Effect of length of cut and kernel processing on use of corn silage by lactating dairy cows

Forty Holstein cows were used in an 8-wk randomized block design trial to determine the effects of theoretical length of cut (TLC) and kernel processing (KP) of whole plant corn silage on nutrient intake and digestibility, milk yield, and milk composition. Corn was harvested at three-quarters milk line stage of maturity at TLC of 1.90 or 2.54 cm. At each TLC, corn was KP at either 2 or 8 mm roll clearance. The control was harvested at 1.90 cm without KP. Corn silage provided 38% of the dietary dry matter (DM) in the experimental diets. Intake of DM and nutrients was similar among treatments. Apparent digestibility of DM and acid detergent fiber (ADF) increased with increasing TLC. Fiber digestibility was improved by KP compared with unprocessed corn silage. Starch digestibility was greater for corn silage KP at 2 vs. 8 mm. Apparent digestibility of DM, crude protein, and ADF was lowest for the diet containing silage harvested at 2.54 cm TLC and KP at 8 mm, resulting in an interaction of TLC and KP. No differences were observed in DM intake (DMI) among treatments. An interaction of TLC and KP was observed, however, for yield of milk protein and energy-corrected milk (ECM) and efficiency of converting DMI to ECM because of lower yield for diets containing silage harvested at 2.54 cm TLC and KP at 8 mm. Results of this trial indicate that as TLC increases, aggressive KP is necessary to maintain nutrient digestibility and performance of lactating dairy cows.     

Effect of replacing corn silage with annual ryegrass silage on nutrient digestibility,intake, and milk yield for lactating dairy cows

Twenty Holstein cows were used in an 8-wk randomized block design study to determine the effects of replacing corn silage with ryegrass silage on nutrient intake, apparent digestion, milk yield, and milk composition. The 8-wk trial consisted of a 2-wk preliminary period followed by a 6-wk collection period. Experimental diets were formulated to provide 55.5% of the total dry matter (DM) as forage. Ryegrass silage was substituted for 0, 35, 65, and 100% of DM provided by corn silage. Dietary concentrations of neutral detergent fiber (NDF) and acid detergent fiber (ADF) increased as ryegrass silage replaced corn silage. Intake of DM and crude protein (CP) was similar for all treatments, but intake of NDF and ADF increased linearly as ryegrass silage replaced corn silage. Apparent digestibility of DM declined linearly, whereas digestibility of CP increased linearly as ryegrass silage replaced corn silage. Apparent digestibility of NDF and ADF was highest for the diets in which ryegrass or corn silages provided all of the forage, resulting in a quadratic response. Dry matter intake was not different among treatments. Yield of milk, fat, and protein increased as ryegrass silage replaced corn silage. No differences were observed for body weight change, body condition score, and serum urea nitrogen concentration, but serum glucose concentration increased with increasing dietary proportion of ryegrass silage. These results indicate that substituting ryegrass silage for a portion or all of the corn silage in diets fed to lactating dairy cows can improve yield of milk and components.     

Effects of cutting height and maturity on the nutritive value of corn silage for lactating cows

We studied the effect of increasing the cutting height of whole-plant corn at the time of harvest from 12.7 (NC) to 45.7 (HC) cm on yield and nutritive value of silage for dairy cows. Three leafy corn silage hybrids were harvested at NC and HC at about 34% dry matter (E) and 41% DM (L) and ensiled in laboratory silos. Increasing the height of cutting lowered yields of harvested DM/ha. In addition, the concentrations of DM and starch were higher but the concentrations of lactic acid, crude protein, neutral detergent fiber (NDF), and acid detergent fiber were lower in HC than in NC. The concentration of acid detergent lignin was also lower in HC, but only in corn harvested at E. In vitro digestion (30 h) of NDF was greater in HC (50.7%) than NC (48.3%). Calculated yield of milk per tonne of forage DM was greater for HC than for NC at E but not at L. In a lactation experiment, increasing the height of cutting of another leafy corn silage hybrid, TMF29400, in general also resulted in similar changes in nutrient composition as just described. When fed to lactating dairy cows, HC corn silage resulted in tendencies for greater NDF digestion in the total tract, higher milk production and improved feed efficiency, but there were no differences in 3.5% fat corrected milk between treatments. Results of this study suggest that increasing the cutting height of whole plant corn at harvest can improve the nutritive value of corn silage for lactating dairy cows.     

Using brown midrib 6 dwarf forage sorghum silage and fall-grown oat silage in lactating dairy cow rations

Double cropping and increasing crop diversity could improve dairy farm economic and environmental sustainability. In this experiment, corn silage was partially replaced with 2 alternative forages, brown midrib-6 brachytic dwarf forage sorghum (Sorghum bicolor) or fall-grown oat (Avena sativa) silage, in the diet of lactating dairy cows. We investigated the effect on dry matter (DM) intake, milk yield (MY), milk components and fatty acid profile, apparent total-tract nutrient digestibility, N utilization, enteric methane emissions, and income over feed cost. We analyzed the in situ DM and neutral detergent fiber disappearance of the alternative forages versus corn silage and alfalfa haylage. Sorghum was grown in the summer and harvested in the milk stage. Oats were grown in the fall and harvested in the boot stage. Compared with corn silage, neutral detergent fiber and acid detergent fiber concentrations were higher in the alternative forages. Lignin content was highest for sorghum silage and similar for corn silage and oat silage. The alternative forages had less than 1% starch compared with the approximately 35% starch in the corn silage. Ruminal in situ DM effective degradability was similar, although statistically different, for corn silage and oat silage, but lower for sorghum silage. Diets with the alternative forages were fed in a replicated 3 × 3 Latin square design experiment with three 28-d periods and 12 Holstein cows. The control diet contained 44% (DM basis) corn silage. In the other 2 diets, sorghum or oat silages were included at 10% of dietary DM, replacing corn silage. Sorghum silage inclusion decreased DM intake, MY, and milk protein content but increased milk fat and maintained energy-corrected MY similar to the control. Oat silage had no effect on DM intake, MY, or milk components compared to the control. The oat silage diet increased apparent total-tract digestibility of dietary nutrients, except starch, whereas the sorghum diet slightly decreased DM, organic matter, crude protein, and starch digestibility. Cows consuming the oat silage diet had higher milk urea N and urinary urea N concentrations. Milk N efficiency was decreased by the sorghum diet. Diet did not affect enteric methane or carbon dioxide emissions. This study shows that oat silage can partially replace corn silage at 10% of the diet DM with no effect on MY. Brown midrib sorghum silage harvested at the milk stage with <1% starch may decrease DM intake and MY in dairy cows.     

Influence of mechanical processing on utilization of corn silage by lactating dairy cows

We conducted three experiments to determine the influence of mechanical processing on corn silage utilization by lactating dairy cows. Total mixed rations contained either unprocessed or processed corn silage harvested between 1/4 and 3/4 milk line. In trial 1, 12 multiparous Holstein cows were used in a replicated double switchback design with 21-d periods. Intake of dry matter (DM) was increased 1.2 kg/d by processing, but milk yield was unaffected. Processing did not affect apparent total-tract DM digestibility, but processing tended to lower starch and corn excretion in feces and reduced concentration of sieved corn kernel particles in feces. In trial 2, 42 Holstein cows were used in an 18-wk randomized complete-block design. Intake of DM and milk yield were unaffected by processing, but milk fat percent was increased 0.35 percentage units by processing. Processing tended to increase total-tract digestibility of starch, but reduced organic matter, crude protein, and neutral detergent fiber digestibilities. In trial 3, 30 Holstein cows were used in a 15-wk randomized complete block design. There was no influence of mechanical processing on intake or lactation performance in this trial. Despite indications of increased starch digestion in two trials and increased DM intake in one trial, effects of processing corn silage on lactation performance were minimal with corn silage at the maturity and moisture contents used in these trials.     

Effect of applying bacterial inoculants containing different types of bacteria to corn silage on the performance of dairy cattle

This study examined the effect of applying different bacterial inoculants to corn silage at the time of ensiling on the performance of lactating dairy cows. Corn plants were harvested at 35% dry matter (DM), chopped, and ensiled in 2.4-m-wide bags after application of (1) no inoculant (CON); (2) Biotal Plus II (B2) containing Pediococcus pentosaceus and Propionibacteria freudenreichii; (3) Buchneri 40788 (BUC) containing Lactobacillus buchneri; or (4) Buchneri 500 (B500) containing Pediococcus pentosaceus and L. buchneri. All inoculants were supplied by Lallemand Animal Nutrition (Milwaukee, WI). Each of the 4 silages was included in separate total mixed rations consisting of 44% corn silage, 50% concentrate, and 6% alfalfa hay (DM basis). Fifty-two lactating Holstein cows were stratified according to milk production and parity and randomly assigned at 22 d in milk to the 4 dietary treatments. Cows were fed for ad libitum consumption and milked twice daily for 49 d. Dietary treatment did not affect intakes (kg/d) of DM (20.0), crude protein (CP; 3.7), neutral detergent fiber (NDF; 5.7), or acid detergent fiber (ADF; 3.6), or digestibility (%) of DM (73.9) or CP (72.4). However, NDF digestibility was lower in cows fed B2 compared with those fed other diets (45.3 vs. 53.0%). Consequently, cows fed B2 had lower digestible NDF intake (kg/d) than those fed other diets (2.5 vs. 3.0 kg/d). Dietary treatment did not affect milk yield (32.3 kg/d), efficiency of milk production (1.61), concentrations of milk fat (3.18%) and protein (2.79%), or yields of milk fat (1.03 kg/d) and protein (1.26 kg/d). Inoculant application to corn silage did not affect milk yield or feed intake of cows.     

Performance of dairy cows fed annual ryegrass silage and corn silage with steam-flaked or ground corn

Twenty-four lactating Holstein cows were used in a 6-wk randomized block design trial with a 2 × 2 factorial arrangement of treatments to determine the effects of feeding ground corn (GC) or steam-flaked corn (SFC) in diets based on either annual ryegrass silage (RS) or a 50:50 blend of annual ryegrass and corn silages (BLEND). Experimental diets contained 49.6% forage and were fed as a total mixed ration once daily for 4 wk after a 2-wk preliminary period. No interactions were observed among treatments. Cows fed BLEND consumed more dry matter (DM), organic matter (OM), neutral detergent fiber (NDF), and acid detergent fiber (ADF) than those fed RS, but total-tract digestibility of OM, NDF, and ADF was greater for RS than for BLEND. No differences in nutrient intake were observed among treatments during wk 4 when nutrient digestibility was measured, but digestibility of DM and OM was greater for SFC than for GC. Cows fed BLEND tended to produce more energy-corrected milk than those fed RS, resulting in improved efficiency (kg of milk per kg of DM intake). When diets were supplemented with SFC, cows consumed less DM and produced more milk that tended to have lower milk fat percentage. Yield of milk protein and efficiency was greatest with SFC compared with GC. Blood glucose and milk urea nitrogen concentrations were similar among treatments, but blood urea nitrogen was greater for cows fed GC compared with those fed SFC. Results of this trial indicate that feeding a blend of annual ryegrass and corn silage is more desirable than feeding diets based on RS as the sole forage. Supplementing diets with SFC improved performance and efficiency compared with GC across forage sources.     

Effects of brown midrib 3 mutation in corn silage on dry matter intake and productivity of high yielding dairy cows

The effects of enhanced in vitro neutral detergent fiber (NDF) digestibility of corn silage on dry matter intake (DMI) and milk yield were evaluated using 32 Holstein cows in a crossover design with 28-d periods. At the beginning of the experiment, cows were 89 d in milk and yielded 45.6 kg/d of milk. Experimental diets contained either brown midrib (bm3) corn silage or isogenic normal corn silage (control) at 44.6% of DM. The NDF digestibility estimated by 30-h in vitro fermentation was higher for bm3 corn silage by 9.7 units. Contents of NDF and lignin were lower for bm3 corn silage by 1.8 and 0.8 units, respectively. Diets were formulated to contain 19% crude protein and 31% NDF and to have a forage to concentrate ratio of 56:44. Daily DMI, milk yield (3.5% fat-corrected milk), and solids-corrected milk were 2.1, 2.6, and 2.7 kg higher, respectively, for cows fed bm3 corn silage. The milk protein and lactose contents were greater for bm3 treatment, but milk fat content was not. Individual milk yield responses of the cows to bm3 treatment were positively related to pretrial milk yield, and DMI response tended to be positively related to pretrial milk yield. Enhanced in vitro NDF digestibility was associated with higher energy intake, which resulted in increased milk yield.     

Utilization of protein in red clover and alfalfa silages by lactating dairy cows and growing lambs

Feeding trials were conducted with lactating cows and growing lambs to quantify effects of replacing dietary alfalfa silage (AS) with red clover silage (RCS) on nutrient utilization. The lactation trial had a 2 × 4 arrangement of treatments: AS or RCS fed with no supplement, rumen-protected Met (RPM), rumen-protected Lys (RPL), or RPM plus RPL. Grass silage was fed at 13% of dry matter (DM) with AS to equalize dietary neutral detergent fiber (NDF) and crude protein contents. All diets contained (DM basis) 5% corn silage and 16% crude protein. Thirty-two multiparous (4 ruminally cannulated) plus 16 primiparous Holstein cows were blocked by parity and days in milk and fed diets as total mixed rations in an incomplete 8 × 8 Latin square trial with four 28-d periods. Production data (over the last 14 d of each period) and digestibility and excretion data (at the end of each period) were analyzed using the MIXED procedure of SAS (SAS Institute Inc., Cary, NC). Although DM intake was 1.2 kg/d greater on AS than RCS, milk yield and body weight gain were not different. However, yields of fat and energy-corrected milk as well as milk content of fat, true protein, and solids-not-fat were greater on AS. Relative to AS, feeding RCS increased milk and energy-corrected milk yield per unit of DM intake, milk lactose content, and apparent N efficiency and reduced milk urea. Relative to AS, apparent digestibility of DM, organic matter, NDF, and acid detergent fiber were greater on RCS, whereas apparent and estimated true N digestibility were lower. Urinary N excretion and ruminal concentrations of ammonia, total AA, and branched-chain volatile fatty acids were reduced on RCS, indicating reduced ruminal protein degradation. Supplementation of RPM increased intake, milk true protein, and solids-not-fat content and tended to increase milk fat content. There were no silage × RPM interactions, suggesting that RPM was equally limiting on both AS and RCS. Supplementation of RPL did not influence any production trait; however, a significant silage × RPL interaction was detected for intake: RPL reduced intake of AS diets but increased intake of RCS diets. Duplicated metabolism trials were conducted with lambs confined to metabolism crates and fed only silage. After adaptation, collections of silage refusals and excreta were made during ad libitum feeding followed by feeding DM restricted to 2% of body weight. Intake of DM was not different when silages were fed ad libitum. Apparent digestibility of DM, organic matter, NDF, and hemicellulose was greater in lambs fed RCS on both ad libitum and restricted intake; however, acid detergent fiber digestibility was only greater at restricted intake. Apparent and estimated true N digestibility was substantially lower, and N retention was reduced, on RCS. Results confirmed greater DM and fiber digestibility in ruminants and N efficiency in cows fed RCS. Specific loss of Lys bioavailability on RCS was not observed. Based on milk composition, Met was the first-limiting AA on both silages; however, Met was not limiting based on production and nutrient efficiency. Depressed true N digestibility suggested impaired intestinal digestibility of rumen-undegraded protein from RCS.     

Effects of brown midrib corn silage on the energy balance of dairy cattle

Effects of genotype and level of intake on net energy for lactation values of corn silage were evaluated by indirect calorimetry in two experiments using lactating and dry, nonpregnant dairy cows. In experiment 1, six multiparous Holstein cows in early lactation were fed experimental diets containing either brown midrib (bm3) or isogenic normal corn silage. Dietary treatments were isogenic and bm3 diets fed ad libitum, and the bm3 diets restricted-fed. Dry matter (DM) intake was 2.4 kg/d greater for cows fed the bm3 diet ad libitum compared with cows fed the isogenic diet. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows restricted-fed bm3 than the isogenic diet. In experiment 2, six dry, nonpregnant Holstein cows were fed maintenance diets containing either bm3 or isogenic corn silage. Apparent digestibilities of DM, organic matter, neutral detergent fiber, and acid detergent fiber were greater for cows fed bm3 compared with isogenic corn silage. Digestible energy and metabolizable energy were greater for maintenance diets containing bm3 compared with isogenic corn silage, respectively. These data indicate increased milk production seen in other studies is a result of increased DMI rather than an increase in energy efficiency. Increased organic matter digestibility of bm3 corn silage resulted in greater digestible energy and metabolizable energy values in cows fed at maintenance energy intake. However, calculated net energy for lactation values of bm3 and isogenic corn silages were similar at both productive and maintenance levels of feeding.     

Production of lactating dairy cows fed alfalfa or red clover silage at equal dry matter or crude protein contents in the diet

Two Latin square trials, using 21 or 24 multiparous lactating Holstein cows, compared the feeding value of red clover and alfalfa silages harvested over 2 yr. Red clover silages averaged 2 percentage units lower in crude protein (CP) and more than 2 percentage units lower in neutral detergent fiber and acid detergent fiber than did alfalfa silage. In trial 1, diets were formulated to 60% dry matter (DM) from alfalfa, red clover silage, or alfalfa plus red clover silage (grown together); CP was adjusted to about 16.5% by adding soybean meal, and the balance of dietary DM was from ground high moisture ear corn. Nonprotein N in red clover and alfalfa-red clover silages was 80% of that in alfalfa silage. Although DM intake was 2.5 and 1.3 kg/d lower on red clover and alfalfa plus red clover, yield of milk and milk components was not different among diets. In trial 2, four diets containing rolled high moisture shelled corn were formulated to 60% DM from alfalfa or red clover silage, or 48% DM from alfalfa or red clover silage plus 12% DM from corn silage. The first three diets contained 2.9% soybean meal, and the red clover-corn silage diet contained 5.6% soybean meal; the 60% alfalfa diet contained 18.4% CP, and the other three diets averaged 16.5% CP. Nonprotein N in red clover silage was 62% of that in alfalfa silage. Intake of DM was about 2 (no corn silage) and 1 kg/d (plus corn silage) lower on red clover. Yield of milk and milk components was not different among the first three diets; however, yields of milk, total protein, and true protein were higher on red clover-corn silage with added soybean meal. Replacing alfalfa with red clover improved feed and N efficiency and apparent digestibility of DM, organic matter, neutral detergent fiber, acid detergent fiber, and hemicellulose in both trials. Net energy of lactation computed from animal performance data was 18% greater in red clover than alfalfa. Data on milk and blood urea and N efficiency suggested better N utilization on red clover.     

The effect of silage cutting height on the nutritive value of a normal corn silage hybrid compared with brown midrib corn silage fed to lactating cows

A brown midrib (BMR) hybrid and a silage-specific non-BMR (7511FQ) hybrid were harvested at a normal cut height leaving 10 to 15 cm of stalk in the field. The non-BMR hybrid was also cut at a greater height leaving 45 to 50 cm of stalk. Cutting high increased the concentrations of dry matter (+4%), crude protein (+5%), net energy for lactation (+3%), and starch (+7%), but decreased the concentrations of acid detergent fiber (−9%), neutral detergent fiber (−8%), and acid detergent lignin (−13%) for 7511FQ. As expected, the BMR corn silage was 30% lower in lignin concentration than 7511FQ. After 30 h of in vitro ruminal fermentation, the digestibility of neutral detergent fiber for normal cut 7511FQ, the same hybrid cut high, and the normal cut BMR hybrid were 51.7, 51.4, and 63.5%, respectively. Twenty-seven multiparous lactating cows were fed a total mixed ration composed of the respective silages (45% of dry matter) with alfalfa haylage (5%), alfalfa hay (5%), and concentrate (45%) (to make the TMR isocaloric and isonitrogenous) in a study with a 3 × 3 Latin square design with 21-d periods. Milk production was greater for cows fed the BMR hybrid (48.8 kg/d) compared with those fed the normal cut 7511FQ (46.8 kg/d) or cut high (47.7 kg/d). Dry matter intake was not affected by treatment. Feed efficiency for cows fed the BMR silage (1.83) was greater than for those fed high-cut 7511FQ (1.75), but was not different from cows fed the normal cut 7511FQ (1.77). Cows fed the BMR silage had milk with greater concentrations of lactose but lower milk urea nitrogen than cows on other treatments. Harvesting a silage-specific, non-BMR corn hybrid at a high harvest height improved its nutritive content, but the improvement in feeding value was not equivalent to that found when cows were fed BMR corn silage.     

Effects of replacing grass silage with barley silage in dairy cow diets

This study examined the effects of gradually replacing grass silage with whole-crop barley silage on feed intake, ruminal and total tract digestibility, and milk yield in lactating dairy cows. Four dairy cows in early lactation, equipped with rumen cannulas, were fed 4 diets over four 21-d periods. The diets consisted of 4 forage mixtures of grass silage and whole-crop barley silage supplemented with 8.9 kg/d of concentrates [dry matter (DM) basis]. The proportion of barley silage in the forage was adjusted to 0, 0.20, 0.40, and 0.60 kg/kg of DM. Ruminal nutrient metabolism was measured on the basis of digesta flow entering the omasal canal. Ammonia concentrations and volatile fatty acid profiles were determined in the rumen fluid. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Replacement of grass silage with barley silage had no effect on DM, digestible organic matter, or neutral detergent fiber (NDF) intake, but starch intake increased, whereas nitrogen and digestible NDF (dNDF) intake decreased. Increases in the proportion of barley silage linearly decreased milk yield, and the molar proportion of acetate in the rumen, and increased that of propionate, butyrate, and valerate. Decreases in milk yield due to inclusion of barley silage were attributed to decreases in diet digestibility and nutrient supply to the animal. Barley silage linearly decreased organic matter digestibility in the total tract and NDF and dNDF digestibility in the rumen and the total tract, and decreased nonammonia N flow entering the omasal canal. No significant differences between diets were noted in the digestion rate of dNDF or passage rate of indigestible NDF from the rumen. Decreases in organic matter and NDF digestibility were attributed to the higher indigestible NDF concentration of barley silage compared with that of grass silage and to the smaller pool size of dNDF in the rumen.     

Effects of NutriDense and waxy corn hybrids on the rumen fermentation, digestibility and lactational performance of dairy cows

The objectives of this study were to determine the effects of NutriDense and waxy corn hybrids as silage and grain sources on milk yield, milk composition, digestibility of dietary components, and rumen characteristics. Six multiparous (intact) and six primiparous (ruminally cannulated) Holstein cows were assigned at 72 to 90 d of lactation to a 3 x 6 Latin rectangle design experiment to treatment of: 1) control diet, 2) NutriDense corn diet, and 3) waxy corn diet. Diets consisted of 10.9% alfalfa silage, 32.8% corn silage, 27.9% cracked corn grain, and 28.4% other ingredients (DM basis). Milk, FCM, and milk fat and protein yields were higher for cows fed the waxy diet than those fed the control diet. Milk protein percentage tended to be higher for cows fed the control and waxy diets than those fed the NutriDense diet. Dry matter intake tended to be higher for cows fed the waxy diet than the NutriDense diet. Apparent DM, OM, CP, ADF, NDF, and gross energy digestibilities were similar among dietary treatments, while apparent starch digestibility was higher for the waxy corn than for the NutriDense corn. Rumen NH3-N concentration was higher for cows fed the NutriDense diet than for those fed the control and waxy diets. The proportion of ruminal propionate was higher for the waxy diet than the control diet. NutriDense and waxy corn hybrids can be effective substitutes for conventional yellow dent corn hybrids in lactating dairy cow rations.     

Effect of replacing alfalfa silage with high moisture corn on nutrient utilization and milk production

Twenty-four multiparous lactating Holstein cows were blocked by days in milk and assigned to treatment sequences in a replicated 4x4 Latin square with 21-d periods. The four diets, formulated from alfalfa silage plus a concentrate mix based on ground high moisture ear corn, contained [dry matter (DM) basis]: 1) 20% concentrate, 80% alfalfa silage (24% nonfiber carbohydrates; NFC), 2) 35% concentrate, 65% alfalfa silage (30% NFC), 3) 50% concentrate, 50% alfalfa silage (37% NFC), or 4) 65% concentrate, 35% alfalfa silage (43% NFC). Soybean meal and urea were added to make diets isonitrogenous with equal nonprotein N (43% of total N). Intake of DM and milk yield indicated that adaptation was complete within 7 d of changing the diets within the Latin square. There were linear increases in apparent digestibility of DM and organic matter, and a linear decrease in neutral detergent fiber (NDF) digestibility with increasing dietary NFC. Solutions of significant quadratic equations yielded estimated maxima for intake of DM, organic matter, digestible organic matter, and NDF at, respectively, 37, 38, 43, and 27% dietary NFC. There were linear increases in yields of milk, protein, lactose, and solids not fat with increasing dietary NFC. Feed efficiency (milk/DM intake) yielded a quadratic response with a minimum at 27% dietary NFC. Maxima for milk fat content, fat yield, and fat-corrected milk yield were estimated to occur at, respectively, 30, 34 and 38% dietary NFC. In this short-term trial, maximal DM intake and fat-corrected milk yield indicated that the optimum concentrate for cows fed high moisture ear corn plus alfalfa silage as the only forage was equivalent to 37 to 38% dietary NFC; however, yields of milk, protein and solids not fat were still increasing at 65% dietary concentrate (43% NFC).     

Ryegrass or alfalfa silage as the dietary forage for lactating dairy cows

Renewed interest exists in using grass forages to dilute the higher crude protein (CP) and lower digestible fiber present in legumes fed to lactating dairy cows. A 3 x 3 Latin square feeding study with 4-wk periods was conducted with 24 Holstein cows to compare ryegrass silage, either untreated control or macerated (intensively conditioned) before ensiling, with alfalfa silage as the sole dietary forage. Ryegrass silages averaged [dry matter (DM) basis] 18.4% CP, 50% neutral detergent fiber (NDF), and 10% indigestible acid detergent fiber (ADF) (control) and 16.6% CP, 51% NDF, and 12% indigestible ADF (macerated). Alfalfa silage was higher in CP (21.6%) and lower in NDF (44%) but higher in indigestible ADF (26%). A lower proportion of the total N in macerated ryegrass silage was present as nonprotein N than in control ryegrass and alfalfa silages. Diets were formulated to contain 41% DM from either rye-grass silage, or 51% DM from alfalfa silage, plus high moisture corn, and protein concentrates. Diets averaged 17.5% CP and 28 to 29% NDF. The shortfall in CP on ryegrass was made up by feeding 7.6% more soybean meal. Intake and milk yields were similar on control and macerated ryegrass; however, DM intake was 8.3 kg/d greater on the alfalfa diet. Moreover, feeding the alfalfa diet increased BW gain (0.48 kg/d) and yield of milk (6.1 kg/d), FCM (6.8 kg/d), fat (0.26 kg/d), protein (0.25 kg/d), lactose (0.35 kg/d), and SNF (0.65 kg/d) versus the mean of the two ryegrass diets. Both DM efficiency (milk/DM intake) and N efficiency (milk-N/N-intake) were 27% greater, and apparent digestibility was 16% greater for DM and 53% greater for NDF and ADF, on the ryegrass diets. However, apparent digestibility of digestible ADF was greater on alfalfa (96%) than on ryegrass (average = 91%). Also, dietary energy content (estimated as net energy of lactation required for maintenance, milk yield, and weight gain) per unit of digested DM was similar for all three diets. Results of this trial indicated that, relative to ryegrass silage, feeding alfalfa silage stimulated much greater feed intake, which supported greater milk production.     

Improved milk production efficiency in early lactation dairy cattle with dietary addition of a developmental fibrolytic enzyme additive

A 3-part study was conducted to evaluate the effect of a developmental fibrolytic enzyme additive on the digestibility of selected forages and the production performance of early-lactation dairy cows. In part 1, 4 replicate 24-h batch culture in vitro incubations were conducted with alfalfa hay, alfalfa silage, and barley silage as substrates and ruminal fluid as the inoculum. A developmental fibrolytic enzyme additive (AB Vista, Marlborough, UK) was added at 5 doses: 0, 0.5, 1.0, 1.5, and 2.0 μL/g of forage dry matter (DM). After the 24-h incubation, DM, neutral detergent fiber (NDF), and acid detergent fiber (ADF) disappearance were determined. For alfalfa hay, DM, NDF, and ADF disappearance was greater at the highest dosage compared with no enzyme addition. Barley silage NDF and ADF and alfalfa silage NDF disappearance tended to be greater for the highest enzyme dosage compared with no enzyme addition. In part 2, 6 ruminally cannulated, lactating Holstein dairy cows were used to determine in situ degradation of alfalfa and barley silage, with (1.0 mL/kg of silage DM) and without added enzyme. Three cows received a control diet (no enzyme added) and the other 3 received an enzyme-supplemented (1.0 mL/kg of diet DM) diet. Enzyme addition after the 24 h in situ incubation did not affect the disappearance of barley silage or alfalfa silage. In part 3, 60 early-lactation Holstein dairy cows were fed 1 of 3 diets for a 10-wk period: (1) control (CTL; no enzyme), (2) low enzyme (CTL treated with 0.5 mL of enzyme/kg of diet DM), and (3) high enzyme (CTL treated with 1.0 mL of enzyme/kg of diet DM). Adding enzyme to the diet had no effect on milk yield, but dry matter intake was lower for the high enzyme treatment and tended to be lower for the low enzyme treatment compared with CTL. Consequently, milk production efficiency (kg of 3.5% fat-corrected milk/kg of DM intake) linearly increased with increasing enzyme addition. Cows fed the low and high enzyme diets were 5.3 (not statistically significant) and 11.3% more efficient, respectively, compared with CTL cows. This developmental fibrolytic enzyme additive has the potential to increase fiber digestibility of forages, which could lead to greater milk production efficiency for dairy cows in early lactation.     

Effect of feeding macerated alfalfa silage on nutrient digestibility and milk yield in lactating dairy cows

Five feeding studies were conducted with 141 lactating Holstein cows comparing macerated and control alfalfa silage harvested at two cuttings in each of 2 yr. Overall, silage made from macerated alfalfa contained more ash (suggesting improved soil contamination); greater fiber and lower nonprotein nitrogen (NPN) content suggested greater fermentation in the silo. In a digestion study, two diets were fed containing [dry matter (DM) basis] 72% of either control or macerated second-cutting alfalfa. Apparent digestibility of neutral detergent fiber and acid detergent fiber (ADF) was increased by maceration, and similar changes in digestibility were observed with Yb or indigestible ADF as marker; indigestible ADF was used as a marker in later studies. Lactation trials were conducted with first- and second-cutting alfalfa from each year. In each study, diets were formulated from alfalfa silage plus concentrate based on processed high moisture ear corn; mean compositions were (DM basis): negative control (61% control alfalfa silage), macerated (61% macerated alfalfa silage), and positive control (50% control alfalfa silage). All diets contained 2% crude protein from either roasted soybeans or low-solubles fish meal; soybean meal was added to make the positive control isonitrogenous (but not equal in ruminal undergraded protein). Milk yield was greater on macerated than negative control in two of four trials but not different in the other two trials. Yields of milk and milk components were not different between macerated and positive control in one of four trials. Versus the negative control, milk fat synthesis was depressed on macerated alfalfa in one trial. Overall performance on macerated versus negative control indicated greater apparent digestibility of organic matter (OM), greater yield of milk, protein, and solids not fat, but lower milk fat content. Yields of milk and milk components were greater overall on positive control versus macerated. Estimation of net energy for lactation (NEL) from maintenance, milk yield, and body weight gain indicated that control and macerated alfalfa silage contained, respectively, 1.36 and 1.42 Mcal of NEL of OM, an increase of about 5% due to maceration of alfalfa in these trials.     

Effects of feeding forage soybean silage on milk production, nutrient digestion, and ruminal fermentation of lactating dairy cows

The objective of this study was to determine the feeding value of forage soybean silage (SS) for dairy cows relative to a fourth-cut alfalfa silage (AS). Forage soybean was harvested at full pod stage. Two isonitrogenous diets were formulated with a 48:52 forage:concentrate ratio. Soybean silage and AS constituted 72% of the forage in each diet, with corn silage constituting the remaining 28%. Twenty Holsteins cows in early lactation were used in a switchback design. Four lactating Holsteins cows fitted with ruminal cannulas were used to determine the effects of dietary treatments on ruminal fermentation parameters and in vivo total tract nutrient utilization. Relative to AS, SS contained 15, 28, and 25% more neutral detergent fiber, acid detergent fiber, and crude protein, respectively. Dry matter intake (23.5 vs. 25.1 kg/d) and milk yield (35.5 vs. 37.2 kg/d) were lower for cows fed SS than for those fed AS. However, energy-corrected milk and milk efficiency were similar for both dietary treatments. Milk protein, lactose, and total solids concentrations were not influenced by dietary treatments (average 3.0, 4.7, and 12.6%, respectively). However, cows fed SS produced milk with greater milk fat (3.8 vs. 3.6%) and milk urea nitrogen concentrations (15.6 vs. 14.3 mg/dL) compared with cows fed AS. Ruminal pH was lower, whereas ruminal NH₃-N concentration was greater in cows fed SS than in cows fed AS. Total tract digestibilities of dry matter, crude protein, and neutral detergent fiber were not influenced by silage type. We concluded that forage SS, when compared with AS, had a negative impact on feed intake and milk yield, whereas energy-corrected milk, milk efficiency, and total tract nutrient digestion were similar.     

Performance of lactating dairy cows fed corn as whole plant silage and grain produced from a glyphosate-tolerant hybrid (event NK603)

Sixteen multiparous Holstein cows averaging 74 d in milk were used in a replicated 4 x 4 Latin square to compare the effects on animal performance of feeding whole plant silage and grain from a glyphosate-tolerant corn hybrid (event NK603), a nontransgenic control hybrid, and two commercial nontransgenic hybrids (DK647 and RX740). The grain and silage from the four corn hybrids were produced using the same procedures and under similar agronomic conditions at the University of Illinois. On a dry matter (DM) basis, diets contained 30% corn silage and 27.34% corn grain produced either from event NK603, a nontransgenic control, or commercial hybrids. Apart from the DM content of silages, the chemical composition of both grain and silage produced from the four corn hybrids were substantially equivalent. Feeding diets that contained event NK603 and DK647 hybrids tended to decrease DM intake (DMI) compared with the control nontransgenic and RX740. The intakes of crude protein (CP), acid and neutral detergent fiber, and nonfiber carbohydrates were not different for cows fed event NK603 and control diets. The RX740 diet resulted in the highest intakes of fiber and CP, whereas the DK647 diet resulted in the lowest intake of CP. These differences in nutrient intake arose from small variations in both the DMI and the chemical composition of feed ingredients and experimental diets. Production of milk and 3.5% fat-corrected milk; milk fat, CP, and true protein percentage and yield; milk urea N; milk total solids percentage and yield; and somatic cell count were not affected by treatments. These data indicate that the stable insertion of the gene that confers tolerance to glyphosate (event NK603) in the corn line used in this experiment does not affect its chemical composition and nutritional value for lactating dairy cows when compared with conventional corn.