Abstract
ABSTRACTThis study was conducted to evaluate the effects of dietary crude protein (CP) level on faecal CP and amino acid (AA) flow and digestibility, faecal and ileal digesta microbial AA composition. Eighteen Duroc × Landrace × Yorkshire barrows (60 ± 1.43 kg) were randomly divided into 3 groups with 6 barrows in each, and fed a maize–soybean meal diet at the 10% (L-CP), 13% (M-CP) and 16% (H-CP) CP levels. The results indicated the faecal total N, CP, total AA (TAA) flow increased linearly (P < 0.05) whereas dietary CP concentration increased from 10% to 16%. The DM digestibility, CP digestibility, TAA digestibility, essential amino acid and non-essential amino acid digestibility decreased linearly (P < 0.05), whereas dietary CP concentration increased from 10% to 16%. Compared with pigs in M-CP and L-CP groups, pigs in the H-CP group had higher Asp, Cys, His, Arg flow in the faeces (P < 0.05). Compared with pigs in the L-CP group, pigs in M-CP and H-CP groups had less faecal Glu, Ala, Tyr, Pro, Val, Ile, Leu and flow (P < 0.05). Faecal microbial N and AA in the L-CP group was the highest in three groups. Pigs fed a corn–soybean meal-based diet reduced in protein concentration have lower faecal N flow.
Highlights
Amino acid (AA) plays a very important role in animal nutrition and physiology (Li et al 2009)
The microbial protein N flow of faeces in 30–60 kg growing pigs was different among the three treatments (P < 0.01), that is, the greatest in the HCP group and the lowest in the LCP group (P < 0.05)
This study demonstrated the effect of dietary N substrates on microbial AA composition in ileum was more significant than faeces
Summary
Amino acid (AA) plays a very important role in animal nutrition and physiology (Li et al 2009). Growing concerns about environmental pollution arising from intensive swine production had forced researchers to study protein and AA nutrition of the pig beyond their requirements for maximal growth and performance (NRC 2012). In the last 10 years, animal husbandry workers did their best to find effective ways to reduce excessive emissions of nitrogen in the pig production, such as the use of essential AA (EAA) with diet, the decrease in the level of dietary protein, the use of amino acid synthesis, the application of ‘ideal protein’, the implementation stage and the high digestibility of protein feed raw materials (Rotz 2004). Protein-bound AA absorption might be reduced in complete diets containing low protein concentrations and might contribute to impaired growth performance
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