Vitamin A supplementation in animal feed typically comes in the form of retinyl acetate.

This might lead to the impression that retinyl acetate is the active form of vitamin A that the body needs, which gets metabolised to deliver nutritional functions. However, the fact is the retinyl acetate in the animal diet is digested and absorbed along with fat.

Retinyl acetate is hydrolysed by pancreatic lipase into retinol, which is then incorporated into lipid micelles. Retinol is transferred to mucosal cells upon reaching the microvilli in the intestine, where it is re-esterified to retinyl ester, gets incorporated into chylomicrons and then transported to the lymph for storage in the liver. These stored retinyl esters are hydrolysed to free retinol over time to a complex with retinol binding proteins, which are then transported through the blood to the needed tissues.

Can vitamin A feed additive be delivered in the form of retinol to relieve the animal's metabolic energy load on hydrolysis and re-esterification of retinol?

In theory, this is a good strategy in animal nutrition. However, from a practical perspective, this will be extremely challenging and may not be beneficial to the animal at all.

Why is this?

Retinol is a highly conjugated, unsaturated hydrocarbon molecule with a terminal allylic alcohol. Such a molecular structure predisposes it to undergo rapid oxidative degradation, even at a room temperature of 20°C. In the presence of light and other chemical components, for example, zinc and iron ions in the same matrix, the degradation of retinol can accelerate significantly.

Hence, retinol as a feed additive must be tightly encapsulated to completely screen off light, oxygen and any interaction with the environment. Unfortunately, ambient temperature during storage or harsh conditions during a feed or premix production process are enough to initiate the cascading oxidation of the encapsulated retinol.

On the other hand, a highly stable form of retinol might mean that the encapsulation could be extremely resistant to enzymatic digestion in the animal body, thus resulting in the poor availability of retinol for uptake and metabolism. Therefore, the right technology must be in place to provide high-quality vitamin A feed additive that has good stability during preparation and storage, but yet is readily available for uptake in the animal body. There are a few strategies to maximise the cost-effectiveness of vitamin A feed additive.

Firstly, the esterification of retinol to esters of acetate or propionate reduces the susceptibility towards oxidation, thereby increasing the stability of vitamin A during storage or in harsh processing environments. Secondly, the encapsulation of the retinyl acetate in an enzyme-digestible matrix excludes environmental interactions with the sensitive retinyl moiety, thereby reducing the probability of direct contact with oxygen and trace minerals. Upon ingestion, the specific matrix should be easily digested by the enzymes in the animal body, thus releasing the retinyl acetate for the above-mentioned metabolic processes. Examples of such an encapsulation matrix are fats, proteins, carbohydrates or sugars, or a combination of these. Encapsulation efficiency and protection efficacy will depend on the ingredients used and the encapsulation technology. Finally, the use of approved antioxidants such as butylated hydroxy toluene (BHT) or tocopherol is important to slow down the degradation of retinyl ester. This enables the vitamin A feed additive to preserve its active ingredient over a longer period, as well as to withstand harsh processing conditions in feed or premix production.

BASF follows an optimised combination of these strategies with Lutavit^® A 1000 NXT, thus providing a very high-quality vitamin A feed additive with a 15-month shelf life and excellent stability in premix and feed.

A recent study showed that Lutavit^® A 1000 NXT is stable for up to 15-months being stored at a temperature of 15°C (Figure 1). A third-party comparison of Lutavit^® A 1000 NXT against two other commercially available products (A & B) was conducted using a representative commercial premix and stored at 35°C and 60-70% relative humidity over eight weeks.

The study showed that Lutavit^® A 1000 NXT demonstrates high stability in such commercial premix with a vitamin A recovery of about 55% after 56 days under hot and humid conditions, and the performance is comparable to Product A (Figure 2). The premix stability also significantly outperforms Product B, which shows almost no vitamin A remaining in the premix under such harsh storage conditions.

Lutavit^® A 1000 NXT is produced using a highly controlled beadlet technology process with a tailor-made gelatine-carbohydrate encapsulation matrix, which is easily digested by protease, thus readily releasing vitamin A for metabolism in the animal body.

How does a high-quality vitamin A feed additive add value to the animal nutrition industry?

Firstly, a vitamin A product with a longer shelf life (for example, 15-months) provides a buffer for logistical setbacks and stock accessibility. In these current times of high shipping costs, this can mean cost savings for businesses by consolidating shipments, without compromising premix or feed production efficiency and quality.

The right technology must be in place to provide high-quality vitamin A feed additive.

Vitamin A feed additive with a high degree of stability also results in better efficiency in providing the adequate level of retinyl esters to the animal with minimal level of endogenous degradation in premix matrixes or under feed processing conditions.

Research has also shown that an optimal level of stored vitamin A in the liver improves certain parameters of immune function in the animal and reduces the negative impacts of external stress (for example, heat, over-nutrition) conditions.

In conclusion, Lutavit^® A 1000 NXT is a premium vitamin A feed additive with high stability demonstrated in both shelf life as well as premix stability studies. This high-quality beadlet product is manufactured in Germany using an advanced production technology where retinyl acetate is efficiently encapsulated in an enzyme-digestible matrix, together with an antioxidant to enhance its stability.

Lutavit^® A 1000 NXT has a 15-month shelf life and high stability in premix, both of which are important attributes that positively impact the premix and feed production industry.

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Article made possible through the contribution of DR. KOK-PING CHAN; DR. WOLF PELLETIER; DR. ANDREA KUNTZ, BASF Animal Nutrition

BASF: High Quality Vitamin A Feed Additives Are Critical To The Animal Nutrition Business