X. Qiu, M. L. Eastridge1, and Z. Wang
The Ohio State University Department of Animal Sciences
Eight intact multiparous cows and four cannulated primiparous cows were fed four diets in a 4 x 4 Latin square design: (1) 17% forage NDF (FNDF) with brown midrib (BMR) corn silage (CS), (2) 21% FNDF with BMRCS, (3) 17% FNDF with conventional CS (CCS), and (4) 21% FNDF with CCS. About 75% of the forage was from CS and 25% from alfalfa hay. The CCS and BMRCS contained 7.8 and 7.7% CP, 41.1 and 41.6% NDF, and 2.3 and 1.1% lignin, respectively. Diets contained 17.4% CP and 38.5% NDF, with soyhulls providing 23.4 and 17.8% of DM for 17 and 21% FNDF diets, respectively. Each period consisted of four weeks for intact cows and two weeks for cannulated cows. For intact cows, DM intake was higher for BMRCS than CCS, and milk urea nitrogen (MUN) was higher for cows fed 21 than 17% FNDF. Milk protein yield tended to be higher and MUN lower for cows fed BMRCS than CCS. Milk yield, milk fat yield, and milk protein percentage were similar among treatments. For the cannulated cows, physical effects of forage were not compromised by feeding BMRCS based on ruminal pH, mat consistency, and volatile fatty acids (VFA). There were no adverse effects of feeding BMRCS in a low FNDF diet with starch concentration of 32.7%.
It is proposed that, if you accept the potential 10 to 15% lower yield, the corn hybrids with the BMR gene can be an excellent forage source, especially when DM intake is a particular concern such as with pre-fresh, fresh, or high-producing cows. This is largely because BMR corn silage usually has higher NDF digestibility than the conventional corn silage. Cows in early lactation experience a negative energy balance, and gut fill is considered to be one of the factors limiting energy intake of dairy cows. An enhanced NDF digestibility is speculated to increase DM intake and thus the energy intake when the maximum intake is limited by gut fill. Previous studies revealed that inclusion of BMR corn silage in the diets could result in higher DM intake, ranging from 0.9 to 7.3 lb/cow/day, but milk yield response has been more variable than DM intake response (Eastridge, 1999).
Because of its higher NDF digestibility, BMR corn silage has not been suggested for use in diets with low FNDF. However, there has been limited justification for this suggestion. The objectives of the current study were to determine the chemical composition of corn silage with and without the BMR gene and to investigate the interaction of corn hybrid and dietary level of FNDF on ruminal fermentation and animal performance.
Eight intact multiparous cows and four ruminally and duodenally cannulated primiparous cows were used in two separate 4 x 4 Latin square designed experiments. The treatments were as follows: (1) 17% FNDF with BMRCS, (2) 21% FNDF with BMRCS, (3) 17% FNDF with CCS, and (4) 21% FNDF with CCS.
The diets contained on average 17.3% CP and 38.5% NDF, with soyhulls providing 23.4 and 17.8% of DM for 17 and 21% FNDF diets, respectively. About 75% of the forage was from CS and 25% from alfalfa hay (Table 1). All cows were fed individually twice a day with unrestricted intake. The amount of feed offered and refused was weighed and sampled for each cow daily during the collection period to determine DM intake.
Table 1. Ingredient and Nutrient Composition of Experimental Diets1.
|Composition||17 - BMR||21 - BMR||17 - CCS||21 - CCS|
|(% of DM)|
|Dry shelled corn||12.95||7.41||12.95||7.41|
|Soybean meal -44% CP||14.8||16.4||14.8||16.4|
|Feed grade urea||0.33||0.15||0.33||0.15|
|Minerals and vitamins||2.47||2.36||2.47||2.36|
|1 17-BMR =
17% forage NDF(FNDF) with brown midrib (BMR) corn silage (CS), 21-BMR=21%
FNDF with BMRCS, 17-CCS=17% FNDF with conventional corn silage (CCS), and
21-CCS=21% FNDF with CCS.
2 Calculated assuming that the two corn silages have the same energy value.
The eight intact cows were fed on each diet for four weeks, with the last two weeks used for sample collection. Data collected included DM intake, milk yield, and milk components. The four cannulated cows were fed for two weeks per period, with the later week devoted to data collection. Ruminal fluid samples were taken on days 11 and 13 of each period at 3, 6, 9, and 12 hours postfeeding to determine pH, NH3-N, and VFA. Rumen mat consistency was determined on day 13 at three hours after the a.m. and p.m. feedings using a weight inserted in the rumen (Welch, 1982). To investigate the rate and extent of NDF disappearance, duplicated in situ bags containing either BMRCS or CCS were incubated in the rumen of cows fed the same CS for 0, 2, 6, 12, 24, 48, and 72 hours.
Chemical composition of the BMR and conventional fresh corn forages and the silages were similar except that the BMR forage was lower in lignin content (Table 2). For intact cows, DM intake was higher for BMRCS than CCS, and MUN was higher for 21 than 17% FNDF (Table 3). An interaction occurred between FNDF and CS for DM intake, indicating that increasing BMRCS in the diet may not have the same depressive affect on DM intake as expected with CCS. Milk protein yield tended to be higher and MUN lower for BMRCS than CCS. Decreasing FNDF from 21 to 17% decreased milk fat percentage with BMRCS but increased it with CCS. Milk yield and milk protein percentage were similar among treatments. While most studies found an increase in milk yield by feeding BMR corn silage (Block et al., 1981; Frenchick et al., 1976; Keith et al., 1979; Oba and Allen, 1999), some were on the contrary (Rook et al., 1977; Sommerfeldt et al., 1979; Stallings et al., 1982). In this particular study, the increase in milk yield with BMRCS approached statistical significance (P = 0.11).
Table 2. Chemical Composition of Brown Midrib (BMR) and Conventional Corn (CC) as Fresh Forage and Corn Silage.
|Fresh Forage||Corn Silage|
|% of DM|
|1 DM=dry matter, CP=crude protein, NDF=neutral detergent fiber, and ADF=acid detergent fber.|
Table 3. Effects of Corn Silage Hybrid and Level of Forage NDF on DM Intake and Performance by Lactating Cows1.
|DM intake, lb/day||57.6||59.0||55.0||51.7||<0.01||0.29||0.03|
|4% FCM, lb/day||75.0||77.0||73.7||72.4||0.14||0.88||0.38|
|Milk fat, %||3.76||3.89||3.93||3.79||0.58||0.95||0.05|
|Milk fat, lb/day||2.92||3.06||2.93||2.83||0.21||0.84||0.17|
|Milk protein, %||3.31||3.29||3.28||3.35||0.62||0.44||0.11|
|Milk protein, lb/day||2.57||2.55||2.44||2.46||0.09||0.96||0.79|
|1 17-BMR=17% forage NDF (FNDF) with brown midrib (BMR) corn silage (CS), 21-BMR=21% FNDF with B<RCS, 17-CCS=17% FNDF with conventional corn silage (CCS), 21-CCS=21% FNDF with CCS, FCM=fat corrected milk, and MUN-milk urea nitrogen.|
Cows fed BMRCS had higher ruminal propionate than cows fed CCS (Table 4). Cows fed 21% FNDF had higher ruminal acetate and lower ruminal propionate than cows fed 17% FNDF. Potentially digestible NDF, calculated by subtracting NDF washout and NDF residuals after 72 hours of incubation, was similar among treatments. The NDF washout was higher for BMRCS than CCS, and this resulted in a higher total digestible NDF for BMRCS than CCS. Ruminal mat consistency, measured by distance traveled by a weight placed in the rumen during the first minute, was similar among treatments. Oba and Allen (1998) found that enhanced NDF digestibility of corn silage did not decrease physical effectiveness of NDF. In this study, unaltered rumen mat consistency and rumen fermentation products also suggested that feeding the BMRCS might not compromise the physical effects of the forage. Because cows fed 17% FNDF with BMRCS resulted in a relatively high level of DM intake and milk yield, and the ruminal fermentation was not adversely affected, there were no adverse effects of feeding BMRCS in a relatively low FNDF diet with starch concentration of 32.8% (FNDF/starch = 0.52). Optimizing animal performance and health necessitates providing a proper balance between dietary levels of effective fiber and starch.
Table 4. Effects of Corn Silage Hybrid and Level of Forage NDF on Ruminal Fermentation, In Situ Disappearance of NDF in Silage, and Rumen Mat Consistency1.
|Ammonia Nitrogen, mg/dl||16.0||14.8||17.1||17.9||0.41||0.92||0.69|
|Total VFA, mg/dl||121||120||112||118||0.30||0.57||0.51|
|In situ NDF disappearance:|
|Potentially Degestible NDF, %||51.1||57.8||54.0||51.8||0.63||0.49||0.20|
|Total digestible NDF, %||66.7||68.3||61.5||57.4||0.02||0.65||0.29|
|Distance traveled in min 1, cm||14.0||11.3||15.3||13.4||0.40||0.25||0.83|
|Total ascension time, min||6.4||7.6||7.3||6.9||0.72||0.43||0.06|
|1 17-BMR=17% forage NDF (FNDF) with brown midrib (BMR) corn silage (CS), 21-BMR=21% FNDF with BMRCS, 17-CCS=17% FNDF with conventional corn silage (CCS), 21-CCS=21% FNDF with CCS, and VFA=volatile fatty acids.|
Appreciation is extended to Cargill Hybrid Seeds (Minneapolis, Minn.) for partial support of this research.
Block, E., L. D. Muller, L. C. Griel Jr., and D. L. Garwood. 1981. Brown midrib-3 corn silage and heat extruded soybeans for early lactating dairy cows. J Diary Sci. 64:1813-1825.
Eastridge, M. L. 1999. Brown midrib corn silage. Proceedings of the Tri-State Dairy Nutrition Conference. The Ohio State University, Columbus. pp.179-190.
Frenchick, G. E., D. G. Johnson, J. M. Murphy, and D. E. Otterby. 1976. Brown midrib corn silage in dairy cattle rations. J. Dairy Sci. 59:2126-2129.
Keith, E. A., V. F. Colenbrander, V. L. Lechtenberg, and L. F. Bauman. 1979. Nutrition value of brown midrib corn silage for lactating dairy cows. J. Dairy Sci. 62:788-792.
Oba, M. and M. S. Allen. 1999. Effects of brown midrib 3 mutation in corn silage on dry matter intake and productivity of high yielding dairy cows. J. Dairy Sci. 82:135-142.
Oba, M. and M. S. Allen. 1998. Enhanced NDF digestibility of corn silage did not decrease physical effectiveness of NDF. J. Dairy Sci. 81 (Suppl. 1):365.(Abstr.)
Rook, J. A., L. D. Muller, and D. B. Shank. 1977. Intake and digestibility of brown midrib corn silage by lactating dairy cows. J Dairy Sci. 60:1894-1904.
Sommerfeldt, J. L., D. J. Schingoethe, and L. D. Muller. 1979. Brown midrib corn silage for lactating dairy cows. J. Dairy Sci. 62:1611-1618.
Stallings, C. C., B. M. Donaldson, J. W. Thomas, and E. C. Rossman. 1982. In vivo evaluation of brown midrib corn silage by sheep and lactating dairy cows. J. Dairy Sci. 65:1945-1949.
Welch, J. G. 1982. Rumination, particle size, and passage from the rumen. J. Anim. Sci. 54:885.
1 For more information, contact at: The Ohio State University, 221B Animal Science Building, 2029 Fyffe Road, Columbus, OH 43210; (614) 688-3059, Fax (614) 292-1515; email:firstname.lastname@example.org