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A total of 32 male piglets Large White x Landrace were weaned at 18 days of age and individually kept in metabolism crates. Piglets were distributed into four experimental treatments according to the initial body weight. Four experimental diets based on maize and soybean meal were prepared, but no synthetic amino acids were added to the control diet containing 23.1%CP. Therefore three low protein diets containing 21.2, 18.9 and 17.2%CP were formulated by decreasing soybean meal content in substitution of maize, and supplementing with eight essential amino acids with the exception of arginine and leucine. Animals were weighted and feed intake weekly measured in order to calculate ADG, ADFI and FGR. Blood samples were also collected from each animal on days 0, 7 and 14 of experiment in order to determine serum urea nitrogen and serum free AA concentration. Severity of diarrhoea was monitored twice per day and quantified using a faecal consistency scoring. At the end of the experimental trial piglets were sacrified to study intestinal morphology and enzyme activity.
The reduction in dietary CP content did not affect ADFI but linearly decreased ADG and FGR during the whole experimental period. However, decreasing CP content in piglet diets linearly improved faecal consistency, and reduced serum urea nitrogen levels on 7 and 14 days post-weaning. On day 14, a reduction of arginine, glutamine and proline concentrations in serum was observed for piglets fed the 17.2% of CP diet than those animals fed the control diet. Additionally, villous height was also reduced in the duodenum and jejunum according to the reduction of dietary CP.
It is concluded that reducing dietary CP content from 23.1 to 18.9% with AA supplementation improve the utilization of dietary nitrogen of piglets diets without affecting intestinal morphology. Levels below 18.9% of CP may limit amino acid availability resulting in a reduction of feed intake, villous atrophy and low enzymatic activity.
LY Yue and SY Qiao. 2008 Livestock Science,115:144-152.
