METHODICAL INVESTIGATIONS ABOUT EVALUATIO N OF LYSINE UTILIZATION IN PIGS FOLLOWING EXTREME CHANGES OF PROTEIN QUANTITY AND PROTEIN-QUALITY

Aim of investigations was to measure lysine utilisation under dietary conditions which could have negative effects on well known relation be tween limiting amino acid and level of N-utilisation. Incorrect conclu sions about level of lysine availability (efficiency) could be drawn u nder such conditions. Therefore N-balance trials were done with 32 fem ale pigs (35-45 LW, fitted with urine bladder catheters), based on sem isynthetic diets (wheatgluten/cornstarch) supplemented with glutamic a cid as additional nitrogen source. Lysine concentration in the protein was further reduced by this way near to N-balance +/-0. Data calculat ion followed a Further developed N-utilisation model from Gebhardt (19 66). Experimental conditions resulted in disturbed relationships betwe en lysine concentration and protein utilisation and led to the conclus ion, that N-balance trials related to estimation of amino acid efficie ncy in feed proteins resp. to amino acid requirements should be realis ed under conditions of > 500 mg/LW(kg)(0,67) daily N-balance connected with > 2000 mg/LW(kg)(0,67) daily N-intake.