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PubMed2000

Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 2. Chewing activities.

The effects of digestibility of corn silage neutral detergent fiber (NDF) and dietary NDF content on chewing activities were evaluated with eight multiparous high producing dairy cows in a duplicated 4 x 4 Latin square design with 21-d periods. Experimental diets contained corn silage from a brown midrib (bm3) hybrid or its isogenic normal control at two concentrations of dietary NDF (29 and 38%). The NDF digestibility estimated by 30-h in vitro fermentation was higher for bm3 corn silage by 9.4 units (55.9 vs. 46.5%). Feeding behavior of animals and ruminal pH were monitored continuously for 4 d in each period by a computerized data acquisition system. Ruminal digesta were evacuated twice per period to determine the ruminal NDF pool and its turnover rate. There was no effect of NDF digestibility on total chewing time either per day or per kilogram of NDF intake, or on ruminating time either per day or per kilogram of NDF intake. Although bm3 treatments increased the turnover rate of NDF in the rumen, they increased dry matter intake and had no effect on ruminal NDF pool size. Total chewing time and ruminating time per day were related positively to NDF intake and ruminal NDF pool size, but were not related to ruminal turnover rate of NDF. These results provide no evidence that enhanced NDF digestibility decreases the physical effectiveness of NDF of corn silage.

Animals↗
PubMed2000

Influence of mechanical processing on utilization of corn silage by lactating dairy cows.

We conducted three experiments to determine the influence of mechanical processing on corn silage utilization by lactating dairy cows. Total mixed rations contained either unprocessed or processed corn silage harvested between 1/4 and 3/4 milk line. In trial 1, 12 multiparous Holstein cows were used in a replicated double switchback design with 21-d periods. Intake of dry matter (DM) was increased 1.2 kg/d by processing, but milk yield was unaffected. Processing did not affect apparent total-tract DM digestibility, but processing tended to lower starch and corn excretion in feces and reduced concentration of sieved corn kernel particles in feces. In trial 2, 42 Holstein cows were used in an 18-wk randomized complete-block design. Intake of DM and milk yield were unaffected by processing, but milk fat percent was increased 0.35 percentage units by processing. Processing tended to increase total-tract digestibility of starch, but reduced organic matter, crude protein, and neutral detergent fiber digestibilities. In trial 3, 30 Holstein cows were used in a 15-wk randomized complete block design. There was no influence of mechanical processing on intake or lactation performance in this trial. Despite indications of increased starch digestion in two trials and increased DM intake in one trial, effects of processing corn silage on lactation performance were minimal with corn silage at the maturity and moisture contents used in these trials.

Animals↗
PubMed2002

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.

Animals↗
PubMed2003

Influence of glyphosate-tolerant (event nk603) and corn rootworm protected (event MON863) corn silage and grain on feed consumption and milk production in Holstein cattle.

Two studies were conducted to evaluate the effect of a glyphosate-tolerant (event nk603) and a corn rootworm protected (event MON863) corn hybrid on feed intake and milk production compared with the nontransgenic hybrid and two reference hybrids. In Experiment 1, 16 multiparous Holstein cows were assigned to one of four treatments in replicated 4 x 4 Latin squares with 28-d periods. Diets contained 40% (dry matter [DM] basis) of either 1) glyphosate-tolerant corn silage (GT), 2) nontransgenic control corn silage, or 3) two nontransgenic reference hybrids which are commercially available. Each diet also contained 23% corn grain from the same hybrid that supplied the silage. At ensiling, rapid drying conditions prevailed and the GT hybrid was the last to be harvested which resulted in greater DM content at similar physiological maturity. The 4% fat-corrected milk (FCM) yield and DMI were reduced for cows fed the GT corn diet due to the higher DM content of the GT silage (37.1 vs. 33.2 kg/d and 4.05 vs. 3.61% of BW, respectively). There was no effect of the GT diet on milk composition or efficiency of 4% FCM production that averaged 1.43 kg/kg of DM intake for all diets. In Experiment 2, 16 multiparous Holstein cows were assigned to one of four treatments in replicated 4 x 4 Latin squares with 21-d periods. Diets contained 26.7% (DM basis) corn grain from either 1) corn rootworm protected (event MON863) corn hybrid, 2) nontransgenic control corn hybrid, or 3) the same two nongenetically enhanced reference hybrids used in Experiment 1. The 4% FCM yield (34.8 kg/d) and DM intake (4.06% of BW) were unaffected by diet. Efficiency of FCM production (average 1.32 kg/kg of DMI) was not affected by diet. In summary, these two studies indicated that insertion of a gene for glyphosate tolerance or corn rootworm protection into a corn hybrid did not affect its nutritional value (as measured by efficiency of milk production) for lactating dairy cows compared with conventional corn hybrids.

Animal Feed↗
PubMed2003

Effects of various glucogenic sources on production and metabolic responses of dairy cows fed grass silage-based diets.

Four rumen cannulated Finnish Ayrshire cows in midlactation were used in an experiment designed as a 4 x 5 incomplete Latin square with 2-wk periods to compare effects of glucogenic substrates on grass silage-based diets. The five treatments were continuous infusions of 1) water (control), 2) casein 300 g/d, 3) glucose 300 g/d, 4) propionic acid 247 g/d, and 5) barley starch 270 g/d. Substrates were infused either into the rumen (propionic acid) or into the abomasum (other substrates). As a basal diet, cows were fed a formic acid treated grass silage ad libitum (digestible organic matter 690 g/kg dry matter [DM], crude protein [CP] 131 g/kg DM) and a barley-rapeseed concentrate (CP 141g/kg DM) at a rate of 7 kg/d. Production responses to glucogenic substrates other than casein were negligible, suggesting that glucose supply of the cows did not primarily limit milk production. However, with casein cows produced significantly more milk, milk protein, and lactose than with other glucogenic substrates. Casein increased urea and essential amino acid (EAA), and decreased nonessential AA (NEAA) in arterial plasma compared with other substrates, suggesting that casein provided precursors both in terms of NEAA for gluconeogenesis and EAA for milk protein synthesis. This puts forward that providing the AA needs of the mammary gland for milk protein synthesis are met, glucose supply may become the next limiting factor for milk protein synthesis in cows fed diets based on restrictively fermented grass silage. The limited supply of AA from the basal diet, and possibly the low production levels of cows partly invalidated the hypothesis of monitoring differing glucogenic substrates for grass silage-based diets.

Abomasum↗
PubMed2003

Effects of corn silage processing and amino acid supplementation on the performance of lactating dairy cows.

This experiment was conducted to determine the effect of crop processing and amino acid supplementation on dairy cow performance. Corn silage processed (PCS) or unprocessed (UCS) was used as the main forage (45% of dry matter, DM) in a total mixed ration (TMR). Each TMR was either supplemented (AA) or not (AAO) with ruminally protected amino acids (lysine, 3 g/d and methionine, 14 g/d). Thirty-two (551 kg) Holstein cows were randomly assigned to four treatments: PCS-AA, PCS-AA0, UCS-AA, and UCS-AA0 in a 2 x 2 factorial structure. Between wk 7 and 17 of lactation, cows were fed ad libitum TMR comprising 45% of corn silage plus 1 kg of grass hay once a day. The UCS presented better fermentation characteristics than PCS. Dry matter intake (DMI) of the TMR was not affected by treatment and averaged 22.7 kg/d. Energy-corrected milk (ECM) production was 9% higher with UCS than with PCS (33.1 vs. 30.1 kg/d). Milk efficiency was therefore 6% higher with UCS than with PCS (1.43 vs. 1.35 kg ECM/kg of DMI). The concentration of major milk constituents (fat, protein, lactose, urea) was not affected by treatments. Apparent digestibility of DM, organic matter, N, starch, acid detergent fiber, and neutral detergent fiber were similar among treatments. The effective ruminal degradability of DM, starch, and protein, however, was greater with PCS than with UCS. Amino acid supplementation had no effect on milk production nor on milk constituents, whether it was used with processed corn silage or with unprocessed corn silage. These data indicate that feeding UCS resulted in a greater milk production compared with PCS. The numerically higher DMI, a potentially greater intestinal digestion of starch or the better conservation of UCS could have contributed to the greater milk production.

Amino Acids↗
PubMed2004

Influence of corn variety and cutting height on nutritive value of silage fed to lactating dairy cows.

Two corn varieties predicted to differ in digestibility were harvested at 2 cutting heights (10.2 or 30.5 cm) to determine effects on the nutrient content of the resulting silage, nutrient intake, nutrient digestibility, and production of lactating cows fed such corn silage originally harvested at two-thirds milk line. Acid detergent fiber (ADF) concentration was higher and in vitro true dry matter (DM) digestibility (IVTDMD) was lower for the variety predicted to have average digestibility. An interaction was observed between variety and cutting height because of decreased ADF and increased IVTDMD for the average digestibility variety cut at 30.5 vs. 10.2 cm; no differences were observed for the higher digestibility variety at each cutting height. When silages were fed to 32 Holstein cows in a 5-wk randomized design trial, DM intake, milk yield, and milk composition were similar. There was an interaction between variety and cutting height for DM intake and total tract apparent digestibility of DM, crude protein, and neutral detergent fiber because of lower intake and digestibility for the diets containing either the high cut, average quality variety or low cut, higher quality variety. These results suggest that increasing the cutting height to 30.5 cm does not improve silage quality or improve milk yield of cows. Although the 2 varieties selected for this trial were predicted to differ in digestibility, these differences were not great enough to influence milk yield or composition of lactating cows.

Agriculture↗
PubMed2004

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.

Acetates↗
PubMed2006

Effects of physically effective fiber on chewing activity and ruminal pH of dairy cows fed diets based on barley silage.

The objective of this study was to investigate the effects of physically effective neutral detergent fiber (peNDF) content of dairy cow diets containing barley silage as the sole forage source on feed intake, chewing activity, and ruminal pH. The experiment was designed as a replicated 3 x 3 Latin square using 6 lactating dairy cows with ruminal cannulas. Cows were offered 1 of 3 diets (high, medium, and low peNDF) obtained using barley silage that varied in particle length: long (theoretical cut length of 9.5 mm), medium (equal proportions of long and fine silages), and fine (theoretical cut length of 4.8 mm). The peNDF contents were determined using the Penn State Particle Separator and were 13.8, 11.8, and 10.5%, for the high, medium, and low diets, respectively. The physical effectiveness factors (defined as proportion retained on 19- and 8-mm screens) for the long and fine silages were 0.84 and 0.68, respectively. Increased forage particle size increased intake of peNDF but did not affect intake of DM and NDF. Ruminating and total chewing time were linearly increased with increasing dietary peNDF. Mean ruminal pH, area between the curve and a horizontal line drawn at pH 5.8 or 5.5, and time that pH was below 5.8 or 5.5 were not affected by peNDF content. Intake of peNDF was not correlated to any chewing activity but proportion of long particles on the 19-mm sieve tended to be correlated to ruminating chews (r = 0.36) and ruminating time (r = 0.36). These results indicate that increasing the peNDF content of diets increases chewing time. However, increased chewing time does not always improve ruminal pH status. Increasing chewing time and thus increasing salivary secretion may not fully overcome the effects of feed digestion and the production of fermentation acids that lower rumen pH. The results suggest that dietary peNDF and fermentable OM intake are critical in regulating rumen pH. Dietary particle size, expressed as peNDF, was a reliable indication of chewing activity.

Animals↗
PubMed2006

Evaluation of palm kernel meal and corn distillers grains in corn silage-based diets for lactating dairy cows.

The effects of increasing levels of solvent-extracted palm kernel meal (SPKM) and corn distillers dried grains (CDG) in corn silage-based diets on feed intake and milk production were examined in 2 experiments. In Experiment 1, 20 Holstein cows averaging 100 d in milk (DIM) (SD = 61.5) at the start of the experiment were utilized in an 11-wk randomized complete block design with 4 treatments in 5 blocks to study effects of increasing levels of SPKM in the diet. During a 3-wk preliminary period, cows were fed a standard diet. At the end of the preliminary period, cows were blocked by 4% fat-corrected milk yield, parity number (primiparous and multiparous), and DIM, and were assigned randomly to 1 of 4 experimental diets. The total mixed ration (TMR) consisted of (dry matter basis) 40% corn silage, 5% coarsely chopped wheat straw, and 55% concentrate. The increasing dietary levels of SPKM were achieved by replacing protein sources and citrus pulp with SPKM and urea (0, 5, 10, and 15% SPKM and 0.06, 0.22, 0.38, and 0.55% urea for SPKM0, SPKM5, SPKM10, and SPKM15, respectively). In Experiment 2, 18 Holstein cows averaging 93 DIM (SD = 49.1) at the start of the experiment were utilized in an 11-wk randomized complete block design with 3 treatments in 6 blocks to study effects of increasing levels of CDG in the diet. The preliminary period lasted for 2 wk. Assignment of cows to treatments was the same as in Experiment 1. The TMR consisted of (dry matter basis) 40% corn silage, 5% coarsely chopped wheat straw, and 55% concentrate. The increasing dietary levels of CDG were achieved by replacing soybean meal and citrus pulp with CDG and urea (0, 7, and 14% CDG and 0, 0.22, and 0.49% urea for CDG0, CDG7, and CDG14, respectively). There were no significant treatment effects on dry matter intake, milk yield, or milk composition in Experiment 1. Inclusion of SPKM tended to increase protein and lactose contents of milk. The SPKM0 diet promoted body weight loss. There were no treatment effects in Experiment 2, except for milk protein content, which was decreased by CDG. Plasma Lys concentration tended to be affected by SPKM and CDG inclusions. Plasma concentrations of 3-methylhistidine and Leu seemed to be related to body protein degradation/synthesis. The feeding of SPKM up to 15% in the diet decreased feed costs without detrimental effects on productive responses and tended to increase milk protein content. The inclusion of CDG in diets based on corn silage and corn byproducts might decrease milk protein content due to an unbalanced supply of AA, particularly Lys.

Amino Acids↗
PubMed1975

Fungal growth and acid production during fermentation and refermentation of organic acid treated corn silages.

Chopped corn (35% dry matter) treated with either propionic, formic, 60% propionic plus 40% formic, or 80% propionic plus 20% acetic acids at 0, .5, 1, and 2%, was placed in polyethylene bags inside metal drums, and evacuated. During fermentation silages were sampled and temperatures determined. On day 40 of fermentation silages were placed in open containers at 25 C and were sampled during refermentation. All samples were analyzed for volatile and lactic acids, pH, and number and type of fungi. Lactate fermentation was totally inhibited at 2% addition of all acids, but formic acid was more effective than propionic acid at .5 and 1%. Acerate production was equally depressed by both propionic and formic additions. Heating, growth of fungi, and days until spoilage were delayed by all acid additions during refermentation, with propionic more effectivethan formic. The large increases in lactate and acetate of treated silages during refermentation reflect a protection of soluble sugars during fermentation and subsequent use by microbes after exposure to air. Silages treated with more than 1%propionic (as propionic or a mixture) did not increase in fungal colonies during refermentation. At initiation of fermentation yeasts werehigher than other fungi but decreases by day 40. During refermentation, yeasts again grew. Geotrichum comprised 35% on day 40 of refermentation but was lower at other times. Aspergillus proliferated during refermentation and few Penicillium were detected.

Acetates↗
PubMed1980

Ammonia versus urea-treated silages with varying urea in concentrate.

In four factorial experiments, 96 lactating Holstein cows averaging 100 days postpartum were fed corn silage (21 to 31% dry matter) ad libitum treated with aqueous ammonia (.3 to .4%) or urea (.5 to .7%). Concentrates fed at 1 kg/3 kg milk contained 0, .7, or 1.4% urea in Experiment 1 and 0 or 1.4% in Experiments 2, 3, and 4. Following 14-day pretreatment, experimental rations were fed for 65 days in Experiment 1 and 84 days in Experiments 2, 3, and 4. Urea in grain and urea in silage depressed intakes of silage and total dry matter. Milk persistences were lowered only by the diet containing urea in both grain and silage. Bodyweight changes, percent milk fat, and feed efficiencies were not altered significantly by treatments.

Ammonia↗
PubMed1980

Woodpulp fines or corn silage as roughages in complete rations or a pelleted complete ration for young dairy replacements from birth through 18 weeks of age.

Holstein calves, 18 females and 12 males, were assigned randomly to 10 blocks of 3 calves each by sex, and within each block were assigned randomly to one of three experimental rations. All calves received sour colostrum from day 1 through day 35. The respective dry rations were offered beginning at day 8. The three rations consisted of (dry basis): 1) 11% woodpulp fines and 89% concentrate; 2) 33.7% corn silage and 66.3% concentrate; and 3) a commercially available pelleted complete ration. From birth through 8 wk, calves fed woodpulp gained more weight than those fed silage and approximately equal weight to calves fed commercial ration. From 8 through 18 wk. calves fed the latter gained more weight than other calves. Dry matter intake followed the same order as weight gain. Blood samples were obtained biweekly beginning with the 2nd wk from the jugular vein of each calf. There were no differences in glucose 2 through 18 wk. Urea nitrogen of plasma was greater in calves fed commercial ration than in other calves in six of the sampling periods. Calves fed silage had more urea nitrogen in plasma than calves fed woodpulp for three of the sampling periods. Rumen tissue from male calves at 18 wk fed woodpulp showed the most normal appearance in papillae color, density, and length. Calves fed silage had rumen tissue showing short, black, nodular papillae. Calves fed commercial ration showed long, branched, necrotic papillae that were keratotic and loosely attached.

Animal Feed↗
PubMed1980

Woodpulp fines or corn silage as roughages in complete rations or a pelleted complete ration for young dairy replacements 18 through 36 weeks of age.

Twenty-eight Holstein calves were fed one of three experimental diets from 18 through 36 wk: 1) 50% woodpulp fines, 25% corn silage, and 25% concentrate; 2) 75% corn silage and 25% concentrate; and 3) a commercially available, pelleted, total calf ration. The first two rations were equivalent in roughage, vitamin, and mineral content, and all three rations were equivalent in crude protein. Average daily gain (kg), dry matter intake (% of body weight), and feed/gain for calves fed the three rations were .92, 2.42. 6.28; 1.10, 2.29, 4.07; and 1.12, 3.16, 6.73. Glucose (mg/100 ml), urea nitrogen (mg/100 ml), and B-hydroxybutyrate (mg/100 ml) in plasma from calves at 23 wk were 72.0, 5.2, .7; 72.5, 5.1, 1.9; and 82.4, 12.3, .8. The amount of butyrate (% of total), acetate/propionate, and pH of the rumen fluid from calves at 23 wk were 6.31, 2.79, 6.99; 11.74, 2.76, 7.05; and 9.89, 2.04, 6.73. Papillae length (cm) and density/cm2 ofa the rumen tissue from male calves by biopsy were: 1.83, 48.5; 2.12, 67.1; and 2.12, 27.6. Corn silage and woodpulp fines or corn silage alone can be fed to dairy calves in complete rations with satisfactory results from 18 to 36 wk of age. Additional experimentation is required to optimize quantities and proportions of these roughages in complete rations for young heifers.

3-Hydroxybutyric Acid↗
PubMed1983

Changes of tocopherols in blood serum of cows fed hay or silage.

The purpose was to determine if cows fed corn silage during gestation have calves with low serum tocopherol and high erythrocyte hemolytic rates. Ten cows were fed hay, six fed corn silage with one vitamin E injection, and six fed corn silage with no injection beginning with the 6th mo of gestation. Hay intakes were adjusted to equalize intakes of dry matter. Analysis of tocopherol isomers was by reverse phase, high performance liquid chromatography. Alpha-tocopherol and potassium were lower for hay-fed cows than for cows fed predominantly corn silage, but creatinine phosphokinase, glutamic-oxaloacetic transaminase, and glucose were higher. Calves from hay-fed cows had lower alpha-tocopherol and higher glutamic-oxaloacetic transaminase. No consistent histopathological changes of muscle tissue were seen. Erythrocyte hemolytic rates were low. Serum vitamin E of cows may change during gestation because of type of forage fed. Specific enzyme changes may give an early indication of a change of tocopherol status of cattle.

Animals↗
PubMed1992

Effect of copper and cobalt addition on digestion and growth in heifers fed diets containing alfalfa silage or corn crop residues.

Copper and cobalt were added to the diet of heifers in excess of NRC recommendations for these minerals. In Experiment 1, the rate of DM disappearance from dacron bags placed in the rumen was increased by the additional dietary Cu and Co for alfalfa hay (14.6 vs. 8.4%/h) and corn cobs (5.8 vs. 3.1%/h) but did not affect the DM disappearance rate for corn crop residue silage (3.6 vs. 3.4%/h). In Experiment 2, additional Cu and Co increased DM disappearance rate of corn crop residue silage (6.2 vs. 3.4%/h) but did not influence the rate of alfalfa hay (8.6 vs. 7.6%/h). In Experiment 3, a random design with a 2 x 2 factorial arrangement was used. The diet consisted of 45% corn crop residue silage, 35% alfalfa silage containing 60 or 40% DM, 18% high moisture corn, and 2% vitamin and mineral mix with or without added Cu and Co, respectively. Each of the four diets was group-fed to 9 light and 11 heavy Holstein heifers. Growth rate was lower with Cu and Co supplementation, but DM digestibility was improved by the additional Cu and Co. These results indicate that addition of Cu and Co above the NRC requirements may aid in digestion of low quality forages.

Animals↗
PubMed1992

Nitrogen metabolism in rumen and whole digestive tract of lactating dairy cows fed grass silage.

Effects of wilting of grass prior to ensiling on OM intake, ruminal digestibility, efficiency of bacterial protein synthesis, and amount and composition of duodenal N fraction were examined using four lactating Holstein cows. Direct-cut or wilted grass silages were fed for ad libitum intake and supplemented with 5.0 or 5.3 kg of concentrate, respectively. Milk yield was 18.1 and 21.2 kg/d with direct-cut versus wilted silage, and milk protein and fat contents were 2.63 and 4.60% with direct-cut versus 2.75 and 4.27% with wilted silage, respectively. Wilting of the grass (from 17 to 38% DM) increased OM intake but had no effect on ruminal digestibility. Total N flow and amounts of different AA in proximal duodenum were increased, and the difference was principally of bacterial origin. The efficiency of bacterial protein synthesis in rumen was related to dilution rate of liquid phase and to the time devoted to ruminating. These results indicate that the passage of bacterial protein to the lower digestive tract is a key factor for improving the assimilation of the soluble N fraction of grass silage and that this phenomenon is related to chewing activity.

Ammonia↗
PubMed1994

Changes in plasma alpha-tocopherol and selenium of gestating cows fed hay or silage.

The effects of dietary hay or silage on plasma alpha-tocopherol and Se concentrations during late gestation and early lactation were studied using 40 crossbred pregnant cows and their calves. Cows received solely either timothy hay or grass silage forage from midgestation to early lactation and 21 d prior to estimated calving were or were not injected with Se (30 mg) and alpha-tocopherol (3000 IU). Five blood samples were collected for determination of concentrations of alpha-tocopherol and Se twice during late gestation and three times after calving. Blood samples from calves were collected at birth and at 10 and 30 d of age. Serum concentrations of alpha-tocopherol were low at birth for both groups of calves and ranged from .83 to 1.08 micrograms/ml of plasma. Hay had less alpha-tocopherol than silage (15 vs. 35 ppm in the DM). Cows fed silage had significantly higher plasma alpha-tocopherol concentrations (3.41 micrograms/ml) than cows fed hay (2.25 micrograms/ml). Cows given one subcutaneous injection of Se plus alpha-tocopherol preparation had significantly higher Se concentration in plasma (30 ng/ml) than did cows in the control group (17 ng/ml). The Se concentration in the placenta of cows that were injected with the Se preparation was significantly higher (64 ppm) than that in the control (47 ppm). Plasma Se concentration of calves at birth was correlated significantly with that of dams soon after parturition.

Animal Feed↗