Evaluating Availability Of Phosphorus In Feedstuffs Of Plant Origin For Pekin Ducks

Three experiments were executed to evaluate true availability of phosphorus in 6 kinds of feedstuffs of plant origin for Pekin ducks based on determining endogenous loss of phosphorus and researching the additivity of available phosphorus in feedstuffs of plant origin for Pekin ducks.Experiment 1,this experiment determined the endogenous loss of phosphorus in Pekin ducks with P-free technique, regression technique and difference technique. One hundred and fifty Pekin ducks aged 21 days with similar body weight were randomly assigned into 5 treatments, with 6 replicates each treatment. P-free pure diet was formulated with P-free feedstuffs. Four cornstarch-based diets containing four levels of phosphorus (0.20%, 0.35%, 0.51% or 0.55%) were formulated with soybean meal, which was only source of phosphorus. TiO2 was added to diets as exogenous marker. On 22-day-old, all ducks were pre-fed with complete pellet feed for 3 days. During 25 to 30 day-old, ducks were fed with experiment diets separately, and excreta were collected by replicate in the period of 28 to 30 day-old. All samples were air-dried, and total P and TiO2 content were evaluated. Endogenous loss of phosphorus was calculated. The results showed that the endogenous loss of phosphorus in Pekin Ducks were 1.20g/kg DMI, 0.37 g/kg DMI and 0.29 g/kg DMI separately when determined by P-free technique, Regression technique and Difference technique. The value measured by P-free technique was highest among three techniques.Experiment 2,this study was executed to research the additivity and available P in feedstuffs of plant origin for Pekin ducks with emptying-force-feeding method. 84 21-day-old Pekin Ducks with similar weight and excreta-collecting apparatus were randomly assigned into 7 treatments, with 6 replicates each treatment. The ducks under trial were starved for 72h. After fasting period, the ducks from different treatments were fed by gavage with 70 g corn, soybean meal, cottonseed meal, rapeseed meal or their equal proportion mixtures, which included corn-soybean, corn-soybean-cottonseed, and corn-soybean-cottonseed. Excreta were collected separately for 48h and bioavailability of P was evaluated. The results showed that for mixed diets corn-soybean-cottonseed, there was significant difference between analyzed and calculated values for the apparent P availability, true P availability, apparent available P and true available P (P<0.05), while there was no significant difference (P>0.05) between the other two mixed diets. It is concluded that: 1) the additivity of true available P was better than apparent P for different feedstuffs of plant origin; 2) the additivity of apparent available P and true available P was variable for different combination of feedstuffs.Experiment 3,this experiment evaluated true availability of phosphorus and available phosphorus in 6 kinds of feedstuffs of plant origin for Pekin ducks. Three hundred and thirty-six Pekin Ducks aged 21 days with similar weight were randomly assigned into 7 treatments, with 6 replicates each treatment. The basal diet contained low level of phosphorus. The 6 experimental diets were formulated by mixing corn, soybean meal, rapeseed meal, cottonseed meal, peanut meal or wheat bran with basal diet at the ratio of 75:25,60:40,45:55,45:55,60:40 or 55:45, respectively. 0.4% TiO2 was added to diets as exogenous marker. On 22-day-old, ducks were pre-fed with complete pellet feed for 3 days. During 25 to 30 day-old, ducks were fed with experiment diets separately, and excreta were collected by replicate in the period of 28 to 30 day-old. All samples were air-dried, and total P and TiO2 content were evaluated. Bioavailability of phosphorus was calculated. The results showed that the true P availability in corn, soybean meal, rapeseed meal, cottonseed meal, peanut meal and wheat bran were 65.98%, 45.10%, 40.44%, 20.32%, 46.93% and 38.59%, respectively. The true available phosphorus were 1.74, 2.83, 4.27, 2.45, 3.35 and 2.84 g/kg DM, respectively.