Adjusting for 30-hour undigested neutral detergent fiber in substitution of wheat straw and beet pulp for alfalfa hay and corn silage in the diet of high-producing cows

This study examined the feeding effects of wheat straw (WS) and beet pulp (BP) substituted for corn silage (CS) and alfalfa hay (AH) based on forage 30-h undigested neutral detergent fiber (uNDF₃₀) on lactation performance in high-producing dairy cows. Twelve multiparous (body weight = 611 ± 31 kg, days in milk = 97 ± 13; 51 ± 3 kg/d of milk; mean ± standard error) Holstein cows were used in a replicated 3 × 3 Latin square design with 28-d periods. Three treatments were established by substituting WS for CS and AH such that the concentration of forage uNDF₃₀ in all diets was the same. The treatments were (1) 0% forage uNDF₃₀ from WS (WS0; control), (2) 50% forage uNDF₃₀ from WS (WS50), and (3) 100% forage uNDF₃₀ from WS (WS100). Beet pulp was added in the straw diets to achieve similar dietary neutral detergent fiber digestibility after 30-h incubation (NDFD₃₀). The 3 diets were similar in forage uNDF₃₀ (14% of dry matter), total uNDF₃₀ (∼18.5% of dry matter), and NDFD₃₀ (approximately 42% of neutral detergent fiber). The substitution of WS and BP for AH and CS decreased the proportion of forage (40, 31, and 22.3% of dry matter) and forage neutral detergent fiber (21.2, 19.7, and 18.3% of dry matter) for WS0, WS50, and WS100, respectively, in the diet. However, the substitution linearly increased mean rumen pH (5.90, 6.09, and 6.28 for WS0, WS50, and WS100, respectively), digestibility of nutrients, and selection for long particles of diets without affecting dry matter intake. The substitution also linearly increased cholesterol and blood urea nitrogen concentration in the blood. Milk fat percentage, fat production, fat:protein ratio, and milk urea nitrogen increased linearly when treatments changed from WS0 to WS100, whereas the production of energy-corrected milk (ECM) was not affected by the treatments. Milk yield and milk protein yield were affected in a curvilinear manner and were lower in WS100 than other treatments. The efficiency of ECM production linearly increased in the diet with higher inclusion of WS and BP substitution in the diet (1.66, 1.70, and 1.72 for WS0, WS50, and WS100, respectively), but body weight, body weight change, and backfat thickness of cows were not different among treatments. In conclusion, the substitution of WS and BP for CS and AH with fixed uNDF₃₀ improved feed efficiency and rumen pH, decreased milk and protein yield, and did not affect ECM yield.     

Dried distillers grains plus solubles with corn silage or alfalfa hay as the primary forage source in dairy cow diets

Nine multiparous (250 ± 6 d in milk) and 3 primiparous (204 ± 6 d in milk) Holstein cows were utilized in a 3 × 3 Latin square design to evaluate the lactation performance of cows fed a diet containing dried distillers grains plus solubles (DDGS) with either corn silage or alfalfa hay as forage. Cows were fed total mixed diets containing corn silage (CS), 50% corn silage and 50% alfalfa hay (CSAH), or alfalfa hay (AH) as the forage source. All diets had a 50:50 forage-to-concentrate ratio, contained 15% DDGS, and were formulated to be equal in metabolizable protein. Dry matter intake increased when cows were fed CSAH (24.9 kg/d) compared with CS (21.9 kg/d) and AH (20.9 kg/d). Yields of milk (26.5, 28.4, 29.0 kg/d for CS, CSAH, and AH, respectively) increased linearly as proportions of alfalfa fed increased but 4% fat-corrected milk and energy-corrected milk were not affected by treatment. Feed efficiency (1.28, 1.23, and 1.45 kg of energy-corrected milk/kg of intake) improved when AH was fed compared with CS or CSAH. Milk fat concentration (3.67, 3.55, and 3.49%) decreased linearly when alfalfa replaced corn silage, but was observed only in primiparous cows, not multiparous cows. Milk protein concentration (3.32, 3.29, and 3.29%) was not affected by diet although yield (0.90, 0.96, and 0.98 kg/d) tended to increase linearly when alfalfa was added to the diet. This may have been due to an increase in essential amino acid (AA) availability and uptake by the mammary gland or to greater crude protein intake in cows fed AH. In addition, replacing corn silage with alfalfa increased the uptake of Lys by the mammary gland. Methionine was the first-limiting AA based on the transfer efficiency of AA in arterial plasma to milk protein. However, Lys was the first-limiting AA in CS and CSAH and Met was first limiting in AH for mammary gland extraction efficiency of AA from plasma. In conclusion, replacing corn silage with alfalfa hay in diets containing 15% DDGS increased milk yield and tended to increase milk protein yield linearly in cows during late lactation. Feeding alfalfa hay as the sole forage source improved feed efficiency compared with diets containing corn silage.     

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.     

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

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

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.     

Fibrous coproducts of corn and citrus as forage and concentrate sources for dairy cows

This study evaluated the effect on dairy cows of the partial replacement of whole plant corn silage (WPCS) with corn ear fibrous coproduct (CEFC) in diets with concentrate coproducts from citrus and corn on dry matter intake (DMI), lactation performance, digestibility, and chewing behavior. Holstein dairy cows (n = 20) in 5, 4 × 4 Latin squares (21-d periods) were fed a combination of strategies for feeding fibrous coproducts in a 2 × 2 factorial arrangement of the following treatments: (1) forage feeds: the partial replacement of WPCS (CS) with CEFC (CO), and (2) concentrate feeds: the partial replacement of wet corn gluten feed (GF) with a blend of pelleted citrus and corn distillers dried grains (CD) to have isonitrogenous diets. The concentrations of physically effective neutral detergent fiber (NDF; _peNDF_>8) were (% of dry matter): 21.8% for CS, 19.2% for CO, 20.7% for GF, and 20.2% for CD. Cows fed diet CS-CD had the highest yield of energy-corrected milk (30.0 kg/d) relative to the other diets (28.4 kg/d). Milk fat concentration was reduced on CO relative to CS. Cows fed the CO diets had higher DMI (21.2 vs. 20.2 kg/d) and digestible organic matter intake and tended to have a lower ratio of energy-corrected milk to DMI than cows fed CS. Diets CO reduced the daily intake of _peNDF_>8 and the intake as percent of body weight of _peNDF_>8, forage NDF, and total NDF relative to CS. Cows fed CO had greater meal frequency and lower daily meal time, meal duration, meal size, and duration of the largest meal than cows fed CS. The CO diet reduced rumination and total chewing in minutes per day and minutes per kilogram of DMI. When expressed per unit of _peNDF_>8 intake, rumination and total chewing were not affected by forage source. The total-tract starch digestibility coefficient was lower for cows fed CO than CS, but the intake of digestible starch was higher on CO than CS. Cows fed GF had reduced milk yield (29.6 vs. 30.8 kg/d), tended to have reduced DMI (20.4 vs. 21.0 kg/d), and had reduced digestible organic matter intake than cows fed CD. Feed efficiency was not affected by source of concentrate. The type of concentrate did not affect the intake of forage NDF and _peNDF_>8, but cows fed GF had higher intake of total NDF as percent of body weight than cows fed CD. The GF increased meal frequency and reduced meal size and largest meal duration and size. Cows fed GF had higher rumination and total chewing than cows fed CD (min/d, min/kg of DMI, and min/kg _peNDF_>8). Starch digestibility was higher and the intake of digestible starch tended to be higher on cows fed GF than CD. Plasma urea-N was higher, milk urea-N tended to be higher, and N utilization efficiency tended to be lower on cows fed GF than CD. Ruminal microbial yield was not affected by any treatment. All strategies evaluated were nutritionally viable and CEFC was a feasible partial replacement for WPCS.     

Chewing,rumen pool characteristics,and lactation performance of dairy cows fed 2 concentrations of a corn wet-milling coproduct with different forage sources

We used a novel corn wet-milling coproduct [CMP; approximately 70% dry matter, 28% crude protein, 36% neutral detergent fiber (NDF), and 18% nonstructural carbohydrates] in diets formulated to contain 18.4% forage NDF, 17.4% crude protein, 20.2% starch, and 3.7% sugar. Six primiparous, rumen-cannulated Jersey cows were assigned to a 6 × 6 Latin square design with a 2 × 3 factorial arrangement of treatments. Diets were formulated to contain 20 and 30% CMP with 3 forage sources [corn silage (CS) and 40.5% NDF, CS replaced with 10% alfalfa hay (AH) and 45.0% NDF, or CS replaced with 7% grass hay (GH) and 67.4% NDF], with each providing 18.4% forage NDF in the diet. Total-tract digestibilities of NDF, N, and organic matter were not affected by treatment. Similarly, no treatment effects were detected for kinetics of NDF disappearance in situ from CMP or respective forage source or for N disappearance in situ from CMP. Grass hay increased total and liquid pool size of rumen contents compared with AH (by 3.2 and 3.0 kg, respectively). Total time spent chewing increased in cows fed GH by over 35 min compared with those fed AH, partially due to a trend for increased minutes spent ruminating. Mean particle size of rumen contents also tended to be higher in the GH (0.55 mm) than AH (0.69 mm) diets. No effects on production of milk or milk components were detected, but dry matter intake (DMI) tended to decrease when CMP increased from 20 to 30%. Gross feed efficiency (fat-corrected milk/DMI) tended to be greater when cows were fed AH and GH compared with CS and was greater for AH than GH diets. In diets containing low starch, increasing CMP from 20 to 30% potentially maintained similar fat-corrected milk production with lower DMI. However, more consideration also should be given to interactions among forages with respect to fill, digestion, and passage of fiber with increased inclusion rates of CMP.     

Milk production, nitrogen balance, and fiber digestibility prediction of corn, whole plant grain sorghum, and forage sorghum silages in the dairy cow

Total mixed rations containing corn (CS), whole plant grain sorghum (WPGS), or forage sorghum (FS) silages were fed to 6 primiparous Italian Friesian cows to determine the effects on lactation performance, nutrient digestibility, and N balance. Furthermore, the relationship between in vivo total-tract neutral detergent fiber (NDF) digestibility (ttNDFD) and the ttNDFD derived by the Cornell Net Carbohydrate and Protein System (CNCPS) model was assessed. Cows were assigned to 1 of 3 diets in a replicated 3 × 3 Latin square with 28-d periods. The experimental treatment was silage type and 3 different silages were included in the diets. The diets were formulated to be iso-NDF. Accordingly, each diet was formulated to contain 41.5% CS silage, 36.7% WPGS silage, or 28.0% FS silage, on a DM basis. Starch content was balanced by adding the appropriate amount of corn meal. Separate collection of total urine and feces was performed. Dietary forages were analyzed for in vitro NDF digestibility (6 and 24h of incubation) to predict fiber digestion rate with 2 NDF pools (digestible and indigestible). Rumen digestibility of the potentially digestible NDF pool was predicted using CNCPS version 6.1, using the in vitro forage fiber digestion rate. The ttNDFD was predicted assuming that intestinal digestibility of the NDF amount escaping rumen digestion was 20%, according to the CNCPS model. Dry matter intake was decreased by approximately 1.8 kg/d in cows fed the FS diet compared with the other diets, probably for the greater particle size of FS diet. Hence, milk yield (kg/d) was lowest for FS (23.6), intermediate for WPGS (24.6), and highest for the CS diet (25.4). Milk urea N (mg/dL) was highest for FS (12.9), intermediate for WPGS (11.9), and lowest for CS (10.7) diet. In vivo ttNDFD (%) was 51.4 (CS), 48.6 (WPGS), and 54.1 (FS); this was probably due to a higher retention time of FS diet in the rumen rather than to a better quality of the FS silage, as confirmed by in situ and in vitro results. Urinary N excretion (% N intake) was highest for FS (31.8), intermediate for WPGS (29.3), and lowest for the CS (27.5) diet. The predicted ttNDFD (37.7, 36.3, and 39.5% for CS, WPGS, and FS, respectively) were lower than the in vivo results. Providing an adequate starch supplementation, whole plant grain sorghum silage can replace corn silage in dairy cows TMR. Forage sorghum silage had rumen NDF digestibility comparable to the other silages; however, it had a negative effect on dry matter intake and milk production, probably due to an inadequate effect of processing.     

Effects of alfalfa and cereal straw as a forage source on nutrient digestibility and lactation performance in lactating dairy cows

This study was conducted to investigate the nutrient digestibility and lactation performance when alfalfa was replaced with rice straw or corn stover in the diet of lactating cows. Forty-five multiparous Holstein dairy cows were blocked based on days in milk (164 ± 24.8 d; mean ± standard deviation) and milk yield (29.7 ± 4.7 kg; mean ± standard deviation) and were randomly assigned to 1 of 3 treatments. Diets were isonitrogenous, with a forage-to-concentrate ratio of 45:55 [dry matter (DM) basis] and contained identical concentrate mixtures and 15% corn silage, with different forage sources (on a DM basis): 23% alfalfa hay and 7% Chinese wild rye hay (AH), 30% corn stover (CS), and 30% rice straw (RS). The experiment was conducted over a 14-wk period, with the first 2 wk for adaptation. The DM intake of the cows was not affected by forage source. Yield of milk, milk fat, protein, lactose, and total solids was higher in cows fed diets of AH than diets of RS or CS, with no difference between RS and CS. Contents of milk protein and total solids were higher in AH than in RS, with no difference between CS and AH or RS. Feed efficiency (milk yield/DM intake) was highest for cows fed AH, followed by RS and CS. Cows fed AH excreted more urinary purine derivatives, indicating that the microbial crude protein yield may be higher for the AH diet than for RS and CS, which may be attributed to the higher content of fermentable carbohydrates in AH than in RS and CS. Total-tract apparent digestibilities of all the nutrients were higher in cows fed the AH diet than those fed CS and RS. The concentration of rumen volatile fatty acids was higher in the AH diet than in CS or RS diets, with no difference between CS and RS diets. When the cereal straw was used to replace alfalfa as a main forage source for lactating cows, the shortage of fermented energy may have reduced the rumen microbial protein synthesis, resulting in lower milk protein yield, and lower nutrient digestibility may have restricted milk production.     

Effects of dietary forage level and monensin on lactation performance, digestibility and fecal excretion of nutrients, and efficiency of feed nitrogen utilization of Holstein dairy cows

Two experiments (Exp. 1 and 2) were conducted using a 4 × 4 Latin square design with 2 replications (n = 8) to evaluate effects of feeding Holstein dairy cows a total mixed ration containing 50 or 60% of ration dry matter (DM) from forages with or without supplementation of monensin. In Exp. 1, alfalfa silage (AS) was used as the major forage (55% forage DM), and corn silage (CS; 45% forage DM) was used to make up the rest of the forage portion of diets (55AS:45CS). In Exp. 2, CS was used as the major forage (70% forage DM) and alfalfa hay (AH; 30% forage DM) was used to make up the rest of the forage portion of diets (70CS:30AH). Experimental diets were arranged in a 2 × 2 factorial with 50 or 60% ration DM from forages and monensin supplemented at 0 or 300 mg/cow daily. In Exp. 1 (55AS:45CS), feeding 60% forage diets decreased DM intake (DMI; 27.3 vs. 29.6 kg/d) but maintained the same levels of milk (45.8 vs. 47.0 kg/d) compared with 50% forage diets. The efficiency of converting feed to milk or 3.5% fat-corrected milk was greater for cows fed 60% compared with 50% forage diets (1.7 vs. 1.6 kg milk or 3.5% fat-corrected milk/kg of DMI, respectively). Increasing dietary forage level from 50 to 60% of ration DM increased milk fat percentage (3.4 to 3.5%); however, adding monensin to the 60% forage diet inhibited the increase in milk fat percentage. Feeding 60% forage diets decreased feed cost, but this decrease ($0.5/head per day) in feed cost did not affect income over feed cost. Feeding 60% forage diets decreased fecal excretion of DM (10.6 to 9.6 kg/d) and nitrogen (N; 354 to 324 g/d) and improved apparent digestibility of neutral detergent fiber from 43 to 49% and apparent efficiency of feed N utilization from 32.3 to 35.9% compared with 50% forage diets. In Exp. 2 (70CS:30AH), feeding 60% forage diets decreased DMI from 29.6 to 28.2 kg but maintained the same level of milk (41.1 vs. 40.8 kg/d) and therefore increased the efficiency of converting feed to milk (1.46 vs. 1.38 kg milk/kg DMI) compared with 50% forage diets. Daily feed cost for feeding 60% forage diets was $0.3/head lower than for the 50% forage diets. Fecal excretion of DM (10.3 vs. 11.5 kg/d) was lower and fecal excretion of N (299 vs. 328 g/d) tended to be lower for 60% compared with 50% forage diets. Results from these 2 experiments suggest that a 60% forage diet consisting of either AS or CS as the major forage can be fed to high producing Holstein dairy cows without affecting milk production while improving or maintaining the efficiency of converting feed to milk and the apparent efficiency of utilization of feed N. Cows receiving a 60% forage diet had a similar or improved digestibility of nutrients with a similar or reduced fecal excretion of nutrients. Effects of monensin under the conditions of the current experiments were minimal.     

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.     

Intake and milk production of cows fed diets that differed in dietary neutral detergent fiber and neutral detergent fiber digestibility

The objectives of this study were to determine how feeding diets that differed in dietary neutral detergent fiber (NDF) concentration and in vitro NDF digestibility affects dry matter (DM) intake, ruminal fermentation, and milk production in early lactation dairy cows. Twelve rumen-cannulated, multiparous Holstein cows averaging 38 ± 15 d (±standard deviation) in milk, and producing 40 ± 9 kg of milk daily, were used in a replicated 4 × 4 Latin square design with 28-d periods. Treatment diets were arranged in a 2 × 2 factorial with 28 or 32% dietary NDF (DM basis) and 2 levels of straw NDF digestibility: 1) LD, untreated wheat straw (77% NDF, 41% NDF digestibility) or 2) HD, anhydrous NH₃-treated wheat straw (76% NDF, 62% NDF digestibility). All 4 diets consisted of wheat straw, alfalfa silage, corn silage, and a concentrate mix of cracked corn grain, corn gluten meal, 48% soybean meal, and vitamins and minerals. Wheat straw comprised 8.5% DM of the 28% NDF diets and 16% DM of the 32% NDF diets. Cows fed 28% NDF and HD diets produced more milk, fat, and protein than those consuming 32% NDF or LD diets. Dry matter intake was greater for cows consuming 28% NDF diets, but intakes of DM and total NDF were not affected by in vitro NDF digestibility. Intake of digestible NDF was greater for cows consuming HD diets. Ruminal fermentation was not affected by feeding diets that differed in NDF digestibility. Ruminal NDF passage rate was slower for cows fed HD than LD. No interactions of dietary NDF concentration and in vitro NDF digestibility were observed for any parameter measured. Regardless of dietary NDF concentration, increased in vitro NDF digestibility improved intake and production in early lactation dairy cows.     

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

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

Effects of feeding alfalfa hay on chewing, rumen pH, and milk fat concentration of dairy cows fed wheat dried distillers grains with solubles as a partial substitute for barley silage

The objective of this study was to determine the effects of feeding alfalfa hay on chewing activity, rumen fermentation, and milk fat concentration of dairy cows fed wheat-based dried distillers grains with solubles (DDGS) as a partial replacement of barley silage. Thirty lactating Holstein cows (220 ± 51 DIM), 6 of which were ruminally cannulated, were used in a 3 × 3 Latin square design with 21-d periods. Cows were fed a control diet [CON; 50% barley silage and 50% concentrate mix on a dry matter (DM) basis], a diet in which barley silage was replaced with DDGS at 20% of dietary DM (DG), or a diet in which barley silage was replaced with DDGS and alfalfa hay at 20 and 10% of dietary DM, respectively (DG+AH). All diets contained approximately 20% crude protein. Compared with the CON diet, cows fed DG and DG+AH diets respectively had greater DM intake (20.1 vs. 23.1 and 22.7 kg/d); yields of milk (24.5 vs. 27.3 and 28.1 kg/d), milk protein (0.88 vs. 0.99 and 1.01 kg/d), and milk lactose (1.11 vs. 1.24 and 1.29 kg/d); and body weight gain (0.25 vs. 1.17 and 1.23 kg/d). However, compared with cows fed the CON diet, cows fed the DG and DG+AH diets respectively had lower chewing time (38.3 vs. 30.7 and 31.5 min/kg of DM intake), mean rumen pH (6.11 vs. 5.88 and 5.84), and minimum rumen pH (5.28 vs. 5.09 and 5.07) and a greater duration that rumen pH was below 5.8 (7.3 vs. 11.2 and 12.0 h/d). However, these response variables did not differ between cows fed the DG and DG+AH diets. Milk fat concentration differed among the 3 diets (3.92, 3.60, and 3.38% for CON, DG, and DG+AH, respectively), but milk fat yield was not affected by treatment. These results indicate that partially replacing barley silage with DDGS can improve productivity of lactating dairy cows but may decrease chewing time, rumen pH, and milk fat concentration, and that dietary inclusion of alfalfa hay may not alleviate such responses.     

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.     

Effect of source of trace minerals in either forage- or by-product–based diets fed to dairy cows: 1. Production and macronutrient digestibility

Excess rumen-soluble Cu and Zn can alter rumen microbial populations and reduce fiber digestibility. Because of differences in particle size and chemical composition, ruminal and total-tract digestibility of fiber from forage- and by-product–based diets can differ. We hypothesized that, because of differences in mineral solubility, diets with hydroxy rather than sulfate trace minerals would have greater fiber digestibility, but the effect may depend on source of fiber. Eighteen multiparous cows were used in a split-plot replicated Latin square with two 28-d periods to evaluate the effects of Cu, Zn, and Mn source (sulfates or hydroxy; Micronutrients USA LLC, Indianapolis, IN) and neutral detergent fiber (NDF) source (forage diet = 26% NDF vs. by-product = 36%) on total-tract nutrient digestibility. During the entire experiment (56 d) cows remained on the same fiber treatment, but source of supplemental trace mineral was different for each 28-d period so that all cows were exposed to both mineral treatments. During each of the two 28-d periods, cows were fed no supplemental Cu, Zn, or Mn for 16 d followed by 12 d of feeding supplemental Cu, Zn, and Mn from either sulfates or hydroxy sources. Supplemental minerals for each of the mineral sources fed provided approximately 10, 35, and 32 mg/kg of supplemental Cu, Zn, and Mn, respectively, for both fiber treatments. Total dietary concentrations of Cu, Zn, and Mn were approximately 19, 65, and 70 mg/kg for the forage diets and 21, 85, and 79 mg/kg for the by-product diets, respectively. Treatment had no effect on dry matter intake (24.2 kg/d) or milk production (34.9 kg/d). Milk fatty acid profiles were altered by fiber source, mineral source, and their interaction. Cows fed the by-product diets had lower dry matter (65.9 vs. 70.2%), organic matter (67.4 vs. 71.7%), and crude protein digestibility (58.8 vs. 62.1%) but greater starch (97.5 vs. 96.3%) and NDF digestibility (50.5 vs. 44.4%) compared with cows fed the forage treatment. Feeding increased concentrations of by-products decreased total digestible nutrients regardless of mineral source. Feeding hydroxy Cu, Zn, and Mn increased NDF digestibility (48.5 vs. 46.4%) but had no effect on total digestible nutrients.     

Diets varying in ratio of sweet sorghum silage to corn silage for lactating dairy cows: Feed intake,milk production,blood biochemistry,ruminal fermentation,and ruminal microbial community

The objective of this study was to investigate the effects of partial substitution of corn silage (CS) with sweet sorghum silage (SS) in the diets of lactating dairy cows on dry matter (DM) intake, milk yield and composition, blood biochemistry, and ruminal fermentation and microbial community. Thirty mid-lactation Holstein dairy cows [mean ± standard deviation; 639 ± 42.0 kg of body weight; 112 ± 24.0 d in milk (DIM)] were assigned to 3 groups (n = 10/treatment) by considering parity, milk yield, and DIM. The cows were fed ad libitum total mixed rations containing 55% forage and 45% concentrate, with only the proportion of CS and SS varying in 3 treatments (DM basis): SS0 (0% substitution of CS), 40% CS and 0% SS; SS25 (25% substitution of CS)_, 30% CS and 10% SS; and SS50 (50% substitution of CS)_, 20% CS and 20% SS. Dry matter intake and milk protein concentration tended to linearly decrease with increasing proportion of SS in the diet. Yields of milk (mean ± standard deviation, 30.9 ± 1.12 kg/d), 4% fat-corrected milk (30.0 ± 0.81 kg/d), energy-corrected milk, milk protein, lactose, and total solids, concentrations of milk fat, lactose, somatic cell counts, and milk efficiency did not differ among diets. The concentrations in blood of urea nitrogen, phosphorus, aspartate aminotransferase, and malondialdehyde linearly increased with increasing SS proportion. Blood IgA decreased with increasing SS substitution rate, but blood IgG and IgM were not different among diets. Ruminal pH did not differ among diets, whereas ruminal NH₃-N concentration quadratically changed such that it was greater for SS50 than for SS0 and SS25. Molar proportions of propionate and acetate to propionate ratio were less for SS25 than for SS0. Although the diversity and general ruminal microbial community structure were not altered by partially replacing CS with SS, the relative abundances of predominant bacteria were affected by diets at the phylum and genus levels. Firmicutes and Bacteroidetes were dominant phyla in the ruminal bacterial community for all diets, and their relative abundance linearly decreased and increased, respectively, with increasing SS substitution rate. Prevotella_1 and Ruminococcaceae_NK4A214_group were detected as the most and the second most abundant genera, with their relative abundance linearly increased and decreased, respectively, with increasing SS substitution rate. The relative abundance of Fibrobacter linearly increased with increasing dietary SS proportion, with greater abundance observed for SS25 and SS50 than for SS0. These results suggest that substitution of CS with SS altered the relative abundances of some predominant bacteria; however, these changes had little effect on ruminal fermentation and milk yield. Under the current experimental conditions, substituting up to 50% of CS with SS had no negative effects on milk yield, indicating that SS can partially replace CS in the diets of high-producing lactating dairy cows without adding extra grain, when diets are fed for a short time. As the effects of substituting CS with SS depend upon the chemical composition and digestibility of these silages and the nutrient requirements of the cows, additional grain may be required in some cases to compensate for the lower starch content of SS.     

Production performance and nutrient digestibility of lactating dairy cows fed low-forage diets with and without the addition of a live-yeast supplement

We aimed to evaluate the use of a live-yeast product as a means to attenuate plausible nutritional disturbances when feeding relatively low-forage diets containing rapidly fermentable carbohydrates (i.e., wheat) to high-producing cows in early to mid lactation. Eight primiparous [mean ± SD; 569 ± 35 kg of body weight (BW) and 80 ± 29 d in milk (DIM) at the beginning of the experiment] and 16 multiparous (665 ± 67 kg of BW and 64 ± 10 DIM at the beginning of the experiment) Holstein cows were blocked by parity and DIM, and randomly assigned to 1 of 2 diets (control vs. yeast) for a 12-wk-long period according to randomized complete block design. The formulated diets contained 36.7% corn silage, 8.3% alfalfa hay, and 55% concentrate. The yeast diet was formulated to provide approximately 5.4 × 10¹¹ cfu/d of Saccharomyces cerevisiae (BeneSacc; Global Nutritech Biotechnology LLC, Richmond, VA). Total-tract nutrient digestibility was estimated using 240-h undigested neutral detergent fiber (NDF) as an internal marker. Dry matter intake, milk yield, and milk component concentrations and yields were analyzed using repeated measures. The statistical model for these variables included the effects of block, treatment, the block by treatment interaction, week, the treatment by week interaction, and the random residual error. The statistical model for analyzing BW gain, body condition score gain, and dry matter and nutrient digestibilities included the effects of block, treatment, and the random residual error. Supplementing live yeast to lactating dairy cows did not affect dry matter intake (26.0 kg/d), milk yield (48.1 kg/d), milk fat concentration (3.61%), milk fat yield (1.72 kg/d), milk protein concentration (2.96%), milk protein yield (1.43 kg/d), milk lactose concentration (4.84%), milk lactose yield (2.35 kg/d), milk urea nitrogen (7.99 mg/dL), body weight gain (0.62 kg/d), and body condition score gain (0.02 units; all averages of the 2 treatments). The digestibilities of dry matter (70.2%), crude protein (71.4%), NDF (36.4%), and starch (99.8%) were not affected by treatments. In conclusion, the supplementation of the live yeast did not affect production performance and nutrient digestibility of high-producing dairy cows. A potential interaction between live-yeast supplementation and NDF passage rate, which may have hindered the beneficial effects of live-yeast supplementation on production performance and nutrient utilization, deserves further research.     

Replacing alfalfa hay with triticale hay has minimal effects on lactation performance and nitrogen utilization of dairy cows in a semi-arid region of Mexico

In the semi-arid highlands of central Mexico, triticale (× Triticosecale L.) is emerging as an alternative, less water-demanding forage crop than alfalfa for dairy cattle. Studies reported here were aimed at evaluating triticale hay (TH) relative to alfalfa hay (AH) for lactating cow performance, apparent digestibility, N partition, and ruminal degradation kinetics of dry matter (DM), crude protein (CP), and neutral detergent fiber (NDF). Study 1 was conducted on a privately owned farm. Four barns were used to conduct 4 replicated 3 × 3 Latin squares (1 barn = 1 square), where each barn included 3 pens (experimental units) receiving 1 of 3 dietary treatments. Each pen had 62 Holstein dairy cows. All diets included a forage-to-concentrate ratio of 42:58 (DM basis), which is typical for intensive dairy farms of the region. Dietary treatments were formulated to replace AH with TH on a CP basis, and included (DM basis) 15.1% AH and 0% TH, 9.0% AH and 7.4% TH, and 0% AH and 16.4% TH. Diets were iso-energetic (1.64 Mcal of net energy for lactation/kg of DM) and iso-nitrogenous (17.9% CP). Pen-level DM intake and milk production were from all cows in the pen, but pen-level milk composition, apparent digestibility, and N partitioning were from 8 cows (observational units) randomly selected in each pen. Orthogonal contrasts were used to determine linear and quadratic effects of increasing TH from 0 to 7.4, and 16.4% of dietary DM. Although DM intake was not affected, there was a tendency for CP intake to decline linearly and for NDF intake to increased linearly as TH replaced AH in the diet. Milk production declined linearly by 0.077 kg/d for each additional percentage unit of TH in the diet, which amounted to a 3.5% decline when TH replaced AH entirely. However, no effect was observed on energy-corrected milk production because of a compensatory linear effect of increasing milk fat concentration with the incorporation of TH in the diet. Total-tract NDF digestibility tended to increase linearly by 18.5%, but no differences were detected for urinary urea-N excretion and for N utilization estimated as milk N/(fecal N + urinary N + milk N). Study 2 was an in situ trial conducted to determine the degradation kinetics of AH and TH used in study 1. In spite of differences in degradation kinetics parameters for DM, CP, and NDF, only NDF effective ruminal degradation tended to be greater for TH than AH. Replacing AH with TH at the level typically found in intensive dairy farms of the semi-arid regions of Mexico had minimal effects on milk production and N utilization.