Lecture 29: Livestock Production Systems III: Pastoral Livestock Production

Learning Outcomes

• Understand how New Zealand's grass growth patterns influence seasonal pasture-based production activities.

• Learn how measurements of pre- and post-grazing pasture mass, along with pasture mass targets, are used to inform grazing decisions on farms.

Pasture-Based Production Systems

• New Zealand has a Pasture-Based Production Systems.

  • New Zealand's temperate climate is suitable for pasture-based systems.

  • Pasture serves as a cost-effective and renewable feed source for grazing livestock.

• These systems can be intensive or extensive.

• Herbage quality and quantity are key constraints to animal production in such systems.

Grass Growth Rate

• Rapid Growth: Active growth phase.

• Slow Growth: Grass builds root reserves to support a larger plant.

• Growth Slows/Stops: As grass reaches maturity and forms seeds.

  • Energy put into forming seeds not growing

• Plant Dies: Leaving a dry seedhead.

Overall Trend: Growth, Digestibility, and Nutrient value declines sharply as the grass matures.

Thus farmers try to keep the grass in the actively growing non-reproductive area for as long as possible

• Through mowing ect.

Supply and Demand in Pasture-Based Production

• Supply (IN):

  • Two factors influences pasture supply:

    • Temperature and Rainfall

• Demand (OUT):

  • Influences on pasture/animal demand:

    • Nutrient/Energy requirements

      • The maintenance energy needed not doing anything.

    • Animal activity/production

      • Any additional energy above the maintenance level: could be required for growth, reproduction/pregnancy, and lactation.

    • Environmental temperature.

      • Require energy to thermoregulate(Maintain Body Temperature)

Matching Supply and Demand

• Supply:

  • Supply is driven by season, with spring being the peak pasture supply.

• Demand:

  • Lactation represents peak nutrient (energy) demand.

• Farmers thus try match animal birth and lactation to coincide with spring pasture supply.

  • Matching peak demand with peak supply.

  • This means matching up breeding cycles.

Aligning Breeding Cycles

Animals can be seasonal or non-seasonal breeders

Seasonal Breeders

• Sheep

  • Short-day breeder

  • They come into their breeding season as the day begins to shorten

    • Become reproductively active in about autumn.

    • 5 month pregnancy: Allowing the to give birth in spring.

      • Higher chance of offspring survival as spring as increased food supply.

• Goats

• Deer

• Horses

  • Long-day breeder.

  • Become reproductively active as the day lengths begin to increase.

    • Become reproductively active in about spring.

    • 12 month pregnancy: Allowing them to give birth in spring.

      • Higher chance of offspring survival as spring as increased food supply.

    

Non-Seasonal Breeders

Reproductively active all year round (Polyestrous/Continuous Breeders).

• Cattle

  • That being said we treat cows in a seasonal fashion to align births with the pasture surplus in spring.

• Pigs

• Poultry

Pasture-Based Production Cycle

• Sheep: Lambing in spring, Mating in autumn, Gestation ~147 days, Lactation follows lambing.

• Cattle: Calving, Breeding during lactation, Gestation ~9 months, Lactation follows calving.

Seasonal Sheep Production (Generalized)

• Spring: Lambing/lactation

  • Peak pasture supply/surplus.

• Summer: Weaning

  • Summer dry leads to pasture deficit

    • But you need to feed growing lambs and look after the ewe condition for breeding,

      • Solutions Include: Supplementary feeds/specialist crops.

• Autumn: Mating.

• Winter: Pregnancy.

  • Slow pasture growth (deficit to animal requirements)

    • Solutions include winter forage crops (planted spring/early summer, grown summer/autumn, grazed winter).

Seasonal Dairy Production (Generalized)

Cows are not seasonal breeders but are typically farmed as such in NZ.

• Spring: Calving (late winter)/early lactation/breeding.

• Summer: Mid lactation.

• Autumn: Late lactation.

• Winter: Dry off cows in preparation for calving.

Supplementation and/or specialised crops used to met any additional energy demands.

Key Factors for Producers

All this relies on producers “knowing”:

• Animal nutrient demands.

• How much pasture they have.

• How much pasture will likely grow.

• How much supplementary feed they need.

And being able to:

• Estimate pasture growth

• Measure pasture mass

Measuring Pasture Mass

Two time points when the Pasture Mass needs to be Measured:

• Pre-grazing pasture mass/cover (kg DM/ha).

• Post-grazing pasture mass/cover (kg DM/ha).

  • Don’t want them grazing down to low.

• With pasture mass information, potential intakes, grazing days, and appropriate stocking rates can be calculated.

  • Intake = Pre-grazing cover – Post-grazing cover

    • Example: 2000 kg DM/ha – 1500 kg DM/ha = 500 kg DM/ha.

      • If you had 1 ha paddock with 30 cows, means they would get ~16-17 kg DM each $(500/30)$.

• Pasture utilization is the amount of pasture eaten relative to the amount of pasture grown.

  • Controlling Intake allows us to maximize efficiency and reduce feed wastage.

    • You don’t want your animals overfeeding ect.

Pre- and post-grazing Targets

Why Have Targets?

• Optimize intake: avoid restriction or excess.

• Pasture management: Avoiding the grass grow too long or too short.

  • If you graze to low you get slow regrowth(little photosynthesis due to little leaf)

  • If you let it grow to high you get low nutrient quality due to seed heads forming ect.