agricultural production guidelines
m
Veld in KwaZulu-Natal
Co-ordinated Extension KwaZulu-Natal Veld 3.1 1999
THE REQUIREMENTS OF THE ANIMAL
J M B Smith
KwaZulu-Natal Department of Agriculture
Veld in Perspective
Feed Intake by Animals
Animal Unit
The Task of Grazing
Factors Affecting
Food Intake and Performance
Grazing Management
INTRODUCTION
Livestock producers should regard themselves as grass farmers who use the animal as the harvester. Therefore the more productive the grass sward is the more productive the livestock will become. Good perform-ance of grazing animals will lead to economic production and maximum profits. The objective should be to maximise summer gains on veld and minimise winter losses. This should be reflected in good animal condition, high conception rates and high mass for age.
Veld is the cheapest form of feed and has a substantial influence on animal performance, particularly when expressed as calving percentage and weaning mass. The estimated relative contributions of i) veld grazing, ii) a winter protein supplement and iii) breeding, to calving percentage is reflected in Table 1 for different veld types.
Table 1. The relative contribution of veld, winter protein supplement & breeding, to calving percentage on different veld types.
Sourveld
Mixed veld
Sweetveld
Veld grazing
Winter protein supplement
Breeding
50%
30%
10%
65%
15%
10%
80%
10%
Total calving percentage
90%
90%
90%
Similarly, the relative contribution made by veld, winter protein supplement and breeding to the weaning mass on different veld types is shown in Table 2.
Generally, smaller animals have a relatively higher metabolic rate and will consume more food in proportion to their body mass than larger animals (see Table 3).
The mass (kg) of dry matter that most animals have the potential to consume is about 10% of their metabolic mass (provided that the herbage is off sufficiently high quality).
Table 2. The contribution made by veld, winter protein supplement and breeding, to weaning mass for different veld types.
Sourveld
Mixed veld
Sweetveld
Veld grazing
Winter protein supplement
Breeding
150 kg
30 kg
20 kg
165 kg
15 kg
20 kg
180 kg
20 kg
Total weaning mass
200 kg
200 kg
200 kg
Table 3. The consumption of food by animals in proportion to their body mass.
Type of animal
Body mass
(kg)Dry matter
feed per day
(kg)Feed intake
as % of
body massElephant
White Rhino
Beef (cow)
Beef (weaner)
Sheep
Duiker
6000
2000
450
200
50
10
60.0
30.0
10.0
5.0
2.0
0.5
1.0
1.5
2.25
2.5
4.0
5.0
Metabolic mass can be calculated from the formula:
(Mass of animal)0.75
Note: the metabolic mass of an animal can also be estimated:
1) using a calculator by entering the mass of the animal and pressing buttons %% XX ==. For example, a 400 kg animal would have a metabolic mass of 89.4 and could consume 8.9 kg dry matter per day, or
2) by using a simple "rule of thumb" to do the calculation
Table 4. An example of the expected percentage of grass growth during each month of the growing season.
Months
Sept
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Percentage of growth
Accumulative percentage growth
5
5
15
20
20
40
20
60
15
75
12
87
8
95
5
100
i.e. doubling the mass of the animal, adding 100 and taking 10 % of this figure, e.g. 400 + 400 + 100 x 10% = 90. The animal would consume 90 x 10 % = 9 kg dry matter per day. [When using the formula for sheep add 80 instead of 100 e.g. (50+50+80) x 10% = 18]
A knowledge of the grazing capacity of a farm is a prerequisite for the development of a sound veld management system or farm plan. It is essential to use a common term to define the grazing capacities because, for instance, a farm could be said to carry 3 000 sheep or 400 beef cattle or 150 dairy cows or 100 white rhinos. This would become confusing to different users.
The accepted unit to define grazing capacity is the Animal Unit (AU). This is equivalent to a steer with a mass of 450 kg consuming 10 kg of dry matter a day (which contains at least 55 % total digestible nutrients) and gains 500 g per day.
An AU is calculated as follows:
Mass of animal 0.75 x 0.01 x CF
CF = 1.5 for dairy cows
= 1.25 for other lactating females
= 1.0 for all other animals
For example, a 420 kg lactating beef cow (CF = 1.25) would be equivalent to 1.16 AU’s. Using the "thumb rule" method, 420 + 420 + 100 x 10% = 94 (metabolic mass); 94 x 0.01 x 1.25 = 1.18 AU’s.
To achieve a high performance, animals need to consume large quantities of food and water. A 450 kg cow has a daily intake of 10 kg of dry matter (DM) or 40 kg green grass, which is equivalent to about 3.5 ton DM or 14.5 ton green grass per annum respectively. Water is consumed at the rate of 10% of body mass per day, i.e. a 450 kg cow will consume 45 litres of water per day.
Under average conditions a cow will graze for approximately 8 hours, ruminate for 8 hours and rest for 8 hours. The cutting surface of a cow's teeth is about 8 cm wide and under good grazing conditions, about 0.5 g dry matter is consumed per bite. During the grazing period approximately 20 000 bites have to be taken, which is 1.4 seconds per bite to fill the cow's stomach. Therefore it is the manager's obligation to ensure that conditions are optional for his grazing animals.
A 50 kg sheep will consume approximately 2 kg dry matter or 8 kg green grass per day, which is equivalent to 0.7 ton DM or 3 ton of green grass per annum, respectively. The daily water intake is about 5 litres. Observations indicate that sheep graze for 9.5 hours, stand for 9 hours, walk for 2 hours and lie down for 3.5 hours.
FACTORS AFFECTING FOOD INTAKE AND PERFORMANCE
There are a number of factors which affect the productive performance of the grazing animal, such as veld type, time of the year and drought. These factors are beyond the control of the manager. There are, however, certain factors which can be influenced by management such as quantity, quality and height of herbage, selection of feed and livestock ratios.
The quantity of grass available to the animal does influence dry matter intake. As the bulk and density of grass increases, the dry matter intake increases at a progressively smaller rate, depending on the grass height, up to a point beyond which the amount of forage on offer to the animal does not influence intake.Quantity of herbage
Grass follows a sigmoid pattern of growth, with an initial slow period of growth, followed by rapid growth which, in turn, is followed by slow growth (Table 4).
Therefore, where the herbage is very sparse as in the early grazing season (e.g. October), animals spend time and energy in grazing and might not meet their required consumption during the limited grazing period. Animal performance will then be reduced due to the low availability of forage. Stocking the veld with too many animals has a similar effect in that it reduces the amount of forage available to each animal.
Walking results in expenditure of energy, which increases the maintenance requirement of animals at the rate of 10 % per 1.5 km walked.
Quality of herbage
The quality of herbage depends on palatability,
nutrient content and digestibility. Intake of grass is dependent on the rate of
digestibility, because as digestibility decreases, the intake also decreases.
Thus the quality of veld affects performance. Generally, during the grass
growing season the digestible crude protein and total digestible nutrients of
grass decline from 8% to 2% and from 60% to 45%, respectively. Consequently, the
intake of a 450 kg animal could decrease from 12 kg to 6 kg dry matter per day
over the season.
Herbage quality is also interrelated with quantity and height of herbage. The decrease of intake beyond a certain quantity and height of herbage is largely attributed to a decline in quality.
The nutrient requirements of different classes of stock vary. Animals with high nutrient requirements will show poor performance when provided with poor quality grazing when compared with animals with lower nutrient requirements. This is reflected in Table 5, where the performance of mature cows and young cows, grazing on good and poor veld respectively, is compared.
Height of herbage
Height of the herbage does affect intake, but it is
interrelated with the quantity and quality of the herbage. Generally, as the
height increases so does the quantity, but the quality decreases, resulting in
reduced intake.
Table 5. Calving percentage of mature and young cows on good and poor grazing.
|
Good grazing |
Poor grazing |
|
|
Mature cows Young cows |
84% 78% |
76% 47% |
From observations made, different animals show various preferences for height of herbage (Table 6).
Table 6. Herbage height preference by different animals.
|
Animal type |
Grazing height |
Grazing height |
|
Cattle Sheep Goats Horses |
8 - 70 2 - 40 2 - 150 2 - 12 |
20 - 30 <10 >10 - |
Opportunity for selection of feed
Generally, smaller animals are more selective feeders than larger animals. This is because smaller animals have a high metabolic rate and energy requirement. Therefore sheep are more selective feeders than cattle. Animals also differ in the area, plant species and parts of a plant that they select. When animals are not given the opportunity to select and are forced to graze unpalatable species, intake will decline.At the Kokstad Experiment Station it was found that, during the period May to August, cattle grazing on veld selected forage with a protein level of 1% higher than what was sampled by hand. Furthermore, sheep on veld selected forage with a protein level of 1.5% higher than that selected by cattle, i.e. 2.5% higher than that randomly sampled by hand.
Livestock ratios
Herbage is better utilized and animal performance is enhanced when different types of animals graze together in the correct ratio. It is recognised that savanna country is best utilised when game are stocked in the ratio of 40% bulk grazers, 40% concentrate feeders and 20% browsers.At the Kokstad Experiment Station, cattle and sheep when grazed together at different ratios, but at the same total AU’s per hectare, performed differently (Table 7).
Livestock gains are optimal when cattle and sheep graze together in a ratio between 3:1 and 1:1 on an AU basis i.e 3 cattle with 5 sheep, and 2 cattle with 10 sheep respectively (note that these estimates are based on the cattle weighing 450 kg and the sheep weighing 50 kg).
Table 7. Gain of cattle and sheep grazed at different ratios (AU cattle:AU sheep) at the Kokstad Experiment Station (Bioresource Group 9).
|
Cattle:Sheep |
Cattle gain |
Sheep gain |
|
No sheep 3 : 1 1 : 1 1 : 3 No cattle |
70 82 83 86 - |
- 7.9 5.5 5.3 3.4 |
Grazing management will influence each of the above factors and subsequently have a profound effect on animal performance.
Stocking rate is the most important factor in veld management. This is because increasing the stocking rate leads to a reduction in herbage quantity and height. It also reduces the scope for selective grazing and detrimentally affects species composition and grass vigour.Stocking rate
Period of stay in a camp
The period of stay in a camp, herd size and the area
of the camp are interdependent and affect the stocking intensity, which, in
turn, influences animal performance. Stocking intensity is determined by
multiplying the number of AU’s by the number of days in camp and dividing by
the area (in hectares) of the camp. This is expressed in AU days per ha. As the
stocking intensity increases, animal performance decreases. When grazing a set
of camps of various sizes or grazing capacities the period of stay must be
adjusted to keep the stocking intensity the same. The stocking intensity will
vary accordingly to the grazing capacity of the veld, veld condition and time of
the year.
Grazing cycle and period of absence
The length of time it takes to graze a set number of
camps or the period animals are out of a camp will affect the quantity, height
and quality of grass. Generally, should the grazing cycle be too long, grass
becomes rank, unpalatable and of poor quality, resulting in reduced animal
performance. For this reason, grazing cycles in the sourveld should be much
shorter than in the sweetveld.
Supplementary feeding
In sour and mixed veld animal performance could
be enhanced with mineral phosphate supplements in summer and
protein supplements in autumn and winter. Animal performance during summer also
depends on the level of winter performance due to compensatory gain. Therefore
high levels of winter supplements might be uneconomical.
It is of primary importance that, in addition to ensuring a sound veld management system, the requirements of the animal must be considered when planning the veld management system for the farm.