Manure Management: Dairy

Introduction

Drinking

Table 1 provides estimates of drinking water requirements in gallons per cow per day. Consumption of 25-30 gal of water per day by lactating cows is common, which varies depending on milk yield, dry matter intake (DMI), temperature, and other environmental conditions.111

Cow Washing

Presently most dairies, in warm climates, bring cows to be milked into a holding area equipped with floor-level sprinklers, which spray water upward to wash cows. Each cow usually has a holding area of about 15 ft2 and are typically washed for 3 min. Amount of water used per cow should be calculated for each dairy. An estimate for conservative use is that a holding area for 300 cows is 30 x 150ft2 (15 ft2 per cow) and is equipped with sprinklers with 5-ft spacing (say 7 across and 30 rows) having 210 sprinklers. If each sprinkler applies 5 gal min', total usage is 1050gal min' or 3150 gal for 3min, the average consumption per cow would be 3150/300 = 10.5 gal per cow per wash cycle. If cows are milked three times this would require 31.5 gal per cow per day.

The washing system previously described also helps in cooling of cows while they are crowded together waiting to be milked. However, the cooling effect could be achieved by sprinkling a little amount of water from above, alternatively with fans to give evaporative cooling, if cows were clean enough so that extensive washing was not required and water conservation was necessary.

Washing Milking Equipment and Milking Parlor

Use of water for these purposes is not as directly related to the number of cows as for other uses. For washing milking equipment, a common wash vat volume is 75 gal. If this is filled for rinse, wash, acid rinse, and sanitizing at each of three milkings, this amounts to 900 gal for the herd, e.g., with 300 cows, only 3 gal per cow per day. This is an extremely small component of the total water budget. The amount used to wash out the milking parlor varies largely. If only hoses are used, the amount may be as little as 2 gal per cow per milking or 6 gal per cow per day if cows are milked three times daily. If flush tanks are used, the amount may be more, i.e., nearly 3000gal per milking or 9000 gal day for three times, equivalent to 30 gal per cow per day for a 300-cow system.

TABLE 1 Predicted Saily Water Intake of Dairy Cattle as Influenced by Milk Yield, DMI, and Season'1-1

Milk Yield (lb)

Cool Season (e.g., February)

Warm Season (e.g., August)

DMI

(lb)

Water Intake

(gal)

DMI

(lb)

Water Intake (gal)

0

25

11.5

25

16.3

60

45

22.2

44

26.8

100

55

28.6

48

31.9

a Drinking water intake predicted from equation of Murphy et al., J. Dairy Sci., 1983, 66, 35: Water intake (lb day-1) = 35.2 x DMI (lb day4) + 0.90 x milk produced (lb day4) + 0.11 x sodium intake (g day4) + 2.64 x weekly mean minimum temperature [°C = (°F -32) x5/9]. For examples above, diet dry matter was assumed to contain 0.35% Na. Predicted water intakes (lb) from formula calculations were divided by 8.3461b water per gal to convert to gallons.

b Average minimum monthly temperatures for February (43.5°F) and August (71°F) used with prediction equation were 70 years averages for specified months at Gainesville, FL (Whitty et al., Agronomy Dept, Univ. FL, 1991).

Sprinkling and Cooling

Sprinklers along with fans are used for evaporative cooling to relieve heat stress in dairy cows during hot periods of the year. Their use has shown increased cow comfort (lowered body temperature and respiration rates) and economic increases in milk production and reproductive performance.12,31 Application rates used by dairymen vary. Florida experiments compared application rates of 51 gal per cow per day, 88 gal per cow per day, and 108 gal per cow per day at 10 psi in one experiment and 13 gal per cow per day, 25 gal per cow per day, and 40 gal per cow per day in another experiment. The application rate, 13 gal per cow per day, is close to the estimated evaporation rate from the cow and surrounding floors. This component should be considered in water use but not in runoff water that must be managed in the manure management system. We estimate 25 gal per cow per day as the minimum practical application rate in order to get adequate coverage of cows to cool them because often they are not in the sprinkled area. Total application days per year vary from 120 days to 240 days. A separate water well, or reserve tank and booster pump, may be needed to supply short-term high demand required by the sprinkler system.

Flushing Manure

Flushing manure can be made a clean and labor-saving process, if facilities include concrete floors with enough slope so that water flow propelled by gravity could be used to move manure. Amounts of water used per cow vary widely depending on size and design of facilities and frequency of flushing. However, usually a flush of about 3000 gal is required to clean an alley width of 10-16 ft. If 4 alleys are common for every 400 cows and alleys are flushed twice daily, this would amount to an average use of 60 gal per cow per day. Many dairies use more flushings per day.

Recycling Dairy Wastewater through Irrigation of Forage Crops

Most often nitrogen is the nutrient on which manure application rates are budgeted. To maximize nutrient uptake, crop growth should be as vigorous as possible. This requires irrigation during most of the year in many dairy regions for the disposal of flushed wastewater. In southern regions, multiple cropping systems are possible, which will recycle effectively nitrogen excretions from 100 cows on a sprayfield or manure application field of about 30 acres.141

Tentative estimates of total water needs of the growing crops in warm climates average about 1.75 in. of water per week (0.25 in. per day) from irrigation plus rainfall with a minimum of 0.5 in. per week tolerated even in rainy season on sandy soils.15,61 Table 2 provides estimates of water requirements for two triple cropping forage systems that are common in southern climates. In sandy soils that hold only about 1.0 in. of water per foot of soil depth, some amount of rainfall cannot be stored. Therefore, even in heavy rainfall seasons, judicious irrigation is often needed during lower rainfall weeks. Limited data are available on the maximum amount of water that could be applied and not reduce yield or quality of forage and not result in pollution of groundwater with nitrates and other minerals. However, the maximum probably is at least 35-45 in. per year above the acre totals in Table 2.

Rainwater from Roofs and Concrete Areas

Rainwater entering wastewater holding areas can be significant. For example in the dairy representing typical minimum water usage with a flush system in southeast United States (Table 3), the net accumulation during the hot season was calculated as follows: assumed wastewater holding area is lacre surface area per 100 cows, net rainfall accumulation in holding area is 3in. more than evaporation per month, concrete areas and/or undiverted roof areas that capture rainfall are 15,000 ft2 per 100 cows that divert 15,000/43,560 ft2 per acre of the 3 in. to the wastewater holding facility. Titus, 3 in. + 0.344 x 3 = 4.03 acre in. mo4 or essentially 1.0acre in. per week per 100 cows (approximately 27,000 gal per 100 cows).

TABLE 2 Crop Yield and Water Requirement Estimates for Two Triple Cropping Forage Systems

Crop No.

Name

Silage Yield

lb/A DM

lb/lb

DM

Water Required

А-in. Total

Ton/A 35% DM

Ton/А DM

lb/A Total

gal/A Total

1

Wheat

10

3.5

7000

500

3,500,000

419,362

15.4

2

Corn

24

8.4

16,800

368

6,182,400

740,762

27.3

3

Corn

14

4.9

9800

368

3,606,400

432,111

15.9

Total

48

16.8

33,600

13,288,800

1,592,235

58.6

1

Rye

10

3.5

7000

500

3,500,000

419,362

15.4

2

Corn

24

8.4

16,800

368

6,182,400

740,762

27.3

3

F. Sorghum

18

6.3

12,600

271

3,414,600

409,130

15.1

Total

52

18.2

36,400

13,097,000

1,569,254

57.8

a A = acre; No. = number; DM = dry matter.

Developing a Water Budget

A wide range exists in water usage on dairy farms. For most dairy waste management systems designed to utilize flushed manure nutrients through cropping systems grown under irrigation, water amounts are small in relation to irrigation needs for crop production. Costs for construction of storage structures for holding wastewater until used for irrigation warrant consideration. For example, water-use budgets given in Table 3 show that water usage is small in comparison to irrigation needs when there are 30 acre of sprayfield crop production per 100 cows. Conversely, the amounts used in most dairy systems would be large and unmanageable if application through irrigation is not an option or if less acreage for irrigation is available than needed for application of all manure nutrients.

If a dairy does not have acreage available close by to utilize manure nutrients and water through an environmentally accountable sprayfield application system, it would be necessary to export nutrients off the farm, preferably as solid wastes to avoid excessive hauling or pumping costs. If the water and manure nutrients cannot be used through irrigation, a non-flush system should be utilized. However, usually some irrigation is possible, permitting dairymen to use cow washers and limited flushing if they scrape and haul manure from some areas.

Strategies to minimize water usage: Table 3 presents one column indicating a theoretical minimum amount of water use in a dairy. This system implies that cows are clean and cool enough so that sprinkler washers are not required to clean and cool cows while being held for milking. In addition, it is assumed that all of the manure is scraped and hauled to manure disposal fields or transported off the dairy in some other fashion. Intermediate steps that might be taken include the following:

  • 1. Scraping and hauling manure from high use areas such as the feeding barn so that this manure can be managed off the dairy.
  • 2. Using wastewater rather than fresh water to flush manure from feeding areas and freestall barns.
  • 3. Using a housing system that will keep cows clean enough so that cow washers are not required to clean cows before milking. This system, however, may require use of alternating sprinklers and fans to keep crowded cows cool during hot weather conditions.

If flushing is desired in conjunction with scraping and hauling from heavy use areas, perhaps the feeding area could be flushed with recycled water after scraping to clean the area. These procedures would reduce total nutrient loads retained in wastewater and would significantly reduce the size of the sprayfield needed for water and manure nutrient recycling.

TABLE 3 Estimated Water Budgets for Three Example Dairies

Water Use in the Dairy

Flush Systems

Non-Flush Theoretical Minimum

Worksheet for Your Dairy

Typical Need during Hot Season

Common Usage on Some Dairies

Drinking (cows)

25

25

25

Cleaning cows

32

150

0

Cleaning milking equipment

3

5

3

Cleaning milking parlor

30

30

6

Sprinklers for cooling

25

130

12

Flushing manure

60

80

0

Total use per cow per day

175

400

46

Total use per 100 cows per day

17,500

40,000

4600

Use per 100 cows per week

122,500

280,000

32,200

Water in milk per 100 cows per week

4500

4500

4500

Estimated evaporation (at 20% of use)

24,500

56,000

6440

Average rainfall and watershed drainage into storage facility per 100 cows per week

27,000

27,000

13,000

Wastewater produced from 100 cows/week

120,500

246,500

38,760

Acre in. per 100 cows per week in. per week

4.44

9.08

1.43

if 30 acre in sprayfield

0.15

0.30

0.05

a All values are in gal unless otherwise noted.

Example calculations (column 1): Total use per cow per day = 175 gal; total use per 100 cows per week = 122,500 gal less 4500 in milk and 24,500 gal evaporation = 93,500 gal week-1; net rainfall and watershed drainage to storage per 100 per cows per week = 27,000; acre in. per 100 cows per week = (93,500 + 27,000)/27,152 gal per acre in. = 4.44.; if 30 acre were in sprayfield, 4.44/30 = 0.15 in. week-1.; if crop needed 1.75 acre in. week"1 (a common average), a total of 1.75 in. x 30 acre x 27,152 gal per acre in. = 1,425,480 gal is needed of which only 120,500 gal (8.5%) would come from dairy wastewater. The remaining (91.5% of total) would have to come from rainfall or fresh irrigation water.

References

  • 1. Beede, D.K. Water for dairy cattle. Large Dairy Herd Management; American Dairy Science Assoc.: Champaign, IL, 1992; 260-271.
  • 2. Bray, D.R.; Beede, D.K.; Bucklin, R.A.; Hahn, G.L. Cooling, shade, and sprinkling. Large Dairy Herd Management; American Dairy Science Assoc.: Champaign, IL, 1992; 655-663.
  • 3. Van Horn, H.H.; Bray, D.R.; Nordstedt, R.A.; Bucklin, R.A.; Bottcher, A.B.; Gallaher, R.N.; Chambliss, C.G.; Kidder, G. Water Budgets for Florida Dairy Farms; Circular 1091; Florida Coop. Ext., Univ. Florida: Gainesville, 1993.
  • 4. Van Horn, H.H.; Nordstedt, R.A.; Bottcher, A.V.; Hanlon, E.A.; Graetz, D.A.; Chambliss, C.F. Dairy Manure Management: Strategies for Recycling Nutrients to Recover Fertilizer Value and Avoid Environmental Pollution; Circular 1016; Florida Coop. Ext., Univ. Florida: Gainesville, 1998; 1-24.
  • 5. North Florida Research and Education Center. AREC Research Report 77-2; IFAS, University of Florida, Gainesville, 1977.
  • 6. Wesley, W.K. Irrigated Corn Production and Moisture Management; Bui. 820; Coop. Ext. Serv., Univ. Georgia College of Agric. and USDA, 1979.
 
Source
< Prev   CONTENTS   Source   Next >