Brown Midrib Sorghum Research Articles

Growth rate of weaned lambs grazing brown midrib sorghum (Sorghum bicolor) supplemented with increasing levels of soybean meal

The aim of the present study was to describe the relationship between increasing levels of soybean meal (SBM) supplementation and the growth rate of weaned lambs grazing brown midrib (BMR) sorghum. Sixty Corriedale weaned lambs (3 months old) were divided into 12 homogeneous groups and allocated into three blocks of BMR sorghum (stocking density: 50 lambs/ha) of four plots each. In each block, lambs were assigned (5 lambs/plot.block) to one of the following treatments: grazing sorghum, grazing sorghum + 115 g SBM/lamb.day, grazing sorghum + 230 g SBM/lamb.day, and grazing sorghum + 345 g SBM/lamb.day. Rotational grazing management was implemented. Lambs were weighed at the beginning of the experiment. Final bodyweight and average daily gain (ADG) were analysed according to a completely randomised block design. The relationship between SBM supplementation level and ADG was tested and a non-linear fit with a prediction model of first-order kinetics was determined. Supplemented lambs had a higher (P < 0.036) final bodyweight and presented higher (P < 0.001) ADG than did non-supplemented lambs (31 kg and 120 g/lamb.day vs 26 kg and 55 g/lamb.day in supplemented and non-supplemented lambs, respectively). An asymptotic ADG value estimated by the model of 143.26 g/lamb.day BMR sorghum appeared to be an adequate summer grazing alternative for weaning lambs. SBM supplementation would improve the performance of animals however the level of supplementation would depend on the productive goal.

Sorghum bmr6 mutant analysis demonstrates that a shared MYB1 transcription factor binding site in the promoter links the expression of genes in related pathways

Sorghum is not only an important cereal crop but also a biofuel crop. The sorghum brown midrib mutant 6 (bmr6) has a reduced lignin content in the cell walls and vascular tissues, which could potentially be advantageous for cellulosic biofuel production. Meanwhile, both dry matter yield and plant height were decreased in the bmr6 mutant. To identify genes affected in the mutant, differential gene expression analysis was performed for bmr6 and the wild type. As a result, a total of 1,052 differentially expressed genes were detected between the two samples, of which 166 genes were downregulated and 886 genes were upregulated. Five hundred seventy-nine of the 1,052 differentially expressed genes could be assigned to 154 documented pathways. These pathways mainly included primary and secondary metabolism. Therefore, mutation of the bmr6 gene, which impaired the biosynthesis of lignin, ultimately affected the expression of these genes associated with the growth and development of sorghum. Except for the bmr6 gene, 11 key enzyme genes of monolignols biosynthesis were upregulated. Promoter analysis identified that these genes have common MYB sites. It revealed that a feedback mechanism existed in the pathway and a MYB1 transcription factor (Sb02g031190) could associate with the upregulation of these genes in sorghum. In this study, we investigated gene expressions at a global level in sorghum bmr6 mutant and provided valuable insights into the mechanisms of lignin biosynthesis.

Waste Streams from Methane Digesters: Exporting Nutrients through Turfgrass and Forage Production Systems

Similar to manure, residual manure solids (MS) from methane digesters require cropping systems and management practices that optimize nutrient export to prevent large increases in soil P levels. The objectives were to compare forage and turfgrass sod production systems with respect to effects of MS management practices on soil properties and crop productivity and to compare mass balance of N and P on field scale. A 2‐yr field experiment was conducted on a fine sandy loam soil receiving MS to compare nutrient imports, forms in soil, and export by Tifton 85 bermudagrass (Cynodon spp.) grown for forage and Tifway bermudagrass [C. dactylon (L.) Pers. × C. transvaalensis (Burtt‐Davy)] grown for turfgrass sod. Five soil treatments for each crop included MS with and without Alum topdressed (250 kg total phosphorus [TP] ha−1) annually or a single application of MS (500 kg TP ha−1) incorporated compared to soil without MS. One harvest of Tifway sod removed 2.7 times more total nitrogen (TN) and 2.8 times more TP than three harvests of Tifton 85 forage biomass during the first year of production. Greater biomass production and nutrient uptake by Tifton 85 forage during the second production season reduced the difference in nutrient export between Tifton 85 and Tifway sod. Turfgrass sod production systems can be used by producers to increase export of MS applied nutrients compared to forage production and enable waste streams from methane digesters to be recycled.

Biological conversion assay using Clostridium phytofermentans to estimate plant feedstock quality

BackgroundThere is currently considerable interest in developing renewable sources of energy. One strategy is the biological conversion of plant biomass to liquid transportation fuel. Several technical hurdles impinge upon the economic feasibility of this strategy, including the development of energy crops amenable to facile deconstruction. Reliable assays to characterize feedstock quality are needed to measure the effects of pre-treatment and processing and of the plant and microbial genetic diversity that influence bioconversion efficiency.ResultsWe used the anaerobic bacterium Clostridium phytofermentans to develop a robust assay for biomass digestibility and conversion to biofuels. The assay utilizes the ability of the microbe to convert biomass directly into ethanol with little or no pre-treatment. Plant samples were added to an anaerobic minimal medium and inoculated with C. phytofermentans, incubated for 3 days, after which the culture supernatant was analyzed for ethanol concentration. The assay detected significant differences in the supernatant ethanol from wild-type sorghum compared with brown midrib sorghum mutants previously shown to be highly digestible. Compositional analysis of the biomass before and after inoculation suggested that differences in xylan metabolism were partly responsible for the differences in ethanol yields. Additionally, we characterized the natural genetic variation for conversion efficiency in Brachypodium distachyon and shrub willow (Salix spp.).ConclusionOur results agree with those from previous studies of lignin mutants using enzymatic saccharification-based approaches. However, the use of C. phytofermentans takes into consideration specific organismal interactions, which will be crucial for simultaneous saccharification fermentation or consolidated bioprocessing. The ability to detect such phenotypic variation facilitates the genetic analysis of mechanisms underlying plant feedstock quality.

Composición química y cinética de degradabilidad de ensilaje de maíz convencional y sorgo de nervadura café

The chemical composition, dry mater and neutral detergent fiber digestibility and fermentation kinetics of the “33J56” and “Virgi” corn hybrids, and “Silo miel” and “Gigante verde” brown midrib sorghum varieties were compared. The corn hybrids were harvested at half milk line and sorghum varieties in soft dough stage, were ensiled in laboratory silos (n=3). After 45 d of fermentation, the laboratory silos were opened and analyzed for pH, DM, OM, ash, CP, EE, NDF, ADF, ADL, ME, IVDMD, IVNDFD and fermentation kinetics. No differences (P > 0,05) were observed in chemical composition between forage sources, except in NDF and ADF content, both were low (P < 0,05) in corn silage. GP at 72 h of incubation, fermentation parameters (A y C), fractional rateof degradation (R), time at which R is maximal (tRM) were similar (P > 0,05) between forage sources. The fermentation parameter B was different (P < 0,05) between forage sources and between corn hybrids.

Stalk strength and reaction to infection by Macrophomina phaseolina of brown midrib maize ( Zea mays) and sorghum ( Sorghum bicolor)

Reduced lignin concentration in brown mid-rib mutants in both maize and sorghum have resulted in improved dry matter digestibility, increased milk yield and higher energy in lactating cows. However, the mutations were not widely deployed due to concern that reduced lignin concentration might increase vulnerability to lodging and stalk rot incidence. The objective of this study was to determine the effects of the mutations on stalk strength and stalk rot resistance in both sorghum and maize. Six brown midrib ( bmr) sorghum, four brown midrib ( bm) maize, and their normal isolines were evaluated for stalk strength and stalk rot disease reaction at two locations in four replications. Three randomly selected plants in each plot were inoculated with Macrophomina phaseolina at 14 d after flowering by using the toothpick inoculation technique. On 28 d after inoculation, the plants were rated for disease severity by measuring the length of necrotic lesions in the stalks. Stalk strength was determined from another three random plants in each plot by using a rind penetrometer. The mutations had no effect on stalk rot disease severity in either sorghum or maize though stalks strength was markedly affected by the mutations in both species. While maize bm entries broke easily in response to mild mechanical stress, bmr sorghums did not exhibit sign of stalk collapse in all backgrounds. The result suggests that the bmr genes in both maize and sorghum can be deployed without incurring losses to stalk rot disease.

Evaluation and Characterization of Sorghum Biomass as Feedstock for Sugar Production

Conversion of cellulosic biomass, such as agricultural residues, to biofuels offers significant economic, environmental, and strategic benefits. Sorghum is an important energy crops in the U.S. It is a renewable resource and is currently grown on about 10 million acres in the U.S. However, at present, there is a lack of scientific information and knowledge about the use of sorghum biomass for biofuel production. The objective of this research was to evaluate and characterize sorghum biomass as a feedstock for sugar production. Five types of sorghum biomass (brown midrib sorghum, forage sorghum, grain sorghum, photoperiod-sensitive sorghum, and sweet sorghum) were characterized and evaluated for sugar production. Pretreatment with dilute acid was used to increase yield of fermentable sugars. Effects of sulfuric acid concentration, treatment temperature, and residence time on yield of fermentable sugars were studied. Accellerase 1000 was used to hydrolyze cellulose into glucose at 50C and pH 4.8 for 96 h. A high percentage of enzymatic conversion of cellulose (ECC) was observed for sorghum biomass that was pretreated under severe pretreatment temperature (85% to 98% ECC for biomass pretreated at 165C for 10 min; 65% to 82% ECC for biomass pretreated at 140C for 30 min). However, mass recovery and cellulose recovery of the solid fraction after pretreatment decreased under severe pretreatment conditions (70% to 85% cellulose recovery for sorghum biomass pretreated at 140C for 30 min; 31% to 58% cellulose recovery for sorghum biomass pretreated at 165C for 10 min).

Brown midrib forage sorghum silage for the dairy cow: nutritive value and comparison with corn silage in the diet

Rumen dry matter and fibre digestibility of brown midrib (BMR) sorghum forage silage (SF) in comparison to corn silage (CS) was determined in situ using 3 fistulated dry cows. The effect of replacing CS with SF on milk production was studied in a change-over design with 58 lactating Italian Friesian cows fed two diets with similar composition. CS had a higher (P<0.001) rapidly degradable dry matter (DM) fraction than SF (33.1 vs. 23.7, respectively), whilst the slowly degradable fraction was not different (46.3 vs. 48.7). Overall, the extent of DM rumen degradability was higher for CS.Rumen digestion rate of neutral detergent fibre (aNDFom) tended to be higher (P=0.06) for SF than CS (3.08 vs. 2.49 %/h, respectively); however, effective rumen degradability of fibre was not different between silages.Neither milk yield (kg/d) and 4%-fat corrected milk nor milk protein and fat contents were affected by treatment. Cows fed CS diet had lower (P<0.05) milk urea content compared with their SF counterparts (19.9 vs. 21.5 mg/dL) suggesting a better nitrogen utilization at the rumen level. In conclusion, feeding a BMR sorghum forage resulted in milk yield and quality similar to corn silage. However, to obtain comparable milk production as corn silage, the SF-based diet had to be supplemented with more starch from corn meal.

Performance of Forage Sorghum‐Legume Mixtures in Southern High Plains, USA

Forage sorghum [Sorghum bicolor (L.) Moench] and sorghum & sudangrass (S. bicolor var Sudanese) hybrids may produce as much dry matter yield as corn (Zea mays L.) for silage but with less water. Planting sorghum forage with annual legumes could increase digestibility and crude protein (CP) concentration, making the mixture more suitable for dairy cow rations. The objective of this study was to assess dry matter (DM) yield and nutritive value of brown midrib (BMR) sorghum forage grown as a monoculture or in combination with selected annual legumes. BMR100 (a forage sorghum) and PS210BMR (a photoperiod sensitive sorghum & sudangrass) were planted with four annual legumes: cowpea [Vigna unguiculata (L.) Walp.], lablab (Lablab purpureus L.), soybean (Glycine max L.), and tepary bean (Phaseolus acutifolius A. Gray). Lablab was most complementary with sorghum for forage. The lablab-sorghum mixtures contained more CP with no consistent effect on neutral detergent fiber (NDF) and acid detergent fiber (ADF) compared to monoculture sorghums. This finding opens another possibility to produce good quality forage that could be used as an alternative forage crop to corn in the Southern High Plains.

Nitrogen Management of Brown Midrib Sorghum × Sudangrass in the Northeastern USA

Brown midrib (BMR) forage sorghum [Sorghum bicolor (L.) Moench.] × sudangrass (Sorghum sudanense Piper) hybrids (S × S) have been considered as a possible forage alternative to maize silage (Zea mays L.) where maize planting is delayed due to wet soil conditions. Our objective was to determine the most economic rate of nitrogen (MERN) for BMR S × S grown in a two‐cut management system with a split application of N. Six field trials were conducted in New York in 2003 and 2004. One trial followed a grass–legume sod; a second trial had received liquid manure 19 mo before S × S planting. The remaining four followed S × S, silage maize, and/or a small grain crop. The MERN ranged from 137 to 192 kg N ha−1 cut−1 with dry matter (DM) yield ranging from 7.8 to 9.7 Mg ha−1 at the sites without additional N input. At the sites with prior N inputs, yield was higher (10.4–13.8 Mg ha−1) and MERN lower. The apparent nitrogen recovery (ANR) at the MERN was highest (61–73%) for the sites with prior N inputs. Nitrogen application rates &gt; 145 kg N ha−1 cut−1 decreased nitrogen use efficiency (NUE) to &lt;15 kg DM kg−1 N, while the ANR became &lt;45%. We concluded that the MERN for BMR S × S grown in New York in a two‐cut system following maize, small grains, or forage S × S is 125 to 145 kg N ha−1 cut−1. For sites that follow sod plow‐down or recent manure application, N application rates should not exceed 40 to 60 kg N ha−1 cut−1

Nitrogen, Phosphorus, Potassium, Magnesium and Calcium Removal by Brown Midrib Sorghum Sudangrass in the Northeastern USA

AbstractFor the long‐term sustainability of the dairy industry in the Northeastern USA, manure nutrient application rates should not exceed crop nutrient removal once above‐optimum soil fertility levels are reached. Dairy producers have shown a growing interest in brown midrib (BMR) forage sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (S × S) as a more environmentally sound alternative to maize (Zea mays L.) but data on S × S nutrient removal rates are scant. Our objectives were to determine N, P, K, Ca and Mg removal with harvest as impacted by N application rate, using six N rate studies in New York. One of the six sites had a recent manure history. Although site‐to‐site differences existed, N application tended to decrease P and K and increase N, Ca and Mg concentrations in BMR S × S forage. Nutrient removal and yield were highly correlated for all sites except one location that showed a K deficiency. The crop removed large amounts of P and K in the manured site, suggesting that BMR S × S is an excellent scavenger of these nutrients. If manure is applied mid‐season, forage K levels are likely too high for feeding to non‐lactating cows.

Field yield, ensiling properties and digestibility by sheep of silages from two forage sorghum varieties

This study examines the yield, composition, digestibility and ensiling properties of the new sorghum brown-midrib hybrid BMR-101. The commercial forage sorghum FS-5 was used as a reference variety. Forages were grown in a typical Mediterranean climate in five replicate plots, irrigated with 250 mm water, combine harvested at the soft dough stage and ensiled under both laboratory and commercial conditions. Both varieties were tall (>2.0 m). The dry matter (DM) content at harvest of FS-5 was higher than that of BMR-101 (296 g/kg forage versus 255 g/kg forage, P<0.05). BMR-101 plants suffered from higher lodging than FS-5 plants (60% versus 16.7%, P<0.05). Dry matter (DM) yield of the green forage was higher for FS-5 than BMR-101 (12.1 t/ha versus 9.89 t/ha, P<0.05). The distribution of DM among plant organs was similar for the two varieties, which contained also similar levels of neutral detergent fiber (aNDFom, 560–563 g/kg DM). BMR-101 raw plants had higher content of crude protein (CP) and hemicellulose and lower content of water-soluble carbohydrate (WSC), cellulose and lignin than FS-5 plants. Ensiling of the two varieties in glass silos resulted in moderate DM losses (<0.08 of yield) mostly as volatile gases, solubilisation of 0.04–0.12 hemicellulose, and high conversion of WSC mostly into lactate, ethanol and acetate. Ensiling in large scale bunker silos resulted in more extensive fermentation of WSC and lactate into acetate and ethanol, but in similar low pH (<4). In vitro DM digestibility of the two silages was similar, but in vitro NDF digestibility was higher for BMR-101 silage than FS-5 silage (P<0.05). Eight Assaff rams were assigned randomly into two dietary groups of four rams each and fed the two silages in a 2 × 2 crossover design. Intake and digestibility by sheep of silage DM and CP were similar for both varieties. Digestibility of silage NDF, cellulose and hemicellulose was higher for sheep fed BMR-101 as compared with FS-5 (P<0.05). The production of digestible silage DM was calculated to be higher for FS-5 than BMR-101 (7.14 t/ha versus 6.13 t/ha, P<0.05). These data highlight the advantages of commercial FS-5 relative to the new BMR-101 variety: its better resistance to lodging and higher production of silage DM and digestible DM per ha.

Potassium Management for Brown Midrib Sorghum × Sudangrass as Replacement for Corn Silage in the North‐eastern USA

AbstractIn recent years, there has been a growing interest in brown midrib (BMR) sorghum (Sorghum bicolor (L.) Moench.) × sudangrass (Sorghum sudanense Piper) hybrids (SxS) as a replacement for silage corn (Zea mays L.) in the north‐eastern USA. Recent studies suggest it is suitable for both rotational grazing and as a hay crop and could compete with corn harvested for silage in years when wet spring conditions prevent the timely planting of corn. However, little is known about its suitability as forage for non‐lactating cows that require low potassium (K) forages to prevent health problems. Our objective was to evaluate the impact of K fertilizer management (0, 112 or 224 kg K2O ha−1 cut−1) under optimum N management (112–168 kg N ha−1 cut−1) on yield, quality and K concentrations of BMR SxS over a 2‐year period. Field trials were established on a fine loamy, mixed, active, mesic Aeric Fragiaquepts with medium K‐supplying capacity and characteristic of a large region in New York. Potassium application did not affect dry matter yields in either of the 2 years. Averaged over 2 years, neutral detergent fibre (NDF) significantly increased with K addition with similar but non‐significant trends observed in each of the years individually. The digestibility of NDF was unaffected by K application. Crude protein (CP) concentrations showed a significant decrease with K application in 2002 and similar trends were observed in 2003, although differences were not significant at P ≤ 0.05. The changes in NDF and CP did not significantly impact forage quality expressed as milk production per megagram of silage. Potassium application increased forage K concentration up to 13 mg K kg−1 dry matter (in the first cut in 2003). Forage Ca and Mg concentrations decreased with K addition except for the first cut in 2002 where differences between 112 and 224 kg K2O ha−1 treatments were not significant. Without K addition in the 2‐year period, K concentrations in the forage decreased from 23 g kg−1 for the first cutting in 2002 to 15 g kg−1 for the second cut in 2003. Low K forage was obtained for all second‐cut forage unless 224 kg K2O ha−1 cut−1 had been added. First‐cut forage was suitable only when no additional K had been applied. These results suggest low K BMR SxS forage can be harvested from initially high K soils without loss in dry matter yield as long as no additional K is added.

Optimum Stand Height for Forage Brown Midrib Sorghum × Sudangrass in North‐eastern USA

AbstractBrown midrib sorghum × sudangrass is attracting attention in the north‐eastern USA because of its ability to produce acceptable forage yields on marginal corn ground. Other potential advantages include conservation of soil on highly erosive ground, the possibility to spread manure mid‐summer (after first cutting) when runoff risk is minimal, greatly reduced needs for herbicides and the potential to reduce the importation of phosphorus onto the farm. Best management practices need to be developed to take full advantage of the crop in the north‐east. Seven field studies were conducted from 2000 to 2002 in four different agricultural regions in New York to determine the time of harvest optimum for yield and quality in one‐ to three‐cut management systems. Yield, rather than a change in forage quality indicators, was the key determining factor for estimated milk production. However, to prevent the shift from vegetative to reproductive growth (and associated decline in quality) and to better manage the amount of water at harvest, we recommend that in the north‐eastern USA brown midrib sorghum sudangrass be managed using a two‐cut system with harvest taking place when stand heights are about 125 cm or less.

A candidate-gene approach to clone the sorghum Brown midrib gene encoding caffeic acid O-methyltransferase.

The brown midrib (bmr) mutants of sorghum have brown vascular tissue in the leaves and stem as a result of changes in lignin composition. The bmr mutants were generated via chemical mutagenesis with diethyl sulfate (DES) and resemble the brown midrib (bm) mutants of maize. The maize and sorghum brown midrib mutants are of particular value for the comparison of lignin biosynthesis across different, yet evolutionarily related, species. Although the sorghum brown midrib mutants were first described in 1978, none of the Brown midrib genes have been cloned. We have used a candidate-gene approach to clone the first Brown midrib gene from sorghum. Based on chemical analyses of the allelic mutants bmr12, bmr18 and bmr26, we hypothesized that these mutants had reduced activity of the lignin biosynthetic enzyme caffeic acid O-methyltransferase (COMT). After a northern analysis revealed strongly reduced expression of the COMT gene, the gene was cloned from the mutants and the corresponding wild types using PCR. In all three mutants, point mutations resulting in premature stop codons were identified: bmr12, bmr18 and bmr26 are therefore mutant alleles of the gene encoding COMT. RT-PCR indicated that all three mutants express the mutant allele, but at much lower levels relative to the wild-type controls. Molecular markers were developed for each of the three mutant alleles to facilitate the use of these mutant alleles in genetic studies and breeding programs.

Genetic Variability in the Fodder Yield, Chemical Composition and Disappearance of Nutrients in Brown Midrib and White Midrib Sorghum Genotypes

Samples of eleven brown midrib (ICSU 96031, ICSU 93046, ICSU 96082, ICSU 96078, ICSU 96075, ICSU 95101, ICSU 96034, ICSU 96063, ICSU 45116, ICSA 93-3 and ICSA 3845 X 3816) and nine white midrib genotypes (ICSU 96050, ICSU 96030, ISU 95082, SSG 59-3, FSHI 93-1, FSHI 2219A X 3211, HC 171, ICSA 93-2 and ICSA 93-1) based on their phenotypic appearance were collected at 50 per cent flowering from the sorghum germplasm grown at Research farm of IGFRI, Jhansi. These genotypes were evaluated with respect to crude protein, fiber composition, in-sacco dry matter, OM, cell wall components disappearance/digestibility besides the fodder yield, total phenolic and availability index values. Brown midrib genotypes were lower (p 0.05) differences were observed in dry matter, crude protein and organic matter contents between brown midrib and white midrib genotypes. Phenolic contents were significantly (p 0.05) differences between genotypes in extent of fiber fraction degradability though in-sacco NDF and ADF degradability was more by 5 and 4 units, respectively in brown midrib genotypes vis-a-vis white midrib genotypes. Average fodder yield (green and dry g/plant) and availability index (%) values were significantly (p<0.05) higher for brown midrib (474.2, 129.8 and 80.4) genotypes than white midrib (375.0, 104.8 and 69.2) genotypes. Lignin contents had significant negative correlation with DM, OM, NDF and ADF degradability. The results of the study revealed that brown midrib genotypes are superior not only with regard to chemical entities and disappearance of DM and fiber fractions but also better in respect of fodder yield and availability index values. Thus, brown midrib sorghum strains may be useful in increasing digestibility, intake, feed efficiency and animal performance. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 9 : 1303-1308)

Evidence for an evolutionarily conserved interaction between cell wall biosynthesis and flowering in maize and sorghum

BackgroundFactors that affect flowering vary among different plant species, and in the grasses in particular the exact mechanism behind this transition is not fully understood. The brown midrib (bm) mutants of maize (Zea mays L.), which have altered cell wall composition, have different flowering dynamics compared to their wild-type counterparts. This is indicative of a link between cell wall biogenesis and flowering. In order to test whether this relationship also exists in other grasses, the flowering dynamics in sorghum (Sorghum bicolor (L.) Moench) were investigated. Sorghum is evolutionarily closely related to maize, and a set of brown midrib (bmr) mutants similar to the maize bm mutants is available, making sorghum a suitable choice for study in this context.ResultsWe compared the flowering time (time to half-bloom) of several different bmr sorghum lines and their wild-type counterparts. This revealed that the relationship between cell wall composition and flowering was conserved in sorghum. Specifically, the mutant bmr7 flowered significantly earlier than the corresponding wild-type control, whereas the mutants bmr2, bmr4, bmr6, bmr12, and bmr19 flowered later than their wild-type controls.ConclusionThe change in flowering dynamics in several of the brown midrib sorghum lines provides evidence for an evolutionarily conserved mechanism that links cell wall biosynthesis to flowering dynamics. The availability of the sorghum bmr mutants expands the germplasm available to investigate this relationship in further detail.

Producción, composición química y digestibilidad del forraje de sorgo x sudán de nervadura café en la región norte de México

Nunez HG, Cantu BJE. Tec Pecu Mex. 2000, 38(3)177-187. The objective was to evaluate forage yield, chemical composition and in vitro digestibility of a brown midrib and a normal sorghum x sudan varieties (Sorghum bicolor (L.) Moench x Sorghum sudanense) and their relationships to climatic factors in northern Mexico. Two experiments were initiated on April 19 and 23 of 1995 and 1996, respectively, at La Laguna Experimental Station located at Matamoros, Coah., Mex. The varieties were Genex (brown midrib) and SX-16 (control variety). Both materials were harvested four times each year when plants were at the boot stage or beginning of heading . The brown midrib sorghum x sudan had less height and dry matter yield than the control variety in most harvests (P<0.05). There was an interaction genotype x harvest x year (P<0.05) for crude protein. No interaction between genotype with year and/or harvests was found for in vitro digestibility. The brown midrib sorghum x sudan variety had greater in vitro digestibility than the control variety (P<0.05). However, the control variety had greater digestible dry matter per hectare than the brown midrib variety (P<0.05). Temperature, light and solar radiation affected yield and in vitro digestibility of both varieties (P<0.05). Climatic factors affected the relationships between neutral detergent fiber (NDF), acid detergent fiber (ADF) and lignin (ADL) with in vitro digestibility year to year (P<0.05). NDF, ADF or ADL are not adequate predictors of in vitro digestibility through years.

Brown midrib sorghum in diets for lactating dairy cows.

In Experiment 1, 16 Holstein cows were assigned to one of four diets in replicated 4 x 4 Latin squares with 4-wk periods to measure dietary effect on short-term lactational performance. Additionally, 3 fistulated cows were assigned to the same diets in a 3 x 4 Youden square design with 4-wk periods to measure ruminal rate and extent of fiber digestion, fractional passage rate of fiber, ruminal pH, and concentration of volatile fatty acids. Diets comprised 65% of brown midrib (BMR) forage sorghum, standard forage sorghum, alfalfa or corn silages and 35% concentrate. Experiment 2 was conducted with 30 Holstein cows in early lactation to evaluate the same BMR sorghum hybrid in a 10-wk study with 35.3% standard sorghum, BMR sorghum, or corn silages as dietary treatments. Milk production was significantly higher for brown midrib than for standard sorghum in Experiment 1. Ruminal pH and acetate to propionate ratio did not differ among diets. The fractional passage rate of silage was not significantly different among the forages. In situ extent of ruminal fiber digestion was significantly higher for BMR than for standard sorghum, but rate of fiber digestion was not different. Similarly, in Experiment 2, in vitro extent of fiber digestion was significantly higher for BMR sorghum than for standard sorghum. Dry matter intake and body condition score were not significantly different between cows fed BMR and standard sorghum, but cows fed BMR sorghum resulted in long-term milk production greater than cows fed standard sorghum and similar to cows fed corn silage.

Brown Midrib Sorghum Silage for Midlactation Dairy Cows

Brown midrib sorghum silage was compared with alfalfa, corn, and normal sorghum silages for its effect on performance, ruminal metabolism, and digestive kinetics of Holstein dairy cows in midlactation. Twelve cows averaging 90±5 DIM were assigned to one of four diets in replicated 4 × 4 Latin squares with 4-wk periods. Additionally, 3 ruminally fistulated cows (95±20 DIM) were assigned to the same diets in a 3 × 4 Youden square for measurement of ruminal characteristics. Diets were fed as isonitrogenous TMR that contained 65% silage DM basis). The DMI was greater for the corn and brown midrib sorghum (4% of BW/d) than for the alfalfa and normal sorghum diets (3.4% of BW/d). The brow midrib sorghum supported FCM production that was similar to that of cows on corn and alfalfa diets (25.8 kg/d), but cows fed normal sorghum produced less milk and fewer milk components. Source of silage had no effect on eating time, but rumination was least for the alfalfa diet. Ruminal pH and ammonia concentrations were similar for all diets. Total VFA concentrations were greatest for the corn and brown midrib sorghum diets. The brown midrib sorghum had greater in situ extent of ruminal NDF digestion than did the normal sorghum, which agreed with in vitro data. The brown midrib sorghum used in this experiment supported FCM production similar to the corn and alfalfa silages commonly fed to dairy cows in midlactation.