Predicting the effect of proteolysis on ruminal crude protein degradation of legume and grass silages using near-infrared reflectance spectroscopy

Two studies were conducted to assess whether routine applications of near infrared reflectance spectroscopy could predict the effects of silage proteolysis on ruminal crude protein (CP) degradation of legume and grass silages. A preliminary study was conducted to assess the effect of laboratory drying method on ruminal CP degradation of silages. Thirty legume and grass silages were freeze-, oven-, or microwave-dried and incubated in situ in the ventral rumen of three ruminally cannulated cows for 24 h. Freeze-drying was considered least likely to alter ruminal CP degradation of the silages; therefore, oven- and microwave-drying were compared using first-order regression with freeze-drying. Oven-drying for 48 h at 55 degrees C compared favorably (R2 = 0.84) with freeze-drying. Microwave-drying resulted in a large bias (2.84 g/10(-1) kg of CP) and was poorly related (R2 = 0.48) to freeze-drying. In a second study, alfalfa and timothy were cut at three maturities and allowed to wilt for 0, 10, 24, 32, 48, and 54 h. Forages were ensiled in triplicate cylindrical mini silos and allowed to ferment for 120 d. After fermentation, silages were oven-dried, ground, and scanned on a near-infrared reflectance spectrophotometer. Duplicate, dried, 2-mm ground silage samples were incubated in the ventral rumen of three ruminally cannulated cows for 24 h. Forage species, maturity, and wilting time significantly affected 24-h ruminal CP degradation of the silages. Near-infrared reflectance spectroscopy accurately predicted (R2 = 0.91) 24-h ruminal CP degradation of silages. Data suggest near-infrared reflectance spectroscopy can accurately assess the effects of forage species, maturity, and wilting time (proteolysis) on 24-h ruminal CP degradation of legume and grass silages.     

Prediction of laboratory and in situ protein fractions in legume and grass silages using near-infrared reflectance spectroscopy

Legume and grass silage samples (n = 121) were collected from commercial forage testing laboratories (trial 1). Samples were dried at 55 degrees C for 48 h, ground, scanned on a near-infrared reflectance spectrophotometer, and analyzed for crude protein (CP), soluble CP, acid detergent fiber (ADF) CP, and neutral detergent fiber (NDF) CP by wet chemistry methods. Sixty samples were selected for calibration development, and the remaining samples were used for equation validation. Near-infrared reflectance spectroscopy accurately predicted the CP content of the silages (R2 = 0.96), but prediction of soluble CP, ADF CP, and NDF CP was markedly less accurate. The coefficients of determination and standard errors of calibration for CP, ADF CP, NDF CP (percentage of DM), and soluble CP (percentage of CP) were as follows (0.96 and 0.80, 0.77 and 0.24, 0.72 and 0.71, and 0.82 and 4.40). In a second study, legume and grass silage samples (n = 32) were dried at 55 degrees C and ground (2 mm). Duplicate dacron bags containing 5 g of silage were incubated in the ventral rumen of three ruminally cannulated cows for 0, 3, 6, 12, 24, 48, and 72 h. In situ protein fractions, including rapidly degraded protein, slowly degraded protein, undegradable protein, degradation rate, and rumen-undegradable protein, were determined. Original samples were reground (1 mm) and scanned. Previously defined near-infrared spectroscopy calibration procedures were conducted. Coefficients of determination for in situ CP fractions were R2 > 0.92 with the exception of degradation rate (R2 = 0.87). Data suggest that in situ protein fractions are better predicted by near-infrared reflectance spectroscopy than by laboratory protein fractions.     

Short communication: a novel system to estimate protein degradability in legume and grass hays

Previous research from our laboratory has demonstrated that near-infrared reflectance spectroscopy has utility in predicting rumen-undegradable protein (RUP) contents of legume and grass silages. This study was conducted to evaluate whether application of previous research techniques could yield a useful near-infrared reflectance spectroscopy RUP prediction system for legume and grass hays. Legume and grass hays (n = 106) were evaluated for RUP content by in situ techniques in four ruminally cannulated cows. In situ RUP for legume and grass hays averaged 25.9% CP and ranged from 14.6 to 45.5% CP, respectively. We developed a near-infrared reflectance spectroscopy RUP calibration equation for the legume and grass hay data set using in situ RUP contents as base data. This procedure resulted in an acceptable (R2 = 0.87, SE = 2.46% CP) near-infrared reflectance spectroscopy equation to predict RUP content of legume and grass hays. Data suggest that near-infrared spectroscopy predicts RUP contents of legume and grass hays with accuracies similar to legume and grass silages.     

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

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

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

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

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

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

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.     

Performance of lactating dairy cows fed alfalfa or red clover silage as the sole forage

Three Latin square trials, with 20 (two trials) or 24 (one trial) multiparous lactating Holstein cows (four in each trial with ruminal cannulae), compared the feeding value of red clover and alfalfa silages harvested over 3 yr. Overall, the forages contained similar amounts of neutral detergent fiber and acid detergent fiber; however, red clover silage contained more hemicellulose, less ash and crude protein (CP), and only 67% as much nonprotein N, as a proportion of total N, as did alfalfa silage. Diets were formulated with equal dry matter (DM) from alfalfa or red clover silage and contained on average 65% forage, 33 or 30% ground high moisture ear corn, and 0 or 3% low soluble fishmeal (DM basis). Diets fed in the Latin squares contained (mean dietary CP): 1) alfalfa (17.8% CP); 2) red clover (15.1% CP); 3) alfalfa plus fishmeal (19.6% CP); and 4) red clover plus fishmeal (16.9% CP). Although performance varied somewhat among trials, overall statistical analysis showed that replacing alfalfa with red clover reduced yields of milk, fat-corrected milk, fat, protein, lactose, and SNF; these effects were related to the 1.2 kg/d lower DM intake for cows fed red clover. Replacing alfalfa with red clover improved body weight gain and reduced concentrations of milk and blood urea and ruminal NH3. Apparent digestibility of DM, organic matter, neutral detergent fiber, acid detergent fiber, and hemicellulose all were greater when red clover was fed. There were no significant forage x fishmeal interactions for DM intake and yield of milk and milk components, indicating that supplementation with rumen undegradable protein gave similar increases in production on both forages. Net energy of lactation (NE(L)), estimated from maintenance, mean milk yield, and body weight change, in alfalfa and red clover silage were, respectively, 1.25 and 1.38 Mcal NE(L)/kg of DM, indicating 10% greater NE(L) in red clover.     

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.     

Effect of feeding protein supplements of differing degradability on omasal flow of microbial and undegraded protein

Ten ruminally cannulated lactating Holstein cows that were part of a larger trial studying the effects of feeding different proteins on milk production were used in a replicated 5 x 5 Latin square to quantify flows of microbial and rumen-undegradable protein (RUP) in omasal digesta. Cows were fed total mixed rations containing (dry matter basis) 44% corn silage, 22% alfalfa silage, 2% urea, and 31% concentrate. The basal diet contained 31% high-moisture corn; equal N from one of four protein supplements was added to the other diets at the expense of corn: 9% solvent soybean meal (SSBM), 10% expeller soybean meal (ESBM), 5.5% blood meal (BM), and 7% corn gluten meal (CGM). Omasal sampling was used to quantify total AA N (TAAN) and nonammonia N (NAN) flows from the rumen. Estimates of RUP were made from differences between total and microbial N flows, including a correction for RUP in the basal diet. Modifying a spectrophotometric assay improved total purine recovery from isolated bacteria and omasal samples and gave estimates of microbial TAAN and NAN flows that were similar to a standard HPLC method. Linear programming, based on AA patterns of the diet and isolated omasal bacteria and ruminal protozoa, appeared to overestimate microbial TAAN and NAN flows compared to the purine assays. Yields of microbial TAAN and NAN determined using any method was not affected by diet and averaged 32 to 35 g NAN per kilogram of organic matter truly digested in the rumen. On average, National Research Council (NRC) equations underpredicted microbial N flows by 152 g/d (vs. HPLC), 168 g/d (vs. spectrophotometry), and 244 g/d (vs. linear programming). Estimates of RUP (means from the HPLC and spectrophotometric methods) were: SSBM, 27%, ESBM, 45%, BM, 60%, and CGM, 73%. Except for CGM, RUP values averaged about 20 percentage units lower than those reported by the NRC.     

Diets deficient in rumen undegraded protein did not depress milk production

The objective of this study was to evaluate the National Research Council's recommendations for feeding levels of rumen undegraded protein (RUP) for cows fed a one-group total mixed ration. Sixty Holstein cows were paired by parity (1 to 6) and DIM (23 to 315) and were randomly assigned to one of two treatment sequences. Diets contained alfalfa silage (30% diet DM) and corn silage (26% diet DM), and were isonitrogenous (16% CP) and isocaloric (1.71 Mcal/kg). Soybean meal, protected soybean meal (Soy Best), and urea were used to make ration protein fractions that were predicted to be 35 or 29% RUP. The 35% RUP diet was formulated to provide 98 and 105% of the average requirement for RUP and rumen degraded protein (RDP), respectively. The ration containing 29% RUP provided 79 and 117% of average required RUP and RDP, respectively. All cows were group-fed the high RUP diet during a 2-wk pretreatment period, and then were fed one ration for 4 wk followed by the other for 4 wk according to their assigned treatment sequence. Data were collected in the last wk of each period. Mean milk production, milk fat, and milk protein were 32.6 kg/d, 4.35%, and 3.36%, respectively, with no treatment differences. Treatment response was not affected by degree of predicted RUP deficiency. National Research Council requirements for RUP may be too high for cows fed diets similar in energy to a one-group total mixed ration. Alternatively, estimates of RUP content of feedstuffs may be low.     

Effect of formic acid or formaldehyde treatment of alfalfa silage on nutrient utilization by dairy cows.

Third-cutting alfalfa with 37% DM was ensiled untreated or treated with either 2.8 g of formic acid/100 g of DM or .31 g of formaldehyde/100 g of DM and fed to lactating dairy cows in two experiments. Silage treated with formic acid had the lowest pH and concentrations of NPN, NH3, and total free AA. Both treatments decreased rumen in vitro protein degradability but did not affect in vitro rumen plus pepsin digestibility. In trial 1, part 1, 22 Holstein cows received a standard diet for 18 d postpartum and then were fed for 6 wk one of three diets containing 98% alfalfa silage DM. Although DMI was comparable, yields of milk, SCM, fat, protein, lactose, and SNF were higher when treated silages were fed. Plasma concentrations of branched-chain, essential, and total AA increased when formic acid-treated silage was fed. Rumen pH and concentrations of NH3 and VFA were similar for all diets. Rumen escape protein, estimated using 15N as a microbial protein marker, was increased more by formic acid than by formaldehyde treatment. In trial 1, part 2, supplementation with 4.8% fish meal increased concentration of milk protein and yields of milk, protein, lactose, and SNF. Milk urea concentration was higher on the untreated silage diet. Total tract apparent DM and N digestibilities were not affected by silage treatment, although fish meal decreased apparent DM digestibility. In trial 2, 80:20 alfalfa silage:ground corn diets were fed to 12 midlactation cows in a 3 x 3 Latin square study. Milk production was unaffected, but milk protein concentration and DMI were higher when treated silages were fed. Feeding treated silages increased plasma concentrations of branched-chain AA, essential AA, and total AA. Formaldehyde and especially formic acid treatment effectively improved utilization of nutrients in alfalfa silage by lactating dairy cows.     

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.     

Effect of low level monensin supplementation on the production of dairy cows fed alfalfa silage

Effectiveness of low level monensin supplementation on N utilization in lactating dairy cows fed alfalfa silage was assessed using 48 multiparous Holsteins. Cows were fed a covariate diet [% of dry matter (DM): 56% alfalfa silage, 39% ground high moisture corn, 3% soybean meal, 1% ground corn, 1% vitamin-mineral supplements] for 2 wk, then grouped by days in milk into blocks of 4. Cows were randomly assigned within blocks to 1 of 4 diets that were fed for 10 wk: 1) control (covariate diet), 2) control plus 3% fish meal (replacing DM from high moisture corn), 3) monensin (10 mg/kg DM), and 4) monensin plus 3% fish meal. Diets 1 and 3 averaged 16.7% crude protein (25% from free AA in alfalfa silage); diets 2 and 4 averaged 18.5% crude protein. Monensin intake averaged 16 mg/d on diets 1 and 2 (due to contamination) and 248 mg/d on diets 3 and 4. There was no effect of fish meal or monensin on DM intake. However, weight gain and yield of milk, protein, and SNF increased with fish meal feeding, indicating metabolizable protein limited production. Feeding monensin increased blood glucose but reduced yield of 3.5% fat-corrected milk, milk fat content and yield, and milk protein content and yield. Apparent N efficiency was greatest on monensin (diet 3) but lowest on monensin plus fish meal (diet 4). Fish meal reduced blood glucose concentration and apparent N efficiency, and increased concentrations of milk and blood urea. Monensin increased ruminal propionate concentration and decreased concentration of acetate and butyrate and acetate:propionate in ruminally cannulated cows fed the experimental diets. However, these changes were small, suggesting that too little monensin was fed. Fish meal reduced ruminal total amino acid (AA) but monensin did not alter ruminal NH(3) or total AA. Both fish meal and monensin increased NH(3) formation from casein AA using ruminal inoculum from the cannulated cows. There was no evidence from this trial that feeding 250 mg of monensin per day to lactating cows improved N utilization by reducing ruminal catabolism of the large amounts of free AA in alfalfa silage.     

Short communication: effect of tannic acid on composition and ruminal degradability of bermudagrass and alfalfa silages

We measured the effects of the addition of tannic acid on chemical composition and crude protein (CP) ruminal degradability of bermudagrass, cv. coast cross (Cynodon dactylon L.) and alfalfa (Medicago sativa L.) silages with nylon bags incubated in the rumen of two fistulated lactating cows. Silage pH was greater for alfalfa than for bermudagrass. The addition of tannic acid had no effect on silage pH. Ammonia N was greater in alfalfa than in bermudagrass silage. Treated and control silages had similar ammonia N concentrations. The percentage of CP that was solubilized at time 0 was lower for alfalfa than for bermudagrass silage. The addition of tannic acid decreased the portion of CP solubilized at time 0 and increased the potentially degradable fraction of CP. The potentially degradable fraction of CP was greater for alfalfa than for bermudagrass. There was an interaction of species and treatment; the disappearance rate of CP increased with tannic acid treatment of alfalfa but decreased with acid treatment of bermudagrass. The effective degradability of CP was similar for control and treated alfalfa but lower for treated than for control bermudagrass. Tannic acid treatment is effective in decreasing the rapidly soluble fraction of alfalfa and bermudagrass silages, which could be beneficial to the animal because it would decrease the excess of N in the rumen after feeding. Tannic acid treatment decreased CP degradability of bermudagrass silage but had no effect on alfalfa silage, suggesting that tannic acid concentration required to effectively decrease CP degradability differs among forages.     

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.     

Effects of feeding formate-treated alfalfa silage or red clover silage on the production of lactating dairy cows

In trial 1, 15 Holsteins were fed 3 total mixed rations (TMR) with 33% neutral detergent fiber in 3 × 3 Latin squares (28-d periods). Two TMR contained (dry matter basis): 40% control alfalfa silage (CAS) or 40% ammonium tetraformate-treated alfalfa silage (TAS), 20% corn silage (CS), 33% high-moisture shelled corn (HMSC), 6% solvent soybean meal (SSBM), and 18% crude protein (CP); the third TMR contained 54% red clover silage (RCS), 6% dried molasses, 33% HMSC, 6% SSBM, and 16.3% CP. Silages differed in nonprotein N (NPN) and acid detergent insoluble N (ADIN; % of total N): 50 and 4% (CAS); 45 and 3% (TAS); 27 and 8% (RCS). Replacing CAS with TAS increased intake, yields of milk, fat-corrected milk, protein, and solids-not-fat, and apparent dry matter and N efficiency. Replacing CAS with RCS increased intake and N efficiency but not milk yield. Replacing CAS or TAS with RCS lowered milk urea N, increased apparent nutrient digestibility, and diverted N excretion from urine to feces. In trial 2, 24 Holsteins (8 ruminally cannulated) were fed 4 TMR in 4 × 4 Latin squares (28-d periods). Diets included the CAS, TAS, and RCS (RCS1) fed in trial 1 plus an immature RCS (RCS2; 29% NPN, 4% ADIN). The CAS, TAS, and RCS2 diets contained 36% HMSC and 3% SSBM and the RCS1 diet contained 31% HMSC and 9% SSBM. All TMR had 50% legume silage, 10% CS, 27% neutral detergent fiber, and 17 to 18% CP. Little difference was observed between cows fed CAS and TAS. Intakes of DM and yields of milk, fat-corrected milk, fat, protein, lactose, and solids-not-fat, and milk fat and protein content were greater on alfalfa silage vs. RCS. Blood urea N, milk urea N, ruminal ammonia, and total urinary N excretion were reduced on RCS, suggesting better N utilization on the lower NPN silage. Apparent N efficiency tended to be higher for cows fed RCS but there was no difference when N efficiency was expressed as kilograms of milk yield per kilogram of total N excreted.     

Effect of dietary protein concentration and degradability on response to rumen-protected methionine in lactating dairy cows

An incomplete 8 × 8 Latin square trial (4-wk periods; 12 wk total) using 32 multiparous and 16 primiparous Holstein cows was conducted to assess the production response to crude protein (CP), digestible rumen-undegraded protein (RUP), and rumen-protected Met (RPM; fed as Mepron; Degussa Corp., Kennesaw, GA). Diets contained [dry matter (DM) basis] 21% alfalfa silage, 34% corn silage, 22 to 26% high-moisture corn, 10 to 14% soybean meal, 4% soyhulls, 2% added fat, 1.3% minerals and vitamins, and 27 to 28% neutral detergent fiber. Treatments were a 2 × 2 × 2 factorial arrangement of the following main effects: 15.8 or 17.1% dietary CP, with or without supplemental rumen-undegraded protein (RUP) from expeller soybean meal, and 0 or 9 g of RPM/d. None of the 2- or 3-way interactions was significant. Higher dietary CP increased DM intake 1.1 kg/d and yield of milk 1.7 kg/d, 3.5% fat-corrected milk (FCM) 2.2 kg/d, fat 0.10 kg/d, and true protein 0.05 kg/d, and improved apparent N balance and DM and fiber digestibility. However, milk urea N and estimated urinary excretion of urea-N and total-N also increased, and apparent N efficiency (milk-N/N-intake) fell from 33 to 30% when cows consumed higher dietary CP. Positive effects of feeding more RUP were increased feed efficiency and milk fat content plus 1.8 kg/d greater FCM and 0.08 kg/d greater fat, but milk protein content was lower and milk urea N and urinary urea excretion were elevated. Supplementation with RPM increased DM intake 0.7 kg/d and FCM and fat yield by 1.4 and 0.06 kg/d, and tended to increase milk fat content and yield of milk and protein.     

Effect of mechanical processing and fat removal on the nutritive value of cottonseed for lactating dairy cows.

In experiment 1, 24 midlactation, multiparous Holstein cows were used in six 4 x 4 Latin squares to evaluate extruded-expelled cottonseed (EEC) as a source of ruminally undegradable protein (RUP). Diets were formulated to contain: 16% crude protein (CP), 35% RUP (SBM16); 18% CP, 35% RUP (SBM18); 16% CP, 40% RUP using EEC (EC16); and 16% CP, 40% RUP using a fishmeal-blood meal blend (FBM16). Milk yields (37.2 kg/d) and percentages of milk fat, protein, casein, and SNF were similar across diets. Cows fed FBM16 consumed less dry matter (DM) (28.0 kg/d) than those consuming other diets (29.4 kg/d). In experiment 2, 18 midlactation, multiparous Holstein cows were used in six 3 x 3 Latin squares to determine the value of EEC as a replacement for whole cottonseed in lactating cow diets. Diets contained whole cottonseed (CS), EEC plus tallow (ECT), or EEC (EC). Diets were formulated to be similar in energy, N, and RUP. Milk yields (35.5 kg/d), DM intake (27.0 kg/d), and milk fat percent were similar across diets. Percentages of milk protein and SNF were higher for EC than CS or ECT. These production data suggest that EEC can replace whole cottonseed in isocaloric diets and can be partially substituted for soybean meal or a fishmeal-blood meal blend without affecting lactational performance. In situ ruminal degradation and in vitro ammonia N release indicate that processing of EEC was inadequate to protect the protein from ruminal degradation and EEC would not be a source of RUP.     

Water partitioning and intake prediction in dry and lactating Holstein cows.

Data from four energy and N balance trials with lactating Holstein cows (n = 329) and one trial with dry cows (n = 60) were used to predict free water intake and water-related traits. Lactating cows were between 36 and 159 DIM and, individually, were allowed ad libitum water and forage (corn silage without or with wilted haycrop silage) plus concentrates; dry cows accessed ad libitum water and single forages (grass, clover, or alfalfa, as hays or as wilted silages, or corn silage) varying in maturity. Intake of DM per day and dietary DM percentage were significant and positively related predictors of free water intake in dry and lactating cows. Daily milk yield (range 16 to 52 kg/d) was related linearly to water consumption (.60 L/kg of milk), and season effect in lactating cows was curvilinear; peak water intake was in late June and nadir in late December. Ration CP percentage (DM basis) affected free water intake only in dry cows; 1 unit of increase resulted in an increase of about 1 kg/d in water intake between 12 and 13% CP. As ration moisture dropped from 70 to 40%, free water intake increased about 7 L/d in dry cows, but this was accompanied by a drop of 15 L/d in total water intake (free plus feed water). Free water intakes were predicted with R2 of .64 and .69 in dry and lactating Holstein cows, respectively. Fecal water and urine outputs also were predicted. We found no significant relationship between DM content of the diet and the resulting ad libitum intake in either dry or lactating cows.