A new cotton plant, Bollgard-II cotton, has been produced using biotechnology methods to insert the cry2Ab2 gene from Bacillus thuringiensis var. kurstaki into the Bollgard cotton genome. As a result, Bollgard-II cotton produces both the Cry1Ac and the Cry2Ab2 proteins that have insecticidal activity against Lepidopteran insect pests of cotton. The combination of both proteins in one cotton plant provides an additional tool to delay the development of pest resistance to the Cry1Ac protein in Bollgard cotton, because the Cry2Ab2 protein is a different Bt protein class than Cry1Ac. The Bollgard-II traits have been introduced into Indian cotton varieties using traditional plant breeding methods to provide Indian cotton growers an additional tool to protect cotton from lepidopteran insect damage. As a requirement for commercial development of the Bollgard-II product, a study to evaluate the nutritional value of diets containing Bollgard-II cottonseed, parental and commercial lines of cottonseed on chicken performance and carcass yield was conducted in a 42 day feeding study.
The Bollgard-II, parental control and commercial cottonseeds obtained from the Mahyco were first processed with solvent to obtain oil extracted meals. The total and free gossypol (%) contents of cottonseeds were 0.68 and 0.52 in Bollgard-II cottonseeds (MRC 6301 BG II, F2), 0.64 and 0.47 in parental control cottonseeds (MRC 6301 Non-BG II F2), 0.63 and 0.49% in the commercial cottonseed variety (NHH-44, F2). The total and free gossypol contents were 0.62 and 0.08, 0.54 and 0.05, and 0.61 and 0.07% in meals processed (solvent extraction) from MRC 6301 BG II, MRC 6301 Non-BG II or NHH-44 cottonseeds, respectively. Day-old unsexed broiler chicks (n=280) were divided into 28 groups of 10 each. Seven dietary treatments (iso-nitrogenous, 22% CP and 19.5% CP for 0-3 and 3-6 weeks and iso-caloric, 2900 kcal ME/kg from 0-6 weeks) were formulated viz., D1 (non-cotton control, soybean meal-SBM based), D2 and D3, commercial cotton (NHH-44) CSM at 10% of diet with and without additional iron), D4 and D5 (MRC 6301 BG II cottonseed CSM with and without additional iron), and D6 and D7 (MRC 6301 Non-BG II cottonseed CSM with or without additional iron at 2 ppm for every 1 ppm of free gossypol, respectively). The limiting amino acids lysine, methionine, cystine, threonine and arginine were similar in all the diets in both growth phases (0-3 weeks starting and 3-6 weeks finishing phases). Each dietary treatment was offered to four replicated groups of birds up to 6 weeks of age. The birds were reared in battery cages with brooding, feeding and watering facility. Other management practices and the vaccination schedule remained similar for all birds. Birds were weighed at weekly intervals with feed intake measured and recorded during the sample interval. A nitrogen retention trial (3 day collection period) was conducted the 6th week. At the end of 6th week, 8 birds per treatment (2 birds / replicate) were sacrificed to study certain blood bio-chemicals, carcass traits, and development of digestive and immune organs.
Body weight gain, feed intake, feed conversion efficiency, and protein and energy utilization efficiency did not differ statistically (P<0.05) either at starting (0-3 wk) or growing (3-6 weeks) and overall (0-6 weeks) growth phase. Dry matter digestibility, nitrogen intake (g/bird/day or per unit energy intake) and nitrogen retention (either expressed as percent of N-intake, g/bird/day or g/unit energy intake) remained statistically similar in all the diets. The different blood biochemical constituents, viz. serum protein, albumin and globulin, uric acid, total cholesterol and hemoglobin did not differ (P<0.05) across dietary treatments. The consumption of cottonseed meals did not influence the mortality of birds. Feather loss, blood loss, yield of giblet, gizzard and liver were not different (P<0.05) across dietary treatments. However, eviscerated yield in the broilers fed NHH-44 diets was significantly higher (P<0.01) than the other treatment groups. All treatment groups had similar eviscerated yield as compared to soybean meal based control except for the MRC 6301 non-BG II + Fe group which was lower and the NHH-44 group which was higher. Also, the yield of heart was statistically higher from the NHH-44 commercial cottonseed meal fed group compared to the soybean meal control, NHH-44 + Fe and MRC 6301 Non-BG II groups. No statistical differences across treatment were observed in the major cut up parts. Likewise, the development of digestive organs was not affected by dietary treatments except for the weight of the small intestine which was lighter in the birds fed the NHH-44 and NHH-44 + Fe groups as compared to the MRC 6301 BG II, MRC 6301 BG II + Fe and MRC 6301 Non-BGII + Fe groups. The yield of bursa and thymus was significantly higher (P<0.005) in MRC 6301 BG II, MRC 6301 BG II + Fe, MRC 6301 Non-BGII, and MRC 6301 Non-BGII + Fe groups as compared to the NHH-44 fed group. Overall, performance, carcass characteristics, nitrogen retention, organ weights and blood biochemical constituents were not different in birds fed cottonseed meal from Bollgard-II cotton compared to the non-transgenic cotton. This indicates that Bollgard-II cotton is as safe and nutritious to chickens as commercial cotton with low free gossypol.
