Up to five complex diets may be used in a phase-feeding program to accommodate the changing nutrient and ingredient requirements of fast-growing nursery pigs. Being expensive and prone to rapid quality deterioration, these diets require frequent mixing to ensure freshness and wholeness. Therefore, inputs such as logistics, storage capacity, and labor increase dramatically with a large number of diets.

Vitamin and trace mineral premixes can be omitted from diets of late-finishing pigs (200 lb to market) without any negative effect on growth performance, carcass characteristics, meat quality, or animal health (Tables 1 and 2). Finishing pigs may not require any supplemental vitamins and trace minerals from premixes because overfeeding of vitamins and trace minerals during growing results in substantial body stores that can be drawn upon to cover any deficits.

There are many factors that can potentially affect mammary gland growth. Estrogen and progesterone are known as essential hormonal factors for the growth of mammary glands during lactation. Insulin, cortisol, thyroid hormone, and prolactin also support mammary gland growth. Nutrient intake may also affect the growth of mammary glands. During gestation, dietary protein level does not affect mammary gland growth of gilts (Weldon et al., 1991; Kusina et al., 1999). However, excessive energy intake during gestation reduces mammary gland growth of gilts (Weldon et al., 1991).

Reduced reproductive performance is often associated with season of the year (Love et al., 1993), lactation length, and sow parity (Hurtgen and Leman, 1981; Koketsu and Dial, 1997; Koketsu et al., 1997), and is observed frequently throughout the world. The reduction in reproduction originates from reduced numbers of sows returning to estrus, increased time to return to estrus, higher returns to estrus after mating, which collectively result in lower farrowing rates.

Meat quality is affected by a number of factors such as environment, nutrition and genetics. The Halothane and RN genes impact animal performance, carcass composition and pork quality. The Halothane gene offers producers a rapid way of producing lean, heavily muscled market hogs that will receive higher packer premiums. However, Halothane reactor and carrier animals have poorer meat quality and processing characteristics, when compared to Halothane negative pigs. The meat quality problems associated with the Halothane gene result from a high incidence of the pale, soft, exudative (PSE) condition. Animals that carry the dominant allele of the Rendement Napole gene (RN-) have been found to produce paler meat with reduced water holding capacity and processing yields.

Modern pig housing systems are expensive to construct and operate. Historically, the number of pigs per pen (i.e. group size) and the floor area allowed per pig (i.e. stocking density) have been key factors in the design and use of pig houses. Historically, pigs typically have been penned from weaning to market weight in groups of 10 to 30 animals. Now, however, group sizes of 50 to 100 or even more are being advocated by some as a management strategy which is claimed to minimize housing cost, maximize housing use, and improve overall profitability.

Genetic improvement of sows has been significant during the past two decades. Modern sows are not only leaner and heavier at maturity but also produce larger litters. A simple comparison of 1979 British national data (MLC, 1979) with similar data (MLC, 1998) 20 years later reveals a three-pig per year increase in pigs weaned per sow per year.

Within hours after birth, pigs start to nurse the sow and teat order is quickly established (McBride, 1963; Wyeth and McBride, 1964; de Pasille et al., 1988). Sight, smell, and recognition of neighbors are factors which influence the identification of teats by new born pigs (McBride, 1963). Teat order helps to reduce the fighting frequency among littermates (Hartsock and Graves, 1976) and it is reported that teat order at the middle position is more slowly established (Fraser, 1975).

The digestibility of amino acids and other nutrients by the pig is an important measure of efficiency when evaluating swine diets or ingredients used in swine diets. Any method of feeding or use of a feed additive that significantly increases the ileal digestibility of amino acids could be used to increase the efficiency of amino acid use by the pig, and decrease waste and nutrient losses from swine production.

Animal agriculture is vitally important to the State of Illinois, both currently and in the future. Animal products provide high quality nutrition for humans and a large job base for Illinois citizens.

Sows with larger litters produce greater amounts of milk than sows with smaller litters. Sows with 12 pigs produced more than 50% more milk than sows with 6 pigs (King et al., 1989; King, 1991). This may result from an increased number of active mammary secretory cells, a crucial component of milk production as litter size increases (Tucker, 1966; Knight and Peaker, 1984; Knight et al., 1984).

The sow=s mammary gland is the sole organ for providing nutrients for nursing pigs. Understanding the biology of the sow=s mammary gland is critical for maximizing pig growth rate during lactation. It has been demonstrated that pre-weaning growth of pigs affects post-weaning growth (McConnell et al., 1987; Mahan and Lepine, 1991; Mahan, 1993). Thus, characterizing growth of mammary gland during lactation and understanding its relationship to the growth of nursing pigs may be important for improving pre-weaning growth of pigs.

Management is the key element that brings together genetics, facilities, and nutrition to achieve maximal performance in nursery pigs (3 to 25 kg of body weight). The ultimate goals of a any commercial nursery program should be to (1) maximize performance, in terms of growth and feed efficiency, and at the same time, (2) to minimize losses due to mortality and morbidity. Achievement of these goals requires a tremendous amount of resources during the delicate phase of postweaning growth.

Myostatin (GDF-8) is a member of the TGF-ƒÒ superfamily of growth factors which is expressed predominantly in skeletal muscle. Myostatin is a purported negative regulator of muscle development (McPherron et al., 1997).

Starvation and depressed postweaning appetite guarantee life-long poor growth rates, increased mortality and morbidity, and intensive management. Nursery pigs have a tremendous genetic potential for lean growth. However, low feed intakes allow them to achieve only 60 to 70% of it under most commercial conditions, mainly because feed intake determines growth.

Vaccination regimens for nursery pigs require that injections be given at a time that will ensure maximal development of immunity. Protection against pathogens is of paramount importance in pigs weaned at or before 3 weeks because at this age, passive (i.e., antibodies from sow’s milk) and active (i.e., antibodies produced by the pig itself) immunity are at their lowest points. Therefore, it is often recommended that the primary immunization be administered 1 to 2 weeks before weaning followed by a booster immunization 1 to 2 weeks after weaning.

Complex diets are loaded with lysine and reducing sugars that can combine together and become worthless for pigs. Besides corn and soybean meal, major sources of lysine include animal plasma, whey, skim milk, fishmeal, and crystalline lysine. Lactose, the main reducing sugar in nursery diets, is furnished by milk products, and crystalline lactose itself. The SEW, Phase 1, and Phase 2 diets are the most vulnerable diets.

The following is a brief summary of current projects underway and projects recently completed.

Swine research in the Department of Animal Sciences.

The digestibility of nutrients by the pig is an important measure of efficiency when evaluating swine diets or ingredients used in swine diets. Any method of feeding or feed additive that significantly increases the digestibility of nutrients could be used to increase the efficiency of, and decrease waste and nutrient losses from, swine production.

Australian research has shown that including magnesium aspartate in the diet of pigs during the final five days of the finishing period before slaughter reduced the incidence of Pale, Soft, and Exudative (PSE) pork thus improving the color and water holding capacity of the pork (D=Souza et al., 1998). In a follow up study (D=Souza et al., 1999), magnesium sulfate and magnesium chloride were found to be as effective as magnesium aspartate in reducing both the incidence of PSE and muscle drip loss.

One of the most critical aspects of swine reproduction is embryonic development. Embryonic development is directly related to litter size which also indicates the reproductive performance of a sow or gilt. In pig reproduction, it is know that estrogen plays a major role in early embryonic development and maternal recognition of pregnancy.

Milk is the exclusive nutrient source for the neonate. Enhanced management practices and availability of highly selected sows have allowed for increased litter sizes. The ability of the sow to produce adequate milk for large litters is limiting to neonate growth and total pig production (Boyd & Kensinger, 1998). Many studies have focused on improving nutrition for the high-producing lactating sow to maximize sow productivity.