Twenty four sorghum stovers were investigated with sheep for organic matter digestibility (OMD) and intake (OMI), and for digestible organic matter intake (DOMI) and for relations between laboratory fodder quality traits and these in vivo measurements. Statistically highly significant and nutritionally important differences were found between the stover with OMD differing by 15 percentage units and OMI and DOMI varying 1.6 and 2 times, respectively. For each of the in vivo measurements, chemical (NDF, ADF, ADL) and in vitro (in vitro digestibility, metabolisable energy content) traits were identified which accounted for at least 50% of the variation in the respective traits. Using multiple regression procedures and stringent cross-validation (“blind-predictions”) procedures OMD, OMI and DOMI could be predicted with R2 for comparing observed and predicted values of 0.36, 0.65 and 0.75, respectively. The reported research showed selection for dual purpose sorghum cultivars is promising, and identified and validated simple laboratory traits that can be used for such phenotypin

Blummel, M

Khan, A A

Prasad, K V S V

Ramkrishna Reddy, Ch

Ravi, D

Reddy, B V S

Rego, T J

ICRISAT Open Access Repository

113Stover Quality Traits for Improvement ofDual-Purpose SorghumCh. Ramkrishna Reddy*, A.A. Khan, K.V.S.V. Prasad1, D. Ravi1,B.S.V. Reddy2, T. Rego2 and M. Blümmel11International Livestock Research InstitutePatancheru-502 324, India2International Crop Research Institute for Semi-Arid TropicsPatancheru-502 324, IndiaABSTRACTReddy, Ch. R., Khan, A.A., Prasad, K.V.S.V., Ravi, D., Reddy, B.S.V., Rego, T. and Blümmel, M.2010. Stover quality traits for improvement of dual-purpose sorghum. Animal Nutrition and Feed Technology,10S: 113-119.Twenty four sorghum stovers were investigated with sheep for organic matter digestibility (OMD)and intake (OMI), and for digestible organic matter intake (DOMI) and for relations between laboratoryfodder quality traits and these in vivo measurements. Statistically highly significant and nutritionallyimportant differences were found between the stover with OMD differing by 15 percentage units and OMIand DOMI varying 1.6 and 2 times, respectively. For each of the in vivo measurements, chemical (NDF,ADF, ADL) and in vitro (in vitro digestibility, metabolisable energy content) traits were identified whichaccounted for at least 50% of the variation in the respective traits. Using multiple regression proceduresand stringent cross-validation (“blind-predictions”) procedures OMD, OMI and DOMI could be predictedwith R2 for comparing observed and predicted values of 0.36, 0.65 and 0.75, respectively. The reportedresearch showed selection for dual purpose sorghum cultivars is promising, and identified and validatedsimple laboratory traits that can be used for such phenotyping.Key words: Stover quality, Dual-purpose sorghum, Metabolisable energy.INTRODUCTIONSorghum stover plays an important part in the feed budget of Indian farmer’ whooften prefer dual-purpose type sorghums. This has resulted in sorghum improvementexploring ways of including stover fodder quantity and quality traits in breeding andselection (Reddy et al., 1995; Kelley and Rao, 1996). Such crop improvement requiressimple yet meaningful laboratory fodder quality traits to rank cultivars reliably for stoverquality. Many laboratory traits have been proposed by livestock nutritionist for fodder Animal Nutrition and Feed Technology (2010) 10S : 113-119*Reprint request: Dr. Ch. Ramkrishna Reddy, ILRI, Patancheru-502 324, India.114quality assessments, but validation of these indicators through actual livestock productivitytrials were limited, and often generally applied to the higher quality feedstuffs used inindustrialized livestock feeding. Basing dual-purpose crop improvement work on untestedlaboratory traits could clearly present a major set back to the breeding objective. Thepresent work therefore investigates the relationship between a wide range of chemicaltraits (nitrogen, NDF, ADF, ADL) and measurements of in vitro digestibility, metabolisableenergy content and extent and rate of in vitro gas production with the organic matterdigestibility, organic matter intake and digestible organic matter intake of 24 sorghumstovers fed ad libitum to sheep.MATERIALS AND METHODSSorghum stovers usedA total of 24 sorghum stovers obtained from 13 cultivars were evaluated. The totaltreatment numbers of 24 was arrived since some cultivars were grown in consecutiveyears and compared when grown sole and when intercropped. In addition, stover fromthree cultivars was purchased from different fodder traders at different times.Feeding trialsMale growing Deccani sheep of mean live weight of about 20 kg were used forthe in vivo experiments. The sheep were housed in metabolic cages with provision formeasurement of feed intake and faecal collection for feed digestibility measurements.Each stover was fed to six sheep randomly allocated according to body weight (sheepgroups were balanced according to live weight). The sheep were accustomed to a stoverfor a minimum of two weeks, followed by a 10-days faecal collection period for estimationof digestibility. All chopped stovers were offered as sole feed about 15% above theappetite. In other words sheep were allowed to refuse about 15% of the stover offered,which is the most common norm when investigating voluntary (ad libitum) feed intake.Laboratory stover quality analysisStovers were analyzed for nitrogen (N x 6.25 equals crude protein), neutral detergentfiber (NDF), acid detergent fiber (ADF) and acid detergent lignin (ADL) by routinechemical analytical procedures (Goering and Van Soest, 1970). As biological laboratoryfodder quality traits, stovers were analyzed for apparent in vitro digestibility using invitro gas production procedures according to Menke and Steingass (1988) and for truein vitro digestibility using the gravimetric procedure of Goering and Van Soest (1970).Extent, rate and lag phase of in vitro fermentation kinetics was determined using in vitrogas production test as described by Blümmel and Ørskov (1993).Statistical analysisThe statistical package of SAS (1988) was used for analysis of variance (SASGLM Procedure), for simple correlations between laboratory traits and in vivomeasurements and for stepwise multiple regressions between laboratory traits and in vivomeasurements using an entry level of P≤0.05. SAS cross validation procedures wereReddy et al.115used for predictions of in vivo variables where observations from the treatment to bepredicted are not used in the development of the regression equation.RESULTS AND DISCUSSIONResponses of sheep to different sorghum stoverAs shown in Table 1, stover differed significantly in organic matter digestibility(OMD), and intake (OMI), nitrogen balance and digestible organic matter intake (DOMI).(When these in vivo measurements were calculated for only one stover per cultivar– theone first fed - the statistical differences were of the same order (results not shown). Theranges in the measurements reported in (Table 1) are substantial. For example in breedingprogram with forage grasses a difference in 4 to 5 percentage units in in vivo digestibilityresulted in 17 to 24% difference in livestock productivity (Vogel and Sleper, 1994).When surveying price: quality relationships in sorghum stover trading Blümmel and Rao(2006) observed that a 5% difference in in vitro digestibility (47 to 52%) was associatedwith a price difference of about INR 1 per kg dry sorghum stover (INR 4 vs INR 3).For comparison the difference in in vivo digestibility observed in the sorghum stoverswas about 15 percentage units (Table 1). Similarly, DOMI which is closely related tolivestock performance in cereal crop residue fed livestock (Blümmel et al., 2003), variedby more than 1.6-fold. Stover quality differences of this magnitude will have substantialimplication for livestock productivity. From nitrogen balances in sheep (Anandan et al.2009) it can be extrapolated that on sorghum stover a DOMI of 10.7 g/kg LW /d sufficesfor maintenance requirement of the animal. Applied to the data in Table 1 (which arereported relative to metabolic weight) a DOMI of about 22 to 23 g / kg LW0.75/d wouldprovide maintenance requirements to livestock. This figure is close to the mean DOMIobserved in the current work, suggesting that sorghum stovers could also provide someenergy for milk and meat production in addition to maintenance requirements. In factsorghum, stover are the most highly priced cereal crop residues traded in India (Teufelpersonal communication).Laboratory traits for estimating sorghum stover fodder qualityCorrelations between laboratory fodder quality traits and OMD, OMI and DOMIare presented in Table 2. In general laboratory traits were significantly related to OMD,Table 1. Mean values and ranges in organic matter digestibility (OMD) and intake (OMI) and digestibleorganic matter intake (DOMI) in 24 sorghum stovers fed ad libitum to sheepParameter Mean Range Probability LSD1OMD (%) 56.5 46.0 to 65.1 <0.0001 3.3OMI (g/kg W0.75/d) 44.6 35.1 to 56.8 <0.0001 5.55DOMI (g/kg W0.75/d) 25.4 16.3 to 33.0 <0.0001 3.21 LSD: Least significant difference.Improvement of dual-purpose sorghum116OMI and DOMI. Mostly relations between laboratory traits and in vivo measurementswere as expected in that nitrogen content and in vitro digestibility measurements werepositively associated with OMD, OMI and DOMI while fiber constituents (NDF, ADFand ADL) were significantly negatively associated with OMD, OMI and DOMI. Timeand analytical inputs required for the various traits listed in (Table 2) are quite different.For example nitrogen, NDF and ADF are quite convenient for analyses while ADL(lignin) analysis demands first the ADF preparation which then has to be treated with72% sulphuric acid, washed, filtered, dried and ashed (Goering and Van Soest, 1970).Similarly, measurements of in vitro digestibility are easily obtained than in vitrofermentation kinetics (extent, rate and lag time measurements). In other word, ease ofmeasurement and predictive power of a laboratory traits need to be balanced. From thispoint of view, nitrogen, ADF and in vitro digestibility measurements seem to berecommendable laboratory traits for sorghum stover analysis (Table 2). These laboratoryTable 2. Correlation matrix between laboratory stover quality traits and organic matter digestibility(OMD) and intake (OMI) and digestible organic matter intake (DOMI)Parameters OMD OMI DOMISimple linear correlationsNitrogen 0.23 (0.29) 0.61 (0.002)  0.58 (0.003)NDF -0.60 (0.002) -0.48 (0.018) -0.61 (0.001)ADF -0.69 (0.0002) -0.77 (<0.0001) -0.84 (<0.0001)ADL -0.67 (0.0003) -0.66 (0.0004) -0.80 (<0.0001)ME  0.71 (<0.0001)  0.66 (0.0005)  0.78 (<0.0001)In vitro digestibility 0.69 (0.0002)  0.54 (0.007)  0.70 (0.0002)Extent of fermentation 0.55 (0.005) 0.72 (<0.0001) 0.70 (0.0001)Rate of fermentation 0.59 (0.002) 0.22 (0.29) 0.33 (0.11)Lag time of fermentation -0.46 (0.02) -0.46 (0.02) -0.49 (0.01)Cross validation proceduresNitrogen -0.02 (0.93) 0.52 (0.009) 0.51 (0.01)NDF 0.49 (0.015) 0.36 (0.08) 0.53 (0.008)ADF 0.58 (0.003) 0.73 (<0.0001) 0.81 (<0.0001)ADL 0.57 (0.003) 0.58 (0.002) 0.75 (<0.0001))ME 0.60 (0.002) 0.59 (0.002) 0.74 (<0.0001)In vitro digestibility 0.57 (0.0035) 0.42 (0.04) 0.61 (0.001)Extent of fermentation 0.27 (0.21) 0.67 (0.0003) 0.61 (0.001)Rate of fermentation 0.39 (0.06) -0.32 (0.13) -0.13 (0.53)Lag time of fermentation 0.25 (0.23) 0.31 (0.14) 0.35 (0.09)Reddy et al.117traits each accounted for more than 50% in the variation in DOMI, the most pertinentof the in vivo measurement listed in Table 2, and for example ADF accounted for 67%of the variation in DOMI. It is encouraging to see that the correlations between the keylaboratory traits and OMD, OMI and DOMI remained strong when used in cross validationprocedures, where the laboratory traits of the individual treatment to be predicted areexcluded from establishing the correlation. In other words, OMD, OMI and DOMI ofa given treatment are blind-predicted.Prediction of in vivo measurements by laboratory traits of sorghum stover couldbe improved through combination of traits in multiple regressions. For example 73% and80% of the variation in OMI and DOMI were accounted for by ADF in combination withnitrogen content (Table 3). The last model of the stepwise multiple regressions seemsto particularly suitable for reliably ranking of sorghum stover for fodder quality for tworeasons: 1) DOMI is a very pertinent in vivo measurement that is very closely relatedto milk and meat production and 2) ADF and nitrogen are simple and convenient tomeasure and to predict by Near Infrared Spectroscopy.Using the stepwise multiple regression models presented in (Table 3) in crossvalidation procedures in comparison to measured and predicted OMD, OMI and DOMIresulted in R2 of 0.36, 0.65 and 0.75, respectively (see figures 1a-c). The R2 for comparingmeasure and predicted OMD was weaker than in the cases of OMI and DOMI. Thereason for this is unclear, however when revisiting individual treatments 3 to 4 outlierscould be traced back to the stover obtained from the intercropping experiments. Also thesheep experimental data were obtained from a total of six different consecutive trials andexperimental conditions like season and temperature and animals varied which can haveaffected OMD, OMI and DOMI measurements. In this context the generally goodagreement between measured and observed OMI and DOMI is encouraging consideringaforementioned conditions and the stringent statistical analysis of cross validation applied.Table 3. Stepwise multiple regressions between stover laboratory quality traits and in vivo measurements(as in Table 1)X –Variables Y-Variable R2 ProbabilityModel: ME OMD 0.51 0.0001Step 1:ME 0.51 0.0001Model: Extent + Nitrogen OMI 0.73 0.0001Step 1: ADF 0.59 0.0001Step 2: Nitrogen 0.14 0.004Model: ADF + Nitrogen DOMI 0.80 0.0001Step 1: ADF 0.70 0.0001Step 2: Nitrogen 0.10 0.0003Improvement of dual-purpose sorghum118Fig. 1a. Relationship between measured and by cross validation predicted organic matter digestibilities(OMD)Fig. 1b. Relationship between measured and by cross validation predicted organic matter intakes (OMI)Fig. 1c. Relationship between measured and by cross validation predicted digestible organic matterintakes (DOMI)Reddy et al.119REFERENCESBlümmel, M. and Ørskov, E.R. 1993. Comparison of in vitro gas production and nylon bag degradabilityof roughages in predicting feed intake in cattle. Animal Feed Science and Technology, 40: 109-119.Blümmel, M., Zerbini, E., Reddy B.V.S., Hash, C.T., Bidinger, F.R. and Ravi, D. 2003. Improvingthe production and utilization of sorghum and pearl millet as livestock feed: methodologicalproblems and possible solutions. Field Crops Research, 84: 123–142.Blümmel, M. and Rao, P.P. 2006. Economic value of sorghum stover traded as fodder for urban andperi-urban dairy production in Hyderabad, India. International Sorghum and Millets Newsletter,47:97-101.Goering, H.K. and Van Soest, P.J. 1970. Forage fiber analyses (Apparatus, Reagents, Procedures andSome Applications). Agric. Handbook No 379, USDA-ARS, Washington, DC, USA.Kelley, T.G. and Rao, P. 1996. Availability and requirement of different sources of livestock feed inIndia with special reference to sorghum and millet straw. In: Global Agenda for Livestock Research,Proceedings of the Consultation for the South Asia Region, June 6-8, 1995, ICRISAT AsiaCenter, Patancheru, International Livestock Research Institute, Nairobi, Kenya, pp. 53-65.Menke, K.H. and Steingass, H. 1988. Estimation of the energy feed value obtained from chemicalanalysis and in vitro gas production using rumen fluid. Animal Research and Development, 28:7–55.Reddy, B.V.S., Hash, C.T., Stenhouse, J.W., Nigam, S.N., Singh, L. and Van Rheenen, H.A. 1995.Crop Improvement for Livestock Feed at ICRISAT ASIA Centre. In: Crop Improvement and itsImpact on the Feeding Value of Straw and Stovers of Grain Cereals in India (Eds. A. Seetharam,A. Subbarao, J.B. Schiere). Indian Council of Agricultural Research, New Delhi, India andDepartment of Tropical Animal Production Agricultural University, Wageningen, The Netherlands,pp. 85-90.SAS. 1988. Statistical Analysis System. SAS Institute Inc. Release 6.03 ed. Cary, New York, USA.Vogel, K.P. and Sleper, D.A. 1994. Alteration of plants via genetics and plant breeding. In: Foragequality Evaluation, and Utilization (Eds. J. George, and C. Fahey), American Society of Agronomy,Madison, Wisconsin, USA, pp. 891-921.Improvement of dual-purpose sorghum

Stover Quality Traits for Improvement of Dual-Purpose Sorghum

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Stover Quality Traits for Improvement of Dual-Purpose Sorghum

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