DEVELOPMENT OF A SEMISYNTHETIC DIET FOR AMINO ACID-EXPERIMENTS WITH LAYING HENS

In view of future experiments concerning the ideal amino acid pattern for laying hens a semisynthetic diet should be developed, in which the concentration of essential amino acids should be very close to requirements and in which at least 30 % of each essential amino acid should be provided in free form. In trial 13 semisynthetic diets with about 13 % crude protein were compared. The amino acid pattern of 1 diet (diet AS100) was exactly the same as in egg protein, while compared to egg protein the essential amino acids of the other 2 diets were reduced by 15 % (diet AS85) and by 30 % (diet AS70). The concentrations of essential amino acids of diet AS70 did not meet the requirements as the hens of this treatment produced significantly lower than the hens of the 2 higher amino acid-levels (AS100 and AS85). There were no differences in production between the treatments AS100 and AS85, but with 70 % egg production rate and losses of body mass production of these hens was significantly lower than production of those hens, that received a fourth, more practical diet (diet K) based on cereals and soybean meal (17 % crude protein) (-40 % egg number and daily egg mass). Adding, one after the other, 2 % bicarbonate-salts, 2 % glutamic acid and essential amino acids and increasing meal frequency from once to 3 times feeding per day could not raise production of the hens, that received semisynthetic diets. In a second trial, lasting for 3 weeks, 2 factors (crude protein content of diets and % free amino acids in crude protein) with 2 levels each were tested in cross classification. Increasing crude protein from 13.5 % to 16.5 % and reducing the amount of free amino acids in crude protein from 60 % to 40 % did not raise the production data or exert any influence on blood plasma free amino acid levels, except of asparagin concentration. All 4 experimental treatments of the second trial produced equally and egg production rate of 70 % was the same as that of treatments AS100 and AS85 in trial 1. The poorer utilization of free dietary amino acids for protein synthesis, as compared to proteinbound amino acids, together with a too short intake of dietary energy was thought to be responsible for the low production level of hens receiving semisynthetic diets.