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Adaptation of lactating cows to rations containing urea
Journal of Dairy Science
|August 1, 1980
Summary
Increasing urea intake in dairy cows to 0.34 g/kg body weight maximized milk production. Higher urea levels decreased milk yield and fat, impacting milk lipid profiles and blood metabolites.
Area of Science:
- Animal Nutrition
- Ruminant Physiology
- Dairy Science
Background:
- Urea supplementation is common in ruminant diets to enhance protein utilization.
- Understanding the optimal urea levels and adaptation periods is crucial for dairy cow health and productivity.
- Previous studies have indicated varying responses to urea inclusion in feed concentrates.
Purpose of the Study:
- To investigate the effects of progressive urea supplementation on jugular blood composition and animal performance in dairy cows.
- To determine the optimal urea intake level for milk production and identify potential adverse effects.
- To compare 3-week versus 6-week adaptation periods for urea intake.
Main Methods:
- Twenty-seven cows were subjected to a 6-week dietary change from urea-free to urea-containing concentrates (.34 or .66 g urea/kg body weight).
- Jugular blood samples were analyzed for metabolites, including ammonia, urea, and amino acids.
- Milk yield, milk fat content, and milk fatty acid profiles (butyrate to caproate, stearate, linoleate) were measured.
- Dry matter intake was monitored throughout the study.
Main Results:
- Dry matter intake remained unaffected by urea levels.
- Milk production peaked at .34 g urea/kg body weight, with higher intakes reducing yield and milk fat.
- Milk lipid profiles shifted, with lower short-chain fatty acids and altered stearate and linoleate levels.
- Serum ammonia and urea increased with high urea intake; nonessential amino acids varied, while essential amino acids were unchanged.
- A 6-week adaptation period was superior to 3 weeks for achieving .34 g urea/kg body weight in cows producing up to 18 kg milk/day.
Conclusions:
- A medium urea intake (.34 g/kg body weight) optimizes milk production in dairy cows.
- High urea intake negatively impacts milk yield, milk fat, and specific blood metabolites.
- Dietary adaptation duration influences metabolic responses and is critical for successful urea supplementation.