[Relation between the level of free amino acids in milk and milk production]

A negative relationship of glutamic acid content and milk yield over the first 100 days of lactation was found in a set of 20 cows. In some free amino acids, large differences exist between the cows with the higher milk yield and those with the lower milk yield, the largest difference being recorded in the content of glutamic acid (in favour of the cows with the lower milk output). The group of cows with the higher milk output per day or per first 100 days of lactation showed no dependence on any of the free amino acids in milk. The group of cows with the lower milk yield showed a significant negative relation of glutamic acid content to milk yield over the first 100 days of lactation and a significant to highly significant positive relation between serine, threonine and alanine contents on the one hand and daily milk yield on the other.