Lipid Accumulation and Cell Multiplication in Adipose Bodies in White Leghorn and Broiler-Type Chicks

Abstract

Reduction of nutrient intake from hatching until six weeks of age by dietary dilution decreased growth rate and lipid accumulation in the retroperitoneal adipose depot. In White Leghorn chicks fed the undiluted diet adipocyte size remained relatively constant during the six-week period and was approximately half that in broiler-type chicks. With the diluted diets, adipocytes decreased in size to a minimum at 4–5 weeks of age and then increased. The breed difference in adipocyte size was generally maintained with restricted nutrient intake.The response of adipose tissue to withholding feed for up to five days after hatching was studied. At hatching the lateral thoracic body was a major fat depot and, in the 24-hour-old broiler and White Leghorn chicks, contained 215 and 177 mg. of lipid, respectively. In chicks not given feed the amounts of lipid declined to 14 and 13 mg. by the fifth day. White Leghorn chicks withstood the starvation period after hatching better than the broiler chicks and had 6% mortality as contrasted with 27% in the broilers. Four-week old chicks of both breeds had deposited less retroperitoneal lipid when feed had been withheld for five days after hatching.Broiler-type chicks fed ad libitum to 21 days of age showed an increase in the weight of the retroperitoneal adipose body which was due mainly to hyperplasia but with some increase in cell size. The lateral thoracic subcutaneous fat body showed no growth until approximately 12 days in birds fed ad libitum. In birds fasted for three-days after hatching, adipocytes in this site, which had lost lipid during the starvation period, were repleted after feeding. Cell multiplication in the retroperitoneal adipose body, as estimated by 3H-thymidine-uptake and dilution, was retarded immediately following fasting either post-hatching or at 10 days of age. The three-day old fasted chicks showed, nevertheless, considerable cell multiplication in this depot as soon as they were fed. In 13-day old chicks no appreciable cell multiplication occurred in the retroperitoneal depot immediately after refeeding and it was apparent that the increase in tissue weight following refeeding was due to refilling of existing adipocytes.