Determination of Ammonia Emission and Urine pH as Affected by Different Dietary Sources of Calcium and-or Phosphorus in Grow-Finish Pigs

North Carolina State University Swine Nutrient Management Research from 2001. The objective of this study was to investigate the effect of different sources of calcium and phosphorus in swine diets on urine pH and ammonia emission. Experiment 1 evaluated the impact of acidogenic calcium and phosphorus sources on urine pH. In Exp. 2, the effect of acidogenic calcium and phosphorus sources on in vivo ammonia emission were determined. In Exp. 1, urine pH was decreased (P<.05) in animals consuming diets containing phosphoric acid+calcium sulfate (PA) and monocalcium phosphate+calcium sulfate (MCP). In Exp. 2, the ammonia concentration (NH3), ammonia emission per feed intake (NH3/FI), and ammonia emission per nitrogen uptake (NH3/NI) were significantly decreased in the pigs fed the phosphoric acid+calcium sulfate grower diet (PA-G) compared with the control diet. The ammonia reduction percentages of PA-G diet were 27.7, 30.6, and 30.4%, respectively. The phosphoric acid+calcium sulfate finishing diet (PA-F) decreased NH3 concentration only (25.3%, P=.06) as feed intake was decreased with this treatment. Also, the combination of calcium sources (50% CaCO₃ + 50% CaCl₂) with monocalcium phosphate (MCPCl) diet led to a decreased NH3 (18.8%, P=.07), NH3/FI (16.1%, P=.07), and NH3/NI (15.7%, P=.07) emission. It is concluded that diet manipulation of acidogenic agents can reduce ammonia emission from swine manure.

 

Introduction

 

Ammonia emission from the swine industry should be reduced to prevent water and air pollution (Apsimon and Kruse-Plass, 1991) and to reduce possible health problems with humans working with hogs or living in the vicinity of hog facilities (Schiffman, 1998). The major source of ammonia emission is urea excreted with urine. This urea is converted into ammonia and carbon dioxide by the urease present in feces (Stevens et al., 1989). Diet manipulation could be a candidate solution for reducing ammonia emission from swine manure (van Kempen and van Heugten, 1998).

 

Acidogenic agents in the diet could reduce urine pH due to the renal regulation of acidbase balance. Low urine pH can trap ammonia in the manure in the form of ammonium salts rather than gaseous ammonia, thus preventing ammonia emission. In this study, the effect of different sources of calcium and phosphorus, which were the acidogenic agents in the swine diet, on ammonia emission from pigs was investigated.

 

Materials and Methods

 

General: The North Carolina State University Institutional Animal Care and Use Committee approved all experimental procedures, care, and handling of animals.

 

Experiment 1: A total of eight crossbred finishing barrows (initial BW 67 kg) were used to test four diets using a Latin square design. The diets tested were as indicated in Table 1. The pigs were housed in individual pens and received water ad libitum. Feed was provided twice per day and the amount was 80 g per kg metabolic body weight (BW.75). Urine samples were collected on Day 6 and 7 following a 5-day adaptation for determination of urine pH using a standard pH electrode.

 

Experiment 2: A total of six trials were conducted in two environmental chambers. In each trial the effect of an acidogenic agent on ammonia emission was compared with that observed on a control diet (Table 2). Chambers used were 7 × 9 × 8 ft and contained a pig pen (7 × 8 feet) that housed 10 pigs and which was positioned above a pit designed for pit-recharge. Manure was stored in this pit for a one-week period, after which the pit was emptied and filled with approximately 2” of water. Feed and water were provided ad libitum and intake was recorded. Each chamber was equipped with a ventilation system connected to a dehumidifying air conditioners (Thermoster, Madison, WI) at the air inlet, an exhaust fan, and an air flow meter using ultrasound speed measurements (Panametrics, Waltham, MA). Air samples were taken from air inlets (for background corrections) and outlets semi-continuously for a 3.75 minutes period every 15 minutes. Sampled air was subsequently pulled through an 84-meter gas cell (Gemini, Anaheim, CA) connected to a Magna 760 Fourier Transform Infrared (FTIR) Spectrometer (Nicolet, Madison, WI). Using the FTIR ammonia was quantified in both inlet and exhaust air by determining the peak area at 909 cm-1. The experimental period consisted of a one-week adaptation period followed by a one-week data collection period. During the data collection period, the ammonia emission data were collected on days 2, 4, and 6 for 24 h each day.

 

Experimental Design: Experiment 1 was conducted as a Complete Latin Square design (CLSD) and experiment 2 was by Cross-Over design. Data were analyzed using the GLM procedure of SAS (1998).

 

Results and Discussion

 

There were no problems in animal health in experiment 1. In experiment 2, mild diarrhea was occasionally observed in animals on diets with calcium sulfate. In Exp. 1, urine pH was decreased (P<.05) in animals consuming diets containing phosphoric acid+calcium sulfate (PA) and monocalcium phosphate+calcium sulfate (MCP) compared to urine pH from animals receiving the control diet (Figure 1). However, the hydrochloride diet (HCl) had a lower diet pH than others (Table 1), but the urine pH was not affected by HCl addition in the diet.

 

Table 1. Composition of diets as used in Exp. 1. (%)

 

Based on the results of Exp. 1, a series of environmental chamber trials were performed in Exp. 2 for the determination of ammonia emission as affected by the different dietary calcium and phosphorus sources (Table 2). In trial 2, the pigs fed the phosphoric acid+calcium sulfate (PA-G) diet had significantly decreased ammonia concentration (NH3), ammonia emission per feed intake (NH3/FI), and ammonia emission per nitrogen uptake (NH3/NI) compared to the control diet (P<.05, P<.01, and P<.01, respectively; Figure 2).

 

Table 2. The list of treatments and starting BW in Exp. 2.

 

The ammonia reduction percentages of PA-G diet were 27.7, 30.6, and 30.4%, respectively. The phosphoric acid+calcium sulfate finishing (PA-F) diet decreased NH3 concentration 25.3% (P=.06). Also, the monocalcium phosphate+Ca combination (MCPCl) diet decreased NH3 (18.8%, P=.07), NH3/FI (16.1%, P=.07), and NH3/NI (15.7%, P=.07) emission. But, other treatments (CS, PACp, and MCP) did not affect ammonia emission (P>.05). Monocalcium phosphate was the most potent acidogenic agent based on result of Exp. 1, but in trial 5, the MCP diet did not affect ammonia emission. It could be the effect of excess calcium sulfate (excess SO4 2- ion), which reduced the dEB too much with negative consequences for animal health. Also, calcium sulfate may have induced adverse effects on nutrient availability due to the abnormal ion balance in the intestine. The combination of calcium sources (50% CaCO₃ + 50% CaCl₂) with monocalcium phosphate did reduce the ammonia emission (P<.08). This calcium combination likely did not have the negative effects on dEB and therefore did not negative the effects of monocalcium phosphate on urine pH.

 

Implications

 

The ammonia emission from swine slurry (urine and feces mixture) depends on slurry pH (Stevens et al., 1989). As most of the ammonia emission stems from manure coating slats rather than manure in the slurry storage, addition of acid to the manure in storage is expected to only moderately reduce ammonia emission. As an alternative, dietary modifications can be used for reducing urine pH. Phosphoric acid and monocalcium phosphate both were effective in reducing urine pH and both, when fed with suitable calcium sources, result in lowered ammonia emission (30 and 16%, respectively). A major dilemma remaining is the calcium source to use; limestone increases urine pH, in contrast to gypsum or calcium chloride. The latter two, however, may negatively affect the dietary electrolyte balance and thus gut and animal health. The urine pH was decreased in pigs consuming diets containing phosphoric acid and monocalcium phosphate. Also, phosphoric acid and monocalcium phosphate as the role of acidogenic agents can reduce ammonia emission 30 and 16%, respectively.

 

Literature Cited

 
Apsimon, H.M., and M. Kruse-Plass. 1991. The role of ammonia as an atmospheric pollutant. In: V.C. Nielson, J.H. Voorburg and P. L’Hermite (Eds.) Odour and Ammonia Emission from Livestock Farming. pp. 17-20. Elsevior Applied Science, London, UK.
 
Canh, T.T., A.J.A. Aarnink, Z. Mroz, A.W. Jongbloed, J.W. Schrama, and M.W.A. Verstegen. 1998. Influence of electrolyte balance and acidifying calcium salts in the diet of growing-finishing pigs on urinary pH, slurry pH and ammonia volatilization from slurry. Livest. Procd. Sci. 56:1-13.
 
Keshavarz, K. 1994. Laying hens respond different to high dietary levels of phosphorus in monobasic and dibasic calcium phosphate. Poultry Sci. 73:687-703.
 
Keshavarz, K. 1991. The effect of calcium sulfate (gypsum) in combination with different sources and forms of calcium carbonate on acid-base balance and eggshell quality. Poultry Sci. 70:1723-1731.
 
Lenis, N.P., and A.W. Jongbloed. 1999. Review: New technologies in low pollution swine diets: Diet manipulation and use of synthetic amino acids, phytase and phase feeding for reduction of nitrogen and phosphorus excretion and ammonia emission. Asian-Aus. J. Anim. Sci. 12(2):305-327.
 
Mahan, D.C., T.D. Wiseman, E. Weaver, and L. Russell. 1999. Effect of supplemental sodium chloride and hydrochloric acid added to initial starter diets containing spray-dried blood plasma and lactose on resulting performance and nitrogen digestibility of 3-week-old weaned pigs. J. Anim. Sci. 77:3016-3021.
 
SAS. 1992. SAS User’s Guide: Statistics (Version 6.12 Ed.). SAS Inst. Inc., Cary, NC
 
Schiffman, S.S. 1998. Livestock odors: Implications for human health and well-being. J. Anim. Sci. 76:1343-1355.
 
Stevens, R.J., R.J. Laughlin, and J.P. Frost. 1989. Effect of acidification with sulphoric acid on the volatilization of ammonia from cow and pig slurry. J. Agric. Sci. 113:389-395.