THE CONCENTRATION OF DIFFERENT LIPID CLASSES DURING LATE EMBRYONIC-DEVELOPMENT IN A RANDOM-BRED TURKEY POPULATION AND A SUBLINE SELECTED FOR INCREASED BODY-WEIGHT AT 16 WEEKS OF AGE

Lipid changes in the yolk sac of the embryo were studied in a randombr ed population of turkeys (RBC2) and a subline of the RBC2 selected for increased BW at 16 wk (F line). Comparisons of yolk sac and embryonic development were made between 22 d of incubation and hatch (28 d). Po ults from the F line had heavier yolk sacs from 24 to 28 d and yolk fr ee body weight was also heavier at hatch (61.1 vs 52.8 g). Yolk sac li pid (percentage of DM) declined faster in F line embryos (69 to 39%) c ompareds with the RBC2 line (62 to 48%). In both lines, embryonic live r dry matter and lipids (Percentage of DM) were similar. Yolk sac neut ral lipids increased from 22 to 28 d (70 to 80% total lipid) in both l ines and there was a concomitant decline in phospholipids (30 to 20%). The direction of the changes was similar for embryonic liver lipid. A t 26 and 28 d, there were significantly increased neutral lipids (94 v s 88%) and decreased phospholipids (6 vs 12%) in RBC2 compared with F line embryonic livers. The concentration of cholesterol esters (percen tage of total lipid) increased in the yolk sac and embryonic liver dur ing the course of incubation. At 26 and 28 d, livers from RBC2 embryos had increased cholesterol ester concentration compared with livers fr om the F line. These results suggest that selection for body weight at 16 wk of age has not changed total lipid content of the yolk, but the re was a significant decline in the proportion of triacylglycerol (per centage of total lipid) and diacylglycerol (percentage of total lipid) in the F line during embryonic development. Selection also resulted i n significantly increased hepatic total lipid in F line embryos but si gnificantly decreased the proportion of hepatic neutral lipid.