Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Define and calculate carrying capacity.
• Compare different grazing management systems.
• Explain the pros and cons of each grazing system for South Africa.
• Describe methods for improving pasture quality.

Lesson summary

Pasture and fodder production are critical components of livestock farming, especially in South Africa where variable rainfall and drought conditions are common. Efficient pasture management ensures a consistent and affordable feed supply for livestock, reducing reliance on expensive supplementary feeds. This module focuses on optimizing pasture production techniques and understanding the role of different fodder crops to enhance livestock productivity and profitability. Understanding these principles is vital for sustainable livestock farming, which directly impacts food security, rural livelihoods, and economic growth within South Africa.

Lesson notes

2. 1.

Carrying Capacity: Carrying capacity refers to the maximum number of animals that can graze a specific pasture area for a specific period without causing damage to the pasture or the environment. It's expressed as animal units (AU) per hectare. An Animal Unit (AU) is generally defined as a 500 kg cow with or without a calf at foot. Other livestock are converted to AU equivalents based on their feed requirements. Why is it important? Overstocking leads to overgrazing, soil erosion, reduced pasture productivity, and ultimately, reduced livestock performance. Understocking, on the other hand, wastes valuable resources and reduces potential productivity. Calculating carrying capacity accurately is crucial for sustainable pasture management.

Calculating Carrying Capacity: The basic formula to calculate carrying capacity is: ``` Carrying Capacity (AU/ha) = (Pasture Yield (kg DM/ha) x Utilization Rate (%) ) / (Animal Feed Requirements (kg DM/AU/day) x Grazing Period (days)) ``` Where: Pasture Yield: The amount of dry matter (DM) produced by the pasture per hectare (kg DM/ha). DM refers to the weight of the feed after all moisture has been removed.

Utilization Rate: The percentage of the pasture DM that is actually consumed by the animals (expressed as a decimal). A typical utilization rate is around 50% to prevent overgrazing.

Animal Feed Requirements: The amount of dry matter required by one Animal Unit per day (kg DM/AU/day). This varies depending on the type and size of livestock, but a common estimate is 10-12 kg DM/AU/day for cattle.

Grazing Period: The length of time the animals will graze the pasture (days).

Example 1: A farmer in KwaZulu-Natal estimates their pasture yields 5000 kg DM/ha annually. They plan to graze cattle (1 AU) for 180 days. Assume a utilization rate of 50% (0.5) and a feed requirement of 12 kg DM/AU/day. ``` Carrying Capacity = (5000 kg DM/ha x 0.5) / (12 kg DM/AU/day x 180 days) Carrying Capacity = 2500 / 2160 Carrying Capacity ≈ 1.16 AU/ha ``` This means the farmer can sustainably graze approximately 1.16 Animal Units per hectare for 180 days.

Example 2: A sheep farmer in the Karoo region estimates a pasture yield of 1500 kg DM/ha annually. He wants to graze sheep (0.2 AU each) for 365 days. Assume a utilization rate of 40% (0.4) and a feed requirement of 2 kg DM/AU/day (10 kg/day * 0.2 AU/sheep). ``` Carrying Capacity = (1500 kg DM/ha x 0.4) / (2 kg DM/AU/day x 365 days) Carrying Capacity = 600 / 730 Carrying Capacity ≈ 0.82 AU/ha ``` Since each sheep is 0.2 AU, the farmer can graze 0.82 AU/ha / 0.2 AU/sheep = 4.1 sheep/ha (approximately 4 sheep per hectare). 2.

2. Grazing Management Systems: Why are they important? Different grazing systems influence pasture health, livestock productivity, and overall sustainability. The choice of system depends on factors like climate, pasture type, livestock type, and farmer goals.

Continuous Grazing: Animals have unrestricted access to the entire pasture throughout the grazing season.

Advantages:* Low management input, simple to implement.

Disadvantages:* Can lead to selective grazing, overgrazing in some areas, and undergrazing in others, reduced pasture diversity. Not ideal for most South African conditions.

Rotational Grazing: Pasture is divided into paddocks, and livestock are moved systematically between them.

Advantages:* Improved pasture utilization, allows for pasture recovery, better weed control, increased forage production, and reduced parasite load in livestock.

Disadvantages:* Requires more management input, initial investment in fencing and water systems. Widely recommended for South African conditions.

Deferred Grazing: Postponing grazing on a specific pasture area to allow plants to set seed and replenish their root reserves.

Advantages:* Enhances plant vigor, improves pasture composition, and promotes natural reseeding. Useful for veld management in arid regions.

Disadvantages:* Requires careful planning and monitoring.

Strip Grazing: Animals are given access to a narrow strip of pasture each day.

Advantages:* Maximizes forage utilization and reduces waste, even distribution of manure.

Disadvantages:* High management input, suitable for intensive grazing systems.

Mixed Grazing: Utilizing different livestock species (e.g., cattle and sheep) to graze the same pasture.

Advantages:* Improves pasture utilization as different species prefer different plants, controls weeds and brush.

Disadvantages:* Requires careful management to avoid competition and ensure each species has adequate forage. 2.

3. Improving Pasture Quality and Yield: Why is it important? Improving pasture quality and yield directly translates to increased livestock productivity and reduced supplementary feed costs.

Fertilization: Applying fertilizers (nitrogen, phosphorus, potassium) to replenish soil nutrients and promote plant growth. Soil testing is crucial to determine appropriate fertilizer application rates.