Effect of protein and amino acid status on lipogenesis by turkey poults

Feeding trials were conducted with large White turkey poults to determine the role of dietary protein, sulfur amino acid (SAA), and lysine levels on growth and in vitro lipogenesis by turkey poults. A basal, 23% protein diet was formulated to contain 75% of the National Research Council (NRC) requirement for both SAA (8.0 g/kg) and lysine (12.9 g/kg). Lysine hydrochloride and L-methionine were added to the basal diet. A 30% protein diet was formulated to contain 100% of the requirement for SAA and lysine and served as the dietary control treatment. Twenty-three percent protein diets supplemented to contain the required levels of SAA (10.5 g/kg) and lysine (17.0 g/kg) supported growth and feed consumption equal to that attached with the control diet. Glutamic-aspartic amino transferase (GAT) and isocitrate dehydrogenase (ICD) activities were decreased (P less than 0.5) by 23% protein compared to 30% protein. Lysine additions to the 100% SAA diets increased GAT activity; however, additional lysine had little effect upon ICD activity. Each increment of lysine, whether fed to conjunction with 75 or 100% SAA, increased malic enzyme (ME) activity. It is suggested from the study that both GAT and ICD reflect the protein nutritional status of the poult and ME its lipogenic capacity. Lysine added to 23% protein diets increased (P less than .05) in vitro lipogenesis; however, this effect could be moderated by increasing the SAA level from 75 to 100% of the requirement. Liver slices preferentially used lactate over alanine as a lipid precursor; however, both lactate and alanine stimulated acetate incorporation into lipid equally. Liver slices did not use glucose for lipid synthesis to the degree that they used alanine, lactate, or acetate.