Effect  of the  Bt-  or conventional cottonseed meal  was assessed  as well as the  performance, fermentation, ciliate protozoa population and microbial enzyme  of lambs.  Three  feed mixture (FM, forage: concentrate ration of 35: 65)  contained  groundnut oilmeal  (GNM),  insect protected  Bt- cottonseed meal (Bt-CM) or conventional whole cottonseed (C-CM) as protein source, were fed for 123 days to the control, C-CM and Bt-CM group of lambs, respectively. Whole seed meal Bt- and C-CM had similar nutrient composition.  The Ca was higher while Zn content was lower in C-CM. Both CM had similar metabolizable energy (MJ/kg DM). Lambs of three groups had similar daily gain, DM intake and nutrient  digestibility.  Rumen fluid  pH  and TVFA were  similar, while  ammonia-N (mg/l) was higher (p<0.001) in control lambs.  Cottonseed feeding  eliminated  (p<0.001)  rumen  protozoa;  protozoa were 101.1, 59.0 and 39.6 ×104 / ml  in  rumen fluid respectively in control, C-CM and Bt-CM diet fed lambs. Rumen enzymes  activities  of  xyalanase,  β-glucosidase and  β-xylosidase  were similar, while  Bt-CM feeding reduced (p=0.010) carboxymethyl cellulase  (CMCase) activity by 47% and  increased proteases activity by 22%. The study concludes  that  inclusion of Bt-CM produced pronounced defaunation with reduced rumen ammonia concentrations, which improved daily gain.  Therefore,  Bt-CM  can be incorporated at 180 g/kg in lamb diet.

Keywoards: Cottonseed, genetically modified feed, performance, fermentation, rumen enzymes.

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