683. Factors influencing the vitamin content of milk fat: VI. The effect of reduced carotene intake

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Abstract
1. The results of an investigation into the efficiency of utilization by dairy cows of carotene from New Zealand summer pasture and from arachis oil are reported.2. A 50-fold decrease in the intake of carotene from pasture over a short period was shown to have only a small effect on the vitamin A potency of milk fat, carotene content being reduced by approximately 2μg./g. fat and vitamin A ester by approximately 1·5μg./g. fat. No change was observed in vitamin A alcohol content.3. Sample-to-sample variations in both the control and treated animals were observed in many cases to exceed the differences due to treatment except during the period of extreme carotene deprivation. Sample-to-sample variations of control and treated animals were also observed to be highly correlated, and it is suggested that variations in the external environment of the animal may have a marked effect on carotene utilization.4. Carotene in arachis oil was shown to be relatively more effective in maintaining the vitamin A potency of milk fat than summer pasture.The results of this investigation form a section of a thesis submitted by one of us (N.A.W.) in partial fulfilment of the requirements for the degree of Ph.D. of the University of New Zealand. The authors are indebted to the Department of Scientific and Industrial Research for a grant towards the investigation, and to Mr D. J. Dobson and the farm staff of The Dairy Research Institute (N.Z.) for assistance with the feeding and dosing of the animals and the collection of milk samples. The technical assistance of Miss Fay Frecklington is also thankfully acknowledged.