Effects of bale moisture and bale diameter on spontaneous heating, dry matter recovery, in vitro true digestibility, and in situ disappearance kinetics of alfalfa-orchardgrass hays

Alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.) hay was made in 96 large-round bales over 3 harvests during 2006 and 2007 to assess the effects of spontaneous heating on dry matter (DM) recovery, in vitro true digestibility (IVTD), and in situ disappearance kinetics of DM. Throughout these harvests, bales were made at preset diameters of 0.9, 1.2, or 1.5 m and at moisture concentrations ranging from 9.3 to 46.6%. Internal bale temperatures were monitored daily during an outdoor storage period, reaching maxima of 77.2°C (MAX) and 1,997 heating degree days >30°C (HDD) for one specific combination of bale moisture, bale diameter, and harvest. Following storage, regressions of DM recovery on HDD and MAX indicated that DM recovery declined linearly in close association with measures of spontaneous heating. For HDD, slopes and intercepts differed across bale diameters, probably because the greater surface area per kilogram of DM for 0.9-m bales facilitated more rapid dissipation of heat than occurred from 1.2- or 1.5-m-diameter bales. Regardless of bale diameter, coefficients of determination were high (r² ≥ 0.872) when HDD was used as the independent variable. Regressions of DM recovery on MAX also exhibited high r² statistics (≥ 0.833) and a common slope across bale diameters (−0.32 percentage units of DM/°C). Changes in concentrations of IVTD during storage (poststorage - prestorage; ΔIVTD) also were regressed on HDD and MAX. For HDD, the data were best fit with a nonlinear model in which ΔIVTD became rapidly negative at <1,000 HDD, but was asymptotic thereafter. When MAX was used as the independent variable, a simple linear model (y = −0.23x + 9.5) provided the best fit. In both cases, coefficients of determination were comparable to those for DM recovery (R² or r² ≥0.820). Changes (poststorage - prestorage) in ruminal DM degradation rate (ΔK_d) and effective ruminal degradability of DM (ΔDEG) were assessed similarly. Although the most appropriate statistical model varied, ΔK_d and ΔDEG both became increasingly negative at low to moderate levels of heating, but generally stabilized thereafter. Both HDD and MAX were excellent predictor variables for both ΔK_d and ΔDEG; r² or R² statistics ranged from 0.788 to 0.921. Measures of spontaneous heating are consistently effective indicators of DM recovery following storage, as well as good indicators of concurrent changes in IVTD or in situ disappearance of DM for heated alfalfa-orchardgrass hays.     

Effects of spontaneous heating on fiber composition, fiber digestibility, and in situ disappearance kinetics of neutral detergent fiber for alfalfa-orchardgrass hays

During 2006 and 2007, forages from 3 individual hay harvests were utilized to assess the effects of spontaneous heating on concentrations of fiber components, 48-h neutral detergent fiber (NDF) digestibility (NDFD), and in situ disappearance kinetics of NDF for large-round bales of mixed alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.). Over the 3 harvests, 96 large-round bales were made at preset bale diameters of 0.9, 1.2, or 1.5 m, and at moisture concentrations ranging from 9.3 to 46.6%. Internal bale temperatures were monitored daily during an outdoor storage period, reaching maxima (MAX) of 77.2°C and 1,997 heating degree days >30°C (HDD) for one specific combination of bale moisture, bale diameter, and harvest. Concentrations of all fiber components (NDF, acid detergent fiber, hemicellulose, cellulose, and lignin) increased in response to spontaneous heating during storage. Changes in concentrations of NDF during storage (poststorage - prestorage; ΔNDF) were regressed on HDD using a nonlinear regression model (R² = 0.848) that became asymptotic after ΔNDF increased by 8.6 percentage units. Although the specific regression model varied, changes (poststorage - prestorage) in concentrations of acid detergent fiber, cellulose, and lignin also increased in nonlinear relationships with HDD that exhibited relatively high coefficients of determination (R² = 0.710 to 0.885). Fiber digestibility, as determined by NDFD, was largely unaffected by heating characteristics except within bales incurring the most extreme levels of HDD or MAX. In situ assessment of ruminal NDF disappearance kinetics indicated that disappearance rate (K_d) declined by about 40% within the range of heating incurred over these hay harvests. The change in K_d during storage (ΔK_d) was related closely to both HDD and MAX by nonlinear models exhibiting high R² statistics (0.907 and 0.883, respectively). However, there was no regression relationship between changes (poststorage - prestorage) in effective ruminal disappearance of NDF and spontaneous heating, regardless of which heating measure was used as the independent variable. The close regression relationship between ΔK_d and measures of spontaneous heating indicates clearly that ruminal NDF disappearance was altered negatively by some direct or indirect aspect of spontaneous heating. However, it was equally apparent that these effects were offset by an expanding pool of dry matter recovered as potentially degradable NDF.     

Effects of spontaneous heating on estimates of total digestible nutrients for alfalfa-orchardgrass hays packaged in large round bales

Large round or large square hay packages are more likely to heat spontaneously during storage than hay packaged in conventional (45 kg) bales, and the effects of this phenomenon on the associated energy estimates for these hays can be severe. Our objectives for this project were to assess the relationship between estimates of total digestible nutrients (TDN) and spontaneous heating and to describe any important differences in energy estimates that may result specifically from 2 methods of estimating truly digestible fiber (TD-Fiber). Using the summative approach to estimate TDN, TD-Fiber can be estimated from inputs of protein-corrected neutral detergent fiber (NDFn) and acid detergent lignin (TD-FiberLIG) or from NDFn and 48-h neutral detergent fiber digestibility (TD-FiberNDFD). Throughout 2006 and 2007, mixed alfalfa (Medicago sativa L.)-orchardgrass (Dactylis glomerata L.) hays from 3 individual harvests were obtained from the same 8.2-ha research site near Stratford, Wisconsin. Both options for estimating TD-Fiber (TD-FiberLIG or TD-FiberNDFD) were then used independently via the summative approach to estimate the total TDN concentrations (TDN-LIG or TDN-NDFD, respectively) within these hays. Estimates of both TDN-LIG and TDN-NDFD then were related to heating degree days >30°C accumulated during storage by various regression techniques. Changes (poststorage - prestorage) in TDN-LIG that occurred during storage (ΔTDN-LIG) were best fitted with a nonlinear decay model in which the independent variable was squared [Y = (11.7 × e^{−0.0000033×x×x}) − 11.6; R² = 0.928]. For changes in TDN-NDFD (ΔTDN-NDFD), a quadratic regression model provided the best fit (Y = 0.0000027x² − 0.010x + 0.4; R² = 0.861). Generally, ΔTDN-LIG estimates were 2.0 to 4.0 percentage units lower than ΔTDN-NDFD estimates when heating exceeded 500 HDD. For regressions on maximum internal bale temperature, both ΔTDN-LIG (Y = −0.38x + 16.3; R² = 0.954) and ΔTDN-NDFD (Y = −0.25x + 10.2; R² = 0.848) were best fitted by linear models with heterogeneous (P < 0.001) slopes and intercepts. In both cases, coefficients of determination were high, suggesting that simple measures of spontaneous heating are excellent predictors of energy losses in heated forages. Regardless of method, reductions in TDN were associated primarily with losses of nonfiber carbohydrate, which is known to occur via oxidation of sugars during spontaneous heating. For heated forages, some discrepancy between TDN-LIG and TDN-NDFD existed because the relationship between NDFD and spontaneous heating was shown previously to be very poor, resulting in minimal changes for estimates of TD-FiberNDFD as a consequence of heating. In contrast, TD-FiberLIG declined in close association with heating, largely because TD-FiberLIG was sensitive to changes in concentrations of both NDFn and acid detergent lignin. Discrepancies between TDN-LIG and TDN-NDFD were exacerbated further when neutral detergent fiber rather than NDFn was used to estimate TD-FiberNDFD. Estimates of TDN declined by as much as 13.0 percentage units within severely heated hays, and this is a serious consequence of spontaneous heating.     

Effects of a propionic acid-based preservative on storage characteristics, nutritive value, and energy content for alfalfa hays packaged in large round bales

During 2009 and 2010, alfalfa (Medicago sativa L.) hays from 2 cuttings harvested from the same field site were used to evaluate the effects of a propionic acid-based preservative on the storage characteristics and nutritive value of hays stored as large round bales. A total of 87 large round bales (diameter = 1.5m) were included in the study; of these, 45 bales served as controls, whereas 42 were treated with a commercial propionic acid-based preservative at mean application rates of 0.5±0.14 and 0.7±0.19% of bale weight, expressed on a wet (as is) or dry matter basis, respectively. Initial bale moisture concentrations ranged from 10.2 to 40.4%. Internal bale temperatures were monitored daily during an outdoor storage period, and heating characteristics were summarized for each bale as heating degree days (HDD) >30°C. For acid-treated bales, the regression relationship between HDD and initial bale moisture was best fitted to a quadratic model in which the linear term was dropped to improve fit (Y=2.02x(2) - 401; R(2)=0.77); control hays were best fitted to a nonlinear model in which the independent variable was squared [Y=4,112 - (4,549×e(-0.000559x*x)); R(2)=0.77]. Based on these regressions, acid-treated bales accumulated more HDD than control hays when the initial bale moisture was >27.7%; this occurred largely because acid treatment tended to prolong active heating relative to control hays. Linear regressions of recoveries of dry matter on HDD did not differ on the basis of treatment, yielding a common linear relationship of Y=-0.0066x+96.3 (R(2)=0.75). Regressions relating changes (post-storage - pre-storage) in concentrations of several nutritional components (neutral detergent fiber, lignin, ash, crude protein, and total digestible nutrients) with HDD for acid-treated hays typically exhibited more inflection points or were higher-ordered polynomial regressions than those of control hays. These more complex responses probably reflected the perturbation of normal heating patterns following acid treatment; however, overall effects on post-storage nutritive value were relatively limited in scope. The potential to improve nutritive value relative to cost for these large round bales was not especially favorable, and hay producers may find that diligence to achieve adequate field desiccation before baling, or use of oxygen-exclusion methods, such as wrapping in plastic, may be better alternatives for preserving moist hays.     

Storage characteristics,nutritive value,energy content,and in vivo digestibility of moist,large rectangular bales of alfalfa-orchardgrass hay treated with a propionic acid-based preservative

Unstable weather, poor drying conditions, and unpredictable rainfall events often place valuable hay crops at risk. Recent research with large round bales composed of alfalfa (Medicago sativa L.) and orchardgrass (Dactylis glomerata L.) has shown that these large-bale packages are particularly sensitive to spontaneous heating and dry matter (DM) losses, as well as other undesirable changes with respect to forage fiber, protein, and energy density. Various formulations of organic acids have been marketed as preservatives, normally for use on hays that are not desiccated adequately in the field to facilitate safe bale storage. Our objectives for this study were to (1) evaluate the efficacy of applying a commercial (buffered) propionic acid-based preservative at 3 rates (0, 0.6, and 1.0% of wet-bale weight) to hays baled at 3 moisture concentrations (19.6, 23.8, and 27.4%) on the subsequent storage characteristics and poststorage nutritive value of alfalfa-orchardgrass forages packaged in large rectangular (285-kg) bales, and then (2) evaluate the in vivo digestibility of these hays in growing lambs. Over a 73-d storage period, the preservative was effective at limiting spontaneous heating in these hays, and a clear effect of application rate was observed for the wettest (27.4%) bales. For drier hays, both acid-application rates (1.0 and 0.6%) yielded comparable reductions in heating degree days >30°C relative to untreated controls. Reductions in spontaneous heating could not be associated with improved recovery of forage DM after storage. In this study, most changes in nutritive value during storage were related to measures of spontaneous heating in simple linear regression relationships; this suggests that the modest advantages in nutritive value resulting from acid treatment were largely associated with perturbations of normal heating patterns during bale storage. Although somewhat erratic, apparent digestibilities of both DM (Y = −0.0080x + 55.6; R² = 0.45) and organic matter (Y = −0.0085x + 55.5; R² = 0.53) evaluated in growing lambs were also directly related to heating degree days in simple linear relationships. Based on these data, applying propionic acid-based preservatives to large rectangular bales is likely to provide good insurance against spontaneous heating during storage, as well as modest benefits with respect to nutritive value and digestibility.     

Estimation of feed crude protein concentration and rumen degradability by Fourier-transform infrared spectroscopy

Currently, rapid methods are needed for feed analysis. This study examined the potential of Fourier-transform infrared (FTIR) spectroscopy to predict the nutritional value of a wide range of feeds for ruminants, as an alternative to the in situ technique. Moreover, we investigated whether universal equations could be developed that would allow the low-cost determination of crude protein (CP) concentrations and their kinetics of degradation into the rumen. Protein nutritional values of 663 samples comprising 80 different feed types were determined in terms of concentrations of CP, water-soluble CP (CP_WS), total-tract mobile bag CP digestibility (CP_TTD), and in situ CP degradability, including the rumen soluble fraction (CP_A), the degradable but not soluble fraction (CP_B), rate of CP_B degradation (CP_C), effective degradability (CP_ED), and potential degradability (CP_PD). Infrared spectra of dry samples were collected by attenuated total reflectance from 4000 to 600 cm⁻¹. Models were developed by partial least squares (PLS) regression in a randomly selected subset of samples, and the precision of the equations was confirmed by using an external validation set. Analysis by FTIR spectroscopy was sufficiently sensitive to allow the accurate prediction of sample CP concentration (R² = 0.92) and to classify feeds according to their CP_WS concentrations using universal models (R² = 0.78) that included all sample types. Moreover, substantial improvements in predictions were observed when samples were subdivided in groups. Models for forages led to accurate predictions of CP_WS and fractions CP_A and CP_B (R² > 0.83), whereas models for CP_TTD and CP_ED could be used for screening purposes (R² > 0.67). This study showed that models for protein-rich concentrates alone could also be used for screening according to the feed concentrations of CP_WS, CP_TTD, CP_ED, CP_A, and CP_B, but models for energy-rich concentrates gave relatively poor predictions. The general difficulty observed in predicting CP_C is because of a low correlation between FTIR spectra and the kinetics of CP degradation, which may be the result of large variation in the reference method (i.e., in situ degradation studies) and perhaps also because of the presence of compounds that can modify the CP degradation pattern in the rumen. In conclusion, FTIR spectroscopy should be considered as a low-cost alternative in the feed evaluation industry.     

Dietary starch source and protein degradability in diets containing sucrose: Effects on ruminal measures and proposed mechanism for degradable protein effects

A feeding study was conducted to evaluate ruminal effects of starch source (STA) and rumen-degradable dietary protein (RDP) in diets with added sucrose. The experimental design was an incomplete Latin square with three 21-d periods, 8 ruminally cannulated lactating cows, and a 2 × 2 factorial arrangement of treatments. Treatments were STA (dry ground corn or high-moisture corn) as more slowly and more rapidly fermenting starch sources, respectively, and relative amount of RDP (+RDP: added protein from soybean meal; −RDP: heat-treated expeller soybean product partially substituted for soybean meal). Diets were formulated to be isonitrogenous and similar in starch and neutral detergent fiber concentrations. Dry matter (DM) intake was 1 kg greater with +RDP compared with −RDP diets. For ruminal digesta measures made 2 h postfeeding, weight of digesta DM was unaffected by treatment; total kilograms of wet digesta and kilograms of liquid tended to be greater with +RDP than with −RDP, and no effect was observed of STA × RDP. Digesta DM percentage was greater with −RDP than with +RDP. At 2 h postfeeding, ruminal pool sizes (mol) of lactate and total AA were larger and those of total organic acids (OA) and ammonia tended to be larger with +RDP than with −RDP; no effects of STA or STA × RDP were detected. Rumen-degradable protein effects on lactate and OA pool sizes may be due to a protein-mediated increase in fermentation rate of carbohydrate. Organic acid concentrations at 2 h postfeeding did not show the same response pattern or significance as the pool size data; high-moisture corn tended to be greater than dry ground corn and no effect was observed for RDP or STA × RDP. Concentration and pool size for OA were more weakly correlated [coefficient of determination (R²) = 0.66] than was the case for other ruminal analytes (R² >0.80). Organic acid pool size and kilograms of digesta liquid were strongly correlated (R² = 0.79), whereas concentration and kilograms of liquid were much less so (R² = 0.21). The correlation of OA moles with kilograms of liquid likely relates to the homeostatic mechanism of water flux across the rumen wall to reduce the osmotic gradient with blood as intraruminal moles of solute change. This action compresses the range of ruminal OA concentrations. With kilograms of ruminal liquid differing across individual measurements, the ruminal OA concentration data are not on the equivalent basis required to be reliably useful for assessing the effect of treatments. Further evaluation of protein effects on carbohydrate fermentation and of methods that allow accurate comparison of treatments for their effect on ruminal OA production are warranted.     

Microwave improvement of soy protein isolate–saccharide graft reactions

Soy protein isolate (SPI) was mixed with lactose, maltose, dextran or soluble starch (SS) and heated (temperature ?90 °C) by microwave irradiation. Compared to the classical heating, the microwave heating (MH) speeded up the graft reactions of SPI with sugars. From the results calculated, the rate constants of free amino groups in the grafts of SPI with lactose, maltose, dextran and SS by MH were, respectively, 6, 7, 57 and 12.3 times of those by classical heating. After heating by microwave, the lysine and arginine decreased and from, the FTIR spectroscopy of SPI and its grafts by MH, the absorbance of –C–O stretching and –OH deformation vibrations (1050–1150 cm⁻¹) and free –OH form (3643–3630 cm⁻¹) in SPI grafts increased compared to SPI. The temporal development of the graft reactions of SPI with sugars by MH was also shown by SDS–PAGE.     

Dietary cation-anion difference and dietary protein effects on performance and acid-base status of dairy cows in early lactation

Our objective was to examine the effects of dietary cation-anion difference (DCAD) with different concentrations of dietary crude protein (CP) on performance and acid-base status in early lactation cows. Six lactating Holstein cows averaging 44 d in milk were used in a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of treatments: DCAD of −3, 22, or 47 milliequivalents (Na + K - Cl - S)/100 g of dry matter (DM), and 16 or 19% CP on a DM basis. Linear increases with DCAD occurred in DM intake, milk fat percentage, 4% fat-corrected milk production, milk true protein, milk lactose, and milk solids-not-fat. Milk production itself was unaffected by DCAD. Jugular venous blood pH, base excess and HCO₃⁻ concentration, and urine pH increased, but jugular venous blood Cl⁻ concentration, urine titratable acidity, and net acid excretion decreased linearly with increasing DCAD. An elevated ratio of coccygeal venous plasma essential AA to nonessential AA with increasing DCAD indicated that N metabolism in the rumen was affected, probably resulting in more microbial protein flowing to the small intestine. Cows fed 16% CP had lower urea N in milk than cows fed 19% CP; the same was true for urea N in coccygeal venous plasma and urine. Dry matter intake, milk production, milk composition, and acid-base status did not differ between the 16 and 19% CP treatments. It was concluded that DCAD affected DM intake and performance of dairy cows in early lactation. Feeding 16% dietary CP to cows in early lactation, compared with 19% CP, maintained lactation performance while reducing urea N excretion in milk and urine.     

Effects of Chemical Drying Agents and Preservatives on Composition and Digestibility of Alfalfa Hay

Effects of chemicals as drying agents applied at time of cutting or organic acids applied as preservatives at time of baling on composition and digestibility of alfalfa (Medicage sativa L.) hays were studied in three experiments, two with large round bales and one with square bales. Potassium carbonate-treated hays or commercial product-treated hays dried somewhat faster than control hays. Hays moist enough to sustain heating gradually increased in percentages of CP, ADF, and NDF with concomitant deterioration in visual quality and measured estimates of digestibility. These changes appear associated with greater loss of more readily fermentable carbohydrates. Lower density of large round bales resulted in less heating, spoilage, and increased digestibility of hay baled above 25% moisture. Hay above 30% moisture made in 1 d with a combination of drying agent applied at time of cutting and application of propionic acid and acetic acid (80:20) at baling maintained high quality for nearly 2 mo, but in vitro organic matter digestibilities declined thereafter as compared with other treated hays baled at lower moisture contents. Mold spore counts in this hay, measured after 6 mo in storage, were 20 times higher, which suggested mold inhibition by acid treatment was effective only initially and waned with time.     

Effects of time at suboptimal pH on rumen fermentation in a dual-flow continuous culture system

Ruminal pH varies considerably during the day, achieving values below 6.0 when cows consume large amounts of concentrates. Low ruminal pH has negative effects on ruminal fermentation. However, previous studies have indicated that rumen bacteria may resist short periods of low ruminal pH, and it is not clear how long this period may be before rumen microbial fermentation is negatively affected. Seven dual-flow continuous culture fermenters (1,320 mL) were used in 3 replicated periods with the same diet (97 g of dry matter/d of a 60:40 forage-to-concentrate diet, 18.3% crude protein, 35.9% neutral detergent fiber), temperature (39°C), and solid (5%/h) and liquid (10%/h) dilution rates to study the effects of increasing time at suboptimal pH on rumen microbial fermentation and nutrient flow. Treatments were a constant pH of 6.4 and 6 different intervals of time during the day (4, 8, 12, 16, 20, 24 h) at suboptimal pH (5.5), with the rest of the day being at pH 6.4. Polynomial equations were derived using the Mixed procedure of SAS, and linear, quadratic and cubic terms were left in the equation if P < 0.10. True organic matter digestion decreased with increasing time at suboptimal pH and was best described by a cubic regression (TOMD = 58.5 − 2.15x + 0.16x² −0.0037x³; R² = 0.74). Digestion of NDF (DNDF = 55.1 − 1.00x; R² = 0.75) and digestion of ADF (DADF = 56.2 − 1.33x; R² = 0.78) decreased linearly with increasing time at suboptimal pH. Total VFA had a cubic response (VFA = 112.7 − 2.09x + 0.17x² − 0.0054x³; R² = 0.82). The proportion of acetate decreased linearly (acetate = 58.7 − 0.61x; R² = 0.79). The propionate proportion increased (propionate = 17.6 + 2.09 × −0.044x²; R² = 0.85) and branched-chain VFA decreased (BCVFA = 4.45 −0.51x + 0.014x²; R² = 0.75) quadratically. The ammonia N concentration (NH₃-N = 5.85 − 0.13x; R² = 0.46) and flow (NH₃-N flow = 0.18 − 0.0039x; R² = 0.43) decreased linearly as the time at suboptimal pH increased. Crude protein degradation (CPd = 41.9 − 1.60x + 0.060x²; R² = 0.71), efficiency of microbial protein synthesis (EMPS = 26.6 − 0.33x + 0.021x²; R² = 0.77), microbial N flow (MN flow = 1.38 − 0.036x + 0.0015x²; R² = 0.77), and dietary N flow (DN flow = 1.49 + 0.041x − 0.0015x²; R² = 0.65) had a quadratic response. The flow of essential, nonessential, and most individual AA increased linearly with increasing time at suboptimal pH. The effects of pH on rumen fermentation appear to start as soon as pH drops to suboptimal pH.     

Improved Feed Protein Fractionation Schemes for Formulating Rations with the Cornell Net Carbohydrate and Protein System

Adequate predictions of rumen-degradable protein (RDP) and rumen-undegradable protein (RUP) supplies are necessary to optimize performance while minimizing losses of excess nitrogen (N). The objectives of this study were to evaluate the original Cornell Net Carbohydrate Protein System (CNCPS) protein fractionation scheme and to develop and evaluate alternatives designed to improve its adequacy in predicting RDP and RUP. The CNCPS version 5 fractionates CP into 5 fractions based on solubility in protein precipitant agents, buffers, and detergent solutions: A represents the soluble nonprotein N, B1 is the soluble true protein, B2 represents protein with intermediate rates of degradation, B3 is the CP insoluble in neutral detergent solution but soluble in acid detergent solution, and C is the unavailable N. Model predictions were evaluated with studies that measured N flow data at the omasum. The N fractionation scheme in version 5 of the CNCPS explained 78% of the variation in RDP with a root mean square prediction error (RMSPE) of 275 g/d, and 51% of the RUP variation with RMSPE of 248 g/d. Neutral detergent insoluble CP flows were overpredicted with a mean bias of 128 g/d (40% of the observed mean). The greatest improvements in the accuracy of RDP and RUP predictions were obtained with the following 2 alternative schemes. Alternative 1 used the inhibitory in vitro system to measure the fractional rate of degradation for the insoluble protein fraction in which A = nonprotein N, B1 = true soluble protein, B2 = insoluble protein, C = unavailable protein (RDP: R² = 0.84 and RMSPE = 167 g/d; RUP: R² = 0.61 and RMSPE = 209 g/d), whereas alternative 2 redefined A and B1 fractions as the non-amino-N and amino-N in the soluble fraction respectively (RDP: R² = 0.79 with RMSPE = 195 g/d and RUP: R² = 0.54 with RMSPE = 225 g/d). We concluded that implementing alternative 1 or 2 will improve the accuracy of predicting RDP and RUP within the CNCPS framework.     

Relationships between dry matter content,ensiling, ammonia-nitrogen,and ruminal in vitro starch digestibility in high-moisture corn samples

The objectives of the study were (1) to determine relationships between high-moisture corn (HMC) dry matter (DM), ammonia-N [% of crude protein (CP)], and soluble CP concentrations, and pH, with 7-h ruminal in vitro starch digestibility (ivStarchD), and (2) to evaluate the effect of ensiling on pH, ammonia-N, soluble CP, and ivStarchD measurements in HMC. A data set comprising 6,131 HMC samples (55 to 80% DM) obtained from a commercial feed analysis laboratory was used for this study. Month of sample submittal was assumed to be associated with length of the ensiling period. Data for month of sample submittal were analyzed using Proc Mixed in SAS (SAS Institute Inc., Cary, NC) with month as a fixed effect. Regressions to determine linear and quadratic relationships between ivStarchD and ammonia-N, soluble CP, pH, and DM content were performed using Proc Mixed. The ivStarchD increased by 9 percentage units from October to August of the following year. Similar results were observed for ammonia-N and soluble CP with increases from 1.8 to 4.6% of CP and 31.3 to 46.4% of CP, respectively, from October to August of the following year. Ammonia-N was positively related to ivStarchD (R² = 0.61). The DM content of HMC at silo removal was negatively related (R² = 0.47) to ivStarchD with a decrease of 1.6 percentage units in ivStarchD per 1-percentage-unit increase in DM content. The pH of HMC was negatively related to ammonia-N (R² = 0.53), soluble CP (R² = 0.57), and ivStarchD (R² = 0.51). Combined, ammonia-N, DM, soluble CP, and pH provided a good prediction of ivStarchD (adjusted R² = 0.70). Increasing pH, ammonia-N, soluble CP, and ivStarchD values indicate that HMC may need up to 10 mo of ensiling to reach maximum starch digestibility. Ammonia-N, DM content, soluble CP concentration, and pH are good indicators of ruminal in vitro starch digestibility for high-moisture corn.     

Determination of resveratrol in grains,hulls and leaves of common and tartary buckwheat by HPLC with electrochemical detection at carbon paste electrode

A reverse-phase high-performance liquid chromatographic method for the determination of trans-resveratrol with spectrophotometric detection (306 nm) and amperometric detection at carbon paste electrode (E = + 1,2 V) was developed and tested on real samples of grains, hulls and leaves of six varieties of common buckwheat (Fagopyrum esculentum Möench) and two varieties of tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.). Optimal conditions for the determination of trans-resveratrol were as follows: column Kromasil C-18 (7 μm), 125 × 4 mm; mobile phase acetonitrile: diluted BR buffer pH 7 (50:50, 30:70 for grains and hulls and 20:80 for leaves); flow rate 1 ml min⁻¹. Under these conditions, the limit of detection of trans-resveratrol (L_D) was 3.5 × 10⁻⁸ mol l⁻¹ (R² = 0.9986) for electrochemical detection and 3.2 × 10⁻⁸ mol l⁻¹ (R² = 0.9993) for spectrophotometric detection.     

Effect of dietary crude protein modification on ammonia and nitrous oxide concentration on a tie-stall dairy barn floor

Dietary crude protein (CP) reduction is considered a useful strategy to minimize cow N excretion and NH₃ and N₂O emissions. The aim of the current work was to relate dietary CP modification to whole-animal N balance and subsequent NH₃ and N₂O concentrations on a tie-stall barn floor. The effect of temperature on NH₃ and N₂O concentration was also studied. Three Holstein mid to late lactating cows were confined in separate tie-stalls and randomly assigned to 3 diets with varying CP content [low CP (LCP): 14.1%; moderate CP (MCP): 15.9%; high CP (HCP): 16.9%]. Increasing N intake (from 438.6 to 522.8 g of N/d) improved milk yield (from 22.1 to 24.2 kg/d). However, N use efficiency tended to decrease with increasing dietary CP, as shown by milk N use efficiency (from 23.9 to 22.6%), milk urea N (from 15.4 to 18.7 mg/dL), and excreted N per milk yield unit (from 14.7 to 16.4 g of N/kg of milk). Because of higher N excretion, NH₃ concentration on the dairy barn floor increased (LCP: 7.1 mg of NH₃/m³; MCP: 10.4 mg of NH₃/m³; HCP: 10.8 mg of NH₃/m³). In contrast, N₂O concentration did not respond to dietary manipulation (mean 1.1 mg of N₂O/m³). Temperature, which ranged between 12.6 and 18.0°C, did not affect NH₃ and N₂O concentrations at the stall level. However, when fecal and urinary samples were incubated at 4, 19, and 29°C in the laboratory, ammonia concentration increased for all diets, especially for the MCP and HCP diets, as the temperature increased. In contrast, N2O concentration was negatively related to increasing temperature. In conclusion, data from the current trial demonstrate that lowering dietary CP minimizes NH₃ concentration on dairy stall floors although temperature controls the rate of NH₃ volatilization. On the other hand, N₂O concentration is not affected by dietary treatments on tie-stall floors.     

Ruminal degradability of dry matter,crude protein,and amino acids in soybean meal,canola meal,corn, and wheat dried distillers grains

Different protein sources, such as canola meal (CM) or dried distillers grains (DDG), are currently used in dairy rations to replace soybean meal (SBM). However, little data exists comparing their rumen degradation in a single study. Therefore, the objective of this study was to compare the ruminal degradation of dry matter (DM), crude protein (CP), and AA of SBM, CM, high-protein corn DDG (HPDDG), and wheat DDG plus solubles (WDDGS). In situ studies were conducted with 4 rumen-fistulated lactating Holstein cows fed a diet containing 38% grass hay and 62% corn-based concentrate. Each protein source was incubated in the rumen of each cow in nylon bags for 0, 2, 4, 8, 16, 24, and 48 h to determine DM and CP rumen degradation kinetics, whereas additional bags were also incubated for 16 h to evaluate AA ruminal disappearance. Rumen DM and CP degradability was calculated from rumen-undegraded residues corrected or not for small particle loss. Data were fitted to an exponential model to estimate degradation parameters and effective degradability (ED) was calculated with a passage rate of 0.074 h⁻¹. The WDDGS and SBM had higher uncorrected ED (DM = 75.0 and 72.6%; CP = 84.8 and 66.0%, respectively) than CM and HPDDG (DM = 57.2 and 55.5%; CP = 59.3 and 48.2%, respectively), due to higher soluble fraction in WDDGS and a combination of higher potentially degradable fraction and rate of degradation in SBM. Correction for small particle loss from bags, higher for WDDGS than for the other protein sources, decreased estimated ED but did not alter feed ranking. The ruminal disappearance of AA after 16 h of incubation reflected the overall pattern of CP degradation between protein supplements, but the ruminal disappearance of individual AA differed between protein supplements. Overall, these results indicate that, in the current study, (1) SBM and WDDGS were more degradable in the rumen than CM and HPDDG, and (2) that small particle loss correction is relevant but does not alter this ranking.     

Unique interrelationships between fiber composition,water-soluble carbohydrates,and in vitro gas production for fall-grown oat forages

Sixty samples of ‘ForagePlus’ oat were selected from a previous plot study for analysis of in vitro gas production (IVGP) on the basis of 2 factors: (1) high (n = 29) or low (n = 31) neutral detergent fiber (NDF; 62.7 ± 2.61 and 45.1 ± 3.91%, respectively); and (2) the range of water-soluble carbohydrates (WSC) within the high- and low-NDF groups. For the WSC selection factor, concentrations ranged from 4.7 to 13.4% (mean = 7.9 ± 2.06%) and from 3.5 to 19.4% (mean = 9.7 ± 4.57%) within high- and low-NDF forages, respectively. Our objectives were to assess the relationships between IVGP and various agronomic or nutritional characteristics for high- and low-NDF fall-oat forages. Cumulative IVGP was fitted to a single-pool nonlinear regression model: Y = MAX × (1 – e ^{[–K× (t – lag)]}), where Y = cumulative gas produced (mL), MAX = maximum cumulative gas produced with infinite incubation time (mL), K = rate constant, t = incubation time (h), and lag = discrete lag time (h). Generally, cumulative IVGP after 12, 24, 36, or 48 h within high-NDF fall-oat forages was negatively correlated with NDF, hemicellulose, lignin, and ash, but positively correlated with WSC, nonfiber carbohydrate (NFC), and total digestible nutrients (TDN). For low-NDF fall-grown oat forages, IVGP was positively correlated with growth stage, canopy height, WSC, NFC, and TDN; negative correlations were observed with ash and crude protein (CP) but not generally with fiber components. These responses were also reflected in multiple regression analysis for high- and low-NDF forages. After 12, 24, or 36 h of incubation, cumulative IVGP within high-NDF fall-oat forages was explained by complex regression equations utilizing (lignin:NDF)², lignin:NDF, hemicellulose, lignin, and TDN² as independent variables (R² ≥ 0.43). Within low-NDF fall-grown oat forages, cumulative IVGP at these incubation intervals was explained by positive linear relationships with NFC that also exhibited high coefficients of determination (R² ≥ 0.75). Gas production was accelerated at early incubation times within low-NDF forages, specifically in response to large pools of WSC that were most likely to be present as forages approached boot stage by late-fall.     

Effect of dietary crude protein concentration on ruminal nitrogen metabolism in lactating dairy cows

Ten lactating Holstein cows fitted with ruminal cannulas that were part of a larger feeding trial were blocked by days in milk into 2 groups and then randomly assigned to 1 of 2 incomplete 5 × 5 Latin squares. Diets contained [dry matter (DM) basis] 25% alfalfa silage, 25% corn silage, and 50% concentrate. Rolled high-moisture shelled corn was replaced with solvent-extracted soybean meal to increase crude protein (CP) from 13.5% to 15.0, 16.5, 17.9, and 19.4% of DM. Each of the 4 experimental periods lasted 28 d with data and sample collection performed during the last 8 d. Digesta samples were collected from the omasum to quantify the ruminal outflow of different N fractions. Intake of DM was not affected but showed a quadratic trend with maxima of 23.9 kg/d at 16.5% CP. Ruminal outflow of total bacterial nonammonia N (NAN) was not different among diets but a significant linear effect of dietary CP was detected for this variable. Bacterial efficiency (g of total bacterial NAN flow/kg of organic matter truly digested in the rumen) and omasal flows of dietary NAN and total NAN also showed positive linear responses to dietary CP. Total NAN flow increased from 574 g/d at 13.5% CP to 688 g/d at 16.5% CP but did not increase further with the feeding of more CP. Under the conditions of this study, 16.5% of dietary CP appeared to be sufficient for maximal ruminal outflow of total bacterial NAN and total NAN.     

Selective determination of chloramphenicol at trace level in milk samples by the electrode modified with molecularly imprinted polymer

A novel voltammetric sensor for determination of chloramphenicol (CAP) in milk samples was introduced. The CAP selective molecularly imprinted polymer (MIP) and non imprinted polymer (NIP) were synthesized and then added to the carbon paste (CP) electrode composition in order to prepare MIP-CP electrode. The MIP, embedded in the carbon paste electrode, acted as the selective recognition element and pre-concentrator agent for CAP. CAP was extracted in the electrode for a definite time and then it was analyzed by differential pulse voltametry, found to be an effective determination method. The MIP-CP showed very high CAP recognition ability, compared to NIP-CP. The electrode washing, after CAP extraction, led to an enhanced selectivity. Various factors, known to affect the response behavior of the electrode, were investigated and optimized. This sensor showed a linear response range of 8.0 × 10⁻⁹−1.0 × 10⁻⁶ M and lower detection limit of 2.0 × 10⁻⁹ M (S/N = 3). The sensor was successfully applied to the determination of CAP in milk samples.     

Degradation kinetics of anthocyanins in acerola pulp: Comparison between ohmic and conventional heat treatment

Degradation kinetics of monomeric anthocyanins in acerola pulp during thermal treatment by ohmic and conventional heating was evaluated at different temperatures (75–90 °C). Anthocyanin degradation fitted a first-order reaction model and the rate constants ranged from 5.9 to 19.7 × 10⁻³ min⁻¹. There were no significant differences between the rate constants of the ohmic and the conventional heating processes at all evaluated temperatures. D-Values ranged from 116.7 to 374.5 for ohmic heating and from 134.9 to 390.4 for conventional heating. Values of the free energy of inactivation were within the range of 100.19 and 101.35 kJ mol⁻¹. The enthalpy of activation presented values between 71.79 and 71.94 kJ mol⁻¹ and the entropy of activation ranged from −80.15 to −82.63 J mol⁻¹ K⁻¹. Both heating technologies showed activation energy of 74.8 kJ mol⁻¹ and close values for all thermodynamic parameters, indicating similar mechanisms of degradation.