Diet composition, environmental temperature, and exogenous estradiol effects on hepatic lipid deposition in growing chicks.

The interrelationships among dietary composition, environmental temperature, and level of estradiol (E2) administration on hepatic lipid deposition in chicks were studied. Two levels of E2 were injected at three intervals over a 4-day period, in 3-week-old male Leghorn chicks fed either a corn-soybean meal (CS) diet or a diet containing fish meal (FM) after 2 days fasting. The chicks were subjected to temperature ranges of 15 to 24 C (low) or 24 to 35 C (high) at 2 weeks of age. The E2 (in silastic tubes) was also implanted subcutaneously in 3-week-old broiler chicks fed either the CS diet or a diet containing fish meal, alfalfa meal, and torula yeast (FAY) from day of age to 6 weeks. They were subjected to the high and low temperature ranges at 3 weeks. Liver lipid deposition markedly increased with E2 administration among chicks fed all diets within both temperature ranges. Liver lipid was significantly greater at 24 to 35 C than at 15 to 24 C among estrogenized chicks. Feeding the FM or the FAY diet decreased hepatic lipid accumulation as compared to feeding the CS diet, but the ameliorative effect of the FM diet on hepatic lipid deposition was not observed at the low temperature or at the lower level of implantation. It was concluded that a range for estrogen administration exists wherein dietary effects are expressed. These data indicate that environmental temperature, dietary composition, estrogen level, and their interactions influence hepatic lipid deposition and also suggest that high temperature augments liver response to estrogen.