High-moisture Shelled Corn Research Articles

Changes in Moisture Desorption Rate of Shelled Corn Layers in a Low-Temperature Deep-Bed Drying Column

To optimize grain drying processes, high-moisture shelled corn was dried in a device using a combination of three temperatures (45, 55 and 65 °C) and hot-air velocities (0.7, 1.1 and 1.3 m·s-1). The grain moisture and temperature, and the relative humidity (RH) of interstitial airflow were determined intelligently in grain layers of 7.5 to 32.5 cm with 5.0 cm intervals. The change in RH of interstitial airflow in grain layers of 7.5-27.5 cm with drying time all revealed the shape of a hyperbolic line and took turns to lag. These RH lines shortened with an increased drying temperature from 45 to 65 °C and hot-air velocity from 0.7 to 1.3 m·s-1. The temperature lines were raised and shortened with an increase in drying temperature and hot-air velocity. A modified moisture diffusion exponential equation was developed to analyze the moisture desorption rate of corn kernels. For the average sorption rate curve from grain layers of 2.5-32.5 cm at 1.3 m·s-1 of hot air, the transition points from adsorption to desorption occurred at 2.4 h, 2.7 h, and 3.0 h with drying temperatures of 65 and 45 °C, respectively, and represented the earliest and largest initial desorption rates among the three hot-air velocities. The moisture desorption rate of samples increased with increasing drying temperature. Compared with the average value of grain layers, at the same hot-air velocity, the kernel effective diffusivity (Deff) values dried at 55 °C were correspondingly higher than those dried at 45 and 65 °C. At the same drying temperature, the kernel Deff values tended to increase with an increase in hot-air velocity, whereas the activation energy decreased. These results suggested that an increase in drying temperature and hot-air velocity may considerably shorten adsorption time and increase desorption rates of shelled corn in deep bed drying.

Performance and ruminal fermentation of second-trimester pregnant beef cows fed short-season high-moisture corn stover or barley greenfeed during winter in western Canada

This study evaluated performance and ruminal fermentation for cows fed short-season high-moisture shelled corn stover with corn dried distillers’ grains with solubles (COR) or barley greenfeed (BAR) that was either swathed (S-COR; S-BAR; Experiment 1) or baled (B-COR; B-BAR; Experiment 2) as winter-feeding systems. In Experiment 1, cows were randomly assigned to S-COR or S-BAR and fed for 52 days in the fields where crops were grown. Body weight (BW), subcutaneous rib and rump fat, and body condition score (BCS) were measured, with no differences detected between treatments ( P > 0.05). However, S-COR had a lower estimated dry matter intake (DMI) than S-BAR ( P ≤ 0.03). In Experiment 2, cows were assigned to B-COR or B-BAR for 42 days and fed in field paddocks. Cows fed B-COR had less ( P ≤ 0.01) DMI, final BW, rib fat, rump fat, and BCS than B-BAR, with no differences ( P > 0.05) for ruminal pH. Total SCFA concentration was greater ( P ≤ 0.05) on day 21 for B-BAR than B-COR, but not on day 42. Under western Canadian conditions, COR may reduce DMI and the performance of pregnant cows, suggesting that additional preservation and supplementation strategies should be investigated.

Short-season high-moisture shelled corn, snaplage, or corn silage as a partial replacement for dry-rolled barley grain or barley silage in western Canadian beef cattle finishing diets

The objective was to evaluate the replacement of barley-based ingredients with short-season high-moisture corn products on steer growth performance and carcass characteristics. Over 2 years, 320 beef steers (528 ± 36.2 kg initial body weight) were assigned to 32 pens (4 pens/treatment/year). Treatments were finishing diets that contained dry-rolled barley grain and barley silage (BGBS; control), barley grain and corn silage (BGCS), high-moisture shelled corn and barley grain with barley silage (HCBS), or snaplage (included as a silage and grain source) with barley grain (SNAP). Steers were fed for 99 days and 72 days in years 1 and 2, respectively. Steers fed BGCS did not differ ( P ≥ 0.13) from BGBS for dry matter intake, average daily gain, gain:feed, or carcass characteristics. Steers fed HCBS had greater ( P ≤ 0.05) hot carcass weight and dressing percentage than BGBS. A lesser ( P = 0.02) proportion of steers fed SNAP had severe liver abscesses than BGBS. We concluded that corn silage can replace barley silage, 50% replacement of barley grain with high-moisture shelled corn may improve hot carcass weight, and replacement of barley silage and some barley grain with snaplage decreases the proportion of cattle with severe liver abscesses at slaughter.

Digestibility of western Canadian finishing beef cattle diets when short-season, high-moisture shelled corn and snaplage partially replace dry-rolled barley grain and barley silage

The objective of this study was to determine the effects of substituting barley grain with short-season, high-moisture shelled corn, and barley grain and barley silage with snaplage on ruminal fermentation and the site and extent of digestion in beef cattle fed finishing diets. Six ruminally and duodenally cannulated heifers (420 ± 16.4 kg body weight) were fed a barley grain and silage finishing diet (BG), a diet where half of the barley grain was replaced with high-moisture shelled corn (HC), or a diet where the barley silage and a portion of grain were replaced with snaplage (SN) in a replicated 3 × 3 Latin square design. While dry matter and starch intake were unaffected, feeding SN resulted in greater ( P = 0.02) ruminal but not total tract starch digestibility than BG. Ruminal pH did not differ between HC and BG, but SN reduced ( P = 0.02) minimum ruminal pH relative to BG. Feeding BG increased ( P = 0.04) ruminal ammonia concentrations over HC. In conclusion, high-moisture shelled corn can partially replace barley grain with minimal impact on nutrient digestibility or ruminal fermentation, but replacement of barley silage and some barley grain with snaplage may increase the risk of ruminal acidosis.

ハイモイスチャーシェルドコーンの給与が泌乳牛の消化率，窒素出納，飼養成績および血液性状に及ぼす影響

ハイモイスチャーシェルドコーンの給与が泌乳牛の消化率，窒素出納，飼養成績および血液性状に及ぼす影響

High Moisture Shelled Corn Harvesting and Ensiling System Using a Combine Harvester and Flexible Container Bag

High Moisture Shelled Corn Harvesting and Ensiling System Using a Combine Harvester and Flexible Container Bag

Effects of replacing soybean meal with canola meal or treated canola meal on ruminal digestion, omasal nutrient flow, and performance in lactating dairy cows

Extrusion treated canola meal (TCM) was produced in an attempt to increase the rumen-undegraded protein fraction of canola meal (CM). The objective of this study was to evaluate the effects of replacing soybean meal (SBM) with CM or TCM on ruminal digestion, omasal nutrient flow, and performance in lactating dairy cows. To assess performance, 30 multiparous Holstein cows averaging (mean ± SD) 119 ± 23 d in milk and 44 ± 7 kg of milk/d and 15 primiparous cows averaging 121 ± 19 d in milk and 34 ± 6 kg of milk/d were blocked in a randomized complete block design with a 2-wk covariate period and 12-wk experimental period (experiment 1). Dietary ingredients differed only in protein supplements, which were SBM, CM, or TCM. All diets were formulated to contain (dry matter basis) 30% alfalfa silage, 30% corn silage, 4% soy hulls, 2.4% mineral-vitamin premix, and 16% CP. The SBM diet contained 25% high-moisture shelled corn and 8.6% SBM; the canola diets contained 22% high-moisture shelled corn and either 11.2% CM or 11.4% TCM. To assess ruminal digestion and omasal nutrient flow, 6 rumen-cannulated cows were blocked into 2 squares of 3 cows and randomly assigned within blocks to the same 3 dietary treatments as in experiment 1 in a replicated 3 × 3 Latin square design (experiment 2). Data were analyzed using the MIXED procedure of SAS (SAS Institute, Cary, NC). Orthogonal contrasts were used to compare effects of different protein supplements: SBM versus CM + TCM and CM versus TCM. In experiment 1, compared with SBM, apparent total-tract digestibilities of dry matter and nutrients were greater in cows fed both CM diets, and there was a tendency for nutrient digestibilities to be higher in cows fed CM compared with TCM. Diets did not affect milk yield and milk components; however, both canola diets decreased urinary urea N (% of total urinary N), fecal N (% of total N intake), and milk urea N concentration. In experiment 2, compared with SBM, both canola diets increased N intake and tended to increase rumen-degraded protein supply (kg/d) and N truly digested in the rumen (kg/d). Diets did not affect ruminal digestibility, efficiency of microbial protein synthesis, and rumen-undegraded protein flow among diets. Results from this experiment indicate that replacing SBM with CM or TCM in diets of lactating cows improved digestibility and may reduce environmental impact. Moreover, under the conditions of the present study, treating CM by extrusion did not improve CM utilization.

Replacing alfalfa silage with tannin-containing birdsfoot trefoil silage in total mixed rations for lactating dairy cows

Two lactation trials were conducted comparing the feeding value of silages made from birdsfoot trefoil (BFT, Lotus corniculatus L.) that had been selected for low (BFTL), medium (BFTM), and high (BFTH) levels of condensed tannins (CT) to an alfalfa silage (AS) when fed as the principal forage in total mixed rations. Diets also included corn silage, high-moisture shelled corn, soybean meal, soy hulls, and supplemental fat. In trial 1, 32 lactating Holstein cows were blocked by days in milk, assigned to treatment sequences in 8 balanced 4 × 4 Latin squares, and fed 50% dietary dry matter from AS or 1 of 3 BFT silages containing 0.6, 1.2, or 1.7% CT. Diets averaged 17.5 to 19.5% crude protein and 26% neutral detergent fiber on a dry matter basis. Data were collected over the last 2 wk of each 4-wk period. Intakes were 1.3 to 2.8 kg of dry matter/d greater on BFT than on AS and cows gained 0.5 kg of body weight/d on BFT diets while losing 0.14 kg of body weight/d on the AS diet; this resulted in greater milk per dry matter intake (DMI) on AS. Linear effects indicated true protein yield and milk urea nitrogen declined with increasing CT concentration and quadratic effects indicated DMI, energy-corrected milk, and fat yield were increased at intermediate CT concentration. True protein yield and apparent N-efficiency were greater, and milk urea nitrogen lower, on all BFT diets than on AS. In trial 2, 50 lactating Holstein cows were fed a covariate AS diet for 2 wk and then blocked by parity and days in milk and randomly assigned to 1 of 5 diets that were fed continuously for 12 wk. Diets contained (dry matter basis) 48% AS, 16% AS plus 32% of 1 of 3 BFT silages with 0.5, 0.8, or 1.5% CT, or 48% of an equal mixture of each BFT silage. Diets averaged 16.5% crude protein and 30% neutral detergent fiber. Intake and milk yield tended to be lower on AS than BFT, but body weight gains averaged 0.6 kg/d on all diets. Cows fed any of the BFT silages had reduced milk urea nitrogen and ruminal ammonia and reduced urinary N excretion. Feeding the BFT mixture reduced concentrations of milk true protein and milk urea nitrogen and depressed apparent nutrient digestibility. Among diets containing the individual BFT silages, linear reductions in DMI and yield of milk, fat, true protein, lactose, and SNF were observed with increasing CT concentration. By contrast, a previous trial with the same BFT populations showed that substituting BFTH silage containing 1.6% CT for AS in rations containing 60% silage dry matter had no effect on intake, increased yield of milk, energy-corrected milk and milk components, elevated protein use-efficiency, but with a more modest reduction in milk urea nitrogen and urinary N excretion. Silage analyses suggested that the inconsistent responses among trials were related to growth environment or ensiling effects that altered tannin-protein interactions in BFT silage. Differences in diet formulation among trials may have also influenced responses. Results from the current and previous trials indicate further work is needed to identify optimum tannin levels in forages.

Effect of High Moisture Ear Corn and High Moisture Shelled Corn Feeds on Laying Hen Performance.

The aim of the study was to test the effect of high moisture ear corn (HMEC) and high moisture shelled corn (HMSC) feeds on laying hen performance. A total of 108 Rhode Island Red laying hens were divided by body weight and performance into 12 blocks (9 in each). Each block was assigned to one of three dietary treatments. The hens were fed one of three experimental diets containing 48.0% commercial laying hen diet (CON), 55.7% HMEC (EC) or 48.5% HMSC (SC) on a dry matter (DM) basis. All diets were isocaloric (2.80 mega calorie (Mcal) of (metabolizable energy (ME)/kg of DM) and isonitrogenous (15.5% CP of DM). DM Feed intake (139 to 148 g DM/d per hen), egg production rate (79 to 85%), egg mass (47.6 to 51.2 g/d per hen) and feed utilization (2.7 to 3.1 g of feed DM/g of egg) were not affected by diet. Body weight for the SC diet was significantly less than that for the CON diet (P<0.05). This was possibly due to the low feed intake during weeks 1 and 2 because of the short adaptation period to the experimental diet. The body weight loss of hens fed the SC diet may not have occurred when there had been a sufficient adaptation period. Eggshell strength (3.27 to 3.52 kg/cm2) and Haugh unit (80.0 to 83.6) were not affected by diet. In conclusion, HMEC and HMSC diets do not significantly affect laying hen performance and can be used as a main ingredient of the laying hen diet.

Effect of Feeding of Ear Corn Silage, High Moisture Shelled Corn or Dry Shelled Corn on Lactation Performance and Metabolic Profile of Dairy Cows

Effect of Feeding of Ear Corn Silage, High Moisture Shelled Corn or Dry Shelled Corn on Lactation Performance and Metabolic Profile of Dairy Cows

Comparison of Chemical Composition, Nutritive Value and Production Yield between High Moisture Shelled Corn and Ear Corn Silage

Comparison of Chemical Composition, Nutritive Value and Production Yield between High Moisture Shelled Corn and Ear Corn Silage

トウモロコシ子実主体サイレージ（HMSCおよびCCM）の飼料成分組成，発酵品質および栄養価

トウモロコシ子実主体サイレージ（HMSCおよびCCM）の飼料成分組成，発酵品質および栄養価

Blood parameters in fattening pigs fed whole-ear corn silage and housed in group pens or in metabolic cages.

The aim of this work was to evaluate the effects of the inclusion of whole-ear corn silage (WECS) in diets for advanced fattening heavy pigs (substitution for part of the dry corn and wheat bran) allocated or not in metabolic cages on the main blood parameters. The high-moisture shelled corn is largely used in pig feeding while WECS is less often used despite the fact that it increases the DM crop yield. Three experimental diets were fed to 27 barrows (Italian Large White × Italian Duroc), with an average BW of 98.2 (±5.6) kg at the start of the trial, and randomly allotted to 3 experimental groups including a control diet (CON) containing cereal meals (corn, barley, and wheat, 80.2% DM in total), soybean meal (9% DM), wheat bran (8% DM), minerals and supplements (2.8% DM), and 2 diets containing WECS (15 or 30% DM referred to as 15WECS and 30WECS, respectively) in partial or complete substitution for wheat bran and corn meal. The pigs were randomly housed in 9 pens with 3 animals per pen and 3 pens per dietary treatment. Six pigs per each of the 3 treatments were moved from the pens to individual metabolic cages for 3 consecutive periods (2 pigs per treatment per period). Each period lasted 14 d, and blood was collected at the start and at the end of the periods. Blood was drawn from the jugular vein before feed distribution in the morning, at 14 d intervals, and analyzed for hematological, metabolic, and serum protein profiles. The effect of the metabolic cage housing was included in the statistical model to compare the results obtained in the 2 different environments of restrained and group-housed barrows. The WECS affected the neutrophil to lymphocyte ratio and mean corpuscular hemoglobin concentration. The main diet effect on plasma metabolites was recorded for plasma NEFA, with higher values in WECS diets compared with the CON. The metabolic cage housing affected both hematological (red blood cell count, hemoglobin, hematocrit) and metabolic (protein and its fractions) items, which can be markers of hemodilution. These results indicate the possibility to use this feed in the diet of heavy pigs without negative effects on physiology. The absolute values from metabolic profile of pigs in metabolic cages must be considered with caution for possible comparisons with values obtained on-field in group pens, particularly because a different hemodilution may affect the results.

Effect of corn snaplage on lactation performance by dairy cows

<h2>ABSTRACT</h2> The objective of this study was to determine lactation performance by dairy cows fed corn snaplage either alone (SNAP) or in combination with ground dry shelled corn (SPDC) versus rolled high-moisture shelled corn (RHMC). Dry-matter content was greater for RHMC (78.2%) than SNAP (68.5%). The starch content of SNAP was approximately 10%-units lower than RHMC. Sixty Holstein cows (30 primiparous and 30 multiparous; 100 ± 23 DIM and 626 ± 44kg of BW at trial initiation) were used in a randomized, complete-block, continuous-lactation trial: 2-wk covariate adjustment period with all cows fed a 50:50 mixture (DM basis) of SNAP and RHMC in TMR followed by an 8-wk experimental period with cows fed their assigned treatment corn grain (RHMC, SNAP, or SPDC) in TMR. Intake of DM was reduced by 2.6 kg/d per cow, on average, for SNAP and SPDC compared with RHMC. Milk yield averaged 39.4 kg/d per cow and was unaffected by treatment as were all measures of component-corrected milk yield. Actual milk, FCM, solids-corrected milk, and energy-corrected milk feed efficiencies (kg/kg) were greater, on average, for SNAP and SPDC compared with RHMC by 7 to 9%. Milk fat percentage was reduced by 0.27% units, and milk-urea-nitrogen concentration was greatest, for SNAP compared with RHMC. These changes in milk composition along with reduced DMI were likely related to greater ruminal starch digestibility for SNAP. Milk fat and milk-urea-nitrogen concentrations were improved by the partial replacement of SNAP with ground dry shelled corn in the SPDC treatment.

Changes in ruminal bacterial community composition following feeding of alfalfa ensiled with a lactic acid bacterial inoculant

Some silage inoculants help to improve silage quality and promote an increase in milk production, possibly through altering the rumen microflora. We hypothesized that rumen bacterial community composition (BCC) would be different in cows fed alfalfa ensiled with the inoculant Lactobacillus plantarum MTD/1 (LP) compared with those fed alfalfa ensiled without the inoculant (Ctrl). Eight ruminally cannulated Holstein cows were allotted to 2 diets (Ctrl or LP) in a double crossover design with four 28-d periods. Diets were formulated to contain (% dry matter basis) 28.0% neutral detergent fiber and 16.2% crude protein, and contained alfalfa silage, 50.9; corn silage, 20.6; high-moisture shelled corn, 21.4; soy hulls, 4.7; plus minerals and vitamins, 2.4. Ruminal digesta were collected just before feeding on 3 consecutive days near the end of each period, and were separated into solid and liquid phases. Microbial DNA was extracted from each phase, amplified by PCR using domain-level bacterial primers, and subjected to automated ribosomal intergenic spacer analysis. The pH was 4.56 and 4.86 and the lactate-to-acetate ratio 9.8 and 4.4, respectively, for the treated and untreated alfalfa silages. Dry matter intakes and milk production data were not influenced by diets but showed a cow effect. Total volatile fatty acids (mM) tended to be greater for LP compared with Ctrl. Individual volatile fatty acids were not influenced by diets but showed a significant cow effect. Ruminal acetate (mol/100mol) and acetate-to-propionate ratio were lower and propionate (mol/100mol) greater for the 2 milk fat-depressed (MFD; <3.2% fat content) cows compared with the other 6 cows. Correspondence analysis of the 265 peaks in the automated ribosomal intergenic spacer analysis profile across the 188 samples revealed that the first 2 components contributed 7.1 and 3.8% to the total variation in the profile. The ordination points representing the liquid and solid phases clustered separately, indicating that these phases differed in BCC. The analysis of similarity data showed differences between Ctrl and LP. The lactic acid bacterial counts (log10 cfu/g of wet silage) were 3.94 and 4.53 for the untreated and treated silage, respectively, at ensiling. The relative population size (RPS) of L. plantarum, determined by real-time PCR of 16S rRNA gene copies, was greater in LP compared with Ctrl. The ordination points corresponding to certain individual cows clustered separately, and the most distinctive bacterial communities were those associated with MFD cows. The RPS of Megasphaera elsdenii was greater in 1 of the 2 MFD cows, although mean RPS of M. elsdenii did not differ between the treatments. In addition to the differences in rumen BCC between LP and Ctrl, MFD cows also displayed differences in BCC compared with cows with normal milk fat yield.

Effect on Production of Replacing Dietary Starch with Sucrose in Lactating Dairy Cows

Replacing dietary starch with sugar has been reported to improve production in dairy cows. Two sets of 24 Holstein cows averaging 41kg/d of milk were fed a covariate diet, blocked by days in milk, and randomly assigned in 2 phases to 4 groups of 6 cows each. Cows were fed experimental diets containing [dry matter (DM) basis]: 39% alfalfa silage, 21% corn silage, 21% rolled high-moisture shelled corn, 9% soybean meal, 2% fat, 1% vitamin-mineral supplement, 7.5% supplemental nonstructural carbohydrate, 16.7% crude protein, and 30% neutral detergent fiber. Nonstructural carbohydrates added to the 4 diets were 1) 7.5% corn starch, 0% sucrose; 2) 5.0% starch, 2.5% sucrose; 3) 2.5% starch, 5.0% sucrose; or 4) 0% starch, 7.5% sucrose. Cows were fed the experimental diets for 8 wk. There were linear increases in DM intake and milk fat content and yield, and linear decreases in ruminal concentrations of ammonia and branched-chain volatile fatty acids, and urinary excretion of urea-N and total N, and urinary urea-N as a proportion of total N, as sucrose replaced corn starch in the diet. Despite these changes, there was no effect of diet on microbial protein formation, estimated from total purine flow at the omasum or purine derivative excretion in the urine, and there were linear decreases in both milk/DM intake and milk N/N-intake when sucrose replaced dietary starch. However, expressing efficiency as fat-corrected milk/DM intake or solids-corrected milk/DM intake indicated that there was no effect of sucrose addition on nutrient utilization. Replacing dietary starch with sucrose increased fat secretion, apparently via increased energy supply because of greater intake. Positive responses normally correlated with improved ruminal N efficiency that were altered by sucrose feeding were not associated with increased protein secretion in this trial.

The Relative Merit of Ruminal Undegradable Protein from Soybean Meal or Soluble Fiber from Beet Pulp to Improve Nitrogen Utilization in Dairy Cows

Early lactating dairy cows were used to determine whether the replacement of solvent-extracted soybean meal [SSBM; a source of rumen-degradable protein (RDP)] with expeller soybean meal (ESBM; a source of rumen-undegradable protein), or the replacement of high-moisture shelled corn (HMSC) with beet pulp (a source of soluble fiber) would be effective in improving efficiency of N usage for milk production. The study was designed as a replicated 4×4 Latin square with 21-d periods. Eight multiparous Holstein cows were fed, ad libitum, the following diets, which were based on alfalfa silage and HMSC, and formulated to be isocaloric: 1) basal diet without a protein supplement (negative control diet: NC); 2) NC supplemented with solvent-extracted SBM (diet SSBM); 3) NC supplemented with expeller SBM (diet ESBM); 4) SSBM in which unmolassed dried beet pulp replaced half of the HMSC (diet SSBMBP). Compared with diet NC, protein supplementation increased intake of organic matter and dry matter. Milk and milk protein yields were lower with NC but this diet resulted in the greatest efficiency of N usage for milk production (30% milk N/N intake). Supplementation with ESBM, a proven source of RUP, increased plasma concentrations of histidine and branched-chain amino acids, and reduced milk urea N concentration, but failed to improve the yields of milk or milk protein. Milk fat yield tended to decrease with RUP supplementation. Replacing part of HMSC with soluble fiber from beet pulp (SSBMBP) tended to decrease milk production compared with SSBM; the effect was due to a reduction in dry matter intake. There were no differences among diets SSBM, ESBM, or SSBMBP in urinary excretion of purine derivatives. Neither substitution of ESBM for SSBM nor partial replacement of HMSC with beet pulp altered the efficiency of N usage for milk production or manure N excretion.

Effect of Supplementing Rumen-Protected Methionine on Production and Nitrogen Excretion in Lactating Dairy Cows

Two 4×4 Latin square trials (4-wk periods; 16 wk total) were conducted to see whether supplementing rumen-protected Met (RPM; fed as Mepron) would allow feeding less crude protein (CP), thereby reducing urinary N excretion, but without losing production. In trial 1, 24 Holsteins were fed 4 diets as total mixed rations containing [dry matter (DM) basis]: 18.6% CP and 0g of RPM/d; 17.3% CP and 5g of RPM/d; 16.1% CP and 10g of RPM/d; or 14.8% CP and 15g of RPM/d. Dietary CP was reduced by replacing soybean meal with high-moisture shelled corn. All diets contained 21% alfalfa silage, 28% corn silage, 4.5% roasted soybeans, 5.8% soyhulls, 0.6% sodium bicarbonate, 0.5% vitamins and minerals, and 27% neutral detergent fiber. There was no effect of diet on intake, weight gain, or yields of protein, lactose, and solids-not-fat. However, production was greater at 17.3% CP plus RPM and 16.1% CP plus RPM than on the other 2 diets. Apparent N efficiency (milk N:N intake) was greatest on the lowest CP diet containing the most RPM. Linear reductions in milk urea N and urinary N excretion were observed with lower dietary CP. In trial 2, 32 Holsteins were fed 4 diets as total mixed rations, formulated from ingredients used in trial 1 and containing 16.1 or 17.3% CP with 0 or 10g of RPM/d. On average, cows were calculated to be in negative N balance on all diets because of lower than expected DM intake. There was no effect of RPM supplementation on any production trait. However, higher CP gave small increases in yields of milk, protein, and solids-not-fat and tended to increase DM intake and lactose yield. Apparent N efficiency was greater, and milk urea nitrogen was lower, on 16.1% CP. In trial 1, feeding lower CP diets supplemented with RPM resulted in improved N efficiency and reduced urinary N excretion. However, in trial 2, reducing dietary CP from 17.3 to 16.1% reduced milk secretion, an effect that was not reversed by RPM supplementation at low DM intakes when cows were apparently mobilizing body protein.

Effects of Different Protein Supplements on Omasal Nutrient Flow and Microbial Protein Synthesis in Lactating Dairy Cows

Eight ruminally cannulated Holstein cows that were part of a larger lactation trial were used in 2 replicated 4×4 Latin squares to quantify effects of supplementing protein as urea, solvent soybean meal (SSBM), cottonseed meal (CSM), or canola meal (CM) on omasal nutrient flows and microbial protein synthesis. All diets contained (% of dry matter) 21% alfalfa silage and 35% corn silage plus 1) 2% urea plus 41% high-moisture shelled corn (HMSC), 2) 12% SSBM plus 31% HMSC, 3) 14% CSM plus 29% HMSC, or 4) 16% CM plus 27% HMSC. Crude protein was equal across diets, averaging 16.6%. The CSM diet supplied the least rumen-degraded protein and the most rumen-undegraded protein. Microbial nonammonia N flow was similar among the true protein supplements but was 14% lower in cows fed urea. In vivo ruminal passage rate, degradation rate, and estimated escape for the 3 true proteins were, respectively, 0.044/h, 0.105/h, and 29% for SSBM; 0.051/h, 0.050/h, and 51% for CSM; and 0.039/h, 0.081/h, and 34% for CM. This indicated that CSM protein was less degraded because of both a faster passage rate and slower degradation rate. Omasal flow of individual AA, branched-chain AA, essential AA, nonessential AA, and total AA all were lower in cows fed urea compared with one of the true protein supplements. Among the 3 diets supplemented with true protein, omasal flow of Arg was greatest on CSM, and omasal flow of His was greatest on CSM, intermediate on CM, and lowest on SSBM. Lower flows of AA and microbial nonammonia N explained lower yields of milk yield and milk components observed on the urea diet in the companion lactation trial. These results clearly showed that supplementation with true protein was necessary to obtain sufficient microbial protein and rumen-undegraded protein to meet the metabolizable AA requirements of high-producing dairy cows.

Effects of Different Protein Supplements on Milk Production and Nutrient Utilization in Lactating Dairy Cows

Sixteen (8 ruminally cannulated) multiparous and 8 primiparous lactating Holstein cows were used in 6 replicated 4×4 Latin squares to test the effects of feeding supplemental protein as urea, solvent soybean meal (SSBM), cottonseed meal (CSM), or canola meal (CM) on milk production, nutrient utilization, and ruminal metabolism. All diets contained (% of DM) 21% alfalfa silage and 35% corn silage plus 1) 2% urea plus 41% high-moisture shelled corn (HMSC), 2) 12% SSBM plus 31% HMSC, 3) 14% CSM plus 29% HMSC, or 4) 16% CM plus 27% HMSC. Crude protein was equal across diets, averaging 16.6%. Intake and production were substantially reduced, and milk urea, blood urea, and ruminal ammonia were increased on urea vs. the diets supplemented with true protein. Although intake was lower in cows fed SSBM compared with CM, no differences were observed for milk yield among SSBM, CSM, and CM. Yields of fat and protein both were lower on CSM than on CM, whereas SSBM was intermediate. Milk urea and milk protein contents also decreased when CSM replaced SSBM or CM. Diet did not affect ruminal volatile fatty acids except that isobutyrate concentration was lowest on urea, intermediate on CSM, and greatest on SSBM and CM. Urinary excretion of urea N and total N was greatest on urea, intermediate on SSBM and CM, and lowest on CSM. Apparent N efficiency (milk N/N intake) was lower on the CSM diet than on the SSBM diet. Overall, production and N utilization were compromised when the diets of high-yielding dairy cows were supplemented with urea rather than true protein and the value of the true proteins, from most to least effective, was in the order CM > SSBM > CSM.