Factors Affecting the Stability of the Vitamin A from Cod Liver Oil in Cereal Feeds

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Abstract
The vitamin A in a mixed ration and ground white corn samples containing added cod liver oil was not stabilized by storage in sealed containers (gas-tight) at different moisture levels. The removal of enclosed oxygen by respiration of the feed samples at higher moisture levels (10 to 15%) showed no demonstrable effect upon vitamin A preservation. Compar-able vitamin A losses occurred in sealed and unsealed samples under similar storage conditions. Vitamin A losses in both sealed and unsealed samples increased with temperature and length of storage. Significant amounts of the added vitamin A in the mixed ration and white corn samples (without added trace minerals) were retained after several months' storage. Approximately 60% of the initial vitamin A content of the mixed ration was still present in samples stored in sealed and unsealed containers for 2.5 to 3 months at 33 to 36°C. The vitamin A of cod liver oil was more stable in ground white corn than in the mixed ration, under sealed and unsealed conditions and at similar storage temperatures. The extremely rapid destruction of vitamin A induced by adding trace minerals (Fe, Cu, Co and Mn) to an unsealed white corn sample containing added cod liver oil was largely prevented by adding the minerals in a dried gelatin-mineral mixture rather than in free form. The experiments did not determine whether the free trace minerals are capable of accelerating vitamin A destruction in feeds stored in an atmosphere free of oxygen. The effective prevention of rancidity and vitamin A destruction in practical poultry rations and certain livestock feeds which commonly contain small amounts of added (free) trace minerals is an important problem. The present study indicates that a practical solution of the problem depends upon the addition of the trace minerals in a form which limits their ability to come in contact and react with other constituents of the ration.