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Methionine imbalance and toxicity in calves
1School of Veterinary Medicine, Azabu University, Sagamihara, Japan. abe@azabu-u.ac.jp
Journal of Animal Science
|October 26, 2000
Summary
Methionine toxicity can occur in young Holstein bull calves even with modest excesses, impacting growth and nutrient utilization. Younger, lighter calves (70-kg) are more susceptible to these adverse effects than older, heavier calves (100-kg).
Area of Science:
- Animal Nutrition
- Amino Acid Metabolism
- Ruminant Physiology
Background:
- Methionine is an essential amino acid crucial for protein synthesis and metabolic functions in young animals.
- Imbalances or excesses of methionine can lead to toxicity, affecting growth performance and nutrient utilization.
- Understanding the threshold for methionine toxicity is vital for optimizing calf diets and preventing adverse health outcomes.
Purpose of the Study:
- To investigate the occurrence and effects of methionine imbalance and toxicity in Holstein bull calves.
- To determine the dose-dependent impact of supplemental DL-methionine on growth, feed efficiency, and nitrogen retention.
- To compare the susceptibility to methionine toxicity between different calf weights (70-kg vs. 100-kg).
Main Methods:
- Two trials were conducted using Holstein bull calves (n=30 and n=24) aged 7 and 12 weeks, respectively.
- Calves received either a corn-soybean meal or a corn-corn gluten meal diet, with postruminal administration of varying doses of DL-methionine and L-lysine.
- Key performance indicators including average daily gain (ADG), feed intake, gain/feed, nitrogen (N) retention, and plasma amino acid concentrations were measured.
Main Results:
- In Trial 1, 6 g/d DL-methionine improved performance, but 18-24 g/d caused BW loss and reduced efficiency.
- In Trial 2, L-lysine improved performance; however, 16-32 g/d additional DL-methionine negated benefits and caused toxicity.
- Younger (70-kg) calves showed greater susceptibility to methionine toxicity than older (100-kg) calves, with decreased plasma branched-chain amino acids and phenylalanine observed.
Conclusions:
- A methionine imbalance and toxicity can occur in calves with even modest excesses of DL-methionine.
- Calf age and weight significantly influence susceptibility to methionine toxicity, with lighter calves being more vulnerable.
- Methionine metabolism, potentially via the transsulfuration pathway, is implicated in the observed toxicity and changes in plasma amino acid profiles.