The lysine requirement of young growing male guinea pigs.

The lysine requirement of young, growing male guinea pigs was investigated by using crystalline amino acid diets containing 3.58% nitrogen. One hundred eighty-seven 3-wk-old guinea pigs were fed one of 10 crystalline amino acid diets ranging from 0.4 to 2.0% lysine or the control diet consisting of 30% casein in four 21-d performance trials. Diets were evaluated on the basis of changes in body weight, nitrogen retention, carcass weight, gastrointestinal tract weight, liver weight, hematocrit and hemoglobin plus carcass weight, gastrointestinal tract weight and liver weight as percentages of live body weight. A 0.7% dietary lysine level (0.875% lysine X HCl) was the lowest that gave results similar to those attained when casein or higher levels of lysine were fed.