Carotene Supplementation Research Articles

Carotene in the Ration of Dairy Cattle. I. The Influence of Long Periods of Suboptimal Carotene Intake on the Carotene and Vitamin A Values of the Blood, Liver, and Milk Fat of Dairy Cows1,2

Summary Blood plasma, liver, and milk fat analyses for carotene and vitamin A in Jersey and Holstein cows on normal and suboptimal carotene rations were compared. Suboptimal carotene rations fed prenatally and over long periods of time after birth resulted in low liver vitamin A and carotene values, which failed to respond to carotene supplementation as high as 330 γ per kilogram of body weight. Repeated injections every 5 days of either 250,000 or 1,250,000 I.U. of vitamin A ester failed to result in any appreciable increase of liver vitamin A or carotene in cows on a suboptimal carotene ration.

The Utilization of Carotene by Hypothyroid Rats

The conversion of carotene to vitamin A and the distribution of vitamin A was studied in young growing or mature rats made hypothyroid with thiouracil. On administration of small doses of carotene a relatively greater amount of vitamin A was recovered from the livers of the hypothyroid rats than from the normal controls. The difference disappeared with a 20-fold increase in dose. A decrease in the utilization rate of vitamin A for metabolic functions by hypothyroid rats was demonstrated when hypothyroid and normal rats were depleted of similar preexisting stores since larger amounts were found in the deficient animals than in the controls. Growth retardation through caloric restriction in normal rats likewise resulted in larger residual vitamin A stores in quantities comparable with those found in hypothyroid rats. The removal rate of a given dose of carotene in oil from the gastrointestinal tract was similar in normal and hypothyroid rats. This indicates a similarity of absorption rates in the two groups for the dose employed. Normal male rats were capable of accumulating measurable amounts of vitamin A in their kidneys following carotene supplementation. Female rats whether normal or thyroid-deficient had only insignificant accumulation of vitamin A in their kidneys. Hypothyroidism and growth retardation due to caloric restriction were factors causing the disappearance of these vitamin A deposits in the male rat. It is concluded that body weight and growth rather than basal metabolic rate govern the utilization of vitamin A and that neither absorption, transformation nor utilization of carotene is affected directly by thyroid activity.

469. The effect of tocopherol and carotene supplements on the vitamin A potency of New Zealand butterfat

1. Reasons for the seasonal variations in the vitamin A potency of New Zealand butterfat have been investigated. Adequate carotene for the production of butterfat of maximum potency has been shown to be present in New Zealand pasture throughout the year, but during the summer period this carotene is relatively non-available to dairy cows.2. In experiments with monozygotic twins grazing average summer pasture it has been shown that a supplement of 1 g. of tocopherol per day increased both carotene and vitamin A levels in the milk fat, the total vitamin A potency being raised from a typical midsummer minimum of 34 i.u./g. fat to a value approaching the maximum late winterspring level of about 50 i.u./g. This maximum level was unaffected by increasing the tocopherol supplement to 3 g. per day or by supplying 300 mg. of carotene in a readily available form in addition to the 3 g. tocopherol.3. Supplementing the summer pasture with 300 mg. of carotene in oil without tocopherol was without effect on the potency of the fat, supporting the conclusion that the carotene intake was already adequate.4. A significant correlation was found to exist between vitamin A potency and tocopherol content of New Zealand butterfat.5. It is suggested that the low vitamin A potencies may be associated with the high percentage of clover in the summer pastures.

Seasonal changes in spermatogenesis in rams : Their relation to plane of nutrition and to vitamin A status

Observations have been made on the seminal characters, body weights, and plasma vitamin A status of rams fed on carotene-deficient diets, at higher and lower levels of food intake. Carotene supplements were provided for a number of the rams at each level of dietary intake. The seminal characters exhibited a seasonal variation, characterized by a reduction in the total number and longevity of spermatozoa during the summer months. Within this period, a temporary increase in the number of morphologically abnormal spermatozoa occurred in the rams of low plasma vitamin A status, or on the lower plane of nutrition. Plasma vitamin A levels fell more rapidly in the rams on the higher plane of nutrition than in those on the lower plane. Morphological abnormality of spermatozoa attributed to vitamin A deficiency appeared at an earlier date in the high-plane group except when rams with presumably low liver stores of vitamin A were fed on the deficient diets. Vitamin A deficiency, if sufficiently severe, resulted in the appearance of a high percentage of morphologically abnormal spermatozoa in the semen of rams on both planes of nutrition. The addition of pure carotene to the diet prevented or reduced this degree of abnormality.