Effect of Moisture Content at Baling on Nutritive Value of Alfalfa Orchardgrass Hay in Conventional and Large Round Bales

Alfalfa-orchargrass herbage was harvested for hay at 23, 18, and 13% moisture and stored in conventional and large round hay bales. After 5 mo of storage indoors, hay was higher in acid detergent insoluble nitrogen if baled at 23 than at 18% moisture. This was due to increased internal temperature of the bales, which reached a peak of 90°C at the center of large bales stored at 23% moisture. Acid detergent fiber and acid insoluble lignin increased in hay at the center of round bales compared with the outer layer or shell or that in conventional bales. In vivo digestibilities of dry matter, protein, and acid detergent fiber were significantly reduced in the inside core and outside shell of large round bales stored at 23% moisture compared with conventional bales of equal moisture content. Protein digestibility was depressed only slightly in the core of hay stored in large round bales at 18% moisture. These data show that round bales are more susceptible to heat damage than conventional bales made at the same moisture content.     

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.     

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.     

Effect of microbial inoculant on quality of alfalfa hay baled at high moisture and lamb performance.

The effectiveness of a microbial hay inoculant in high moisture alfalfa hay was evaluated. Alfalfa (third cutting) was baled at 72% DM without or with inoculant and at 82% DM without inoculant during yr 1. In yr 2, alfalfa (second cutting) was baled at 75% DM without or with inoculant and at 82% DM without inoculant. Application rate of inoculant was 3.8 L/.98 tonne each year. At this application rate, 90 billion cfu were applied per .98 tonne of forage. Hays were core sampled at 0, 14, 30, and 60 d after baling to determine chemical composition. By d 30, all hays had DM content of 89%. In yr 2, 12 wether lambs were assigned to three treatments in a replicated 3 x 3 Latin square. Treatments were chopped, low moisture hay plus corn; chopped, inoculated high moisture hay plus corn; and chopped, high moisture hay plus corn. All diets contained 63% alfalfa hay, 35% ground corn, and 2% minerals and vitamins. In yr 1, inoculated and low moisture hays were not different in chemical composition but were higher in CP and lower in NDF than high moisture hay. Neither NDF nor CP were different among the three hays in yr 2. Average daily gain was not different on the three diets. The feed to gain ratio was lowest for the inoculated hay, intermediate for the low moisture hay, and highest for the high moisture hay diet. Daily gain and feed to gain ratio were not different for lambs fed the inoculated hay baled at 75% DM compared with lambs fed untreated hay baled at 82% DM.     

Preservation of moist hay in miniature bales treated with propionic acid

In 2 experiments, propionic acid was applied by hand-sprayer to partly dried hay which was made into miniature bales of about 1 kg. In an experiment in which the hay moisture content was 51%, acid was applied at 0%, 1%, 2%, 4%, 6% and 8% by weight. Bales with less than 4% acid showed severe heating, moulding, and losses of dry matter and nutrient content within a few weeks. Bales with 4% acid or more were still well preserved after 3 months. In a second experiment hays of 32% and 41% moisture showed moulding at 0.5% and 1.0% acid respectively, but slight or no moulding at 1.0% and 1.5% acid. At 48%, 59% and 76% moistures the lowest acid levels used, 2%, 3% and 3.5% respectively, all prevented moulding.It was concluded that acid treatments of 1%, 1%–1.5%, and 2% for hays of 30%, 40% and 50% moisture respectively were on the margin between being effective and ineffective in the preservation of hay stored under experimental conditions.     

Effect of chemical drying agents on alfalfa hay and milk production response when fed to dairy cows in early lactation

Third-cutting alfalfa hay cut at bud stage was treated with a drying agent consisting of potassium carbonate, sodium carbonate, and citric acid at the rate of 280.6 L/ha (1 kg/37.47 L water) to alternate swaths 4.27-m wide. Hay samples were taken at cutting and at 4-h intervals during daylight until baling was initiated. Twenty lactating Holstein cows were randomly assigned to untreated and treated alfalfa hay treatments in a switch-back design. Individual feed intakes and milk yields were recorded daily. Milk composition was analyzed once weekly. Drying rates were: .40 and .48% moisture/h for control and Na2-K2CO3-citrate treatments, respectively. There was no significant difference between treatments in feed composition parameters nor in vitro DM digestibility parameters. Cows fed the hay treated with Na2-K2CO3-citrate had a higher mean daily milk yield, adjusted for feed intake, compared with cows fed untreated hay (33.0 versus 32.5 kg/d). There were no significant differences in milk composition between treatments.     

Comparison of Alfalfa-Orchardgrass Hay Stored in Large Round Bales and Conventional Rectangular Bales for Lactating Cows

Lactating Jersey cows were used in two trials to evaluate alfalfa-orchardgrass hay baled and stored by the following methods: 1) conventional rectangular bales; 2) large round bales, stored inside; and 3) large round bales, stored outside. Half the round bales stored outside in trial 1 were stored on automobile tires and the other half were stored on the gound. In trial 2, half of the bales stored outside were partially covered with plastic caps and the other half were exposed to the weather. Covariance adjusted milk production was significantly higher for inside over outside storage in trial 1 and for conventional over round bales and covered over exposed in trial 2.In trial 1, utilization by cows as a percent of dry matter baled was 92.9, 74.0, and 66.6% for round bales stored inside, stored outside on tires, and stored outside on the ground. Percents were 86.8, 88.8, and 65.0% for round bales stored inside, stored outside covered, and stored outside exposed in trial 2. Storing round bales on automobile tires effectively reduced bottom spoilage. Covers of polyethylene film reduced weather deterioration and feeding waste of covered bales to amount of bales stored inside.     

Nutritive value of high moisture alfalfa hay preserved with urea

Urea (2 and 4%) was added to high moisture hays and compared with untreated wet or dry hays. Means for bale temperatures (degree C) for 1 wk postharvest were highest for wet control (41.2), lowest for dry control (31.4), and intermediate for urea treatments (36.7). By 4 wk postharvest, all temperatures were equal. Protection from molding was most effective for 4% urea, and 2% urea was superior to wet control. By 4 mo postharvest, CP for low urea had decreased due to NH3 loss, and CP for wet control had increased due to DM loss, so they were not different. Initially, ADF was similar for the hays, but after 4 mo storage the wet control was highest (41.7%), the dry control lowest (36.0%), and urea treatments intermediate. Lignin and NDF followed similar trends. In vitro DM digestibilities were highest for the wet control at harvest but lowest at 120 d with high urea and dry control greater than low urea. Feed intakes and milk yields in lactating cows fed the hays were not different. These data show that addition of 2 or 4% urea improved quality of hay baled at about 25% moisture; high urea was more effective than low urea.     

Preservation of moist hay with propionic acid

Propionic acid was applied to hay (i) of 27, 35 and 45% moisture contents at rates of nil, 1, 2, 3 and 4% by a high pressure applicator fitted to the baler; and (ii) of 25% moisture content at nil, 2.5, 3.2 and 5% and of 35% moisture content at 2.5 and 5% by a low pressure applicator. Hays from (i) were stored in 9-bale batches and those from (ii) in 50-bale batches.Increasing levels of acid progressively delayed and reduced moulding, heating and losses of dry matter, water-soluble carbohydrates and moisture. Only at the lowest moisture levels, 27 and 25%, was moulding completely eliminated, this at acid levels of (i) 2, 3 and 4% and (ii) 5%. In these batches slight cellular heating occurred during the first few days of storage, and dry matter losses were below 5%. Patches of fungal growth occurred on (i) 20–85% and (ii) 6–21% of the hay in the other treated batches. All controls were 100% mouldy.Unlike the controls, the acid treated batches showed wide temperature differences between individual bales; this was probably brought about by a combination of unequal acid distribution and variable moisture content. Thermophilic actinomycetes were isolated from both the treated and untreated hays which had been stored at 45% moisture content.     

Ruminal in vitro degradability of protein in alfalfa harvested as standing forage or baled hay.

Eighty-nine samples, 45 of standing forage and 44 of baled hay, were collected from alfalfa harvested at various maturities over three cuttings each during 2 yr. Alfalfa was cut and conditioned mechanically; samples of standing forage were collected by removing bunches of forage from windrows and freeze-drying them. Forage was allowed to field cure and was harvested at an average 80% DM as small rectangular bales; samples of baled hay were collected by coring bales after storing for 3 to 6 mo. Samples were analyzed for DM, ADF, total N, fractions of total N present as ADIN, N degraded at 0 h, and potentially degradable protein N. Ruminal protein degradation rates and escapes were estimated using an inhibitor in vitro system, assuming that ADIN was unavailable and that ruminal passage rate was .06/h. Standing forage contained smaller fractions of ADIN and N degraded at 0 h, contained a larger fraction of potentially degradable N, and had more rapid degradation rates and lower estimated protein escapes than baled hay. Mean degradation rates and estimated escapes were .171/h and 24% for standing forage and .075/h and 40% for baled hay. There were no differences in degradation rate or estimated escape because of harvest year, and neither was significantly related to maturity or to ADF concentration. Results indicate a significant advantage in ruminal protein escape, compared with grazed alfalfa, for alfalfa harvested and stored as hay.     

The relationship between the in vivo digestibility of hay and its solubility in pepsin–hydrochloric acid and fungal cellulase solutions

The determination of the solubility of the organic matter (OM) of hay in pepsin-hydrochloric acid and fungal cellulase solution according to the method of Jones and Hayward¹ gave reproducible results when applied to four hays with solubilities of 51.5, 49.1, 63.5 and 40.2%. In addition the correlation of the soluble OM determined by the cellulase solubility technique and in vivo digestibility studies for 34 hays produced highly significant correlations for the digestibility of the OM in the dry matter (DM) (r=0.91, RSD ± 2.180) and the OM digestibility (r=0.91, RSD ± 2.362). These data indicate that the determination of the solubility of OM in fungal enzyme solution is an acceptable method for the prediction of in vivo digestibility of the OM in the DM of hays.     

How to improve the hygienic quality of forages for horse feeding

BACKGROUND: Improving the hygienic quality of forages for horse nutrition seems to be a reasonable target for decreasing the prevalence of pulmonary diseases. The aim of the experiment was to study the effects of different agricultural practices on the main aero‐allergens contained in forages, including breathable dust, fungi, mycotoxins and pollens. RESULTS: Results showed that the late harvest of hay, a second crop or a haylage production provides a good alternative to increase hygienic quality by reducing fungi contamination and breathable dust content. Barn drying of hay, while having no effect on breathable dust, similarly reduced fungi contamination. In contrast, when hay was harvested at a lower dry mass content (750 g DM kg^?1 versus 850 g DM kg^?1), both breathable dust and fungi contaminations were increased, which could at least be reversed by adding propionic acid just before baling. Zearalenone was detected in different hays, and even in one case, in breathable dust. CONCLUSION: Overall, our data suggest that different approaches can be used to increase forage hygienic quality for horse feeding and thus reduce their exposure to factors involved in equine pulmonary disease. Copyright © 2011 Society of Chemical Industry     

Effects of spontaneous heating on forage protein fractions and in situ disappearance kinetics of crude protein for alfalfa-orchardgrass hays packaged in large round bales

During 2006 and 2007, forages from 3 individual hay harvests were used to assess the effects of spontaneous heating on concentrations of crude protein (CP), neutral detergent insoluble CP (NDICP), acid detergent insoluble CP (ADICP), and in situ disappearance kinetics of CP and NDICP 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. The change in concentrations of NDICP (poststorage − prestorage) increased with heating degree days (HDD) >30°C in a relationship best explained with a nonlinear model {Y = 24.9 - [22.7 × (e^{−0.000010 × x × x})]; R² = 0.892} that became asymptotic at +24.9 percentage units of CP, thereby indicating that NDICP increases rapidly within bales that heat spontaneously. When maximum internal bale temperature (MAX) was used as the independent variable, the best regression model was quadratic and the coefficient of determination was still relatively high (R² = 0.716). The change in concentrations of ADICP (poststorage − prestorage; ΔADICP) also increased with HDD and was best fitted to a nonlinear model {Y = 14.9 - [15.7 × (e^{−0.0000019 × x × x})]} with a very high coefficient of determination (R² = 0.934). A similar quartic response was observed for the regression of ΔADICP on MAX (R² = 0.975). Increases in ΔADICP as a result of heating (HDD or MAX) were paralleled by concurrent increases in hemicellulose at relatively low increments of heating, but the inverse relationship was observed as hemicelluloses likely became reactive and concentrations decreased in more severely heated hays. Changes in ruminal disappearance rate of CP were best fitted to cubic models for regressions on both HDD (R² = 0.939) and MAX (R² = 0.876); these changes represented an approximate 50% rate reduction in severely heated hays relative to prestorage controls. Within ranges of heating most commonly encountered under field conditions, changes in rumen-degradable protein decreased in a primarily linear relationship with HDD or MAX. However, the mean change in rumen-degradable protein for the 4 most severely heated hays was only −2.6 percentage units of CP, which represents a minimal reduction from prestorage controls and is far less than the maximum of −7.9 percentage units of CP observed with less-severe heating. Interpretation of these results was complicated by poor recovery of NDICP from our most severely heated hays following machine rinsing of 0-h Dacron bags; theoretically, and by definition, this unrecovered pool of NDICP is assumed to be entirely degradable in the rumen. It remains unclear whether these responses could be corroborated in vivo or by other analytical techniques, or whether the magnitude of HDD or MAX for our most severely heated hays exceeds the reliable limits for estimating RDP via in situ methodology.     

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.     

Silage review: Recent advances and future technologies for baled silages

Although the concept of ensiling large-round or large-square bales dates back to the late 1970s, many refinements have been made to both equipment and management since that time, resulting in much greater acceptance by small or mid-sized dairy or beef producers. This silage preservation technique is attractive to producers for several reasons, but the primary advantage is a reduced risk of weather damage to valuable forage crops compared with preservation as dry hay. Most core principles for making high-quality precision-chopped silages also apply to baled silages; among these, establishing and subsequently maintaining anaerobiosis are priorities. For baled silages, these priorities are critical, in part because recommended moisture concentrations (45 to 55%) are drier, and particle length is much longer. These factors act to restrict the rate and extent of silage fermentation, often resulting in less production of desirable fermentation acids and a greater (less acidic) final pH. Within this context, preservation of baled silages can be improved by applying polyethylene (PE) film wraps promptly, using an appropriate number of PE film layers (6 to 8), selecting a storage site free of sharp objects or other debris, and by monitoring wrapped bales closely for evidence of puncture, particularly by birds or vermin. Under certain conditions, such as those in which the bale moisture of highly buffered forages exceeds the recommended range, the heterogeneous nature of baled silages coupled with a restricted rate and extent of fermentation may increase susceptibility to clostridial activity compared with precision-chopped forages ensiled at comparable moisture concentrations. To date, research evaluating inoculants or other additives designed to improve the fermentation of challenging forages or aerobic stability has been limited, but should not be discontinued. Development of PE film embedded with an oxygen-limiting barrier has yielded positive results in some trials; however, most differences between these novel formulations and reputable commercial PE film have been related to decreases in yeast and mold counts at the surface layer. Related assessments of fermentation or nutritive value determined on a whole-bale basis have been less conclusive. Baled silages can be produced successfully by adhering to straightforward management principles; as such, this form of silage production is likely to remain popular for the foreseeable future.     

Aflatoxin formation in hay treated with formic acid and in isolated strains of Aspergillus flavus

The possibility of improving the keeping qualities of field-dried and hayloft-dried hay, with dry matter contents of 55 and 73% by adding sodium chloride, formic acid and propionic acid was investigated. Field-dried, sodium-chloride-treated hay was stored in containers, while controls and acid-treated hay were pressed into high-density bales. All hayloft-dried hay was stored in containers. Fungal attacks were very heavy, especially in the baled hay. The contaminating flora was examined at the temperature maximum and after 40 and 32 days storage for field-dried and hayloft-dried hay respectively. The genera Penicillium, Cladosporium and Trichothecium were predominant in hayloft-dried hay, and the differences between varying dry matter contents were insignificant. Mostly Aspergillus spp., but also Penicillium spp., occurred in the field-dried hay at 73% dry matter content but at 55% the flora consisted mostly of Aspergillus flavus, and the formic acid-treated hay contained almost a pure culture of this fungus. In addition, aflatoxin B₁ and G₁ (635–1000 μg/l) were demonstrated in this formic acid-treated hay.

Toxin formation in isolates of A. flavus from differently treated hay specimens was also investigated on various substrates.     

Degradation of Crude Protein in Forages Determined by In Vitro and In Situ Procedures

Objectives were to determine in selected forages fiber and protein fractions, in vitro and in situ CP degradability, and to compare in vitro methods of estimating rumen CP degradability with the in situ bag technique. Forages analyzed (five samples per treatment except alfalfa hays, which had four) included alfalfa as baled hay, alfalfa ensiled in conventional upright silos, alfalfa ensiled in oxygen-limiting silos, ammonia-treated corn silage, untreated corn silage, and orchardgrass hay. Untreated corn silages had the greatest protease insoluble CP at 48 h, indicating protein in corn silage is not degraded well by protease enzyme. In situ CP degradability was greater than 80% for all ensiled forages. Ensiled forages had the greatest estimated A fraction (rapidly degraded in the rumen), alfalfa hays had the greatest B fraction (intermediate rate of degradation), and orchardgrass hays had the greatest C fraction (not degraded in rumen).High correlations between in situ degradability and some in vitro measurements suggest laboratory techniques of estimating CP degradability of forages are possible. For silages, buffer-soluble CP had the greatest correlation (.58) with in situ degradability; for hays, NDIN had the greatest correlation (−.83).     

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.     

Effect of undigested neutral detergent fiber content of alfalfa hay on lactating dairy cows: Feeding behavior,fiber digestibility,and lactation performance

The objective of this study was to investigate the effects of 2 alfalfa hays differing in undigested neutral detergent fiber content and digestibility used as the main forage source in diets fed to high producing cows for Parmigiano-Reggiano cheese production. Diets were designed to have 2 different amounts of undigestible NDF [high (Hu) and low (Lu)], as determined by 240-h in vitro analysis (uNDF₂₄₀). Alfalfa hay in vitro digestibility [% of amylase- and sodium sulfite-treated NDF with ash correction (aNDFom)] at 24 and 240 h was 40.2 and 31.2% and 53.6 and 45.7% for low- (LD) and high-digestibility (HD) hays, respectively. The 4 experimental diets (Hu-HD, Lu-HD, Hu-LD, and Lu-LD) contained 46.8, 36.8, 38.8, and 30.1% of alfalfa hay, respectively, 8.6% wheat straw, and 35.3% corn (50% flake and 50% meal; DM basis). Soy hulls and soybean meal were used to replace hay to balance protein and energy among diets. Eight multiparous Holstein cows (average milk production = 46.0 ± 5.2 kg/d, 101 ± 38 d in milk, and 662 ± 42 kg of average body weight) were assigned to a 4 × 4 Latin square design, with 2 wk of adaptation and a 1-wk collection period. Dry matter and water intake, rumination time, ruminal pH, and milk production and composition were measured. Diets and feces were analyzed for NDF on an organic matter basis (aNDFom), acid detergent fiber, acid detergent lignin, and uNDF₂₄₀ to estimate total-tract fiber digestibility. Dry matter intake and rumination times were higher in HD diets compared with LD diets, regardless of forage amount. Rumination time was constant per unit of dry matter intake but differed when expressed as a function of uNDF₂₄₀, aNDFom, or physically effective NDF intake. No differences were found among treatments on average ruminal pH, but the amount of time with pH <5.8 was lower in Hu-HD diets. Milk production and components were not different among diets. Total-tract aNDFom and potentially digestible neutral detergent fiber fraction digestibility was higher for the LD diets (88.3 versus 85.8% aNDFom in HD), for which lower feed intakes were also observed. The Hu-HD diet allowed greater dry matter intake, longer rumination time, and higher ruminal pH, suggesting that the limiting factor for dry matter intake is neutral detergent fiber digestibility and its relative rumen retention time.     

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.