Optimum Vitamin Nutrition for Optimum Animal Health and Performance

In recent years, researchers have made significant advances in understanding the importance of vitamin adequacy to sound livestock and poultry nutrition. Work in all the major species has refined and expanded previous ideas about the role that specific vitamins play, and the opportunities to improve producers' profitability.

The Role of Vitamins in Nutrition

Influencing Factors

Although vitamins aren't the only nutrients being reconsidered in this new light, they offer a key example because they are so central to a balanced diet. Indeed, vitamins are involved in all the biological functions that allow an animal to use energy and protein for health, growth, feed conversion and reproduction. If one or more vitamins are deficient, no increase in the other nutrients will overcome the deficiency and permit those functions to occur.

What is still evolving is the definition of deficiencies. Today, it is widely recognized that deficiencies do not even have to approach clinical status before they compromise a producer's returns. Traditionally, however, deficiencies and adequacies have been determined by the presence or absence of very specific, clearly identified diseases or other clinical signs. Vitamin E adequacy would be measured by freedom from white muscle disease, for instance, and vitamin D adequacy by freedom from rickets. Dietary requirements would be defined as the lowest levels necessary to prevent these signs.

However, this approach is limiting, as most professionals involved in making nutritional decisions recognize. By defining adequacy simply as freedom from clinical deficiency signs, this approach sets its sights dangerously low. It can be likened to a producer who concentrates on a breakeven return when real profits are possible.

Research in vitamin E, for instance, has demonstrated links between this vitamin and the ability to mount an effective immune response. In fact, research has found that immunocompetence is impaired by low tissue levels of vitamin E well before clinical signs of deficiency appear. Thus, on a dairy farm, vitamin E adequacy might traditionally be judged by the levels that permit freedom from white muscle disease. The new approach would consider levels that permit a cow to mount a strong immune response to mastitis. Similar differences in approach would arise on other types of livestock operations.

Fortification Yields Better Performance

The NRC vitamin requirements are designed to prevent clinical deficiencies and provide acceptable performance. By contrast, the new approach to nutritional requirements wonders whether "acceptable performance" is good enough—especially given the cost of feed and the investments in better genetics and management that producers have made over the years.

Because vitamins are involved in all the biological functions that allow an animal to metabolize energy and protein, the new approach instead asks this question: What dietary levels of vitamins are necessary for optimum weight gains, feed efficiency and (or) reproductive performance?

Defining OVN

This change in thinking mirrors modern farm management to a large extent, since clinical unthriftiness is now rare, but less-than-optimum performance is not. For instance, recent swine studies found as much as a 40-to-1 return on investment through improved growth rate and feed efficiency when vitamin intake was optimized. Yet even the control pigs in the study did not exhibit clinically poor performance.

Optimum vitamin allowances will vary with the operation's production goals and also with other factors that influence the vitamin needs of animals under commercial production conditions. These include animal genetics, physiological makeup, nutritional and health status, stress levels, vitamin stability and bioavailability, feed management (including feeding practices) and environment.

Recommendations For Optimum Vitamin Nutrition

Optimum vitamin allowances will also contain margins of safety to make sure the animals' intake does indeed meet desired levels. This is an important, economical form of insurance.

For the key roles played in allowing the animal to utilize the other nutrients, vitamins account for less than 4 percent of the diet's cost. Skimping here quickly becomes a case of false economy as it risks or reduces the producer's return from the other 96 percent of the feed's cost. The danger is that marginal vitamin deficiencies may lessen economic returns silently, through unrecognized lost opportunity.

Just how quickly marginal vitamin allowances can reduce animal performance is apparent in the results of controlled studies. One study measured weight gains and feed efficiency in starter pigs receiving various dietary levels for five B vitamins: riboflavin, niacin, pantothenic acid, vitamin B12 and folic acid. All of these vitamins are closely associated with protein synthesis. Because this study used two genotypes of pigs, the researchers could also chart differences in live performance by vitamin intake for animals with different genetic potential, in this case for lean gain.

Pigs in the control group received a diet containing approximately 70 percent of the NRC requirements for the five vitamins. The other treatment groups received the basal diet fortified with the five vitamins at 100, 200, 300 or 400 percent of the NRC vitamin requirements.

In pigs with moderate lean growth potential, average daily gains continued to increase as the total vitamin intake rose to 470 percent of NRC requirements, and feed efficiency plateaued at the 270 percent level. The performance differences by vitamin intake were even more pronounced in pigs from the newer, high lean growth genotype. Again, rate of gain continued to increase as vitamin allowances rose to 470 percent of NRC requirements. Feed efficiency in these pigs also continued to improve to 470 percent of NRC requirements, and it did not plateau even at this level (Figure 1).

Figure 1
Feed Efficiency and B Vitamin Supplementation

In economic terms, the researchers calculated that the improved performance that came with optimizing vitamin allowances for the pigs returned over $40 for each dollar invested.

These results were especially noteworthy, the researchers said, because it has been suggested that stressed pigs would benefit most from increased vitamin supplementation. Yet, the pigs used in this study were healthy and raised in pristine circumstances.

In breeding stock and poultry, genetic improvements have prompted similar research. Today's sows, for example, have been bred to produce larger litters. In research on sow biotin allowances, numerous studies have reported improvements in pigs born alive, pigs weaned per litter and (or) weaning to estrus interval with biotin supplementation. A cooperative university study by researchers in Kentucky, Minnesota and Nebraska found that when sows received 300 mg per ton (0.33 ppm) of dietary supplemental biotin, they averaged 9.4 pigs per litter at 21 days, compared to 8.7 for unsupplemented sows.

Other studies of increased vitamin supplementation of sows have also shown significant results. Among them:

• Sows receiving 60,000 International Units (IU) of vitamin E per ton (66 IU/kg) of feed had more pigs born (12.27 vs. 11.85) and more pigs born live (11.60 vs. 11.45) than control sows that received the NRC requirement of 20,000 IU per ton (22 IU/kg).
• In 11 studies at southeastern universities, sows fed supplemental folic acid consistently produced larger litters than unsupplemented sows.

In the above studies, the benefits of optimum vitamin allowances were demonstrated in the fairly pristine conditions of university facilities. The issue becomes even more critical in commercial situations, where stress poses a much more significant threat to optimum performance.

Stress increases an animal's vitamin requirements in several ways. First, like anything else that reduces total feed intake, stress increases the vitamin concentrations needed per unit of feed to meet the animal's vitamin needs. In addition, stress shifts metabolic nutrient requirements and can make a theoretically adequate ration inadequate.

This danger arises both for those vitamins with clearly recognized dietary requirements and for those that the animals themselves synthesize. Researchers are asking whether the amounts synthesized actually meet the animals' requirements in times of stress.

For example, the NRC lists no dietary requirement for biotin in adult ruminants, because it assumes that the animals synthesize enough of this vitamin through gastrointestinal microbes. Biotin is particularly important in controlling the rate of production and deposition of "hard" proteins such as keratin, which is a component of skin, hair and horn. Research in both dairy and beef cattle has reported significant improvements in the hardness and tensile strength of hoof horn, and reduced incidence of the most common hoof disorders, in cows whose diets include biotin supplementation compared to unsupplemented cows.

Work at The Ohio State University in 1997 found that white line separation in the rear lateral hoof was reduced to 10 percent of dairy cows receiving dietary supplemental biotin, compared to 27 percent of unsupplemented cows. Supplementation consisted of 20 mg per head per day. In the rear medial hoof, white line separation occurred in 20 percent of the unsupplemented cows but in only 2 percent of the supplemented animals. Similarly, a significant improvement in claw parameters in direct proportion to increased plasma biotin levels is shown when the cows received dietary supplementation of the vitamin at 20 mg per day. These cows had from 20 to 37 percent lower incidence of interdigital dermatitis than unsupplemented controls.

Dairy research at Ohio State has also shown increased milk production in biotin-supplemented cows, compared to unsupplemented herd mates. This difference averaged 2.7 percent more milk and 4.3 to 4.7 percent more milk was observed in a 1996 Roche study.

Across species, much of the recent research into stress and vitamin requirements has focused on vitamins E and C. Both are antioxidants that protect the cell from damage by radical oxygen molecules (ROMs) and other highly destructive by-products of metabolism. The production of these destructive molecules increases with physiological changes during stress, and thus there's a greater need for the quenching ability of these vitamins—vitamin E in the lipid portions of the cell and vitamin C in the aqueous portions.

In studies with incoming feedlot cattle (Table 1), the value of vitamin E supplementation appeared to increase as the level of stress increased. Yet, even when cattle faced less stress and disease pressure than is common in commercial situations, significant improvements, including a 13 percent increase in average daily gain, in cattle that received vitamin E supplementation have been reported.

Vitamin C requirements during stressful periods present a special case because this is one of the vitamins that livestock and poultry synthesize. In addition, early research into vitamin C supplementation was hampered by the highly unstable nature of the vitamin. But with the development of stabilized products such as Stay-C®, in which the vitamin is protected from oxidation by phosphate groups attached to the ascorbic acid molecule, results have been more consistent.

In a study with broilers, researchers fortifed diets with 0, 150 or 300 ppm of supplemental vitamin C and then measured performance when the birds were subjected to combinations of heat, beak trimming and (or) coccidiosis. In general, live performance declined linearly as the number of stressors increased. However, supplemented birds performed significantly better than unsupplemented birds at any given level of stress.

The feed intake of the birds receiving either 150 or 300 ppm was about 23 percent greater than for the unsupplemented birds when all three stressors were present (Figure 2). In fact, birds receiving either level of vitamin C supplementation ate as much feed when exposed to the three stressors as unsupplemented birds ate when exposed to none. Weight gains also clearly favored supplementation, and as the number of stressors increased, so did the differences in weight gain between treatment groups.

Figure 2
Feed Intake of Chicks Exposed to Multiple Concurrent Stressors

Whether or not animals undergo significant stress with its various immunosuppressive effects, vitamin adequacy plays a key role in the ability to mount an effective response to disease. Today, vitamin E offers the clearest example of vitamin adequacy being expanded in the light of maximizing an animal's resistance to disease. Indeed, studies have shown reduced immunocompetence with low tissue levels of vitamin E well before any clinical signs of vitamin E deficiency occur.

Researchers have reported significant responses with increased vitamin E fortification to health problems ranging from scours in baby calves and mastitis-metritis-agalactia (MMA) in sows to E. coli mortality in broilers.

The Problem with Estimating Vitamin Content in Feedstuffs

In the dairy industry, work at The Ohio State University reported an 80 percent reduction in early lactation mastitis, compared to the control group, in animals receiving a high level of dietary vitamin E supplementation (Figure 3). This regimen included 1,000 IU of vitamin E per head daily for the first 46 days of the dry period, 4,000 IU daily for the last 14 days of the dry period and 2,000 IU per head daily during the first 30 days of lactation. The control cows received 100 IU of Vitamin E per head daily during the 60-day dry period and first 30 days of lactation.

The increases in intramammary infection and mastitis that commonly occur around calving coincide with the lowest plasma concentrations of vitamin E. Along with the marked decrease in mastitis incidence, plasma vitamin E levels remained at precalving levels in the cows receiving the highest level of supplementation.

Figure 3
Effect of Dietary Vitamin E Supplementation on Incidence of Mastitis

A third treatment group received 1,000 IU of vitamin E per head daily during the 60-day dry period and 500 IU per head daily during the first 30 days of lactation. The incidence of clinical mastitis in this group was about 30 percent lower than in the control cows. This intermediate supplementation level was used in most of the previous Ohio State studies on vitamin E, and the reductions in mastitis incidence were similar in those studies.