The First Injection Of Isotope Detection Of Endogenous Amino Acids Losses Methodology

A new technique, the single intravenous injection of [3H] Leucine (SIIL), for determining the recovery of endogenous amino acid (AA) in the excreta of poultry was perfect. The new technique aims to minimize the unavoidable drawbacks of the traditional isotope dilution technique, the continuous intravenous injection of isotope labeled amino acids.The main principle of SIIL technique was that, reasoning from the theory of single compartment and origins of endogenous AA, the ratios between specific radioactivity (SR) of endogenous leucine in excreta (SRe) and SR of free leucine in plasma (SRp) kept constant, no matter what kinds of diets the birds eaten. The SRe of practical nitrogen-containing diet could be estimated from the SRe/SRp of nitrogen-free diet (NFD), and endogenous leucine loss of practical diet was calculated directly from the estimated SRe, and the endogenous losses of other amino acids could be obtained based on the endogenous AA pattern of NFD.The study was carried out in three steps for establishing the SIIL technique.The first step was to prove the synthesis that the birds in travenously injected with the same dosage of [3H]Leucine, the ratio of SR in endogenous leucine and plasma free leucine to SR in endogenous leucine and excreta leucine remained constant. Twenty four young hens(1.5kg of body weight, WB) were randomly divided in to 4 groups. Every sixth group was force-fed a nitrogen-free diet or the diet with 20% crude protein (cp) content in which soybean meal or cottonseed meal was the sole nitrogen source (30g DM/kg BW) or diet free.The second step was to calculate the amount of all AA the birds fed practical nitrogen-containing diets excreted. The amount was estimated on the basis of the first step's result and the endogenous AA pattern of NFD.The last step was to estimate the optional time of taking blood samples by differential and nutrition theory.The main results of the study were as follows:1. The SIIL technique suggested here was theoretically valid for measuring endogenous AA losses in nitrogen-containing diets. According to statistics, AA in the excreta from 0 to 48hr, between FAS and NFD should be all endogenous; The ratio of SR in endogenous leucine and plasma free leucine to SR in endogenous leucine and excreta leucine was 0.064±0.0012 or 0.068±0.0008, respectively, which was no significant difference (p>0.05), and proved the right SRe/SRp=K.2. SIIL could estimate the endogenous of leucine and other AAS when birds were force-fed practical nitrogen-containing diets. The total endogenous AA in the excreta of the two diet with 20%crude protein is 52.07% or 34.21% more than NFD's ,respectively. The amount of the two treatments was 25081.94 mg/kg DMI and 22136.00 mg/kg DMI, respectively. There was no significant difference (p>0.05). This proved that the excreta amount of endogenous AA was constant within the definite level of CP.3.The optional time of taking blood samples was 35 hours after intravenously injected [3H]leucine.