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INTERPRETIVE SUMMARY

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

RUNNING HEAD: FEEDING HIGH 9 CORN SILAGE DIETS

Effect of Feeding High Corn Silage 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 – Agricultural Research Service, Madison

¹ Trade names and the names of commercial companies are used in this report to provide specific information. Mention of a trade name or manufacturer does not constitute a guarantee or warranty of the product by the USDA or an endorsement over products not mentioned.

² Corresponding author: Vinicius R. Moreira, Louisiana State University Agricultural Center Southeast Research Station, 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 as a treatment. Twenty multiparous and 4 primiparous Holstein cows, from early to mid lactation were used 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) and silage (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, can result in large amounts of corn grain in some diet formulations, potentially contributing to increased incidence of rumen acidosis and feet/leg problems.

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

However, alfalfa can be a valuable complement to CS in dairy rations. The complementarity of CS:AS mixtures include agronomical, nutritional and economical reasons. A significant portion of that complementarity relates to the efficiency of nitrogen utilization on the farm. Alfalfa silage complements CS in dairy diets, in that alfalfa is high in protein, particularly RDP. Alfalfa also complements corn in the crop rotation, since it fixes N and can provide other desirable features such as reducing soil erosion and improving soil tilth (Borton et al., 1997; Dhiman and Satter, 1997; Rotz et al., 1999). The growing disparity in cost of production of the two forages has contributed to growing reliance on CS as the predominant dairy forage in many parts of the United States, despite what 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 quantitative understanding of the advantages, if any, of feeding a combination of alfalfa silage 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 to other 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-based diets, but when compared to forage other than AS, increasing the proportion of CS consistently increased 76 milk production and DMI. Studies have also compared CS:AS mixtures and AS alone (Dhiman and Satter, 1997; Krause and Combs, 2003), or evaluated the inclusion of higher proportions of CS:AS mixtures in high-NDF diets (Onetti et al., 2002; Ruppert et al., 2003). Milk production has generally been consistently similar across treatments, while fat yield tended to remain the same or decrease with increasing CS in the diets.

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


MATERIAL AND METHODS

Forages and Diets
Treatments consisted of different proportions of 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 and 25% 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 chopped before mixing in the TMR wagon. Nutrient content of the diets was calculated from individual feed analyses.

Treatment diets were formulated to have similar contents of protein, sufficient to meet NRC (1989) recommendations for 40 kg of milk production. Neutral detergent fiber was limited to 27% of diet DM. Dietary levels of protein were adjusted by replacing high moisture 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 Dairy Forage Research Center Experimental Farm located in Prairie du Sac, WI. The protocol was approved by the Animal Use Committee of the College of Agricultural and Life Sciences, University of Wisconsin-Madison.

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

All cows received BST injections (Posilac, Monsanto Co., St. Louis, MO) every 14 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. Cows were 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 experimental periods. A pre-trial TMR was fed for 14 d before the experimental period. Orts were restricted to 10% of the feed offered (as-fed basis).

Sampling, Laboratory Analyses and Calculations

Feed offered was individually weighed for each feeding. Mangers were cleaned daily before the morning feeding, and orts weighed. Diets, orts and forages were sampled daily and stored frozen. A composite was prepared and sub-sampled weekly. Concentrate ingredients were sampled once every week.

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

Two fresh samples of CS and AS were collected weekly. One was used for DM determination and utilized, along with DM values for high moisture shelled corn, to adjust diets once weekly for changes in DM. The other fresh sample was frozen and later composited by period and analyzed for lactic acid and VFA concentrations with a HPLC [(Varian model 5500, Varian Instrument Group, Walnut Creek, 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 calculate organic matter. Crude protein was determined by combustion in a LECO FP-2000 Nitrogen/Protein Analyzer (Leco Co., St. Joseph, MI), according to AOAC (1990). Fiber was analyzed according to the sequential NDF/ADF analysis utilizing heat-stable amylase and sodium sulfite (Van Soest et al., 1991), modified for 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 (Glen Mills, Clifton, NJ).

Milk production was recorded daily and samples were collected from 4 consecutive milking (p.m. and a.m.) on d 10, 11, 17 and 18 of each period. Milk samples were analyzed for fat, protein, lactose, and SNF by the National Cooperative DHIA (Wisconsin DHIA Laboratory, Appleton, WI). Milk composition was determined by near-infrared analysis in a Fossomatic-605 fitted with a B filter (Foss Electric, 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 free glucose, NDF, and ADF were estimated using an external marker (ytterbium-marked soybean hulls) according to Hartnell and Satter (1979). Fecal grab samples were taken from the rectum during the last 4 d of each period. During the first 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 (1000 and 2200h). Individual samples were dried at 60^oC for 72 h in a forced draft oven. Fecal samples were composited for each cow by period and ground through a 1 mm-screen in a Wiley mill. Feed and fecal samples were analyzed for Yb content 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 the ventral sac from the 4 rumen cannulated cows. Aliquots were taken from the same animal at 0, 2, 3, 6, 9 and 12 h after the morning and afternoon feeding on the last day of each period. Rumen contents were squeezed through a folded cheesecloth, and pH of the fluid fraction immediately measured with a Corning 360i pH meter (Corning Inc., Corning, NY). Twenty milliliters of rumen fluid were preserved in scintillation vials by adding 0.3 mL of 50% (vol/vol) sulfuric acid and stored at –20^oC. Samples were thawed and centrifuged at 30,000-x g for 20 minutes at 4^oC. The supernatant was analyzed for free amino acids and NH3-N, using the alkaline phenol hypoclorite procedure (Broderick and Kang, 1980) in a Dual Channel Lachat Quick Chem 8000 FIA (Lachat Instruments, Milwaukee, WI). Another sample of rumen fluid (10 mL) was added to formic acid (1:1; vol/vol) and stored in scintillation vials at –20^oC. Samples were thawed later and centrifuged at 30,000-x g at 4^oC for 20 minutes. The supernatant was 176 analyzed for 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 day of each period at 1, 4, 8 and 10 h after the morning feeding, and 0, 4, 8 and 10 h after the afternoon feeding. These samples were used to estimate fluctuation in urine pH in relation to time of feeding, and possible relationships with rumen pH. Samples of less than 100 mL of urine were discarded and not used for pH measurements. Fecal samples were collected from the same 16 cows at 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 experiment and at the end of each period.

Statistical Analyses

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

Measurements of rumen fermentation, such as VFA concentrations were 195 summarized by sampling time. The model included treatment, period, time, and interaction between time and treatment. Model for urine pH and feces pH also included square. Cow and cow within period by treatment were included in the random statement. The subject for repeated measures was defined as cow within period. First order autoregressive covariate structure was chosen based on Akaike’s Information Criterion.

Specific contrasts were set to test for linear and quadratic effects of CS:AS proportions, 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 experiment is presented in Table 1.
Table 2 contains the proportions of dietary ingredients and nutrient composition of pre trial and treatment diets. Corn silage and AS had similar NDF content, but AS was higher in ADF. Concentrations of organic acids and pH of the silages indicated normal fermentation in the silos. The NDF and ADF contents of AH were higher than originally intended and affected the corresponding treatment diet. Dietary levels of NDF and ADF were higher and starch plus free glucose were lower with the treatment including AH, although CP and estimated NE_L were similar across 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 and metabolizable 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 predicted DMI of all treatment diets, except that of the ¾CSAH. Because of the lower DMI, the ¾CSAH treatment resulted in negative energy balance (-0.4 Mcal/d) and insufficient MP (-65 g/d) as predicted by the NRC (2001). Mixtures of CS and AS resulted in higher DMI (Table 3) compared to ACS diet (Linear P ≤ 0.006). Little difference was observed between the two CS:AS mixtures (Quadratic P ≤ 0.005). The effect of 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 may not 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 instead of CS. The results of our study, with lower dietary NDF content, and possibly those of Onetti et al. (2002), where a large portion of dietary NDF was supplied by soybean hulls, indicated that intake was reduced in diets when CS was the only 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 mixtures but attributed this effect to the higher quality of alfalfa (Grieve et al., 1980; Atwal and Erfle, 1988). According to Leonardi and Armentano (2003), cows sorted more against longer particles and sorted less when half of the AH was replaced by AS, but it was unrelated to hay quality. Alfalfa hay used in our trial was intended to provide chewing substrate, and therefore it was chopped long. Long chopping alfalfa hay appears to promote sorting against long particles thereby reducing intake by the cows.

Milk production (Table 3) was 2.2 kg greater (Quadratic P ≤ 0.04) for cows fed ¾CSAS and ½CSAS than those fed ACS treatment. Diet ¾CSAH tended (P ≤ 0.10) to support lower milk yield than ¾CSAS, but method of preservation significantly affected production of 3.5% FCM (P ≤ 0.01) or SCM (P ≤ 0.01). Most diets based on mixtures of AS and CS have not been found 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 that RUP (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 lactation fed diets containing high CS:AS mixtures compared with high AS:CS mixtures, regardless of dietary CP content. Krause and Combs (2003) found similar total purine derivatives in the urine of cows fed diets containing 39% AS, or 19.5% AS plus 19.5% CS (dietary DM basis) suggesting similar microbial yield. Higher dietary protein availability associated with CS inclusion in the diets was a direct result of soybean meal increment. Results actually observed for ½CSAS compared to the ¾CSAS suggested that dietary protein content was enough to support the milk production achieved by cows in this study.

Lower DMI probably limited production of cows fed ¾CSAH, although milk production 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 ACS and ½CSAS compared to ¾CSAS (Table 3). Diets based on CS often result 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, coupled with the presence of polyunsaturated fatty acids have been related with milk fat depression (Kalscheur et al., 1997). In this experiment, all diets were marginal 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 fiber levels.
Roasted soybeans were a source of polyunsaturated fatty acids in all diets. Despite differences in NDF and ADF contents of the diets, all treatments had low milk fat content, which supports the possibility that the diet with long, low-quality AH may have had limited intake because of sorting.


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

Feed efficiency was not influenced by CS:AS ratio in the diet, while ¾CSAH improved (P ≤ 0.001) efficiency of feed and nitrogen utilization (Table 4). Efficiencies of feed utilization need to be evaluated with caution in short-term experiments because of the capacity of cows to mobilize body reserves to supply nutrients for milk production. Lower DMI with ¾CSAH could affect body weight and 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 of AS in the diets increased (Table 5). Total VFA and NH3-N content were not influenced by CS:AS levels (P ≤ 0.10). The concentration of total amino acids in 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) by treatment (Table 6). The lowest pH (nadir) of rumen fluid was attained at 6 h after 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 between the 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 treatments were relatively large, they were not significant (P ≤ 0.10). The number of hours during which pH of rumen fluid was below 6.0 was estimated assuming linearity between sampling time-points. The amount of time that rumen fluid pH was below 6.0 tended (P = 0.10) to decrease with the inclusion of AS in the diet. There was no difference between 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 Soest et al., 1991). Rapid acid production and/or reduced cation exchange capacity associated with the ACS diet could contribute to the extended interval of low rumen pH. This effect can impair fiber degradation in the rumen by delaying lag time and rate of digestion (Grant and Mertens, 1992).

Low ruminal pH has long been associated with milk fat depression, and milk fat depression can be partially corrected by addition of buffer to the diet, possibly by 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 was added to diets based on CS as the sole forage source and remained high in diets 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 similar rate 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 despite the addition of 0.7% (DM basis) sodium bicarbonate. The rate of passage of rumen 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 among treatments (Table 6). There was a significant (P ≤ 0.008) interaction between time and treatment indicating larger fecal pH fluctuation with the ACS than with CS:AS treatments (Figure 1).

Inclusion of CS significantly reduced (P ≤ 0.01) mean urinary pH (Table 6), but did not result in urinary pH outside of normal range (7.5 to 8.5). Goff and Horst (1998) fed dry cows with CS alone, or supplemented with potassium carbonate or 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 excretion of protons, such as ammonium, and decrease bicarbonate in the urine in an attempt to maintain a constant ionic balance in the body. Peaks of urinary pH 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 fluctuation in 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) increased dry matter intake and milk yield when compared to either corn silage as the only source of forage, or corn silage supplemented with low-quality alfalfa hay.





Table 1. Nutrient 445 composition of forages.






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





¹ Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 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 ppm Mn, 2.4 × 103 ppm Fe, 1.3 × 103 ppm Cu, 43.1 ppm Co, 320 ppm Se, 7.1 × 106 IU/kg vitamin A, 2.2 × 106 IU/kg vitamin D, and 1.8 × 106 IU/kg vitamin E.

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



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



¹ Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 50% alfalfa silage.

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

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

⁴ SCM = 12.3 × (fat yield) + 6.56 × (solids non-fat yield) – 0.0752 × (milk yield).



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



¹ Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effect of 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 different proportions of corn silage.



¹ Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 50% alfalfa silage.

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

³ TAA = total amino acids.


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



¹ Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 50% alfalfa silage.

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

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


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



1 Treatment diets contained 50% forage and 50% concentrates. Treatments are described by 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 silage and 50% alfalfa silage.

² L = linear effect of CS:AS; Q = quadratic effect of 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 Research Service, Madison







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