The NRC and Agriculture Research Council vitamin requirements are usually close to minimal levels required to prevent deficiency signs and maintain acceptable health and performance, provided sufficient amounts of other nutrients are supplied. Most nutritionists concur with this, and consequently vitamins are supplemented above NRC requirements based on experience within industry situations where higher vitamin levels are needed.
The optimum vitamin nutrition concept is designed to demonstrate why vitamin levels higher than those required to prevent deficiencies may be needed to achieve desired health and performance. This concept should provide improved economic returns for producers. To understand this concept, which is applicable to any animal species, it is necessary to define the following terms as applied to vitamins: minimal and optimal requirements, total levels and allowances.
A. Minimal requirements are the vitamin levels required by an animal to prevent overt clinical deficiency signs and conditions and maintain acceptable health and performance, provided sufficient amounts of all other nutrients are supplied.
B. Optimal requirements are the vitamin levels required by an animal to prevent marginal (undetected) deficiencies and inadequacies to allow optimal health and performance. Inadequacy means that the vitamin levels are too low to maintain a specific normal biological function such as immune competence, even though these levels may be adequate for another function such as growth.
C. Total vitamin levels are vitamin levels from all sources in the diet. Total levels of a vitamin consist of the supplemental levels added to fortify the ration (fortification levels) plus the levels of the vitamin supplied by feedstuffs.
D. Allowances are total vitamin levels fed to meet the vitamin needs of livestock under commercial production conditions. Allowances of a vitamin are those total levels from all sources fed to compensate for factors influencing vitamin needs of animals.
These influencing factors that affect vitamin requirements include those that may lead to inadequate levels of the vitamin in the diet and those that may affect the animal’s ability to utilize the vitamin under commercial production conditions. The higher the allowance, the greater the extent to which it may compensate for the influencing factors. Thus, under commercial production conditions, vitamin allowances higher than NRC requirements may be needed to achieve the desired level of performance (Perry and Zimmerman, 1979a, b). Generally, the optimum supplementation level is the quantity that achieves the best growth rate, feed utilization and health (including immune competency) and provides adequate body reserves (Gadient, 1986).
The concept of optimum vitamin nutrition under commercial production conditions is illustrated in Figure 14 (Roche, 1979). The marginal zone in Figure 14 represents vitamin levels that are lower than requirements and may predispose animals to deficiency. The requirement zones are minimum vitamin quantities that are needed to prevent deficiency signs, but may lead to sub-optimum performance even though animals appear normal. Feeding vitamin levels lower than minimal requirements predisposes animals to deficiency risk. Clinical deficiency signs and conditions are prevented by minimal requirements; however, this may lead to sub-optimal health and performance.
The optimum allowances in Figure 14 permit animals to achieve their full genetic potential for optimum performance. In the excess zone, vitamin levels range from levels still safe, but uneconomical, to concentrations that may produce a toxic effect. Usually only vitamins A and D, under practical feeding conditions, pose the possibility of toxicity problems for animals. Optimum allowances of any vitamin are depicted as a range in Figure 14 because factors influencing vitamin needs are highly variable, and optimum allowances to allow maximum response may vary from animal to animal of the same species, type and age within the same population and from day to day (Roche, 1979). Optimal responses vary depending upon the severity of the influencing factors. For example, under mild stress, a relatively lower allowance may be adequate, and under severe stress, a relatively higher allowance may be needed.
It should be emphasized that subacute deficiencies can exist although the actual deficiency signs do not appear. Such borderline deficiencies are both the most costly and the most difficult with which to cope. They often go unnoticed and unrectified, yet may result in poor and expensive gains, impaired reproduction or depressed production. Also, under farm conditions, one will usually not find a single vitamin deficiency. Instead, deficiencies are usually a combination of factors, and often deficiency signs will not be clear cut. If the NRC minimum requirement for a vitamin is the level that barely prevents clinical deficiency signs, then this level moves in relationship to the level required for optimum responses. This means that if a greater quantity of a vitamin is required for an optimum response (because of the influencing factors), a greater quantity would also be required to prevent deficiency signs.
Similarly, if a lesser quantity is required for an optimum response, less would also be required to prevent deficiencies (Perry, 1978). Optimum animal performance required under modern commercial conditions cannot be obtained by fortifying diets to just meet minimum vitamin requirements. Establishment of adequate margins of safety must provide for those factors that may increase certain dietary vitamin requirements and for variability in inactive vitamin potencies and availability within individual feed ingredients.
The NRC requirements often do not take into account that certain vitamins have special functions in relation to disease conditions with higher than recommended levels needed for response (Cunha, 1985; McDowell and Ward, 2008). The NRC (1994) vitamin K requirement in growing chicks in 0.5 mg per kg (0.23 mg per lb) of diet. However,Scott et al. (1982) concluded that as much as 8 mg of vitamin K per kg of diet (3.6 mg per lb) was needed for chicks with coccidiosis. In pigs artificially infected with Treponema hyodysenteriae, the agent causing diarrhea, high supplementation with vitamin E (200 mg per day) in combination with selenium (0.2 mg per day) markedly reduced the number of pigs that became clinically ill (Tiege et al. 1978). Clinical signs and pathological changes were less severe compared with vitamin E-deficient pigs. Thus, higher levels of vitamin E increase resistance against disease. In practice, feeds contaminated with mycotoxins increase requirements for fat-soluble and other vitamins (e.g., biotin, folic acid and possibly others) and therefore supplementation should be increased above NRC requirements. Apart from fat-soluble vitamins, additions of folacin (Purser, 1981) and biotin (Cunha, 1984) will improve performance in pigs fed moldy grains and feeds. Besides other nutrients, vitamins play a major role in immune response, the body’s defense system against infectious disease. Vitamin supplementation above requirements has been shown to be required for optimum immune responses (Ellis and Vorhies, 1976; Cunha, 1985; Weiss, 1998; Beck, 2007; Stahly et al., 2007; Abdukalykov et al., 2008; Leeson, 2008; McDowell and Ward, 2008; Sheridan and Beck, 2008; Ahmad et al., 2009; Silva et al., 2009).
To compensate for the influencing factors occurring in commercial operations, the poultry industry has more closely attempted to recommend higher supplementation levels for poultry diets. The industry vitamin average allowances have increased significantly (30 to 500%) to keep pace with greater genetic potential, faster growth rates, better feed efficiency, poorer quality ingredients, larger poultry houses, and generally higher disease levels, all of which caused increased stress.
It is of interest to note that in 1925 it took 112 days for a broiler chicken to be ready for market. The average market weight was 1.14 kg (0.52 lb) and it took 2.14kg (0.97 lb) of feed for the bird to put on a kg (lb) of gain. Bird mortality was high in 1925, averaging 18%. Today it only takes 48 days to get a bird to the market weight of 2.5 kg (1.14 lb) and it only requires 0.89 kg (0.41 lb) of feed per kg (lb) of gain, with mortality rates of 4%. A reasonable amount of logic would suggest that vitamin requirements determined decades ago may not apply to today’s poultry industry (Dudley-Cash, 1994). NOTE: Please have Nelson change this paragraph 1.141g would be 2.513 lbs FEED EFFECIENCY in the same numbers whether you SAY kg/lb or lbs/lbs.
Commercial supplementation levels of most vitamins for poultry often reflect stresses encountered under production practices. Over 90% of the broilers, turkeys and laying hens were included in two broad surveys of vitamin supplementation rates (Ward, 1993; 2005); levels for most vitamins were substantially higher than NRC recommendations.
There has been little research on poultry vitamin requirements during the last 40 years and unfortunately new-NRC poultry requirements still rely on these older established requirements (Leeson, 2007). As an example, vitamin requirements for egg production as suggested by the NRC (1994) have changed little over the last 30 to 50 years. However, during this time period, layer feed conversion rates have dramatically improved by approximately 40% based on a higher egg mass production (approximately 30%) and lower feed consumption (approximately 10%) (Pérez-Vendrell et al., 2003b). Broiler vitamin requirements have likewise changed little in recent years. However, for the last 30 years broiler feed conversion rates have improved dramatically, more than 20%, due to a much higher body weight in a shorter production period. On the other hand, modern broiler production systems often place animals under high stress conditions so that an optimum level of vitamins in feed is essential to allow birds to achieve their full potential while maintaining good health.
Dritz et al. (1995) fed sows higher vitamin concentrations than NRC requirements with the result of 0.1 more pigs born alive, 0.2 more pigs weaned per litter and weaned pigs 1.1 kg heavier than controls. Stahly (1994) fed growing pigs under two management schemes to create a moderate or high level of antigen exposure. Within each antigen group, pigs were fed one of five dietary concentrations of B-vitamins (niacin, riboflavin, pantothenic acid, B12, folic acid). The addition of B-vitamin concentrations of 370% to 470% above the current NRC (1998) resulted in a 21% greater body weight gain and a 10% improvement in feed utilization for pigs in either antigen group. Higher vitamin fortification has been reported to influence the lean tissue accretion possible with modern genetics (Lindemann et al., 1999).
Another concern with the NRC recommendations is that the older research studies involved purified diets (Leeson, 2008) particularly for monogastric species. These diets often contained purified ingredients that were highly digestible and were not encumbered with facets of variable nutrient availability. Also, the actual minimum nutritional requirement for vitamins is difficult to access as it is most often determined under favorable experimental conditions. The NRC requirements for poultry and swine were determined under optimal rearing conditions, thereby implying that these levels should be increased under “field conditions” (Catain et al., 2003). In this regard, it is suspected that virtually all data used in the compilation of NRC requirements for poultry and swine were derived from studies where animals were in optimum health and not under immunological stress (McDowell, 2000; Leeson, 2007). This would not be the case for many commercial operations.
Supplementation allowances need to reflect different management systems, and be high enough to allow for fluctuation in environmental temperatures, energy content of feed or other factors that influence feed consumption. Optimum concentrations of vitamins in animal diets allow today’s livestock, fish and poultry to perform to their genetic potential. Vitamin requirements established decades ago do not take into account the modern genetically superior animals with increased growth, egg production, milk production, improved feed efficiency, etc. Also, vitamin allowances today need to take into account modern management procedures that increase animal densities and stress conditions for the producing birds. Vitamins are important for maintaining optimum immune response. Higher levels of vitamins (e.g., vitamins A, carotenoids, E and C) have been shown to increase overall health by improving disease resistance as a result of improved immunity. Thus, under commercial production conditions, vitamin allowances higher than NRC requirements may be needed to allow optimum performance. Generally, the optimum supplementation level is the vitamin concentration that achieves the best growth rate, feed utilization and health (including immune competency) and provides adequate body reserves.
During recent years, increased interest has been given toward the elimination of vitamin supplementation from poultry and swine diets for varying lengths of time. Research reported by Skinner et al. (1991), for example, found that broiler performance was not impaired when vitamin supplementation was deleted from the diet for the last 21 days of the feeding period. In contrast with these results, however, Gwyther et al. (1992) reported that NRC vitamin recommendations were much too low to maintain broiler performance. This latter study indicates that broiler vitamin requirements exceed those recommended by the NRC, and that the elimination of vitamin supplementation from broiler diets would severely impair performance. Teeter and Deyhim (1996) eliminated vitamins and/or minerals from broiler diets for the last 21 days of life, a period during which the birds were exposed to heat stress. There was significant reduction in live bird and carcass performance. Performance tended to be poorest when the diet contained added trace minerals and no added vitamins, suggesting oxidation of the vitamins already present. Shaw et al (2002) removed the vitamin premix in growing pigs 28 days prior to slaughter; this withdrawal significantly reduced riboflavin in the longissimus dorsi muscle.
Research from Floridahas shown a beneficial response for vitamin E supplementation on male reproduction of bulls fed high concentrations of gossypol. Velasquez-Pereira et al. (1998) reported that bulls which receive 14 mg free gossypol per kg body weight had a lower (P<0.05) percentage of normal sperm than those which also received supplemental vitamin E, 31% versus 55%, respectively (Table 24). Likewise, sperm production per gram of parenchyma and total daily sperm production were higher (P<0.05) when gossypol-treated animals also received vitamin E. Bulls receiving gossypol exhibited more sexual inactivity (P>0.05) than bulls in other treatments (Table 25). Vitamin E supplementation to bulls receiving gossypol improved number of mounts in the first test and time of first service in the second test. The final conclusion of the Florida data is that vitamin E is effective in reducing or eliminating important gossypol toxicity effects for male cattle.
Many attempts have been made to control lipid oxidation in meats through the use of antioxidants. In order to improve the oxidative stability and thus increase the quality and shelf life of meat and eggs, antioxidants (e.g., vitamin E, vitamin C and carotenoids) have been added to animal feeds (McDowell, 2006; Guo et al., 2006a,b; Morel et al., 2008; Bou et al., 2005; Barroeta, 2007). Dietary supplementation of vitamin E and intravenous infusion of vitamin C immediately before slaughter are efficacious techniques for increasing the concentration of these vitamins in beef skeletal muscle (Schaefer et al., 1995). Meat with elevated levels of either and probably both of these antioxidant vitamins possesses greater stability of oxymyoglobin and lipid, which results in less discoloration and rancidity. Vitamin E would seem to be the most practical, since it is administered dietetically. Vitamin E functions as a lipid-soluble antioxidant in cell membranes (Linder, 1985), thus protecting phospholipids and even cholesterol against oxidations. Increased dietary levels of vitamin E result in higher tissue alpha-tocopherol concentrations and greater stability of these tissues toward lipid oxidation (Yang et al., 2002; Formanek et al., 2003) Buckley and Connolly (1980) reduced the rate of rancidity development in frozen pork by including vitamin E in the feed (80 mg per day per animal) for seven days before slaughter. In order to improve the oxidative stability, and thus increase the shelf life of pork, different antioxidants such as carotenoids, vitamin C, selenium and plant extracts have been tested in different experiments to verify their potential antioxidant effect on pork quality (Kerth et al., 2001; Hasty et al., 2002; Peeters et al., 2005; Guoet al., 2006a,b; Morel et al., 2008). Of them all, alpha-tocopherol demonstrated the highest biological efficiency in preventing the lipid oxidation in vivo.
Increased antioxidative stability in skeletal muscle of poultry is beneficial to avoid or delay the development of rancid products or warmed-over flavor (Ruiz et al., 2001). Supplemental vitamin E will increase the alpha-tocopheral in tissue (Lanari et al., 2004; Bou et al., 2006) and alleviate oxidative stress and rancidity levels in chicken meat (Ruiz et al., 2001; Fellenberg and Speisky, 2006; Gao et al., 2010; Singh et al., 2010). The increased oxidative stability of lipids from the Musculus pectoralis major was observed after dietary treatment of alpha-tocopherol supplemented solely (Goñiet al., 2007) or with ascorbic acid (Young et al., 2003).
Supplementing finishing steers with vitamin E (500 IU per head daily) has been observed to dramatically increase the stability of beef color (Faustman et al., 1989a). Loin steaks of control steers discolored two to three days sooner than those supplemented with vitamin E. Supplemental dietary vitamin E extended the color shelf-life of loin steaks from 3.7 to 6.3 days. This was most likely due to the increased alpha-tocopherol content of the loin tissue of the supplemented animals, which was approximately four-fold greater than controls (Faustman et al., 1989a). Color is an extremely critical component of fresh red meat and greatly influences consumer perception of meat quality. Steaks from cattle supplemented with vitamin E were preferred over control steaks by 91% of Japanese survey participants (n=10,941), and 58% of all participants identified muscle color as the most important factor in selecting beef products (Sanders et al., 1997).
In a subsequent report, Faustman et al. (1989b) observed that vitamin E stabilized the pigments and lipids of meat from the supplemented steers. Perhaps the vitamin E-supplemented steers were able to incorporate a greater amount of vitamin E as an in vivo lipid stabilizer. The vitamin’s effect on flavor and storage properties of various meats have been reviewed. Supplementing cattle with vitamin E resulted in steaks that exhibited superior lean color, less surface discoloration, more desirable overall appearance and less lipid oxidation during retail display than control steaks (Sanders et al., 1997). Likewise, Roeber et al. (2001) had improved color of ground beef by feeding 1,000 IU of vitamin E daily for the last 100 days of the finishing period.
As was true for beef, supplementation of diets with vitamin E in excess of NRC requirements increases the alpha-tocopherol concentration of muscle and improved color stability in lamb meat (Wulf et al., 1995; Cuidera et al., 1997; Turner et al., 2002). During a 6 day display period, semimembranosus steaks from lambs fed 300 IU of supplemental vitamin E per kg (136 IU per lb) for either 7 or 21 days had higher color readings than steaks from lambs fed 15 IU per kg (6.8 IU per lb) of supplemental vitamin E (Turner et al., 2002). Vitamin E also plays a role in controlling the color of veal calf meat. Combined feeding of monosodium phosphate and 100 IU of vitamin E per calf daily produced a light colored veal without making calves anemic (Agboola et al., 1990).
Vitamin E may have an additional effect on meat quality related to tenderness. Intramuscular collagen is responsible for the background toughness in cattle. Vitamins E and C may increase collagen turnover, but handling of cattle may reduce vitamin concentrations in muscles, impeding the removal of reactive oxygen species (ROS) and leading to oxidative stress. Collagen turnover was increased by vitamins E and C, with a higher rate of turnover increasing meat tenderness (Aranda-Osorio et al., 2010; Archile et al., 2010). Providing vitamin E at pharmacological levels (i.e., >1,000 IU per animal per day) to stressed, newly received feedlot cattle was beneficial for decreasing bovine respiratory disease (Duff and Galyean, 2007).
Feeding supplemental vitamin E at levels of 1,000 to 2,000 mg of naturally occurring mixed tocopherols per cow per day increased the vitamin E content of milk and its stability against oxidized flavor (Neilsen et al., 1953). The increased oxidative deterioration of milk produced from cows fed red clover silage was avoided by vitamin E supplementation (Al-Mabruk et al., 2004). The vitamin E content of milk from cows fed stored feeds was lower than that of milk from cows on pasture and their milk was more susceptible to development of oxidized flavor. Feeding supplemental vitamin E asdl-alpha-tocopheryl acetate, providing an equivalent of 500 mg of dl-alpha-tocopherol per cow per day, increased the vitamin E content and oxidative stability of milk (Dunkley et al., 1967). Nicholson et al. (1991) suggest that adequate selenium improves the transfer of dietary tocopherol to milk.
Supplemental levels of vitamin E higher than recommended for dairy cattle NRC (2001) have been beneficial in the control of mastitis. Smith and Conrad (1987) reported that intramammary infection was reduced 42.2% in vitamin E-selenium supplemented versus unsupplemented controls. The duration of all intramammary infections in lactation was reduced 40% to 50% in supplemented heifers. Weiss et al. (1990) reported that clinical mastitis was negatively related to plasma vitamin E and selenium concentrations in the diet.
The ability of vitamin E to affect growth, health and reproduction of animals is documented. Vitamin E supplementation program utilizing both parenteral and oral administration is often suggested, particularly when fresh green pasture is lacking. Mahan (1991) assessed the influence of low supplemental vitamin E (<16 IU/kg) to sows and offspring in three parities. Small litter size, sow agalactia and pig mortality during the first week after birth resulted from inadequate supplemental E to breeding sows. Chicks fed a diet containing 100 IU per kg vitamin E (45.5 IU per lb) had increased weight gains and reduced mortality during a coccidiosis challenge (Colnago et al., 1984). Large doses of vitamin E protected chicks and poults against Escherichia coli with increased phagocytosis and antibody production (Tengerdy and Brown, 1977). In studies, vitamin E supplementation of the feed, at levels of 150 to 300 IU per kg (68 to 136 IU per lb) decreased chick mortality due to E. coli challenge from 40% in the birds not supplemented with vitamin E, to 5% in supplemented birds (Tengerdy and Nockels, 1975; Nockels, 1979).
Exercise has an influence in vitamin E requirements and needed supplementation (Valberg et al., 1993). For horses, dietary levels of vitamin E greater than the 80 IU per kg (36.4 mg per lb) dry matter, and potentially approaching 300 IU per kg (136.4 mg per lb) dry matter, are required to maintain blood and muscle vitamin E concentrations in horses undergoing exercise conditioning. The level of vitamin E recommended by the NRC for working horses, 80 IU per kg (36.4 mg per lb) dry matter, will not maintain serum vitamin E levels.
The need for supplementation of vitamin E is dependent on the requirement of individual species, conditions of production and the total available vitamin E in food or feed sources. The primary factors that influence the need for supplementation include (1) vitamin E- and/or selenium-deficient concentrates and roughages; (2) excessively dry ranges or pastures for grazing livestock; (3) confinement feeding where vitamin E-rich forages are not included or only forages of poor quality are provided; (4) diets that contain predominantly non-alpha-tocopherols and thereby are less biologically active; (5) diets that include ingredients that increase vitamin E requirements (e.g., unsaturated fats, waters high in nitrates); (6) harvesting, drying or storage conditions of feeds that result in destruction of vitamin E and/or selenium; (7) accelerated rates of gain, production and feed efficiency that increase metabolic demands for vitamin E; and (8) intensified production that also indirectly increases vitamin E needs of animals by elevating stress, which often increases susceptibility to various diseases (McDowell and Williams, 1991; McDowell, 1992, 2000). After stress, livestock may have reductions in alpha-tocopherol concentrations in certain tissues. Supplemental vitamin E may be required after stress to restore alpha-tocopherol in tissues (Nockels et al., 1996).
Fortification of the ration with optimum levels of vitamins is the surest way to provide optimum vitamin nutrition for animals. This minimizes the variability, uncertainty and/or inadequacy created by the influencing factors. Of the major food-producing companion animals, only fish and guinea pigs require vitamin C. However, for some species (e.g., poultry and swine) vitamin C would be warranted under certain stress conditions. The dietary vitamin fortification levels should be reviewed and/or adjusted periodically to compensate for the influencing factors and allow optimum response. Supplementation allowances need to be adjusted to levels that reflect different management systems. They must be high enough to compensate for the effects of fluctuations in environmental temperatures, energy content of feed, or other factors that might influence feed consumption or the vitamin requirements in other ways.
A summary of the importance of providing optimum vitamin nutrition is as follows:
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