. It was collected blood and slaughtered to remove of the liver (without the gallbladder), thymus, spleen, bursa of fabricius at the end of the trial.Results of production showed that the average daily gain of the trial groups was higher, and the feed-meat ratio was lower. The trial result for ducklings to achieve the best growth performance was dietary supplementation of52.0mg/kg zinc.Results of antioxidant index showed that activity of the T-AOC of serum and liver, the CuZn-SOD of serum and the GSH-Px of liver increased first and then decreased as increasing of zinc. The content of MDA was the opposite. It showed adding the appropriate level of zinc improved the antioxidant function, thus contributing to the growth and development of the body. In this trial, the curve fitting results showed that adding52.9mg/kg of zinc in the corn-soybean meal of egg ducklings met the needs of the antioxidant capacity. This study found that supplementing with zinc in the diets significantly improved laying ducklings total protein and albumin concentration of serum and profit protein metabolism. The trend of serum urea nitrogen with the increase of dietary zinc levels was declining. This showed that dietary zinc had a beneficial effect on protein metabolism.The results of activity of main enzyme in serum also confirmed that the activity of serum ALP and LDH increased along with increasing of feed zinc levels. Adding51.8mg/kg zinc met the needs of ALP and LDH.The results of serum hormone indicators showed that the levels of T3, T4of the group fed60mg/kg were higher. Low zinc had a certain effect for T4, but the influence to T3was not large. The content of GH was highest when adding40.6mg/kg. Cortisol concentrations were lower when it added different levels of zinc in the diet of ducklings. But there was a rising trend in the higher level of zinc. Too high or too low level of zinc didn’t make body reaction achieve the best.The results of immune indicators showed that diet supplemented with zinc significantly increased the serum immunoglobulin concentrations. This study showed that zinc dosage of48.2mg/kg was better. Adding53.0mg/kg zinc to the basal diet (Zn33.3mg/kg) significantly improved the immune organs (thymus, spleen, bursa of Fabricius) index. The results of curve fitting showed that the concentration of IL-2was higher when it added57.9mg/kg zinc in the diet of ducklings.Integrating the results of production performance, the antioxidant function, hormone metabolism and immune function over the same period, it showed that adding zinc in the diet of ducklings was necessary, and the best level of zinc adding in the diet of ducklings(1～28days) was... |
PDF Full Text Request