Metabolism and Ovarian Follicular Uptake of the Major Yolk Precursor in Laying Turkey Hens'

ABSTRACT The total turnover of the major yolk precursor lipoprotein (very-low-density lipo-protein from laying hens; VLDL-L) was determined in laying turkey hens (n = 21) of a single strain selected for increased egg production (egg strain). Separate calculations were made for the two major lipid fractions, the triglycerides (TG) and phospholipids (PL). No difference was found between the fractional clearance rates of VLDL-L TG and VLDL-L PL (-.00248 min"1 vs.-.00245 miri"1, respectively). The concentration of VLDL-L TG was greater than that of VLDL-L PL (14.03 mg-mf vs. 5.60 mg-mf) and accounted for the difference in total turnover between VLDL-L TG and VLDL-L PL (12.12 g. d"1 vs. 4.77 g-d"1). Multiple regressions, with total turnover of either VLDL-L TG or VLDL-L PL as the dependent variable and fractional turnover rate (k) of VLDL-L TG or PL, concentration (C) of VLDL-L TG or PL, the distribution volume (V) of VLDL-L (not measured independently for TG and PL), and body weight (B wt) were calculated. For VLDL-L TG as the dependent variable, significant con-tributions to R2 were made by C, V, and k with O V> k. For VLDL-L PL, significant contribu-tions were made by these variables with O k> V. The percentage uptake of VLDL-L radioactivity by developing ovarian follicles was 30.3 % (n = 17). When percentage uptake was the dependent variable, multiple regression analysis did not explain the variance in the data utilizing either the VLDL-L TG or VLDL-L PL data sets. Thus, follicular uptake was not associated with plasma concentration, fractional clearance rate, distribution volume, or body weight in this strain of turkey hens