Improved Reaction Conditions for Preparation of β-Cyclodextrin (β-CD) from Cassava (Manihot esculenta Crantz) Starch

Experimental conditions for bioconversion of starch to get higher yield of ß-cyclodextrin using cyclodextrin glycosyl transferase (CGT-ase) (EC 2.4.1.19) were worked out. A 5% initial starch concentration gave ß-CD yield of 20-28% that could be separated as ß-CD bromobenzene complex from the reaction mixture. Addition of bromobenzene during the second phase of the reaction, i.e. CD formation phase, was found beneficial.     

Production of Maltose from Starch by Simultaneous Action of beta-Amylase and Flavobacterium Isoamylase

Debranching isoamylase was prepared by fermentation of Flavobacterium sp., and purified. Soybean ß-amylase was extracted from defatted soybean meal and purified. 1.6, 4.0, 6.6. and 9.1% DE liquefied corn starch was prepared by bacterial α-amylase. The mixture of liquefied starch. Flavobacterium isoamylase, and soybean ß-amylase was incubated at 40 C, pH 6.0, for 46 h. The maximum yield of hydrolysates from 1.6 and 4.0% DE substrates was maltose, and a considerable amount of maltotriose, but no detectable glucose. 6.6 and 9.1% DE substrates also produced largest amounts of maltose with moderate maltotriose, and small amounts of glucose also formed during hydrolysis. With the increase of DE of the substrate the yield of maltose decreased and the yield of glucose and maltotriose increased.     

Raw Starch Digestion by Bacillus polymyxa beta-Amylase

Unlike plant ß-amylases, Bacillus polymyxa ß-amylase digests raw starch at a significant rate. The action of this bacterial ß-amylase on raw starch is stimulated greatly by the presence of the debranching enzyme pullulanase.     

The Production and Properties of Glucose Syrups I. Production of Glucose Syrups by Enzymatic Hydrolysis of Starch

Certain metal ions are shown to influence the enzymic hydrolysis of maize starch. Amyloglucosidase was not affected by the metal ions but á- and ß-amylase were affected by varying degrees. Calcium ions produced a positive effect with both fungal and bacterial α-amylases but no effect with ß-amylase, whilst zinc, ferric and lead ions produced negative effects or no effect. A simultaneous enzymic hydrolysis (using α- and ß-amylases) and catalytic hydrogenation showed enzyme inhibition by the nickel catalyst. High hydrogen pressure (100 at) had little effect on the enzymes. The hydrolysis and hydrogenation of the starch fraction of milled whole defatted maize was also shown to be feasible.     

Effects of enzymically modified amylopectin on the rheological properties of amylose-amylopectin mixed gels

Branched α-dextrins with different molecular weights were prepared from waxy maize. A series of β-limit dextrins was prepared from α-dextrins and native amylopectin. The fine structure of the dextrin samples was investigated by debranching, and was found to be similar to the unit chain distribution of native amylopectin. The absolute molecular weights of α- and β-limit dextrins and commercial potato amy lose were determined by gel-permeation chromatography (GPC) and with a dual light-scattering detector. Solubilized potato amy lose and α- and β-limit dextrins were mixed at different ratios to give a total concentration of 8%. Dynamic viscoelastic measurements showed that gel formation of amylose was highly dependent both on the ratio of amylose to α-dextrin and on the molecular weight of α-dextrin. α-Dextrin caused an increase of storage modulus, G, when the amylose: α-dextrin ratio was low and the molecular weight of α-dextrin was high. The high-molecular-weight α-dextrin influenced amylose gelation in the same way as native waxy maize starch, but the medium- and low-molecular-weight α-dextrins weakened the gel formation, especially at a ratio of 25:75 (amylose: α-dextrin). When low-molecular-weight β-limit dextrins were mixed with amylose, the resulting gels were more rigid than those in which amylose was mixed with corresponding α-dextrins. When high-molecular-weight β-limit dextrins were mixed with amylose, the resulting gels were weaker.     

Short communication: Effects of butyrate supplementation on the productivity of lactating dairy cows fed diets differing in starch content

The objective of this study was to evaluate the effects of butyrate supplementation on the dry matter intake (DMI), milk production, and blood metabolites of lactating dairy cows fed diets differing in starch content. Eight Holstein cows after peak lactation (58.6 ± 9.96 d in milk; mean ± SD) were blocked by parity and assigned to 1 of 2 Latin squares (4 × 4) balanced for carryover effects with a 2 × 2 factorial arrangement of treatments. Treatments differed by dietary starch content (20.6 vs. 27.5%) and butyrate supplementation (butyrate vs. control) with 21-d periods. Experimental diets contained 36 and 30% corn silage, 18 and 15% grass silage, and 46 and 55% concentrates, respectively, for low starch and high starch diets, on a dry matter (DM) basis. Butyrate was provided as Gustor BP70 WS (Norel S.A., Madrid, Spain), containing 70% sodium butyrate and 30% fatty acid mixture, at 2% of dietary DM (providing butyrate at 1.1% of dietary DM), and control premix contained 70% wheat bran and 30% fatty acid mixture. Interaction effects between dietary starch content and butyrate supplementation were not observed for primary response variables, and milk yield was not affected by treatment. Butyrate supplementation increased serum β-hydroxybutyrate concentration compared with control (0.706 vs. 0.930 mM), but did not exceed 1.2 mM, a commonly accepted value for subclinical ketosis, and DMI was not affected. Cows fed butyrate had increased milk fat content (4.58 vs. 4.37%) and milk fat yield (1.51 vs. 1.42 kg/d), tended to have increased 4% fat-corrected milk yield (35.9 vs. 34.3 kg/d) and feed efficiency (1.56 vs. 1.50; 4% fat-corrected milk yield/DMI), and had decreased milk urea nitrogen (MUN) concentration (10.8 vs. 11.7 mg/dL) compared with control. Cows fed high starch diets tended to have increased DMI (23.3 vs. 22.5 kg/d), increased milk protein yield (1.13 vs. 1.05 kg/d), and decreased MUN concentration (10.3 vs. 12.2 mg/dL). Inclusion of butyrate at 1.1% of dietary DM increased milk fat production and decreased MUN concentration without affecting DMI or increasing the risk of subclinical ketosis, regardless of dietary starch content.     

Yield and Functional Properties of Taro Starch as Affected by Ultrasound

Effect of ultrasound pretreatment on yield and functional properties of taro starch was investigated. A three-factor two-level factorial design was employed with treatment time (5 and 10 min), treatment cycle (0.5 and 1), and amplitude of ultrasound (50 and 100 %). Starch yield from ultrasonic treatment varied from 17.45 to 18.97 % compared to 15.29 % in conventional method. The highest yield of 18.97 % was obtained with treatment time 10 min, treatment cycle 0.5, and amplitude 50 %. A significant increase in swelling, solubility, pasting, and texture properties of the ultrasonically extracted starch was observed. A slight decrease in clarity of the starch pastes was also observed after ultrasonic pretreatment, but the differences were not much significant. Freeze-thaw stability of the ultrasonically extracted starches was found to be better compared to starch extracted using conventional method, making them suitable for foods subjected to refrigeration. The whiteness of the ultrasonically extracted starch powders was lower compared to conventionally extracted starch, but the differences were not statistically significant.     

Labeling of Starch Granules by Bombardment with Tritium Atoms

Starch granules were labeled by exposure to tritium atoms produced by thermal dissociation of tritium gas at a tungsten filament. Activity was shown by α-amylase etching experiments to be confined to the surface of the granule. Dextrins and low molecular weight compounds could be partially resolved on Sephadex G-75. The dextrin produced during tritiation had an elution volume corresponding to dextrin of 20–35 glucose units and was hydrolyzeable by α-amylase. Labeled starch was hydrolyzed first with ß-amylase and the limit dextrin hydrolyzed further with α-amylase. A comparison of the specific activities of the maltoses produced by the two enzymes demonstrated that labeling was more heavily concentrated in outer brunches than in inner branches. Amylose obtained from labeled potato starch was purified by crystallization and on DEAE-Sephadex columns. The ion-exchange purified potato amylose was hydrolyzed with ß-amylase with 50% of the activity retained in maltose. Tritium was found to be concentrated at the nonreducing ends of the amylose molecules. These results suggest that starch molecules are organized in granules with nonreducing ends oriented to the surface.     

Entwicklungstendenzen in der Stärke- und Zuckerindustrie in Abhängigkeit vom Rohstoff. Teil 4. Kartoffel

Development Trends in Starch and Sugar Industries Depending on the Source Material. Part 4. Potato. In Western Europe (52°N. Latitude) the potential starch yield is estimated to be about 17 t ha⁻¹. For potato crops that can grow until October the average starch yield is estimated to be about 8 t ha⁻¹. The big gap between these two yields must be explained mainly by insufficient water supply to the potato crop. Also a more optimal quantity of foliage and possibly an improved type of haulm may help to bridge the gap. It is assumed that the starch yield will increase annually by about 100 kg ha⁻¹. The yield of coagulable protein is approximately 500 kg ha⁻¹. About the same quantity of N-compounds is processed with the cellwall material for fodder. It is shown that selection on starch yield is in general also a selection on protein yield. The energy output/input ratio for the production of 1 ha potatoes for the starch industry is about 2.5. It is likely that this ratio will increase.     

Effects of supplementing a Saccharomyces cerevisiae fermentation product during the periparturient period on performance of dairy cows fed fresh diets differing in starch content

The objective of this study was to evaluate the effects of supplementing a Saccharomyces cerevisiae fermentation product (SCFP; NutriTek, Diamond V, Cedar Rapids, IA) during the periparturient period (d ?28 ± 3 to 44 ± 3 relative to calving) on dry matter intake (DMI), milk production, apparent total-tract nutrient digestibility, and postpartum ovarian activity of dairy cows fed fresh diets varying in starch content. From d 28 ± 3 before the expected calving date until d 44 ± 3 after calving, 117 Holstein cows were fed diets with SCFP (SCFP; n = 59) or without (control, CON; n = 58). A common, basal, controlled-energy close-up diet (net energy for lactation: 1.43 Mcal/kg; 13.8% starch) was fed before calving. Cows within each treatment (CON or SCFP) were fed either a low- (LS; 22.1% starch) or high-starch (HS; 28.3% starch) diet from d 1 to 23 ± 3 after calving (fresh period), resulting in 4 treatment groups: LS-CON (n = 30), LS-SCFP (n = 29), HS-CON (n = 28), and HS-SCFP (n = 30). All cows were fed the HS diets from d 24 ± 3 to 44 ± 3 after calving (post-fresh period). Cows were assigned to treatment balanced for parity, body condition score, body weight, and expected calving date. Milk yield was higher for cows fed the LS diets compared with those fed the HS diets during the fresh period (34.1 vs. 32.1 kg/d), whereas DMI and 3.5% fat-corrected milk yield (FCM) were not affected by dietary starch content, and LS cows tended to lose more body condition than HS cows (?0.42 vs. ?0.35 per 21 d) during the fresh period. Overall DMI during the close-up and fresh periods did not differ between SCFP and CON cows. However, SCFP supplementation transiently increased DMI on d 1 (13.0 vs. 11.9 kg/d) and 5 (15.5 vs. 14.1 kg/d) after calving compared with CON. During the post-fresh period, SCFP cows tended to eat less than CON cows (19.8 vs. 20.6 kg/d) but had similar 3.5% FCM (44.9 vs. 43.6 kg/d), resulting in greater feed efficiency for SCFP cows (FCM/DMI; 2.27 vs. 2.13). Neither starch content of fresh diets nor SCFP supplementation affected the interval from calving to first ovulation or the incidence of double ovulation. These findings suggest that feeding low-starch diets during the fresh period can increase milk production of dairy cows during the fresh period, and that supplementation of SCFP may increase feed intake around calving and feed efficiency in the post-fresh period.     

Effects of hindgut acidosis on metabolism,inflammation, and production in dairy cows consuming a standard lactation diet

Postruminal intestinal barrier dysfunction caused by excessive hindgut fermentation may be a source of peripheral inflammation in dairy cattle. Therefore, the study objectives were to evaluate the effects of isolated hindgut acidosis on metabolism, inflammation, and production in lactating dairy cows. Five rumen-cannulated lactating Holstein cows (32.6 ± 7.2 kg/d of milk yield, 242 ± 108 d in milk; 642 ± 99 kg of body weight; 1.8 ± 1.0 parity) were enrolled in a study with 2 experimental periods (P). During P1 (4 d), cows were fed ad libitum a standard lactating cow diet (26% starch dry matter) and baseline data were collected. During P2 (7 d), all cows were fed the same diet ad libitum and abomasally infused with 4 kg/d of pure corn starch (1 kg of corn starch + 1.25 L of H₂O/infusion at 0600, 1200, 1800, and 0000 h). Effects of time (hour relative to the first infusion or day) relative to P1 were evaluated using PROC MIXED in SAS (version 9.4; SAS Institute Inc.). Infusing starch markedly reduced fecal pH (5.84 vs. 6.76) and increased fecal starch (2.2 to 9.6% of dry matter) relative to baseline. During P2, milk yield, milk components, energy-corrected milk yield, and voluntary dry matter intake remained unchanged. At 14 h, plasma insulin and β-hydroxybutyrate increased (2.4-fold and 53%, respectively), whereas circulating glucose concentrations remained unaltered. Furthermore, blood urea nitrogen increased at 2 h (23%) before promptly decreasing below baseline at 14 h (13%). Nonesterified fatty acids tended to decrease from 2 to 26 h (40%). Circulating white blood cells and neutrophils increased on d 4 (36 and 73%, respectively) and somatic cell count increased on d 5 (4.8-fold). However, circulating serum amyloid A and lipopolysaccharide-binding protein concentrations were unaffected by starch infusions. Despite minor changes in postabsorptive energetics and leukocyte dynamics, abomasal starch infusions and the subsequent hindgut acidosis had little or no meaningful effects on biomarkers of immune activation or production variables.     

Synthesis of Heptakis (2-O-methyl)-β-cyclodextrin

The title compound was prepared by a reaction sequence comprising methylation of heptakis (6-bromo-6-deoxy)-β-cyclodextrin by the Kuhn procedure, regeneration of the primary hydroxyl groups from the resulting heptakis(2-O-methyl-6-bromo-6-deoxy)-β-dextrin via the 6-O-benzoate ester by benzoate exchange and subsequent deesterification. It was proved that the methyl groups in the tetradeca-O-methyl ether of β-dextrin are located 0–2 and 0–6 of the D-glucose residues.     

Effect of modified resistant starch of culinary banana on physicochemical,functional, morphological,diffraction, and thermal properties

Resistant starch has received much attention for both its potential health benefits and functional properties. The present study revealed that the culinary banana can be a potential source for production of resistant starch type III. The results showed that resistant starch yield can be increased using debranching enzyme (Pullulanase EC 3.2.1.41) and hydrothermal process. The three repeated autoclaving and cooling (hydrothermal) cycles followed by storage at –20ºC, increased the resistant starch yield from 12.3 to 26.4%. The use of debranching enzyme and subsequent retrogradation at –20ºC increased the resistant starch yield up to 31.2%. The modified resistant starch when compared to culinary banana starch evinced better stability. The modified resistant starch was analyzed using scanning electron microscopy, Fourier transform infrared, x-ray diffraction, and thermogravimetric diffraction analysis to determine the structural changes which proved that the modification occurred substantially.     

Alkali Extraction of Starch from Corn Flour

The alkali steeping process was tested for extraction of starch from degerminated yellow corn flour. The effect of three process parameters, alkali concentration (0.1 and 0.4%), steep temperature (25 and 55°C) and steep time (30 and 90min) were evaluated for their effect on yield, protein and sodium contents of starch. Two-level full factorial design was used to investigate the process. The experimental results indicated that starch yield increased with increasing steep temperature and at low alkali concentration. All main effects and interactions were found to have significant effect on protein content in the extracted starch. The sodium content of the starch was effected by the three main effects and the three two-factor interaction effects. Conditions were identified that simultaneously produced a high starch yield, low protein and sodium contents were 0.1% alkali steep at 55°C for 30 min.     

Isolation and characterization of Mexican jackfruit (Artocarpus heterophyllus L) seeds starch in two mature stages

Starch was isolated from jackfruit (Artocarpus heterophyllus L) seeds grown in México at different stages of fruit maturity and ripeness. Seeds represent about 8–15% from the fruit that can weigh around 2–36 kg. Proximate composition of seeds showed a high protein content (ca. 22%). Starch yield was 14% with a purity of 81% in both ripeness stages and AM content was lower (12.27%) than other non‐common starch sources. The starch granules in physiological mature (PM) and consumption ripeness (CR) jackfruit showed birefringence with diverse shapes such as semi‐oval or bell shapes. The size of starch granules for PM ranged between 3 and 9.5 µm and for CR between 3 and 12 µm. A‐type XRD pattern was similar to cereal starches. PM starch had higher peak viscosity than CR, but CR did not show breakdown; both starches presented setback during cooling. Thermal properties of gelatinization and retrogradation in PM and CR starches were similar. Characterization performed on this non‐common starch showed that it could be an alternative to use in food systems.     

Physicochemical,rheological, morphological,and in vitro digestibility properties of cross-linked starch from pearl millet cultivars

The effect of epichlorohydrin (0.5%) as a cross-linking agent on physicochemical, rheological, morphological, and in vitro digestion properties of pearl millet starches from different cultivars was studied. Degree of cross-linking (DC) ranged between 40.61% and 89.75%, lower values of DC were observed for cv.HC-10 and cv.HHB-67 whereas higher values were observed for cv.HHB-223 and cv.GHB-732. Cross-linked starch from cv.GHB-732 showed the lowest amylose content, swelling power, and solubility as compared to other cultivars. Rheological properties of starches during heating showed their elastic behaviour. G′ value was much higher than the G′′ value at all frequency values for starch pastes. Plots of shear stress (σ) versus shear rate (γ?) data for cross-linked starch pastes were fitted to Herschel-Bulkley model and yield stress (σ_o), flow behaviour index (n), and consistency index (K) were evaluated. Scanning electron micrographs (SEM) investigations revealed that cross-linked starch granules had slightly rough surfaceand grooves with slight fragmentations. Readily digestible starch (RDS) of cross-linked starches varied from 46.1% to 50.6%, cv.GHB-732 had the lowest value. Slowly digestible starch (SDS) and resistant starch (RS) content of cross-linked starches ranged from 34.5% to 36.4% and 13.6% to 19.4%, respectively. cv.HC-10 had the highest value for SDS content while the highest RS content was observed for cv.GHB-732. In comparison to native starches, cross-linked modification decreased SDS and RDS content whereas RS content was increased.     

Effects of pre- and postpartum dietary starch content on productivity,plasma energy metabolites,and serum inflammation indicators of dairy cows

The objective of this study was to evaluate the effects of the starch content of pre- and postpartum diets on productivity, plasma energy metabolites, and serum markers of inflammation of dairy cows during the calving transition period. Eighty-eight primiparous and multiparous cows were randomly assigned to pre- and postpartum dietary treatments balanced for parity and pretrial body condition score at d 28 ± 3 before expected calving date. Cows were fed either a control [Control; 14.0% starch, dry matter (DM) basis] or high-starch (High; 26.1% starch, DM basis) prepartum diet commencing 28 ± 3 d before expected calving date. Following calving, cows were fed either a high-fiber (HF; 33.8% neutral detergent fiber, 25.1% starch, DM basis) or high-starch (HS; 27.2% neutral detergent fiber, 32.8% starch, DM basis) postpartum diet for the first 20 ± 2 d following calving. Cows fed the High prepartum diet had greater DM intake (12.4 vs. 10.2 kg/d), plasma concentrations of insulin (1.72 vs. 14.2 ng/mL), glucose (68.1 vs. 65.0 mg/dL), and glucagon-like peptide-2 (0.41 vs. 0.32 ng/mL) before parturition, but increased plasma free fatty acid concentration (452 vs. 363 µEq/L) and milk fat yield (1.64 vs. 1.48 kg/d) after parturition. Cows fed the HS postpartum diet had lower plasma free fatty acid (372 vs. 442 µEq/L) and serum haptoglobin (0.46 vs. 0.70 mg/mL) concentrations over a 3-wk period after calving. In addition, there was a tendency for interaction between prepartum and postpartum diets for milk yield, where feeding the HS postpartum diet increased milk yield compared with the HF diet for cows fed the Control prepartum diet (40.8 vs. 37.9 kg/d) but not for cows fed the High prepartum diet. These results suggest that management efforts to minimize the change in diet fermentability during the calving transition by feeding the High prepartum diet, the HF postpartum diet, or both did not increase productivity of dairy cows but increased fat mobilization after calving. Our findings also suggest that feeding high-starch postpartum diets can decrease fat mobilization and serum indicators of systemic inflammation and increase milk production even with the transition from a low-starch prepartum diet.     

The effects of feeding α-amylase-enhanced corn silage with different dietary starch concentrations to lactating dairy cows on milk production,nutrient digestibility,and blood metabolites

Corn silage is one of the most common ingredients fed to dairy cattle. Advancement of corn silage genetics has improved nutrient digestibility and dairy cow lactation performance in the past. A corn silage hybrid with enhanced endogenous α-amylase activity (Enogen, Syngenta Seeds LLC) may improve milk production efficiency and nutrient digestibility when fed to lactating dairy cows. Furthermore, evaluating how Enogen silage interacts with different dietary starch content is important because the ruminal environment is influenced by the amount of rumen fermentable organic matter consumed. To evaluate the effects of Enogen corn silage and dietary starch content, we conducted an 8-wk randomized complete block experiment (2-wk covariate period, 6-wk experimental period) with a 2 × 2 factorial treatment arrangement using 44 cows (n = 11/treatment; 28 multiparous, 16 primiparous; 151 ± 42 d in milk; 668 ± 63.6 kg of body weight). Treatment factors were Enogen corn silage (ENO) or control (CON) corn silage included at 40% of diet dry matter and 25% (LO) or 30% (HI) dietary starch. Corn silage used in CON treatment was a similar hybrid as in ENO but without enhanced α-amylase activity. The experimental period began 41 d after silage harvest. Feed intake and milk yield data were collected daily, plasma metabolites and fecal pH were measured weekly, and digestibility was measured during the first and final weeks of the experimental period. Data were analyzed using a linear mixed model approach with repeated measures for all variables except for body condition score change and body weight change. Corn silage, starch, week, and their interactions were included as fixed effects; baseline covariates and their interactions with corn silage and starch were also tested. Block and cow served as the random effects. Plasma glucose, insulin, haptoglobin, and serum amyloid A concentrations were unaffected by treatment. Fecal pH was greater for cows fed ENO versus CON. Dry matter, crude protein, neutral detergent fiber, and starch digestibility were all greater for ENO than CON during wk 1, but differences were less by wk 6. The HI treatments depressed neutral detergent fiber digestibility compared with LO. Dry matter intake (DMI) was not affected by corn silage but was affected by the interaction of starch and week; in wk 1, DMI was similar but by wk 6, cows fed HI had 1.8 ± 0.93 kg/d less DMI than LO cows. Milk, energy-corrected milk, and milk protein yields were 1.7 ± 0.94 kg/d, 1.3 ± 0.70 kg/d, and 65 ± 27 g/d greater for HI than LO, respectively. In conclusion, ENO increased digestibility but it did not affect milk yield, component yields, or DMI. Increasing dietary starch content improved milk production and feed efficiency without affecting markers of inflammation or metabolism.     

Isolation, Partial Characterization and Modification of the Great Northern Bean (Phaseolus vulgaris L.) Starch

The yield of the Great Northern bean starch was 18.23% (bean flour basis). The starch granule size ranged from 12 × 12 μm to 58 × 40 μm (length × width). The shape of starch granules was round to oval to elliptical, and in some cases, concave as well. Lamellae were present on all the starch granules observed. Amylose content of the starch was 10.2% (starch basis). Hog pancreatic α-amylase hydrolyzed more starch than did malt α-amylase under similar conditions. The Great Northern bean starch had good water and oil absorption capacities at room temperature (21°C). The bean starch formed a stable gel at concentrations of 7% and above (w/v). The viscoamylographic studies of the isolated starch indicated the restricted-swelling character of the bean starch.     

Replacing ground corn with soyhulls plus palmitic acid in low metabolizable protein diets with or without rumen-protected amino acids: Effects on production and nutrient utilization in dairy cows

We previously observed that diets with reduced starch concentration decreased yields of milk and milk protein in dairy cows fed low metabolizable protein diets. Supplementation of reduced-starch diets with a lipid source may attenuate or eliminate production losses. Our objective was to investigate the effects of partially replacing ground corn with soyhulls plus a palmitic acid-enriched supplement on dry matter (DM) intake, milk yield and composition, plasma AA concentration, and N and energy utilization in cows fed low metabolizable protein diets (mean = −68 g/d balance) with or without rumen-protected Met, Lys, and His (RP-MLH). Sixteen multiparous Holstein cows averaging (mean ± standard deviation) 112 ± 28 d in milk, 724 ± 44 kg of body weight, and 46 ± 5 kg/d of milk in the beginning of the study were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement of treatments. Each period lasted 21 d, consisting of 14 d for diet adaptation and 7 d for data and sample collection. Diets were fed as follows: (1) high starch (HS), (2) HS plus RP-MLH (HS+AA), (3) reduced starch plus a palmitic acid-enriched supplement (RSPA), and (4) RSPA plus RP-MLH (RSPA+AA). The HS diet contained (DM basis) 26% ground corn and 7% soyhulls, and the RSPA diet had 10% ground corn, 22% soyhulls, and 1.5% palmitic acid. The HS diet averaged (DM basis) 32.6% starch and 4% ether extract, while starch and ether extract concentrations of the RSPA diet were 21.7 and 5.9%, respectively. All 4 diets had (DM basis) 40% corn silage, 5% mixed-mostly grass haylage, 5% grass hay, and 50% concentrate. Diets did not affect DM intake and milk yield. Contrarily, feeding RSPA and RSPA+AA increased yields of energy-corrected milk (47.0 vs. 44.8 kg/d) and milk fat (1.65 vs. 1.50 kg/d) compared with HS and HS+AA. Milk fat concentration tended to decrease when RP-MLH was supplemented to HS, but no change was seen when added to RS (starch level × RP-MLH interaction). Milk and plasma urea N increased, and milk N efficiency decreased in cows fed RSPA and RSPA+AA versus HS and HS+AA. Apparent total-tract digestibilites of crude protein and neutral detergent fiber, as well as urinary urea N and total N excretion, were greater in cows offered RSPA and RSPA+AA than HS and HS+AA. Plasma Met and His concentrations increased with supplemental RP-MLH. Intake of gross energy and digestible energy and the output of urinary and milk energy were all greater with feeding RSPA and RSPA+AA versus HS and HS+AA. In summary, partially replacing ground corn with soyhulls plus palmitic acid in diets supplemented or not with RP-MLH increased milk fat yield and fiber digestibility and maintained DM intake and milk yield, but with decreased milk N efficiency and elevated urinary N excretion.