Effects Of Dietary Protein And Threonine On Growth Performance And Carcase Traits Of Pekin Ducks

Threonine (Thr) is an essential amino acid for animal growth and development, which is now considered as the second or third limiting amino acid and plays an important role in animal growth. To determine whether by reducing dietary protein in the diets, nitrogen excretions can be reduced in litter, we added graded levels of Thr to the diets and studied the effect of interaction between dietary protein and threonine on the growth performance and carcass traits in Pekin ducks. For this purpose,we studied the effect of dietary protein level on Thr requirement of Pekin ducks from hatching to 21 days of age. We also studied threonine requirement of Pekin ducks from 15 to 35 days of age.This study included two experiments. Expeiment lwas conducted to investigate the effects of dietary threonine (Thr) and crude protein on the growth performance and carcase traits of starter Pekin ducks, and experiment 2 was conducted in order to evaluate the Thr requirements of Pekin ducks.Exp 1. Effects of Dietary Threonine and Crude Protein on growth performance and carcase traits of 21 D old Pekin ducks.The aim of this study was to investigate the effects of dietary threonine (Thr) and crude protein (CP) in wheat-peanut meal based diets on the growth performance, carcase traits of Pekin ducks from 1 to 21 d of age. A 2×6 factorial experiment, using 2 protein (16.99%,20.1%) and 6 total dietary threonine levels(0.43%,0.49%,0.55%,0.61%,0.67%,0.73%) was conducted to study the effects of dietary threonine and protein on growth performance and carcase traits of Pekin ducks from 1 to 21 days of age.Five hundred and seventy six 1-day-old white Pekin male ducklings were randomly allocated to 72 pens with 8 birds per pen according to similar pen weight. There were 12 dietary treatments,consisting of 6 replicate pens. Weight gain, feed intake and feed’gain of ducks from each pen were measured every week. At 21 days of age, two ducks were selected randomly from each pen and slaughtered to evaluate the carcass quality. A significant interaction between dietary CP and Thr was found for feed intake, body weight (BW) gain and FCR. Increasing Thr supplementation improved feed intake, BW gain and FCR in both high and low CP diets. Incremental increases in dietary Thr increased breast yield at both CP levels and abdominal fat only significantly increased by Thr supplementation. Legmeat yield was not affected.Thr and CP had a significant interaction in their effects on the growth performance of Pekin ducks. Estimated Thr requirements increased as dietary CP increased.According to the Broken-line regression in the low CP diet the Thr requirementis 0.54%for feed intake and weight gainand 0.50% for breast meat. While in the high CP dietthe Thr requirement is 0.61% forthe weight gain and breast meat and 0.62% for the feed intake.Exp 2 Effects of Dietary Threonine on Growth Performance and Carcase traits in 15-35-D-Old Pekin DucksIn Experiment no.2, six threonine levels(0.48%,0.54%,0.60%,0.61%,0.66%,0.72% and 0.78%) were used to study the effects of dietary threonine on growth performance and carcase traits of Pekin ducks from 15 to 35 days of age.Three hundred and sixty 15-day-old white Pekin male ducks were randomly allocated to 72 pens with 5 birds per pen according to similar pen weight. There were 6 dietary treatments, each of which consisted of 12 replicate pens. Weight gain, feed intake and feed/gainof ducks from each pen were measured. At 35 days of age,twoducks were selected randomly from each pen and slaughtered to evaluate the carcass quality. Thr supplements significantly affected thefeed intake, body weight (BW) gain, and FCR (P< 0.05).Increasing Thr supplementation improved feed intake, BW gain and FCR (P< 0.05). Incremental increases in dietary Thr increased breast yield at high Thr levels. Abdominal fat and legmeat yield were not affected.According to the broken-line regression analysis, the thr requirement was 0.54%for weight gainandfeed intake and 0.58%for breast meat.