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Swine Nutrition and Feed Technology
Asian-Australasian Journal of Animal Sciences 2001;14(9): 1282-1289.
DOI: https://doi.org/10.5713/ajas.2001.1282    Published online September 1, 2001.
The Effect of Lysine to Protein Ratio on Growth Performance and Efficiency of Nitrogen Utilization in Pigs
Defa Li, Pengbin Xi, Junxun Wang, Jitan Wang, Jiping Ren, Yufan Kang, P. Thacker
One feeding trial and two metabolic trials were conducted to investigate the effects of lysine to protein ratio in practical swine diets on growth performance and efficiency of nitrogen retention and utilization in different growing phases. In Trial one (the feeding trial), 90 mixed sex pigs weighing 9.1 1.4 kg (Duroc Landrance Beijing Black) were used to study the effects of concentrations of 5.2, 5.3, 5.8, 6.4 and 7.2 g lysine/100 g CP in diets containing 1.2% lysine on growth performance and serum urea nitrogen. The results showed that feed conversion efficiency and economic efficiency were best for pigs fed the diet containing the lysine concentration of 5.8 g /100 g crude protein. Serum urea nitrogen concentration decreased linearly (p=0.0009) and serum free lysine content increased linearly (p=0.0017) as the lysine to protein ratio in diets increased from 5.2 to 7.2 g/100 g. In Trials two and three (the metabolic trials), five growing barrows (Duroc Landrance Beijing black), with initial body weights of approximately 26 2.4 kg and 56.3 3.5 kg, respectively, were allotted to five dietary treatments according to a 5 5 Latin square design. Trial two contained 5.2, 5.7, 6.1, 6.7 and 6.8 g lysine/100 g CP treatments. Trial three contained 4.6, 5.0, 5.6, 6.1 and 6.6 g lysine/100 g CP treatments. The results showed that nitrogen retention in growing pigs decreased linearly (p=0.0011 in Trial two; p=0.0099 in Trial three) as the lysine to protein ratio in diets increased. The ratio of lysine to protein in diets resulting in maximum nitrogen retention was 5.2 g/100 g and 5.0 g/100 g in Trial two and Trial three, respectively. In Trial two, apparent biological value and gross nitrogen efficiency increased linearly (p=0.0135 and p=0.0192, respectively) as the lysine to protein ratio increased from 5.2 to 6.8 g lysine/100 g CP. In summary, we concluded that the optimal Lysine to Protein Ratios for 8-20 kg and 20-80 kg pigs were 5.8 g/100 g and 5.0 to 5.2 g/100 g, respectively.
Keywords: Lysine to Protein Ratio; Pig; Growth Performance; Nitrogen Retention; Nitrogen Digestibility

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