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.     

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.     

Methane emissions of stored manure from dairy cows fed conventional or brown midrib corn silage

The objective of this study was to examine the effects of feeding conventional corn silage (CCS) or brown midrib corn silage (BMCS) to dairy cows on CH₄ emissions from stored manure. Eight lactating cows were fed (ad libitum) a total mixed ration (forage:concentrate ratio 65:35; dry matter basis) containing 59% (dry matter basis) of either CCS or BMCS. Feces and urine were collected from each cow and mixed with residual sludge obtained from a manure storage structure. Manure was incubated for 17 wk at 20°C under anaerobic conditions (O₂-free N₂) in 500-mL glass bottles. Methane emissions and changes in chemical composition of the manure were monitored during the incubation period. The total amount of feces and urine excreted was higher for cows fed BMCS than for cows fed CCS [8.6 vs. 6.5 kg/d of volatile solids (VS)]. Manure from cows fed BMCS emitted more CH₄ than manure from cows fed CCS (173 vs. 146 L/kg of VS) throughout the incubation period. Similarly, VS and neutral detergent fiber losses throughout incubation were higher for manure from cows fed BMCS versus cows fed CCS (37.6 vs. 30.6% and 46.2 vs. 31.2%, respectively). Manure NH₃ concentration (79% of total manure N) was not affected by corn silage cultivar. Results of this study show that using a more digestible corn silage cultivar (BMCS vs. CCS) may increase the contribution of manure to CH₄ emissions, and may offset gain achieved by reducing enteric CH₄ emissions.     

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.     

Effects of corn silage hybrid and dietary concentration of forage NDF on digestibility and performance by dairy cows

Eight intact multiparous cows and four ruminally and duodenally cannulated primiparous cows were fed four diets in a replicated 4 x 4 Latin square design: 1) 17% forage neutral detergent fiber (NDF) with brown midrib corn silage (BMRCS), 2) 21% forage NDF with BMRCS, 3) 17% forage NDF with conventional corn silage (CCS), and 4) 21% forage NDF with CCS. Diets contained 17.4% crude protein and 38.5% NDF. Each period consisted of 4 wk for intact cows and 2 wk for cannulated cows. For intact cows, DM intake was higher for BMRCS than CCS, and milk urea N was higher for 21 than 17% forage NDF. Milk protein yield tended to be higher and milk urea N lower for cows fed BMRCS than those fed CCS. Milk yield and milk protein percentage were similar among treatments. For the cannulated cows, ruminal mat consistency was similar among treatments. Based on a 72 h in situ incubation, BMRCS was lower in indigestible NDF than CCS. The BMRCS resulted in a higher proportion of ruminal propionate than CCS. Cows fed 21% forage NDF had a higher proportion of acetate and a lower proportion of propionate than cows fed 17% forage NDF. The total tract digestibility of nutrients and efficiency of bacterial N synthesis were similar among treatments, except that BMRCS resulted in lower intestinal fatty acid digestibility than CCS, and 17% forage NDF tended to result in higher total tract fatty acid digestibility than 21% forage NDF. Ruminal NDF digestibility was similar among dietary treatments. The increased milk production observed from feeding BMRCS in some studies may be explained by higher DM intake rather than increased total tract digestibility of the diets.     

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 corn silage hybrids and dietary nonforage fiber sources on feed intake, digestibility, ruminal fermentation, and productive performance of lactating Holstein dairy cows

This experiment was conducted to determine the effects of corn silage hybrids and nonforage fiber sources (NFFS) in high forage diets formulated with high dietary proportions of alfalfa hay (AH) and corn silage (CS) on ruminal fermentation and productive performance by early lactating dairy cows. Eight multiparous Holstein cows (4 ruminally fistulated) averaging 36 ± 6.2 d in milk were used in a duplicated 4 × 4 Latin square design experiment with a 2 × 2 factorial arrangement of treatments. Cows were fed 1 of 4 dietary treatments during each of the four 21-d replicates. Treatments were (1) conventional CS (CCS)-based diet without NFFS, (2) CCS-based diet with NFFS, (3) brown midrib CS (BMRCS)-based diet without NFFS, and (4) BMRCS-based diet with NFFS. Diets were isonitrogenous and isocaloric. Sources of NFFS consisted of ground soyhulls and pelleted beet pulp to replace a portion of AH and CS in the diets. In vitro 30-h neutral detergent fiber (NDF) degradability was greater for BMRCS than for CCS (42.3 vs. 31.2%). Neither CS hybrids nor NFFS affected intake of dry matter (DM) and nutrients. Digestibility of N, NDF, and acid detergent fiber tended to be greater for cows consuming CCS-based diets. Milk yield was not influenced by CS hybrids and NFFS. However, a tendency for an interaction between CS hybrids and NFFS occurred, with increased milk yield due to feeding NFFS with the BMRCS-based diet. Yields of milk fat and 3.5% fat-corrected milk decreased when feeding the BMRCS-based diet, and a tendency existed for an interaction between CS hybrids and NFFS because milk fat concentration further decreased by feeding NFFS with BMRCS-based diet. Although feed efficiency (milk/DM intake) was not affected by CS hybrids and NFFS, an interaction was found between CS hybrids and NFFS because feed efficiency increased when NFFS was fed only with BMRCS-based diet. Total volatile fatty acid production and individual molar proportions were not affected by diets. Dietary treatments did not influence ruminal pH profiles, except that duration (h/d) of pH <5.8 decreased when NFFS was fed in a CCS-based diet but not in a BMRCS-based diet, causing a tendency for an interaction between CS hybrids and NFFS. Overall measurements in our study reveal that high forage NDF concentration (20% DM on average) may eliminate potentially positive effects of BMRCS. In the high forage diets, NFFS exerted limited effects on productive performance when they replaced AH and CS. Although the high quality AH provided adequate NDF (38.3% DM) for optimal rumen fermentative function, the low NDF concentration of the AH and the overall forage particle size reduced physically effective fiber and milk fat concentration.     

Influence of a novel bm3 corn silage hybrid with floury kernel genetics on lactational performance and feed efficiency of Holstein cows

Dry matter intake, lactation performance, and chewing behavior of multiparous Holstein cows (n = 15) fed diets containing a novel bm3 corn silage hybrid with floury kernel genetics were compared with cows fed diets containing commercially available conventional and bm3 hybrids using a replicated 3 × 3 Latin square design with 28-d periods. Cows were housed in tiestalls, milked 3 times/d, and fed a total mixed ration containing 49.0% (dry matter basis) of (1) a conventional corn silage hybrid (CONV); (2) a brown midrib bm3 hybrid (BMR); or (3) a bm3 hybrid with floury kernel genetics (BMRFL). All diets contained 6.3% hay crop silage and 44.7% concentrate. Dietary nutrient composition averaged 32.7% neutral detergent fiber (NDF) and 26.3 starch (% of dry matter). Data were analyzed by ANOVA using the MIXED procedure in SAS (SAS Institute Inc., Cary, NC). The dry matter intake was greater for cows fed BMR (28.0 kg/d) compared with CONV (26.8 kg/d), whereas dry matter intake for cows fed BMRFL was intermediate (27.6 kg/d). Energy-corrected milk (ECM) yield was greater for cows fed BMR (50.3 kg/d) and BMRFL (51.8 kg/d) compared with CONV (47.2 kg/d). Milk fat yield was higher for cows fed BMRFL (1.87 kg/d) compared with CONV (1.74 kg/d) and BMR (1.80 kg/d). Milk protein yield was greater for cows fed BMR (1.49 kg/d) and BMRFL (1.54 kg/d) compared with CONV (1.36 kg/d). Milk urea-N was reduced for cows fed BMR (11.61 mg/dL) and BMRFL (11.16 mg/dL) compared with CONV (13.60 mg/dL). Feed efficiency (ECM/dry matter intake) was higher for cows fed BMRFL (1.87) compared with CONV (1.76) and BMR (1.79). Milk N efficiency was greatest for cows fed BMRFL (40.4%) followed by BMR (38.1%) and finally CONV (35.3%). Cows fed CONV chewed 5 min more per kilograms of NDF consumed than cows fed either of the BMR hybrids. No differences were observed among diets in apparent total-tract digestibility of NDF (58.1%) or starch (99.3%). Overall lactational performance was enhanced for cows fed diets containing both BMR and BMRFL hybrids versus CONV. In addition, feeding the BMRFL corn silage improved efficiency of component-corrected milk production and milk N efficiency compared with the CONV and BMR silages.     

Influence of fiber degradability of corn silage in diets with lower and higher fiber content on lactational performance,nutrient digestibility,and ruminal characteristics in lactating Holstein cows

The effect of neutral detergent fiber (NDF) degradability of corn silage in diets containing lower and higher NDF concentrations on lactational performance, nutrient digestibility, and ruminal characteristics in lactating Holstein cows was measured. Eight ruminally cannulated Holstein cows averaging 91 ± 4 (standard error) days in milk were used in a replicated 4 × 4 Latin square design with 21-d periods (7-d collection periods). Dietary treatments were formulated to contain either conventional (CON; 48.6% 24-h NDF degradability; NDFD) or brown midrib-3 (BM3; 61.1% 24-h NDFD) corn silage and either lower NDF (LNDF) or higher NDF (HNDF) concentration (32.0 and 35.8% of ration dry matter, DM) by adjusting the dietary forage content (52 and 67% forage, DM basis). The dietary treatments were (1) CON-LNDF, (2) CON-HNDF, (3) BM3-LNDF, and (4) BM3-HNDF. Data were analyzed as a factorial arrangement of diets within a replicated Latin square design with the MIXED procedure of SAS (SAS Institute Inc., Cary, NC) with fixed effects of NDFD, NDF, NDFD × NDF, period(square), and square. Cow within square was the random effect. Time and its interactions with NDFD and NDF were included in the model when appropriate. An interaction between NDFD and NDF content resulted in the HNDF diet decreasing dry matter intake (DMI) with CON corn silage but not with BM3 silage. Cows fed the BM3 corn silage had higher DMI than cows fed the CON corn silage, whereas cows fed the HNDF diet consumed less DM than cows fed the LNDF diet. Cows fed the BM3 diets had greater energy-corrected milk yield, higher milk true protein content, and lower milk urea nitrogen concentration than cows fed CON diets. Additionally, cows fed the BM3 diets had greater total-tract digestibility of organic matter and NDF than cows fed the CON diets. Compared with CON diets, the BMR diets accelerated ruminal NDF turnover. When incorporated into higher NDF diets, corn silage with greater in vitro 24-h NDFD and lower undegradable NDF at 240 h of in vitro fermentation (uNDF240) allowed for greater DMI intake than CON. In contrast, for lower NDF diets, NDFD of corn silage did not affect DMI, which suggests that a threshold level of inclusion of higher NDFD corn silage is necessary to observe enhanced lactational performance. Results suggest that there is a maximum gut fill of dietary uNDF240 and that higher NDFD corn silage can be fed at greater dietary concentrations.     

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.     

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.     

Corn grain endosperm type and brown midrib 3 corn silage: ruminal fermentation and N partitioning in lactating cows

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on ruminal fermentation and microbial efficiency of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber and 30% starch. Increasing ruminal starch digestibility by replacing vitreous corn grain with floury grain reduced mean and minimum ruminal pH. Brown midrib 3 corn silage reduced mean and minimum ruminal pH and increased total volatile fatty acid concentration. Ruminal pH was positively associated with rate of valerate absorption. Although floury endosperm reduced acetate:propionate ratio in both control and bm3 corn silage diets, it had a greater effect on reducing acetate:propionate ratio for control silage compared with bm3 corn silage. Nonammonia N flow to the duodenum did not differ among treatments and no effects of treatment were detected for microbial N and nonammonia, nonmicrobial N flow. Although treatment effects on ruminal fermentation and ruminal pH were observed, few interactions of treatment were detected and treatments did not affect flow of N fractions to the intestines.     

Corn grain endosperm type and brown midrib 3 corn silage: feeding behavior and milk yield of lactating cows

Interactions of endosperm type of corn grain and the brown midrib 3 mutation (bm3) in corn silage on feeding behavior, productivity, energy balance, and plasma metabolites of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous), and corn silage type (bm3 or isogenic control). Diets contained 26% neutral detergent fiber (NDF) and 30% starch. Floury endosperm grain decreased dry matter intake (DMI) 1.9 kg/ d compared with vitreous grain when combined with control corn silage but did not affect DMI when combined with bm3 corn silage. This interaction of treatments occurred because of changes in meal size; floury endosperm grain decreased meal size in control silage diets but increased meal size in bm3 corn silage diets. Ruminal pool sizes reflected DMI differences among diets, suggesting that ruminal fill was not the primary limitation on intake. Brown midrib 3 corn silage reduced rumination time per day and number of rumination bouts per day. Floury endosperm grain decreased 3.5% fat-corrected milk by 1.2 kg/d when combined with control silage but increased 3.5% fat-corrected milk by 2.1 kg/d when combined with bm3 corn silage. Starch and fiber digestibility interact to affect feeding behavior and milk production and production response to bm3 corn silage depends on the grain source that is fed.     

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.     

Comparison of feeding diets diluted with sorghum-sudangrass silage or low-quality grass on nutrient intake and digestibility and growth performance of Holstein dairy heifers

This study was carried out to evaluate the nutrient intakes and growth of dairy heifers offered an alfalfa silage–corn silage diet (CON; 14.3% crude protein, 61.1% total digestible nutrients, 47.9% neutral detergent fiber) compared with diets containing 1 of 2 types of sorghum-sudangrass (SS) silages: conventional or photoperiod sensitive. The objective of the study was to determine the potential to use SS to control dry matter (DM) and nutrient intakes and weight gain. Both diets were similar in nutrient composition, with approximately 13% crude protein, 60 to 61% total digestible nutrients, and 55% neutral detergent fiber. Seventy-two Holstein heifers (16–18 mo at study initiation) were blocked by initial body weight (light = 422 ± 12.8 kg; medium = 455 ± 14.8 kg; heavy = 489 ± 16.7 kg) with 3 pens assigned to each weight block (8 heifers/pen; 24 heifers/block). The 3 diets were randomly allocated to the pens within each block and offered for 12 wk. Heifers offered the CON diet had greater DM, protein, and energy intakes compared with those offered the SS silage-based diets due to the greater neutral detergent fiber concentration of the SS diets. With lower DM and nutrient intakes, average daily gain was in the recommended range (0.8–1 kg/d for Holstein heifers) for heifers offered the SS silage-based diets (mean of 0.92 kg/d for both SS diets vs. 1.11 kg/d for CON). Sorting behaviors for heifers offered both SS diets were more aggressive against long, medium, and short particles compared with those of heifers offered the CON diet; however, heifers sorted large particles from photoperiod-sensitive silage more aggressively than those from conventional silage. Based on this study, SS silage-based diets can control the DM and energy intakes for heifers and maintain optimum growth rates, with harvesting at a shorter chop length likely helping to alleviate sorting issues.     

Corn grain endosperm type and brown midrib 3 corn silage: site of digestion and ruminal digestion kinetics in lactating cows

Interactions of endosperm type of corn grain and the brown midrib 3 (bm3) mutation in corn silage on ruminal kinetics and site of nutrient digestion of lactating dairy cows were evaluated. Eight ruminally and duodenally cannulated cows (72 +/- 8 d in milk; mean +/- SD) were used in a duplicated 4 x 4 Latin square design experiment with a 2 x 2 factorial arrangement of treatments. Treatments were corn grain endosperm type (floury or vitreous) and corn silage type (bm3 or isogenic normal). Diets contained 26% neutral detergent fiber (NDF) and 30% starch. Interactions of treatments were not observed for any measure of digestibility, but digestion kinetics of starch and fiber did interact to affect digestible organic matter intake by affecting dry matter intake. Rate of ruminal starch digestion was faster and rate of ruminal starch passage tended to be slower in diets containing corn grain with floury vs. vitreous endosperm, resulting in a mean increase of 22 units for ruminal starch digestibility. Although compensatory postruminal starch digestion decreased differences among treatments for total tract starch digestibility, starch entering the duodenum was more digestible for grain with floury endosperm compared with vitreous grain, resulting in greater total tract starch digestibility for floury compared with vitreous corn grain. Fermentation rate of potentially digestible NDF was not affected by either bm3 corn silage or greater ruminal starch digestion of floury grain. Brown midrib corn silage increased total tract NDF digestibility vs. control silage by numerically increasing ruminal and postruminal digestibility of NDF. Endosperm type of corn grain greatly influences site of starch digestion and should be considered when formulating diets.     

Comparison of a corn silage hybrid with high cell-wall content and digestibility with a hybrid of lower cell-wall content on performance of Holstein cows

We hypothesized that substituting a corn hybrid with high cell-wall content and high neutral detergent fiber (NDF) digestibility (HCW) for a hybrid with lower cell-wall content and lower NDF digestibility (LCW) would improve feed intake and milk production in lactating Holstein cows. There was a 3.6 percentage unit difference in NDF content and a 4.1 percentage unit difference in 30-h in vitro NDF digestion between the 2 corn hybrids. In trial 1, 40 cows (12 primiparous) ranging in milk production from 24.1 to 44.0 kg/d, following a 2-wk preliminary period, were used in a crossover design with 2-wk periods. Diets consisted of 45% corn silage (HCW or LCW), 10% alfalfa hay, and 45% concentrates. The DMI (25.4 vs. 24.2 kg/d) and 4% FCM yield (34.3 vs. 31.7 kg/d) were higher for cows fed the HCW diet compared with the LCW diet. When HCW was substituted for LCW on a DM basis, there was no relationship between pretrial milk yield (preliminary period) and subsequent response to HCW silage. In trial 2, 40 cows (8 primiparous) ranging in milk production from 20.6 to 49.0 kg/d, following a 2-wk preliminary period, were used in a crossover design with 2-wk periods. Diets consisted of the same LCW diet as trial 1 and a diet containing HCW at a concentration (40% of DM) that resulted in equal NDF content (30.8%) between the 2 diets (HCWN). The DMI (26.8 kg/d) was unaffected by diet, although there was a trend for greater DMI (% of BW) for cows fed the HCWN diet compared with LCW silage (4.24 vs. 4.12). Milk fat (3.91 vs. 3.79%) and 4% FCM yield (34.9 vs. 33.4 kg/d) were greater for cows fed HCWN vs. LCW diet. When HCW was substituted for LCW silage on an NDF basis, cows with greater milk production during the preliminary period had a greater milk response to HCW than lower-producing cows. Results of these trials supported our hypothesis that HCW corn silage results in greater DMI and milk yield than LCW silage, whether substitution occurs on a DM or NDF basis.     

Comparison of brown midrib-6 and -18 forage sorghum with conventional sorghum and corn silage in diets of lactating dairy cows

Total mixed rations containing conventional forage sorghum, brown midrib (bmr)-6 forage sorghum, bmr-18 forage sorghum, or corn silage were fed to Holstein dairy cows to determine the effect on lactation, ruminal fermentation, and total tract nutrient digestion. Sixteen multiparous cows (4 ruminally fistulated; 124 d in milk) were assigned to 1 of 4 diets in a replicated Latin square design with 4-wk periods (21-d adaptation and 7 d of collection). Diets consisted of 40% test silage, 10% alfalfa silage, and 50% concentrate mix (dry basis). Acid detergent lignin concentration was reduced by 21 and 13%, respectively, for the bmr-6 and bmr-18 sorghum silages when compared with the conventional sorghum. Dry matter intake was not affected by diet. Production of 4% fat-corrected milk was greatest for cows fed bmr-6 (33.7 kg/d) and corn silage (33.3 kg/d), was least for cows fed the conventional sorghum (29.1 kg/d), and was intermediate for cows fed the bmr-18 sorghum (31.2 kg/d), which did not differ from any other diet. Total tract neutral detergent fiber (NDF) digestibility was greatest for the bmr-6 sorghum (54.4%) and corn silage (54.1%) diets and was lower for the conventional (40.8%) and bmr-18 sorghum (47.9%) diets. In situ extent of NDF digestion was greatest for the bmr-6 sorghum (76.4%) and corn silage (79.0%) diets, least for the conventional sorghum diet (70.4%), and intermediate for the bmr-18 sorghum silage diet (73.1%), which was not different from the other diets. Results of this study indicate that the bmr-6 sorghum hybrid outperformed the conventional sorghum hybrid; the bmr-18 sorghum was intermediate between conventional and bmr-6 in most cases. Additionally, the bmr-6 hybrid resulted in lactational performance equivalent to the corn hybrid used in this study. There are important compositional differences among bmr forage sorghum hybrids that need to be characterized to predict animal response accurately.     

Performance of lactating dairy cows fed ryegrass silage and corn silage with ground corn, steam-flaked corn, or hominy feed

Forty-eight mid-lactation Holstein cows were used in a 6-wk completely randomized block design trial with a 4 × 3 factorial arrangement of treatments to determine the effects of feeding different proportions of corn silage and ryegrass silage with supplemental ground corn (GC), steam-flaked corn (SFC), and hominy feed (HF) on the performance of lactating dairy cows. Forage provided 49% of the dietary dry matter in the experimental diets, which were formulated to meet National Research Council requirements. Ryegrass silage provided 100, 75, 50, or 25% of the total forage dry matter, with corn silage supplying the remainder. There were no interactions between the proportion of forage provided by ryegrass silage and energy supplement. Dry matter intake and milk protein percentage decreased linearly with increasing proportions of ryegrass silage, but milk protein yield was similar among forage treatments. There were no differences among forage treatments in milk yield, milk fat percentage and yield, and energy-corrected milk yield. Dry matter intake was higher and there was a tendency for increased milk fat percentage for GC compared with SFC or HF. No other differences were observed in milk yield or composition among energy supplements. Plasma urea nitrogen and glucose concentrations were similar among treatments. Under the conditions of this trial, our results indicate that feeding a combination of corn silage and ryegrass silage is more desirable than feeding ryegrass silage alone, whereas supplementation with GC, SFC, or HF supports similar levels of milk production.     

Effects of tallow in diets based on corn silage or alfalfa silage on digestion and nutrient use by lactating dairy cows

Six multiparous Holstein cows (average 31 days in milk; 36.3 kg/d of milk) fitted with ruminal cannulas were used in a 6 x 6 Latin square with 21-d periods to investigate the effects of diets that varied in forage source and amount of supplemental tallow. Isonitrogenous diets in a 2 x 3 factorial arrangement were based on either high corn silage (40:10 corn silage to alfalfa silage, % of dry matter) or high alfalfa silage (10:40 corn silage to alfalfa silage, % of dry matter) and contained 0, 2, or 4% tallow. Intakes of dry matter and total fatty acids were lower when cows were fed the high corn silage diet. Tallow supplementation linearly decreased dry matter intake. Milk yield was unaffected by diet; yields of milk fat and 3.5% fat-corrected milk were higher for the high alfalfa silage diet but were unaffected by tallow. Milk fat percentage was higher for the high alfalfa silage and tended to decrease when tallow was added to the high corn silage diet. Contents of trans-C18:1 isomers in milk fat were increased by high corn silage and tallow, and tended to be increased more when tallow was fed in the high corn silage diet. Ruminal pH and acetate:propionate were lower when high corn silage was fed. Ruminal acetate:propionate decreased linearly as tallow increased; the molar proportion of acetate was decreased more when tallow was added to the high corn silage diet. Ruminal liquid dilution rates were higher for the alfalfa silage diet; ruminal volume and solid passage rates were similar among diets. Total tract apparent digestibilities of dry matter, organic matter, crude protein, starch, energy, and total fatty acids were unaffected by diet. Digestibilities of neutral detergent fiber, acid detergent fiber, hemicellulose, and cellulose were lower when high corn silage was fed. The high alfalfa silage diet increased intakes of metabolizable energy and N, and increased milk energy and productive N. Tallow decreased the amount of N absorbed but had few other effects on utilization of energy or N. Tallow linearly increased concentrations of nonesterified fatty acids and cholesterol in plasma; cholesterol was increased by high alfalfa silage. Overall, forage source had more pronounced effects on production and metabolism than did tallow supplementation. Few interactions between forage source and tallow supplementation were detected except that ruminal fermentation and milk fat content were affected more negatively when tallow was fed in the high corn silage diet.