Understanding the sensitivity and stability of
vitamins By Amir Attar, Alireza Abbasipour, Samira Hassanpour New Millennium Feed Processing Co. (www.nmfeed.com), Mashhad, Iran
Introduction
The stability characteristics differ across a variety of conditions for
Feed technology has progressed in the past two decades. However,
the full collective of important vitamins. It is the unique chemical
NRC (1994) vitamin requirements for monogastric animals have not
structure and other characteristics of each vitamin that directs
altered to any great extent due to limited research in this field. Vitamins
the type of stabilization or formulation. For example, heat can be
are important for livestock nutrition and performance. They are
especially destructive to vitamin A, folic acid, or vitamin B but has
intentionally added to animal feed in order to achieve the improvement
little consequence on niacin or riboflavin. Therefore, the focus on
of health and growth of animals and the characteristics of products
some vitamins is their weaknesses to heat, knowing that most feed
of animal origin. Additionally, if lacking from the diet, vitamins can
processing methods utilize heat.
cause a specific deficiency disease because they are essential for normal metabolism. Vitamins, as biologically active biochemicals, are
Factors affecting vitamin stability
generally quite delicate to their physical and chemical environment.
Vitamin stability in premixes is affected by exposure to light, heat,
Feed processes tend to improve the distribution of nutrients
moisture, oxygen, and pH, and contact with other compounds. These
(premixing) and the digestibility of carbohydrates (pelleting, extrusion).
factors subject vitamins to degradation primarily through oxidation.
However, these processes are harmful to labile nutrients, such as
The long-term or multiple exposures to these factors generally magnify
vitamins, that can be easily oxidized.
the negative impact on vitamin stability. The individual vitamins vary
Vitamin formulations vary significantly in complexity and cost.
in their susceptibility to degradation (Table 1).
Cost is a very important factor because the vitamin manufacturing costs are passed on to the consumer. Manufacturing processes should
Pelleting
not only be evaluated based on physio-chemical properties of the
Conditioning/pelleting temperature is the most obvious contributor to
vitamin, but also the need to further process the vitamin to improve
vitamin losses for poultry feed. According to Van’t Hoff’s Rule, an increase
handling properties and stability through feed processing.
in temperature by 10°C will increase the rate of chemical reactions by 2- to 3-fold. Thus, the integrity of the vitamin is threatened with exposure
Vitamin stability
to oxygen and trace minerals, during conditioning of feeds.
The stability of vitamins in a premix is critical in maintaining vitamin
Conditioning time affects vitamin degradation, with a longer
potency. Susceptibility to degradation varies depending on individual
conditioning time posing the greater threat. The goal of conditioning
vitamins and on a number of factors that affect vitamin stability. Safety
feed is to uniformly penetrate each feed particle with moisture and
margins for vitamin premix formulation are usually based upon vitamin
heat. Under pressure and with rigorous mixing in the feed conditioner,
cost, presence or absence of trace minerals and choline in the premix,
this creates an environment especially harsh to vitamins and other
feed processing characteristics, environmental conditions, anticipated
feed additives. Often, moisture is increased to 17-18%, and provides
storage time, and expected rates of vitamin potency losses.
a solvent for destructive agents since moisture is often essential for
Not all vitamins are equal in stability. Commercial vitamins for
harmful chemical reactions.
feeds and foods are formulated to counter anticipated stresses,
The type of feed, mineral and fat content must be considered.
and these formulations act as a buffer between the vitamin and the
Each brings characteristics that can influence the degree of friction
aggressor. Differences exist in the stability of vitamins in their natural
as the feed passes through the die. At least theoretically, we expect
form. The ability of vitamins to withstand the rigors of storage in
lower vitamin degradation in finisher type diets (i.e. higher fat, lower
mineral premixes or in the presence of choline chloride is not good.
mineral content).
Feed Compounder May/June 2021 Page 45
