Abstract This experiment evaluated the risk of vitamin A loss cattle producers face when storing free-choice mineral and vitamin mixes, stability may be reduced by elevated temperature, humidity, and interactions with trace minerals that accelerate oxidative degradation. The vitamin A content in a mineral mix was evaluated over 6-months (April-August) in Lincoln, NE. The mix was bagged in 22.6 kg increments using three bag types, 1) biaxially oriented polypropylene, 2) paper with a polypropylene liner, 3) laminate and was stored in two locations, feed room (FR) and metal barn (MB). These locations were targeted to represent common storage systems that feed stores and producers use. Vitamin A, retinol-acetate (Zhejiang Medicine Company, China) , as a cross linked gelatin bead let, was added to achieve 694,260 ± 16,448 IU/kg in a free choice supplement that contained 25% salt, 10% dried distillers grains, 882 IU/kg of vitamin E and 2,000, 4,000 and 4,000 mg/kg of copper, manganese and zinc, from sulfate. The product was mixed in four batches, which served as replicates. Within batch, bagging order was stratified in six bag increments to control for bagging order; bag type was randomly assigned within each stratification, storage location was subsequently randomly assigned within stratification by bag type, and sampling timepoint was randomly assigned within batch, bag type, and location. Samples were collected at the start of the trial (d 0) and monthly thereafter through d 120, with a final sampling at d 180. One bag from each batch × bag type × location combination was sampled at each timepoint. Data were analyzed as a repeated-measures design, with bag as the experimental unit and storage location included as a blocking factor. Bagging order out of mill was used as a co-variate (P = 0.07). Storage location (P = 0.08) tended to affect vitamin A content of the mix where FR (684,714 ± 9506 IU/kg) was 3.65% greater than MB (659,955 ± 9,834 IU/kg). Mean temperature was 20.8 ± 1.37 °C and 26.2 ± 7.04 °C for FR and MB, respectively. Mean humidity was 59.9 ± 10.9% and 53.02 ± 12.99% for FR and MB, respectively. The two-way interaction of bag type x timepoint (P = 0.92) and the main effect of bag type (P = 0.89) were not significant. A significant effect of time (P 0.01) was detected; however, no consistent trend was observed, with vitamin A concentrations being 89%, 96%, 102%, 104%, and 90% of the initial content at d 30, 60, 90, 120, and 180, respectively. Vitamin A in this mix was stable over six months of storage regardless of bag type or storage location, suggesting that current manufacturing methods produce a product with adequate vitamin A stability under common storage conditions.
Wansing et al. (Wed,) studied this question.