Authors: CHENGZHANG WANG, YINGHUA SHI, YUXIN YANG, ZHENTIAN LI, YUXIA GUO, YIBAO JIANG
Abstract: Metabolism and growth trials were conducted to study true digestible methionine (tMet) and lysine (tLys) requirements for growing Lohmann egg-type cockerels and to evaluate the effects of 2 dietary tMet levels and 4 tLys levels in a factorial arrangement on growth, nitrogen balance and serum biochemical indices. In the metabolism trial, 20 caecectomised and anus-stitch-surgery healthy adult male birds were used to determine the true digestibility of Met and Lys. In the growth trial, 30 Lohmann egg-type cockerels were allocated to each of 32 floor pens (total 960 birds). During the 0-6 week starting period, 2 levels of tMet (0.37, 0.42%) and 4 levels of tLys (0.84, 0.92, 1.00, 1.08%) were fed to birds, while during the 7-10 week finishing period tMet levels were 0.29% and 0.33% and tLys levels 0.73%, 0.80%, 0.87% and 0.94%, respectively. The results showed that the survival rate in all treatments was 100% during the whole period, indicating that levels of tMet and tLys in the experiment had no influence on the rate. Considering the average daily gain (ADG), average daily feed intake (ADFI), feed conversion ratio (FCR), nitrogen retention ratio (N-retention), and serum uric acid (UA) content of all treatments together with Met and Lys digestibility, optimal tMet and tLys levels were 0.42%/1.00% (T7) for the starter diet and 0.33%/0.94% (T8) for the finisher diet. Although serum growth hormone (GH), thyroxine (T4) and triiodothyronine (T3) contents of chicks indicated significant differences among the treatments during the whole period, the relationship between dietary tMet and tLys levels and serum GH, T4 and T3 contents seemed irregular. The results also showed that there were interactions between tMet and tLys, and that this interaction had influenced ADG, ADFI, FCR, N-retention, serum UA and hormone contents significantly during the whole period.
Keywords: Digestible methionine, digestible lysine, nitrogen balance, hormone, egg-type cockerels
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