EFFECT OF DIFFERENT LYSINE LEVELS ON THE METHIONINE AND CYSTINE REQUIREMENTS OF PIGLETS

A two-factorial trial using piglets (liveweight range 7-30 kg) was per formed to determine the methionine and cystine requirement in relation to the lysine requirement (i.e. the optimal (Met+Cys):Lys weight rati o). The lysine concentrations (0.9 %, 1.0 %, and 1.1 %) and the methio nine and cystine concentrations (0.5 %, 0.55 %, 0.6 %, and 0.65 %) in the diet were therefore varied. Performance parameters were daily weig ht gain, feed intake and feed conversion of the piglets. It could be d emonstrated that at the chosen lysine levels (0.9 %, 1.0 %, and 1.1 %) and the correspondingly different growth rates of the pigs, maximum w eight gain and minimal feed-per-gain ratio was achieved at different ( Met+Cys):Lys weight ratios. Piglets fed diets with only 0.9 % lysine s howed poorer performance when compared to those with a higher lysine s upply. Maximum average weight gain mas 410 g/day. Additions of Met+Cys up to a level of 0.55 % improved gain and feed conversion by 10 % and 6 %, respectively. Higher dietary Met+Cys levels did not further impr ove performance. With 1.0 % lysine included in the diet, the maximum a verage weight gain was 480 g/day. An addition of 0.55 % Met+Cys improv ed gain and feed conversion of the pigs by 19 % and 8 %, respectively. Increasing the contents of Met+Cys in the diet up to 0.60 % or 0.65 % did not lead to further improvements in the performance parameters of the pigs. When using 1.1 % lysine in the diet, the average growth rac e could be increased to a maximum of 550 g/day. Growth rate and feed c onversion showed a maximum increase at a dietary Met+Cys concentration of 0.6 %. Higher contents of Met+Cys did not further improve performa nce. In the opposite case it turned out that at the 0.5 % Met+Cys leve l there was only little effect of lysine on the growth of the piglets. Feeding 0.55 % Met+Cys, particularly increasing the lysine content fr om 0.3 % co 1.0 % led to a considerable increase in growth, while 1.1 % did not further improve performance. At a Met+Cys supply of 0.6 % an d 0.65 %, the increase in lysine from 0.9 % to 1.1 % led to a linear i mprovement in growth rate and feed conversion in the piglets. Exhausti ng maximum growth rates, the (Met+Cys):Lys weight ratio decreased from 0.66 to 0.61 and 0.57 while increasing the lysine concentration from 0.3 % to 1.0 % and 1.1 %. Similar ratios were found for feed conversio n. Here, the weight ratios were 0.65, 0.61, and 0.56 with increasing l ysine