Determining the bioavailability of Vitamin A acetate concentrates mixed in a vitamin-mineral premix after a 56-day temperature and humidity storage stress

The current study was conducted to determine the availability of Lutavit® A 1000 NXT (A-1000), a vitamin (Vit) A acetate product, after a 56-d incubation period. Four Vit A sources (A-1000, B, C, and D) were blended into Vit-trace mineral premix designed to put oxidation stress on the Vit A beadles. These Vit premixes along with a negative control (NC), without Vit A, were stored in two different conditions, Cold Stress (CS) at 4°C or Heat Stress (HS) at 35°C and ≥60% Relative humidity. Day-old Cobb 500 chicks were placed in battery cages for a 28-d grow out study. The birds were fed a sorghum-soybean meal diet formulated to meet the breeder’s recommendations. A Vit A devoid diet was fed for the initial 14 days to deplete the broiler chicks stores of retinol. On d14, all birds were allocated 6/cage (±1 body weight SD). After 56 days of Vit A storage, 10 test diets containing the CS or HS premixes were pelleted and provided to the birds from d14-28 (8 cages/NC and 10 cages/Vit A diets). Liver and blood samples were collected on d21 and 28 for Vit A analysis. A 2×4 factorial design was used with main effects of storage temperature and Vit A sources. The NC treatment (trt) was statistically analyzed as an ANOVA contrast with each of the 4 Vit A sources. Given a significant interaction between CS or HS, data were analyzed as a one-way ANOVA. P-value was set as ≤0.05 and the means were separated by Duncan’s test. Results showed that hepatic concentrations of retinol were significantly lower in NC and Source D diets in comparison to other trts for both CS and HS at d21 and 28 (P=0.000). However, there was no statistical difference between A-1000 and Source B in levels of hepatic retinol (P=0.000). In addition, circulating plasma retinol concentrations at d28 was significantly lower in the NC trt in comparison to A-1000 and Source B for both CS and HS, but no significant difference was observed between A-1000 and Source B. In the current study, no classic Vit A deficiency symptoms were observed in the NC trt potentially due to the presence of maternal stores of Vit A. In conclusion, based on liver and plasma retinol concentrations, the A-1000 has better availability than Source D but there was no observed difference in comparison to Sources B and C.

Key Words: Vitamin A acetate, Bioavailability, Heat stress, Broiler, Butylated hydroxy toluene.