Chemical and Physical Characteristics of Corn Silages and Their Effects on In Vitro Disappearance

Whole-plant flint corn silage inclusion in total mixed rations for pre- and postweaning dairy calves

Assuming that acetic acid plays a minor role in the development of ruminal epithelium of preweaning dairy calves, the fiber supply for growing calves has been neglected. More research has been done on including starch and nonfibrous carbohydrates in solid feed for preweaning calves. Accordingly, the fiber requirement of these calves is not well known, as diet recommendations vary greatly. Hence, elucidating the effects of including fiber from long particle sizes in the diet may be essential for helping calves overcome the transition challenge during weaning. Forty-five Holstein calves were used in a randomized block design, considering sex, birth date, and weight at 28 d of age, when the supply of the total mixed ration (TMR) with the inclusion of corn silage started. Three TMR with increasing whole-plant flint corn silage content (0, 10, or 20% on a dry matter basis) were compared: 0CS, 10CS, or 20CS, respectively. During the first 28 d of life, the calves were managed homogeneously and were fed 6 L/d of whole milk, a commercial calf starter pelleted, and water ad libitum. Next, the solid diet was changed to the respective solid feed treatment. Calves were gradually weaned from 52 to 56 d of age but were evaluated for an additional 14 d postweaning. Feed intake was measured daily, while body weight and metabolic indicators of intermediate metabolism were evaluated weekly. Ruminal fluid was collected at 6, 8, and 10 wk of age. Behavioral analysis was conducted on wk 7 (preweaning) and 10 (postweaning). There was a quadratic effect for dry matter intake from wk 7 to 10, with higher intake for the 10CS diet than the 0CS and 20CS diets. Consequently, the 10CS diet also promoted greater average daily gain at wk 8 and 9 compared with the 0CS and 20CS diets. However, the final body weight was not affected by the different solid diets. Silage inclusion in calves' diet positively affected time spent ruminating and chewing pre- and postweaning. Including 10% of whole-plant flint corn silage in the diets of young dairy calves is a strategy to increase total solid intake and decrease acidosis risk by increasing pH and ruminating activity around weaning.

Physical effectiveness of corn silage fractions stratified with the Penn State Particle Separator for lactating dairy cows

This study evaluated the physical effectiveness of whole-plant corn silage (CS) particles stratified with the Penn State Particle Separator, composed of 19- and 8-mm-diameter sieves and a pan, for lactating dairy cows. Eight Holstein cows (27.6 ± 2.8 kg/d of milk, 611 ± 74 kg body weight; 152 ± 83 d in milk) were assigned to two 4 × 4 Latin squares (22-d periods, 16-d adaptation), where one square was formed with rumen-cannulated cows. Three CS particle fractions were manually isolated using the 8- and 19-mm diameter sieves and re-ensiled in 200-L drums. The 4 experimental diets were (% dry matter): (1) CON (control): 17% forage neutral detergent fiber (NDF) from CS (basal roughage), 31.5% starch, and 31.9% NDF; (2) PSPan: 17% forage NDF from CS + 9% NDF from CS particles <8 mm, 25.9% starch, and 37.9% NDF; (3) PS8: 17% forage NDF from CS + 9% NDF from CS particles 8 to 19 mm, 25.5% starch, and 38.3% NDF; and (4) PS19: 17% forage NDF from CS + 9% NDF from CS particles >19 mm, 24.9% starch, and 38.8% NDF. Cows fed PS8 had greater dry matter intake and energy-corrected milk yield (22.4 and 26.9 kg/d, respectively) than cows fed CON (20.8 and 24.7 kg/d) and PS19 (21.2 and 24.8 kg/d), but no difference was detected between PSPan (21.6 and 25.8 kg/d) and other treatments. Milk fat concentration was greater for PS8 than CON, with intermediate values for PSPan and PS19. Milk fat yield was greater for cows fed PS8 than CON and PS19, and cows fed PSPan secreted more fat than CON cows but were not different from cows fed the other 2 diets. Cows fed CON had a lower meal frequency than cows fed PSPan, shorter meal and rumination times than PS8, and greater meal size and lower rates of rumination and chewing than the other 3 diets. Total chewing per unit of NDF was higher for PS8 than PSPan, although neither treatment differed from CON or PS19. Cows fed PS19 had higher refusal of feed particles >19 mm than cows fed CON and PSPan. The refusal of dietary NDF and undigested NDF in favor of starch were all greater for PS19 than on the other treatments. Cows fed PS19 had a greater proportion of the swallowed bolus and rumen digesta with particles >19 mm than the other 3 diets. Cows fed CON had the lowest ruminal pH and greatest lactate concentration relative to the other 3 diets. Plasma lipopolysaccharide was higher for cows fed CON and PSPan than for cows fed PS8 and PS19, and serum d-lactate tended to be lower on PSPan than for CON and PS8. In summary, the inclusion of CS fractions in a low-forage fiber diet (CON) reduced signs of ruminal acidosis. Compared with CS NDF <8 and >19 mm, CS NDF with 8- to 19-mm length promoted better rumen health and performance of dairy cows. These results highlight the importance of adjusting CS harvest and formulating dairy diets based on the proportion of particles retained between the 8- and 19-mm sieves.

Nutritional Composition and In Vitro Ruminal Digestibility of Crabgrass (Digitaria sanguinalis (L.) Scop.) in Monoculture or Interseeded with Cowpea (Vigna unguiculata (L.) Walp) and Lablab (Lablab purpureus (L.) Sweet)

The objective of this study was to evaluate the effects of interseeding crabgrass (CG) with two annual summer legumes on forage nutritional composition, dry matter (DM) yield, and in vitro fiber digestibility. The study was conducted as a randomized complete block design with four replicates per treatment. Plots were randomly assigned to one of six forage mix treatments. Crabgrass, cowpea (CWP), and lablab (LL) were planted in monoculture or in mixtures, resulting in six treatments. Throughout the growing season (three cuts), CG had the highest biomass yield, followed by the CG grown in mixtures with CWP and LL, whereas the two annual legume monocultures had the lowest yield. Cowpea and LL planted in monocultures had the highest concentration of CP and fiber digestibility, while the CG monoculture had the lowest. Furthermore, growing CG in a mixture with CWP and LL boosted the CP concentration and fiber digestibility to intermediate levels to those observed between both legume monocultures and CG. Regardless of treatment, the highest forage quality and yield was observed in the first harvest, with a drastic decline in the following harvests. In conclusion, the benefits of mixing crabgrass with legumes might be less than expected and should be carefully evaluated by livestock producers, especially when considering the effects of DM yield, forage quality, and pasture seeding costs.

Effects of ensiling time on corn silage starch ruminal degradability evaluated in situ or in vitro

Accurate measurements of concentration and ruminal degradability of corn silage starch is necessary for formulation of diets that meet the energy requirements of dairy cows. Five corn silage hybrids ensiled for 0 (unfermented), 30, 60, 120, and 150 d were used to determine the effects of ensiling time on starch degradability of corn silage. In addition, the effects of grind size of silage samples on 7-h in vitro starch degradability and the relationship between in vitro, in situ and near-infrared reflectance spectroscopy (NIRS) starch degradability were studied. In situ disappearance of corn silage starch increased from 0 to 150 d of ensiling, primarily as a result of an increase in the washout or rapidly degraded fraction of starch, particularly during the first 60 d of ensiling. When analyzed in vitro and by NIRS, ensiling time increased corn silage starch degradability either linearly or to a greater extent during the first 2 mo of ensiling. Differences in in situ starch disappearance among corn silage hybrids were apparent during the first 2 mo of ensiling but were attenuated as silages aged. No differences among hybrids were detected using a 7-h in vitro starch digestibility approach. Results from the in vitro subexperiment indicate that 7-h in vitro starch degradability was increased by reducing grind size of corn silage from 4 to 1 mm, regardless of ensiling duration. Fine grinding corn silages samples (i.e., 1-mm sieve) allowed distinguishing low- from medium- and high-starch degradability rated hybrids. Correlations among in situ, in vitro and NIRS measurements for starch degradability were medium to high (r ≥0.57); however, agreement among methods was low (concordance correlation coefficient ≤0.15). In conclusion, ensiling time linearly increased degradation rate of corn silage resulting in greater in situ starch disappearance after 150 d of ensiling. Reductions in grind size from 4 to 1 mm resulted in greater in vitro starch degradability, regardless of ensiling duration. Strong correlation but low agreement between starch degradability methods suggest that absolute estimations of corn silage starch degradability will vary, but all methods can be used to assess the effect of ensiling time on starch degradability.

The Effects of Irrigation, Genotype and Additives on Tef Silage Making

Tef is known as a multi-harvest crop with high production capacity and outstanding fodder quality. Hence, our overall goal is to develop tef as a new multi-harvest summer crop that can maintain high-quality feed and contribute to both field crops and the livestock industry in Israel. In this study, we aimed to evaluate the ability to preserve tef as silage. Four tef genotypes grown under well-watered (100%) and water-limited (75%) irrigation regimes were harvested at grain filling stage and ensiled with either no additives (control, CTL), or with heterofermentative inoculum (HI), molasses (MOL), and both MOL + HI. Our results showed for the first time that tef could be ensiled, although water-soluble carbohydrates (WSC) were lower than those in corn, "the perfect ensiling crop". Most of the tef silage qualitative parameters were better at water-limited irrigation. Additives HI or MOL or MOL + HI also improved silage parameters, e.g., lowered pH and ammonia nitrogen content, but increased in vitro dry matter digestibility, lactic acid and crude protein content, and lactic acid bacteria counts of tef silage. The current results imply increasing the diversity of local ruminant fodder crops, ensuring high-quality feed supply during the summer.

Yield, Nutritional Composition, and Digestibility of Conventional and Brown Midrib (BMR) Pearl Millet as Affected by Planting and Harvesting Dates and Interseeded Cowpea

The objective of this study was to evaluate the yield, nutritional composition, and digestibility of conventional (CON) and brown midrib (BMR) pearl millet (PM) with different establishment dates, maturity at harvest and when mixed with cowpea (CWP). In trial 1, CON and BMR were planted on two different dates. In trial 2, CON and BMR, mixed or not with CWP, were harvested when PM was at the boot or heading stages. In trial 1, dry matter (DM) yield was similar between both PM genotypes but delaying establishment reduced DM yield by 30%. Additionally, BMR had a lower concentration of acid detergent lignin (ADL) and a higher in vitro neutral detergent fiber digestibility (IVNDFD) compared to CON. In Trial 2, the DM yield was 7.3% higher for CON compared to BMR, and PM with the BMR trait had a lower level of ADL and higher IVNDFD compared to CON. Mixing PM with CWP had negligible effects on nutritional composition but reduced DM yield by 8.3%. Results of these studies indicated that fiber from BMR PM is more digestible than CON but, in one of the trials, this occurred at the expense of lower DM yield. Mixing CWP with PM negatively impacted DM yield.

The Evaluation of γ-Zein Reduction Using Mass Spectrometry—The Influence of Proteolysis Type in Relation to Starch Degradability in Silages

The starch availability and nutritional value of corn (Zea mays L.) are affected by zein proteins. The aim of the study was to see whether the proposed reduction of γ-zeins during the fermentation of silages is a result of either the enzymatic proteolytic activity or of the acidic environment, and how this reduction affects starch availability and degradability in high-moisture corn. A mass spectrometry (MS) technique was used to quantify the 16- and 27-kDa γ-zeins. Briefly, two-dimensional gel electrophoresis (2-DE) was used for γ-zein separation, followed by densitometry for protein quantification and matrix-assisted laser desorption ionization time-of-flight MS (MALDI-TOF/TOF) for protein identification. The results show that the reduction in γ-zeins induced by the ensiling led to a more pronounced starch availability and in vitro degradation, and this reduction was dependent on the type of proteolysis. More specifically, the results indicate that the reduction of γ-zeins in the ensiled corn was primarily driven by the enzymatic proteolysis. Furthermore, we demonstrated that 2-DE followed by densitometric quantification and the mass spectrometry analysis for protein identification can be used as a state-of-the-art method for γ-zein evaluation both in fresh and fermented/ensiled corn samples.

Symposium review: Fiber and in vitro methods, analytical variation, and contributions to feed analysis

At least 2 basic inputs are needed to formulate rations: the nutritional requirements of the animals to be fed and the nutritional composition of the feeds. David R. Mertens not only defined fiber requirements for dairy cattle but became a leading expert in the laboratory measurement of fiber in feeds, digesta, and feces. Fiber is a heterogeneous nutritional entity composed mainly of polysaccharides and polyphenolics. Because the method defines the fiber that is measured, methods must be described thoroughly and followed exactly to obtain results that are repeatable within a laboratory and reproducible among others. Filtration of neutral detergent fiber (NDF) can be difficult, and those who have worked in his laboratory can attest that Mertens rigorously studied this, along with other method details to improve NDF analysis from sample preparation to blank corrections. Mertens's procedure for amylase-treated NDF (aNDF), using α-amylase and sodium sulfite with crucibles, culminated in the Association of Official Analytical Chemists Official Method 2002.04 for aNDF, which was also accepted as International Standard ISO 16472:2006 and is used worldwide as a reference method for feed evaluation. Because aNDF digestibility is variable and a key factor in overall digestibility, Mertens also worked to improve in vitro ruminal digestibility and gas production procedures within and among laboratories, including procedures using flasks or filter bags. His in vitro gas production method is currently used by commercial laboratories that generate a significant share of the aNDF digestibility results reported worldwide. Outside of the laboratory, his extensive outreach to commercial and research laboratories has had a huge impact on fiber analysis, in vitro digestibility, and other laboratory procedures. While advising the National Forage Testing Association, Mertens provided program infrastructure that improved laboratory proficiency in more than 120 laboratories in the United States and around the world. Most importantly, thanks to his advances in fiber analysis and in vitro digestibility techniques, Mertens has enhanced the evaluation of feeds and the nutrition and health of dairy cows. These contributions have helped thousands of dairy farmers and nutritionists around the globe and continue to have a substantial impact on the industry.

Effect of kernel processing and particle size of whole-plant corn silage with vitreous endosperm on dairy cow performance

Kernel processing and theoretical length of cut (TLOC) of whole-plant corn silage (WPCS) can affect feed intake, digestibility, and performance of dairy cows. The objective of this study was to evaluate for lactating dairy cows the effects of kernel processing and TLOC of WPCS with vitreous endosperm. The treatments were a pull-type forage harvester without kernel processor set for a 6-mm TLOC (PT6) and a self-propelled forage harvester with kernel processor set for a 6-mm TLOC (SP6), 12-mm TLOC (SP12), and 18-mm TLOC (SP18). Processing scores of the WPCS were 32.1% (PT6), 53.9% (SP6), 49.0% (SP12), and 40.1% (SP18). Twenty-four Holstein cows (139 ± 63 d in milk) were blocked and assigned to six 4 × 4 Latin squares with 24-d periods (18 d of adaptation). Diets were formulated to contain 48.5% WPCS, 15.5% citrus pulp, 15.0% dry ground corn, 9.5% soybean meal, 6.8% low rumen degradability soybean meal, 1.8% calcium soap of palm fatty acids (FA), 1.7% mineral and vitamin mix, and 1% urea (dry matter basis). Nutrient composition of the diets (% of dry matter) was 16.5% crude protein, 28.9% neutral detergent fiber, and 25.4% starch. Three orthogonal contrasts were used to compare treatments: effect of kernel processing (PT6 vs. SP6) and effect of TLOC (particle size; SP6 vs. SP12 and SP12 vs. SP18). Cows fed SP6 produced 1.2 kg/d greater milk yield with no changes in dry matter intake, resulting in greater feed efficiency compared with PT6. Cows fed SP6 also produced more milk protein (+36 g/d), lactose (+61 g/d), and total solids (+94 g/d) than cows fed PT6. The mechanism for increased yield of milk and milk components involved greater kernel fragmentation, starch digestibility, and glucose availability for lactose synthesis by the mammary gland. However, cows fed SP6 had lower chewing time and tended to have greater levels of serum amyloid A compared with PT6. Milk yield was similar for SP6 and SP12, but SP12 cows tended to have less serum amyloid A with greater chewing time. Cows fed SP18 had lower total-tract starch digestibility and tended to have lower plasma glucose and produce less milk compared with cows fed SP12. Compared with PT6, feeding SP6 raised linear odd-chain FA concentration in milk. Similarly, a reduction of these same FA occurred for SP12 compared with SP6. Cows fed SP6 had greater proportion of milk C14:1 and C16:1 compared with PT6 and SP12. Lesser trans C18:1 followed by greater C18:0 concentrations were observed for SP12 and PT6 compared with SP6, which is an indication of more complete biohydrogenation in the rumen. Under the conditions of this study, the use of a self-propelled forage harvester with kernel processing set for a 12-mm TLOC is recommended for WPCS from hybrids with vitreous endosperm.

Adaptation strategies of forage soybeans cultivated on acidic soils under cool climate to produce high quality forage

Boreal soils tend to be podzols characterized by acidic pH, which can further limit forage crop growth and production. It is unclear, how forage soybeans adopt to produce forage with high nutritional quality when cultivated on podzols in boreal climate. To answer this question, we cultivated forage soybeans on agricultural podzols at 3 farm sites with varied soil pH (6.8, 6.0 or 5.1), and assessed the root membrane lipidome remodeling response to such climatic conditions. Contrary to our expectations, significantly lower biomass was observed at pH 6.8 compared to 6.0 and 5.1. However, surprisingly the plants produced similar forage quality at 6.8 and 5.1 pH. Three major lipid classes including phospholipids, glycolipids and phytosterols were observed in roots irrespective of soil pH. Phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidic acid (PA), and acylated glucosyl betasitosterol ester (AGlcSiE) accounted for 95% of the root lipidome, and expressed significant changes in response to cultivation across the three soil pH levels. These lipids were also observed to have strong correlations with forage production, and forage quality. Therefore, soybean genotypes with higher abilities to remodel PC, PE, PA, and AGlcSiE could be better suited for producing higher quality forage in acid podzolic soils characteristics of boreal ecosystems.

Response of common silage corn hybrids to inoculant application: fermentation profile, carbohydrate fractions, and digestibility during ensiling

Corn silage digestibility studies have focussed on genetically distant corn types. Conversely, silage additive studies monitored fermentation differences without discussing the subject of hybrid digestibility. How ensiling phases and additives affect silage quality in commercial corn hybrids has not been properly examined yet. As corn silage quality is a result of combined silage fermentation and digestibility characteristics, the aim of the study was to examine fermentation and digestibility responses to inoculant application in whole-plant corn silage of commercial hybrids intended for silage production in several time points during ensiling. Three corn hybrids grown under identical conditions in a split-plot field test were ensiled without inoculant application and with inoculant containing lactic acid bacteria and carbohydrate-degrading enzymes. Silages were sampled before ensiling, at the peak of the fermentation phase and during the stable phase. The fermentation profile, carbohydrate fraction, ruminal in vitro true dry matter digestibility, ruminal in vitro starch digestibility, and ruminal in vitro neutral detergent fibre digestibility were monitored. Although adding inoculant to silage improved its lactic acid production and decrease in pH, it did not affect its starch and fibre contents or their digestibility. Digestibility improved as ensiling continued, with the highest in vitro neutral detergent fibre digestibility and in vitro true dry matter digestibility values observed in the stable phase. Corn hybrids in this study differed in main fermentation characteristics, carbohydrate contents, and digestibility. These results suggest that even for commercial corn hybrids, the hybrid type is more important than inoculant for optimising silage characteristics and digestibility.

Nutritional composition and in vitro digestibility of grass and legume winter (cover) crops

In dairy farming systems, growing winter crops for forage is frequently limited to annual grasses grown in monoculture. The objectives of this study were to determine how cropping grasses alone or in mixtures with legumes affects the yield, nutritional composition, and in vitro digestibility of fresh and ensiled winter crops and the yield, nutritional composition, and in vitro digestibility of the subsequent summer crops. Experimental plots were planted with 15 different winter crops at 3 locations in Virginia. At each site, 4 plots of each treatment were planted in a randomized complete block design. The 15 treatments included 5 winter annual grasses [barley (BA), ryegrass (RG), rye (RY), triticale (TR), and wheat (WT)] in monoculture [i.e., no legumes (NO)] or with 1 of 2 winter annual legumes [crimson clover (CC) and hairy vetch (HV)]. After harvesting the winter crops, corn and forage sorghum were planted within the same plots perpendicular to the winter crop plantings. The nutritional composition and the in vitro digestibility of winter and summer crops were determined for fresh and ensiled samples. Growing grasses in mixtures with CC increased forage dry matter (DM) yield (2.84 Mg/ha), but the yield of mixtures with HV (2.47 Mg/ha) was similar to that of grasses grown in monoculture (2.40 Mg/ha). Growing grasses in mixtures with legumes increased the crude protein concentration of the fresh forage from 13.0% to 15.5% for CC and to 17.3% for HV. For neutral detergent fiber (NDF) concentrations, the interaction between grasses and legumes was significant for both fresh and ensiled forages. Growing BA, RY, and TR in mixtures with legumes decreased NDF concentrations, whereas growing RG and WT with legumes did not affect the NDF concentrations of either the fresh or the ensiled forages. Growing grasses in mixtures with legumes decreased the concentration of sugars of fresh forages relative to grasses grown in monoculture. Primarily, this decrease can be attributed to low concentrations of sugars of mixtures with HV (10.5%). Growing grasses in mixtures with legumes reduced the fiber digestibility of both winter crops (75.7% to 72.8% NDF). Growing grasses in mixtures with legumes did not affect estimated DM yield, nutritional composition, or digestibility of the succeeding summer crops. In conclusion, growing grasses in mixtures with legumes as winter forage crops can increase forage estimated DM yields and its nutritional quality in dairy farming sytems.

Effect of ensiling time and exogenous protease addition to whole-plant corn silage of various hybrids, maturities, and chop lengths on nitrogen fractions and ruminal in vitro starch digestibility

The objective of this study was to evaluate the effects of ensiling time and exogenous protease addition on soluble CP (% of CP), ammonia-N (% of N), and ruminal in vitro starch digestibility (ivSD) of whole-plant corn silage (WPCS) from 3 hybrids, 2 maturities, and 2 chop lengths. Samples from 3 nonisogenic hybrids [brown midrib containing the bm3 gene mutation (BM3), dual-purpose (DP), or floury-leafy (LFY)] at 2 harvest maturities [2/3 kernel milk line (early) or 7d later (late)] with 2 theoretical lengths of cut settings (0.64 or 1.95cm) on a forage harvester were collected at harvest, treated with or without exogenous protease, and ensiled in triplicate in vacuum heat-sealed plastic bags for 0, 30, 60, 120, and 240d. Thus, the experiment consisted of 120 treatments (3 hybrids × 2 maturities × 2 chop lengths × 2 protease treatments × 5 time points) and 360 mini-silos (3 replications per treatment). Vitreousness, measured by dissection on unfermented kernels on the day of harvest, averaged 66.8, 65.0, and 59.0% for BM3, DP, and LFY, respectively. A protease × maturity interaction was observed with protease increasing ivSD in late but not early maturity. Ensiling time × hybrid interactions were observed for ammonia-N and soluble CP concentrations with greater values for FLY than other hybrids only after 120d of ensiling. Ensiling time × hybrid or protease × hybrid interactions were not observed for ivSD. Measurements of ivSD were greatest for FLY and lowest for BM3. Length of the ensiling period did not attenuate negative effects of kernel vitreousness or maturity on ivSD in WPCS. Results suggest that the dosage of exogenous protease addition used in the present study may reduce but not overcome the negative effects of maturity on ivSD in WPCS. No interactions between chop length and ensiling time or exogenous protease addition were observed for ivSD.

Influence of corn silage hybrid type on lactation performance by Holstein dairy cows

The primary objective of this study was to determine lactation performance by dairy cows fed nutridense (ND), dual-purpose (DP), or brown midrib (BM) corn silage hybrids at the same concentration in the diets. A secondary objective was to determine lactation performance by dairy cows fed NutriDense corn silage at a higher concentration in the diet. One hundred twenty-eight Holstein and Holstein × Jersey cows (105 ± 38 d in milk) were stratified by breed and parity and randomly assigned to 16 pens of 8 cows each. Pens were then randomly assigned to 1 of 4 treatments. Three treatment total mixed rations (TMR; DP40, BM40, and ND40) contained 40% of dry matter (DM) from the respective corn silage hybrid and 20% of DM from alfalfa silage. The fourth treatment TMR had ND corn silage as the sole forage at 65% of DM (ND65). A 2-wk covariate adjustment period preceded the treatment period, with all pens receiving a TMR with equal proportions of DP40, BM40, and ND40. Following the covariate period, cows were fed their assigned treatment diets for 11 wk. nutridense corn silage had greater starch and lower neutral detergent fiber (NDF) content than DP or BM, resulting in ND40 having greater energy content (73.2% of total digestible nutrients, TDN) than DP40 or BM40 (71.9 and 71.4% TDN, respectively). Cows fed BM40 had greater milk yield than DP40, whereas ND40 tended to have greater milk yield and had greater protein and lactose yields compared with DP40. No differences in intake, component-corrected milk yields, or feed efficiency were detected between DP40, BM40, and ND40. Milk yield differences may be due to increased starch intake for ND40 and increased digestible NDF intake for BM40 compared with DP40. Intake and milk yield and composition were similar for ND40 compared with BM40, possibly due to counteracting effects of higher starch intake for ND40 and higher digestible NDF intake for BM40. Feeding ND65 reduced intake, and thus milk and component yields, compared with ND40 due to either increased ruminal starch digestibility or increased rumen fill for ND65. Nutridense corn silage was a viable alternative to both DP and BM at 40% of diet DM; however, lactation performance was reduced when nutridense corn silage was fed at 65% of DM.

Efficacy of liquid feeds varying in concentration and composition of fat, nonprotein nitrogen, and nonfiber carbohydrates for lactating dairy cows

In trial 1, we evaluated the efficacy of a liquid feed (LF) containing cane molasses and corn steep liquor as carriers of suspended white grease (WG) without or with urea (U) or with soybean lipid (SL; a byproduct of soybean processing) compared with roasted soybeans plus tallow blended into respective concentrates in a 16-wk lactation study. The dry matter intake (DMI) and milk production for LF diets were either similar to or greater than respective controls, although SL decreased milk fat percentage. In trial 2, we compared LF without fat to LF plus WG or SL and also evaluated the dose response to increasing amount of LF + WG in a 16-wk lactation trial in which the LF products were added to respective total mixed rations. The DMI was increased and then decreased (quadratic response) with increasing LF + WG without a linear response. However, production of milk, protein, and fat increased linearly with corresponding quadratic responses, which we interpret to be a result of a limiting returns response from DMI and density of net energy for lactation. When LF plus SL was fed, milk fat percentage and yield decreased compared with the comparable amount of LF + WG. In a 12-wk lactation study (trial 3), we added 3.25 or 6.5% of the dry matter as LF (a different but generally similar product than the previous trials and without fat) to diets formulated to maintain comparable ruminal nonstructural carbohydrate digestibility by adding soybean hulls to decrease nonfiber carbohydrates (NFC) concentration; the 6.5% LF diet was without or with Rumensin (11.5 g/909 kg of dry matter). When 3.25% LF was added but NFC was decreased from 40 to 37%, cows increased DMI and production of milk fat. Adding Rumensin decreased DMI but maintained milk fat yield compared with its 6.25% LF control without Rumensin. In trials 1 and 3, apparent total tract nutrient digestibility was not affected by treatment. In conclusion, feeding LF at about 5% (trial 2, which contained WG, 1.6% added sugar) or 3.25% (trial 3, 1.7% added sugar) generally increased DMI and maintained or increased production of milk, protein, and fat.