Endosperm Type Research Articles

Protein quality and endosperm modification of quality protein maize ( Zea mays L.) under two contrasting soil nitrogen environments

Quality protein maize (QPM) breeding involves the combined use of the opaque-2 ( o2) gene and the genetic modifiers of the o2 locus to develop cultivars with modified kernel endosperm, and increased concentrations of lysine and tryptophan. This study was designed to assess grain yield performance, endosperm modification, and protein quality and quantity under two contrasting soil nitrogen environments. A 15-parent diallel cross was evaluated under one low nitrogen stress and one optimal nitrogen environment each at Harare (Zimbabwe) and Bako (Ethiopia). Most QPM hybrids showed higher protein quality levels than the best non-QPM check under both conditions. Protein concentration tended to vary across nitrogen levels, but not endosperm type. Significant differences were found for the test of main effect (nitrogen-level) for endosperm modification and tryptophan concentration. This indicated that QPM maintains quality even under low soil nitrogen, a widespread condition in Africa. General combining ability (GCA) mean squares were highly significant for most protein quality traits for each environment and across environments whereas specific combining ability (SCA) mean squares were not significant in most cases. This indicated that additive gene effects were primarily responsible for variation of most traits evaluated and hence progeny performance can adequately be predicted on the basis of parental performance. Inbred lines P2, P4 and P12 had desirable GCA effects for endosperm modification while P1 and P3 had the best GCA for tryptophan concentration in grain. The current study suggests that hybrids with desirable endosperm modification, protein quality and stable performance under low nitrogen stress and optimal conditions can be produced with careful selection.

Effect of Wet and Dry Fractionation Methods on Ethanol Production from Hard and Soft Endosperm Corn Types

Two corn fractionation methods, wet and dry, were compared to the conventional dry grind process using hard and soft endosperm corn types. Fractionation methods remove germ and pericarp fiber prior to fermentation. Wet fractionation involves soaking of corn and grinding, followed by germ and pericarp fiber removal. In dry fractionation, corn is tempered and passed through a roller mill before the germ and pericarp fiber are removed. Hard and soft endosperm types differ in the protein starch interactions, shape of starch granules, and type of proteins present. Effect of hard and soft endosperm on wet and dry fractionation processes and the conventional process were analyzed for final ethanol concentrations and fermentation rates. Germ from fractionation processes was analyzed for yield, oil, protein, and residual starch contents. Pericarp fiber yields, residual starch, and NDF contents were determined. Soft endosperm corn resulted in higher final ethanol concentrations (15.8%) than hard endosperm corn types (15.5%). Germ yields from hard endosperm corn were 1.8% higher than soft endosperm corn types. Pericarp fiber yields were higher from soft endosperm corn (10.8%) than from hard endosperm corn (8.35%). Among processes, wet fractionation resulted in 0.5% and 1.8% v/v higher final ethanol concentrations than dry fractionation and the conventional process, respectively. Germ yields were higher from dry fractionation (10.6%) than from wet fractionation (8.35%). Germ fractions from wet fractionation had higher oil (31.4%) and protein (14.2%) than germ from dry fractionation (18.8% and 12.6%, respectively). Dry fractionated germ had 6.9% more starch than wet fractionated germ. Pericarp fiber yields were higher from wet (11.4%) than from dry (7.21%) fractionation. Fractionation processes result in higher final ethanol concentrations and can provide valuable coproducts.

Effect of endosperm type on texture and in vitro starch digestibility of maize tortillas

Tortilla is the main staple of Mexico and it is made using diverse maize varieties, which have different endosperm types. Three maize varieties with vitreous, intermediate and floury endosperms were used. Texture and starch digestibility were evaluated in freshly prepared and stored tortillas for 24, 48 and 72 h. Tortilla made with maize of vitreous endosperm had the highest force to rupture and the lowest distance of elongation, indicating more rigid texture. Stored tortillas had lower available starch content and higher effect was shown by tortilla of vitreous endosperm, pattern that agrees with the higher increase in the resistant starch content with the storage time. Fresh tortilla of floury endosperm showed the highest hydrolysis rate during the first 15 min followed by tortillas of intermediate and vitreous endosperms. Starch hydrolysis values decreased when storage time increased, in agreement with the resistant starch content in the stored tortillas. At the longest storage time (72 h) tortilla of floury endosperm presented higher hydrolysis rate, followed by tortilla of intermediate and vitreous endosperms. The endosperm type plays an important role in the textural and starch digestibility of fresh and stored tortillas.

Embryological and cytochemical features of Scilla autumnalis L.

Nucellar epidermal cells in the micropylar region of Scilla autumnalis L. differentiate into a nucellar cap. It secretes a PAS-positive exudate filling the micropyle. A group of cells at the chalazal end of the nucellus forms a hypostase. Close to the antipodals, the hypostase cells contain abundant starch grains, suggesting a function as a storage tissue. Another ovular structure is the obturator. It secretes an exudate that stains deeply with PAS reaction, and it takes a role in directing the growth of pollen tubes toward the micropyle. Cytochemical tests in the mature embryo sac indicate the presence of high amounts of proteins, polysaccharides, and lipids in the cytoplasm of the egg, synergids, antipodals, and central cell, appearing to be the site of intensive synthetic activity. The presence of a PAS-positive wall completely surrounding the egg cell and synergids is an unusual feature worthy of mention. Antipodals undergo polytenisation to reach ploidy levels of up to 128n. Another embryological feature of S. autumnalis is the development of an Onagrad type of embryo and a helobial type of endosperm.

Maize (Zea Mays L) landraces from the southern region of Brazil: contamination by Fusarium sp, zearalenone, physical and mechanical characteristics of the kernels

This work had as objectives the study of the physical and mechanical characteristics of maize kernels in relation to the contamination by Fusarium sp and by zearalenone in twenty landraces of maize from the southern region of Brazil. From the analyzed samples, 60 % has been considered to have a hard endosperm type and 40 % an intermediary one. A correlation between the physical and mechanical variables was observed as an indication that the higher is the proportion of hard endosperm, more dense will be the kernel and more force for its rupture will be necessary. The level of contamination by Fusarium sp was between 5.5 and 24.75% among the analyzed grains, correlating positively with the flotation index, indicating that the landraces of maize with a softer endosperm can present a higher contamination by this genus. The presence of zearalenone was verified in 75 % of the samples, in concentrations varying from 50 to 640 µg kg-1.

Near Infrared Hyperspectral Imaging for the Evaluation of Endosperm Texture in Whole Yellow Maize (Zea maizeL.) Kernels

Near infrared hyperspectral images (HSI) were recorded for whole yellow maize kernels (commercial hybrids) defined as either hard, intermediate, or soft by experienced maize breeders. The images were acquired with a linescan (pushbroom) instrument using a HgCdTe detector. The final image size was 570 x 219 pixels in 239 wavelength bands from 1000 to 2498 nm in steps of approximately 6.5 nm. Multivariate image cleaning was used to remove background and optical errors, in which about two-thirds of all pixels were removed. The cleaned image was used to calculate a principal component analysis (PCA) model after multiplicative scatter correction (MSC) and mean-centering were applied. It was possible to find clusters representing vitreous and floury endosperm (different types of endosperm present in varying ratios in hard and soft kernels) as well as a third type of endosperm by interactively delineating polygon based clusters in the score plot of the second and fourth principal components and projecting the results on the image space. Chemical interpretation of the loading line plots shows the effect of starch density and the protein matrix. The vitreous and floury endosperm clusters were used to make a partial least-squares discriminant analysis (PLS-DA) model, using four components, with a coefficient of determination (R(2)) for the y data (kernel hardness category) for the training set of over 85%. This PLS-DA model could be used for prediction in a test set. We show how the prediction images can be interpreted, thus confirming the validity of the PCA classification. The technique presented here is very powerful for laboratory studies of small cereal samples in order to produce localized information.

Type of corn endosperm influences nutrient digestibility in lactating dairy cows

An experiment was conducted to evaluate the effect of type of corn endosperm on nutrient digestibility in lactating dairy cows. Near-isogenic variants of an Oh43×W64A normal dent endosperm hybrid carrying floury-2 or opaque-2 alleles were grown in spatial isolation in field plots and harvested as dry shelled corn. Six ruminally cannulated, multiparous Holstein cows (67±9 d in milk at trial initiation) were randomly assigned to a replicated 3×3 Latin square design with 14-d periods; the first 11 d of each period were for diet adaptation followed by 3 d of sampling and data collection. Treatment diets that contained dry rolled vitreous-, floury-, or opaque-endosperm corn [33% of dry matter (DM)], alfalfa silage (55% of DM) and protein-mineral-vitamin supplement (12% of DM) were fed as a total mixed ration. The percentage vitreous endosperm was zero for floury and opaque endosperm corns and 64±7% for the vitreous corn. Prolamin protein content of floury and opaque endosperm corns was 30% of the content found in vitreous corn. Degree of starch access and in vitro ruminal starch digestibility measurements were 32 and 42% greater on average, respectively, for floury and opaque endosperm corns than for vitreous corn. Dry matter and starch disappearances after 8-h ruminal in situ incubations were, on average, 24 and 32 percentage units greater, respectively, for floury and opaque endosperm corns than for vitreous corn. Ruminal pH and acetate molar percentage were lower, propionate molar percentage was greater, and acetate:propionate ratio was lower for cows fed diets containing floury and opaque endosperm corns than for cows fed vitreous corn. In agreement with laboratory and in situ measurements, total-tract starch digestibility was 6.3 percentage units greater, on average, for cows fed diets containing floury and opaque endosperm corns than vitreous corn. Conversely, apparent total-tract neutral detergent fiber (NDF) digestibility was lower for cows fed diets containing floury and opaque endosperm corns compared with vitreous corn. The type of endosperm in corn fed to dairy cows can have a marked effect on digestion of starch and NDF. Feeding less vitreous corn increased starch digestion but decreased NDF digestion.

Morphological fractions and <i>in vitro</i> fermentation characteristics of five endosperm types maize stover harvested at two maturity stages

Morphological fractions and <i>in vitro</i> fermentation characteristics of five endosperm types maize stover harvested at two maturity stages

A Common Genetic Basis for Cross-sensitivity to Mesotrione and Nicosulfuron in Sweet Corn Hybrid Cultivars and Inbreds Grown throughout North America

Mutation of a cytochrome P450 (CYP) gene on the short arm of chromosome five, referred to as nsf1 or ben1, conditions sensitivity to certain P450-metabolized herbicides in corn (Zea mays L.). Previous research has shown that the sweet corn inbred Cr1 is sensitive to nicosulfuron, mesotrione, and at least seven other P450-metabolized herbicides with five different modes of action. Although the nsf1/ben1 CYP gene has not been sequenced from Cr1, a QTL that conditions cross-sensitivity to P450-metabolized herbicides was detected in a segregating population of Cr1 × Cr2 (herbicide tolerant) on the short arm chromosome five in tight linkage disequilibrium with the nsf1/ben1 CYP locus. Sweet corn hybrid cultivars and inbreds that had been identified in previous research as being susceptible to injury from P450-metabolized herbicides were tested in this study to determine if they were allelic with Cr1 for cross-sensitivity to nicosulfuron and mesotrione. These cultivars and inbreds were developed by 12 independent commercial breeding programs. These cultivars include sugary, sugary enhancer, and shrunken-2 endosperm types that are grown for processing and fresh consumption in markets throughout North America and in other temperate climates throughout the world. Each hybrid cultivar, their F2 progeny, and progeny from testcrosses of cultivars with Cr1 and Cr2 were evaluated for responses to mesotrione and nicosulfuron. Each inbred line, progeny from crosses of inbreds with Cr1 and Cr2, and F2 progeny from crosses of inbreds with Cr1 were also tested. Based on segregation of progeny from testcrosses with Cr1 and Cr2 and the F2 generation, 45 sweet corn hybrid cultivars and 29 sweet corn inbreds, including lines from each of the 12 breeding programs, appeared to be sensitive to nicosulfuron and mesotrione as the result of a gene that is the same as or very closely linked to the gene in Cr1. None of the cultivars or inbreds appeared to be sensitive to these herbicides as a result of other independent genes; however, additional genes that modify responses to these herbicides may be present in a few cases. The presence of a gene conditioning sensitivity to nicosulfuron and mesotrione, and probably to several other P450-metablolized herbicides, provides an explanation for varied levels of injury and inconsistent responses of sweet corn hybrid cultivars under differing environmental conditions. This information provides a basis from which an industry-wide concern with herbicide sensitivity in sweet corn can be addressed by various methods, including the elimination of an allele rendering germplasm sensitive.

Technical Note: A Method to Quantify Prolamin Proteins in Corn That Are Negatively Related to Starch Digestibility in Ruminants

Compared with floury or high-moisture corns, dry corn with a greater percentage of vitreous endosperm has been demonstrated to be negatively related to starch digestibility and milk yield of lactating dairy cows. Starch granules in corn are encapsulated by hydrophobic prolamin proteins that are innately insoluble in the rumen environment. Corn prolamin proteins are named zein, and laboratory methods to quantify zein exist but are seldom employed in ruminant nutrition because of their arduous nature. In this study, advances in cereal chemistry were combined with rapid turbidimetric methods yielding a modified turbidimetric zein method (mTZM) to quantify zein in whole corn. Ten dry corns containing unique endosperms were evaluated using the mTZM. Corns with flint, dent, floury, or opaque endosperms were found to contain 19.3, 11.3, 5.8, and 4.9g of zein/100g of starch, respectively. The ability of mTZM to differentiate corn endosperm types as defined by least significant difference was 2.6g of zein/100g of starch. Ten high-moisture corns of varying moisture content were also evaluated using the mTZM. Zein content of high-moisture corns as defined by mTZM ranged from 8.3 to 2.8g of zein/100g of starch with a least significant difference of 1.2g of zein/100g of starch. The mTZM determined that zein contents of high-moisture, floury, and opaque corns were markedly less than those of flint and dent dry corns, indicating that mTZM has the ability to quantify starch granule encapsulation by hydrophobic prolamin proteins in whole corn.

Systematic Significance of the Development and Anatomy of Flowers and Fruit of Quercus schottkyana (Subgenus Cyclobalanopsis: Fagaceae)

The developmental process of flower and fruit production was studied for the first time in Quercus schottkyana (subgenus Cyclobalanopsis) and compared with other species of Quercus and related Fagaceae. Four main developmental periods were recognized, and standard embryological features such as basic type of anther wall formation, simultaneous cytokinesis of microspore mother cells, tetrahedrally arranged microspore tetrads, and two‐ to three‐celled pollen grains. Polygonum type of embryo sac development, delayed fertilization, and free nuclear endosperm were observed in Q. schottkyana and confirmed to be plesiomorphic. In Q. schottkyana, the primary archesporial cell divided into megaspore mother cells without forming a primary parietal cell, a condition that may be derived in Fagaceae. Another possibly derived state observed at an early ovule stage was a pseudocrassinucellate nucellus, defined by ovule epidermis giving rise to the subdermal layer (parietal layer) and archesporial cells directly developi...

Sweet Corn Growth and Yield Responses to Planting Dates of the North Central United States

Sweet corn is planted over a 3-month period in the north central United States to extend availability for fresh market and processing; however, the extent to which development and growth of sweet corn changes during this period is unreported. Field experiments were conducted in 2006 and 2007 to determine the effect of five planting dates, ranging from mid-April to early July, on sweet corn establishment, growth, and yield components. Day length at the time of silking decreased from 15.1 h in the mid-April planting to 13.7 h in the early July planting. Development took 13 to 25 fewer days from emergence to silking for the hybrid ‘BC0805’, an 82-day augmented sugar enhancer endosperm type, as planting was delayed from mid-April to early July. Maximum height generally increased through planting dates with as much as 23% taller plants in early July versus mid-April planted sweet corn. While leaf mass was unaffected by planting date, maximum leaf number and rate of leaf appearance steadily decreased with later planting dates. Lower reproductive and total biomass at silking as well as marketable ear yield components were lowest in the early July planting date and were associated with presence of maize dwarf mosaic virus in leaf samples. In response to environmental conditions, the crop canopy undergoes distinct morphological changes as planting is delayed, and those changes may have implications for crop production.

Physicochemical and Biochemical Characterization of Starch Granules Isolated of Pigmented Maize Hybrids

AbstractIn this study, the morphological and physicochemical of pigmented maizes as well as the initial characterization of the corresponding starch granule enzymes are described. Starch granules were isolated from blue, black, and white maize. They were analyzed using scanning electron microscopy, particle size distribution, pasting characteristics, sorption isotherms, differential scanning calorimetry, and two‐dimensional gel electrophoresis. The morphology of the starch granules of pigmented maizes was different from the granules of white maize; the pattern was related to the endosperm type of these varieties. The average starch granule size was higher for black than for white and blue maizes. The average gelatinization temperature was similar in the three starches, but the pigmented maizes had higher gelatinization enthalpy; black maize starch showed the lowest enthalpy of retrogradation. These results indicated that the starches from the three maizes analyzed had different organization level. Black maize starch showed the highest peak viscosity followed by white and blue maize starches. In the gel electrophoresis three starch granules presented one main spot at pI of 5 and MW of 60 kDa that corresponds to the granule‐bound starch synthase. Blue and white starches presented some spots near 97 kDa at pI of 5.3–5.7 (white maize) and 5.1–5.5 (blue maize), spots that were not observed for black maize starch. The morphological and physicochemical characteristics of maize starch are related to the enzymes involved in its biosynthesis.

Microtubules in early development of the megagametophyte of Ginkgo biloba

Food storage tissue in the seeds of gymnosperms is female gametophyte (megagametophyte) that develops before fertilization, whereas, in seeds of angiosperms, food is stored as endosperm initiated by double fertilization. The megagametophyte is haploid, and endosperm is usually triploid, at least initially. Despite differences in origin, ploidy level, and developmental trigger, the early events of female gametophyte development in ginkgo are very similar to nuclear endosperm development in the seeds of angiosperms. In both, development begins as a single cell that undergoes multiple mitoses without cytokinesis, to produce a large syncytium. This study provided evidence that microtubule involvement in organization of the syncytium into nuclear cytoplasmic domains (NCDs) via nuclear-based radial microtubule systems is a critical developmental feature in the ginkgo megagametophyte, as it is in endosperm. Once the initial anticlinal walls have been deposited at the boundaries of NCDs, cellularization proceeds by the process of alveolation. Continued unidirectional growth of the alveolar walls is an outstanding example of polar cytokinesis. Ginkgo megagametophyte development appears to occur uniformly throughout the entire chamber, whereas nuclear type endosperm usually exhibits distinct developmental domains. These observations suggest that there is a fundamental pathway for the development and cellularization of syncytia in seed development.

Degree of starch access: An enzymatic method to determine starch degradation potential of corn grain and corn silage

Starch supplied from corn grain or corn silage is an important source of dietary energy for lactating dairy cows and other ruminants, but few laboratory methods are available to determine starch digestion potential. A laboratory method, degree of starch gelatinization (DSG), commonly used by the food industry to assess relative differences in starch characteristics of human foods was modified for application to corn grain and corn silage. The modified assay, degree of starch access (DSA, g/kg starch), was used to evaluate starch recovery by enzymatic hydrolysis in gelatinized undried, unground corn grains and corn silages, which differed in particle size, dry matter content and endosperm type. Effects of particle size (370, 500, 640, 1100, 3140 and 4000 μm) of corn grains, which are known to influence starch digestion in ruminants, were evaluated. For each 100 μm increase in particle size, DSA decreased (P < 0.001) 26.8 g/kg starch. In high-moisture corn grain, for each 10 g/kg fresh matter increase in DM content, DSA decreased 20.0 g/kg starch ( r 2 = 0.76). In corn grain of differing endosperm vitreousness (0 g/100 g versus 100 g/100 g endosperm) DSA values were approximately 200 g/kg starch higher for corn grain with no vitreous endosperm as compared to corn grain with highly vitreous (100 g/100 g) endosperm. For corn silage, DSA was positively correlated to latent starch and starch retained on screens < 2.38 mm. While no comparisons between DSA and in vivo starch digestibility exist, the DSA assay may be useful as an index for evaluating differences in starch digestion potential of corn and corn silage fed to ruminants.

Priming Duration Influences Anatomy and Germination Responses of Parsley Mericarps

Germination studies indicated that increasing priming duration (-1.0 MPa at 20 °C for 7, 14, or 21 days) increased `Moss Curled' parsley [Petroselinum crispum (Mill.) Nyman ex A.W. Hill] germination rate quadratically and seed moisture content linearly. A histological and anatomical study was conducted to identify and/or quantify principle mericarp organ or tissue volume changes influenced by priming duration. Embryo volume increased as priming duration increased from 7 to 21 days (0.014 to 0.034 mm3), and this was due more to radicle (0.007 to 0.022 mm3) than to cotyledon (0.006 to 0.011 mm3) growth. Concomitant with increased embryo volume was increased volume of the depleted layer (space formation, surrounding the embryo), from 0.038 after 7 days to 0.071 mm3 after 21 days, and increased hydrolysis of central endosperm (a thick-walled endosperm type). In nonprimed mericarps, central endosperm cells constituted 97% of the endosperm volume. The remaining 3% was comprised of 1% depleted layer and 2% distal endosperm (small, thin-walled, and irregularly shaped endosperm cells). During 7 or 21 days of priming, ≈10% or 40%, respectively, of central endosperm cells were hydrolyzed centrifugally around the embryo with a corresponding decrease in volume of central endosperm with thick cell walls. In addition, distal endosperm cells adjacent to the depleted layer, containing reserve materials, were digested of contents following 21 days priming, and sometimes, following 7 days priming. A long priming duration resulted in degradation of pericarp tissues, as indicated visually and by a decline in pericarp volume. We hypothesize that priming duration of parsley primarily influences radicle growth and centrifugal digestion and utilization of central and distal endosperm, resulting in a larger depleted layer required for embryo volume increases. Secondary events influenced by priming duration include cotyledon growth and degradation of pericarp tissues.

Differential Response of Rice Germplasm to Straighthead Induced by Arsenic

Straighthead disease is a physiological disorder of rice (Oryza sativa L.) characterized by sterility of the florets leading to reduced grain yield. Knowledge of the straighthead response of new cultivars is important for producer control of this disease, and identification of resistant germplasm is essential for breeding improved cultivars. The objectives of this study were to characterize U.S. cultivar reactions to straighthead and search for resistant germplasm. Twelve lines, including 10 U.S. cultivars, a Chinese and Japanese cultivar, were tested for straighthead reaction induced by monosodium methanearsonate (MSMA) at 0, 6.7, and 9.0 kg ha−1 under nitrogen fertilizer of 0, 67, 134, and 269 kg N ha−1 in 1999 and 2000. Straighthead delayed heading date, shortened plant height, and dramatically reduced grain yield. Cocodrie, Mars, Kaybonnet, and Bengal were highly susceptible to straighthead with ratings from 7.2 to 8.0 and grain yield reductions from 80 to 96%. Wells, LaGrue, Drew, Cypress, and Japan 92.09.31 were susceptible with ratings from 5.9 to 6.7 and yield reductions from 49 to 73%. Priscilla and Jefferson were tolerant with ratings of 4.9 and 5.3, and yield reductions of 24 and 36%, respectively. The Chinese indica cultivar Zhe 733 was essentially immune to straighthead, showing neither symptoms nor detectable yield reduction. A total of 124 Chinese cultivars including 109 indica and 15 japonica were evaluated for straighthead resistance in 2001. Nineteen cultivars, 18 indica and 1 japonica, were identified as straighthead resistant. Grain yields of the resistant cultivars were not significantly reduced by their straighthead ratings of 1 to 3. Variation in yield, plant height, maturity, and endosperm type within the resistant germplasm was also observed.

Corn Grain Endosperm Type and Brown Midrib 3 Corn Silage: Site of Digestion and Ruminal Digestion Kinetics in Lactating Cows

Interactions of endosperm type of corn grain and the brown midrib 3 (bm3) mutation in corn silage on ruminal kinetics and site of nutrient digestion of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72±8 d in milk; mean±SD) were used in a duplicated 4×4 Latin square design experiment with a 2×2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber (NDF) and 30% starch. Interactions of treatments were not observed for any measure of digestibility, but digestion kinetics of starch and fiber did interact to affect digestible organic matter intake by affecting dry matter intake. Rate of ruminal starch digestion was faster and rate of ruminal starch passage tended to be slower in diets containing corn grain with floury vs. vitreous endosperm, resulting in a mean increase of 22 units for ruminal starch digestibility. Although compensatory postruminal starch digestion decreased differences among treatments for total tract starch digestibility, starch entering the duodenum was more digestible for grain with floury endosperm compared with vitreous grain, resulting in greater total tract starch digestibility for floury compared with vitreous corn grain. Fermentation rate of potentially digestible NDF was not affected by either bm3 corn silage or greater ruminal starch digestion of floury grain. Brown midrib corn silage increased total tract NDF digestibility vs. control silage by numerically increasing ruminal and postruminal digestibility of NDF. Endosperm type of corn grain greatly influences site of starch digestion and should be considered when formulating diets.

Corn Grain Endosperm Type and Brown Midrib 3 Corn Silage: Ruminal Fermentation and N Partitioning in Lactating Cows

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on ruminal fermentation and microbial efficiency of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72±8 d in milk; mean±SD) were used in a duplicated 4×4 Latin square design experiment with a 2×2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber and 30% starch. Increasing ruminal starch digestibility by replacing vitreous corn grain with floury grain reduced mean and minimum ruminal pH. Brown midrib 3 corn silage reduced mean and minimum ruminal pH and increased total volatile fatty acid concentration. Ruminal pH was positively associated with rate of valerate absorption. Although floury endosperm reduced acetate:propionate ratio in both control and bm3 corn silage diets, it had a greater effect on reducing acetate:propionate ratio for control silage compared with bm3 corn silage. Nonammonia N flow to the duodenum did not differ among treatments and no effects of treatment were detected for microbial N and nonammonia, nonmicrobial N flow. Although treatment effects on ruminal fermentation and ruminal pH were observed, few interactions of treatment were detected and treatments did not affect flow of N fractions to the intestines.

Corn Grain Endosperm Type and Brown Midrib 3 Corn Silage: Feeding Behavior and Milk Yield of Lactating Cows

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on feeding behavior, productivity, energy balance, and plasma metabolites of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72±8 d in milk; mean±SD) were used in a duplicated 4×4 Latin square design experiment with a 2×2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous), and corn silage type (bm3 or isogenic control). Diets contained 26% neutral detergent fiber (NDF) and 30% starch. Floury endosperm grain decreased dry matter intake (DMI) 1.9kg/ d compared with vitreous grain when combined with control corn silage but did not affect DMI when combined with bm3 corn silage. This interaction of treatments occurred because of changes in meal size; floury endosperm grain decreased meal size in control silage diets but increased meal size in bm3 corn silage diets. Ruminal pool sizes reflected DMI differences among diets, suggesting that ruminal fill was not the primary limitation on intake. Brown midrib 3 corn silage reduced rumination time per day and number of rumination bouts per day. Floury endosperm grain decreased 3.5% fat-corrected milk by 1.2kg/d when combined with control silage but increased 3.5% fat-corrected milk by 2.1kg/d when combined with bm3 corn silage. Starch and fiber digestibility interact to affect feeding behavior and milk production and production response to bm3 corn silage depends on the grain source that is fed.