An experiment was designed to compare the compositional and in vitro fermentation characteristics of chemically delinted transgenic cottonseed (Bt, cry1C) and its non-transgenic counterpart (non-Bt). The chemical compositions of both types of cottonseeds including minerals were in their normal range. Total gas production (ml/ 500 mg substrate) from Bt and non-Bt cottonseeds was similar (P>0.05) and both types of cottonseeds, irrespective of presence or absence of Cry protein, were having similar degradability for dry matter and organic matter (P>0.05). The ammonia nitrogen concentration in the incubation medium was similar (P>0.05) for both substrates. Similar NH3-N concentrations in the inoculums and methane concentration in the total gas produced during the fermentation of 24 h indicated that degradation of cottonseed proteins in the rumen, irrespective of presence or absence of foreign protein (Cry1C), was similar. Thus, fermentability of cottonseeds in the rumen, having Cry1C protein, was similar to its traditional counterpart under in vitro conditions, which shows its potential for ruminant feeding.

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