George K. Davis

Reproduction and Lactation in Rats Fed Excessive Iodine

In a series of experiments adult female rats were fed zero to 2500 ppm supplemental iodine from zero to approximately 35 days prepartum. Females were permitted to litter normally and the survival of the young was observed. Other females were killed either between 17 and 19 days of pregnancy or between 24 and 48 hours postpartum to observe ovulation rate, implantation rate, development of normal fetuses and histology of mammary tissue. Increasing mortality of young after birth occurred with increasing levels of iodine. Most young failed to survive for 24 hours and those that survived 48 to 72 hours postpartum usually survived until weaning. Those failing to survive had essentially no milk present in the stomach. Visual observation and histological examination of mammary tissue from females fed iodine revealed that secretion was absent or markedly diminished. The role of iodine in thyroid function and the manifestations of iodine deficiency in various species have been well estab lished and have been reviewed by Riggs (1) and Berson (2). The effect of exces sive iodine, however, is less clearly defined. Morrison (3) reported that excessive in take of iodine is injurious to animals but did not describe the effects, indicate the levels of iodine required, or cite the ex perimental evidence. Malan et al. (4, 5) reported that 200 mg KI daily had detri mental effects on reproduction in sheep; however, the authors stated that the condi tions under which reproductive failure occurred involved not only high levels of iodine but déficiencesof both phosphorus and vitamin A. Other effects of excessive iodine on reproduction have not been re ported, although reproductive abnormali ties have been attributed to iodine defi ciencies (6, 7). The present studies were conducted to determine the effects of various levels of dietary iodine upon reproduction and lacta tion of rats.

COMPETITION AMONG MINERAL ELEMENTS RELATING TO ABSORPTION BY ANIMALS

The relationship of the different components of the diet to the digestion, absorption, and utilization of individual nutrients has always been an intriguing object of research. A literature review has shown that a major factor in the environment that influences the absorption of mineral elements from the intestinal tract of the individual animal or human is the chemical form in which the element is combined when it enters the digestive tract, or which forms in the tract itself. Experiments have demonstrated that excessive levels of various trace elements such as copper, zinc, and molybdenum have an adverse effect upon the utilization of one another and other members of the trace element family that are required for proper nutrition. High levels of calcium, phosphorus and magnesium may also affect the requirement level. Evidence regarding the mechanism of such interactions, and competition among the elements that may influence absorption and utilization is presented.

Gamma Irradiation and Interrelation of Dietary Vitamin A and Copper on their Deposition in the Liver of Swine

A study was made to determine whether dietary vitamin A had an effect on the level of deposition of Cu in liver; whether dietary Cu had an effect on the deposition of vitamin A in the liver; and whether whole-body gamma irradiation had any effect on the deposition of vitamin A and Cu in the liver of swine. Vitamin A unsupplemented pigs had only 2 to 3 N of vitamin A/g fresh weight of liver. High vitamin A values (116 to 122 IU/g) in the liver of supplemented pigs demonstrated the remarkable capacity of the liver to store vitamin A when it is present in the diet. Whole-body Co/sup 60/ irradiation with 630 r had no significant effect on the deposition of vitamin A in these tissues. Swine that received no supplemental vitamin A had a greater concentration of Cu in liver, and irradiation resulted in a greater deposition of Cu in the liver. However, dietary vitamin A and irradiation did not affect deposition of Cu in heart and gracilis muscle. Cu supplementation increased the level of vitamin A in liver, possibly on account of the effect of CuSO/sub 4/ in eradicating intestinal parasites. (TCO)

Nutrition: Joint Responsibility of Agriculture and Medicine

The need for good nutrition is given “lip service” by almost every lay or professional person but the ultimate responsibihty for adequate nutrition and its role in maintaining human health can be said to rest squarely on the sister disciplines of agriculture and medicine.