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Nutritional limitations to increased production on pasture-based systems
1Dexcel, Private Bag 3221, Hamilton, New Zealand. Eric.Kolver@dexcel.co.nz
The Proceedings of the Nutrition Society
|September 26, 2003
Summary
High-quality pasture limits milk production primarily due to insufficient metabolisable energy. Supplementation with grains can shift limitations to specific amino acids like methionine and lysine for grazing dairy cows.
Area of Science:
- Animal Science
- Nutritional Biochemistry
- Dairy Cattle Production
Background:
- High-quality pasture is a primary feed for grazing dairy cows globally.
- Optimizing milk production requires understanding nutritional limitations of pasture-based diets.
- Genotype selection influences a dairy cow's ability to thrive on pasture.
Purpose of the Study:
- To model the nutritional status of grazing dairy cows on high-quality pasture.
- To identify limitations to milk production imposed by pasture diets.
- To evaluate feeding strategies for overcoming these limitations.
Main Methods:
- Utilized the Cornell Net Carbohydrate and Protein System (CNCPS) for nutritional modeling.
- Simulated a 10% change in pasture nutrient composition to assess milk production sensitivity.
- Compared nutritional status and milk yield of New Zealand Friesian and North American Holstein-Friesian cows.
Main Results:
- Metabolisable energy was the primary limiting factor for milk production on high-quality pasture.
- Amino acids (methionine, lysine) became limiting when grain supplements exceeded 20 g/kg.
- Grazing North American Holstein-Friesians produced less milk than those fed total mixed rations, with reduced dry matter intake being a key factor.
Conclusions:
- High-quality pasture alone limits milk production due to energy constraints.
- Feeding strategies must address energy supply and potentially amino acid profiles for optimal performance.
- Dairy cow genotypes not adapted to pasture systems face greater nutritional challenges.