Effects of Blood Sampling Times and Dietary Protein Levels on Hematocrit Value and Volume of Plasma Protein Fraction in Broilers

The concentration of plasma amino acid is a useful criterion for determination of amino acid requirement in animals. However, volume of protein-free plasma may be influenced by dietary protein level and blood sampling time, since it is known that blood contents of corpuscles and protein are influenced by these factors suggesting a possibility that free amino acid concentration in blood is also influenced. The purpose of the present study was to clarify whether these two factors affect hematocrit value and plasma protein content in order to express exact concentration of blood free amino acid. Female broilers were fed 3 experimental diets with 3, 200 kcal ME/kg and 15.51, 16.89 and 18.26% of crude protein from 17 to 27 days. Blood samples were taken at 5, 8, 12, 16 and 20:00 from 4 chicks per dietary group each. As soon as possible, the hematocrit value was determined. Then, plasma was separated by centrifuging and was added the same amount of sulfosalicylic acid solution. After mixing well, the volume of precipitated plasma protein fraction was determined in the same way as in the hematocrit value. The hematocrit value was not affected by blood sampling times and dietary protein levels and remained within the range of 29.4 to 31.3. Though the volume of plasma protein fraction ranged 6.2 to 7.0%, the value and variation were smaller compared to the supernatant fraction. From these data, it is suggested that the effects of the hematocrit value and the volume of plasma protein fraction can be neglected to evaluate the changes in the concentration of plasma amino acid in broilers.