A. L. Slater
M. L. Eastridge 1
J. L. Firkins
The Ohio State University
Department of Animal Sciences
1 For more information, contact at: The Ohio State University, 221B Animal Science Building, 2029 Fyffe Road, Columbus, OH 43210-1095; 614-688-3059; fax: 614-292-1515; e-mail: firstname.lastname@example.org
Neutral detergent fiber (NDF) from soyhulls and whole linted cottonseed were used to replace a portion of NDF from forage (40:60 alfalfa silage:corn silage) and a portion of concentrate. Two different sources of starch, differing in rumen degradability, were evaluated when forage NDF (FNDF) was reduced to 16%. Forty-eight cows were fed one of four diets: (1) 21% FNDF with corn, (2) 16% FNDF with corn, (3) 16% FNDF with corn and wheat (1:1), and (4) 11% FNDF with whole linted cottonseed (WCS) and corn. Experimental diets were fed during weeks 10 to 25 of lactation as a TMR.
Actual FNDF concentrations were two to three units lower than formulated. Dry matter intake and milk yield were highest for cows fed 11% FNDF with WCS. Milk fat percentage and yield were highest for cows consuming 16% FNDF with corn and lowest for cows consuming 16% FNDF with corn and wheat. Cows fed 11% FNDF with WCS and 16% FNDF with corn and wheat had the highest milk protein yield but lowest protein percentage. Cows fed 16% FNDF with corn and wheat showed fat-protein inversion.
For cows in midlactation, FNDF may be reduced to 9 to 11% when WCS is at 11% of the DM and dietary starch is reduced to 30% of the DM. Forage NDF may be reduced to 14 to 16% without WCS when concentration of rumen degradable starch is monitored and starch is at 30% of the DM. It is still uncertain whether FNDF concentrations at these levels are appropriate for early lactation cows.
Carbohydrates make up 60 to 70% of the dry matter (DM) in a dairy cow's diet and are a major source of energy for the synthesis of milk fat, protein, and lactose. Carbohydrates can be split into two fractions, fibrous carbohydrates and nonfiber carbohydrates (NFC). Fibrous carbohydrates are composed of the cell walls of plants that provide rigidity and support to the cell and can be analyzed for nutritional purposes by the detergent system (Van Soest et al., 1991). The NDF fraction consists of hemicellulose, cellulose, and lignin and is fermented slowly in the rumen. Nonfiber carbohydrates consist of starch and sugars, which are rapidly degraded in the rumen.
Research has shown that rumen degradable starch at high levels in the diet affects dry matter intake (DMI), milk production and composition, and decreases pH in the rumen, which can lead to health problems, such as acidosis, laminitis, and displaced abomasum. Therefore, ruminants have a dietary requirement for fiber necessary to maintain an optimal rumen environment for maximum milk production and cow health. When formulating rations, a balance needs to be made between the NFC fraction and the neutral detergent fiber (NDF) fraction to provide enough energy to the cow to maximize milk production and to maintain an optimal ruminal environment (Firkins, 1997; Harmison et al., 1997).
More and more producers are interested in using byproducts such as soyhulls, distillers grains, brewers grains, and cottonseed in dairy cattle diets for the replacement of forage and concentrate. Byproducts are high in energy, fiber, and crude protein, are readily degraded in the rumen, and often are less expensive than traditional feed sources. Use of these products may be an alternative to the addition of more cereal grains to the diet, especially when forages are of extremely poor quality or in short supply. The objective of this research was to determine the effects of NDF from soyhulls and cottonseed for replacing forage NDF (FNDF) and the effects of starch from two different cereal grains on the performance of lactating dairy cows.
Forty-eight lactating Holstein cows (20 primiparous and 28 multiparous) averaging 60 days in milk (DIM) were used. Cows were fed a similar diet during weeks eight to nine of lactation, and then animals were switched to one of four experimental diets (Table 1). Experimental diets were fed during weeks 10 to 25 of lactation. The control diet was balanced to contain 21% FNDF and 42% NFC. Two diets consisted of 16% FNDF with either corn or corn and wheat as the starch sources, and one diet consisted of 11% FNDF with WCS. The 21% FNDF diet with corn was balanced to contain a dietary NDF of 28%. Dietary NDF was increased to 35% for the 16 and 11% FNDF diets during formulation by the addition of soyhulls and whole linted cottonseed (WCS) to the diet. The NFC was reduced to 35% for the 16 and 11% FNDF diets during formulation by the substitution of soyhulls and WCS for concentrate. All diets were balanced to contain 18% crude protein (CP) and 4% fatty acids.
Table 1. Ingredient Composition of Diets Fed to Cows During the Experimental|
Period That Were Differing in FNDF Percentage and Source of Starch.1
|% of DM|
|Dry shelled corn||30.6||22.9||13.8||27.2|
|Soybean meal, 44% CP||15.9||12.5||8.8||10.0|
|Corn gluten meal||0.28||1.80||0.50||0.90|
|Mineral & vitamin suppl.||2.04||1.98||2.06||2.18|
|1 FNDF = forage NDF and WCS = whole linted cottonseed.|
Cows were housed in a tie-stall barn and milked twice daily. Milk samples were taken weekly from four consecutive milkings and analyzed for milk fat and protein by infrared spectroscopy (DHI Cooperative, Inc., Powell, Ohio). Body weights were recorded weekly after the a.m. milking. Body condition score was recorded at the beginning of the covariate period and then at weeks 1, 4, 8, 12, and 16 of the experiment.
Neutral detergent fiber, acid detergent fiber (ADF), and lignin were determined sequentially according to the procedure of Van Soest et al. (1991). Starch was determined using the procedure described by Sarwar et al. (1992). Ruminal fluid samples were taken by stomach tube at week 10 of the experimental period, at approximately six hours after feeding. Feed samples were separated using an oscillating shaker with six screens (USA Standard Testing Sieve, CE Tyler, Inc., Combustion Engineering) and mean particle size (MPS) was determined as described by Waldo et al. (1971). Cows were observed once every five minutes, over an 18-hour period, to determine the amount of time spent chewing while eating and ruminating. Data were analyzed using the GLM procedure of SAS (1988).
The chemical composition of the diets is shown in Table 2. Total NDF was higher for the 16 and 11% FNDF diets than for the 21% FNDF diet due to the addition of soyhulls and WCS. The actual FNDF concentrations were 17.8, 14.0, 13.9, and 9.4% for the 21% FNDF with corn, 16% FNDF with corn, 16% FNDF with corn and wheat, and 11% FNDF with WCS, respectively. These values were lower than expected because the quality of alfalfa silage increased during the trial. Calculated NFC values were higher than the expected calculated values of 42% for the 21% FNDF with corn and 35% for the 16% FNDF and 11% FNDF diets. The starch concentrations in the diets were eight to 12 units lower than NFC. This is to be expected because the enzymatic determination only determines starch content, while calculation takes into account all NFC in addition to starch.
Table 2. Chemical Composition of Diets Fed to Cows During the Experimental|
Period That Were Differing in FNDF Percentage and Source of Starch.1
|NEL, Mcal/kg of DM3||1.88||1.82||1.85||1.78|
|1 NDFCP = NDF corrected for protein contamination, FNDF = |
forage NDF, ADL = acid detergent lignin, and
WCS = whole linted cottonseed.
2 NFC = nonfiber carbohydrates calculated by difference 100 - [ NDFCP +
CP + ash + (FA/0.90)].
3 Calculated using Weiss et al. (1992, 1998).
Dry matter intake (pounds per day and as percentage of body weight [BW]) was highest for cows consuming 11% FNDF with WCS (Table 3). The reduction of dietary forage and MPS plus the addition of WCS may have been responsible for the increase in intake. Cows fed 16% FNDF with corn and wheat had the lowest DMI, possibly because of the increase in ruminal degradable starch resulting in a lower ruminal pH compared to the remaining treatments. Cows fed 21% FNDF with corn had lower NDF intake but higher FNDF intake (Table 3). This was expected due to the lower percentage of NDF in the diet but the higher percentage of forage. Cows fed 11% FNDF with WCS had the highest NDF intake because of increased DMI.
|Table 3. Effects of Dietary FNDF Percentage and Source of Starch on Performance of Cows.|
|DMI % of BW||3.76b||3.87b||3.63c||4.14a||0.47|
|NDF intake, kg/d||6.28c||7.63b||7.43b||8.60a||0.10|
|FNDF1 intake, kg/d||4.02a||3.22b||3.01c||2.38d||0.04|
|3.5 % FCM, kg/d||33.1b||33.5ab||33.0b||34.3a||0.3|
|Milk fat , %||3.52a||3.61a||3.25b||3.35b||0.37|
|Milk fat, g/d||1,157b||1,178a||1,110c||1,168ab||13|
|Milk protein, %||3.30ab||3.27b||3.31a||3.28b||0.01|
|Milk protein, g/d||1,088b||1,082b||1,136a||1,154a||11|
|BW change, kg/d||0.40||0.29||0.40||0.28||0.18|
abcd Means in a row with different superscripts differ (P < 0.05).|
1 DMI = dry matter intake; BW = body weight; FNDF = forage NDF; BCS =
Body condition score (five point scale where 1 = thin to 5 = fat); A:P =
Acetate:propionate; and MPS = mean particle size.
Cows fed 11% FNDF with WCS had higher milk yield (Table 3), probably because of higher DMI. Cows fed 16% FNDF with corn and wheat had higher milk yield than cows fed 21 and 16% FNDF with corn, even though intake was less for those cows. Wheat degrades faster than corn in the rumen (Michalet-Doreau et al., 1997). This may increase microbial protein flow to the small intestine and subsequently increase milk yield and milk protein.
Cows fed 21 and 16% FNDF with corn had higher milk fat percentage than cows fed 16% FNDF with corn and wheat and 11% FNDF with WCS. It is difficult to determine if the increase observed in milk fat percentage in these studies was from the increase in WCS, dietary forage concentration, or dietary NDF concentration. A response of WCS for milk fat percentage may not have been observed in this study because of an increase in milk yield by cows fed WCS and the low concentration of FNDF in the diet. Milk yield was not affected in the studies where milk fat percentage increased by the addition of WCS. Milk fat percentage was lowest for cows fed 16% FNDF with corn and wheat. Cows fed 16% FNDF with corn had the highest milk fat yield (Table 3).
Cows fed 16% FNDF with corn and wheat had the highest milk protein percentage, which was higher than the milk fat percentage. This occurrence is known as fat-protein inversion and is usually indicative of an imbalance between effective fiber and starch source. Protein yield was higher for cows fed 16% FNDF with corn and wheat and 11% FNDF with WCS than for cows fed 21 and 16% FNDF with corn. The increase in milk protein yield may be in response to increased milk yield.
Body weight and BW change were not different among treatments (Table 3). Cows fed 11% FNDF with WCS had the lowest body condition score (BCS), although not significantly different from that of cows fed 21% FNDF with corn or 16% FNDF with corn and wheat. With no difference in BW change but higher NEL intake (data not shown), cows fed 11% FNDF with WCS partitioned the additional energy into milk production. Cows fed 16% FNDF with corn and wheat were the most efficient at producing fat corrected milk (FCM) (FCM/DMI; Table 3). The ruminal availability of carbohydrates from the addition of wheat may have increased the microbial efficiency and thereby increased efficiency of milk production. Ruminal acetate:propionate ratios were not indicative of milk fat percentage in this study.
The MPS was 2.99, 2.02, 2.01, and 2.21 mm for 21% FNDF with corn, 16% FNDF with corn, 16% FNDF with corn and wheat, and 11% FNDF with WCS, respectively (Table 3). The replacement of forage with soyhulls and WCS decreased the MPS of the diets. The addition of WCS in the 11% FNDF diet increased MPS over the 16% FNDF diets containing just soyhulls replacing forage NDF.
There were no differences among treatments for time spent chewing (minutes/day; Table 3), even though MPS of the diets decreased by the substitution of forage with soyhulls and WCS. Cows fed 21% FNDF with corn chewed approximately 7% more than cows fed the remaining diets. The increase in dietary NDF concentration from the soyhulls and WCS may be responsible for maintaining chewing, compared to the diet containing 27.5% dietary NDF. Cows fed 21% FNDF with corn spent more time chewing per kilogram of NDF than cows fed the other diets. As percentage of forage decreased in the diet, the amount of time spent chewing per kilogram of NDF decreased. The NDF from forage is more effective at stimulating chewing than NDF from soyhulls and WCS. The amount of chewing per kilogram of FNDF was lower for the 21 and 15% FNDF diets than the 11% FNDF diet. The WCS may have stimulated some chewing which would cause an increase in chewing per unit of FNDF. Grant (1997) concluded that cows might have an adaptive mechanism that enables them to chew more effectively when there are limited amounts of low effective fiber. This may explain why cows in this study maintained ruminal conditions and milk yield when NDF from forage was replaced with NDF from soyhulls and WCS.
The experiment took place from October 1996 through May 1997. One cow fed 21% FNDF with corn had a right displaced abomasum (RDA) near the end of the experimental period. Two cows fed 16% FNDF with corn had left displaced abomasum (LDA), one cow had an RDA, and one cow had a right torsion of the abomasum. One cow fed 16% FNDF with corn and wheat had an RDA. One cow fed 11% FNDF with WCS had an LDA, and one cow had an RDA. Winter dysentery affected nearly all the cows in the barn during mid-February.
More problems were expected with 16% FNDF with corn and wheat due to the increased rumen degradability of the starch and with 11% FNDF with WCS due to the low concentration of FNDF; however, cows fed 16% FNDF with corn appeared to develop more health problems than cows on other treatments. Many of the problems observed may have occurred because FNDF concentrations were actually two to three units lower than formulated. Cows fed 16% FNDF with corn chewed 10% more than cows fed 16% FNDF with corn and wheat and 6% more than cows fed 11% FNDF with WCS. This may have been an attempt by the cow to produce more saliva to buffer the rumen and counteract a ruminal imbalance.
Increasing ruminal degradable starch when FNDF was actually 14% of the DM decreased DMI and milk fat percentage but increased milk production and milk protein percentage. Dry matter intake and milk production were increased when FNDF was decreased to 9% and WCS was 11% of the DM. Reducing FNDF to 14 and 9% of the DM with soyhulls and WCS as fiber sources stimulated as much chewing and maintained ruminal function similar to a diet containing 18% FNDF with alfalfa silage:corn silage (40:60) as the forage sources. Based on these data for cows past the first third of lactation, FNDF may be reduced to 9 to 11% FNDF when WCS is fed at 11% of the DM and dietary starch is at 30% of the DM. Forage NDF may also be reduced to 14 to 16% when decreasing dietary starch to 30% of the DM with soyhulls. Because of the high incidence of health problems with cows fed 14 to 16% FNDF with corn, caution should be taken when feeding these or similar diets for long periods of time, and it may not be appropriate to feed such diets to cows in the first one third of lactation.
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