Effect of forage to concentrate ratio and intake level on utilization of early vegetative alfalfa silage by dairy cows.

Two experiments were conducted to measure the effects of intake and forage: grain ratio on utilization of early maturity alfalfa silage in dairy cows. In Experiment 1, diets with three forage: concentrate ratios (percentage of silage, percentage NDF): low (56, 28.3), medium (71, 31.0), or high (86, 33.4) were fed ad libitum to six lactating, ruminally cannulated cows in a replicated 3 x 3 Latin square. The same diets were then fed at 1.3 x maintenance intake to six gestating dry cows. Dairy milk yield and percentage and yield of milk protein and casein were higher for cows fed the low silage diet than for cows receiving other treatments. Fat percentage and yield were not different among diets. Lactating cows consumed more DM on low silage (23.0 kg/d) than on medium or high silage diets (21.4 kg), but NDF intake as percentage of BW was higher for the high silage diet. Digestibility of DM in the lactating (70.7, 69.9, and 67.5% for low, medium, and high) and dry cows (76.7, 73.5, and 69.0%, respectively) decreased as the level of silage increased. Depression in digestibility was greater as dietary concentrate increased. Cows fed the high silage diet had a faster fractional passage rate of solids and higher rumen fill. Digestion of concentrate cell walls appeared to be depressed more than alfalfa cell walls as intake increased.     

Effects of feeding alkaline hydrogen peroxide-treated wheat straw-based diets on digestion and production by dairy cows

Twelve Holstein cows, averaging 34 d postpartum, were used in three replications of a 4 x 4 Latin square design to determine the effects of feeding different levels of alkaline hydrogen peroxide-treated wheat straw on digestion and production responses in lactating dairy cows. Complete mixed diets consisted of 50% concentrate (DM basis) plus varying proportions of treated wheat straw, alfalfa haylage, and corn silage as the forage source. Treatment contained 0 (control), 12.5 (low), 25.0 (medium), or 37.5% (high) treated wheat straw in the diet. Dry matter intakes were 18.5, 17.2, 17.4, and 16.7 kg/d for the four treatments, respectively. Apparent digestibilities of DM and OM were decreased (approximately 4.4 percentage units), and NDF and ADF digestibilities were increased by 9.4 and 3.0 percentage units, respectively, with the high wheat straw diet. Yields of milk and 4% FCM, and SNF percentage did not differ among the treatment groups. Milk fat percentage increased (from 3.07 to 3.32%) and milk protein percentage decreased (from 2.61 to 2.56%) as the proportion of treated wheat straw increased in the diet. Cows fed the higher proportions of treated wheat straw had increased ruminal concentrations of total VFA and molar percentage acetate but a decreased molar percentage propionate, resulting in a greater acetate to propionate ratio. Cows fed the low and medium wheat straw diets had slightly lower DM intakes but production responses were similar to cows fed the control diet containing alfalfa haylage and corn silage as fiber sources.     

Influence of forage type, ratio of forage to concentrate, and methionine hydroxy analog on performance of dairy cows.

In a 2-yr study, 44 primiparous and 77 multiparous cows were assigned to one of 12 dietary treatments (2 X 3 X 2 factorial). Treatments were two forages (alfalfa or smooth bromegrass), three percentages of grain (40, 50 or 60% of diet DM), and two percentages of methionine hydroxy analog (0 or .15% of diet DM). Feeds were offered as total mixed diets. Data collection began 4 d postpartum and continued through 116 d postpartum. Dry matter intake was not affected by percentage of concentrate or forage source even though NDF of the diets ranged from 25.6 to 48.8% and ADF ranged from 15.7 to 36.8%. Cows fed bromegrass hay produced 1.5 kg/d more FCM and 1.2 kg/d more SCM than those fed alfalfa hay. Concentrate percentage in the diet increased milk yield (28.9, 30.4 and 31.3 kg/d at 40, 50 and 60%, respectively). Methionine hydroxy analog increased milk fat percentage and yield for cows fed diets of 50 and 60% concentrate with alfalfa hay but not for those fed diets of 50 and 60% concentrate with bromegrass hay. Effect of methionine hydroxy analog was not significant for milk fat or yield when diets of 40% concentrate were fed.     

Effect of fiber content and particle size of alfalfa silage on performance and chewing behavior.

A low NDF drought-stressed 1988 alfalfa silage (32.6% NDF) and a higher fiber 1988 alfalfa silage (46.4% NDF) were fed to lactating cows to evaluate effects on feed intake, fat test, and chewing behavior. Two groups of Holstein cows, 16 primiparous housed in tie stalls and 16 multiparous in free stalls, were assigned to diets based on parity and milk yield. The low NDF silage was fed for 6 wk in a TMR with 21.5% NDF and was compared with a TMR with 31.9% NDF. During an additional 4-wk period, one-half of each dietary group was fed a ration in which one-half of each silage was rechopped to reduce particle size. All rations contained a 1:1 ratio of forages to concentrates (DM basis) and were fed for ad libitum intake. Diets with 21.5% NDF and reduced particle size had no influence on milk fat percentage, 4% FCM yield, or plasma glucose. Cows fed these diets had reduced chewing time, due largely to decreased rumination time. Rumination and total chewing times per unit DMI and FCM also were lowest on these diets. Intake of DM on a BW basis was lowest for cows fed the low NDF rechopped silage diet. Cows fed in tie stalls had more eating bouts than those in free stalls, but total eating times were similar. Sufficient amounts of effective fiber appeared to be present in low NDF and rechopped silage diets to prevent the systemic events leading to milk fat depression but not to prevent a reduction in chewing time.     

Use of a corn milling product in diets for dairy cows to alleviate milk fat depression

Various diet formulation strategies were evaluated to alleviate milk fat depression using a corn milling product (CMP) that contained approximately 28% crude protein, 34% neutral detergent fiber (NDF), and 12% starch (dry basis). The control diet comprised mostly corn silage, alfalfa silage, corn grain, and soybean meal and contained approximately 22% forage NDF (fNDF), 28% total NDF, and 33% starch. Another diet included 25% CMP that replaced corn grain and soybean meal and contained 27% starch and 33% NDF. Two other diets included 25 or 40% CMP that replaced forage and concentrate and contained 19 and 17% fNDF, 31 and 32% total NDF, and 30 and 28% starch, respectively. Diets were fed to 16 mid-lactation Holstein cows in 4 replicated 4 × 4 Latin squares. Milk fat percentage was low for the control diet (2.9%) but increased to 3.5% when cows were fed the diet with 25% CMP that replaced concentrate. Cows fed diets with 25 or 40% CMP that replaced forage and concentrate also had low milk fat percentages (3.0 and 2.9%, respectively). Intake was lowest for cows fed the control diet. Milk yield was reduced when CMP replaced only concentrate but because of the substantial increase in milk fat, the yield of energy-corrected milk was greater. Calculated energy use (maintenance+milk+body weight change) divided by dry matter intake was similar for the control and for the diet in which CMP replaced only concentrate, but it decreased linearly as increasing amounts of CMP replaced both forage and concentrate. A quadratic equation using the ratio of dietary starch to fNDF was the best predictor of milk fat percentage (ratios >1.4 were associated with reduced milk fat). Overall, CMP was effective at alleviating milk fat depression when it replaced corn grain but not when it replaced forage and concentrate.     

Lactation performance and digestibility of forages and diets in dairy cows fed a hemicellulose extract

Inclusion of hemicellulose extract (HE) in cattle diets have shown potential for improving fiber digestibility and production efficiency. The objective of this research was to evaluate production and digestibility effects of a HE on midlactation cows. Twelve multiparous Holstein cows (142 ± 44 d in milk, 685 ± 19 kg of body weight) including 4 with ruminal fistula were used in a 2 × 2 Latin square design with 21-d periods. Cows were fed a control (CON) diet containing 55% forage [dry matter (DM) basis, 2/3 corn silage and 1/3 alfalfa hay] or a similar diet where 1.0% of the diet DM was replaced with HE (TRT). Dry matter intake averaged 27.1 and 26.9 kg/d, for CON and TRT respectively, and was not affected by addition of extract. The percentage of milk protein (3.40 vs. 3.29%) was greater, whereas the percentage of milk fat (3.91 vs. 3.80%) tended to be greater, for cows fed the CON compared with the TRT diet. Because of numerically greater milk production (38.8 vs. 39.2 kg/d) for cows fed the TRT diet, no differences were observed in component yields other than lactose (1.86 vs. 1.94 kg/d), which tended to be greater for cows fed the TRT ration. Treatment improved neutral detergent fiber (NDF) digestibility (38.6 vs. 48.1%) for the TRT diet compared with the CON diet but did not affect apparent total-tract DM (67.8 vs. 68.5%), crude protein (67.2 vs. 67.9%), acid detergent fiber (ADF; 37.1 vs. 43.3%), or starch (92.8 vs. 92.2%) digestibility. For in situ determinations, Dacron bags containing corn silage, alfalfa hay, and either the CON or TRT ration were incubated in triplicate in the rumens of the cannulated cows at 0, 3, 6, 9, 12, 24, and 48 h on d 18 of each period. Each total mixed ration was incubated only in cows assigned to the corresponding diet. For corn silage, the rate of disappearance of NDF (1.70 vs. 4.27%) and ADF (1.79 vs. 4.66%) increased for cows fed the TRT diet. For alfalfa hay, the disappearance of fraction A of DM, NDF, and ADF decreased and fraction B of DM and NDF increased with treatment. The rate of disappearance for DM (8.03 vs. 11.04%), NDF (6.30 vs. 10.28%), and ADF (5.52 vs. 9.19%) increased for the alfalfa hay in rumens of treated cows. For the total mixed ration, the disappearance of the A fraction of NDF and ADF increased for cows fed the TRT diet. Supplementing diets of lactating dairy cows with an HE has beneficial effects on fiber degradation characteristics and provides opportunities for improving animal performance.     

Effects of forage source and amount of concentrate on rumen and intestinal digestion of nutrients in late-lactation cows

The objectives of this study were to determine the effects of dietary forage source with two concentrate concentrations on dry matter (DM) intake, rumen fill, ruminal and intestinal digestibility of nutrients, and duodenal N fractions in lactating cows. Four rumen and duodenal cannulated Holstein cows in late lactation were used in 4 x 4 Latin square design experiment with 21-d periods. Diets were 1) 65% first-cut alfalfa silage and 35% concentrate, 2) 50% alfalfa and 50% concentrate, 3) 65% bromegrass silage and 35% concentrate, and 4) 50% bromegrass and 50% concentrate. Dry matter intake was not affected by forage source but tended to be (P = 0.08) higher for cows fed diets with 50% concentrate. Rumen fill was greater (P < 0.01) for cows fed bromegrass compared with those fed alfalfa silage. Ruminal and intestinal digestion of DM was not affected by dietary forage source or concentrate level. Total N intake was greater for cows fed alfalfa-based diets, reflecting the higher crude protein content of alfalfa. However, total N flow at the duodenum was not affected by either forage source or concentrate in the diet. Although forage source influenced the site of digestion of some nutrients no significant effects on total tract digestibilities were observed.     

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

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

Effects of pea, barley, and alfalfa silage on ruminal nutrient degradability and performance of dairy cows

Six Holstein cows in early lactation were used in a double 3 x 3 Latin square design to determine the effects of feeding diets with pea silage, relative to barley silage, or alfalfa silage. Cows were fed rations formulated to contain 50:50 forage:concentrate ratio. Two ruminally fistulated cows were used in a randomized complete block design to determine ruminal nutrient degradability for pea silage relative to barley and alfalfa silages. Pea silage contained lower neutral detergent fiber (NDF), acid detergent fiber, and starch concentrations but higher crude protein than barley silage. Compared with alfalfa silage, pea silage had higher starch and NDF but lower crude protein content. Pea and alfalfa silage had similar effective ruminal degradability of dry matter, which was higher than that of barley silage. The rate of degradation and effective ruminal degradability of NDF was highest for alfalfa silage, intermediate for pea silage and lowest for barley silage. Results of the lactation trial showed that dry matter intake and milk yield were not affected by forage source. Milk composition was similar for cows fed pea or barley silage; however, cows fed pea silage produced milk with a higher fat and a lower protein percentage than those fed the alfalfa silage. Pea silage can replace barley or alfalfa silage as a forage source for dairy cows in early lactation.     

Influence of rumen fermentable neutral detergent fiber levels on feed intake and milk production of dairy cows.

Sixteen dairy cows in midlactation were fed four isonitrogenous (mean 2.46% N) mixed rations containing 46.4% DM and 40.7% NDF in a 16-wk Latin square design experiment. Diets were 42% barley-based concentrate, on a DM basis; forage was provided by combinations of two timothy silages of either slow (poor timothy) or rapid (good timothy) rumen fermentability and an alfalfa silage. Differences between the timothy forages caused the 24-h in sacco mixed diet NDF fermentability, determined in dry cows fed hay, to be 53.8, 56.0, 60.2, and 62.1% in the four diets formulated to rise from 0% [as a percentage of total timothy DM] to 33, 66, and 100% good timothy. Intake of DM and NDF were not influenced by forage source. Rumen pool sizes of OM and NDF were similarly unaffected by treatment. Milk production increased linearly as the proportion of rapidly fermentable NDF in the diet increased, although the increases were small and not statistically significant, whereas BW gain declined (nonsignificantly). As a result, total net energy output was not influenced by diet. Although cows appeared able to extract more energy than expected from the slower fermenting forage, increasing levels in the diet resulted in a shift in energy output from milk products to BW gain, supported by a shift in rumen fermentation end products from propionic to acetic acid. Results do not appear to support the concept that NDF quality influences and can be used to predict voluntary feed intake. There is no indication that cows responded to more rapidly fermentable dietary NDF by increasing feed intake or extent of NDF fermentation in the rumen.     

True absorption of calcium and phosphorus from alfalfa and corn silage when fed to lactating cows

A crossover experimental design with an extra period was used with four lactating cows (645 kg BW) and two diets to measure the true absorption of Ca and P from alfalfa hay and corn silage. True absorption was calculated after dosing cows intravenously with 45Ca and 32P to measure endogenous fecal losses. In alfalfa hay and alfalfa-corn silage diets, the Ca and P that came from the hay or hay and silage fraction was 94 and 98% and 63 and 84%, respectively. Cows ate more DM (22.7 vs. 20.6 kg/d) and produced more FCM (35.2 vs. 32.0 kg/d) when consuming alfalfa-corn silage compared with alfalfa hay. True absorption of Ca from alfalfa-corn silage was greater (42.2%) than from alfalfa hay (24.6%). Partial true absorption of Ca from alfalfa hay was 23.5% and from corn silage 51.5%. True P absorption for total diet was similar for both alfalfa hay (64.4%) and alfalfa-corn silage (74.6%). Partial true absorption of P from alfalfa hay (67.3%) was different from that from corn silage (80.0%). Fecal endogenous Ca excretion was nearly double the value (31 vs. 16 mg/kg BW) currently used by NRC. True absorption of Ca from alfalfa was lower and from corn silage was higher than currently used in NRC feeding standards. True absorption of P was higher than values currently used by NRC.     

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

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

Effects of feeding diets based on silage from corn hybrids that differed in concentration and in vitro digestibility of neutral detergent fiber to dairy cows

A dual-purpose hybrid and a hybrid selected for high neutral detergent fiber (NDF) concentration were harvested as corn silage. The dual-purpose silage (DPCS) had 42% NDF and 35.4% in vitro (30 h) NDF digestibility and the high fiber silage (HFCS) had 49% NDF and 40.1% in vitro NDF digestibility. Two diets (dry matter basis) had 45% DPCS or HFCS and 46% corn grain-based concentrate (dietary NDF was 29 and 32%, respectively), a third diet had 33% HFCS and 58% corn-based concentrate (27% dietary NDF), and a fourth diet had 33% DPCS and 58% concentrate that contained soybean hulls (32% dietary NDF). All diets contained 9% alfalfa silage. Diets were fed to eight midlactation Holstein cows in a 4 x 4 Latin square with 28 d periods. No differences among treatments were observed for milk yield (34.1 kg/d), dry matter intake (23.7 kg/d), and yield and concentration of milk protein. Cows fed the diet with 33% HFCS tended to have lower milk fat percentage than cows fed the 45% DPCS diet. Total digestible nutrients (measured using total collection) tended to be lower for the 33% DPCS diet than for the 45% DPCS diet. In vivo digestibility of NDF tended to be lower for the 33% HFCS diet than the 45% DPCS diet, but digestibility of starch in the two diets with HFCS was higher than the 45% DPCS diet. The lack of any substantial differences in responses suggest that the HFCS was equal to the DPCS when fed at 45% of the diet dry matter (53.5% total forage). When HFCS replaced DPCS so that NDF was similar between diets, milk fat percentage was reduced and ruminal propionate was increased. Increasing dietary NDF by adding soybean hulls to a diet based on DPCS reduced digestibility of dry matter, organic matter, and protein, and resulted in lower energy balance than the 45% DPCS diet.     

Effect of alfalfa forage preservation method and particle length on performance of dairy cows fed corn silage-based diets and tallow

A study was conducted to evaluate the effect of including alfalfa preserved either as silage or long-stem or chopped hay on DMI and milk fat production of dairy cows fed corn silage-based diets with supplemental tallow (T). Fifteen Holstein cows that averaged 117 DIM were used in a replicated 5 x 5 Latin square design with 21-d periods. Treatments (DM basis) were: 1) 50% corn silage:50% concentrate without T (CS); 2) 50% corn silage:50% concentrate with 2% T (CST); 3) 25% corn silage:25% short-cut alfalfa hay:50% concentrate with 2% T (SAHT); 4) 25% corn silage:25% long-cut alfalfa hay:50% concentrate with 2% T (LAHT); and 5) 25% corn silage:25% alfalfa silage:50% concentrate with 2% T (AST). Cows were allowed ad libitum consumption of a TMR fed 4 times daily. Diets averaged 16.4% CP and 30.3% NDF. Including 2% T in diets with corn silage as the sole forage source decreased DMI and milk fat percentage and yield. Replacing part of corn silage with alfalfa in diets with 2% T increased milk fat percentage and yield. The milk fat of cows fed CST was higher in trans-10 C18:1 than that of cows fed diets with alfalfa. No effect of alfalfa preservation method or hay particle length was observed on DMI and milk production. The milk fat percentage and yield were lower, and the proportion of trans-10 C18:1 in milk fat was higher for cows fed LAHT than for cows fed SAHT. Alfalfa preservation method had no effect on milk fat yield. Ruminal pH was higher for cows fed alfalfa in the diets, and it was higher for cows fed LAHT than SAHT. Feeding alfalfa silage or chopped hay appears to be more beneficial than long hay in sustaining milk fat production when 2% T is fed with diets high in corn silage. These results support the role of trans fatty acids in milk fat depression.     

Lactation performance of holstein cows fed fescue, orchardgrass, or alfalfa silage

Perennial grasses are increasingly being used as an integral part of nutrient management plans, but fescue (Festuca arundinacea Schreb.) is often overlooked because of perceived intake problems. A 30-d study was conducted to evaluate the lactation performance of cows fed a fescue silage-based total mixed ration (TMR) compared with orchardgrass (Dactylis glomerata L.) and alfalfa (Medicago sativa L.) silage-based TMR, when forages are harvested at recommended neutral detergent fiber (NDF) levels. Holstein cows (body weight [BW] = 627 +/- 66.0 kg, milk yield = 40.9 +/- 6.93 kg/d, parity = 2.6 +/- 1.44, days in milk = 152 +/- 24.5) were randomly assigned to treatment. Statistical design was a randomized complete block with 10 cows per treatment. The 5 treatments consisted of TMR using first-cutting alfalfa, and first- and second-cutting orchardgrass and tall fescue silage. Diets were formulated to provide 0.95% of BW as forage NDF and contained approximately 18% CP and 1.6 mcal/kg. This resulted in diets of about 30% NDF; for a 612-kg cow, approximately 5.8 kg/d of forage NDF was fed. Second-cutting, grass-based TMR had lower intake than alfalfa and first-cutting forage TMR. Cows consuming second-cutting orchardgrass had lower milk production than did cows consuming other forage TMR. Cows fed fescue TMR had higher milk production than those fed orchardgrass. Indigestible residues were higher, and NDF digestibilities were lower, in second-cutting forages vs. first-cutting forages, likely contributing to the differences observed in intake and resulting differences in milk production. Dairy cows consumed the first-cutting fescue TMR readily and performed as well as those on alfalfa or first-cutting, orchardgrass-based TMR in terms of lactation performance, but fescue and orchardgrass rations will require more concentrate in the ration than alfalfa.     

Effects of pretrial milk yield on responses of feed intake,digestion, and production to dietary forage concentration

The relationships between pretrial milk yield and effects of dietary forage-to-concentrate ratio on dry matter intake (DMI), digestion, and milk yield were evaluated using 32 Holstein cows in a crossover design with two 16-d periods. Cows were 197 +/- 55 (mean +/- SD) days in milk at the beginning of the experiment. Milk yield averaged 33.9 kg/d and ranged from 16.5 to 55.0 kg/d for the 4 d before initiation of treatments. Treatments were diets with forage-to-concentrate ratios of 67:33 and 44:56. Forages were alfalfa silage and corn silage, each at 50% of forage dry matter (DM). Neutral detergent fiber (NDF) concentrations of high-forage and low-forage diets were 30.7 and 24.3% of DM, respectively. Dry matter intake was 1.7 kg/d higher for cows fed the low-forage diet. Milk yield was 2.3 kg/d greater on low forage than on high forage, but 3.5% fat-corrected milk yield and yield of milk fat were not different between treatments. Individual DMI response to the low-forage diet relative to the high-forage diet (low-high) was positively and linearly related to pretrial fat-corrected milk yield, but fat-corrected milk yield response demonstrated a quadratic relationship with pretrial fat-corrected milk yield. Milk yield responded more positively to low forage among low- and high-producing cows than among moderate-producing cows. Energy partitioned to body reserves and to milk, and passage rate of indigestible NDF, also responded to dietary forage level in quadratic relationships with pretrial milk energy output. Individual responses of intake, production, and fiber digestion to a change in forage-to-concentrate ratio were dependent on production level.     

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.     

Effects of alfalfa hay of varying fiber fed at 35 or 50% of diet on lactation and nutrient utilization by dairy cows.

Five alfalfa hays (four from Arizona and one from California), varying in percentages of ADF (26, 28, 32, and 38%), were fed to 40 lactating Holstein cows averaging 90 DIM. Cows were in 10 groups of 4 cows each; groups were based on 14-d pretreatment milk yield. Each hay was included in TMR to provide 50 or 35% of DM. Diets were fed for ad libitum intake for 70 d. Feeding behavior of 2 cows per treatment was electronically monitored for 14 d. Total tract digestibilities of DM, ADF, and NDF were determined using Cr2O3, and ruminal in situ loss of DM, ADF, and NDF of hays was estimated using 4 cows fitted with ruminal fistulas. Dry matter intake, 3.5% FCM, changes in BW, rectal temperatures, and milk composition (except milk fat) were not affected by ADF in hays or concentrate percentage. However, milk yield decreased as ADF in hay increased, particularly at 50% concentrate. At 50% concentrate, milk yield of cows fed hays of 26 to 28% ADF averaged 30.7 kg/d, and the mean for cows fed 32 and 38% ADF hays was 27.6 kg/d. Milk fat percentages tended to be lower on higher concentrate. Eating time was longer as hay ADF increased and tended to decrease on high concentrate, but there were no significant effects of treatment on number or length of meals. In situ disappearance of DM, ADF, and NDF decreased as hay ADF increased, but total tract digestibilities of ADF and NDF were greater in hay of higher fiber content, particularly in cows fed 35% hay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of starch source and level of forage neutral detergent fiber on performance by dairy cows

The effectiveness of neutral detergent fiber (NDF) from soyhulls and whole cottonseed for replacing NDF from forage was evaluated in a lactation trial during wk 10 to 25 of lactation. Forty-eight cows were blocked and randomly assigned within a block to one of four diets: 1) 21% forage NDF with corn 2) 16% forage NDF with corn, 3) 16% forage NDF with corn and wheat (1:1) and, 4) 11% forage NDF with cottonseed and corn. Soybean hulls were added at approximately 23.0% of dry matter (DM) for the 16 and 11% forage NDF diets to replace forage and formulate diets with 35% nonfiber carbohydrates. Actual forage NDF concentration were 17.8, 14.0, 13.9, and 9.4%, respectively. Dry matter intake and milk yield were highest for cows fed 11% forage NDF with cottonseed. Milk fat percentage was higher for cows consuming 21% forage NDF and 16% forage NDF with corn than for cows fed the two other diets. Cows fed 16% forage NDF with corn and wheat experienced milk fat-protein inversion, but ruminal acetate:propionate was lower for cows fed 11% forage NDF than cows fed 16% forage NDF. Body weight (BW) and BW change were not different among treatments. Time spent chewing was similar among all diets. For cows in midlactation, forage NDF may be reduced to 9 to 11% when cottonseed is at 11% of DM and dietary nonstructural carbohydrates are at 30% of DM. Forage NDF may be reduced to 14 to 16% without cottonseed when nonstructural carbohydrates are at 30% of DM.     

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.