The role of fat in the diet of rats

Earlier results (Aaes-Jargensen & Dam, 1954 b, c ; Aaes-Jargensen, 1954) have demonstrated a decrease in body-weight of rats with increasing amounts of hydrogenated fat in the diet.The experiment reported here was undertaken to investigate whether these results were solely due to an increase in the requirement of linoleic acid with the concomitant ingestion of fat as suggested by Burr (1942) and Deuel, Greenberg, Anisfeld & Melnick (I951), or whether isomers of unsaturated fatty acids formed during hydrogenation were partly responsible for accentuation of the fat-deficiency symptoms.EXPERIMENTAL Newly weaned male rats were distributed over fifteen groups of six animals each.T h e compositions of the diets, calculated on a percentage-by-weight basis, and the amounts of ethyl-linoleate supplement are shown in Table I.The ethyl linoleate was given orally three times a week.Vitamins A and D, were given as drops of an aqueous colloidal solution (Decamin aquosum, Ferrosan Ltd, Copenhagen), supplying I 20 i.u.vitamin A and 18 i.u.vitamin D,/animal/week.Food and water were given ad lib.The food consumption was estimated daily from the 10th to the 13th week of experiment.The daily calorie intake per sq.m. body surface and the efficiency of utilization of calories for growth during the same period were calculated.The animals were weighed and inspected weekly and were killed with chloroform at the end of the experimental period, which lasted 26 weeks.Autopsies were performed, and testes, kidneys, skin specimens, liver, and adrenals were examined histologically.Blocks of tissue were fixed in 10 yo commercial formalin (4% formaldehyde).Paraffin sections were stained routinely with haematoxylin and eosin.Part of the material from the kidneys was stained for connective tissue with van Gieson's stain, and material from all the livers was cut on a freezing microtome and stained for fat with Sudan black. RESULTS AND DISCUSSION Growth ratesI n Table z are listed the mean values for weights at the beginning and the end of the experiment, as well as daily gain in weight, calorie intake and efficiency of utilization of calories for growth from the 10th to the 13th week of the experiment.It will be seen that 7% trilaurin (group 200) or 7% hydrogenated arachis oil (group 209) gave *