The interactive effects of threonine and crude protein level on apparent nutrients digestibility and nitrogen balance in local Muscovy ducks

This study aimed to determine the effects of threonine (Thr) and crude protein (CP) on the apparent nutrients, amino acid digestibility, and nitrogen balance of local Muscovy ducks at 8 and 10 weeks of age. The study was a 3x2 factorial design for two phases with three levels of CP (17, 18, and 19% CP) and two levels of Thr (0.7 and 0.8% Thr) for the first phase while three levels of CP (15, 16, and 17% CP) and two levels of Thr (0.5 and 0.6% Thr) for the second phase. The birds were fed and given water ad libitum for the entire experiment. The results showed that CP and Thr increased apparent nutrient digestibility, especially for DM digestibility (P < 0.05). Besides, Thr addition also increased OM, and NDF digestibility (P <0.05). In addition, nitrogen balance was better in high-dose Thr and CP diets (p<0.05). For amino acids, when increased Thr and CP levels, it increased the digestibility of Isoleucine, Threonine, and Valine (P < 0.05) while Thr levels increased Methionine, Phenylalanine, Serine, Tyrosine, and CP levels increased Isoleucine, Leucine, Lysine, Threonine, Valine, Alanine, Glutamic, Proline digestibility (P < 0.05). However, this study could not record any interactions between Thr and CP in the diet throughout the experiment (P > 0.05). It can be concluded that supplementation with 0.8% Thr and 19% CP for 5-8 weeks of age and 0.6% Thr and 17% CP for 8-10 weeks of age in the local Muscovy duck diet increased the digestibility of apparent nutrients and amino acids and balanced the nitrogen substance in the duck’s body.