Effect of Diet Containing Different Amount of Wheat Dried Distillers’ Grain as a Substitute for Alfalfa Hay on Holstein Lactating Cow Responses

Wheat dried distillers' grain (WDDG) as a co-product has a high content of neutral detergent fiber (NDF) and crude protein (CP), due to the selective removal of starch during the production process. Therefore, it has been proposed to use this by product as a good source of non-forage fiber in ruminant rations. The objective of this study was to evaluate the effect of diets containing different amount of Wheat dried distillers' grain as a partial substitute for alfalfa hay on lactation performance, blood metabolites and chewing activity of lactating Holstein dairy cows. Nine primiparous Holstein lactating dairy cows (76±18 days in milk) were assigned randomly to a replicated 3×3 Latin square design with 21 d periods. Basal diet (BD) was provided using 31.2% alfalfa Milk samples were collected weekly at each milking, then, analyzed for protein, lactose and fat. Blood samples were drawn from the jugular vein into heparinized evacuated tubes on the last day of each experimental period at 4 h post-feeding, then, plasma was provided. Plasma samples were analyzed to determine glucose and urea-N concentrations. Chewing activity (i.e. eating, ruminating, idle)for cows were monitored over a 24 h by manually observing individual cows every 5 min. Inclusion of WDDG in the experimental diets did not affect DMI, milk yield, milk composition, blood glucose. Except for total chewing activity (min/kg NDF) that was decreased significantly with inclusion of WDDG, all other evaluating indices were not affected by treatments. However, diet containing WDDG at 5% caused a significant decrease (P<0.05) in blood plasma urea-N compared with that of the cows fed basal diet (BD= 21.6 and BD+WDDG5= 19.9 mg/dl). Therefore, it was concluded that WDDG might include in the lactating cow diets, up to 8.7%, without any negatively impacting on milk yield, milk composition and blood metabolites evaluated.


INTRODUCTION
Distiller's dried grains as non-forage sources of fiber are a co-product of bio-ethanol production from cereal grains. Due to the selective removal of starch during the production process, it has a high content of NDF and crude protein (CP), allowed to use this by product as a good source of protein and energy in the diet of ruminants. This is mainly due to their high digestible fiber content and ruminal escape protein levels (Mustafa et al., 2000).
Forages usually are the major source of fiber in dairy rations. Non-forage sources of fiber have a low lignin content and large proportion of potentially digestible fiber (Mojtahedi and DaneshMesgaran, 2011) that supply energy needed for lactation without the ruminal acid load caused by rapidly fermented starchy concentrates (Rezaii et al., 2009(Rezaii et al., , 2010(Rezaii et al., , 2011. Non-forage sources of fiber also may serve as partial replacements for forage fiber in those situations where forage availability is limited. Compared with most forage, non-forage sources of fiber typically have a smaller particle size and relatively high specific gravity which promote particle passage from the rumen (Creswell, 1958;Kaske and Engelhardt, 1990). Various experiments were conducted to evaluate animal health and performance responses of lactating Holsteindairy cows fed diets formulated by partial replacement of forage effective neutral detergent fiber (eNDF) with an equal estimated amount of eNDF from a mixture of non-forage sources of fiber (Pereira et al., 1999). In addition, the ability to prevent depression of milk fat concentration, relative to alfalfa haylage, was evaluated (Swain and Armentano, 1994). It has been reported that ruminal NDF digestibility was equal for diets of similar total NDF content formulated by partial replacement of forage with non-forage sources of fiber (Cunningham et al., 1993). However, the (NDF) from most Non-forage sources of fiber does not stimulate chewing activity as effectively as forage NDF (Pereira and Armentano, 2000). Decreased chewing activity when non-forage sources of fiber replace forage can decrease the flow of salivary buffer to the rumen, decreasing rumen pH and NDF degradation (Grant and Mertens, 1992). Chewing activity and rumen pH of lactating cows decreased when soy-hulls replaced 42% of dietary forage in a 59% forage diet and total NDF was increased from 28 to34% of diet DM (Weidner and Grant, 1994).
There are varying approaches for the inclusion of distillers' grains into the diets of lactating dairy cattle. Most often, distillers' grains have been included in the diets as an energy and protein supplement by replacing a portion of the dietary concentrate especially with soybean meal (Anderson et al., 2006, Batajoo andShaver, 1998). They contain a valuable source of supplemental protein with high rumen undegradability, that 60% of crude protein as compared to 37% in soybean meal (Batajoo and Shaver, 1998;NRC, 2001). They also contain other nutrients recovered from fermented grains. These include low soluble carbohydrates, relatively high fiber, high fat and factors that stimulate cellulose digestion in the rumen (Hatch, 1993). Because of the high fiber content in distillers' grains, it may be possible to use them as a partial forage replacement (Clark and Armentano, 1993;Penner et al., 2009).
The objective of this study was to evaluate the effect of Wheat dried distillers' grain substitution for alfalfa hay on the lactation performance, blood metabolites and chewing activity of lactating Holstein dairy cows.

Animals, Diets and Experimental Design
Nine primiparous lactating Holstein dairy cows with average live weight of 559 kg and 76 ± 18 days in milk were assigned randomly to a replicated 3×3 Latin square design with 21 d periods. Each 21 d period consisted of 14 d adaptation period and 7 d sampling period. Throughout the experiment, cows were housed in a tie-stalls barn and were individually fed a total mixed ration (TMR) at 0800 and 1700 h and milked in a herringbone parlour thrice daily at 0500, 1300 and 2130 h. theWDDG used in this study was without soluble and Chemical composition of WDDG is in Table 1.

Sample Analysis
Samples of individual feedstuffs and TMR were dried at 60°C in an oven for 48 h, ground through a 1mm screen in a Wiley Mill (Arthur Hill Thomas Co., Philadelphia, PA). Samples of individual feedstuffs and TMR were analyzed for DM, ASH (determined after 5h of oxidation  , 1991). Sodium sulfate was used in the NDF analysis. NDF assayed without a heat stable amylase and expressed including residual ash. Non-protein N was estimated by incubating 2 g DM equivalent of DWDGsamples in 3 M sodium tungstate solution and determining N in residual sediments (NPN was thencalculated as the total N minus residual sediments N).
Dry matter intake (DMI) and milk yield was recorded daily throughout the 7 d collection period. Milk samples were collected from 3 consecutive milkings during 3 and 5 d of each sampling period and then predicted for protein, lactose and fat (Foss System 4000, Foss Electric, Hillerod, Denmark). Blood samples were drawn from the jugular vein into heparinized evacuated tubes on the last day of each experimental period at 4 h post-feeding. Samples were centrifuged at 1500 x gfor 10min and the plasma was frozen at −20°C prior to determine the urea-N and glucose concentration. The concentration of urea-N and glucose determined with an automatic blood chemical analyzer (SELECTRA trade mark) with the use of a commercially available kit (man kit).

Chewing Activity
Chewing activity (i.e. eating, ruminating, idle) were monitored over 24 h duration on d 4 of each sampling period by manually observing individual cows every 5 min. the recorded activity was assumed to extend for the entire 5 min interval. Chewing activity was also monitored during milking and during the transition to and from the milking parlor.

Statistical Analysis
Data were analyzed using the MIXED procedure of SAS 9.1 (2004). The model included the fixed effects of square, period and treatment, and the random effect of cow nested within square. The model of experiment was: Where µ is the overall mean, C i is the random effect of cow (i = 1 to 9), P j is the fixed effect of period (j = 1 to3), T k is the fixed effect of treatment (k = 1 to 3), and e ijk is the residual, assumed to be normally distributed. Differences between least squares means were considered significant at p<0.05, using PDIFF in the LSMEANS statement.

Feed Intake, Lactation Performance and Blood Metabolites
Data of dry matter intake, lactation performance and blood metabolites of the animals used in the present experiment are shown in Table 3. Dry matter intake was not affected (P>0.05) by decreasing forage NDF and with increasing WDDG in the diet (Table 2). Allen (2000), showed that DMI by lactating cows was maintained in most studies when non-forage fiber sources replaced forage. It was also reported that DMI did not decrease when dried brewers grains was included in cow diets (Younker et al., 1998). The potential filling effects of WDDG and lack of DMI depression in the present study may be explained by ruminal digestion process. It has been proposed that wheat dried distillers grains appeared to have a faster outflow rate than forage (corn silage plus alfalfa silage) but a slower NDF digestion rate than that of alfalfa silage (Younker et al., 1998). The replacement of forage NDF with NDF from WDDG might have decreased the digestion rate but increased the passage rate of NDF, apparently counteracting effects on rumen fill and, therefore, DMI in this study. Replacement of forage with wet corn gluten feed (Allen and Grant, 2000) or a new wet milling corn product (Broddugari et al., 2001) had no consistent effect on overall ruminal NDF digestion rate, whereas passage rate increased in both studies. Therefore, all WDDG diets in the current study supporting the potential for WDDG to serve as a partial forage replacement in diets meeting NRC (2001) guidelines for DMI.
Milk yield and milk composition including fat and protein were not affected by WDDG diets. In addition, the lack of response in milk fat and protein yields would support the hypothesis that WDDG have a similar effectiveness compared with the control diet. Apparently, the decrease in ADF concentration (Table 2) and providing similar amount of NDF with increasing WDDG was not large enough to affect lactation performance, while energy intake was almost constant among the animals used (Firkins et al., 2002). Because milk fat is dependent on fiber digestion and production of fermentation acids in the rumen, it is thought to be the most complete measure of effective NDF, often used as an indicator of rumen health and may indicate inadequate peNDF for the WDDG diet (Zebeli et al., 2006;Armentano and Pereira, 1997), therefore similarity of milk fat between present treatments imply that NDF of WDDG can effectively prevent milk fat depression. Kalscheur (2003), showed similar milk fat with inclusion of distillers' dried grains like this study too.
At level of 5% WDDG, there was a decrease in blood urea-N concentration (Table 3). There is a positive relationship between blood urea-N concentration and ruminal NH3-N concentration (Dann and Varga, 1999). Therefore, feeding diets with higher ruminally available NDF as WDDG to lactating cows may be more desirable. Thus, feeding diets with 5% WDDG might have benefits on animal health as observed in reduced blood Urea-N concentration (Dann and Varga, 1999).  Table 4 summarizes chewing activity as influenced by dietary treatment.Except for total chewing activity (min/kg NDF) that was decreased significantly with inclusion of WDDG, all other evaluating indices were not affected by treatments (Table 4). Non-forage sources of fiber do not stimulate rumination activity as effectively as dietary forage because of their small particle size (Mertens, 1997). Therefore, it is important to consider the effective NDF content of these fiber sources. Effective NDF has been estimated with three approaches including:
Rumination activity has been used as an estimate of the physical effectiveness of fiber sources at stimulating salivary secretion and ruminal buffering (Allen, 1997). In the present study, we did not measure the peNDF content, but similar chewing activity and milk fat content between treatments indicate that peNDF value is same among treatments. This speculation is supported by Zebeli et al. (2006), which conducted a meta-analysis using 33 experiments with 131 treatments and determined that chewing time was positively correlated with dietary physically effective NDF (peNDF) content.

CONCLUSION
Results from this study indicate that WDDG may be incorporated into dairy cattle diets up to 8.7% without adversely affecting feed intake and milk production. In addition, yields and composition of all major milk components were similar for all the experimental diets. Similarity of milk fat percentage between present treatments implies that NDF of WDDG can effectively prevent milk fat depression. Therefore, it can be concluded, based on the results of this study, that inclusion of WDDG at up to 8.7%, as a partial replacement of alfalfa hay, in lactating Holsteindairy cow diets does not appear to alter eating and ruminating (min/kg DM) when the rations are formulated to meet the NDF requirements of the cows. Besides, replacing alfalfa hay with WDDG at up to 8.7% of dietary DM is a viable alternative for producers when forage is limiting. Wheat distillers' dried grains contain high level of undegradable protein and this may lead to a lower ruminal ammonia concentration, hence the low blood urea-N level in the animals fed BD+WDDG5 was expected.