Weanling Pig Research

• Fatty acids. Studies are assessing omega-6:omega-3 fatty acid ratios on performance, immunological, blood, and tissue responses in young pigs.

• Brewers yeast as a source of mannan-oligosaccharides (MOS). Brewers yeast (Brewtec®, International Ingredients Corp.) was evaluated as a source on MOS as a possible alternative to antibiotics for pigs. Performance was not improved by adding brewers yeast or carbadox to unmedicated starter diets. In other experiments, the efficacy of brewers yeast in preventing colonization of pathogenic E. coli K-88 in the gut of pigs is being investigated.

• Ingredients in starter diets. Amino-Lac®, a product consisting of whey protein concentrate, meat protein isolate, and yeast protein (50% protein, 3.4% lysine) was comparable to dried animal plasma on a lysine basis and found to be equal in nutritional value.

• Zinc and antibiotics. We cooperated with NCR-42 in a study to evaluate the combination of high Zn (1,500 or 3,000 ppm, from Zn oxide) and carbadox on performance of weanling pigs. The combination of high Cu and carbadox was additive. Another NCR-42 study assessed Zn oxide (2,500 ppm Zn) and zinc methionine (250, 500, 750 ppm Zn). Zn oxide was more efficacious than the organic Zn form. In another study, 2000, and 3000 ppm added Zn from Zn oxide had markedly increased Zn excretion compared with a low-Zn control diet. High Zn had a slightly negative effect on P, Cu, and Fe absorption, as well as on liver Cu.

Growing-Finishing Pig Research

• Low-phytate corn. The mutant lpa1 gene substantially reduces the phytate content of corn without affecting the total P. Experiments conducted with chicks and pigs indicated that the P in low-phytate corn (Optimum Quality Grains/DuPont Specialty Grains) was 3-4 times as bioavailable as the P in a near-isogenic normal corn. Additional studies with growing and finishing pigs indicate that total dietary P can be reduced by 0.10 to 0.15 of a percentage unit when diets containing low-phytate corn are fed, which will reduce P excretion by 30-40%.

• Low-oligosaccharide, low-phytate soybean meal. Studies were conducted to assess the bioavailability on P in low-oligosaccharide, low-phytate soybean meal (DuPont Specialty Grains) and to assess its nutritional value when fed in combination with normal and low-phytate corn. The bioavailability of P in low-phytate soybean meal was 2-3 times higher than in normal soybean meal for both pigs and chicks. Growing pigs fed low-phytate corn and low-phytate soybean meal with no inorganic P supplementation had similar performance and bone strength as pigs fed conventional corn-soybean meal diets, and they excreted half as much P in their feces.

• Genetically modified soybean meal. Studies have been completed to assess soybean meal from Roundup Ready® vs isogenic control soybeans grown under the same environmental conditions. As expected, there were no differences in the performance or carcass traits of the pigs fed the two diets. Loins are being evaluated by taste panel. Tissues from these pigs are being evaluated for transmission of genetic material (DNA) and the specific protein that makes the soybean tolerant to herbicides.

• Bioavailability of phosphorus in meat byproducts. The P in meat and bone meal was found to be considerably higher (~90%) than previously observed. Ash content (beef [high ash] vs pork [low ash] origin) of meat and bone meal had a greater effect on P availability (beef>pork) than particle size or processing temperature, but none of these factors affected ileal digestibility of amino acids.

• Phytase. Phytase additions were evaluated in corn-soy diets with normal and low-phytate corn. Phytase was more effective in diets with normal corn. The effects of phytase (250, 500, 750 PTU/kg) on digestibility of amino acids, Ca, and P in soybean meal were assessed in ileal cannulated pigs. Apparent and true digestibility of Ca and P, but not amino acids were influenced by dietary phytase. In another study, formulation matrix replacement values for graded levels of phytase were assessed.

• Vitamin levels for pigs. A series of studies have examined the potential of extra vitamin supplementation to enhance performance of growing-finishing pigs. The increase of a standard vitamin supplement (that was devoid of certain vitamins and had various levels of other vitamins) did not improve growth or carcass response. Alternatively, graded levels of five B-vitamins when all other vitamins were present and when other nutrients were not lacking provided an improvement in growth, feed efficiency, and carcass leanness. The response peaked at supplementation levels above current NRC standards but the study design did not allow determination of which vitamin(s) were responsible.

• Betaine for finishing pigs. In several experiments, betaine supplementation improved performance and carcass leanness to a greater degree in finishing pigs fed a low energy, corn-soybean meal diet with 20% wheat middlings than in a corn-soybean meal diet. Betaine was also assessed in low protein, amino acid supplemented diets and in crowded pigs. Crowding (5 and 7 vs 9 sq. ft./pig markedly reduced pig performance, and betaine did not appear to offset this depression.

• Diet manipulation and manure gasses. Studies were conducted to assess diet manipulation (reduced protein + amino acids) and various dietary additives on NH₃ and H₂S emissions from manure in simulated anaerobic manure pits. Dietary protein reduction reduced NH₃ emissions and pH of the slurry. The additives reduced NH₃ to varying degrees. Studies are underway to assess H₂S emissions from manure of pigs fed low sulfur diets.

• Long-term antibiotic withdrawal. There is renewed interest in the antibiotic resistance area. We continue to periodically monitor resistance patterns of enteric flora in pigs from a herd that has not had any exposure to antibiotics for 25 years and a herd having continuous exposure to antibiotics.

Sow Research

• Chromium. A study examining the effects of Cr on immunocompetence in sows and their litters was conducted. Maternal serum and milk samples and pig serum samples were collected from about 35 litters. Four levels of Cr tripicolinate were supplemented in a cooperative study with five other universities to determine the potential for greater supplementation levels to increase the magnitude of response to Cr or to decrease the period of time required before a meaningful response is seen.

• Phytase. Gilts were used were used to assess fecal P excretion in late gestation as affected by dietary phytase additions.

• Enzymes. Sows have been surgically modified with ileal T-cannulae. A variety of assessments of digestibility, some involving enzymes, will be conducted during the coming year.