Varying dietary fiber for lactating cows fed corn and barley silages

Seventy-five lactating cows were in three experiments to determine the effect of dietary fiber content on ration intake, milk and milk fat production, ration digestibility, nitrogen utilization, and ruminal volatile fatty acids. With corn or barley silage as the source of forage, four treatment groups consumed rations averaging 11.8, 14.5, 17.5, and 20.6% crude fiber and 14.3, 17.5, 20.0, and 23.9% acid detergent fiber dry basis. Fiber intake was controlled by the amount and fiber content of concentrate offered or by silages with different grain content. With corn silage, dry matter intake was not altered by dietary fiber, but dry matter intake was lower when additional fiber was fed with barlev silage. Linear regressions best described effects of dietary fiber on milk production and milk fat content. Milk production declined .39 and .36 kg and milk fat test increased .072 and .067% for each percentage increase in crude and acid detergent fiber. Ration digestibility, determined by lignin ratio, was less for barley silage than corn silage. Narrowing acetate: propionate ratios were evident when dietary fiber was lowered. From these experiments with silage based rations, either crude or acid-detergent fiber content of forage adequately describes feeds to serve as a basis for practically balancing rations for lactating cows.     

Sorghum forage in precision-fed dairy heifer diets

Sorghum forage is an alternative crop that is more adapted to drier conditions and more resistant than corn to drought conditions. Thus, sorghum forage maximizes water utilization. The objective of this study was to evaluate sorghum silage (SS), including digestibility and fermentation parameters, in precision-fed dairy heifers. Eight Holstein heifers (13.7 ± 0.6 mo of age and 364.8 ± 17.64 kg of body weight) fitted with rumen cannulas were used in a replicated 4 × 4 Latin Square design; treatments were 4 levels of forage to concentrate ratios (85:15, 75:25, 65:35, and 55:45). Rumen contents were sampled at various times to determine pH and volatile fatty acid concentrations. Dry matter (DM) and neutral detergent fiber (NDF) in situ degradation kinetics were compared between SS and corn silage (CS) diets. Fecal total collection was used to estimate apparent total-tract digestibility. Fecal grab samples at 0, 6, 12, and 18 h after feeding were used to estimate total-tract starch digestibility. Amount of concentrate in the diet affected the time that heifers spent eating as well as rumen pH. When the concentrate proportion of the diet increased, eating time and rumen pH decreased linearly. Total volatile fatty acid concentrations were not affected by treatment, but butyrate increased as the proportion of concentrate increased in the diet. Digestibility of DM and starch were higher in diets with lower forage to concentrate ratio, but NDF, acid detergent fiber, and hemicellulose digestibility were not affected. Corn silage had greater DM and NDF digestibility than SS. Also, fractional rate of digestion was faster for CS than SS (2.78 vs. 2.42% per hour, respectively). We conclude that fecal grab samples are suitable for predicting starch digestibility in heifers given the starch levels studied. In addition, SS was an adequate alternative forage in precision-fed dairy heifers with outcomes very similar to CS-based rations.     

Alfalfa Silage or Hay Versus Corn Silage as the Sole Forage for Lactating Dairy Cows

In Trial 1, three rations were fed to 21 cows in a 3 × 3 Latin square: 60% alfalfa silage, 60% corn silage, and 79% corn silage (dry matter basis) with the balance from corn and soybean meal. Acid detergent fiber measures indicated alfalfa and corn silage were of excellent quality. Milk production was similar on 60% forage rations but lower on 79% corn silage. Milk fat was reduced on 60% corn silage. In Trial 2, four rations were fed to 16 cows in a 4 × 4 Latin square: 63% alfalfa silage, 60% alfalfa hay, 60% corn silage, and 76% corn silage. Alfalfa forages were higher in acid detergent fiber but corn silage was similar to Trial 1. Dry matter digestibility was highest on 60% corn silage, intermediate on 63% alfalfa silage and 76% corn silage, and lowest on 60% alfalfa hay. Milk production was similar on the diets containing 60 and 63% forage and lower on 76% corn silage. Milk protein concentration was reduced on the alfalfa diets. Highest protein secretion and feed conversion was supported by 60% corn silage. In both trials, potentially digestible neutral detergent fiber from alfalfa was more digestible than that from corn silage, and concentrations of urea in milk and blood were highly correlated. Results indicate high quality alfalfa silage is comparable to corn silage for milk production.     

Intake,Digestibility, and Rate of Passage of Silages and Hays from Wet Fractionation of Alfalfa

Fibrous products of alfalfa from various steps of the wet fractionation process were either ensiled or dried artificially. Two 4 × 4 Latin square digestion trials for silages and hays were to determine the effect of cell maceration and pressure fractionation on characteristics and acceptability of these products by ruminants.Silage treatments consisted of field wilted, chopped, and ensiled; direct cut and cell macerated; direct cut, cell macerated, and pressed; and repressed silage. Dry matter intake averaged 971, 914, 796, and 763 g/day, respectively. Digestion coefficients were: dry matter 60.1, 56.0, 55.6, and 54.3; cell wall constituents 49.8, 49.4, 49.9, and 50.8 for the treatments. Hay treatments were processed in the same manner as were silages but artificially dried. Dry matter intake averaged 1021, 990, 1025, and 980 g/day; digestibility of cell wall constituents was 44.6, 46.5, 51.4, and 52.7%; total mean retention time was 31.5, 41.8, 45.8, and 46.6 h for the hay treatments. When the fibrous residues were handled as hay, digestibility of fiber components was increased by cell maceration and pressure fractionation, while intake was maintained.     

Effect of forage to concentrate ratio with sorghum silage as a source of forage on rumen fermentation,N balance,and purine derivative excretion in limit-fed dairy heifers

Sorghum silage has been shown to be a good alternative to corn silage for dairy cows; however, studies regarding heifers are insufficiently explored. Therefore, the objective of this study was to evaluate effects of changing forage to concentrate ratio (FOR:CON) in diets based on sorghum silage on N digestibility, rumen fermentation, N balance, C excretion, and microbial N yield in limit-fed dairy heifers. A split-plot 4 × 4 Latin square design with 19-d periods (15 d of adaptation and 4 d of sampling) was conducted with 8 rumen cannulated dairy heifers (age 13.7 ± 0.6 mo and weight 364.8 ± 17.6 kg). Heifers were fed sorghum silage–based diets with 4 FOR:CON (85:15, 75:25, 65:35, and 55:45) balanced for similar metabolizable energy intake per unit of body weight and crude protein concentration. Diets were fed to allow 900 to 1,000 g/d body weight gain and were fed once daily. Total collection of feces and urine was completed on d 15 to 19 to determine N, C, urea N, allantoin, uric acid, and creatinine excretion. Rumen contents were sampled on d 19 at 0, 1.5, 3, 4.5, 6, 9, 13, 17, 21, and 23 h after feeding to measure pH, volatile fatty acid (VFA), ammonia-N, and free AA concentrations. The pH decreased linearly while ammonia-N and free AA levels increased linearly with decreasing FOR:CON of diets. Although mean total VFA did not differ among treatment diets, molar proportions of VFA did. Acetate proportion decreased while propionate and butyrate increased with decreasing FOR:CON. Intake of N and urea N excretion decreased with decreasing forage proportion in diets while total N excretion, apparent N digestibility, and N retention were not different. Intake of C and excretion in feces (g/d) decreased linearly with decreasing FOR:CON in diets. Creatinine, allantoin, and uric acid excretion were not affected by FOR:CON; however, microbial N yield tended to increase linearly with greater concentrate in diets. Heifers limit fed diets based on sorghum silage demonstrated the effect of available ammonia-N and readily fermentable carbohydrates with subsequent effects on nutrient utilization when different FOR:CON were applied. Based on the presented results, FOR:CON 65:35 had the most suitable balance of available ammonia-N and readily fermentable carbohydrates for the most optimal results.     

The effect of supplemental concentrate fed during the dry period on morphological and functional aspects of rumen adaptation in dairy cattle during the dry period and early lactation

Ten rumen-cannulated Holstein-Friesian cows were used to examine the effect of feeding supplemental concentrate during the dry period on rumen papillae morphology and fractional absorption rate (k_a) of volatile fatty acids (VFA) during the dry period and subsequent lactation. Treatment consisted of supplemental concentrate [3.0 kg of dry matter (DM)/d] from 28 d antepartum (ap) until the day of calving, whereas control did not receive supplemental concentrate. Cows were fed for ad libitum intake and had free access to the dry period ration (27% grass silage, 28% corn silage, 35% wheat straw, and 11% soybean meal on a DM basis) and, from calving onward, to a basal lactation ration (42% grass silage, 42% corn silage, and 16% soybean meal on a DM basis). From 1 to 3 d postpartum (pp), all cows were fed 0.9 kg DM/d of concentrate, which increased linearly thereafter to 8.9 kg of DM/d on d 11 pp. At 28, 18, and 8 d ap, and 3, 17, 31, and 45 d pp, rumen papillae were collected and k_aVFA was measured in all cows. On average, 13.8 (standard deviation: 3.8) papillae were collected each from the ventral, caudodorsal, and caudoventral rumen sacs per cow per day. The k_aVFA was measured by incubating a standardized buffer fluid (45 L), containing 120 mM VFA (60% acetic, 25% propionic, and 15% butyric acid) and Co-EDTA as fluid passage marker, in the evacuated and washed rumen. Treatment did not affect ap or pp DM and energy intakes or milk yield and composition. Treatment increased papillae surface area, which was 19 and 29% larger at 18 and 8 d ap compared with 28 d ap, respectively. Surface area increased, mainly due to an increase in papillae width. However, treatment did not increase k_aVFA at 18 and 8 d ap compared with 28 d ap. In the control group, no changes in papillae surface area or k_aVFA were observed during the dry period. In the treatment group, papillae surface area decreased between 8 d ap and 3 d pp, whereas no decrease was observed for control. From 3 to 45 d pp, papillae surface area and k_aVFA increased for all cows by approximately 50%, but the ap concentrate treatment did not affect k_aVFA pp. In conclusion, the efficacy of supplemental concentrate during the dry period to increase papillae surface area and k_aVFA in preparation for subsequent lactation is not supported by the present study. Current observations underline the importance of functional measurements in lieu of morphological measurements to assess changes in the adapting rumen wall.     

Varying Protein Content and Nitrogen Solubility for Pluriparous,Lactating Holstein Cows: Lactation Performance and Profitability

Effects on total lactation performance of varying ration crude protein (15.3 vs. 13.6% of dry matter) and nitrogen solubility (35 vs. 45% of total nitrogen) in early lactation was studied using 57 pluriparous Holstein cows. Grain was fed according to production so as to minimize change in body weight throughout lactation. Forages high in nitrogen solubility, corn and grass silages, were fed free-choice. Percent concentrate in ration dry matter was highest (64%) 5 to 8 wk postpartum and lowest (3%) 33 to 44 wk postpartum. Protein and nitrogen solubility were varied by formulating four protein supplements fed as 10% of the grain allocation, so differences in treatments applied narrowed as lactation progressed. Cows fed the medium-protein diets produced 196 kg more milk than those receiving low-protein diets, but their peak daily milk yield was only .6 kg higher. Cows receiving rations with reduced nitrogen solubility produced 347 kg more milk than those fed the higher solubility diets, but their peak daily milk yield was 1.0 kg lower. Income above fed cost for the lactation was highest and postpartum loss in body weight was least for cows receiving medium-protein and low-solubility rations in early lactation, but no differences were significant. Both milk yield (38.3 to 40.6 kg) and total dry matter intake (3.74 to 3.91% body weight) means were maximum 6 to 7 wk postpartum, but lactation performance was not proportional to peak milk yield. When cows are fed to minimize body fat mobilization, response to increased protein in the diet is small. Reducing nitrogen solubility of silage-based diets increased milk produced per unit grain fed. There were no adverse effects of treatments on breeding efficiency or herd health.     

Effect of a dual-purpose inoculant on the quality and nutrient losses from corn silage produced in farm-scale silos

This project aimed to determine effects of applying an inoculant containing homofermentative and heterofermentative bacteria on the fermentation, nutritive value, aerobic stability, and nutrient losses from corn silage produced in farm-scale silos. Corn forage was harvested at 34% dry matter (DM) and treated without (control) or with 5 × 10⁵ cfu/g of Lactobacillus buchneri and Pediococcus pentosaceus. The inoculant was sprayed on alternate 8-row-wide swaths of forage, and the untreated and inoculated forages were alternately packed into 3.6-m-wide bag silos. Forty-five tonnes of corn forage were packed into each of 4 replicate bags per treatment and ensiled for 166 d. Silage removed from the bags (500 kg/d) was separated into good and spoiled (visibly moldy or darker) silage portions, and weighed for 35 d. Weekly composites were analyzed for chemical composition, aerobic stability, and fungal counts. Aerobic stability was measured using data loggers that recorded sample and ambient temperature every 30 min for 7 d. Inoculation did not affect the chemical composition of the spoiled or good silage but decreased the quantity (5.7 vs. 12.9 kg/d) and percentage (3.4 vs. 7.8) of spoiled silage in the bags by over 50%. Losses of crude protein (0.28 vs. 0.92 kg/d), gross energy (6.0 × 10⁴ vs. 1.8 × 10⁵ kJ/d), and neutral detergent fiber (1.34 vs. 4.12 kg/d) in spoiled silage were less in inoculated versus control silages. Inoculated silages had lower pH (3.91 vs. 3.99), lactate concentration (7.63 vs. 7.86%), lactate:acetate ratio (1.58 vs. 2.53%), and a greater acetate (5.11 vs. 3.56%) concentration than the control silage. Inoculated silages tended to have fewer yeasts (2.59 vs. 4.62 log cfu/g) than control silages, but aerobic stability was not different across treatments (14.7 vs. 9.5 h). Applying the inoculant made the fermentation more heterolactic, inhibited the growth of yeasts, and substantially reduced the amount of spoilage and the associated energy and nutrient losses.     

Effect of Forage Maturity on Ration Digestibility and Production by Dairy Cows

Mixed grass-legume silages harvested at early and late maturities from the same field were evaluated in three trials to determine maturity effects on ration digestibility when forages were fed alone or in complete rations. In situ dry matter disappearance was examined using a rumen-fistulated steer. Rate of disappearance of potentially digestible dry matter was reduced for forage of greater maturity (−.0504 h⁻¹ for early versus −.0316⁻¹ for late cut silage). Nonlactating cows were used to determine forage digestibility. Apparent dry matter (69.2 versus 54.2%), acid detergent fiber (70.8 versus 52.7%), neutral detergent fiber (74.1 versus 55.9%), and crude protein (66.2 versus 45.6%) digestibilities were higher for early cut forage.Ration digestibility and milk production response were also measured. Concentrate to forage ratios necessary to meet energy requirements were 60:40 and 78:22 for diets containing early or late cut forage, respectively. Digestibilities of acid detergent fiber (60.2 versus 42.5%) and neutral detergent fiber (62.0 versus 52.7%) were higher for lactating animals consuming ration containing early cut forage. Milk yield and composition was not affected by diet. For each day of advancing forage maturity, approximately 1% more concentrate was needed in the total ration.     

Urea on Flaked Soybean Hulls as a Protein Replacement for Dairy Cows

In Experiment I a Latin square design was used to study the utilization of urea nitrogen adsorbed on flaked soybean hulls in normal rations of high producing dairy cows. Concentrates containing urea, urea with supplemental minerals, or soybean meal as the protein supplement were fed with corn silage and alfalfa in a total ration of approximately 17% crude protein. Both urea concentrates contained 2.7% urea. Animals fed urea and soybean had similar milk yields (28.7 and 27.9 kg/day), milk protein, and digestible dry matter intakes. Urea with mineral produced lower milk yield (25.3 kg/day), milk protein, and dry matter intakes, probably because of excessive mineral content. Urea nitrogen of plasma was similar for all three diets. Essential amino acids of plasma were lower for urea than for soybean while for urea mineral the essential amino acids were midway between the other two. In Experiment 2 a switchback design was used to compare the urea-soybean hull concentrate diet of Experiment 1 (17% crude protein) to a negative control diet consisting of its basal components without urea adjusted to 12% protein with wheat bran. Milk yield was 1.2 kg/day higher when the urea diet was fed. Perhaps due to improved urea distribution in the rumen, flaked soybean hulls with urea were effective in maintaining the feed intake necessary for high milk production.     

Feeding Value of Dry Corn,Ensiled High Moisture Corn,and Propionic Acid Treated High Moisture Corn Fed with Hay or Haylage for Lactating Dairy Cows

Trial 1. Fifty lactating Holstein and Brown Swiss cows were assigned to six groups in a 3 × 2 factorial design and fed one of six diets for 16 wk: (1) dry corn + hay, (2) dry corn + haylage, (3) ensiled high moisture corn + hay, (4) ensiled high moisture corn + haylage, (5) propionic acid treated corn + hay, and (6) propionic acid treated corn + haylage. Quantities equal in dry matter of dry corn, ensiled corn, and acid treated corn were offered in the ratio of 1 kg concentrate (corn and supplement) for each 2.75 kg milk produced. Forage was fed free choice. Means adjusted by covariance for cows fed diets 1 to 6 averaged: dry matter intake (kg/day), 16.7, 20.0, 17.4, 20.6, 17.1, 20.0; 4% fat-corrected milk (kg/day), 21.8, 21.1, 22.6, 23.5, 22.4, 23.4; milk fat percent, 3.54, 3.45, 3.63, 3.53, 3.62, 3.80; and acetate to propionate ratio 3.53, 3.85, 3.73, 3.66, 3.13, 3.32. Cows fed ensiled corn and acid treated corn produced more 4% fat-corrected milk than did cows fed dry corn. The molar percent acetate to propionate ratio in rumen fluid of cows fed acid treated corn was lower than for cows fed dry corn or ensiled corn.Trial 2. Dry corn or propionic acid treated corn was fed to 12 cows in combination with a supplement, 4.54 kg of hay, and ad libitum haylage. Means adjusted by covariance for cows fed dry corn and acid treated corn averaged: dry matter intake (kg/day), 18.2 and 17.7; 4% fat-corrected milk (kg/day), 20.6 and 20.1; and total digestible nutrients (%) 63.7 and 58.7.Any of these methods are acceptable for storing corn, and feeding this corn in properly supplemented diets will yield acceptable lactation performance.     

Effect of Dietary Concentrate on In Situ Dry Matter and Nitrogen Disappearance of a Variety of Feedstuffs

Two ruminally cannulated steers were fed 80 or 40% concentrate diets at 1.7% of body weight (dry matter) in a crossover design. Eighteen feedstuffs (eight protein supplements, six energy feeds, and four roughages) were incubated ruminally for 4, 12, and 24 h and dry matter and nitrogen disappearance were measured. For protein supplements, correlations between soluble nitrogen (.15 N sodium chloride) and nitrogen disappearance at 4, 12, and 24 h were .82, .94, and .87. Dry matter disappearance and nitrogen disappearance for all substrates were related at 4, 12, and 24 h (correlation coefficients of .59, .80, and .57). Generally, disappearance of dry matter and nitrogen were greater for the 40 than for the 80% concentrate diet for soybean meal, cottonseed meal, and linseed meal at 12 and 24 h of incubation. Nitrogen residues at 24 h agreed reasonably well with in vivo estimates of ruminal protein escape, except for feeds such as meat meal and corn gluten meal. Predictions of ruminal protein escape were calculated based on in situ nitrogen disappearance by two equations that illustrate potential effects of feed intake and dietary concentrate.     

Seasonal Changes of Mineral Content of Southern Forages

Forage samples were collected at 2-wk intervals during the grazing season from bermudagrass, bahiagrass, millet, and mixed oats and ryegrass pastures. Immature stands of the summer grasses were maintained by rotational grazing and clipping. Corn silage, sorghum silage, and concentrate samples were collected bi-weekly at feeding. Forages and silages were grown on a Providence silt loam soil and fertilized according to results of soil analyses. Sorghum silage was higher in magnesium (.34 versus .21%) and potassium (1.47 versus 1.11%) than corn silage. Both silages were low in copper, zinc, and selenium and averaged 5.6, 21.8, and .056 μg/g. Bermudagrass and bahiagrass contained less calcium and potassium than millet or oats and ryegrass. Differences existed among the grasses in manganese, copper, zinc, and selenium. Concentrations in bermudagrass, bahiagrass, oats and ryegrass, and millet were 111.1, 139.9, 84.6, and 90.0 μg/g for manganese; 8.0, 8.5, 5.8, and 15.3 μg/g for copper; 35.0, 29.4, 23.0, and 43.3 μg/g for zinc; and .164, .086, .082, and .076 μg/g for selenium. For bahiagrass, changes occurred in concentration of all minerals during April through October. For oats and ryegrass, all minerals except zinc varied during November through May. For bermudagrass, copper and phosphorus exhibited significant changes of concentration during the grazing season.     

Evaluation of Sunflower Crop Residue in Rations for Growing Holstein Heifers

Sunflower crop residue, a mixture of stalks and heads, contained 65.4% dry matter, and dry matter was 6.1% crude protein, 66.9% neutral detergent fiber, 56.6% acid detergent fiber, 15.7% lignin, and 12.6% total ash. In vitro dry matter and cell wall digestibilities were 40.6 and 31.4%. Sixteen Holstein heifers (mean weight 247 kg) were assigned to one of four rations containing 0, 8, 16, or 32% sunflower residue (dry matter). Mid-bloom alfalfa hay and a grain mixture (corn, soybean meal, dicalcium phosphate, vitamins A, D, and E) were 30 and 20% of dry matter with corn silage providing the remaining dry matter. Weight gains during a 70-d trial were 1.31, 1.18, .91, and .98 kg/d for 0, 8, 16, and 32% sunflower residue. Dry matter digestibilities decreased with increased sunflower residue in the ration. Ruminal propionate (mol/100 mol total volatile fatty acids) decreased with increasing sunflower residue, resulting in higher acetate-to-propionate ratios. Total volatile fatty acids, ruminal pH, and ammonia concentrations were not different among diets. With proper supplementation, sunflower crop residue was an acceptable roughage up to 32% of total ration dry matter for growing Holstein heifers.     

Effect of Adding Formaldehyde,Glutaraldehyde, or Dimethylolurea to Alfalfa before Ensiling

Formaldehyde, glutaraldehyde, or dimethylolurea were sprayed on alfalfa wilted to approximately 35 and 62% dry matter at rates of 1, 3, and 4 g of formaldehyde; 1.7, 5.0, and 6.7 g of glutaraldehyde; and 2.5, 5.0 and 10 g of dimethylolurea/100 g of crude protein. Treatment of alfalfa with formaldehyde resulted in marked inhibition of silage fermentation as characterized by large amounts of residual water-soluble carbohydrates and low amounts of lactic acid, free NH₃-N, and amino acids. The effects with glutaraldehyde and dimethylolurea were similar but to a lesser extent. Addition of formaldehyde and glutaraldehyde resulted in similar reductions of rumen degradable nitrogen as estimated by in situ techniques. However, fiber digestion tended to be less for glutaraldehyde than formaldehyde silage. Addition of these additives to alfalfa containing 62% dry matter resulted in almost complete inhibition of silage fermentation. Presence of surface mold on the 62% dry matter-treated silages suggest that the silage was unstable.     

By-Product Feeds for Lactating Dairy Cows: Effects of Cottonseed Hulls,Sunflower Hulls,Corrugated Paper,Peanut Hulls,Sugarcane Bagasse,and Whole Cottonseed with Additives of Fat,Sodium Bicarbonate,and Aspergillus oryzae Product on Milk Production

In Experiment 1, Holstein cows (32) fed diets in three 28-day periods were used to evaluate a 3 × 2 × 2 factorial arrangement of fiber sources (sunflower hulls, pelleted cottonseed hulls, and pelleted undelinted cottonseed hulls at 35% of dry matter), fat (0 or 2.5%). and sodium bicarbonate (0 or 1.0%). Sixteen cows also received Aspergillus oryzae product (56.7 g/day) continuously. Sunflower hulls decreased daily intake (19.4 versus 25.1 kg), milk (23.3 versus 26.5 kg), milk protein (2.85 versus 2.95%), and body weight change (?.08 versus .90 kg), but milk fat percent was higher (3.54 versus 3.32%). Sunflower hulls depressed digestibility of dry matter, organic matter, and acid detergent fiber. Added fat reduced milk fat and protein percents. Experiment 2 evaluated fiber sources (20% ground corrugated cardboard boxes, combination of 10% cardboard and 10% peanut hulls, or 30% cottonseed hulls), animal fat (0 or 2.5%), sodium bicarbonate (0 or .75%), and condensed molasses solubles by-product from rum distilling (0 or 10%). Corrugated boxes effected lowest intake (18.0 kg/day), cottonseed hulls highest intake (23.5 kg/day), and combination intermediate (20.2 kg/day). Added fat depressed fat percent. Condensed molasses solubles lowered milk yield but increased milk fat percent (3.76 versus 3.30), molar percent of acetic acid, and ratio of acetic to propionic. In two other experiments whole cottonseed (12.5 or 15% of dry matter) with corn silage, pelleted steam pressure treated sugarcane bagasse, or cottonseed hulls increased milk yield but decreased milk fat percent, especially with pelleted bagasse.     

The effects of feeding rations that differ in fiber and fermentable starch within a day on milk production and the daily rhythm of feed intake and plasma hormones and metabolites in dairy cows

A daily pattern of feed intake, milk synthesis, and plasma metabolites and hormones occurs in dairy cows fed a total mixed ration once or twice a day. The objective of this study was to determine if feeding multiple rations within a day, complementing these rhythms, would improve milk production. Twelve Holstein cows were used in a replicated 3 × 3 Latin square design with 21-d periods. Cows were housed in tie stalls with feed tubs, and feed weight was recorded every 10 s for observation of feeding behavior. Rations were a low fiber and high fermentable starch ration [LFHS; 27.4% neutral detergent fiber (NDF) and 31.7% starch based on 55.7% corn silage and 14.1% steam-flaked corn], a high fiber and low fermentable starch ration (HFLS; 31.7% NDF and 22.3% starch based on 44% corn silage, 26.3% alfalfa haylage, and no steam-flaked corn), and a total mixed ration that was a 1:3 ratio of LFHS and HFLS (30.7% NDF, 24.5% starch). The control treatment (CON) cows were fed the total mixed ration at 0700 h, the high/low treatment (HL) fed HFLS ration at 0700 h and LFHS ration at 2200 h, and the low/high (LH) treatment fed LFHS ration at 0700 h and HFLS ration at 1100 h (LFHS and HFLS rations fed at a 1:3 ratio). No effect was found of treatment on daily milk, but LH decreased milk fat concentration and yield compared with HL (0.2 percentage units and 0.24 kg, respectively). Daily dry matter and NDF intake and total-tract digestibility did not differ between treatments. The HL treatment reduced intake at the morning-conditioned meal after feeding and reduced intake before the evening feeding. A treatment by time of day interaction was found for fecal NDF and indigestible NDF concentration, blood urea nitrogen (BUN), plasma insulin, and fatty acid concentration, and body temperature. The CON and LH treatments increased the daily amplitude of fecal NDF by 1.0 and 1.1 percentage units compared with HL. Plasma insulin was higher in HL than CON at 0100 and 0400 h, but lower at 1300 and 1900 h. Plasma fatty acids were higher for CON than HL at 0700 h and HL was lower than LH at 0400 and 1900 h. Plasma BUN was higher for HL than control at 0100 h, but lower at 1000 h. Body temperature in CON and HL treatments followed a similar diurnal pattern, whereas body temperature for LH was lower than that of HL treatment at 1300 and 2300 h. No daily rhythm was found of fecal indigestible NDF concentration, plasma glucose, or fatty acids detected in the HL treatment, and the amplitude of plasma insulin and BUN was lower for HL compared with CON (70 and 60% decrease, respectively). In conclusion, feeding 2 rations that differ in fiber and fermentable starch modifies diurnal rhythms in dairy cows. Furthermore, feeding a high fiber and low fermentable starch ration during the high intake period of the day may stabilize nutrient absorption across the day.     

Adrenal Response During Periparturient Period to Adrenocorticotropin in Dairy Cattle Fed Corn Silage and Grass Legume Silage

Glucocorticoid response to exogenous adrenocorticotropin was used as an indicator of stress in cows fed different diets ad libitum during the dry period and throughout lactation. Twenty-three Holstein cows were administered adrenocorticotropin at 2 d after initiation of the dry period and at 2 d and 35 d postpartum, and plasma glucocorticoid response was evaluated. Cows were fed diets using only corn silage as forage or mixed forage with or without supplemental concentrate. Mean basal plasma glucocorticoid concentrations were 6.1 ng/ml on d 2 after dry off, 4.7 ng/ml on d 2 postpartum, and 6.7 ng/ml on d 35. Cows on the 32.5:32.5:35 corn silage:grass-legume silage:concentrate diet had the lowest basal glucocorticoid concentrations on d 2 postpartum but highest concentrations on d 35 of lactation. Mean glucocorticoid response was 33.2 ng/ml on d 2 of lactation compared with 50.6 ng/ml on d 35 and 48.5 ng/ml plasma on d 2 following drying off. Diet interactions suggest that feed components may be involved with ability to tolerate stresses that occur during lactation and the dry period and thus may lead to altered adrenal function.     

Influence of Pelleting Whole Cottonseed on Ration Digestibility and Milk Production and Composition

Two trials were conducted to determine the effect of pelleting whole cottonseed on milk production and composition and ration digestibility. In trial 1, four multiparous Holstein cows were paired by production and used in a 2 × 2 reversal design with 37-d experimental periods. Cow receiving pelleted cottonseed produced 35.12 kg/d milk and 31.74 kg/d of 4% fat corrected milk as compared with 33.41 and 29.83 for cows receiving whole cottonseed. There were no significant differences in dry matter intake or milk composition between treatments. Yield of total solids and lactose was greater for cows receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility coefficients for dry matter, gross energy, and crude protein were not different due to pelleting.In trial 2, four ruminal and abomasally cannulated Holstein steers were paired in a 2 × 2 reversal design and fed either pelleted on whole cottonseed for 10 d followed by a 7-d collection. Steers receiving the pelleted cottonseed had higher intakes of gross energy and crude protein. There were greater amounts of total crude protein and crude protein in the particulate phase of abomasal digesta from steers receiving pelleted cottonseed as compared with whole cottonseed. Apparent digestibility for crude protein for the whole tract was not different due to treatment.     

Formaldehyde Treated Whey Protein Concentrate for Lactating Dairy Cattle

Four lactating Holstein cows were fed isonitrogenous rations of urea-corn silage and a 15% crude protein pelleted grain ration containing whey protein concentrate (34% protein) either untreated or treated with 1% formaldehyde on a protein basis. The trial design was three periods double reversal with 12 days per period during which milk and digestibility were measured the last 4 days of each period. Apparent nitrogen digestibility (%), productive nitrogen retained (milk plus retained, g/day), and dry matter digestibility were 60.0 and 53.9, 89.0 and 103.8, and 67.4 and 63.2 for cows fed untreated and treated rations. Productive nitrogen as a percent of absorbed was greater for cows fed the formaldehyde treated ration, suggesting more efficient utilization of absorbed nitrogen. Milk production, milk fat percent and yield, and 4% fat-corrected milk were greater for cows fed the treated ration. Milk fatty acid content was similar. Total daily milk nitrogen, true protein nitrogen, and casein nitrogen yields were not significantly higher for the treated ration. No differences in serum urea and rumen ammonia were major. Rumen volatile fatty acids were higher in cows fed the untreated rations at 4 and 6 h postfeeding. Differences in serum concentrations of most individual essential amino acids between tail and mammary blood were greater for cows fed the treated ration.