Agriculture Reference
In-Depth Information
(12-15 pounds) of mineral supplement per year, and over
90% passes through their system with dung and urine.
Livestock redistribute nutrients in a browsing system
depending on the variation in species browsed, the depth
of the root system of the plants, and their ability to uptake
different mineral elements. Therefore, using good rotation
management can improve soil fertility (Gerrish and
Roberts, 1999). Manure improves the physical character-
istics of the soil. Soil aggregation, friability, and tilth
increase water infi ltration and retention, and decrease root
knot nematodes and other plant root pests. Healthy pas-
tures and healthy soil microorganisms provide high quality
vegetation.
tions can affect recovery time. When using goats in vegeta-
tion management, there are times when the available plant
species are three-dimensional. Brush, shrubs, and trees are
examples of three-dimensional plant species—they are
plants that have more aerial canopy than basal cover. The
correct amount of residual is needed for rapid plant
regrowth and for yielding higher quality forage. In this
scenario, when livestock numbers per hectare (acre) are
increased, animal performance is improved. However,
overstocking will reduce the amount of residual dry matter.
Approximately 2,250 kg per hectare (2,000 pounds per
acre) of residual dry matter or less is needed for optimum
regrowth. High residual dry matter may slow recovery
rate. With high residual dry matter, a denser canopy exists
so sunlight is harder to capture; old leaves are less effi cient
producers of biomass than new leaves; and the higher ratio
of nonphotosynthetic material to green material and the
leaf to stem ratio is stressed. When the leaf to stem ratio
is stressed in residual dry matter, there is more stem than
leaf, the stems dry out exceptionally fast, and the nutrient
quality decreases rapidly.
As the amount of mature vegetation increases in a
system, digestibility decreases, crude protein decreases,
and rumen turnover time increases, all having a dramatic
effect on body condition of the goats. In lightly grazed
paddocks with a high residual dry matter, old leaves shade
the new ones and cause a net decrease in the photosynthe-
sis rate available for new growth resulting in decreased
production. Therefore, the Leaf Area Index (LAI) is a
valuable tool for assessing plant health.
V
EGETATION
Q
UALITY
AND
Q
UANTITY
The quality and quantity of vegetation produced in a given
time is dependent upon the amount of sun energy a plant
captures and converts to tissue (Table 16.1). Plants need
leaf area for photosynthesis, but a canopy cover of more
than 30% can hinder sun-capturing ability and vegetation
production. When plants are browsed, recovery time is
dependent on several environmental factors such as soil
fertility, soil moisture content, season of year, environ-
mental temperature, degree of plant defoliation, time of
plant removal, animal species browsing the land, and
residual dry matter.
Residual dry matter is the forage dry matter remaining
after a pasture/rangeland/woodland has been grazed or
browsed. Different plant species (grasses, forbs, shrubs,
brush, and trees) vary in recovery time, and climatic condi-
Table 16.1
Chemical composition of various plants browsed by goats (%).
Browse Type
Crude Protein
Neutral Detergent Fiber
Calcium
Phosphorus
Multifl ora Rose
Rosa multifl ora
18.8
34.5
0.99
0.32
Honeysuckle
Lonicera
12.8
34.5
1.12
0.30
Brambles
Rubus
15.9
24.5
0.23
0.84
Black Locust
Robinia pseudoacacia
23.0
44.0
1.26
0.21
Privet
Ligustrum
18.0
26.8
0.89
0.34
Green Briar
Smilax
17.0
39.5
0.60
0.18
Trumpet Creeper
Campsis
16.7
43.1
0.42
0.22
