Low Crude Protein Reduces Manure Odor

Researchers at the University of Illinois evaluated the impact of different levels of crude protein (CP) on fecal odor in growing pigs. They found that fecal odor can be reduced by feeding reduced CP diets

Five typical corn-soybean meal diets were fed to five, 80-lb. barrows. The diets contained 12, 14, 16, 18 and 20% CP, which was adjusted by increasing or decreasing the levels of corn and soybean meal in the diets. Crystalline amino acids were included in order to maintain the ideal protein pattern.

The pigs were housed in metabolism crates in a Latin square design, which allows each pig to consume all of the diets throughout the experiment. Pigs were allowed four days to adapt to each diet and then total feces were collected for five days. Upon collection, feces were frozen until odor analysis.

The feces were thawed and mixed and then analyzed by a trained human odor panel. The 10-member panel consisted of non-smoking, non-pregnant women between the ages of 30 and 55 who were not taking medications.

The panel evaluated the following odor characteristics: manure/fecal, urine/ammonia, musty/wet hay, overall odor intensity, tolerability (for a 24-hour period) and offensiveness. A 15-point scale was used, with increased scored indicating fecal odor was worsening.

When the CP level increased from 12% to 16%, fecal odor scores increased for offensiveness, tolerability and overall intensity. However, when CP levels increased from 16% to 20%, odor scores for offensiveness, tolerability and overall intensity were similar to those from 12% and 14% CP diets.

Researchers: Jennifer Wubben, David M. Albin, Michelle Smiricky and Vince Gabert, University of Illinois. Phone Gabert at (217) 244-2870 or e-mail him at gabert@uiuc.edu.

High Levels of Zinc Oxide Increase Fecal Zinc Excretion

Researchers at the University of Kentucky have shown that high levels of supplemental zinc in nursery diets causes increases in fecal zinc (Zn) excretion.

Supplemental zinc oxide (ZnO) is often used to control diarrhea and promote growth in postweaning pigs. In this study, researchers examined the effect of this practice on waste management.

Eighteen barrows, averaging 16 lb. and 22 days of age, were used to evaluate three levels of supplemental Zn (0, 2,000 and 3,000 ppm) from ZnO on fecal excretion. All diets contained a basal level of 150 ppm zinc.

Pigs were fed complex phase I and phase II diets for the entire three-week study. Feed waste was collected daily, and feed intake and growth rate were determined weekly. Total fecal collection was performed for each weekly period.

There were no positive effects of zinc addition on growth rate. Pigs fed higher levels of zinc absorbed greater amounts of zinc, which was confirmed by liver mineral concentrations. The liver mineral concentrations also revealed a negative effect of the high zinc levels on absorption of other minerals, most notably copper.

Pigs fed the 2,000 and 3,000 ppm zinc diets excreted 14.1 and 21.7 times as much fecal zinc as the pigs fed the diet with a normal level of zinc supplementation. At the highest level of supplementation, the amount of zinc excreted just during this nursery period would exceed that of pigs fed a normal level of zinc during the entire grow-finish period.

In conclusion, researchers note that high zinc excretion suggests that the use of high levels of zinc supplementation should be restricted to as short a period as possible.

Researchers: Terry Meyer, Merlin Lindemann and Gary Cromwell, University of Kentucky. Phone Lindemann at (859) 257-7524, or e-mail him at mdlindl@pop.uky.edu.