The swine industry today continues to undergo dynamic changes in efforts to improve profitability and the quality of pork production.
The swine industry today continues to undergo dynamic changes in efforts to improve profitability and the quality of pork production. Feed accounts for 60% to 70% of the total cost of swine production. Vitamin fortification constitutes 3% of the total cost of feed. Although vitamins are required in minute amounts (approximately 0.08% of feed weight), they are extremely important and are involved in approximately 100% of the biological functions in the body. Vitamins regulate biochemical reactions by which energy and protein sources in the diet are used for health, growth, feed conversion, meat quality and reproduction. Therefore, it is counterproductive and wasteful to feed an expensive high-energy diet with high-quality protein ingredients but marginal levels of vitamins. Intensified production for improved weight gains, feed efficiency or reproductive performance can increase the metabolic demand for many vitamins. Moving swine operations into complete confinement without access to pasture has also had a profound effect on vitamin nutrition (as well as mineral nutrition). Previously, pasture or range rearing could be depended upon to provide significant quantities of most vitamins. Young, lush, green grasses or legumes are good vitamin sources. More available forms of vitamins A and E are present in pastures, with green forages containing ample quantities of β-carotene and α-tocopherol versus less bioavailable forms in grains. Confinement rearing on slatted floors also eliminates the pig’s access to feces, which is rich in many vitamins. Confinement rearing requires producers to pay more attention to the higher vitamin requirements needed for this management system (Cunha, 1987). Today, clinical deficiency signs and disorders in swine are very rarely observed compared to several decades ago, primarily because of widespread vitamin fortification. However, the continuous changes in swine production necessitate the reevaluation of the proper vitamin fortification required to maximize swine performance. Trends in swine production include raising pigs in state-of-the-art facilities, weaning pigs at earlier ages, raising pigs that have a higher capacity for lean growth and maintaining high health status. These changes have greatly enhanced swine production as evidenced by advances in reproduction (number of pigs born alive), growth rates (lean tissue accretion) and feed efficiency, thought impossible several decades ago.
However, these developments have also put more pressure on the nutritional formulation of the diet and mandated that all nutrients be supplied in proper proportion. For example, the change to high lean growth pigs has increased the vitamin fortification required for maximum performance (Stahly et al., 1995). Likewise, the health status or antigen exposure of swine influences the required vitamin supplementation (Stahly and Cook, 1996; Stahly et al., 1997; 2007). In addition, due to weaning pigs at early ages and reducing the amount of milk consumed prior to weaning, several vitamins (vitamin C, pyridoxine and carnitine) previously thought by some nutritionists not to be required have now been demonstrated to be necessary for maximum piglet performance (De Rodas et al., 1998; Woodworth et al., 1997). The adequacy of NRC requirements for vitamins have come into question. For example, the B-vitamin requirements for the current NRC (1998) were not changed from the previous NRC publication that was published 10 years earlier. Because of changes in industry practices during the last 20 to 50 years, vitamin requirements for swine now are potentially greater. The B-vitamin requirements were established in experimental conditions with pigs of good health status and frequently with semipurified diets. Most studies were also conducted during an era when lean gains and growth rates were below those of the modern pig. Because of various factors affecting vitamin requirements, many professional nutritionists have increased their dietary B-vitamin recommendations for swine above the NRC (1998) requirement levels.
Studies have suggested that NRC (1988) levels of one or more of the commonly supplemented B-vitamins (riboflavin, niacin, pantothenic acid, and vitamin B12) are inadequate for maximal performance of newly weaned pigs (Wilson et al., 1991a,b; 1992; 1993; Antipatis and Litta, 2003) or high-lean growing pigs (Stahly et al., 2007). Indeed, additions of these B-vitamins at levels of two to ten times the estimated requirements have tended to improve growth rate and, or feed efficiency of pigs. However, it is not known what level above those suggested by the 1988 NRC may be needed and it is not possible to establish revised estimates of requirements for individual B-vitamins. On the contrary, Mahan et al. (2007) evaluated the effects of supplemental B-vitamins at the NRC (1998) requirement and beyond in practical swine diets in various parts of the country. The results demonstrated that supplementation of B-vitamins at the 100% total NRC levels for starter and grower pigs, from weaning to 85 kg (187 lb) bodyweight, was sufficient to meet their needs. These studies did not, however, consider the indigenous contributions of B-vitamins from various feed sources.
Higher supplementation levels than NRC requirements are also needed for vitamins A, D, E and vitamin K (McDowell, 2000). Vitamins A, D and E are required for an optimum immune response. Higher requirements of vitamin D are needed for maximum bone strength. Higher levels of vitamin E are needed for better meat quality. More vitamin K is needed now, than in previous years, as feed sources are different (elimination of green leafy plants) and bacterial synthesis is reduced due to vitamin antagonists in feeds or treatments with antibiotics.
Higher vitamin fortification has been reported to influence the lean tissue accretion possible with modern genetics (Lindemann et al., 1999). Modern genetic strains of pigs have a greater capacity for body growth, particularly proteinaceous (lean) tissue accretion. Furthermore, use of management techniques such as all-in-all-out production and segregated weaning schemes minimize the level of immune system activation the pig experiences, which further increases the animal’s capacity for body protein accretion (Williams et al., 1997; Stahly et al., 2007). These low immune status pigs from high lean strains can deposit 12 to 18 gm of protein per unit of metabolic bodyweight (BW0.75) daily, compared with 4 to 9 gm for fat and lean genetic strains experiencing moderate to highly stimulated immune systems that were evaluated during the 1950s through the 1970s. Assuming the vitamin needs per unit of body protein accretion are relatively constant, Stahly et al., 2007 hypothesized that pigs with high capacities for lean tissue growth would require 2 to 4 times the daily B-vitamin needs currently defined by the NRC (1998). Stahly et al. (2007) compared dietary B-vitamin needs of strains of pigs with high and moderate lean growth, supplemented with an additional 0 to 400% of NRC requirements. Pigs from the high lean strain consumed less feed and gained bodyweight faster and more efficiently than pigs of the moderate lean strain. In both lean strains, the rate and efficiency of growth were improved as dietary B-vitamin concentrations were increased. However, the dietary B-vitamin concentrations needed to optimize feed efficiency were greater in the high (>470% of NRC, 1998) vs. moderate (270%) lean strain. Based on these data, the dietary needs for one or more of the five B-vitamins are greater than current NRC (1998) estimates, particularly in pigs expressing a high rate of lean tissue growth.
All four fat-soluble vitamins (A, D, E and K) are usually added as supplements to all swine diets. In addition, four B-vitamins (riboflavin, niacin, pantothenic acid and B12) are added to all swine diets. Sow diets are usually supplemented with rather high levels of three additional vitamins (biotin, choline and folic acid). Nursery pig diets often contain supplements of vitamin B6, biotin, choline and a stabilized form of vitamin C, and some nutritionists add choline to finishing pig diets. Recently, some studies show carnitine to have benefits as a supplemental vitamin (Rincker et al., 2003; Ramanau et al., 2008).
Knowledge of the nutritional requirements of swine continues to grow. There are still deficits in the knowledge of certain vitamin requirements for swine during various stages of their production cycles which, hopefully, will be filled by future research. Additional recent research studies have demonstrated the importance of vitamin fortification in swine diets, which will be discussed in more detail in the following chapters. (Table 1-1)
Re-evaluation of optimum vitamin fortification levels will continue to be warranted as the swine industry adopts new approaches in the future. A new concept of optimum vitamin nutrition is essential today. Its object is to develop a new standard for vitamin supplementation in the diet of swine, aimed not only at preventing the initial phases of some diseases, but also improving an animal’s productive growth rate. This will permit an improvement in the pig’s state of health and well-being, thus optimizing its productive potential at the same time as permitting the production of high-quality, nutritionally balanced foods. The ideal fortification levels for each vitamin will include limiting overfortification, but at the same time it will also be imperative to ensure that optimum vitamin levels are provided to maximize utilization of other dietary nutrients, resulting in superior performance.
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