Corn silage management: effects of hybrid,maturity, inoculation,and mechanical processing on fermentation characteristics

Two experiments were conducted to evaluate the effects of hybrid, maturity, mechanical processing, and inoculation of corn silage on fermentation characteristics. In experiment 1, Pioneer hybrid 3845 corn silage was harvested at three maturities (hard dough, one-third milkline, two-thirds milkline). In experiment 2, Pioneer hybrids 3845 and Quanta were harvested at three maturities (one-third milkline, two-thirds milkline, and blackline). In both experiments, corn silage was harvested at each maturity with and without mechanical processing and with and without inoculation. In experiments 1 and 2, corn silage was harvested at a theoretical length-of-cut of 6.4 and 12.7 mm, respectively. Maturity at harvest tended to have a greater impact on silage fermentation characteristics of corn silage than mechanical processing and inoculation. In experiments 1 and 2, corn silage harvested at the earliest maturity tended to have decreased dry matter content and increased water-soluble carbohydrate concentrations during the ensiling process than corn silage harvested at advanced maturities. In experiment 2, pH levels were lower for corn silage harvested at the early maturity (one-third milkline) compared with advanced maturities (two-thirds milkline and blackline) by 57 d after ensiling. The difference in pH can be explained by the greater concentration of water-soluble carbohydrates at the early maturity (one-third ML) soon after ensiling (2, 3, 6 and 10 d after ensiling) compared with advanced maturities (two-thirds ML and BL). The increased water-soluble carbohydrate concentrations in the less mature corn silage provided nutrients for bacteria to grow and produce primarily lactic acid (6, 10, and 57 d after ensiling) and some acetic acid (2, 3, 6, and 10 d after ensiling) which reduced the pH of corn silage more than at the advanced maturities. There was a slight change in silage fermentation characteristics when corn silage was inoculated with Pioneer 1132 inoculant in experiment 1. The inoculated corn silage had increased temperature, lactate and acetate concentrations, and lower water-soluble carbohydrate and pH levels compared with uninoculated corn silage. Dry matter recovery tended to be greater for processed corn silage in experiment 1, and greater for unprocessed corn silage in experiment 2. It appears that when fermentation was greater (increased temperature and lactate concentration 57 d after ensiling) the dry matter recovery was lower.     

Corn silage management I: effects of hybrid,maturity, and mechanical processing on chemical and physical characteristics

Two experiments were conducted to evaluate the effects of hybrid, maturity, and mechanical processing of whole plant corn on chemical and physical characteristics, particle size, pack density, and dry matter recovery. In the first experiment, hybrid 3845 whole plant corn was harvested at hard dough, one-third milkline, and two-thirds milkline with a theoretical length-of-cut of 6.4 mm. In the second experiment, hybrids 3845 and Quanta were harvested at one-third milkline, two-thirds milkline, and blackline stages of maturity with a theoretical length-of-cut of 12.7 mm. At each stage of maturity, corn was harvested with and without mechanical processing by using a John Deere 5830 harvester with an onboard kernel processor. The percentage of intact corn kernels present in unprocessed corn silage explained 62% of variation in total tract starch digestibility. As the amount of intact kernels increased, total tract starch digestibility decreased. Post-ensiled vitreousness of corn kernels within the corn silage explained 31 and 48% of the variation of total tract starch digestibility for processed and unprocessed treatments, respectively. For a given amount of vitreous starch in corn kernels, total tract starch digestibility was lower for cows fed unprocessed corn silage compared with processed corn silage. This suggests that processing corn silage disrupts the dense protein matrix within the corn kernel where starch is embedded, therefore making the starch more available for digestion. Particle size of corn silage and orts that contained corn silage was reduced when it was processed. Wet pack density was greater for processed compared with unprocessed corn silage.     

Corn silage management II: effects of hybrid,maturity, and mechanical processing on digestion and energy content

Two experiments were conducted to evaluate the effects of maturity and mechanical processing of two hybrids of whole plant corn on starch, fiber, and ether extract digestibilities and energy content of the total mixed ration fed to lactating Holstein cows. In the first experiment, Pioneer hybrid 3845 whole plant corn was harvested at hard dough, one-third milkline, and two-thirds milkline with a theoretical length of cut of 6.4 mm. At each stage of maturity, corn was harvested with and without mechanical processing. In the second experiment, Pioneer hybrids 3845 and Quanta were harvested at one-third milkline, two-thirds milkline, and blackline stages of maturity with and without mechanical processing. The theoretical length of cut was 12.7 mm. The measured TDN and NEL concentrations were lower for diets containing processed corn silage in experiment 1 and greater for diets containing processed corn silage in experiment 2, compared with diets containing unprocessed corn silage. The lower energy content for diets containing processed corn silage in experiment 1 can be explained by the lower total tract NDF, ether extract, and CP digestibilities. The greater energy content for diets containing processed corn silage in experiment 2 can be attributed to greater total tract starch and NDF digestibilities for cows fed processed corn silage diets. In experiment 2, diets containing processed corn silage (1.59 Mcal/kg) had approximately 2.6% more energy available per kilogram of DM consumed compared with diets containing unprocessed corn silage (1.55 Mcal/kg). For hybrid Quanta in experiment 2, the TDN and NEL concentrations of diets containing corn silage harvested at two-thirds ML were greater than at other maturities.     

Corn silage management: effects of hybrid, maturity, chop length, and mechanical processing on rate and extent of digestion

Five experiments were conducted to evaluate the effects of hybrid, chop length, maturity, and mechanical processing of corn silage on dry matter and nutrient disappearance in the rumen. Corn silage that had not been dried or ground was incubated in macro in situ bags (30 x 35 cm) for 8, 16, 24,48, and 96 h. Experiments la and 2 evaluated the effects of maturity and mechanical processing for two corn silage hybrids harvested at two theoretical lengths-of-cut. Experiments 3 through 5 evaluated the effects of chop length and mechanical processing for two corn silage hybrids harvested at two-thirds milkline. The hybrid with low neutral fiber (NDF) concentrations had greater dry matter and starch disappearance than the hybrid with high NDF concentrations. The effect of chop length on nutrient disappearance was variable across experiments 3 through 5. Processing improved dry matter disappearance in experiments la, 2 (two-thirds milkline and blackline), 3, 4, and 5 at the majority of ruminal incubation timepoints. Starch disappearance was greater for unprocessed corn silage in experiment la (hard dough and two-thirds milkline) and was greater for processed corn silage in experiments 2 and 5. However, there was no consistent trend in starch disappearance between processed and unprocessed corn silage in experiments 3 and 4. This can be partially explained by the high disappearance of starch (experiment 3, > or = 98% and experiment 4, > or = 94%) by 24 h of ruminal incubation. Minimal differences were detected in NDF disappearance between processed and unprocessed corn silage across maturities. In experiments 2 and 5, crude protein disappearance was improved due to processing at some incubation timepoints. Rate of dry matter, starch (one-third milkline and two-thirds milkline), and NDF disappearance tended to increase when corn silage was mechanically processed in experiment 2. Dry matter, starch, and crude protein disappearance tended to be greater for corn silage harvested at the early maturity (one-third milkline) in experiment 2 compared with advanced maturities (two-thirds milkline and blackline). Disappearance of NDF was greater at early maturities compared with advanced maturities in experiments 1a and 2. Rate of dry matter (hybrid 3845), starch, and NDF (hybrid 3845) disappearance tended to decrease as maturity advanced from one-third milkline to blackline in experiment 2. These results suggest that the macro in situ method can be used to evaluate nutrient disappearance in the rumen.     

Corn silage management: effects of hybrid,chop length,and mechanical processing on digestion and energy content

Two experiments were conducted to evaluate the effects of chop length and mechanical processing of two hybrids of whole plant corn on digestion and energy content of the total mixed ration (TMR). The experimental designs in experiments 1 and 2 were 6 x 6 and 4 x 4 Latin squares, respectively. In the first experiment, Pioneer hybrid 3845 was harvested at three theoretical lengths of cut: 11.1, 27.8, and 39.7 mm. At each chop length, corn was harvested with and without mechanical processing using a John Deere 5830 harvester with an onboard kernel processor. In the second experiment, Pioneer hybrid Quanta was harvested at two theoretical lengths of cut: 27.8 and 39.7 mm, with and without mechanical processing. In both experiments, the increase in the theoretical length of cut of corn silage increased the average length of cut and tended to increase the percentage of particles greater than 19 mm and lower the percentage of particles between 8 and 19 mm. In experiment 1, apparent total tract dry matter, organic matter, and neutral detergent fiber (NDF) digestibilities were lower for cows fed diets containing corn silage harvested at a short chop length (11.1 mm) than for corn silage harvested at a long chop length (39.7 mm). The lower total tract digestibility of nutrients may have contributed to the lower TDN, metabolizable energy (percentage of digestible energy), and NEL concentration of diets containing the short chop length corn silage (experiment 1). In experiment 2, total tract starch digestibility was greater for cows fed medium chop (27.8 mm) corn silage diets, and total tract NDF digestibility was greater for cows fed long chop (39.7 mm) corn silage diets. The opposing effect of total tract starch and fiber digestibilities between chop lengths may have contributed to the lack of difference in energy content of the diets in experiment 2. The TDN and NEL concentrations of the processed corn silage diets were greater than the unprocessed corn silage diets in experiment 1. The increase in energy concentration for the processed corn silage diet was due to greater total tract digestibility of organic matter and ether extract. Total tract starch digestibility was greater, and total tract NDF digestibility was lower for cows fed processed corn silage diets than unprocessed corn silage diets in experiment 2. The opposing effect of total tract starch and fiber digestibilities between processed and unprocessed corn silage may have contributed to the lack of difference in energy content of the diets.     

Corn silage management: effects of maturity, inoculation, and mechanical processing on pack density and aerobic stability

Three experiments were conducted to evaluate the effects of inoculation, maturity, and mechanical processing of corn silage on aerobic stability and pack density. Corn silage was stored in 20-L mini silos for the three aerobic stability experiments. Corn silage was stored in 80-L mini silos for the three pack-density experiments. The wet pack density of corn silage tended to decrease as maturity advanced in all of the pack-density experiments, and processed corn silage had a greater wet pack density compared with unprocessed corn silage in two of the three 20-L mini silo experiments. Aerobic stability, measured as the number of hours to reach 1.7 degrees C above ambient, was greater for processed corn silage in two of the three 20-L mini silo experiments, and was greater for inoculated corn silage across the three 20-L mini silo experiments. Inoculation of corn silage with lactic acid producing bacteria tended to improve aerobic stability of corn silage more than maturity and mechanical processing.     

Effect of corn silage hybrid and metabolizable protein supply on nitrogen metabolism of lactating dairy cows

This experiment was conducted to determine the effects of corn silage hybrid and supply of metabolizable protein (MP) on manure excretion and N metabolism by lactating dairy cows. Eight Holstein cows in midlactation (replicated 4 × 4 Latin square with 21-d periods) were fed 1 of 4 treatments, arranged factorially. Diets contained 55% corn silage made from a dual-purpose hybrid or a brown midrib (BMR) hybrid, and 45% concentrate that contained either a low or high concentration of rumen undegradable protein (altered by the addition of fish meal and treated soybean meal). Crude protein averaged 14.0 and 17.5% and supply of MP averaged 2,360 and 2,990 g/d for the low and high MP treatments (not affected by hybrid). Increasing supply of MP greatly increased urine output and tended to increase total manure output, whereas diets with BMR silage tended to reduce manure output. Increased MP supply increased daily excretion of manure N by 25% (465 vs. 374 g/d), fecal N by 27 g, and urinary N by 64 g. When the effect of N intake was removed, cows fed BMR silage excreted about 15 g/d less N via manure than cows fed the other silage. Rumen ammonia, volatile fatty acid concentrations, and pH were not affected by treatment. Dry matter intake (overall mean = 24.9 kg/d) tended to be increased with increased MP but was not affected by hybrid. Milk production for cows fed BMR was higher than for cows fed the dual-purpose hybrid (36.9 vs. 35.3 kg/d), but because of changes in fat concentration, yield of energy-corrected milk was not affected by treatment. The only interaction observed was increased yield of milk protein when BMR silage was combined with increased supply of MP.     

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.     

Methane production,ruminal fermentation characteristics,nutrient digestibility,nitrogen excretion,and milk production of dairy cows fed conventional or brown midrib corn silage

The objective of this study was to examine the effect of replacing conventional corn silage (CCS) with brown midrib corn silage (BMCS) in dairy cow diets on enteric CH₄ emission, nutrient intake, digestibility, ruminal fermentation characteristics, milk production, and N excretion. Sixteen rumen-cannulated lactating cows used in a crossover design (35-d periods) were fed (ad libitum) a total mixed ration (forage:concentrate ratio = 65:35, dry matter basis) based (59% dry matter) on either CCS or BMCS. Dry matter intake and milk yield increased when cows were fed BMCS instead of CCS. Of the milk components, only milk fat content slightly decreased when cows were fed the BMCS-based diet compared with when fed the CCS-based diet (3.81 vs. 3.92%). Compared with CCS, feeding BMCS to cows increased yields of milk protein and milk fat. Ruminal pH, protozoa numbers, total VFA concentration, and molar proportions of acetate and propionate were similar between cows fed BMCS and those fed CCS. Daily enteric CH₄ emission (g/d) was unaffected by dietary treatments, but CH₄ production expressed as a proportion of gross energy intake or on milk yield basis was lower for cows fed the BMCS-based diet than for cows fed the CCS-based diet. A decline in manure N excretion and a shift in N excretion from urine to feces were observed when BMCS replaced CCS in the diet, suggesting reduced potential of manure N volatilization. Results from this study show that improving fiber quality of corn silage in dairy cow diets through using brown midrib trait cultivar can reduce enteric CH₄ emissions as well as potential emissions of NH₃ and N₂O from manure. However, CH₄ emissions during manure storage may increase due to excretion of degradable OM when BMCS diet is fed, which merits further investigation.     

Replacing corn silage with different forage millet silage cultivars: Effects on milk yield,nutrient digestion,and ruminal fermentation of lactating dairy cows

This study investigated the effects of dietary replacement of corn silage (CS) with 2 cultivars of forage millet silages [i.e., regular millet (RM) and sweet millet (SM)] on milk production, apparent total-tract digestibility, and ruminal fermentation characteristics of dairy cows. Fifteen lactating Holstein cows were used in a replicated 3 × 3 Latin square experiment and fed (ad libitum) a high-forage total mixed ration (68:32 forage:concentrate ratio). Dietary treatments included CS (control), RM, and SM diets. Experimental silages constituted 37% of each diet DM. Three ruminally fistulated cows were used to determine the effect of dietary treatments on ruminal fermentation and total-tract nutrient utilization. Relative to CS, RM and SM silages contained 36% more crude protein, 66% more neutral detergent fiber (NDF), and 88% more acid detergent fiber. Cows fed CS consumed more dry matter (DM; 24.4 vs. 22.7 kg/d) and starch (5.7 vs. 3.7 kg/d), but less NDF (7.9 vs. 8.7 kg/d) than cows fed RM or SM. However, DM, starch and NDF intakes were not different between forage millet silage types. Feeding RM relative to CS reduced milk yield (32.7 vs. 35.2 kg/d), energy-corrected milk (35.8 vs. 38.0 kg/d) and SCM (32.7 vs. 35.3 kg/d). However, cows fed SM had similar milk, energy-corrected milk, and solids-corrected milk yields than cows fed CS or RM. Milk efficiency was not affected by dietary treatments. Milk protein concentration was greatest for cows fed CS, intermediate for cows fed SM, and lowest for cows fed RM. Milk concentration of solids-not-fat was lesser, whereas milk urea nitrogen was greater for cows fed RM than for those fed CS. However, millet silage type had no effect on milk solids-not-fat and milk urea nitrogen levels. Concentrations of milk fat, lactose and total solids were not affected by silage type. Ruminal pH and ruminal NH₃-N were greater for cows fed RM and SM than for cows fed CS. Total-tract digestibility of DM (average = 67.9%), NDF (average = 53.9%), crude protein (average = 63.3%), and gross energy (average = 67.9%) were not influenced by dietary treatments. It was concluded that cows fed CS performed better than those fed RM or SM likely due to the higher starch and lower NDF intakes. However, no major differences were noted between the 2 forage millet silage cultivars.     

A comparison of processed conventional corn silage to unprocessed and processed brown midrib corn silage on intake, digestion, and milk production by dairy cows

We studied the effects of mechanical processing and type of hybrid on the nutritive value of corn silage for lactating cows. Treatments were brown midrib (BMR) corn silage that was unprocessed (U-BMR), BMR corn silage that was processed (P-BMR), and a conventional corn silage that was processed (P-7511). All silages were harvested at a theoretical chop length of 19 mm. The chemical compositions of the silages were similar among treatments except that BMR silages were lower in lignin and higher in protein than P-7511. Brown midrib silages had greater 30-h in situ and in vitro NDF digestion than did P-7511, and processing had no effect on 30-h in situ and in vitro fiber digestion, but it increased in situ starch digestion after 3 and 12 h of incubation. Both processed silages had a smaller proportion of particles >1.91 cm and fewer whole corn kernels compared with unprocessed silage. Lactating cows were fed a total mixed ration (TMR) consisting of 42% of each silage type, 40% concentrate, 10% alfalfa silage, and 8% alfalfa hay (DM basis). Cows fed TMR containing P-BMR ate more DM and produced more milk than cows fed P-7511. At feeding, the TMR containing U-BMR had a larger proportion of particles >1.91 cm when compared with the TMR of cows fed processed silages, and after 24 h the difference was even greater, indicating that cows fed unprocessed corn silage sorted more. Cows fed TMR with P-7511 and P-BMR had greater total tract digestibility of organic matter, crude protein, and starch compared with cows fed U-BMR. In vivo digestibility of neutral detergent fiber was greatest for cows fed P-BMR when compared with the other treatments.     

Effects of essential oils on digestion, ruminal fermentation, rumen microbial populations, milk production, and milk composition in dairy cows fed alfalfa silage or corn silage

Four Holstein cows fitted with ruminal cannulas were used in a 4 × 4 Latin square design (28-d periods) with a 2 × 2 factorial arrangement of treatments to investigate the effects of addition of a specific mixture of essential oil compounds (MEO; 0 vs. 750 mg/d) and silage source [alfalfa silage (AS) vs. corn silage (CS)] on digestion, ruminal fermentation, rumen microbial populations, milk production, and milk composition. Total mixed rations containing either AS or CS as the sole forage source were balanced to be isocaloric and isonitrogenous. In general, no interactions between MEO addition and silage source were observed. Except for ruminal pH and milk lactose content, which were increased by MEO supplementation, no changes attributable to the administration of MEO were observed for feed intake, nutrient digestibility, end-products of ruminal fermentation, microbial counts, and milk performance. Dry matter intake and milk production were not affected by replacing AS with CS in the diet. However, cows fed CS-based diets produced milk with lower fat and higher protein and urea N concentrations than cows fed AS-based diets. Replacing AS with CS increased the concentration of NH₃-N and reduced the acetate-to-propionate ratio in ruminal fluid. Total viable bacteria, cellulolytic bacteria, and protozoa were not influenced by MEO supplementation, but the total viable bacteria count was higher with CS- than with AS-based diets. The apparent digestibility of crude protein did not differ between the AS and CS treatments, but digestibilities of neutral detergent fiber and acid detergent fiber were lower when cows were fed CS-based diets than when they were fed AS-based diets. Duodenal bacterial N flow, estimated using urinary purine derivatives and the amount of N retained, increased in cows fed CS-based diets compared with those fed AS-based diets. Feeding cows AS increased the milk fat contents of cis-9, trans-11 18:2 (conjugated linoleic acid) and 18:3 (n-3 fatty acid) compared with feeding cows CS. Results from this study showed limited effects of MEO supplementation on nutrient utilization, ruminal fermentation, and milk performance when cows were fed diets containing either AS or CS as the sole forage source.     

Corn silage in dairy cow diets to reduce ruminal methanogenesis: Effects on the rumen metabolically active microbial communities

Methane produced by the methanogenic Archaea that inhabit the rumen is a potent greenhouse gas and represents an energy loss for the animal. Although several strategies have been proposed to mitigate enteric CH₄ production, little is known about the effects of dietary changes on the microbial consortia involved in ruminal methanogenesis. Thus, the current study aimed to examine how the metabolically active microbes are affected when dairy cows were fed diets with increasing proportions of corn silage (CS). For this purpose, 9 ruminally cannulated lactating dairy cows were used in a replicated 3 × 3 Latin square design and fed a total mixed ration (60:40 forage:concentrate ratio on a dry matter basis) with the forage portion being either alfalfa silage (0% CS), corn silage (100% CS), or a 50:50 mixture (50% CS). Enteric CH₄ production was determined using respiration chambers and total rumen content was sampled for the determination of fermentation characteristics and molecular biology analyses (cDNA-based length heterogeneity PCR, quantitative PCR). The cDNA-based length heterogeneity PCR targeting active microbes revealed similar bacterial communities in cows fed 0% CS and 50% CS diets, whereas important differences were observed between 0% CS and 100% CS diets, including a reduction in the bacterial richness and diversity in cows fed 100% CS diet. As revealed by quantitative PCR, feeding the 100% CS diet increased the number of total bacteria, Prevotella spp., Archaea, and methanogenic activity, though it reduced protozoal number. Meanwhile, increasing the CS proportion in the diet increased propionate concentration but decreased ruminal pH, CH₄ production (L/kg of dry matter intake), and concentrations of acetate and butyrate. Based on these microbial and fermentation changes, and because CH₄ production was reduced by feeding 100% CS diet, this study shows that the use of cDNA-based quantitative PCR to estimate archaeal growth and activity is not reliable enough to reflect changes in ruminal methanogenesis. A more robust technique to characterize changes in archaeal community structures will help to better understand the microbial process involved in ruminal methanogenesis and, hence, enabling the development of more effective dietary CH₄ mitigation strategies.     

Evaluation of nitrogen utilization and the effects of monensin in dairy cows fed brown midrib corn silage

Twenty midlactation Holstein cows (4 ruminally fistulated) averaging 101 ± 34 d in milk and weighing 674 ± 77 kg were used to compare rations with brown midrib corn silage (bm3) to rations with dual-purpose control silage (DP) on N utilization and milk production. The effect of monensin in these rations was also examined. Animals were assigned to one of five 4 × 4 Latin squares with treatments arranged in a 2 × 2 factorial. Cows were fed 1 of 4 treatments during each of the four 28-d periods. Treatments were 1) 0 mg/d monensin and bm3 corn silage, 2) 0 mg/d monensin and DP corn silage, 3) 300 mg/d monensin and bm3 corn silage, and 4) 300 mg/d monensin and DP corn silage. In vitro 30-h neutral detergent fiber (NDF) digestibility was greater for bm3 corn silage (61.0 vs. 49.1 ± 0.62). Dry matter intake (DMI) tended to be greater for cows consuming bm3 corn silage (21.3 vs. 20.2 kg/d). Neither hybrid nor monensin affected milk production, fat, or protein (37.7 kg, 3.60%, or 3.04%). Monensin tended to increase rumen pH (5.89 vs. 5.79 ± 0.07) compared with the control treatment. In addition, bm3 corn silage resulted in a significant decrease in rumen pH (5.72 vs. 5.98 ± 0.07). Supplementing monensin had no effect on molar proportions of acetate, propionate, or butyrate. In contrast, an increase was observed in branched-chain volatile fatty acids. No treatment interactions were observed for rumen pH or molar proportion of propionate but monensin decreased the molar proportion of acetate and increased the molar proportion of butyrate when cattle consumed bm3 silage. Dry matter, N, and acid detergent fiber digestibility were lower for the bm3 ration, whereas NDF digestibility was not different between treatments. There was no effect of hybrid on microbial protein synthesis (1,140 g/d) as estimated by urinary concentration of purine derivatives. Cows consuming bm3 excreted more fecal N than cows consuming DP (38.2 vs. 34.4% N intake); however, based on spot sampling, estimated urinary and manure N were not different between treatments (35.8 and 71.9% N intake). Monensin had no effect on DMI, digestibility of any nutrients, or N metabolism, and there were no hybrid by monensin interactions. Rations including bm3 corn silage tended to increase DMI but did not affect production. The reduction in the digestibility of some nutrients when cows consumed bm3 may have been caused by increased DMI and possible increased digestion in the lower gut. This increase in DMI appeared to also have negatively affected N digestibility but not NDF digestibility. This resulted in a greater amount of N excreted in feces but did not affect total mass of manure N.     

Corn silage hybrid type and quality of alfalfa hay affect dietary nitrogen utilization by early lactating dairy cows

This experiment was conducted to determine the effects of corn silage (CS) hybrids and quality of alfalfa hay (AH) in high-forage dairy diets on N utilization, ruminal fermentation, and lactational performance by early-lactating dairy cows. Eight multiparous Holstein cows were used in a duplicated 4 × 4 Latin square experiment with a 2 × 2 factorial arrangement of dietary treatments. The 8 cows (average days in milk = 23 ± 11.2) were surgically fitted with ruminal cannula, and the 2 squares were conducted simultaneously. Within square, cows were randomly assigned to a sequence of 4 diets: conventional CS (CCS) or brown midrib CS (BMR) was combined with fair-quality AH [FAH: 46.7% neutral detergent fiber (NDF) and 18.4% crude protein (CP)] or high-quality AH (HAH: 39.2% NDF and 20.7% CP) to form 4 treatments: CCS with FAH, CCS with HAH, BMR with FAH, and BMR with HAH. Diets were isonitrogenous across treatments, averaging 15.9% CP. Each period lasted a total of 21 d, with 14 d for treatment adaptation and 7 d for data collection and sampling. Intake of DM and milk yield did not differ in response to CS hybrids or AH quality. Although feeding BMR-based diets decreased urinary N output by 24%, it did not affect fecal N output. Feeding HAH decreased urinary N output by 15% but increased fecal N output by 20%. Nitrogen efficiency [milk N (g/d)/intake N (g/d)] tended to increase for BMR treatments. Ruminal ammonia-N concentration was lower for cows fed BMR-based diets than for those fed CCS-based diets but was not affected by quality of AH. Feeding BMR-based diets or HAH decreased milk urea N concentration by 23 or 15%, respectively, compared with CCS-based diets or FAH. Total volatile fatty acid concentration increased with HAH but was not influenced by CS hybrids. Feeding BMR-based diets decreased urinary N-to-fecal N ratio (UN:FN), and it was further reduced by feeding HAH. Although cows fed the BMR-based diets tended to increase milk N-to-manure N ratio, the quality of AH did not affect the ratio. The lower ratio of UN:FN with a higher ratio of milk N-to-manure N ratio for the BMR-based diets indicates that feeding BMR may reduce manure ammonia-N by reducing excretion of urinary N and increasing secretion of milk N per unit of manure N excreted.     

Methane production,digestion, ruminal fermentation,nitrogen balance,and milk production of cows fed corn silage- or barley silage-based diets

This study evaluated the effects of replacing barley silage (BS) with corn silage (CS) in dairy cow diets on enteric CH₄ emissions, ruminal fermentation characteristics, digestion, milk production, and N balance. Nine ruminally cannulated lactating cows were used in a replicated 3 × 3 Latin square design (32-d period) and fed (ad libitum) a total mixed ration (TMR; forage:concentrate ratio 60:40; dry matter basis) with the forage portion consisting of either barley silage (0% CS; 0% CS and 54.4% BS in the TMR), a 50:50 mixture of both silages (27% CS; 27.2% CS and 27.2% BS in the TMR), or corn silage (54% CS; 0% BS and 54.4% CS in the TMR). Increasing the CS proportion (i.e., at the expense of BS) also involved increasing the proportion of corn grain (at the expense of barley grain). Intake and digestibility of dry matter and milk production increased linearly as the proportion of CS increased in the diet. Increasing dietary CS proportion decreased linearly the acetate molar proportion and increased linearly that of propionate. Daily CH₄ emissions tended to respond quadratically to increasing proportions of CS in the diet (487, 540, and 523 g/d for 0, 27, and 54% CS, respectively). Methane production adjusted for dry matter or gross energy intake declined as the amount of CS increased in the diet; this effect was more pronounced when cows were fed the 54% CS diet than the 27% CS diet. Increasing the CS proportion in the diet improved N utilization, as reflected by decreases in ruminal ammonia concentration and urinary N excretion and higher use of dietary N for milk protein secretion. Total replacement of BS with CS in dairy cow diets offers a strategy to decrease CH₄ energy losses and control N losses without negatively affecting milk performance.     

Corn silage versus corn silage:alfalfa hay mixtures for dairy cows: effects of dietary potassium, calcium, and cation-anion difference

Corn silage (CS) has replaced alfalfa hay (AH) and haylage as the major forage fed to lactating dairy cows, yet many dairy producers believe that inclusion of small amounts of alfalfa hay or haylage improves feed intake and milk production. Alfalfa contains greater concentrations of K and Ca than corn silage and has an inherently higher dietary cation-anion difference (DCAD). Supplemental dietary buffers such as NaHCO₃ and K₂CO₃ increase DCAD and summaries of studies with these buffers showed improved performance in CS-based diets but not in AH-based diets. We speculated that improvements in performance with AH addition to CS-based diets could be due to differences in mineral and DCAD concentrations between the 2 forages. The objective of this experiment was to test the effects of forage (CS vs. AH) and mineral supplementation on production responses using 45 lactating Holstein cows during the first 20 wk postpartum. Dietary treatments included (1) 50:50 mixture of AH and CS as the forage (AHCS); (2) CS as the sole forage; and (3) CS fortified with mineral supplements (CaCO₃ and K₂CO₃) to match the Ca and K content of the AHCS diet (CS-DCAD). Feed intake and milk production were equivalent or greater for cows fed the CS and CS-DCAD diets compared with those fed the AHCS diet. Fat percentage was greater in cows fed the CS compared with the AHCS diet. Fat-corrected milk (FCM; 3.5%) tended to be greater in cows fed the CS and CS-DCAD diets compared with the AHCS diet. Feed efficiencies measured as FCM/dry matter intake were 1.76, 1.80, and 1.94 for the AHCS, CS, and CS-DCAD diets, respectively. The combined effects of reduced feed intake and increased FCM contributed to increased feed efficiency with the CS-DCAD diet, which contained 1.41% K compared with 1.18% K in the CS diet, and we speculate that this might be the result of added dietary K and DCAD effects on digestive efficiency. These results indicate no advantage to including AH in CS-based diets, but suggest that improving mineral supplementation in CS-based diets may increase feed efficiency.     

Meta-analysis of effects of inoculation with Lactobacillus buchneri,with or without other bacteria,on silage fermentation,aerobic stability,and performance of dairy cows

A meta-analysis of 158 peer-reviewed articles was conducted to examine effects of inoculation with Lactobacillus buchneri (LB)-based inoculants (LBB) that did or did not include homolactic or obligate heterolactic bacteria on silage fermentation and aerobic stability. A complementary meta-analysis of 12 articles examined LBB inoculation effects on dairy cow performance. Raw mean differences between inoculant and control treatment means weighted by inverse variance were compared with a hierarchical effects model that included robust variance estimation. Meta-regression and subgrouping analysis were used to identify effects of covariates including forage type, application rate (≤10⁴, 10⁵, 10⁶, or ≥ 10⁷ cfu/g as fed), bacteria type (LB vs. LB plus other bacteria), enzyme inclusion, ensiling duration, and silo type (laboratory or farm scale). Inoculation with LBB increased acetate (62%), 1, 2 propanediol (364%) and propionate (30%) concentration and aerobic stability (73.8%) and reduced lactate concentration (7.2%), yeast counts (7-fold) and mold counts (3-fold). Feeding inoculated silage did not affect milk yield, dry matter intake, and feed efficiency in lactating dairy cows. However, forage type, inoculant composition, and dose effects on silage quality measures were evident. Inoculation with LBB increased aerobic stability of all silages except tropical grasses. Adding obligate homolactic or facultative heterolactic bacteria to LB prevented the small increase in DM losses caused by LB alone. The 10⁵ and 10⁶ cfu/g rates were most effective at minimizing DM losses while aerobic stability was only increased with 10⁵, 10⁶, and ≥ 10⁷ cfu/g rates. Inoculation with LBB increased acetate concentration, reduced yeast counts and improved aerobic stability but did not improve dairy cow performance.     

Processing and chop length effects in brown-midrib corn silage on intake, digestion, and milk production by dairy cows

In this experiment, we evaluated the influence of increasing chop length and mechanical processing of whole-plant brown-midrib corn silage on intake, digestion, and milk production by dairy cows. Corn silage treatments were harvested at three-quarter milk line stage of maturity at 13- and 19-mm theoretical chop length without processing, or at 19- and 32-mm theoretical chop length with processing at a 2-mm roll clearance. Twenty-four multiparous Holstein cows that averaged 102 +/- 17 d in milk at trial initiation were randomly assigned to treatments in a replicated 4 x 4 Latin square design with 28-d periods. Preplanned orthogonal contrasts were used to evaluate effects of processing (19 processed vs. 19 mm unprocessed) and chop length (13 vs. 19 mm unprocessed and 19 vs. 32 mm processed). Treatments were fed in total mixed rations containing 60% forage (67% corn silage and 33% alfalfa silage) and 40% shelled corn and soybean meal-based concentrate (dry matter basis). Milk yield was unaffected by treatment. Dry matter intake was unaffected by corn silage processing, but increasing corn silage chop length reduced dry matter intake in unprocessed (26.6 vs. 25.5 kg/d) and processed (25.9 vs. 25.1 kg/d) chop length contrasts. Processing reduced milk fat content (3.36 vs. 3.11%) and yield (1.43 vs. 1.35 kg/d), increased total-tract starch digestion (92.9 vs. 97.4%), and decreased total-tract neutral detergent fiber digestion (51.0 vs. 41.8%). Total chewing time (min/d) was unaffected by treatment. Masticate mean particle length was unaffected by chop length in unprocessed and processed corn silage treatments. In this study with brown-midrib corn silage fed to dairy cows producing 43 kg/d of milk, there were no benefits from crop processing or increasing chop length on lactation performance.     

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.