Chick bioassay of Lysine

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Abstract
Assays of the available lysine content of twelve protein concentrates have been carried out using the parallel line assay technique. The protein concentrates, three samples each of fishmeal, meat meal, soyabean meal and groundnut meal, were obtained from the A.R.C. collaborative study group on protein quality. The parameters of response selected were live‐weight gain, efficiency of food utilisation and nitrogen retention. A chemical determination was also made of the lysine within the protein concentrate with its e‐group free to react with dinitrofluorobenzene. Wide variations were found in the available lysine content but higher values were generally recorded for those concentrates of animal origin. There was some agreement between the available lysine contents determined chemically and biologically, both procedures ranking each set of meals in the same order. For the fishmeals and groundnut meals the chemical procedure gave available lysine contents that were lower than the biological assays whereas for the meat and soyabean meals the reverse was true. In all assays available lysine contents computed from food efficiency data were greater than those obtained using live‐weight gain data for the same period. It was, however, concluded that nitrogen retention constituted the parameter giving the most precise estimate of available lysine.