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|Advisor:||Dr. J. NARASIMHA|
|Title:||1 INVESTIGATION OF STOVERS OF DUAL PURPOSE SORGHUM CULTIVARS AS FEED RESOURCE FOR SMALL RUMINANTS|
|Abstract:||A comprehensive study was conducted to screen the stovers of dual purpose sorghum cultivars in terms of chemical composition and in vitro gas production parameters and to determine the optimum stover to concentrate ratio for the best three sorghum cultivars. A growth trial of 120 days duration was conducted in 24 sheep (14.39±0.24 kg b.wt.) in order to evaluate three promising sorghum stover (SS) cultivars based complete diets with the best stover to concentrate ratio arrived from in vitro studies and compared with local SS, based on the growth performance, nutrient utilization and meat characteristics. Another growth trial of 120 days was also conducted in 24 sheep (14.50±0.41 kg b.wt.) to assess the comparative effect of different processing methods (chaffing, mash, pelleting and block making) of best sorghum stover cultivar based complete diets on the nutrient utilization and performance. The chemical composition of stovers of 11 dual purpose sorghum cultivars (IS 12015, IS 21549, IS 23143, IS 23253, IS 23765, IS 23787, IS 23789, ICSV 700, ICSR 93036, Phule chitra and Phule moule) in the present study differed significantly (P<0.05), except for phosphorus content. The in vitro dry matter digestibility (IVDMD, %), gas volume (ml/200 mg DM), in vitro organic matter digestibility (IVOMD, mg), microbial bio mass production (MBP, mg) and efficiency of microbial bio mass production (EMBP, %) values varied significantly (P<0.05) among the cultivars. Of all the cultivars, highest IVOMD value was observed in IS 23765 and lowest in ICSR 12015. Both MBP and EMBP values were higher in Phule chitra, IS 23143 and IS 12015 cultivars. Based on the chemical composition and in vitro gas production parameters, IS 12015, IS 23143 and Phule chitra cultivars were selected for further evaluation. In vitro gas production (IVGP) technique was used to evaluate the complete diets utilizing IS 12015, IS 23143 and Phule chitra sorghum stover cultivars, with different ratios of roughage to concentrates from 100:0 to 30:70. There was a gradual increase in gas volume, IVDMD, IVOMD, ME, and truly digested organic matter (TDOM) values as the concentrate proportion increased in the rations for all the three cultivars. The rations which contained 50, 40 and 30 per cent SS, have similar partition factor (PF) and EMBP 19 and these four diets were significantly (P<0.01) higher in ME, PF and EMBP compared to other rations. Among the three rations, ration with 50 per cent SS had similar TDOM, MBP and EMBP and contained higher roughage portion. Based on the results, rations containing 50 per cent SS was selected as optimum level of inclusion along with concentrates in complete diets for growth trials. Feeding of different cultivar based complete rations did not significantly influence the fortnightly body weight changes of lambs during 120 days of trial. Dry matter intake (DMI) of lambs fed dual purpose sorghum stover based rations (Phule chitra, CR-II; IS 12015, CR-III and IS 23143, CR-IV) was significantly (P<0.05) higher than the local sorghum stover based ration (CR-I). The feed conversion ratio (FCR) was not significantly different among the experimental rations. The cost per kg gain was significantly (P<0.01) higher for CR-I ration and comparable among the other three rations (CR-II, CR-III and CR-IV). The digestibilities of dry matter (DM), organic matter (OM) and total carbohydrates (TCHO) were significantly higher (P<0.05) in the rations prepared from the stovers of improved sorghum cultivars compared to the local sorghum stover. The crude protein (CP) digestibility was significantly higher (P<0.05) in lambs fed Phule chitra based ration (CR -II) than the other three rations. The lambs on all the diets were in positive nitrogen, calcium and phosphorus balance. The nitrogen balance expressed as g/d was significantly higher (P<0.05) in lambs fed CR-II (Phule chitra) than the other three rations. All the four experimental diets were significantly (P<0.05) differed in digestible crude protein (DCP) content in which, the CR-II ration contained higher DCP value when compared to other three rations. The total digestible nutrients (TDN) and metabolizable energy (ME) values were comparable among the experimental rations. The daily DCP intake (g/d) was significantly (P<0.05) higher in lambs fed CR-II ration compared to the other three rations, which were similar. The daily intakes of TDN and ME did not differ among the lambs on various diets. Feeding of different dual purpose sorghum stover cultivars based complete diets in the study, could not influence the carcass weight, dressing percentage, proportions of whole sale cuts, edible and inedible portions, yield of visceral organs, and per cent yield of bone, meat and fat and bone meat ratio in different wholesale cuts as well as carcass and meat quality. Based on the phase-II experiment, Phule chitra cultivar was selected for preparation of complete rations and these rations were processed into mash form (SSM), expander extruded pellets (SSP), feed block (SSB) and compared with chop form mixed with concentrate (SSC) through growth-cum-metabolism trial in Nellore x Deccani cross ram lambs. Processing of complete rations into different physical forms did not influence the fortnightly body weight changes of lambs. The weight gain of ram lambs fed SSP was significantly (P<0.01) higher than SSC, SSM and SSB rations. Feed conversion ratio (kg feed/kg gain) of Nellore x Deccani cross ram lambs fed SSC, SSM, SSP, and SSB rations was 12.70, 12.73, 10.87 and 12.11, respectively. The SSP fed lambs efficiently (P<0.05) utilized the feed to gain 1 kg of body weight when compared to SSC, SSM and SSB rations. Feeding SSP was more (P<0.05) economical to gain one kg of body weight than the other three rations. The lambs on extruded pellets SSP could digest more (P<0.05) OM, CP and neutral detergent fiber (NDF) than the other three processed complete rations (SSC, SSM and SSB). The lambs on all the rations were in positive nitrogen, calcium and phosphorus balance. The nitrogen balance (g/d) was significantly higher in SSP ration compared to the SSC ration. However, the nitrogen balance (g/d) was comparable among SSC, SSM 20 and SSB rations. The average DCP, TDN and ME intake (per day or per kg w0.75) of lambs fed SS based expander extruded ration (SSP) were significantly (P<0.01) higher than those fed the other three rations. The lambs consumed more DM in all groups than requirements stipulated by ICAR (2013). The average daily DCP, TDN and ME intakes of lambs in the experiment were higher than the nutrient requirements at 20 kg body weight, growing @ 75 g of average daily gain (ICAR, 2013). Processing could not influence the carcass characteristics and meat quality. Based on the results of the study, it is concluded that among the stovers of 11 evaluated dual purpose sorghum cultivars, IS 12015, IS 23143 and Phule chitra were better in terms of the chemical composition and in vitro gas production parameters. The roughage to concentrate ration of 50:50 was optimum for the preparation of complete feeds for the three selected sorghum cultivars (IS 12015, IS 23143 and Phule chitra). The results of the growth cum metabolism trial indicated that, among the three sorghum stover cultivars, Phule chitra cultivar performed better in terms of growth, nutrient utilization and carcass studies. The Phule chitra stover based complete diet with 50:50 roughage to concentrate ratio is better utilized, if it is processed into expander extruder pellets by the growing ram lambs.|
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