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 randombred 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). Poults from the F line had heavier yolk sacs from 24 to 28 d and yolk free body weight was also heavier at hatch (61.1 vs 52.8 g). Yolk sac lipid (percentage of DM) declined faster in F line embryos (69 to 39%) compareds with the RBC2 line (62 to 48%). In both lines, embryonic liver dry matter and lipids (Percentage of DM) were similar. Yolk sac neutral lipids increased from 22 to 28 d (70 to 80% total lipid) in both lines and there was a concomitant decline in phospholipids (30 to 20%). The direction of the changes was similar for embryonic liver lipid. At 26 and 28 d, there were significantly increased neutral lipids (94 vs 88%) and decreased phospholipids (6 vs 12%) in RBC2 compared with F line embryonic livers. The concentration of cholesterol esters (percentage of total lipid) increased in the yolk sac and embryonic liver during the course of incubation. At 26 and 28 d, livers from RBC2 embryos had increased cholesterol ester concentration compared with livers from 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 there was a significant decline in the proportion of triacylglycerol (percentage of total lipid) and diacylglycerol (percentage of total lipid) in the F line during embryonic development. Selection also resulted in significantly increased hepatic total lipid in F line embryos but significantly decreased the proportion of hepatic neutral lipid.