Feeding Value of High Dry Matter Corn Silage for Dairy Cattle 1 M. J. OWENS, ~ N. A. JORGENSEN, and H. H. VOELKER
Dairy Science Department, South Dakota State University, Brookings
nutrients can occur when corn plants with a low dry matter content are ensiled (1, 13). The exact stage of maturity at which to harvest the corn plant for maximum nutrient value and yield is still in question. I-Iuber et M. (10) compared the feeding value of corn silage harvested with 25.4 and 33.3% dry matter content. Dry matter intake and milk production were higher with the more mature silage. Byers and Ormiston (5) reported greater dry matter intake of mature corn silage (54.9% DM) than of normal corn silage (31.5% DI~[), and no difference in milk production. Gordon et M. (9) did not find a consistent trend in dry matter intake in two trials comparing normal silage (26.3 to 32.4% DM) with late-harvested corn silage (58.2 to 60.0% DM). Milk production was slightly lower for cows fed late-harvested corn silage. Both groups (5, 9) reported greater field losses and lower digestibility of nutrients for mature or late-harvested corn silage. The objective of this study was to compare acreage yields and nutritive value, for lactating cows, of corn silages harvested at high ( > 4 2 % , H D M C S ) and medium (32-42%, MDMCS) dry matter levels.
Two feeding trials using 20 cows each compared high dry matter corn silage (HDMCS) with corn silage of medium dry matter content (MDMCS). A continuous design was employed in Trim I and a double-reversM d e s i ~ in Trial I I . The high d r y matter corn silage was ground before ensiling and both silages stored in gas-tight units. Significant differences associated with the harvesting of high dry matter corn silage when compared with the medium dry silage include: lower dry matter yields; greater field dry matter losses; higher percentage of ear losses; lower carotene content; lower total acid concentration during fermentation; and a higher pH. Voluntary dry matter consumption, milk production, and body weight gains were greater for cows fed the high dry matter corn silage, but differences were significant only for Trial II. There were no significant differences in per cent milk fat or solids-not-fat between treatments. No consistent difference in chemical composition of the silages between years was found. The digestibility of the dry matter, energy, and protein for the medium and high dry matter silages was 66.9, 66.7, and 54.7; and 64.7, 65.4, and 51.1%, respectively. The silages were nearly equal in feed value; however, the disadvantages suggest that general recommendations for delaying harvest were not warranted.
Traditionally, whole plant corn silage has been ensiled in the early dent stage or when the plant contains less than 30-32% dry matter. Research has shown that losses up to 27.8% of the total dry matter and 43.5% of the total Received for publication March 4, 1968. 1 Published with the approval of the Director of the South Dakota Agricultural Experiment Station as Publication no. 805 of the Journal Series. 2 This paper is part of a thesis submitted by the senior author in partial fulfillment of the requirements for the M.S. degree at South Dakota State University.
Silages. A 9.7 ha field of well-eared hybrid yellow corn was divided into six plots of 1.5 ha each. Three of the plots were harvested as MDMCS and three as t I D M C S in each of two successive years: 1965 (Trial I ) and 1966 (Trial I I ) . A conventional field chopper was used for harvesting each plot. Preliminary investigations revealed that H D M C S ensiled without regrinding resulted in separation of plant parts in the silo and selection of plant parts when fed to cows. Thus, the t t D M C S was ground with a hammermill using a 2.5- to 3.8-cm screen before ensiling. Both silages were stored in gas-tight units. Yields were determined by weighing the total material harvested from each plot. Each load was sampled separately for dry matter content. Field losses were determined by weighing all of the material remaining on the ground in a 5.94-sq m area after harvest and sampling each area for dry matter content. Samples were collected at 61-m intervals with and against pre-
SILAGE FOR CATTLE vailing winds. Ear losses in Trial I I were estimated by counting ears on the stalks and ground before harvest and on the ground after harvest within the same area for each hal-test date. Thirty areas 2.13 by 91.4 m were sampled within each plot. Trial I. Twenty Holstein cows were used in a continuous design according to Lucas (12), using a 21-day standardization period, a 119day experimental period, and a 14-day postexperimental period. Covariance analysis based on the standardization was used to adjust for differences between groups at the start of treatment. During standardization all animals were fed 4.5 kg of alfalfa hay, MDMCS ad libitum, and a 13.7% crude protein (Table 2) grain mixture at the rate of 1 kg for each 2.5 kg of 4% FCM produced. Three-year-old animals were given an additional 0.9 kg of grain daily. Grain was adjusted at seven-day intervals. A mineral mixture of two parts dicalcium phosphate to one part trace-mineralized salt was offered free choice. After standardization, cows were paired for milk yield, stage of lactation TABLE 1. Field yields and losses of corn harvested for silage at two stages of maturity. Yield per hectare
Dry matter loss
6.9 17.6 ~
38.3 11,021 64.0*~ 5,910~
II 5.0 25.4*~
** Significantly (P < .01) different from the corresponding MDMCS mean within a triM.
and age, and one cow from each pair assigned at random to each treatment (MDMCS or HDMCS). Alfalfa hay and grain were fed at the same levels as during standardization. Grain adjustments were made every 14 days. Feedstuffs were fed twice daily and weighbacks taken once daily. All feeds were sampled weekly. Proximate analyses were conducted on ovendried samples (48 C for 48 hr) and carotene and nitrogen on fresh samples according to AOAC methods (2). The concentration of volatile fatty acid in the silage was determined by gas-liquid chromatography (4), lactic acid by a colorimetric method (3), and p H with a conventional glass electrode p H meter. Milk was weighed daily with milk fat (Babcock procedure) and solids-not-fat (8) tests conducted weekly on a composite sample of the A~ and P~ milkings. Each cow was weighed for three successive days at the beginning of the experiment and at the end of Weeks 4, 8, 12, and 17. Trial I I . Feeding value was measured in a double-reversal-designed triM, using 20 Holstein cows. All cows were accustomed to corn silage as their only roughage for 21 days before treatment began. Procedures used were similar to Trial I, except that the grain mixture contained 20.3% crude protein (Table 2) and was fed at the rate of I kg for each 3 kg of 4% FC1V[ produced. Milk samples for composition measurements were collected during Weeks 1, 3, and 5. Animals were weighed on three consecutive days at the beginning and end of each period. F o u r Holstein steers were fed the forages in three total-collection digestion trials conducted simultaneously with Trial II. The length of each trial was 21 days (14 days preliminary and seven days collection). A two-day exercise period was allowed between trials, during which
TABLE 2. Average chemical composition of ration components. Dry matter composition Trials
MDMCS HDMCS Alfalfa Grain mixture
38.7 60.0** 88.1 89.4
7.3 7.6 15.1 13.7
21.9 29.7 8.5
2.1 1.5 1.3 4.5
3.8 3.3 7.6 6.5
64.3 65.7 46.3 66.8
MDMCS HDMCS Grain mixture
36.4 63.5 ~* 88.9
8.4 7.9* 20.3
23.1 22.2* 6.7
2.1 1.8" 3.8
5.8 3.8* 5.5
60.5 64.3* 63.7
* Significantly (P < .05) different from the corresponding MDMCS mean within a trial. ** Significantly (P < .01) different from the corresponding MDMCS mean within a trial. J. DAIRY SCIENCE VOL. 51, NO. 12
OWENS, J O R G E N S E N , AND V O E L K E R
only MDMCS was fed. The silages were fed twice daily and sampled once daily. Feces were measured and sampled once daily. All chemical analyses were conducted on oven-dried samples (48 C for 48 hr), except nitrogen (fresh sample), according to AOAC methods (2). Energy values were determined using a P a r r oxygen adiabatic bomb calorimeter. All data were analyzed on a within-trial basis according to statistical methods outlined by Snedecor and Cochran (14). Results and Discussion
Yield and loss data for silage are given in Table 1. Field losses of dry matter were greater (P < .01) for HDI~ICS than for MDMCS, 17.6% compared to 6.9% in Trial I and 25.4% compared to 5.0% in Trial II. Other studies have shown similar field losses of dry matter for late-harvested corn silage (6,8). Losses were mainly due to leaf and ear droppage; however, some whole plants were lost due to wind damage. F o r the MDMCS in Trial I I , 78% of the corn stalks had ears at harvest, compared to 73% for HDMCS. I n Trial II, 10.1% ears on the ground after harvesting the HDMCS was higher (P < .01) than the 1.1% found before harvesting HDMCS and the 0.9% found after harvesting MDMCS. Average chemical composition of the ration components is presented in Table 2. Significant differences in silage composition for Trial I I are probably due to loss of plant parts (mainly ears and leaves) before and during harvest. The significantly (P < .05) lower ash content of the HDMCS in Trial I I may explain why these cows consumed more mineral than cows fed MDMCS (72.6 g compared to 54.5 g per cow per day). The silages as fed were low in carotene during Trial I. However, in Trial I I the carotene content of MDMCS was higher (P < .01) than that of HDMCS (13.4 vs. 3.1 tLg/gram). The lower p H and higher organic acid concentration of MDMCS in comparison to HDMCS suggests a more active fermentation in the MDMCS (Table 3). The p i t values for the respective silages in Trial I were 3.9 and 4.4, similar to those in Trial II. A decrease in acetic acid content with maturity was also reported by Gordon e t a l . (9). Lactic acid accounted for a slightly higher portion of the total acid in HDMCS. However, the concentration was significantly (P < .05) lower than in MDMCS. Cows fed HDMCS voluntarily consumed more forage dry matter than cows fed MD1V[CS J'. DAIRY SOIENC~ "VOL. 51, No. 12
TABLE 3. Average chemical quality of the silages as fed, Trial II. Measm'ement
pH Organic acids a Acetic Lactic Total Lactic/total b
1.67 7.26 8.93 81.30
0.64* 4.83~ 5.47* 88.30
* Significantly (P < .05) different from the corresponding MDMCS mean. a As per cent of dry matter. b As per cent of total organic acid. (Table 4), but differences were significant (P < .05) only for Trial II. The low intake of silage in Trial I was probably due to consumption of hay and high levels of grain. Other studies (5, 10) have shown that dry matter intake of mature corn silage was superior to earlier harvested silage. Similar to intake, milk yields were greatest for HDMCS. I n Trial I I , 4% FCM level was higher ( P < .01) for HDMCS. I t appears that the higher milk yields on the HDMCS were due to greater voluntary intake of silage dry matter, particularly in Trial II. Per cent SNF and milk fat were not significantly affected by treatment. Huber et al. (11) reported depressed milk fat per cent for cows fed recut corn silage, and Gordon et al. (9) reported slightly lower 4 % FCM for cows fed late-harvested corn silage. However, possible reasons why milk fat synthesis was not reduced by rechopping HDMCS in this compared to the Virginia (11) study were: low grain intakes, a short treatment period, and the higql fiber content of the silage (owing to a low yield of grain). Grinding of TABLE 4. Response of cows fed corn silages cut at different maturities. Response
Trial I I
MDMCS ttDMCS MDMCS HDMCS Dry matter intake (kg/100 kg body wt) Silage .93 .97 1.78 1.92" Hay .56 .55 ............ Concentrate 1.09 1.10 .82 .83 Total 2.58 2.62 2.60 2.75 * Milk production (kg/day) Milk 16.5 17.0 14.4 15.7 ** 4% l~CM 16.0 16.0 15.3 16.6 ** Milk composition (%) Milk fat 3.9 3.8 4.4 4.4 Milk SNF 8.7 8.6 8.9 8.9 Body weight gain (kg/day) 0.33 0.40 0.40 0.74** * Significantly (P < .05) different from corresponding MDMCS mean within a trial. ** SignificarLtly (P < .01) different from corresponding MDMCS mean within a trial.
S I L A G E FOR CATTLE
TABLE 5. Digestibility coefficients and digestible energy of silages fed in Trial II. Digestion coefficients Corn silage
MDMCS HDMCS Difference
66.9 64.7 2.2
54.7 51.1 3.6~
66.0 64.4 1.4
66.7 65.4 1.3
(Keal/g) 2.75 2.72 .03
Significant (P ~ .05). the I-IDMCS before ensiling prevented separation of plant parts in the silo, resulted in better packing, improved fermentation conditions, and prevented selection when fed to cows. Grinding of the HDMCS reduced passage of kernels in the feces, a problem noted by Gordon et al. (9). There appeared to be a considerable loss of whole kernels in the feces of cows fed MDMCS. Efficiency o£ milk production was not affected by stage of maturity. Dry matter required per kilogram of 4% FC]Y[ produced for MDMCS and HDMCS averaged 1.16 and 1.14 kg, respectively. Cows fed HDMCS gained more body weight (Table 4), but differencs were significant (P < .01) only for Trial II. Geasler et al. (7) reported that within harvest dates, gains were greater for steers fed finely chopped silage. Digestibility of the dry matter and energy for MDMCS was slightly higher than that for HDMCS (Table 5), findings similar to that reported by others (5, 9). Apparent digestibility of the crude protein was significantly (P < .05) greater for MDMCS. These data suggest that feeding value of corn silage is not greatly affected by delaying harvest. Due to larg'e field losses, necessity of an extra operation (re-chopping) before ensiling, lower energy yields, and lower carotene contents of HDMCS, general recommendations for delaying harvest of corn for silage are not warranted. A similar conclusion was drawn by Gordon et al. (9). However, this practice resulted in satisfactory preservation of plant nutrients, and animal performance indicates it can be used in emergency situations.
Acknowledgments The assistance rendered by Dr. W. :b. Tucker on experimental design and statistical analysis of the data is greatly appreciated.
References (1) Armsby, H. P. 1890. Losses in the ensilage
(8) (9) (10)
of corn. Pennsylvania Agr. Exp. Sta. Rept. 1890. Part II. Association of Official Agricultural Chemists 1960. Official Methods of Analysis. 9th ed. Washington, D.C. Barker, S. B., and W. H. Sommerson. 1941. The eolorimetric determination of lactic acid in biological determination material. J. Biol. Chem., 138: 535. Baumgardt, B. R. 1964. Practical observations on quantitative analysis of free volatile fatty acids (VFA) in aqueous solutions by gas liquid chromatography. Departmental Bull. 1, Dept. Dairy Sci., University of Wisconsin. Byers, J. H., and E. E. Ormiston. 1964. Feeding value of mature corn silage. J. Dairy Sci., 47: 707. (Abstr.) Geasler, M. R., H. E. Henderson, and D. R. Hawkins. 1967. Relationship of corn silage maturity to yield per hectare. J. Anim. Sci., 26: 1467. (Abstr.) Geasler, iV[. R., H. E. Henderson, and D. R. Hawkins. 1967. Relationship of corn silage maturity to steer performance. J. Anim. Sci., 26: 1467. (Abstr,) Golding, N. S. 1959. A solids-not-fat test for milk using density beads as hydrometers. J. Dairy Sci., 42:899. Gordon, C. H., J. C. Derbyshire, and J. L. Humphrey. 1966. The value of mature corn for silage. USDA, ARS 44-176. Huber, J. T., G. C. Graf, and R. S. Engel. 1965. Effect of maturity on nutritive value of corn silage for lactating cows. J. Dairy Sei., 48: 1121.
(11) Huber, J. T., R. A. Sandy, O. N. Miller, and C. E. Polan. 1966. Recut corn silage for dairy cattle. J. Anim. Sci., 26. : 914. (Abstr.) (12) Lueas, H. L. 1958. Experimental Designs and Analysis for Feeding Efficiency Trials with Dairy Cattle. Feed Utilizatio~ by Dairy Cows. Chap. 15. Iowa Stat~ College Press, Ames. (13) Ragsdale, A. C. and C. W. Turner. 1924. Silage investigations--Loss of nutrients in the silo and during the field curing of corn. Missouri Agr. Exp. Sta., Bull. 65. (14) Snedecor, G. W., aad W. G. Cochran. 1967. Statistical Methods. 6th ed. The Iowa State University Press, Ames.
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