Forage Maize in Animal Production Systems

Forage Maize Definition and Biology

• Definition: Maize grown primarily for whole-crop silage, utilizing the entire plant (stem, leaves, cob, and grain).
• Anatomy:
  • Tassle: The male part of the plant.
  • Silk: The female part of the plant.
  • Pollination: Occurs when pollen from the tassle falls onto silks, typically $85$ to $90$ days after sowing.

Agronomy and Site Selection

• Site Selection: Determined by heat units; historically restricted by temperature, though plastic covers allow growth in marginal areas.
• Undersowing: Planting grass between maize rows at the $4-8$ leaf stage ($June$ to mid-$July$) to reduce soil erosion, scavenge $N$ and $K$, and provide overwinter sheep nutrition.
• Harvest Timing: Ideally triggered by dry matter (DM) content rather than contractor availability.
  • Target DM: $30-32\%$.
  • Maturity Rate: Crop matures at $2-3\%$ DM per week from September onwards.

Ensiling Management

• Consolidation: Difficulties arise if DM exceeds $35\%$ or chop length is too long ($>20\,mm$).
• Aerobic Spoilage: Poor compaction leading to oxygen ingress causes spoilage; additives may help but do not replace good management.
• Stabilization: Silage should stabilize for at least one month before feeding.

Nutritional Characteristics and Rumen Function

• Nutritional Profile:
  • Dry Matter: $30-35\%$
  • Starch: $25-35\%$
  • Crude Protein: Low ($7-9\%$
  • Metabolisable Energy (ME): $10.8-11.5\,MJ/kg\,DM$
• Starch Types: Includes "bypass starch" (absorbed directly as glucose) and rumen fermentable energy. Maize starch is generally slower to ferment than cereals, reducing acidosis risk.
• Fibre Digestibility: Cell walls comprise ~$40\%$ of DM. Increased maturity increases lignin and decreases digestibility, which can limit feed intake.

Role in Livestock Systems

• Dairy Systems: Supports high milk yields and improves ration energy density. Requires protein supplementation due to low maize protein levels.
• Beef and Sheep Systems: Used in finishing and growing diets to improve liveweight gain (LWG) and DM intake.
• Crimped Maize: Grain-only feed harvested at $30\%$ moisture.
  • Energy: $14.5\,MJ/kg\,DM$
  • Starch: $65-75\%$
  • Limitations: Deficient in $Ca$ and $Na$.

Sustainability and Environmental Mitigation

• Environmental Risks: Soil erosion, nutrient leaching, runoff, and water quality degradation.
• Mitigation Strategies: Use of cover crops, reduced tillage, buffer strips, and precision nutrient management.

Questions & Discussion

• Prompt: Any questions?