Digestibility of NDF and its effect on the level of rumen fermentation of carbohydrates

DOI: 10.15414/afz.2015.18.04.110–113 Received 14. July 2015 ǀ Accepted 12. October 2015 ǀ Available online 7. December 2015 The objective of this study, was to determinate the effects of digestibility of NDF of TMR on rumen fermentation characteristics and nutrient digestion, dairy cows were fed total mixed ration (TMR). We are measured NDF digestibility of TMR using in situ methods.Digestibility of NDF of TMR in our experiment range 26.8 to 48.2%.  Digestibility of NDF of TMR did not alter VFA production but had effects on A/P ratio and production of acetate and propionate. Our results indicate that TMR with more dNDF may provide more favourable condition for nutrient digestion both in the rumen and in the total tract of dairy cows. Keywords : rumen, fermentation, NDF, volatile fatty acids, digestibility of NDF References ALLEN, M. S., BRADFORD, B. J. and OBA, M. (2009) BOARD-INVITED REVIEW: The hepatic oxidation theory of the control of feed intake and its application to ruminants. In J. Anim. Sci., vol. 87, no. 10, pp. 3317–3334. doi:http://dx.doi.org/10.2527/jas.2009-1779 BEEVER, D. E. and MOULD, F. L. (2000) Forage evaluation for efficient ruminant livestock production. In: D. I. Givens et al. (eds.) Forage Evaluation in Ruminant Nutrition. Wallington: CAB International. HOFFMAN, P.C. and SHAVER, R.D. (2009) UW-Feed Grain Evaluation System Marshfield Soil and Forage Analysis Laboratory. [Online] Available at: http://www.uwex.edu/ces/dairynutrition/documents/ WisconsinFGES.pdf. [Accessed? 2015-06-04]. HUTJENS, M. F. (2002) Is your TMR as good as it can be? In Hoard´s Dairyman, vol. 147, no. 18, pp. 698. CHUMPAWADEE, S. and PIMPA, O. (2009) Effect of fodder tree as fiber sources in total mixed ration on feed intake, nutrient digestibility, chewing behaviour and ruminal fermentation in beef cattle. In J. Anim. And Vet. Adv, vol. 8, no. 7, pp. 1279:1284. doi: http://dx.doi.org/2009.1279.1284 KOLVER, E. S. and DE VETH, M. J. (2002) Prediction of ruminal pH from pasture based diets. In J. Dairy Sci., vol. 85, no. 5, pp. 1255–1266. doi:http://dx.doi.org/10.3168/jds.S0022-0302 (02)74190-8 LINN, J.G. et al. (1989) Feeding the dairy herd. Madison: North Central Regional Extension. LOPEZ, S., J. DIJKSTRA, and FRANCE, J. (2000) Prediction of energy supply in ruminants, with emphasis on forages. In: D. I. Givens, E. Owens, R. F. E., Axford, and H. M. Omed, (eds.) Forage Evaluation in Ruminant Nutrition. Wallingford: CAB International, pp. 63-94. NRC (2001) Nutrient requirements of dairy cattle: Nutrient requirements of domestic animals. 7th revised edition. Washington: National Reserach Council. OBA, M. and ALLEN, M. S. (1999) Evaluation of the importance of the digestibility of neutral detergent fiber from forage: effects on dry matter intake and milk yield of dairy cows. In J. Dairy Sci., vol. 82, no. 3, pp. 589-596. doi:http://dx.doi.org/10.3168/jds.S0022-0302(99)75271-9 OBA, M. and ALLEN, M. S. (2000) Effects of brown midrib 3 mutation in corn silage on productivity of dairy cows fed two concentrations of dietary neutral detergent fiber: 3. Digestibility and microbial efficiency. In J. Dairy Sci., vol. 83, no. 6, pp. 1342–1349. doi: http://dx.doi.org/10.3168/jds.S0022-0302(00)75001-6 ORSKOV, E.R. and MCDONALD, I. (1979) The estimation of protein degradability in the rumen from incubation measurements weighed according to rate of passage. In J. Agric. Sci., vol. 92, no. 3, pp. 499-503. doi:http://dx.doi.org/10.1017/S0021859600063048 VARGA G.A. (2006) In vivo digestibility of forage. In: Proc. Tri-State dairy nutrition conference, Fort Wayne. Columbus: The Ohio State University, pp 95-106. VOELKER LINTON., J. A. and ALLEN, M. S. (2009) Nutrient demand interacts with forage family to affect N digestion and utilization responses in dairy cows. In J. Dairy Sci., vol. 92, no. 4, pp.1594-1602. doi:http://dx.doi.org/10.3168/jds.2008-1327


Introduction
Feeding of total mixed rations (TMR) in dairy cows resulted in increased milk production, through the optimization more balanced ration with a uniform rate of roughage and concentrate and increased DM intake.Increasing production efficiency with feeding TMR is associated with a constant intake of nutrients which is stabilized fermentation and rumen environment for growth of microflora, nitrogen utilization and production of microbial protein.Effects of TMR in comparison with conventional feeding system for the same intake of nutrients increased their utilization by 4% and milk production by 5% (Hutjens, 2002).The quantity and quality neutral detergent fibre (NDF) in TMR acts as a major factor affecting feed intake, rumination, passage and digestibility of nutrients to support production through stabilization of rumen function and healthy rumen environment (Chumpawadee and Pimp, 2009).
Digestibility of NDF is a good indicator for evaluation of the nutritional value of TMR for lactating dairy cows.Higher digestibility of NDF increases the rates and efficiency of rumen fermentation, which is stimulated by appetite of cows with higher intake of dry matter (Voelker et al., 2009).To maintain a healthy rumen environment of high producing dairy cows during early lactation is necessary to maintain the recommended amount of NDF in the range of 280 to 330 g kg-1 of dry matter (Varga, 2006).Digestibility of NDF is crucially influenced by the phase of vegetation and proportional representation of roughage.Digestibility of NDF in relation to the plants mature and chemical composition of the feed, structure and harvest, disruption of stalk and grinding of grains, according to the used hybrid maize (Hoffman and Shawer, 2009).Grasses are characterized by greater digestibility NDF compared to legumes.At high digestibility NDF of roughage increases dry matter intake and utilization of energy from ration, which promotes the synthesis of milk and reduces supply of grain.At low digestibility and lack of compensation of nutrients of TMR required amount of energy and nutrients for the synthesis of milk, which animals meet increasingly from body reserves with excessive weight loss and health disorders (Oba and Allen, 1999).The improved digestibility NDF of TMR helps to maintain rumen pH and to the proportion of acetic and propionic acid (A/P ratio) also contributes to stabilization of the conditions in the rumen of rumen function and improving e.g. higher fibrolytic enzyme activity.
The aim of study was to analyse ruminal digestibility of NDF in selected total mixed ration -TMR at peak lactation and determinate its impact on the level of rumen fermentation of carbohydrates.

Animals and in situ incubation
Parameters of rumen digestibility of neutral detergent fibre (NDF) in selected TMRs from 15 farms of high producing dairy cows were determined, using methods in situ (Ørskov and McDonald, 1979), where 5 g of sample of each feed was weighed into bags (10 × 20 cm, 53±10 µm pore size) and heat-sealed.Samples of each feedstuff were incubated in duplicate, in the rumen of each cow for 30 h.The in situ procedure was conducted using 3 non-lactating dairy cows (600 kg of body weight) fitted with rumen cannulas.Animals were fed ad libitum lactation diet (CP 15.0%, neutral detergent fibre 36.8%, and acid detergent fibre 25.3% of dry matter) composed of 53% forage and 47% of concentrate.After ruminal digestibility, bags were rinsed with cold water to remove particulate matter.

Analysis
Chemical analysis of nutrients in samples of TMR, and also in undigested food residue after rumen incubation were analyzed for dry mater, crude protein (CP), acid and neutral detergent fibre (ADF, NDF) and starch according to conventional methods (Committee regulation ES No. 152/2009of 27. 1. 2009).Non-fibrous carbohydrates (NFC) was calculated by difference (100 -(CP + (NDF -NDF bound protein) + ash + ether extract)) and energy calculated by regression (Linn et al., 1989, NRC, 2001).The amount of NDF prior to incubation in the rumen and the amount of residue remaining is used for calculating the digestibility of NDF.
Analysis of VFA and metabolic transformation of carbohydrates: Samples of rumen content intended for analysis of fermentative and synthesizing capacity of the rumen were taken 4-6 hours after morning feeding by stomach canulas and stabilised by thymol for conservation of sample.Samples of rumen fluid were strained through 4-layer of gauze, centrifuged 25 min and diluted 1 : 50.VFA in the rumen content were determined in a two-capillary isotachophoretic analyser EA100 (VILLA LABECO, Slovak Republic).The pH of the rumen content was determined potentiometrically with portable electronic pH-meter (JP SELECTA, Spain).
Each parameter was presented by its average (x), standard deviation (SD), respectively.

The nutrient composition of analyzed samples of TMR for dairy cows at peak lactation
Level of rumen fermentation is affected by the amount, type, structure and proportions of carbohydrates in the ration of dairy cows.The concentration of VFA in the rumen at any given time reflects the balance between the rate of production and rate of loss.The nutrient composition of samples of TMR for cows 60-90 days after calving is summarized in Table .1.The nutrient composition of TMR is evaluated by comparing the nutrient content of the ration (TMR) with the recommended nutrient by production phases for dairy cows on farms in our conditions.Analysed content of NDF in TMR was variable with an average of 341.1±27.6 g kg -1 of dry matter (DM) and individual variations from 279.6 g kg -1 DM to 393.2 g kg -1 DM in TMR.National Research Council (2001) recommends NDF concentration to be maintained at 28-30% of dietary DM with at least 75% from forage for the NDF requirement.The upper limit of this recommended range it was increased in 53% samples of TMR, individually on 8 selected farms.
The analysis of neutral detergent fiber (NDF) in tested TMRs for cows at the peak of lactation summarized in table 2 and divided in average value by recommended and increased values.Analyzed values of TMR with NDF over 33% against reference value have an average content of NDF 361.4±17.4g kg -1 DM and digestibility of NDF on average 35.9±6.5%.Analyzed values of NDF directly correlated with forage quality and their vegetation phase of harvest and reduced dry matter intake, as shown by the lower digestibility of NDF.At standardized by NDF (28-33%) in the samples analyzed TMR for the first phase of lactation, the mean amount of NDF 318.0±16.9g kg -1 DM and digestible NDF on average 40.0±5.4%.
The efficiency of the use of NDF in the group with a standard amount of NDF on average 318.0±16.9g kg-1 DM and with a higher proportion of NFC 415.1±20.6 g kg-1 DM showed level of rumen fermentation on medium level (VFA 116.72 mmols l -1 , acetate (A) 61.13±2.9% and propionate (P) 25.63±2.7%)with a ratio A:P (2.47 : 1) tend to favor propionate.In TMR with high contents of NDF on average 361.4±17.4g kg -1 DM and a lower of NFC 367.5±23.1 g kg -1 DM showed a similar level of rumen fermentation, while it has been shift in the ratio A : P with an average of 2.64±0.5 : 1. Analysis and management of rumen fermentation by evaluation of the amount and proportion produced VFA is directly dependent on the level of fermentation in relationship to carbohydrate composition of TMR respectively NDF digestibility of the ration.The proportions of the dominant VFA produced in the rumen vary with diets, microbial growth rates, levels of feeding, and ruminal pH (López et al., 2000).Highforage diets result in the production of greater amounts of acetate and butyrate, while high starch diets result in the production of greater proportions of propionate, although acetate is still the dominant VFA (Beever and Mould, 2000).While the rumen microflora transforms 43-46% of fermentable carbohydrate of diets to the creation of VFA, which provide 80% of energy needs for the animal.

Digestibility of NDF -TMR and rumen fermentation of dairy cows in peak of lactation
The Analysis of digestibility of NDF was et experimental conditions determined by the method in situ at 30 h of incubation in 15 tested samples of TMRs with different levels of structural (NDF and ADF) and non-fibrous (NFC) carbohydrates for dairy cows at peak lactation stage.
Results of digestibility of NDF in TMR a showed significant  (Oba and Allen, 2000).
The comparison of level of rumen fermentation of carbohydrates by the digestibility of NDF showed differences in concentration of rumen acetate and propionate and their ration (A : P), and the pH of the rumen.A higher digestibility of NDF effected level of rumen fermentation of a carbohydrate, it is more intensive with the pH 6.14± 0.2, acetate 59.5±3.8%,propionate 29.5±3.1% and ratio A : P 2.35±0.4: 1 compared to rumen fermentations with lower digestibility of NDF pH 6.37±0.3,acetate 62.9±1.8%,propionate 24.1±2.9% with a ratio A : P 2.71±0.4: 1.The ruminal pH of cattle fed a predominantly forage diet is generally higher, in the range of 6.2-7.0,than those fed diets with greater proportions of concentrates, in the range of 5.5-6.5 (Kolver and de Veth, 2002).The relative concentration of the individual acids is influenced most by concentration, digestibility, and fragility of forage NDF (Allen et al., 2009).

Conclusions
The composition of analysed TMR for high production cows showed the increased content of NDF and limited digestibility of NDF in the first stage of lactation with a negative impact on the level of rumen fermentation and dry matter intake.Calculated and confirmed the capacity of dry matter intake required to secure the energy supply in high-production dairy cows increasing the concentration of non-fibrous carbohydrates and starch to an extent that exceeds the physiologically tolerated concentration and results in acidification rumen environment.

Table 1
Chemical analysis of nutrients in total mixed ration -TMR in g kg dry matter

Table 2
NDF and rumen fermentation of dairy cows at peak lactation -represented by NDF

Table 3
Digestibility of NDF and rumen fermentation TMR for dairy cows at peak lactation