Managing Pastures Receiving Swine Wastes

Prepared by:
James T. Green, Jr.
J. Paul Mueller

Published by: North Carolina Cooperative Extension Service

Publication Number WQWM-89

Last Electronic Revision: November 1996 (MSD)

The purpose of this leaflet is to help swine farmers design and manage pasture/cattle operations to effectively use the nutrients from lagoons in an environmentally safe manner. Good pasture management requires an integrated approach of haying and grazing to maximize the transfer of nutrients from the application site. Many of the principles discussed here will be applicable to farms using poultry litter or commercial fertilizer. To obtain additional information, see "LIVESTOCK ANAEROBIC LAGOON MANAGEMENT' (NCSU publication EBAE 103-83); "DESIGN AND SPECIFICATIONS FOR PERMANENT WASTEWATER IRRIGATION SYSTEMS FOR CONTROLLED GRAZING" (NCSU publication EBAE 135-89); "SWINE MANURE AS A FERTILIZER SOURCE" (NCSU publication Soil Science Fact Sheet No. AG 439-4).

NUTRIENT MANAGEMENT

All confinement feeding operations are faced with disposal of manure nutrients. These manures offer a excellent source of low-cost nutrients for growing crops, however there are limitations on nutrient content and availabilities to the growing crop. This system does not promote using more nutrients than the land can utilize. Plant uptake and application rates should be environmentally safe.

Forage grasses can utilize high amounts of nutrients, but to optimize income on a farm and to minimize environmentally damaging nutrient losses, it is not wise to over apply nutrients. For example, 60-1000 Ibs. of N/acre may be applied to bermudagrass hay systems on some soils without causing any plant injury problems. However, it is likely that leaching losses will be great, thereby, posing a threat to ground water quality.

Table 1. Estimated nutrient composition of grasses (fescue, bermuda) cut or grazed every 3-4 weeks.

Nutrients Total Composition (DM)  
  lbs./ton %, DM
N 40 - 80 2.0 - 4.0
P 4 - 8 0.2 - 0.4
K 40 -80 1.5 - 4.0

Grazing animals excrete more than 76% of the N, P and K they consume. Even though much of the N in urine is volatilized (up to 50% in summer), manure effluent application rates on pasture should be considerably less than on hay land because of nutrient recycling. A program which emphasizes grazing management and strategic hay harvests seems to be logical. H the hay is sold or fed off site, the nutrients would be transferred reducing the on-site environmental impact.

Table 2. Nitrogen rates and timing of effluent applications to minimize soil leaching losses and luxury consumption by forage plants.

BERMUDA GRASS Maximum, N (lbs/acre/year) Time of Applications
Management    
all pasture 300 at green up +every 4-6 weeks, 4 applications of 75 lbs/A of N will total 300 lbs/A of N for the season (Apr.1, May 15, July 1, Aug. 15)
all hay 400 at green up and after each cut except for last one.
Pasture + overseed with rye in Sept. 500 green up + every 4-6 weeks with one of the applications just before overseeding + one about Feb. 15-28
FESCUE    
all pasture 200 Feb. 15-28, Apr. 1-15, Sept. 15-30 (Sept. 1-15 - Piedmont)
all hay 300 1/3 of N in Feb., 1/3 after first cut & 1/3 in Sept.

Fertilizer Requirements for Grass Growth

Bermudagrass and fescue will make satisfactory growth when plant nutrient concentrations are similar to those shown in Table 1. However, grasses can take up more nutrients than are actually needed (especially K and N) for optimum growth (this is called luxury consumption). This often occurs on manure treated fields. On coarse sandy soils N and K2O can leach leading to nutrient deficiencies. Split applications of effluent will reduce leaching and promote nutrient uptake.

Application Timing

Management suggestions in Table 2 will provide nutrients at a practical rate and time to optimize plant growth to minimize leaching losses and luxury consumption. The rates vary depending upon whether any growth is taken off the field as hay. Since cattle recycle such a high percent of what they eat, nitrogen rates for pastures are lower than for hay management.

The dates suggested allow for nutrient application when the plants are most likely to respond. Bermudagrass doesn't grow much when night temperatures are below 60øF. Whereas, fescue doesn't grow much when night temperatures exceed 70-75ø and day temperatures are above 85øF. More frequent applications of effluent at lower rates than those suggested in Table 2 could be applied, providing the total for the season remains the same.

Application of effluent or manure should take place as soon as cattle have grazed a paddock down and have been removed from the field, or immediately after hay is removed. This provides for maximum interval between application and regrazing or recutting. During respective peak growth periods for bermudagrass and fescue, regrowth may be ready to graze in 12-18 days. Therefore, some consideration may need to be given to the "palatability" or ~odor" factor that may occur when grass is irrigated with effluent. 'Wash oft' from rain or clean irrigation water would minimke any adverse effect.

Pasture Growth and Animal Performance

Keeping plants in a young, green and leafy condition will provide for rapid plant growth and best animal performance. Grazing should begin when the grass is near its best quality, and it should stop when there is suffident leaf area remaining in the stubble to stimulate rapid regrowth. See Table 3 for specific details on when to begin and when to stop grazing the various plants. These heights will provide enough "available feed" to the animal to encourage maximum consumption and enough rest for the plants to begin rapid regrowth after grazing.

Managing steers on bermuda- grass is a "balancing act'. If pastures are continually grazed between 1 and 14/z inches (this is possible with bermuda- grass but not with fescue, or orchard- grass) the forage quality will be near maximum, but it is likely that animal intake will be limited resulting in depressed ADG. On the other hand, animals are continually grazing forage over 4 inches tall, intake will be high but ADG will be depressed because of poor forage quality. The best compromise is to try to keep the grass growing between 13/a and 33/~ inches. The goal would be to offer a fresh paddock of grass 3-6 inches tall every time the animals are moved. Because of variable grass growth rates between May and September, it will not be possible to achieve this goal unless some clipping or haying is done.

Stocking Rates - (number of animal units/acre/season or year)

Stocker animals may eat about 2.5-3.0% of their bodyweight daily in dry matter. This means a 450 lb. animal consumes about 13.5 Ibs. dry matter. Over the course of the grazing season this averages about 15-17 Ibs/day (about 2000 Ibs DM/eaten for a 120 day grazing season). Hybrid bermudagrass pastures will produce ~10 tons DM/acre/year; enough feed for a stocking rate of 5-10 calves/acre for the grazing season. At these stocking rates, farmers should get effcient use of the growing grass and high gains/acre, but less than maximum average daily gains. In other words, farmers will have to compromise on ADG and gain/acre. To obtain satisfactory ADG, animals should not be forced to eat rank, stemmy or growth which is over 3 weeks of age. A reasonable goal is to obtain 1.5 lb ADG on stocker animals.

Stock density

- The stock density (or the number of animals grazing a paddock on a specific day) should be high enough to use the grass in that paddock in 1-2 days (see Table 3).

Example:

Suppose a 10 acre, grass farm is divided into 10 one acre paddocks and is stocked with 70 stockers for the grazing season. Cattle are rotated into a new paddock based on grass growth and animal needs. The stocking rate for the farm is 7 head/acre. When the animals are grazing one of the 10 paddocks the stock density is 70 head/acre.

If the paddocks are subdivided again (into 20 paddocks) and cattle graze for 1 day, the stocking rate for the farm is still 7 headiacre, but the stock density for one of the 20, '/2 acre paddocks is 140 head/acre. Even if the cattle stay on a paddock for 3 or more days the stock density remains 140/acre.

How Often to Move Cattle

Moving cattle to a fresh paddock each day will result in the highest consumption rates. If the grass is young, green, leafy and within the height range listed in Table 3, daily animal performance will be satisfactory and acre production will be high. If movement every day is not practical, then move every 2-3 days. Walk pastures every 3-5 days to judge which paddocks are scheduled to be grazed based upon growth available. If more than two paddocks are ready to graze and plant growth rate is exceeding animal consumption rate, prepare to harvest paddocks for hay. Bermudagrass growth that will not be grazed prior to 21 days of age after mid-June should be clipped for hay (assuming there is enough acreage to bale).

Clipping Pastures

If pasture growth becomes "spotty" or clumpy, it is because the stock density is not high enough to use all of the feed during the grazing period. This situation can be remedied by increasing the grazing period or increasing the stock density by making paddocks smaller through cross fencing. However, if the "spotty patches" are made up of yellow, old, or stemmy growth and animals are forced to clean it up, their performance will suffer. Clipping will encourage new leaf growth, plus animals often will eat "wilted clippings" when they otherwise would not eat the "clumps".

Wet Weather Grazing Management

When the soil is wet and soft, severe treading damage (compaction) can occur if cattle are left on a paddock too long. Pugged or hoof damaged soils will slow the regrowth rate of grass and reduce seasonal yields. This is especially true on clay or silt-loam soils and with grasses such as small grains, ryegrass, millets, sorghums, orchardgrass and fescue.

The following suggestions can minimke treading damage:

Table 3. Generalized Grazing Management Guidelines for Plant Species in the Mid and Upper South.

Species Months Pasture Growth Rate (lbs. DM/A/DAY) Height to begin (in) Height to stop (in) Stock Density Days of rest before regrazing
fescue-clover Feb-Mar Slow (5-15) 4-6 2-3 20-25 30-40
fescue-clover Apr-Jun Fast (20-50) 6-8 3-4 20-30 14-30
fescue-clover Jul-Aug Slow (10-20) 6-8 3-4 --- 30-60
fescue-clover Sep-Oct Moderate(5-15) 6-8 3-4 20-25 21-35
fescue-clover Nov-Jan Slow (0-15) 4-12+ 1-2 60-70 60-120
bermuda grass Apr-May Slow (10-30) 2-4 2 10-15 21-30
bermuda grass Jun-July Very fast(40-80) 2-4 1-2 40-60 10-21
bermuda grass Aug-Sep Fast (20-40) 2-4 1-2 30-40 20-40
pearlmillet Jun-Sep Fast (40-70) 12-24 6+ 20-40 14-30
alfalfa Apr-May Very fast (50-100) 6 to bud 3-4 20-30 10-21
alfalfa Jun-Oct Moderate (30-55) bud-bloom 2-3 20-30 21-40
alfalfa Nov-Dec Slow (10-20) before leaf 2-3 20-60 90-120
small grain Oct-Dec Moderate (30-40) 6-8 3-4 15-20 21-35
small grain Jan-Feb Slow (0-15) 6-8 3-4 20-30 30-50
small grain Mar-Apr fast (30-60) 6-10 3-4 20-40 14-21
rye grass Nov-Feb Slow (0-15) 6-8 3-4 10-15 30-90
rye grass Mar-May fast (15-60) 6-8 2-4 20-40 14-21

Feeding Supplements

If supplements are supplied to animals, they should be fed in the paddock or cattle should have limited access time to the supplement area in order to encourage maximum grazing time. Keeping animals in the paddocks will maximize pasture consumption and minimize the problem of uneven manure distribution.

Feed supplements will provide another source of nutrients into the manure management system. While supplements may give additional ADG, the cost of gain should be closely monitored. Feeding grain above 2 Ibs/head/day may reduce the amount of grass eaten. To minimke substitution impact on intake, feed grain in the afternoon. Maximizing animal gains should be secondary to manure management on many farms.

Animal Health

Internal parasites may be a significant problem for cattle on intensively grazed pastures. Animals will be returning to regraze new, young growth frequently and because of the high degree of leaf utilization it is likely that frequent ingestion of parasite larvae will occur. Animals should be dewormed prior to start of grazing. Until further research is conducted, subsequent deworming should be based on treatment every 4-6 weeks or on fecal samples taken every 4 weeks to monitor parasite populations in the animals.

Drinking Water For Cattle

Drinking water should be available in every paddock. The benefits of having drinking water available in each paddock include: increased amount of time cattle will graze; improved cattle manure distribution; improved utilization of grass; and reduced walking energy.

There are practical ways to have water in each paddock:

A less desirable alternative is to access a watering point via a gate/lane system.

Shade For Cattle

Research results do not necessarily support the economical need for shade, even though animal stress can be reduced by shade when temperatures exceed 85 90øF during the daylight. In hot weather, cattle should be forced to stay on the paddock at night and as much as possible at other times. Cattle with access to shade do not graze as much as those without it, and they tend to distribute heavy manure loads in the shaded area.

Portable shade could be built onto mobile wagons which contain minerals or "supplements". Access to shade through open gates and a lane is an alternative.

Monitoring Weight Gains

It is advisable to weigh some or all animals every ~6 weeks to monitor performance. Fecal sampling for parasites and necessary treatment could be performed at same time.

PASTURE DESIGN

The shape, size, number and grazing sequence of pastures can influence pasture use and animal performance. Below are some suggestions to improve the ease of managing cattle on pasture.

Fences

Electric fencing is an essential component in a grazing system. Be sure that a high quality (low impedance) energizer is used and that the system is properly grounded. A single strand of high tensile steel wire is suffcient for the internal paddock subdivision. Within paddocks, temporary cross fencing can be obtained with a reel of polywire or polytape and portable posts. Perimeter fences can be constructed with 2 or 3 strands of wire.

Number of Paddocks

The number of permanent paddocks will depend upon how often animals are moved. If a 1 to 3 day move seems practical, then 7-10 paddocks would be desirable. These could easily be subdivided 1 to 2 times to give the equivalent of 14-20 paddocks which would give plenty of flexibility on rotations during all growth periods.

Size of Paddocks

Paddocks should be sized so that each will provide about the same available forage or grazing days, regardless of it's area. Therefore, paddocks on the most productive soils may be slightly smaller than those on less productive soils. Similar sizes or productivities help keep the grazing time per paddock similar during the growing season. Permanent paddocks should be no smaller than one acre to facilitate equipment for haying and fertilization. Further subdivisions should be made with temporary wire.

Shape of paddocks

Square paddocks are more efficient than other shapes (rectangle, wedge shaped, etc.) because of:

When fencing long slopes, attempt to make the paddocks cross the slope so that animals are not forced to graze up and down steep, narrow hillsides.

Gates and Lanes

Lanes should be 15-20 feet wide and as centrally positioned as possible. Gates should be the same width as the lanes so that they can be used to close off the lane as well as the paddock. Gate positioning, as shown in Fig. 1 gives the manager the flexibility to further subdivide the paddock and still have an entrance into each paddock. Lanes which serve as access to shade and water will likely need to be covered with gravel to reduce severe treading in wet weather. H cattle are forced to stay in paddocks at all times, lanes will not be subject to damage.

RECORDS

Records should include the following information so that management decisions can be made consistently over the years.

Figure 1. Example of a Grazing Unit
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