Journal of Environmental Quality 30:2180-2187 (2001)
© 2001 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America
TECHNICAL REPORT
Waste Management
Spatial and Time Distribution of Dairy Cattle Excreta in an Intensive Pasture System
S. L. Whitea,
R. E. Sheffieldc,
S. P. Washburn*,a,
L. D. Kingb and
J. T. Green, Jr.d
a Dep. of Animal Science, North Carolina State Univ., Raleigh, NC 27695-7621
b Dep. of Soil Science, North Carolina State Univ., Raleigh, NC 27695-7619
c Dep. of Biol. and Agric. Eng., North Carolina State Univ., Raleigh, NC 27695-7625
d Jr., Dep. of Crop Science, North Carolina State Univ., Raleigh, NC 27695-7620
* Corresponding author (Steve_Washburn{at}ncsu.edu)
Received for publication January 26, 2001.
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ABSTRACT
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This study determined distribution of feces and urine from 36 lactating dairy cattle (Bos taurus) managed in a rotationally grazed 0.74-ha endophyte-free tall fescue (Festuca arundinacea Schreb.)–white clover (Trifolium repens L.) pasture. Cows were observed for 24 h five times from July 1997 to April 1998, and for 13.5 h in September 1997. During each 24-h observation period, the first grazing period (12 h) used 54% of the paddock and the second grazing period (8 h) used the entire paddock. Times and locations of all defecations and urinations from a subgroup of eight cows, observed while in the pasture, feed area, milking parlor, or in transit were recorded during the observation periods listed above and another time in May 1997. On pasture, all defecations and urinations were surveyed and mapped for all 36 cows. Feces and urine from six observation periods covered an estimated 10% of the paddock area in one year. Within 30 m of the water tank, concentrations of feces and urine from three warm-season observations were significantly greater than concentrations during three cool-season observations. Percentages of defecations and urinations on the pasture, feeding, and milking areas were highly correlated (r > 0.90) with time spent in those areas. Pasture-based systems could reduce manure handling and storage requirements proportional to the time cattle are on pastures. Manure on the pasture was evenly distributed, except around the water tank during warm-weather grazings. Results indicate that pasture-based dairy systems may require smaller, less-expensive manure management systems compared with confinement dairy farms.
Abbreviations: RH, relative humidity • THI, temperature–humidity index
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INTRODUCTION
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GRAZING livestock play an important role in the ecology of pasturelands. Livestock consume nutrients in the form of forages and use those nutrients to produce meat, milk, and fiber that are exported from the farm. However, most of the nutrients are excreted back onto the pasture in the form of feces and urine (Haynes and Williams, 1993). A portion of excreted nutrients are taken up by the pasture plants and recycled back to the pasture when the plants are consumed by the grazing animals. However, since some of the deposited nutrients are not taken up by plants, they can be a potential source of nonpoint-source pollution. Nonpoint-source pollution can occur from pasturelands and conventional drylots as the result of surface water runoff during rain storm events. According to Line et al. (1998), dairy farms can contribute significant sources of nonpoint-source pollution. Goetz (1999) found that nutrient pollution in runoff was much greater from a conventional drylot system than from a grazing system. Little is known about manure distribution patterns within dairy cattle grazing systems. Work with beef cattle in less intensive grazing management systems (2- or 3-d grazing periods) has shown that the location of water source, shade, and topography can affect the distribution of manure in pasture systems (Peterson and Gerrish, 1996).
One objective of this study was to determine the distribution of feces and urine from dairy cattle managed in a rotationally stocked pasture system. A second objective was to compare the proportions of excretions occurring in the pasture to the proportions occurring in the feeding and milking areas in relationship to the percentages of time spent in the respective areas.
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MATERIALS AND METHODS
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The study was conducted at the North Carolina State University Lake Wheeler Road Dairy Educational Unit near Raleigh, NC. Cows were part of a large-scale research project investigating the sustainability of pasture-based dairy systems that began in March 1995 (SARE Project Number LS94-63; White, 2000). Lactating dairy cattle, including 18 Holsteins and 18 Jerseys, were grazed on 29 ha of cool- and warm-season forage species all year. The stocking rate for the project was 2.48 cows/ha throughout the trial. Most cows in the herd had been in the grazing trial for one or two seasons. Data were collected from a 0.74-ha paddock of endophyte-free tall fescue and white clover. Data were collected for five 24-h periods from July 1997 to April 1998, and for one 13.5-h period in September 1997. The September observation period was only 13.5 h because of limited forage availability. Cows were milked at about 0300 and 1300 h each day. They were fed a grain supplement in a covered barn area before each milking. Cows were given fresh pasture after each milking. Pasture allocations and the supplemental feed ration were balanced using the DART ration program (Smith et al., 1994). Rations were adjusted as stage of lactation and pasture availability changed. Supplemental ration feeding amounts varied between 3.6 kg/head/d and 18 kg/head/d. When pasture was limiting in the late fall and winter, round bale silage was fed to the cows, but round bale silage was not fed on the experimental paddock during any observation days. The same paddock was used for each observation period for consistency and data were collected each time it was grazed. This paddock was grazed beginning with about 2600 kg dry matter per ha and leaving about 1600 kg dry matter per ha. The same stocking rate (2.48 cows/ha) was used as for other paddocks in the large-scale research project.
For the 24-h observations, data collection began at approximately 1130 h when cows were brought into the barn for the afternoon milking. Data collection ended 24 h later when cows were removed from the paddock to be milked again. For the 13.5-h observation period (September 1997), data collection began after the afternoon milking and ended when cows were removed for milking the next morning.
For the 24-h observations, the first grazing period (12 h) began at approximately 1430 h and ended at approximately 0230 h the next day when cows were brought in for the morning milking. The second grazing period (8 h) began at about 0400 h and ended about 1200 h when cows were removed from the pasture. The grazing periods were of unequal times due to the established milking schedule. Cows were kept in the barn from 1200 h until 1430 h and from 0230 h until 0400 h for feeding and milking. Cows were restricted to about 54% of the paddock during the first grazing period using a single electrified wire. Cows were given more than one-half of the paddock area for the first grazing period due to the longer afternoon and evening grazing period (12 h vs. 8 h). During the second grazing period the electrified wire was removed, and cows had access to the entire paddock. For the 13.5-h observation, data collection began at 1530 h and ended about 0500 h. Cows were given 100% of the paddock for the 13.5-h period. A portable water tank was located in the northeast corner of the paddock near the entrance to the paddock during each grazing. The paddock contained no natural or artificial shade and had a slope of approximately 5%, with the slope rising from the east to the west end of the paddock, away from the water tank. The soil series of the paddock was Appling sandy loam (fine, kaolinitic, thermic Typic Kanhapludult).
Data Collection
Two types of data were collected; the relative proportions of time spent and defecations and urinations for individual cows; and the distribution of defecations and urinations in the paddock for the entire herd of cows.
Individual Cow Data
The location and time of each defecation and urination from four Holsteins and four Jerseys from the herd of 18 Holsteins and 18 Jerseys were collected in May 1997, July 1997, August 1997, December 1997, February 1998, and April 1998. These dates were chosen to represent different seasons and environmental conditions and as pasture was available in the paddock. Data collected in May, July, and August 1997 were from cows that had calved in January 1997. The later collection dates were from cows that calved in September 1997. The same eight cows were used for each observation period within each season. Cows were chosen to represent a range in daily milk production and age. Milk production for the January-calving Holsteins averaged 29.2 kg/d while Jerseys averaged 21.6 kg/d. September-calving Holsteins averaged 24.3 kg/d while Jerseys averaged 18.1 kg/d. Cows were numbered with livestock paint markers and observed very closely during each 24-h period. The data included any defecations or urinations that occurred on the paddock, while in transit on the lanes, in the feeding area, and in the milking parlor in addition to the time spent in each area. Data from each cow were added across each observation period from each season and then data from all of the cows were averaged. Correlations between the average number of defecations and urinations and time spent in each area were determined within each observation period. The average number of excretions for each location was also expressed as a percentage of the total number of excretions and averaged across observation periods. Correlations of percentages of excretions to percentages of time were calculated within and across observation periods.
Whole-Herd Pasture Data
The locations of all defecations and urinations that occurred on the paddock from all 36 cows were determined in July 1997, August 1997, September 1997, December 1997, February 1998, and April 1998. Data were collected during different seasons and conditions of the year so that the effect of warm and cool temperatures could be compared. Hourly temperature and humidity data were obtained from a computerized weather station located at the Lake Wheeler Road Dairy Educational Unit operated by the State Climate Office of North Carolina. Temperature and relative humidity (RH) were used to calculate the temperature–humidity index (THI) according to the following formulas (National Oceanic and Atmospheric Administration, 1976). The formula for Celsius temperature is:
where td is the dry bulb temperature (°C) and RH is expressed as a decimal fraction. The formula for Fahrenheit temperature is:
where td is the dry bulb temperature (°F) and RH is expressed as a decimal fraction.
Observation periods when the temperature–humidity index was above 22 on a Celsius basis (72 on a Fahrenheit basis) for at least 7 h were considered warm, while the other periods below 22 were considered cool. The warm season included observations during July, August, and September while the cool season included observations during December, February, and April.
Each data collection period included grazing after the afternoon (12 h) and morning (8 h) milkings within a 24-h cycle, except that the September data period was only 13.5 h. While in the pasture, cows were observed constantly. Care was taken not to disturb the cows, especially at night when cows were resting. Observers collecting the data did not assist with the movement or handling of the herd. When cows were retrieved from the paddock for milking, they were given time to stand up and void themselves before being moved into the lane.
Each urination from every cow was marked with a colored flag. The cow was allowed to finish urinating before the observer approached the cow to mark the spot. With the exception of the 13.5-h period, urine spots from the first (Urine 1) and second (Urine 2) grazing periods within each data collection period were distinguished by different colored flags. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period. Within one or two days after the cows had grazed the paddock and had been moved to another paddock, each manure and urine spot was surveyed using the GTS-300 Topcon (Paramus, NJ) Total Station Laser Transit System. For intact feces piles, the point was surveyed from the center of the pile. For feces that were scattered, the middle of the defecation was estimated and surveyed. The fence lines and the location of the water tank were also surveyed and mapped. Data were transformed using Forsight software (Tripod Data Systems, 1997) for mapping and analysis. Maps were developed using Arc View software (ESRI, 1999). To generate the maps, areas of coverage for each feces and urine event were estimated at 0.12 m2 and 0.36 m2, respectively. This size was selected on the basis of reported areas of coverage by Wilkerson and Lowery (1973). Analysis was performed using Arc View software. Eleven arcs radiating out from the water tank location in 10-m increments were drawn. Arcs were lettered A through K with section A being closest to the water tank. Areas of the paddock within each arc were calculated and the number of defecations and urinations within each arc was counted.
The total number of defecations was numerically greater during the warm season than during the cool season (1359 vs. 1160 events). For the urinations, the total number of events was numerically greater during the cool season than the warm season (691 vs. 668). To adjust for this seasonal effect for comparative density analyses, numbers of defecations and urinations in each season were standardized to be equal across seasons. Adjustment factors were obtained by dividing the total number of defecations and urinations in one season by the respective numbers in the other season. The adjustment factor for feces was 0.85 and the adjustment for the urine was 0.97. Numbers of defecations and urinations within each 10-m arc during each season were multiplied by these factors. These adjusted numbers were then divided by the area of each arc to obtain a density (number of excretions/m2) for each 10-m arc. The location of the water tank was essentially the same for each observation period.
Statistical Analyses
Correlations between the total number of defecations and urinations for the eight cows to the time spent in each area were determined within each observation period using Microsoft Excel software (Microsoft, 1997). Cow data for each breed were compared, but were not analyzed statistically because they were similar. The densities of defecations and urinations within each arc radiating from the water tank were analyzed using general linear models procedures in SAS (SAS Institute, 1998). Each month was considered a replicate within each corresponding season. Season effects and linear, quadratic, and cubic effects of distance from the water tank and their interactions with season were tested in the model.
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RESULTS
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Percentages of the defecations were highly correlated with percentages of time spent in each area for each observation period (Table 1). Correlations within each observation period were all above 0.99 and the overall correlations were 0.94 for feces and 0.99 for urine. About 84 to 85% of excreta events occurred in the paddock area, closely associated with the 86% of time spent in the paddock (Table 1).
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Table 1. Average percentages of time spent and of defecations and urinations at various locations by eight dairy cows during five 24-h observation periods.
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The distribution and number of defecations and urinations were similar for four Jerseys and four Holsteins. Holsteins averaged 10.8 ± 0.5 defecations while Jerseys averaged 10.9 ± 0.5 defecations. For the urinations, Holsteins averaged 9.0 ± 0.6 while Jerseys averaged 8.7 ± 0.6.
For the 20-h grazing periods, the front 54% of the paddock was used exclusively for 60% of the total grazing period and contained 68 ± 4% of the urine and 65 ± 6% of the feces during the warm-season observations and 60 ± 2% of the urine and 59 ± 3% of the feces during the cool-season observations (Figs. 1, 2, 3, 4, and 5)
. The front area also included the water tank.
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Fig. 1. Feces and urine distribution by 36 lactating dairy cattle in July 1997 during two grazing periods within 24 h on a 0.74-ha paddock. Cattle were restricted to the front half of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period. Urine = 0.36 m2 (0.68-m diameter), feces = 0.12 m2 (0.39-m diameter). Concentric lines radiate at 10-m intervals from the water tank. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period.
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Fig. 2. Feces and urine distribution by 36 lactating dairy cattle in August 1997 during two grazing periods within 24 h on a 0.74-ha paddock. Cattle were restricted to the front half of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period. Urine = 0.36 m2 (0.68-m diameter), feces = 0.12 m2 (0.39-m diameter). Concentric lines radiate at 10-m intervals from the water tank. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period.
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Fig. 3. Feces and urine distribution by 36 lactating dairy cattle in December 1997 during two grazing periods within 24 h on a 0.74-ha paddock. Cattle were restricted to the front half of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period. Urine = 0.36 m2 (0.68-m diameter), feces = 0.12 m2 (0.39-m diameter). Concentric lines radiate at 10-m intervals from the water tank. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period.
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Fig. 4. Feces and urine distribution by 36 lactating dairy cattle in February 1998 during two grazing periods within 24 h on a 0.74-ha paddock. Cattle were restricted to the front half of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period. Urine = 0.36 m2 (0.68-m diameter), feces = 0.12 m2 (0.39-m diameter). Concentric lines radiate at 10-m intervals from the water tank. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period.
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Fig. 5. Feces and urine distribution by 36 lactating dairy cattle across six observation periods (five of 24 h and one of 13.5 h) on a 0.74-ha paddock. Cattle were restricted to the front half of the paddock during the first grazing period (12 h) and permitted access to the entire paddock during the second grazing period (8 h). Urine = 0.36 m2 (0.68-m diameter), feces = 0.12 m2 (0.39-m diameter). Concentric lines radiate at 10-m intervals from the water tank. Urine spots were flagged so they could be mapped, while feces spots remained visible for the mapping and did not need to be flagged. Therefore, feces spots were not differentiated between grazing periods because they were not marked during the observation period.
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Using area estimates of 0.12 m2 and 0.36 m2 for feces and urine, respectively, the total manure from the five 20-h observations and the one 13.5-h observation covered an estimated 10% of the total paddock area (Fig. 5).
When the densities in each 10-m arc for defecations and urinations were analyzed for the observation periods, season and season x distance were significant (P < 0.05) for both defecations and urinations. The interaction of season and distance can be explained by the fact that there were significantly more defecations and urinations closer to the water tank during the warm season compared with the cool season (Fig. 6 and 7)
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Fig. 6. Frequency of defecations by 36 lactating dairy cows on a 0.74-ha paddock totaled from five 24-h observation periods during which two grazing periods occurred per observation period (cattle were restricted to 54% of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period) and one 13.5-h grazing period, as influenced by distance (A to K in 10-m increments) from the water tank (General Linear Models test, F statistic = 10.45; P < 0.05). Error bars indicate mean ± standard error.
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Fig. 7. Frequency of urinations by 36 lactating dairy cows on a 0.74-ha paddock totaled from five 24-h observation periods during which two grazing periods occurred per observation period (cattle were restricted to 54% of the paddock during the first grazing period and permitted access to the entire paddock during the second grazing period) and one 13.5-h grazing period, as influenced by distance (A to K in 10-m increments) from the water tank (General Linear Models test, F statistic = 17.60; P < 0.05). Error bars indicate mean ± standard error.
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DISCUSSION
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Data from the eight cows showed that the number of excretions that occurred in a location was highly correlated to the time spent in a location. This can be affected by the manner in which cows are handled. For example, our data showed that only 4.6% of the defecations and 3.1% of the total number of urinations occurred while in the holding area near the milking parlor and in the milking parlor itself. Only two defecations and one urination event occurred within the parlor. Low incidences of defecations in the milking area suggest that the cows were handled quietly and routinely during milking because an animal response to stresses such as fear or pain is increased defecation (Friend, 1991). Cows should always be handled as gently as possible to reduce stress and minimize the amount of manure deposited in confined areas. Most of the manure (84.1% urine and 84.7% feces) occurred in the paddock, suggesting that the storage capacity and cost of manure handling facilities for pasture-based dairy systems could be substantially reduced. It should be noted that when cows were retrieved from the paddock, they were given time to stand up and void themselves before they were moved into the lanes. By giving the cows time to empty themselves on the paddock, the amount of manure on the lanes was reduced. Only 1.3% of the feces was deposited on the lanes while no urinations occurred on the lanes.
Because time spent in an area and the number of events are highly correlated, the deposition of manure can be affected by the management of the cow herd. The time spent on the pasture is often maximized for grazing cows to maximize pasture intake. Our study demonstrates that the amount of manure deposited on the pasture can be maximized. Ways to maximize the time spent on the pasture include efficient feeding systems and especially high-throughput milking parlors. If a system results in 85% of the manure being distributed on the pasture by the cattle, the manure storage and handling facilities required would have to handle only about 15% of the total manure produced. Minimal parlor cleanup and manure handling systems would be needed, and such systems would not require large, expensive, and potentially controversial lagoons. However, accommodations need to be made in the design process to account for the amount of manure produced during the periods of highest barn usage. Such high-use times would include periods of low availability of high-quality pasture-forage and veterinary examinations.
Data from previous work with beef cattle (Peterson and Gerrish, 1995) also showed that cattle tend to cluster around the water tank during heat stress. The average and maximum air temperatures for the July, August, and September observations were in and above the theromoneutral zone (15 to 25°C) of cattle (National Research Council, 1981) (Table 2). Values of THI that are above 22 are considered a mild stress on lactating dairy cattle (Dougherty et al., 1991; Armstrong, 1994). The temperature–humidity index (THI) was above 22 for the entire 24-h observation period in July, for 8 h during the August observation, and for the first 7 h of the September observation. Therefore, the cattle were under some heat stress during those observation periods. In July, the THI was as high as 30.3 and higher than 25 for 9 h in the afternoon, resulting in moderately stressful conditions. The THI for the December, February, and April observation periods did not approach 22.
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Table 2. Average, maximum, and minimum temperature and temperature–humidity index (THI) during six 24-h observation periods.
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During the three observation periods when cattle were under mild heat stress (July, August, and September), the density of both feces and urine events around the water tank was significantly (P < 0.05) higher than during the months without heat stress (December, February, and April; Fig. 6 and 7). This effect was seen especially within 30 m of the water tank (arc sections A through C). This effect on manure distribution has also been shown with beef cattle (Peterson and Gerrish, 1996). While this higher concentration can pose a problem with permanent water tanks, portable water tanks could be used to help distribute the manure nutrients more evenly. For example, a longer hose connection to the water tank could have been used to move the water tank down the fence line for the second grazing period. Another option would be to provide multiple water sources in the paddock. Despite the effect of the water tank, distributions of feces and urine were relatively random throughout the rest of the paddock (Fig. 1–5).
Shade was not used and was not a factor in our experiment but shade has been shown to affect manure distribution (Wilkinson et al., 1989; Gerrish et al., 1993). If shade is used in grazing systems, the use of portable shade structures that are moved frequently can be used to help distribute manure.
Literature surveyed reported that the range of area covered is 0.05 to 0.14 m2 for feces and 0.14 to 0.36 m2 for urine (Petersen et al., 1956; Wilkinson and Lowery, 1973; Dalrymple et al., 1994). Using 0.12 m2 and 0.36 m2 for feces and urine, respectively, the area covered from the six observational periods was only about 10% of the total paddock area. During and Weeda (1973) reported that the area affected by nutrients from a feces or urine spot can be as much as five times the area of the actual spot. If this factor of five is applied to our data, then about half of the total paddock was affected by urine and feces in one year. The potential pollution problem these nutrients pose is reduced by the uptake of nutrients by plants during the growing season. Other factors affecting nutrient transformation and movement include the action of rain, earthworm, insect, and microbial activity, and the traffic of the cattle (During and Weeda, 1973).
The distribution of manure in a pasture system can be largely controlled by managing the amount of time cattle spend in certain areas. By maximizing the time spent on the pasture the amount of manure distributed on the pasture can be maximized and the need and cost for expensive manure handling and storage equipment minimized. In addition, the manure deposited on the pasture is relatively evenly distributed over multiple grazing periods. Although concentrations of nutrients were greater near the water tank under summer conditions, use of portable water sources and shade might help distribute manure more evenly during hot weather. The use of a pasture-based dairy system significantly reduced the amount of manure deposited within the confined feeding and milking areas. Similar systems may require smaller, less expensive manure management systems compared with conventional dairy farms.
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ACKNOWLEDGMENTS
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The authors would like to acknowledge the Southern Region Sustainable Agriculture Research and Education Program of the USDA (Griffin, GA), the North Carolina Agricultural Research Service (Raleigh, NC), the North Carolina Cooperative Extension Service (Raleigh, NC), and the North Carolina Dairy Foundation (Raleigh, NC) for funding and research support. We also would like to thank the staff at the NCSU Dairy Educational Unit and to acknowledge the many volunteers who assisted with the 24-h cow watches.
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J. C. B. Dubeux Jr., L. E. Sollenberger, B. W. Mathews, J. M. Scholberg, and H. Q. Santos
Nutrient Cycling in Warm-Climate Grasslands
Crop Sci.,
May 31, 2007;
47(3):
915 - 928.
[Abstract]
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T. W. Katsvairo, D. L. Wright, J. J. Marois, D. L. Hartzog, J. R. Rich, and P. J. Wiatrak
Sod-Livestock Integration into the Peanut-Cotton Rotation: A Systems Farming Approach
Agron. J.,
June 27, 2006;
98(4):
1156 - 1171.
[Abstract]
[Full Text]
[PDF]
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TOP
ABSTRACT
INTRODUCTION
