corn silage effects for dairy cattle

INTERPRETIVE SUMMARY

Corn and alfalfa are among the forages most commonly fed to lactating dairycows because of agronomical, nutritional and economical reasons. Large dairyfarms are increasingly feeding corn silage as their main forage source. In thisstudy, cows fed mixtures of corn silage and alfalfa silage had higher feed intakeand milk production compared to cows offered corn silage as the only sourceof forage, or offered corn silage with low-quality alfalfa hay.

RUNNING HEAD: FEEDING HIGH 9 CORN SILAGE DIETS

Effect of Feeding High CornSilage Diets to Dairy Cows¹

V. R. Moreira^*,2, C. Cragnolino*, and L. D. Satter^*,†
* Department of Dairy Science, University of Wisconsin,and
^† U.S. Dairy Forage Research Center, USDA – AgriculturalResearch Service, Madison

¹ Trade names and the names of commercial companies are used in thisreport to provide specific information. Mention of a trade name or manufacturerdoes not constitute a guarantee or warranty of the product by the USDA or anendorsement over products not mentioned.

² Corresponding author: Vinicius R.Moreira, Louisiana State University Agricultural Center Southeast ResearchStation, Highway 16 West, P.O. Drawer 567, Franklinton, LA.


ABSTRACT

The objective of this experiment was to evaluate the effect of corn silage(CS): alfalfa silage (AS) ratio in 50:50 forage:concentrate diets on production and rumen traits of dairy cows.
Method of alfalfa preservation, whether as silage or hay, was included asa treatment. Twentymultiparous and 4 primiparous Holstein cows, from early to mid lactation wereused in this experiment. Four of the multiparous cows had rumen cannulas. Treatments were randomly distributed among the cows in a Latin square design after blocking for parity and rumen cannulae. Treatments were 100% CS (ACS), 75% CS and 25% low-quality alfalfa hay (¾CSAH), 75% CS and 25% AS (¾CSAS), and 50% CS and 50% AS (½CSAS)in the forage portion of the diet. Soybean meal replaced high moisture shelled corn to adjust dietary crude protein. Dry matter intake responded quadratically (P ≤ 0.005), and ranged from 23.4 with ACS to 24.7 and 24.3 kg/d with the inclusion of AS in the diet. Milk yield had a similar response to that of DMI, 39.4 kg/d with ACS versus 40.6 kg/d with CS:AS mixtures. Fat, lactose and SNF yields were lower (P ≤ 0.04), while protein yield tended (P ≤ 0.06) to increase with the ACS diet. Substituting low-quality AH for AS in a CS based diet resulted in lower (P ≤ 0.02) intake and fat yield and cows tended (P ≤ 0.10) to produce less milk yield, lactose and SNF. Concentrations of acetate and butyrate in rumen fluid were not influenced by method of preservation, but were linearly (P ≤ 0.02) reduced and propionate was increased by ACS inclusion. All diets resulted in rumen pH averaging 6.0. Urinary pH was significantly higher with the inclusion of alfalfa in the diets, but differences were small.The ACS diet resulted in lower ADF digestibility (38.9% vs. 45.6%). It is concluded that CS:AS mixtures support better performance of lactating cows than feeding corn silage as the sole forage. (Keywords: corn silage, alfalfa, milk, dairy cow)

INTRODUCTION

The use of corn silage (CS) in dairy diets, relative to alfalfa hay (AH) andsilage (AS), has increased in some parts of the United States in recent years.This, combined with greater inclusion of corn grain in the dairy diet, canresult in large amounts of corn grain in some diet formulations, potentiallycontributing to increased incidence of rumen acidosis and feet/leg problems.

Corn silage is an economical source of energy, is highly palatable, and has highproductivity per hectare (Grieve et al., 1980; Phipps et al., 1992; Dhiman andSatter, 1997). These characteristics make CS a desirable forage source particularlywhere there is marginal availability of land for growing feed.

However, alfalfa can be a valuable complement to CS in dairy rations. The complementarityof CS:AS mixtures include agronomical, nutritional and economical reasons.A significant portion of that complementarity relates to the efficiency of nitrogenutilization on the farm. Alfalfa silage complements CS in dairy diets, in thatalfalfa is high in protein, particularly RDP. Alfalfa also complements cornin the crop rotation, since it fixes N and can provide other desirable featuressuch as reducing soil erosion and improving soil tilth (Borton et al., 1997;Dhiman and Satter, 1997; Rotz et al., 1999). The growing disparity in costof production of the two forages has contributed to growing reliance on CSas the predominant dairy forage in many parts of the United States, despitewhat appears to be advantages for including some alfalfa in CS based dairy diets(Borton et al., 1997; Rotz et al., 1999). There is need for a better quantitativeunderstanding of the advantages, if any, of feeding a combination of alfalfasilage or hay with CS.

Studies have compared CS and AS as the sole source of forage in dairy diets(Broderick, 1985; Wattiaux et al., 1991), and CS or AS have been compared toother forages (Phipps et al., 1992; Phipps et al., 1995; O’Mara et al.,1998). Milk production and intake have been similar between CS and AS-baseddiets, but when compared to forageother than AS, increasing the proportion of CS consistently increased 76 milkproduction and DMI. Studies have also compared CS:AS mixtures and AS alone(Dhiman and Satter, 1997; Krause and Combs, 2003), or evaluated the inclusionof higher proportions of CS:AS mixtures in high-NDF diets (Onetti et al., 2002;Ruppert et al., 2003). Milk production has generally been consistently similaracross treatments, while fat yield tended to remain the same or decrease withincreasing CS in the diets.

The objectives of this experiment were to evaluate the effect of higher proportionsof CS in relation to AS, and to compare AS or AH as a forage source in high CSdiets, on production and rumen fermentation characteristics of high producingdairy cows fed diets containing 50:50 forage to concentrate ratio (DM basis).


MATERIAL AND METHODS

Forages and Diets
Treatments consisted of different proportionsof CS and alfalfa (silage or hay) in diets that contained 50% forage and 50%concentrate (DM basis). Treatments were: 100% CS (all CS; ACS); 75% CS and25% AS (¾CSAS); and 50% CS and 50% AS(½CSAS).
A fourth treatment included 75% CS and 25% low-quality AH (¾CSAH).

The corn variety used for silage was Dairyland Forecast 3,000 (Dairyland Seeds,West Bend, WI). Corn was harvested between ½ and ¾ milk line,chopped at a theoretical length of cut of 9.5 mm, and stored in a tower silo.Alfalfa silage was stored in a bunker silo. Low-quality AH was coarsely choppedbefore mixing in the TMR wagon. Nutrient content of the diets was calculatedfrom individual feed analyses.

Treatment diets were formulated to have similar contents of protein, sufficientto meet NRC (1989) recommendations for 40 kg of milk production. Neutral detergentfiber was limited to 27% of diet DM. Dietary levels of protein were adjustedby replacing highmoisture shelled corn with soybean meal as dietary CS content was increased(Table 1).

Animals and Management

This experiment was carried out in the facilities of the USDA-ARS US DairyForage Research Center Experimental Farm located in Prairie du Sac, WI. The protocolwas approved by the Animal Use Committee of the College of Agricultural and LifeSciences, University of Wisconsin-Madison.

Twenty-four Holstein cows (36 ± 4.67 kg milk/d; 139 ± 49 DIM) wereused in 4 x 4 Latin square design with 21 d periods. Sixteen multiparous and4 primiparous early lactation cows, plus 4 multiparous mid-lactation cowsfitted with rumen cannulae, were distributed among 6 squares according toparity, rumen cannula, and milk production measured during the pre-trial.Treatments were randomly distributed to cows within each square. Each periodconsisted of 7 d for diet adaptation and 14 d for collecting data on milkproduction and DMI. Rumen fluid, urine and feces were sampled during the last7 d of each period.

All cows received BST injections (Posilac, Monsanto Co., St. Louis, MO) every14 d, with 12 cows injected each week (3 out of 6 allotted in each treatment)to maintain balance in treatment interval relative to period length. Cowswere housed in a tie-stall barn and milked twice daily.

Cows were fed a TMR twice daily every 12 h during the pre-trial and experimentalperiods. A pre-trial TMR was fed for 14 d before the experimental period. Ortswere restricted to 10% of the feed offered (as-fed basis).

Sampling, LaboratoryAnalyses and Calculations

Feed offered was individually weighed for each feeding. Mangers were cleaneddaily before the morning feeding, and orts weighed. Diets, orts and forages weresampled daily and stored frozen. A composite was prepared and sub-sampledweekly. Concentrateingredients were sampled once every week.

Feed DM was determined in a forced air 60oC oven for 48 h. Dry samples wereground through a 1-mm screen in a Wiley mill (Arthur H. Thomas, Philadelphia,PA).
Ground concentrate samples were composited by period before chemicalanalyses. Forages were analyzed as weekly composites.

Two fresh samples of CS and AS were collected weekly. One was used for DMdetermination and utilized, along with DM values for high moisture shelled corn,to adjust diets once weekly for changes in DM. The other fresh sample wasfrozen and later composited by period and analyzed for lactic acid and VFAconcentrations with a HPLC [(Varian model 5500, Varian Instrument Group, WalnutCreek, CA) (Muck, 1987)].

Nutrient composition was calculated based on DM determined at 105^oC for 8 h.
Total ash was determined after 16 h in a 550^oC ashing-oven and used to calculateorganic matter. Crude protein was determined by combustion in a LECO FP-2000Nitrogen/Protein Analyzer (Leco Co., St. Joseph, MI), according to AOAC (1990).Fiber was analyzed according to the sequential NDF/ADF analysis utilizingheat-stable amylase and sodium sulfite (Van Soest et al., 1991), modifiedfor the Ankom200 Fiber Analyzer (Ankom Technology, Fairport, NY).

Starch plus free glucose was analyzed by an enzymatic assay (Bal et al., 2000)in samples ground through 0.25mm-screen in an ultra cetrifugal mill (GlenMills, Clifton, NJ).

Milk production was recorded daily and samples were collected from 4 consecutivemilking (p.m. and a.m.) on d 10, 11, 17 and 18 of each period. Milk samples wereanalyzed for fat, protein, lactose, and SNF by the National Cooperative DHIA(Wisconsin DHIA Laboratory, Appleton, WI). Milk composition was determinedby near-infrared analysis in a Fossomatic-605 fitted with a B filter (FossElectric, Hillerød,Denmark).

Weekly milk composition and yield were used to calculate 3.5% FCM and SCM(Tyrrell and Reid, 1965).

Apparent digestibility coefficients for DM, organic matter, starch plus freeglucose, NDF, and ADF were estimated using an external marker (ytterbium-markedsoybean hulls) according to Hartnell and Satter (1979). Fecal grab sampleswere taken from the rectum during the last 4 d of each period. During thefirst 24 h of sampling, fecal samples (~100 g
each) were collected every 3 h (0200, 0500, 0800, 1100, 1400, 1700, 2000,and 2300h).
Fecal samples were obtained every 12 h for the next 3 d (1000and 2200h). Individual samples were dried at 60^oC for 72 h in a forced draftoven. Fecal samples were composited for each cow by period and ground througha 1 mm-screen in a Wiley mill. Feed and fecal samples were analyzed for Ybcontent by direct current plasma emission spectroscopy in a Spectospan V Spectrometer(Beckman Instruments, Arlington Heights, IL) according to Combs and Satter (1992).

Grab-samples of rumen content were collected from 5 different locations in theventral sac from the 4 rumen cannulated cows. Aliquots were taken from the sameanimal at 0, 2, 3, 6, 9 and 12 h after the morning and afternoon feeding onthe last day of each period. Rumen contents were squeezed through a foldedcheesecloth, and pH of the fluid fraction immediately measured with a Corning360i pH meter (Corning Inc., Corning, NY). Twenty milliliters of rumen fluidwere preserved in scintillation vials by adding 0.3 mL of 50% (vol/vol) sulfuricacid and stored at –20^oC. Samples werethawed and centrifuged at 30,000-x g for 20 minutes at 4^oC. The supernatantwas analyzed for free amino acids and NH3-N, using the alkaline phenol hypocloriteprocedure (Broderick and Kang, 1980) in a Dual Channel Lachat Quick Chem 8000FIA (Lachat Instruments, Milwaukee, WI). Another sample of rumen fluid (10mL) was added to formic acid (1:1; vol/vol) and stored in scintillation vialsat –20^oC. Samples were thawedlater andcentrifuged at 30,000-x g at 4^oC for 20 minutes. The supernatant was 176 analyzedfor volatile fatty acids (VFA) using a gas chromatograph (Varian Vista 6000;Varian Instrument Group) according to Brotz and Schaefer (1987).

Urine samples were collected from 16 cows by vulva stimulation on the last dayof each period at 1, 4, 8 and 10 h after the morning feeding, and 0, 4, 8and 10 h after the afternoon feeding. These samples were used to estimatefluctuation in urine pH in relation to time of feeding, and possible relationshipswith rumen pH. Samples of less than 100 mL of urine were discarded and notused for pH measurements. Fecal samples were collected from the same 16 cowsat 0, 6 and 10 h after the morning feeding and 4 h after the afternoon feeding.Fecal pH was estimated after feces were diluted 50:50 (w:v) with deionized water.Animals were weighed for 2 consecutive days at the beginning of the experimentand at the end of each period.

Statistical Analyses

Statistical analyses used mixed procedures of SAS 8.2 (SAS, 1999) for a 4x 4 Latin square design. Production traits were summarized by week. The modelincluded treatment, period, square, week, and interactions between treatmentand square, treatment and period, square and period, and week and treatment.Cow within square and treatment by period by cow within square were includedin the random statement.

Measurements of rumen fermentation, such as VFA concentrations were195 summarized by sampling time. The model included treatment, period, time,and interaction between time and treatment. Model for urine pH and feces pHalso included square. Cow and cow within period by treatment were includedin the random statement. The subject for repeated measures was defined ascow within period. First order autoregressive covariate structure was chosenbased on Akaike’s Information Criterion.

Specific contrasts were set to test for linear and quadratic effects of CS:ASproportions, and method of alfalfa preservation (¾CSAS vs. ¾CSAH). Significance was declared at P ≤ 0.05, and trends assumed at 0.05 < P ≤ 0.10.


RESULTS AND DISCUSSION

Forages and Diets

Nutrient composition of the forages used in this experimentis presented in Table 1.
Table 2 contains the proportions of dietary ingredientsand nutrient composition of pretrial and treatment diets. Corn silage and AS had similar NDF content, but ASwas higher in ADF. Concentrations of organic acids and pH of the silages indicatednormal fermentation in the silos. The NDF and ADF contents of AH were higherthan originally intended and affected the corresponding treatment diet. Dietarylevels of NDF and ADF were higher and starch plus free glucose were lowerwith the treatment including AH, although CP and estimated NE_L were similaracross treatments.

Evaluations of the treatment diets using the NRC (2001) model, at predicted intake(24.3 kg/d), indicated that experimental diets supplied the recommended NE_L andmetabolizable protein (MP), except for cows on diet ½CSAS.This diet was deficient by 45 g/d of MP.

Animal Performance

The NRC (2001) model accurately predictedDMI of all treatment diets, except that of the ¾CSAH. Because of thelower DMI, the ¾CSAH treatmentresulted in negative energy balance (-0.4 Mcal/d) and insufficient MP (-65g/d) as predicted by the NRC (2001). Mixtures of CS and AS resulted in higherDMI (Table 3) compared to ACS diet (Linear P ≤ 0.006). Little difference wasobserved between the two CS:AS mixtures (Quadratic P ≤ 0.005). The effectof CS:AS mixtures on intake as reported in the literature has been variable.Intake of CS:AS mixture was similar to a diet based on AS alone(Dhiman and Satter, 1997; Krause and Combs, 2003), or when rumen fill maynot have been limiting (Belyea et al., 1974). A study with high-NDF diets(Ruppert et al., 2003) found greater DMI with a higher proportion of AS insteadof CS. The results of our study, with lower dietary NDF content, and possiblythose of Onetti et al. (2002), where a large portion of dietary NDF was suppliedby soybean hulls, indicated that intake was reduced in diets when CS was theonly source of forage.

Including high-NDF AH in a high-CS diet reduced intake by 13.4% compared to ¾CSAS.Other researchers have found similar results when comparing CS to CS:AH mixturesbut attributed this effect to the higher quality of alfalfa (Grieve et al., 1980;Atwal and Erfle, 1988). According to Leonardi and Armentano (2003), cows sortedmore against longer particles and sorted less when half of the AH was replacedby AS, but it was unrelated to hay quality. Alfalfa hay used in our trialwas intended to provide chewing substrate, and therefore it was chopped long.Long chopping alfalfa hay appears to promote sorting against long particlesthereby reducing intake by the cows.

Milk production (Table 3) was 2.2 kg greater (Quadratic P ≤ 0.04) for cowsfed ¾CSAS and ½CSAS than those fed ACS treatment. Diet ¾CSAHtended (P ≤ 0.10) to support lower milk yield than ¾CSAS, but methodof preservation significantly affected production of 3.5% FCM (P ≤ 0.01) orSCM (P ≤ 0.01). Most diets based on mixtures of AS and CS have not beenfound to affect milk yield when compared to AS-based diets (Dhiman and Satter,1997; Krause and Combs, 2003) or CS-based diet (Onetti et al., 2002).

Diet assessment with the NRC (2001) model, using actual intake, suggested thatRUP (Table 2) limited milk yield in the ½CSAS compared to the ¾CSAS.Wattiaux and Karg (2004) found milk yield to increase with cows in early lactationfed diets containing high CS:AS mixtures compared with high AS:CS mixtures,regardless of dietary CPcontent. Krause and Combs (2003) found similar total purine derivatives inthe urine of cows fed diets containing 39% AS, or 19.5% AS plus 19.5% CS (dietaryDM basis) suggesting similar microbial yield. Higher dietary protein availabilityassociated with CS inclusion in the diets was a direct result of soybean mealincrement. Results actually observed for ½CSAS compared to the ¾CSASsuggested that dietary protein content was enough to support the milk productionachieved by cows in this study.

Lower DMI probably limited production of cows fed ¾CSAH, although milkproduction in that treatment was 1.2 kg/d higher than that of the ACS treatment(not compared statistically), despite reduced DMI.

Fat content was low for all treatments, but not significantly different (P≤ 0.10). Fat yield was lower (Quadratic P ≤ 0.003) in the milk of cows fed ACSand ½CSAS compared to ¾CSAS (Table 3). Diets based on CS oftenresult in low milk fat percentage (e.g., Broderick, 1985; Dhiman and Satter,1997; Wattiaux and Karg, 2004). Diets rich in starch and poor in fiber, coupledwith the presence of polyunsaturated fatty acids have been related with milkfat depression (Kalscheur et al., 1997). In this experiment, all diets weremarginal in NDF and were high in starch (measured as starch plus free glucose)levels, except for the treatment containing low-quality AH which had higher fiberlevels.
Roasted soybeans were a source of polyunsaturated fatty acids in alldiets. Despite differences in NDF and ADF contents of the diets, all treatmentshad low milk fat content, which supports the possibility that the diet withlong, low-quality AH may have had limited intake because of sorting.


Milk protein content increased linearly (P ≤ 0.02) with increased CS in thediet.
Milkprotein content has been consistently similar or lower when cows are fed dietsbased on AS compared to diets containing higher proportions of CS (Voss etal., 1988; Krause and Combs, 2003). Protein yield tended (Quadratic P ≤ 0.06)to be higher with theinclusion of alfalfa in the diet, regardless of preservation method. Lactosewas not significantly altered by treatments, but SNF tended (P ≤ 0.07) toincrease linearly with dietary CS content.

Feed efficiency was not influenced by CS:AS ratio in the diet, while ¾CSAHimproved (P ≤ 0.001) efficiency of feed and nitrogen utilization (Table 4). Efficienciesof feed utilization need to be evaluated with caution in short-term experimentsbecause of the capacity of cows to mobilize body reserves to supply nutrientsfor milk production. Lower DMI with ¾CSAH could affect body weightand ultimately limit production if fed for a longer term.


Rumen Fermentation and pH Measurements

Rumen fermentation. Acetate and butyrate content (mM and M%) were increased(P ≤ 0.02) and propionate decreased (P ≤ 0.02) linearly as the proportion ofAS in the diets increased (Table 5). Total VFA and NH3-N content were notinfluenced by CS:AS levels (P ≤ 0.10). The concentration of total amino acidsin the rumen fluid tended (P ≤ 0.09) to increase with AS content in the diet.

pH measurements. Mean daily pH of rumen fluid was not affected(P ≤ 0.10) bytreatment (Table 6). The lowest pH (nadir) of rumen fluid was attained at 6 hafter the morning feeding and 3 h after the afternoon feeding (Figure 1).On average, rumen fluid pH nadir tended (P = 0.10) to show a quadratic effect.The fluctuation in pH (Table 6) was measured as the average difference betweenthe daily high and low in pH for rumen fluid, feces and urine (Figure 1).Although differences in daily fluctuation in pH of rumen fluid among treatmentswere relatively large, they were not significant (P ≤ 0.10). The number ofhours during which pH of rumen fluid was below 6.0 was estimated assuming linearitybetween sampling time-points. The amount of time that rumen fluid pH was below6.0 tended (P = 0.10) to decrease with the inclusion of AS in the diet. Therewas no differencebetween AS and AH (Table 6). Saliva production, and consequently 301 rumen buffering,is stimulated by the chewing of long particles during rumination (Allen, 1997).Also, cation exchange capacity can affect buffering capacity in the rumen.Cation exchange capacity of CS is about one third that of alfalfa (Van Soestet al., 1991). Rapid acid production and/or reduced cation exchange capacityassociated with the ACS diet could contribute to the extended interval oflow rumen pH. This effect can impair fiber degradation in the rumen by delayinglag time and rate of digestion (Grant and Mertens, 1992).

Low ruminal pH has long been associated with milk fat depression, and milk fatdepression can be partially corrected by addition of buffer to the diet, possiblyby reducing the flow of trans fatty acids to the duodenum (Emery and Brown,1961; Kalscheur et al., 1997; Griinari et al., 1998). Onetti et al. (2004)observed increased omasal flow (g/d) of cis- and trans-C18:1 when tallow wasadded to diets based on CS as the sole forage source and remained high indiets containing CS:AS or CS:AH mixtures plus tallow. Ruppert et al. (2003)observed a higher dilution rate and outflow of rumen fluid, but found a similarrate of passage for particulate matter, with 40:10 CS:AS compared to 10:40 CS:AS.Milk fat content and yield was low for all treatments in our study despitethe addition of 0.7% (DM basis) sodium bicarbonate. The rate of passage ofrumen liquid fraction may be increased even under mildly acidic rumen conditions.Under such conditions, enough trans fatty acids may be available for absorption,thus limiting milk fat synthesis by the mammary gland.

Mean, nadir and daily fluctuation of fecal pH did not differ statistically amongtreatments (Table 6). There was a significant (P ≤ 0.008) interaction betweentime and treatment indicating larger fecal pH fluctuation with the ACS thanwith CS:AS treatments (Figure 1).

Inclusion of CS significantly reduced (P ≤ 0.01) mean urinary pH (Table 6),butdid not result in urinary pH outside of normal range (7.5 to 8.5). Goff andHorst (1998) fed dry cows with CS alone, or supplemented with potassium carbonateor hydrochloric acid, and measured urinary pH values of 7.33, 8.22 and 5.92,respectively. To cope with metabolic acidosis, cows tend to increase excretionof protons, such as ammonium, and decrease bicarbonate in the urine in anattempt to maintain a constant ionic balance in the body. Peaks of urinarypH tended to occurred 2 to 4 h after the nadir in rumen pH (Figure 1).

Apparent Digestibility Coefficients

Nutrient digestibility was not affected by treatment, except for a linear(P ≤ 0.05) increase in ADF digestibility when alfalfa was included in the diets, regardless of method of preservation (Table 7). Similar patterns have been noted elsewhere (Krause and Combs, 2003; Ruppert et al., 2003). Cellulolytic activity is decreased when rumen pH is below 6.0 (Grant and Mertens, 1992). Allen (1997) suggested that daily fluctuation in pH as well as mean pH must be considered when evaluating the impact of rumen pH on milk fat. In our study, the amount of time that rumen pH was below 6.0 and the daily fluctuationin rumen pH were closely related. The oscillating pattern of low rumen fluid pH, despite the supplementation of all diets with sodium bicarbonate, probably alternated depression and recovery of the cellulolytic bacteria resulting in lower fiber digestion, particularly when CS was the only source of forage in the diet (Figure 2).


CONCLUSIONS

The addition of alfalfa silage to corn silage-based diets containing 17.5% crude protein and 50:50 forage to concentrate ratio (dry matter basis) increaseddry matter intake and milk yield when compared to either corn silage as theonly source of forage, or corn silage supplemented with low-quality alfalfahay.





Table 1. Nutrient 445 composition of forages.






Table 2. Feed ingredients and nutrient composition of pre-446 trial and treatmentdiets.





¹ Treatment diets contained 50% forage and 50% concentrates. Treatmentsare described by the amount of test forage as a fraction of total forage.ACS = 100% corn silage, ¾CSAH = 75% corn silage and 25% low-qualityalfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² HMSC = High moisture shelled corn.

³ Vitamin-mineral supplement:19.4% Ca, 5.51% S, 6.2 × 103 ppm Zn,5.1 × 103 ppmMn, 2.4 × 103 ppm Fe, 1.3 × 103 ppm Cu, 43.1ppm Co, 320 ppm Se, 7.1 × 106 IU/kg vitamin A, 2.2 × 106 IU/kgvitamin D, and 1.8 × 106 IU/kg vitaminE.

⁴ RUP and NEL calculated based on NRC (2001) tabular values for individualfeedstuffs.



Table 3. Effect of feeding lactating cows with different proportions 458 of cornsilage and alfalfa silage or hay on dry matter intake, milk production andmilk composition.



¹ Treatment diets contained 50% forage and 50% concentrates. Treatmentsare described by the amount of test forage as a fraction of total forage.ACS = 100% corn silage, ¾CSAH = 75% corn silage and 25% low-qualityalfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effectof CS:AS; and MP = method of alfalfa preservation.

³ 3.5% FCM = (0.432 × milkyield) + (16.2 × fat yield).

⁴ SCM = 12.3 × (fat yield) + 6.56 × (solidsnon-fat yield) – 0.0752 × (milkyield).



Table 4. Effect of feeding lactating cows with different proportions 468 of cornsilage and alfalfa silage or hay on feed and nitrogen efficiency.



¹ Treatment diets contained 50% forage and 50% concentrates. Treatmentsare described by the amount of test forage as a fraction of total forage.ACS = 100% corn silage, ¾CSAH = 75% corn silage and 25% low-qualityalfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effectof CS:AS; and MP = method of alfalfa preservation.

³ N intake = dietary CP% x DMI / 6.25.

⁴ Milk N = milk CP yield / 6.38.



Table 5. Volatile fatty acid content of rumen fluid from cows fed 478 differentproportions of corn silage.



¹ Treatment diets contained 50% forage and 50% concentrates. Treatmentsare described by the amount of test forage as a fraction of total forage.ACS = 100% corn silage, ¾CSAH = 75% corn silage and 25% low-qualityalfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effectof CS:AS; MP = method of alfalfa preservation; and t*trt = interaction betweentime and treatment.

³ TAA = total amino acids.


Table 6. pH measurements of rumen fluid, feces and urine 487 from cows fed differentproportions of corn silage and alfalfa silage or hay.



¹ Treatment diets contained 50% forage and 50% concentrates. Treatmentsare described by the amount of test forage as a fraction of total forage.ACS = 100% corn silage, ¾CSAH = 75% corn silage and 25% low-qualityalfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effectof CS:AS; MP = method of alfalfa preservation; and t*trt = interaction betweentime and treatment.

³ Fluctuation in pH was measured as the difference betweendaily high and low in pH for rumen fluid, feces and urine.


Table 7. Apparent digestibility coefficients in lactating 497 cows fed differentproportions of corn silage and alfalfa silage or hay.



1 Treatment diets contained 50% forage and 50% concentrates. Treatments are describedby the amount of test forage as a fraction of total forage. ACS = 100% corn silage, ¾CSAH= 75% corn silage and 25% low-quality alfalfa hay, ¾CSAS= 75% corn silage and 25% alfalfa silage, and ½CSAS = 50% corn silageand 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effectof CS:AS; and MP = method of alfalfa preservation.



Figure 1 - Effect of High Corn Silage Diets on Milk Production






Figure 2 - Effect of High Corn Silage Diets on Milk Production







V. R. Moreira^*,2, C. Cragnolino^*, and L. D. Satter*^,†
* Department of Dairy Science, University of Wisconsin, and
^†U.S.Dairy Forage Research Center, USDA – Agricultural ResearchService, Madison







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