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 and liver of turkeys were determined during incubation and early postnatal 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) decreased 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 Experiment 2, embryos were collected daily from Day 22 through 2 d posthatch. Embryonic weight increased from 32.5 g at Day 22 to 55.8 g at hatch (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 differences (Experiment 1, 2.52 g; Experiment 2, 0.63 g), concomitant with increased hatch weight in Experiment 2. Liver DM percentage and ether extractable lipid increased as incubation proceeded. Oleic acid comprised the largest proportion of total yolk fatty acids and of liver fatty acids. There was a small but significant increase in yolk sac oleic acid (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% to 56.5%). The absolute amount of all yolk sac fatty acids declined greatly during the second half of incubation through 6 d posthatch.