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Published online 5 July 2005
Published in J Environ Qual 34:1439-1445 (2005)
DOI: 10.2134/jeq2004.0455
© 2005 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
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Influence of Canola and Sunflower Diet Amendments on Cattle Feedlot Manure

Xiying Hao*, Priya S. Mir, Mohammad A. Shah and Greg R. Travis

AAFC Lethbridge Research Centre, 5403 1st Ave South, Lethbridge, AB, Canada T1J 4B1

* Corresponding author (haoxy{at}agr.gc.ca)

Received for publication December 1, 2004.

   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS AND SUMMARY
 REFERENCES
 
Cattle (Bos taurus) producers can replace a part of the traditional diet of barley (Hordeum vulgare L.) grain/silage with sunflower (Helianthus annus L.) seeds or canola meal (Brassica napus L.)/oil to enhance conjugated linoleic acids (CLA) content in milk and meat for its positive health benefits. The objective of this study is to investigate the effects of feeding sunflower or canola to finishing steers on cattle manure chemical properties and volatile fatty acid (VFA) content. The control diet contained 84% rolled barley and 15% barley silage, which provided only 2.6% lipid. The other six treatments had 6.6 to 8.6% lipid delivered from sources such as hay, sunflower seed (SS), canola meal/oil, and SS forage pellets. Manure samples (a mixture of cattle urine, feces, and woodchip bedding materials) were collected and analyzed after cattle had been on these diets for 113 d. The dietary source and level of lipid had no effect on organic N and nitrate N content in manure, but significantly affected ammonia N and VFA. Inclusion of SS forage pellets, hay, or canola meal/oil in cattle diets had no significant impact on manure characteristics, but SS significantly reduced the pH and increased propionic, isobutyric, and isovaleric content. In addition, N loss after excretion (mainly from urine N) increases with the pH and N levels in both feed and manure. The combination of SS with barley silage resulted in a lower VFA and NH3 content in manure and should be a more attractive option. To better manage N nutrient cycles and reduce NH3 related odor problems, feed and manure pH should be one of the factors to consider when determining feed mix rations.

Abbreviations: ADF, acid detergent fiber • A/P, acetic/propionic acid ratio • CLA, conjugated linoleic acids • CP, crude protein • EC, electrical conductivity • NDF, neutral detergent fiber • NPN, nonprotein N • SS, sunflower seed • TC, total carbon • TNI, total N intake • VFA, volatile fatty acid


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS AND SUMMARY
 REFERENCES
 
THE CHARACTERISTICS and agronomic value of livestock manure depend largely on livestock diet (Ward et al., 1978; Safley et al., 1984; Rieck-Hinz et al., 1996), and feed ration management is an option to help feedlots become more economically and environmentally sustainable. Considerable research has been conducted on formulating feed to meet but not exceed protein (N) requirements and reduce P supplements to decrease P excretion in the cattle manure (Tomlinson et al., 1996; Klopfenstein and Erickson 2002; Satter et al., 2002). However, few studies have investigated the effect of dietary lipids on manure produced by livestock operations.

Changes in feed composition have been shown to affect odor (Miller and Varel, 2002) and ammonia emission (Swensson, 2003). In contrast, McGinn et al. (2003) have shown a positive relationship between levels of protein intake and ammonium N content of surface-sampled feedlot pen manure, but the higher ammonium N content did not translate into higher ammonia (NH3) emission. The same authors also found that the N level in cattle feed had no effect on the odorant volatile fatty acid (VFA) emission from cattle manure.

Recently, a significant number of cattle producers have started to replace a part of the traditional diet of barley grain and silage with sunflower seeds (SS) or canola meal/oil. They are high in lipid content to enhance conjugated linoleic acids (CLA) content in milk and meat (Kott et al., 2003), which can provide a wide range of positive health benefits (Bessa et al., 2000; Parodi, 2002). Past studies have shown that the dietary level of lipids may affect in vitro gas and VFA production (Getachew et al., 2004) and alter the proportion of individual VFA in rumen fluid (Chalupa et al., 1984, 1986; Jenkins, 1988). These effects also depend on the lipid source (Getachew et al., 2001; Fievez et al., 2003). Most research has focused on the cost of supplements and performance of the cattle, with little consideration of the effect on the manure produced.

An integrated study was initiated to examine the role of SS in feedlot cattle diets, considering both cattle performance and the impact on the manure produced. For the first part of the study, Shah et al. (2004) reported that dietary supplementation with SS resulted in increased concentration (% of fatty acid) of both isomers of CLA in pars costalis diaphragmatic muscle (0.433 vs. 0.224%; p < 0.05) and brisket fat (0.744 vs. 0.438%; p < 0.001), with the improvement being greatest in steers fed the diets containing hay. This was accomplished without affecting feed conversion efficiency.

The second part of this study, reported in this paper, investigates how feeding SS or canola to finishing steers affects cattle manure chemical properties and VFA content. These properties can affect its agronomic value as a fertilizer and the potential environmental impact from odor and NH3 emissions.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS AND DISCUSSION
 IMPLICATIONS AND SUMMARY
 REFERENCES
 
The experiment was conducted using 84 European and British crossbred steers in a completely randomized block design at the Lethbridge Research Center starting on 22 Oct. 2002, including the first 16-d backgrounding period (22 Oct–6 Nov. 2002). Steers with initial weights in the range of 325 to 375 kg were obtained and individually penned. Steers were not implanted or provided any feed additives. Steers were blocked by weight and randomized to one of seven treatments with 12 animals per dietary treatment. All diets contained 1% vitamin/mineral mix, with the remaining ingredients listed in Table 1. The control treatment (Diet 1) contained 2.6% lipids while Diets 2 to 7 had lipid contents between 6.6 and 8.6%, which was achieved by replacing part of the barley grain or silage with one or more of the following: SS, alfalfa forage hay, canola meal/oil or feed pellets (made from rolled barley grain, alfalfa (Medicago sativa L.) forage hay, and SS). At the same time, the crude protein (CP) content also increased to 18.8% from 13.1% (control) (Table 1).


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  		Table 1. Dietary ingredients and properties and cattle dry matter intake (DMI) and total N intake (TNI).{dagger}

 
Wood chips were used as the bedding material. Larney et al. (2001) reported that wood chip materials used at the Lethbridge Research Centre have a 31% water content (wet weight basis), 1 mg kg–1 nitrate N , 1.7 mg kg–1 ammonium N , 50.6% total carbon (TC), 0.17% organic N, 320 C/N ratio, and 5.7 pH. Before the start of this feed experiment, cattle manure was cleaned out and fresh wood chip bedding materials were added to all pens. Additional bedding materials were added when needed and the amount was recorded. Bedding materials accounted for about 60% of the dry matter weight of the manure collected 113 d after the feed trial started.

Manure samples (a mixture of cattle urine, feces, and bedding materials) were collected on 11 and 12 Feb. 2003 before individual feeding pens were cleaned out. Large amounts of manure had accumulated in each pen by this time. The age of the manure in each pen was as fresh as a few hours to as old as 113 d. Four replicate manure samples were taken for each dietary treatment. The manure was analyzed for moisture content, organic N content, pH, electrical conductivity (EC), mineral N content, and short chain VFA content.

Moisture content was determined by drying manure samples in a 60°C oven until the weight was constant. For organic N determination, the oven-dried manure samples were first coarsely ground to pass a 2-mm sieve. The coarsely ground samples were further ground (<150 µm) and organic N content was determined by dry-combustion techniques using an automated CNS analyzer (Carlo Erba, Milan, Italy).

For pH (Thompson, 2001a), mineral N (Thompson, 2001b), and VFA (modified method of Ndegwa et al., 2002) determination, exactly 10 g of wet manure was mixed with 20 mL of distilled water, sonified (BRANSON 250 15–20 s at power setting no. 8) and the pH of the sonified manure slurry was measured using a pH meter (Model 290, Orion Beverly, MA). The slurry was then centrifuged at 15000 x g for 35 min (SS34 SORVAL) to obtain the supernatant solution.

The mineral N, including ammonium and nitrate, is the potential amount of N available for the current year's crop production. For mineral N analysis, 5 mL of supernatant solution were acidified with one drop of 2 M HCl and stored at 4°C and the concentration of NH+4 and NO–3 in the solution were determined using an auto-analyzer within 24 h of extraction. The HCl was used to lower the solution pH, minimizing dissolved NH3 volatile losses during storage and analysis. The concentration of and [NH3] in the extracting solution was calculated using the Henderson-Hasselbalch equation based on extracting solution pH, total concentration [NH34], and Ka as follows:

[1]

[2]

For VFA analysis, 1.5 mL of supernatant solution was mixed with 0.3 mL of 25% orthophosphoric acid, stored in 2 mL screw-cap micro-tubes at –25°C and analyzed within 2 wk. The concentration of VFA in the supernatant solution was determined with an HP 5890 gas chromatograph equipped with a flame ionization detector. The column used to separate the acids was a Nukol (Supelco, Bellefonte, PA) 30 m by 0.32 mm by 1.0 µm. Helium was the carrier gas (linear velocity = 29 cm s–1). The volume of supernatant solution injections was 1 µL and splitless. The concentrations of the following acids were determined: acetic, propionic, isobutyric, butyric, isovaleric, valeric, calpric acid, and total VFA (sum of all the above).

A crude mass N balance was calculated based on cattle N intake, calculated N discharge, measured N content in bedding material used, and total N in the manure bedding mixture at 113 d. For the mass balance calculation, the amount of N retained by cattle is assumed to be 1.6% of weight gain (Power and Van Horn, 1998). The amount of N excreted is the difference between total N intake and N retained in the cattle body. Additionally, fecal N for all diet treatments is assumed to be 50% of total N discharge in the control diet (which had adequate N supply) although values of 26 to 66% have been reported in the literature (Bierman et al., 1999; Cole et al., 2003; Hoffman et al., 2001; Kohn et al., 2005). All diets supplied adequate protein for cattle growth, so any excess N intake above the control diet is known to be excreted in the urine (Archibeque et al., 2002; Bolan et al., 2004; Greenwood et al., 2001; Wessels and Titgemeyer, 1997).

The effects of diet on manure properties were analyzed using the ANOVA procedure in SAS (SAS Institute, 2001). When diet effects were significant at p < 0.05 probability level, the means were compared using the Tukey test. Correlation analysis was used to investigate relationships among various feed and manure properties.


   RESULTS AND DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
IMPLICATIONS AND SUMMARY
 REFERENCES
 
The manure was alkaline, with pH values ranging from 7.74 to 8.45. The pH values for the six diet treatments with high lipid and protein levels were not significantly different from those of the low lipid/protein control diet (Table 2). However, the source of the lipids had a significant effect on pH. The pH values for diets with SS (Diets 3, 4, 5, and 6) were significantly lower than the pH with canola (Diet 7). Correlation analysis reveals that manure pH was negatively related to the feed neutral detergent fiber (NDF) (r = –0.925**) and positively related to total N intake (TNI) (r = 0.861*) and dissolved NH3 concentration (r = 0.878*) in manure. Negative relationships between NDF in feed and pH of fresh fecal discharge have also been reported by Jacobson et al. (2002). Although a negative relationship between the manure pH and feed acid detergent fiber (ADF) content was also reported by Jacobson et al. (2002), there was no such relationship in this study. The increases in pH with higher TNI and dissolved NH3 concentration in manure are possibly due to increased urine N discharge as TNI increases (Topps and Elliott, 1967). The hydrolysis of urea in urine after discharge increases the NH3 content and the manure solution pH. Manure pH was not affected by the pH of the diet treatment, despite feed pH values varying from 4.8 to 5.7 among the seven diets.


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  		Table 2. Effect of dietary treatment on manure chemical properties.{dagger}

 
The manure organic N content varied between 1.62 and 1.82% (Table 2), similar to values reported previously for cattle manure using the same bedding practice in this area (Hao et al., 2001, 2004). Organic N content was positively related to TNI (r = 0.839*) and negatively related to fatty acid content in feed (r = –0.909**). Bierman et al. (1999) also reported a higher fecal N excretion when cattle TNI is high. However, organic N content was not affected by the diet treatment (Table 2), although the protein content varied from as low as 13.1% to as high as 18.8% (Table 1). Organic N comes mainly from fecal discharge (bedding materials have very low N content). Any excess protein in the feed above cattle growth is metabolized to urea and excreted in urine (Kellems et al., 1976; Topps and Elliott, 1967). In other words, similar fecal N was probably excreted across all treatments, leading to similar fertilizer values as the organic N was mineralized and converted to mineral N for crop production after land application.

The mineral N in the cattle manure was almost all from NH+4 + dissolved NH3 (99.9%) with NO–3–N (varying between 3 and 6 mg kg–1) accounting for <0.07%. The lower nitrate N in the manure could be due to the immobilization of nitrate N in the presence of the wood chips (low C to N ratio), gaseous loss of N through denitrification from frequent Chinook events (rapid rise in air temperature in winter months) and a slow rate of nitrification of ammonium N at the typical low winter temperatures. The mineral N content ranged from 6092 to 10138 mg kg–1, and was not significantly affected by the diet treatments except that Diet 7 values were significantly higher than those for Diet 4 (Table 2). But mineral N/organic N ratios were significantly higher for Diets 5, 6, and 7 than Diet 4. Although mineral N values in high lipid/protein diets were similar to the low lipid/protein control diet, Diet 7 had significantly higher values than Diet 4. In addition, dissolved NH3 content in Diet 7 was also significantly higher than the rest of the diets (except Diet 2). The high mineral N content combined with high pH values in Diet 7 (barley grain, hay, canola meal/oil) means more N will be available for current year crop production. At the same time, this could lead to higher NH3 emission during manure stockpiling and land application.

There were no significant correlations between the feed CP or TNI and the manure mineral N content, but dissolved NH3 content was positively correlated to TNI (0.878**) and CP (0.880**) and negatively to NDF (–0.810*). This is consistent with results reported by Topps and Elliott (1967) that urine N discharge is more sensitive to the amount of N in the diet and increases as the TNI increases. Urine N is the predominant contributor to NH3 compared with fecal N (Bolan et al., 2004; Kellems et al., 1976). The contribution of fecal N (organic N) decomposition to NH+4 would be less since the manure decomposition rate would be very low at the low air temperatures (–22 to 13°C) experienced during the feeding trial. Bierman et al. (1999) also reported feedlot cattle urinary N excreted was higher when the NDF content in feed was low. The higher fiber diet may stimulate hindgut fermentation, causing an increase in the amount of fecal N excreted and a decrease in urine. This reduction in urinary N excretion could potentially reduce the amount of NH3 in manure. For this study, CP, TNI, and NDF varied among the seven diets, making it impossible to differentiate the contribution of one from the others.

The manure mineral N contents reported in this study are much higher than values reported previously (Hao et al., 2001, 2004) for this region. This is in part due to the time of the year when the manure was collected and also due to the structure of the individual feedlot pens. In previous studies (Hao et al., 2001, 2004), manure was collected in June or July when the air temperature was much higher and significant amounts of NH3 volatile loss had occurred. This lowers the NH+4 and dissolved NH3–N content in the manure. For this study, manure samples were collected in February when the air temperature was low (below zero most of the time). Less NH3 volatile loss had occurred before the collection of manure samples since NH3 loss is temperature dependent.

The individual feedlot pens were enclosed on the top and three sides with only the front open. This obstructed the wind flow and reduced the water and NH3 volatile losses compared with results reported by Hao et al. (2001)(2004), which were based on manure collected from a large open holding pen with no roof or solid walls around it.

The organic N loss ranged from 1 to 15% of fecal N discharge with an average value of 7.6% for all seven diets over 113 d. On the other hand, mineral N loss ranged from 39 to 67% of urine N discharge with an average loss of 54.8% during the same time period. The overall total N loss (fecal + urine) ranged from 21.8 to 37.3% with an average of 27.5% N, lower than values (40%) reported by Klopfenstein and Erickson (2002) for winter months. This is expected since the temperature in southern Alberta is much lower than Lincoln, NE, and our experiment ended in February instead of May.

The greatest N loss was observed for Diet 7 (37.3%) and least for Diet 1 (21.8%), following a similar trend to the level of protein (N levels) and pH values in the feed and, to a lesser degree, the organic N level and pH in the manure (Fig. 1) . However, it is impossible to differentiate the effects of pH and N levels since there are only seven data points and both pH and N levels change simultaneously within the seven diets. Data in Fig. 1 suggests that manipulating feed and manure pH could play a role in reducing manure N loss, and this warrants further study.



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  		Fig. 1. The manure N loss in response to the pH and protein content in feed and the pH and organic N content of manure (open diamonds are Diets 1, 3, and 4 containing silage and closed diamonds are Diets 2, 5, 6, and 7 containing no silage).

 
Results in Fig. 1 also indicate that the source of N in feed affects N loss after excretion. Feed with silage (Diets 1, 3, and 4) had a higher N loss at similar feed pH or protein levels. In making silage, the majority of the protein N is transformed into nonprotein N (NPN) by the time the ensiling process is complete (McDonald et al., 1991). The NPN is normally converted to urea and discharged in the urine, leading to observed higher N loss.

There are some limitations to the mass balance approach used in this study since the amount of fecal discharge is based on long-term averages, not direct measurement. Nevertheless, this analysis should be useful as a basis for designing future research.

Total water-extractable VFA content was in the range of 71.8 to 119.2 mM kg–1 and was not significantly affected by the dietary treatments (Table 3), that is, there was no relationship between total VFA content in manure and the lipid source or levels in the feed. Acetic acid was in the range of 54.8 to 92.1 mM kg–1 and accounted for 75 to 82% of the total VFA (Table 3). The acetic acid was not significantly affected by diet treatment, except that Diet 5 had significantly higher acetic acid than Diet 3. Both diets had 69% rolled barley and 15% SS, but Diet 3 had 15% barley silage while Diet 5 had 15% alfalfa hay. This implies that a combination of SS and alfalfa hay stimulates, whereas a combination of SS and barley silage inhibits, acetic acid production.


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  		Table 3. Effect of dietary treatment on short chain VFA content{dagger} in manure.

 
The second major VFA was propionic acid, accounting for 12 to 18% of total VFA, with content ranging from 10.1 to 20.9 mM kg–1 (Table 3). Together with acetic acid, they made up 93 to 96% of total VFA. The propionic acid content (20.9 mM kg–1) in Diet 5 was similar to values in Diets 3, 4, and 6, but was significantly higher than values in Diets 1 (control), 2 (feed pellet), and 7 (canola meal/oil), suggesting that SS in Diets 3 to 6 might have contributed to the elevated propionic acid content in the manure. The chopped alfalfa hay in Diet 5 probably also contributed to the elevated propionic acid content in the manure, since higher propionic acid levels in rumen have been reported with alfalfa diets (Galina et al., 2004). In addition, the acetic/propionic acid ratio (A/P) was also positively correlated to the manure pH (r = 0.765*), similar to the findings of Lana et al. (1998) for rumen fluid collected from steers.

Butyric acid (varying from 1.3 to 2.6 mM kg–1), valeric acid (varying from 0.26 to 0.36 mM kg–1), and caproic acid (very close to zero) contents in the cattle manure were not affected by the dietary treatments (Table 3). In contrast, isobutyric and isovaleric acid content were significantly affected by the diet treatments (Table 3). The isobutyric (1.72 mM kg–1) and isovaleric acid (2.093 mM kg–1) content for Diet 6 was similar to values for Diets 2, 5, and 7, but was significantly higher than values for Diets 1 (control), 3, and 4. This suggests that SS or SS + chopped hay supplement in feed would also increase fermentation in the large intestine, and increase the isobutyric acid content in addition to acetic and propionic acid. But if SS were used in combination with barley silage (Diets 3 and 4), then the isobutyric acid level would be similar to the control diet (the lowest level of all the diets). This is because greater ruminal digestion of NDF occurs with silage in feed. Thus, the use of feed pellets, or SS in combination with silage or canola meal/oil, is not only beneficial in increasing cattle meat CLA content but also reduces odor problems with lower isobutyric and isovaletic VFA content.

In addition to the concentrations in the manure, the odor index is another factor affecting VFA odor potential. Odor index values of 15, 50, 112, 255, 340, and 365 for acetic, butyric, propionic, valeric, isobutyric, and isovaleric acid, respectively (Lechner, 1993 as cited by Brinton 1998) have been proposed. Based on this index and VFA content, the ordor index of manure in this experiment varied in the range of 2.24 to 3.94, but differences were not significant. The lack of treatment effect was in part due to the age of the manure (up to 113 d). Although the concentrations of isobutyric and isovaleric acid were much lower than acetic and propionic acids, their high odor indices suggest that they are much more potent in causing offensive odors from manure.


   IMPLICATIONS AND SUMMARY
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS AND SUMMARY
REFERENCES
 
Livestock manure can be a valuable resource as well as a potential hazard to the environment. The change from asset to pollutant and nuisance has occurred as animal production systems intensified over the years. Environmental pollution from animal manure is a global concern. The amount of manure generated today may be a major obstacle to future development of the livestock industry if the impact on the environment is not properly managed and controlled.

Results from this study show that pH is the key to most relevant changes in manure characteristics associated with the cattle diet since emission of both ammonia and odorous VFA are strongly pH dependent (Derikx et al., 1994). Lower manure pH will be beneficial in retaining more mineral N in manure by reducing NH3 emission, but increases VFA emission and creates more odor problems. Besides the atmospheric and environmental consequences due to NH3 emissions from livestock manure, large quantities of N, which could be used as fertilizer for crop production, are lost.

In the present study, the high manure pH and NH3 content associated with canola meal/oil supplement might be a concern since greater NH3 volatilization losses would occur during storage and land application, which reduce the N fertilizer value for crop production. The lower pH and NH3 content in manure with Diet 6 suggests that SS might be an attractive option in managing N. However, taking odor into consideration, the elevated isobutyric and isovaleric acid in manure (the most odorous compounds) associated with Diet 6 makes SS less attractive. But when SS was used in combination with silage (Diets 3 and 4), the contents of the above two acids in manure were significantly lower and were at similar levels to the control diet. In addition, acetic acid content was significantly lower in Diet 3. Combined with a lower pH and NH3 content, this makes the SS combination with silage a more attractive option than SS alone.

The results of this study demonstrate the importance of feed ration management in affecting manure properties, and subsequently N cycling and odor emission. The excretion of N and emission of NH3 can be reduced by diet manipulation, but there is a limit to how much reduction could be achieved without negatively affecting cattle performance (feed efficiency and weight gain). Formulating diet to meet nutritional needs while at the same time managing the feed and manure pH could also play an important role in reducing NH3 and VFA emission and associated odor problems for sustainable livestock production, both economically and environmentally.


   ACKNOWLEDGMENTS
 
We gratefully acknowledge technical assistance from Brett Hill, Pamela Caffyn, Darrel Vedres, Charmaine Ross, and Brad Linderman; organic N analysis by Clarence Gilbertson; statistical advice from Toby Entz; and technical advice from Dr. Chi Chang and Mr. Matt Oryschak. A special thanks to Yvonne Bruinsma for keeping X. Hao up-to-date with the latest references. This is LRC contribution no. 387-04006.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS AND DISCUSSION
 IMPLICATIONS AND SUMMARY
 REFERENCES
 




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