CHARACTERIZATION OF CHANGES IN YOLK-SAC AND LIVER LIPIDS DURING EMBRYONIC AND EARLY POSTHATCH DEVELOPMENT OF TURKEY POULTS

In two studies, changes in lipids and fatty acids from the yolk sac an d liver of turkeys were determined during incubation and early postnat al growth. In Experiment 1, embryos were collected from Day 13 through 6 d posthatch. Embryos weighed 4.25 g at Day 13, 52.8 g at hatch (Day 28), and 104 g at 6 d. Total yolk lipid (grams per yolk sac) decrease d from 9.48 g at Day 13 to 2.52 g at hatch (Day 28). Almost half (47%) of the yolk lipid decreased during the last week of incubation. In Ex periment 2, embryos were collected daily from Day 22 through 2 d posth atch. Embryonic weight increased from 32.5 g at Day 22 to 55.8 g at ha tch (Day 28), 3 g more than in Experiment 1. On Days 22 and 25, total yolk lipid (grams per yolk sac) was slightly less in Experiment 2 than in Experiment 1, but at hatch (Day 28) there were considerable differ ences (Experiment 1, 2.52 g; Experiment 2, 0.63 g), concomitant with i ncreased hatch weight in Experiment 2. Liver DM percentage and ether e xtractable lipid increased as incubation proceeded. Oleic acid compris ed the largest proportion of total yolk fatty acids and of liver fatty acids. There was a small but significant increase in yolk sac oleic a cid (percentage of total fatty acids) between Day 22 (40%) and hatch ( Day 28; 45.4%) and a much larger increase in liver oleic acid (46.6% t o 56.5%). The absolute amount of all yolk sac fatty acids declined gre atly during the second half of incubation through 6 d posthatch.