Determination of the appetite of laying hens for methionine in drinking water by using colour cue Bestimmung der Bedarfsergänzung von Methionin über das Trinkwasser bei Legehennen anhand von Farbmarkierungen

Methionine is the first limiting amino acid in most commercial feeds for laying hens SCHUTTE et al. (1994), in addition to its main role as a component of proteins it also acts in various metabolic pathways. There are several factors (e.g. feed energy and protein content, age, genotype, sex and various environmental factors) to take into account when balancing the feed formulation EMMANS and FISHER (1986), therefore amino acids provided by compounded feeds will meet a variable proportion of the requirements of the hens in a flock BOORMAN and BURGESS (1986). Moreover, once the compound feed is mixed, both its amino acid content and also the extent to which it will meet the requirements of all the hens in any given flock are fixed. However, the methionine requirements of a greater proportion of a flock of hens could be met if it could be demonstrated that the domestic fowl had an appetite for methionine and could express it when experiencing a marginal deficiency by consuming, as a choice, water supplemented with methionine. Relatively few attempts have been made to supply amino acids in drinking water. GRIGGS et al. (1971) succeeded in administering various nutrients, including amino acids to poults through the drinking water and observed early weight gain. DAMRON and GOODSON-WILLIAMS (1987) conducted a study with broilers where 0.05% liquid DL-methionine was added to drinking water while the birds received a low-methionine diet. They found neither reductions of feed or water intake, nor any change in levels of mortality. Moreover, as a result of practising the above feeding regimen, lower mortality and reduced stress have been reported ANONYMOUS (1984). When 2-hydroxy-4 (methylthio) butanoic acid was used in drinking water DAMRON and FLUNKER (1992), the results were similar to those of DAMRON and GOODSON-WILLIAMS (1987), in that no adverse effects on feed intake, water intake, and liveability were observed.