Dependences of apparent digestibility of crude protein and nitrogen excretions on levels of protein intake in gorwing pig
2009
Ho Trung Thong
Dilution method was used to formulate 6 diets (N1, N2, N3, N4, N5, N6) differing in crude protein contents (from 4.58% in N1 to 30.02% in N6 as DM-basis) but identical protein quality. A total of 24 growing pigs (Piétrain x (Duroc x Landrace)) with average initial BW of 43.67 kg were randomly allotted into metabolism cages. The experiment was carried out according to standards of a nitrogen balance experiment. Results from this study showed that apparent digestibility of crude protein increased from diet N1 (76.8%) to diet N6 (90.0%). The changes of apparent digestibility of crude protein in dependence on the increasing of protein contents in the diets from this study was in agreement with result of Sève (2000) in a study on effect of amino acid intake on apparent digestibility of amino acids. When protein content of a feedstuff decreases, the relative importance of the basal endogenous loss of nitrogen in total nitrogen excretion in faeces increases, as a consequence the apparent digestibility decreases. Thus, the concept of "standardized digestibility" or "true digestibility" should be used because these calculations are not affected by protein or amino acid intake/content in diets. Total nitrogen excretion in urine and in faeces increased with the increment of protein intake; however, it can be concluded that main part of the increment of nitrogen excretion comes from urine. Relations between nitrogen intake and nitrogen excretion in urine and in faeces follow the quadratic equations y = ax2 _ bx + c (R2 = 0.98) and y = ax2 + bx + c (R2 = 0.86), respectively.
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