Animal Nutrition and Phosphorus Excretion in Beef and Swine Wendy Powers Department of Animal Science Iowa State University

Opportunities Monogastrics –Phytase –Low phytate grains –Phytase enhancers and alternatives Ruminants –Wider array of feed ingredients –Moving towards better feel for requirements –Total P = Available P

Phytase effects on P excretion When used properly, as much as a 25% reduction in P excretion –Includes impact of reducing diet P to requirements –Smaller effect if not reducing diet P sufficiently –Smaller effect if already feeding a P needs No negative effects on soluble P excretion

Low-phytate grains HAP corn –Similar effect as with phytase –Additive effect when combined with phytase Low phytate soybeans –New research findings

Swine excretion and performance effects of low-phytate soybeans Quantify total and water-soluble excretion from swine fed low-phytate soybean meal alone and with supplementary phytase. Determine if feeding low-phytate soybean meal has any adverse effects on swine performance.

Materials and Methods Diets Four dietary treatments –Control soybeans, no phytase (NP – np) –Control soybeans, phytase (NP – p) –Low-phytate soybeans, no phytase (LP – np) –Low-phytate soybeans, phytase (LP – p) –Each contained 1% indigestible marker

Materials and Methods Pigs 96 pigs, allocated to 24 pens –Initial average BW = 18 kg 10-wk trial –Final average BW = 83 kg

Materials and Methods Individual pigs were weighed weekly Feed was offered daily and refusals were weighed weekly Individual fecal and urine samples collected weekly –Pooled by pen

Results Animal Performance No diet, phytase, or soybean effects on –ADG (0.98 kg) –ADFI (1.94 kg) –F:G (2.03)

Results Nutrient Retention No diet, phytase, or soybean effects on DM or OM retention (83.7%, 86.5%, respectively) P retention –Greater in low-phytate soybean diets 49.1% vs. 42.3% –Greater in diets with phytase 47.3% vs. 44.1%

Results Phosphorus Excretion TP, g per kgWSP, g per kg WSP, % of TP NP - np NP - p LP - np LP - p

Results Phosphorus Excretion TP, g per kgWSP, g per kgWSP, % of TP Control soybeans 19.0 a 10.5 a 0.56 Low-phytate soybeans 15.3 b (-19.5%) 8.7 b (-17%) 0.57 Phytase added 15.9 a (-14%) 9.3 a (-6%) 0.59 a No phytase18.4 b 9.9 b 0.55 b

Conclusions Low-phytate soybeans resulted in reduced mass of TP and WSP excreted Including phytase in the diets, yielded an even further reduction in TP and WSP

Implications Assuming fecal masses do not differ by diet…. Assuming no diet effects in fecal P when pigs > 180 lb…. Assuming fecal production is uniform over the grow-finish phase…. Low-phytate soybeans resulted in a 12% reduction in TP excretion over the grow-finish phase

P Intake, Retention and Excretion 12.2 g 26 g 13.8 g 12.2g 6.38 lb bird 1.93 feed to gain 49 days of age RA0109 exp results 36.2g P 17.1g P Agristats, 1999 (control) Industry+Phy 30.8g P 13.8 g P 19.3 % 17.0g P

P Intake, Retention and Excretion 12.2 g 26 g 13.8 g 12.2g 6.38 lb bird 1.93 feed to gain 49 days of age RA0109 exp results 36.2g P 17.1g P Agristats, 1999 (control) UMD Rcmd 31.7g P 14.8 g P 22.5 % 16.9g P

P Intake, Retention and Excretion 12.2 g 26 g 13.8 g 12.2g 6.38 lb bird 1.93 feed to gain 49 days of age RA0109 exp results 36.2g P 17.1g P Agristats, 1999 (control) UMD Rcmd+Phy 28.8g P 11.9 g P 30.5 % 16.9g P

P Intake, Retention and Excretion 12.2 g 26 g 13.8 g 12.2g 6.38 lb bird 1.93 feed to gain 49 days of age RA0109 exp results 36.2g P 17.1g P Agristats, 1999 (control) UMD Rcmd+Phy+25OHD3 26.8g P 10.0 g P 41.5 % 16.8g P

Citric acid improving phytate- P utilization CA alone –  phytate degradation from 42% to 69% in whole wheat flour during bread baking CA + exogenous phytase -  phytate degradation up to 85% CA alone, CA + phytase, CA + phytase + ascorbic acid  iron dialyzability 12-, 15-, and 24-fold, respectively Porres et al., J. Food Sci. 66(4):

Combined nPP Sparing Effect of Phytase, Citric Acid and 25-Hydroxycholecalciferol Angel et al., % 0.144% 0.147% SEM

Opportunities Monogastrics –Phytase –Low phytate grains –Phytase enhancers and alternatives Ruminants –Wider array of feed ingredients –Moving towards better feel for requirements –Total P = Available P

P content of various feeds Corn grain0.35Citrus pulp0.12 Barley0.39Brewer’s grains0.67 Wheat0.43Bakery waste0.36 Sorghum0.35Whole cottonseed0.60 Alfalfa hay0.30Fishmeal3.05 Corn silage0.26Urea0 SMB0.70Canola meal1.10 DDGs0.80Beet pulp0.09

Feedlot pen 7.2 lb intake 1.9 lb animal 5.3 lb excreted Summer-Yearlings 12.8 lb intake 1.9 lb animal 10.9 lb excreted.35 % P diet.24 % P diet REDUCED 44 % P Mass Balance (continued) Source: Erickson et al., 2000 REDUCED 52%

9.9 lb intake 2.4 lb animal 7.5 lb excreted Winter/spring-Calves 15.0 lb intake 2.5 lb animal 12.5 lb excreted P Mass Balance (continued) Source: Erickson et al., 2000 REDUCED 33 %.40 % P diet.26 % P diet Feedlot pen REDUCED 40%

Challenges Monogastrics –In vivo phytase efficacy is not 100% –Commercial availability of LP grains –Grain P > P needs –Pressure to feed DDGs Ruminants –Grain P > P needs –Pressure to feed DDGs

Challenges Soybean meal Corn

Dietary P in Feedlot Diets Req.

Phosphorus content of common byproduct feeds

Acreage Needs

Digestibility of byproduct feeds Creates a greater volume of manure Bierman et al., JAS

Critical to sample manure Diet impacts on P concentration Diet impacts on manure mass, independent of P content, but affects P concentration

Summary Slowly making nutritional headway towards reducing P excretion Opportunities continue to arise Still searching for the low P grains Endogenous losses prevent 0 P excretion –Feeding through the animal is an inefficient means of getting P to the land!