DSM in Animal Nutrition & Health
Factor Resulting in Inadequate Vitamin Dietary Intake
Vitamin dietary intake and utilization are influenced by many factors, including particular feed ingredients, bioavailability, harvesting, processing, storage, feed intake, antagonists, best-cost feed formulations and others (NRC, 1973; McDowell, 2000).
A. Agronomic Effects and Harvesting Conditions
Vitamin levels will vary in feed ingredients due to crop location, fertilization, plant genetics, plant disease and weather. Intensive cropping practices and use of new crop varieties may alter or reduce levels of certain vitamins in many feedstuffs. In forage crops, factors that favor production of lush, green plants also favor production of many vitamins, particularly beta-carotene, vitamin E and vitamin K.
Combs and Combs (1984) reported vitamin E activity values, based on corn and grain alpha- and gamma-tocopherol, to be different among 42 varieties of corn. The vitamin E activity varied from 11.1 to 36.4 IU per kg (5.06 to 16.5 IU per lb) of air dried corn, with a mean of 22.7 IU per kg (10.3 IU per lb).
Harvesting conditions often play a major role in the vitamin content of many feedstuffs. Vitamin content of corn is drastically reduced when harvest months are not conducive to full ripening. If corn has been subjected to alternate periods of freezing and thawing while it contains a high amount of moisture, fermentation occurs in corn kernels, and there is a loss of vitamin and nutrient content, particularly of vitamin E and cryptoxanthin. In one study, vitamin E activity in blighted corn was 59% lower than in sound corn and activity of the vitamin in lightweight corn averaged 21% below that in sound corn (Hoffmann-La Roche, 1989). The carotene content in lightweight and moldy corn was also lower than that in sound corn in this study. Young et al. (1975) reported that the rate of oxidation of natural tocopherol was higher in high-moisture corn than in low-moisture corn due to increased peroxidation of the lipid. Certain legumes, particularly alfalfa and soybeans, contain an enzyme, lipoxidase, that unless quickly inactivated, readily destroys much of the carotenoids.
B. Processing and Storage Effects
Many vitamins are delicate substances that can suffer loss of activity due to unfavorable circumstances encountered during processing or storage of premixes and feeds. Vitamins in both feeds and vitamin premixes can be destroyed during extensive storage. Table 5 illustrates vitamin retention in feeds and vitamin premixes after six months storage. After six months, over one-half of the vitamin retention was lost in feeds for vitamin A stabilized beadlets, vitamin K, thiamin HCl and crystalline vitamin C. In vitamin premixes, except for vitamin K and crystalline vitamin C, most vitamins were quite stable unless the vitamin premix also included choline and trace minerals.
Stress factors for vitamins include humidity, pressure (pelleting), heat, light, oxidation-reduction, rancidity, trace minerals, pH and interactions with other vitamins, carriers, enzymes and feed additives (NRC, 1973; Jones, 1986; Gadient, 1986; McDowell and Ward, 2008).
Moisture is the primary factor that can decrease the stability of vitamins in premixes and feedstuffs. Water softens the matrix, for example, of some vitamin A products and thus the vitamin becomes more permeable to oxygen. Trace minerals, acids and bases are activated only by moisture. Humidity augments the negative effect exerted by choline chloride, trace minerals and other chemical reactions that are not found in dry feed. Thus, the moisture level is responsible for a higher vitamin reactivity with other feed components. Elevated moisture content or incorrect storage of premixes and feedstuffs are the root of almost all stability problems. Christensen (1983) determined the stability of vitamin A in a premix. After three months of storage, the vitamin A retention was 88% under low temperature and humidity, and 86% under high temperature and low humidity. Humidity was significantly more stressful than temperature.
Vitamins that undergo friction or that are mixed and stored with minerals and or choline are subject to loss of potency (Table 5). Friction is an important factor because it erodes the coating that protects several vitamins and reduces vitamin crystals to a small particle size. Friction is very high in pelleting. Some abrasion is inevitable in the mixing process, but fortunately most minerals contain little moisture with the exception of salt, which is, of course, somewhat hygroscopic if exposed to environmental moisture. Therefore, packaging, careful transport and storage become important, and few companies would willingly use very high levels of salt in a supplement containing fat-soluble vitamins.
Hazards to vitamins from minerals are abrasion and direct destruction by certain trace elements, particularly cooper, zinc and iron, with manganese and selenium the least reactive. Free metal ion is the most reactive, followed by sulfate, carbonate and oxide. In fat-soluble vitamins, esters are significantly more stable than alcohols. The hydroxy group of alcohols is extremely sensitive to oxidation. The five double bonds in retinyl acetate still make the compound sensitive to oxidation. Vitamin A is significantly more stable in vitamin premixes than in vitamin-trace mineral premixes because trace minerals catalyze oxidation of the five double bonds (Gadient, 1986). Dove and Ewan (1991) determined the stability of alpha-tocopherol in feeds without and with trace minerals. At the end of the three months of storage at 25°C or 30°C, alpha-tocopherol retention was 50% and 30%, respectively. Further addition of 245 ppm copper as copper sulfate, produced 0% retention after 15 days. Like trace minerals, choline chloride is highly destructive to vitamins and should not be included in a vitamin premix.
Some vitamins are destroyed by light. Riboflavin is stable to most factors involved in processing; however, it is readily destroyed by either visible or ultraviolet (UV) light. Similarly, vitamin A, vitamin B6, vitamin C and folic acid can also be destroyed by light (Table 6). It is necessary, therefore, to protect premixes of feeds containing these vitamins from light and radiation (Stamberg and Peterson, 1946).
Sun-field curing of cut hay is essential to provide vitamin D3 activity, but results in loss of other vitamin potency. Mangelson et al. (1949) showed that mechanical dehydration at 177°C within one hour after cutting, produced an alfalfa meal that contained 2.5 times more carotene than did sun-cured alfalfa. There was no loss of riboflavin, pantothenic acid, niacin or folic acid during dehydration. Field-cured alfalfa was lower in riboflavin, and when alfalfa was exposed to rain, there was a large loss of pantothenic acid and niacin (Scott, 1973).
Dehydration of alfalfa at 135°C resulted in an average 18% loss of alpha-tocopherol. When dehydrated alfalfa meal was stored for 12 weeks at 32°C, the alpha-tocopherol loss averaged 65% (Livingston et al., 1968). Corn is often dried rapidly under high temperatures, resulting in losses of vitamin E activity and other heat-sensitive vitamins. When corn was artificially dried for 40 minutes at 88°C, losses of alpha-tocopherol averaged 19%, and when corn was dried for 54 minutes at 107°C, losses averaged 41% (Adams, 1973).
Preservation of most grains by ensiling will cause almost complete loss of vitamin E activity and likely destruction of other vitamins. Acid treatment of grain (i.e., propionic acid) can result in grains containing less than 1 mg per kg (0.45 mg per lb) of alpha-tocopherol (McMurray et al., 1980). The destructive effect is apparently the combined action of the acid and high moisture content. Sulfur dioxide is also used as a preservative for high-moisture grains; however, this is reported to destroy dietary thiamin.
While pelleting generally improves the value of energy and protein carriers in a feed, this is not true for some vitamins. During pelleting of feeds, four stressors that destroy some vitamins are applied in combination: heat, humidity, pressure and friction. Increasing the pelleting temperature or conditioning time generally enhances redox reactions and destroys vitamins. Table 7 shows typical losses of commercial forms of vitamins under a range of pelleting conditions (Ward, 2005).
Vitamins and vitamin product forms vary in their susceptibility to these stressors. Significant amounts of vitamin E in the alcohol form, but very little in the acetate form, are destroyed as pelleting temperatures and conditioning times increase. Gadient (1986) reports that vitamins A, D3, K3, C and thiamin are most likely to show stability problems in pelleted feeds. Pelleting of feed may have a beneficial effect on availability of vitamins such as niacin and biotin, which are often present in bound forms (Scott, 1973). In recent years, feed manufacturers have increased pelleting temperatures for all animal feeds to control Salmonella and increase digestibility. The use of steam pelleting, pre-pelleting conditioners and feed expanders, also lead to increased vitamin degradation (Gadient, 1986).
In extrusion, the dominant stress factors are pressure, heat, moisture, and redox reactions. Extrusion is the most aggressive process against vitamins due to the high temperatures (107-135°C), pressure (400-1,000 PSI), and moisture (30%) involved in the process (Gadient, 1986).
Processing with the goal of producing better quality fish meals and fish solubles under conditions where putrefaction is prevented has actually resulted in lower levels of vitamin K and vitamin B12 in these feedstuffs than were present when the products were allowed to undergo a considerable degree of putrefaction. Early studies on vitamin K and vitamin B12 proved that fish meal and rice bran exposed to the action of microorganisms showed increases in content of these vitamins. On the other hand, processing of raw fish with heat is required to inactivate a potent thiaminase that destroys thiamin. Also, attempts to preserve fish with nitrates led to the production of carcinogenic nitrosamines.
The composition and the various methods applied to both wet (canned), semi-moist and dry types of pet food are very exacting and potentially destructive to nutrients such as vitamins (Hilton, 1989). For example, vitamin A losses encountered in extruded cat and dog foods varies from 20% to 35%, while in canned and semi-moist cat and dog food the losses are much lower (Table 8). In contrast, thiamin losses in canned foods would appear to be significantly higher than in extruded type feeds.
Studies on the stability of various vitamins in dog and cat foods were published previously (Gadient, 1989). Table 9 illustrates the vitamin concentration of a canned dog food before and after retorting (Hoffmann-La Roche, 1981). Vitamins A, E, riboflavin, B12, vitamin B6, pantothenic acid, niacin and biotin showed good retention in the dog food after processing, but there were substantial losses of thiamin and folic acid.
Stability of vitamins in an extruded dog food fortified with a multivitamin premix was determined. After processing (i.e., extrusion for 12 seconds at 107°C and drying for 15 minutes) there were considerable losses of vitamin A, riboflavin, folic acid, niacin and biotin (Table 10). Apparently extrusion reduces stability of most vitamins to a greater extent than retorting, whereas retorting appears to decrease stability of thiamin and folic acid to a greater extent than extrusion. A possible explanation for this is the difference in pH of canned and extruded dog foods; thiamin and folic acid are less stable at pH 6 and above compared to other vitamins.
Stability of vitamins D3and K (menadione) in cat foods was evaluated after processing (Hoffmann-La Roche, 1981). Vitamin D3was relatively stable, retaining 89% to 91% of activity after processing. However, menadione losses were greater in the canned (55%) and extruded (74%) cat foods than in the semi-moist (24%) cat food. Supplemental vitamins A and E were added to a dry cat food with vitamin assays being performed on the formulation before and after extrusion. During extrusion, a vitamin A loss of 31% and a vitamin E loss of 25% occurred.
Providing vitamins to fish is a problem as the diet is in contact with water. The problem is greatest with vitamin C; even before feed was placed in the water approximately 50% of the supplemental vitamin C was destroyed during the manufacture of extruded catfish feed (Lowell and Lim, 1978). The vitamin C status of the fish is improved by providing excess vitamin C in commercial formulations and using more stable forms of the vitamin (e.g., polyphosphorylated ascorbic acid).
Concentrate feed ingredients have changed in recent years, influencing the vitamin concentrations of diets as well as vitamin requirements for both farm animals and pets. For example, fats have changed. Fats originally available to the feed industry were primarily from renderers or butcher’s scraps and dead animals; they were relatively stable. With the rapid expansion of fast food restaurants, there is greater feed use of grease and unsaturated fatty acids with an increased propensity toward oxidation (Corbin, 1995). The peroxides formed as fats oxidize can interact with and destroy fat-soluble vitamins as well as others such as biotin. Extensive oxidation can result in catastrophic pathological problems in farm livestock and pets, including exudative diathesis, steatitis (in cats), arteriosclerosis, muscular dystrophy, hair loss and associated mortality. Animal fats that smell rancid are most destructive to fat-soluble vitamins when their peroxide value (PV) is greater than 20 mg per kg of fat (Corbin, 1995). Oxidative rancidity may create off-odors and off-flavors, destroy essential fatty acids and fat-soluble vitamins and even produce toxic compounds (Kappus, 1991).
Due to changes in processing methods, meat and bone meals are now considerably less digestible than before. Also, hydrolyzed feathers and hair are being included in both farm livestock and pet foods at higher concentrations. These changes in protein sources decrease the bioavailable vitamin contribution expected from use of animal by-products.
C. Reduced Feed Intake
When feed intake is reduced, vitamin allowances should be adjusted to assure adequate vitamin intake for optimum performance. Restricted feeding programs and/or improved feed conversion will decrease dietary intake of all nutrients, including vitamins. Restricted feeding of broiler breeders, turkey breeder hens, gestating sows and gilts, and wintering beef cows may result in marginal vitamin intake if diets are not adequately fortified (Hoffmann-La Roche, 1989).
For poultry, vitamin feed intake per unit of output is continually declining. The yearly decline for layers is around 1% per egg produced, while for broilers has been 0.6-0.8 % per kg (0.27 to 0.36 per lb) body gain (Leeson, 2007). It is important to realize that vitamin content of eggs today is lower than it was in 1995. Feeding the same levels of vitamins, Pérez-Vendrell et al. (2002) reported vitamin A, vitamin E and vitamin B12 decreasing by 25.1, 37.5 and 33.0 percent, respectively, compared to the concentrations in 1995. The reason for lower vitamin content in recent years is likely due to improvement of layer feed conversion as a result of better poultry genetics and management. Obviously, a lower total feed intake due to improved feed efficiency will make less quantity of vitamins available to be transferred to eggs. This would apply to production of poultry meat as well, as there would be less vitamins transferred to the meat.
When pet owners decide to cut back feed to overweight pets, not only is the energy-protein reduced, but so are other essential nutrients such as vitamins. Finicky eaters such as cats and toy dog breeds need more palatable and nutrient-dense food because of their low intake levels. Reduced feed intake may also result from stress and disease.
Use of high-energy feeds such as fats to provide diets with greater nutrient density for higher animal performance requires a higher vitamin concentration in feeds. Non-ruminant species provided diets ad libitum consume quantities sufficient to meet energy requirements. Thus, vitamin fortification must be increased for higher energy diets as animals will consume less total feed. Feed consumption comparisons for broilers receiving metabolizable energy ranging from 2,800 to 3,550 kcal kg were made (Friesecke, 1975). Feed consumption, and likewise vitamin consumption, were 19.1% lower for the diet with the greater energy density compared to the lowest energy diet.
Ambient temperature also has an important influence on diet consumption. Animals consume greater quantities of feed during cold temperatures and reduced amounts as a result of heat stressed. Vitamins, as well as other nutrients, must therefore be adjusted to reflect changing dietary intakes. Table 11 illustrates intake of a ration as affected by dietary energy content and environmental temperature for caged leghorn layers (North, 1979).
D. Vitamin Variability and Insufficient Analysis
Tables of feed and food composition demonstrate the lack of complete vitamin information, with vitamin levels varying widely within a given feedstuff. Kurnick et al. (1972) found that, for the feeds surveyed, information on the niacin and riboflavin content of feedstuffs was more complete than for any other vitamins, whereas values for vitamin B12 and vitamin K were most deficient. Thus, 2% to 30% of the ingredients lacked niacin, riboflavin or pantothenic acid values, while 89% to 97% did not have values for carotene, vitamin B12 or vitamin K. Information about the other vitamins was not listed for 36% to 64% of the ingredients. Over 25 years have passed since this report, and the situation has not greatly improved; vitamin analyses of feed remain woefully inadequate.
Variability of vitamin content within ingredients is generally large and difficult to quantify and anticipate. It is well recognized that vitamin levels shown in tables of vitamin composition of feedstuffs represent average values and that actual vitamin content of each feedstuff varies over a fairly wide range. Vitamin content of feed ingredients differs drastically from sample to sample; therefore, nutrient values used in formulation should be reduced by at least two standard deviations (avg. 10%) as a safety margin. Also, several months or more elapse between harvest, processing and finally consumption of feed ingredients. Since most natural vitamins are not chemically protected in feed ingredients, there is considerable loss between harvesting and consumption (avg. 25% loss) (BASF, 1991). Feed table averages are often of little value in predicting individual vitamin content of feedstuffs or bioavailability of vitamins. Vitamin E content of 42 varieties of corn varied from 11.1 to 36.4 IU per kg, a 3.3-fold difference. For 65 samples of corn, biotin varied between 0.012 and 0.072 ppm, a 6-fold difference (McDowell and Ward, 2008).
Methods of processing, storage and analysis contribute to variability in nutrient values. The wide analyses variation of many vitamins in feedstuffs is shown in Table 12 (Kurnick et al., 1972). Often, it is questionable whether the accuracy of vitamin levels from feedstuffs, calculated using tabular values, can be assured (Kurnick et al., 1972). Proof of this is the statement by the 1982 NRC publication on U.S.- Canadian Tables of Feed Composition that “organic constituents (e.g., crude protein, cell wall constituents, ether extract and amino acids) can vary as much as ±15%, the inorganic constituents as much as ±30%, and the energy values as much as ±10%.” Therefore, average values in feed composition tables may vary considerably from the nutrient value of a specific group of feeds.
E. Vitamin Bioavailability
Even accurate analyses of vitamin concentrations do not provide bioavailability data needed for certain vitamins. Bound forms of vitamins in natural ingredients often are unavailable to animals. Bioavailability of choline, niacin and vitamin B6 is adequate in some feeds but limited or variable in other ingredients. For example, bioavailability of choline is 100% in corn but varies from 60% to 75% in soybean meal; that of niacin is 100% in soybean meal but 0% in wheat and sorghum and varies from 0% to 30% in corn; that of vitamin B6 is 65% in soybean meal and varies from 45% to 56% in corn (Hoffmann-La Roche, 1991). The niacin in cereal grains and their by-products is in a bound form. It is probable that bound forms of vitamins are also not available to microorganisms in the rumen
There is virtually no information on the bioavailability of nutrients for companion animals in many of the common dietary ingredients used in pet foods. These ingredients include by-products of the meat, poultry and fishing industries, with the potential for wide variation in nutrient composition (Morris Rogers, 1994).
Some data have been obtained with the pig showing that responses to vitamins may differ depending on whether vitamins are being added to a purified or to a natural diet (Cunha, 1977). Requirements of the pig for niacin, riboflavin and pantothenic acid were considerably higher on a natural diet than requirements established earlier from experiments using purified diets (McMillen et al., 1949). This shows that results obtained with purified diets must also be verified with natural diets and that bioavailability of vitamins may be greater in purified diets.
It is incorrect to assume that vitamins from natural feed sources are more bioavailable than sources derived from synthesis. As an example, several lines of evidence indicate higher bioavailability of added folic acid than naturally occurring folates in many foods (Gregory, 2001). Pyridoxine-5’-beta-D-glucoside (PNG), a conjugated form of vitamin B6, has been shown to be abundant in various plant-derived foods (McCormick, 2006). This form of vitamin B6 may account for up to 50% of the total vitamin B6 content of oilseeds such as soybeans and sunflower seeds. The utilization of dietary PNG relative to pyridoxine has been shown to be 30% in rats and 50% in humans (Gregory et al., 1991). In suckling rats, the availability of vitamin B6 derived from PNG is only 25% compared with pyridoxine (Trumbo and Gregory, 1989). Therefore, the synthesized form of vitamin B6, pyridoxine, would have a much higher bioavailability than the vitamin from feed sources.
F. Computerized Best-Cost Feed Formulations
Vitamins are usually not entered as specifications in computer feed formulations. Therefore, vitamin-rich feedstuffs, such as alfalfa, distiller’s solubles or grains, brewer’s grains, fermentation products, and meat, milk, and fish by-products, are often excluded or reduced when best-cost feed formulations are computed. The resulting best-cost diet consisting of grain and soybean meal is usually lower in vitamins than a more complex one containing more costly vitamin-rich feeds (Roche, 1979). Therefore, total vitamin supplementation with a complete premix is the most efficient method to ensure adequate vitamin allowances.