Dairy Cow Nutrition

Study Notes

Milk Protein and Metabolizable Energy

Typical milk protein ranges from 3.2% to 4.0%.
Metabolizable Energy (ME) is the most crucial nutrient in feed and is measured in megajoules per kg of dry matter (DM).
Energy density in feeds varies from 6 to 14 MJ/kg DM (e.g., 6 for low-quality straw to 14 for high-quality cereal grain).
An ideal energy density for dairy cow diets is above 11 MJ/kg DM.
A 1 MJ increase in energy density can lead to an increase of 2.5–3.0 liters of milk production daily for a cow consuming 15 kg DM/day.
Historically, every 5-6 MJ of ME consumed translates to an additional liter of milk produced.

Typical Dairy Cow Diets

Summer diet (Feb/March): Approximately 3-4 kg DM of pasture, 7-9 kg DM of silage, 3-5 kg of wheat or barley, and 1-2 kg of protein supplements like canola meal.
Spring pasture-based diet in Victoria: Around 17-19 kg DM/cow/day, including 12-14 kg of pasture and 3-4 kg of grain.
Grain fed usually consists of starch-based concentrates (e.g., wheat or barley).
Alternatives for protein meal include protein hay like vetch or lucerne.

Diet Formulation Considerations

Diet formulation must consider individual farm situations, which may vary uniquely.
Overconsumption of grain can lead to problems such as changes in rumen papillae and acidosis, indicating that feeding methods must be carefully monitored.

Rumen Health and Function

Signs of potential rumen dysfunction include cows not eating, lacking cud chewing, not burping, excessive lying down, and bloating.
Rumen health is vital for milk production, as microbial digestion in the rumen supplies most energy and protein needs.
Maintaining a stable rumen environment with a balanced energy and protein intake is essential for microbial sustenance.

Feeding Guidelines

Lactating dairy cows generally consume about 3.0-3.5% of their live weight in dry matter daily, with 1.2% as neutral detergent fiber (NDF).
Dry cows consume around 1.6-2.0% of their live weight in dry matter.
Crude protein levels in milker herd diets should range from 15% to 18%, depending on lactation stage.

Energy Usage Post-Calving

Cows may lose body condition up to three months post-calving, using stored energy to maintain milk production.
High-risk situations arise from excessive body condition loss during this period.

Impact of Acidosis

Acidosis can lead to detrimental effects such as weight loss, lameness, and liver damage.
Cows that recover from acute acidosis may still struggle with long-term productivity.

Flexible Feeding Systems and Cow Health

Reduced pasture availability and high production demands increase reliance on supplementary feeding, particularly grain.
Feeding strategies include control methods with pasture and grain, or partial mixed rations (PMR) that combine both in a feedpad setting.
Ongoing research evaluates how different feeding methods affect cow health and daily rumen pH patterns.

Energy Needs During Lactation

Energy requirements evolve during the lactation cycle, necessitating adjustments in feeding practices to meet demands for milk production.

Description

Test your knowledge on the nutritional requirements of dairy cows, including protein and energy levels, and their impact on milk production. Evaluate your understanding of the ideal energy density for dairy cow diets and how it affects milk yield. Get ready to moo-ve over the competition!