Feeding strategies will be investigated at a number of participating locations to develop nutritional regimens that result in improved utilization of dietary nutrients with a concurrent reduction in excretion in nutrients of environmental concern. Much of the planned work focuses on improved P nutrition of livestock. Participating states include KY, VA, IA, GA, MN, and IN. Researchers in TN will investigate excretion of non-nutrient pollutants in manure. The shared results of each state’s efforts will be used by the project participants to establish priority areas of research and outreach on an annual basis and to develop collaborative strategies to accomplish goals.

Task 1 - Develop and evaluate strategies to reduce phosphorus excretion from livestock.
Task 2 - Evaluate and quantify excretion of non-nutrient pollutants from animal agriculture.

Experiments will be conducted in KY to assess the effects of feeding low-phytate corn and low-phytate soybean meal without and with added microbial phytase on the bioavailability of phosphorus in the corn and soybean meal and on phosphorus excretion from pigs and chickens. In the pig study, a low phosphorus dextrose-casein basal diet will be fed.  In addition, similar diets with graded levels of phosphorus from a highly available source, monocalcium phosphate, or graded levels of phosphorus from the two types of corn and soybean meal will be fed.  Another series of diets will include the two corn and soybean meal types with added microbial phytase.  Similar experiments will be conducted with chicks. In IN swine studies will focus on the efficacy of phytate-phosphorus utilization when wheat bran (containing appreciable amounts of phytase activity) is included in diets.  The additional fiber contribution from wheat bran is proposed to have secondary effects of odor reduction as well. Subsequent studies will assess phosphorus excretion when these two types of feedstuffs are used in practical corn-soybean meal diets.

IA and IN will investigate phytase alternatives, such as citric acid and 25-OH cholicalciferol for nonruminants. An 8-wk screening study will be conducted in IA to assess 11 dietary swine treatments that include 4 levels of non-phytate P with and without microbial phytase and/or citric acid and/or 25-OH cholicalciferol. Fecal and urine samples will be collected for P (total and phytate) analyses. Based on the results, a follow up study will assess the effects of the most promising treatment combinations on long term feeding. Weaned pigs will be fed dietary treatments to market weight. Retention of P and bone strength data will be collected. Optimal combinations of enzymes and additives will be developed for different combinations of feedstuffs (corn, soybean meal, wheat, barley, canola meal, etc.) with the GIT simulation assay.  In vivo studies with chicks and poults will be used to verify results. The contribution of intestinal phytase to phytate-P hydrolysis and P retention will be also be evaluated.  Nutritional and genetic factors contributing to intestinal phytase expression will be investigated in the broiler, turkey poult, and duckling. Studies are planned in IN to investigate the additive effects of microbial phytase, 25-hydroxycholecalciferol, and citric acid in diets for turkeys (similar in scope to swine trials being conducted in IA). An experiment will be conducted with turkey poults to determine the additive effects of plant and fungal phytase on the liberation and utilization of P from phytic acid. An experiment will be conducted to determine the optimal level of fungal mycelium from the commercial production of citric acid on the liberation and utilization of P from phytic acid in diets for turkey poults.  A final experiment will validate the extent of P sparing by the plant phytase and fungal mycelium when used alone and in combination with turkeys raised in floor pens from 0 to 18 weeks of age. Additional studies are planned in IN to look at effects of the current industry practice of feeding pharmacological doses of copper sulfate (broilers and turkeys) and zinc oxide (pigs) on the efficacy of commercial phytases.  Future studies in swine, broilers, and turkeys will focus on life-time mass balance of N, P, Ca, Zn, and Cu and implementing strategies to maximize their retention/minimize excretion.

Further processing of feed grains by removing the germ from the seed through dry milling has been used commercially for subsequent extraction of corn oil from the germ.  As the phytate-phosphorus content of corn is primarily within the germ, the phosphorus content of the degermed-debranned corn (DDCORN) is greatly reduced as compared with normal corn.  Studies in IN will evaluate the effects of feeding DDCORN to broiler chicks on phosphorus excretion and solubility when compared to normal corn and other feeding strategies to reduce litter phosphorus.  If sufficient DDCORN can be obtained, subsequent swine, dairy and beef cattle studies will be conducted.  As the DDCORN ingredient contains significantly less phytate phosphorus, expectations are that the total and soluble phosphorus content of litter from birds fed this treatment will be much lower than those fed the other diets.

Studies will be conducted in MN to determine the long term effects of feeding low inorganic phosphorus and low protein diets with a source of non-starch polysaccharide with enzyme cocktails on the performance of sows over multiple parities. Digestibility studies will be conducted during gestation and lactation to determine nutrient utilization. The impact of the feeding regimens on the performance of pigs weaned from the experimental sows will be evaluated. The characteristics of manure from both the sows and the weaned to finished pigs will be determined. This is a collaborative study with the Departments of Animal Science Biosystems and Ag. Engineering, Microbiology and Soil, Water and Climate. In conjunction with these studies, researchers in GA are looking at amino acid and phytase diets for sows. In addition to P, they are also investigating methods for reducing the Cu and Zn excretion of nursery and grow-finish pigs.

Strategies for beef cows will be explored by a number of states with VA and IN leading the efforts. In VA, experiments will be with steers fed high roughage diets to gain 0.5 to 0.75 kg/day in individual stalls in dry lot.  In the initial experiment, three levels of P and two levels of available energy will be fed.  The cattle will be weighed at 2-wk intervals, and blood P will be determined at 4-wk intervals. A metabolism trial will be conducted with lambs to compare organic and inorganic P utilization in ruminants, compare utilization of different organic P sources, and determine the efficacy of phytase supplementation to ruminants fed organic P.    Criteria to evaluate the efficiency of P utilization will include P balance, blood serum P, bone ash and bone breaking strength. Beef steers will be used in IN to determine the benefits of using highly available phosphorus soybeans (HAPSM)/normal corn (C); highly available phosphorus corn (HAPC)/normal soybean meal (SBM); HAPSM/HAPC compared to the control normal SBM/C.  Nutrient balance trials will be used to determine manure volume, nutrient retention, and nutrient excretion of N and P.

Efforts to reduce P excretion from dairy cows will be led by IA and IN. In IA, ruminal phytase activity in transition dairy cows will be assessed using in vitro procedures and commercial diets with and without additional phytate P. Supplementation with microbial phytase will also be investigated. Phytase activity of high producing dairy cows with high rates of passage will be investigated in IA by using cows with post-ruminal and post-intestinal canulas. Similarly, in IN six ruminaly cannulated lactating cows will be used to determine the extent of rumen phosphorus availability of feeds commonly fed to dairy cattle in the mid-west US, the effect of phytase feeding on phosphorus release from feeds in the rumen and the potential of phytase to release P from postruminal digesta.

Hormonal pollution of the environment, by compounds such as the potent 17beta-estradiol (17BE), has been implicated in human and wildlife health problems. However, little is known regarding the environmental impact of hormones of animal origin. Such knowledge is timely, since current animal waste regulations are driven solely by concerns about nutrients (notably P and N), pathogens, and organic matter, with no consideration given to the impact of these regulations on environmental estrogen loads. Previous work examining livestock 17BE discharges have focused on poultry waste; little has been reported regarding the potentially large environmental loadings of estrogen from dairy and swine operations. To address this gap in knowledge, researchers in TN will pursue the following four objectives:

First, quantify the conservation of estrogens 17beta-estradiol and estrone in full-scale dairy waste storage systems. Specifically, compare lagoons and dry-stacks for their ability to conserve applied estrogen loads. Second, measure 17beta-estradiol and estrone concentrations in runoff and leachate from plots fertilized with liquid dairy wastes. Third, determine the efficacy of high-rate anaerobic digestion for degrading 17beta-estradiol and estrone. Fourth, determine the fate of 17BE in dry stacks, lagoons, high-rate anaerobic digesters, and soil. Specifically, use radiolabeled 17beta-estradiol  in lab studies to establish the extent to which microbes in these systems can mineralize 17beta-estradiol.

Because of increasing concerns about pathogens in animal waste, scientists in TN will evaluate the occurrence of Listeria spp., Salmonella spp. and E. coli O157:H7 in a dairy farm animal waste operation, and in a stream adjacent to the production facility over a six month period. Preliminary results show that feed grain, silage and bulk milk at the experiment site frequently tested positive for both Salmonella and Listeria, while Salmonella, Listeria and E. coli O157:H7 were isolated from the waste stream (separator liquid, separator solids, holding pond liquid), stream water 3 km upstream of the farm, and stream water 1 km downstream from the farm.  Pathogens are isolated and confirmed using FDA BAM protocols (enrichment). Preliminary results show that other sources impact stream quality even before the stream reaches the dairy farm, and that the potential cycling of pathogens through the production system must be carefully evaluated.