Potential nutritive value of some forages used in ruminant nutrition in Northern Turkey

U Kilic and B Z Saricicek*

University of Cukurova, Faculty of Agriculture, Department of Animal Science, Adana, Turkey
unalkilic@hotmail.com
*University of Ondokuz Mayis, Faculty of Agriculture, Department of Animal Science, Samsun, Turkey
bzehra@omu.edu.tr

Abstract

The aim of study was to determine the potential nutritive value of some forages using chemical composition, in vitro gas production kinetics and some estimated parameters.  In this study,  maize hay-MH, grass hay-GH, alfalfa hay-AH and vetch hay-VH were used. There are significant differences among forages in terms of chemical composition. Crude protein (CP) content ranged from 9.17 to 21.89 %. Neutral detergent fiber (NDF) and  acid detergent fiber (ADF) contents ranged from 45.40 to 57.86% and 28.07 to 36.07%.

There are also significant differences among forages in terms of in vitro gas production, kinetics and some estimates of parameters such as metabolizable energy (ME), net energy lactation (NE_L) and organic matter digestibility (OMD). The ME, NE_L and OMD values of MH, AH and VH were significantly higher than that of GH.

The potential nutritive of alfalfa and vetch hay had a significantly higher than those for maize and grass hay when chemical composition, gas production kinetics and some estimated parameters such as ME, NE_L and OMD of forages were taken into consideration.

Key words: digestibility, energy, gas production, metabolizable

Introduction

It is well know that in ruminant nutrition, forages play such an an important role in providing optimum conditions for ruminal fermentation and production. Although maize, grass, alfalfa and vetch hays were widely used in ruminant nutrition in Northern Turkey there is limited information about their nutritive values of these forages. The more information about nutritive value of forages  is required to be more accurate for ration preparation of ruminant animals.

Chemical composition, in combination with in vitro digestibility, ME and NE_L content can be considered useful indicators for preliminary evaluation of the potential nutritive value of previously limited or uninvestigated of forages (Ammar et al 2005) .

The aim of study was to determine the potential nutritive value of  some forages using chemical composition, in vitro gas production kinetics and some estimated parameters. 

Materials and methods 

Forages and chemical analysis

In this study,  maize hay (MH), grass hay (GH), alfalfa hay (AH) and vetch hay (VH) were used. Maize was harvested at dough stage in Semptember. Alfalfa and vetch harvested at flowering stage in August and July respectively . Grass were harvested in July. Samples were shade-dried and representative dry samples from each plot was taken to laboratory and milled in a hammer mill through a 1 mm sieve for subsequent analysis..

Dry matter (DM) was determined by drying samples at 105 ºC overnight. Organic matter (OM) content was determined by ashing in a muffle furnace at 550 ºC for 8 h. Nitrogen (N) content was determined using Kjeldahl method (AOAC 1990). Crude protein was calculated as N x 6.25. Crude fibre (CF) and ether extract (EE) were determined by the methods described by AOAC (1990) and Nitrogen free extract           (NFE) was determined by difference [100 - (CP + EE + CF +ash)]. Neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) contents were determined by the methods of Van Soest (1982). All chemical analysis were carried out in hexaplicate.

In vitro gas production

Approximately 200 mg dry weight of samples was weighed in triplicate into 100 ml calibrated glass syringes following the procedures of Menke and Steingass (1988). The syringes were prewarmed at 39 ºC before the injection of 30 ml rumen fluid-buffer mixture consisting of 10 ml strained rumen fluid and 20 ml buffer solution into each syringe followed by an incubation in a water bath at 39 ºC.

Rumen fluid from three fistulated SakızxKarayaka rams was collected before the morning feeding and strained through two layers of muslin. Sheep were fed twice daily (08.30 and 16.30) with a diet containing grass hay (%60) and concentrate (%40).

Readings of gas production were recorded at 0, 3, 6, 9, 12, 24, 48, 72 and 96 h of incubation. Total gas volumes were corrected for blank incubations. Cumulative gas production data were fitted to the model suggested by  Ørskov and McDonald (1979) using NEWAY computer package programme.

y = a+b(1-exp^-ct)

Where:

a: the gas production from the immediately soluble fraction (ml), 
b: the gas production from the insoluble fraction (ml), 
c: the gas production rate constant for the insoluble fraction (ml/h), 
a+b: potential gas production (ml),
t: incubation time (h), 
y: gas produced at time “t”

Organic matter digestibility (Menke et et al 1979),  ME (Menke et et al 1979) and NE_L (Menke and Steingass,1988) contents of forages were estimated using equations given below:

OMD ( %)  = 14.88+ 0.889 GP + 0.45 CP + 0.065 Ash

ME, (MJ/kg DM) = 2.20+0.136 GP + 0.0574 CP

NE_L, (MJ/kg DM) = 0.101 GP + 0.051 CP + 0.112 EE

Where:

GP: 24 h net gas production (ml/200mg DM),

CP: Crude protein (%)

EE: ether extract  (%)

Statistical analysis

One-way analysis of variance (ANOVA) was carried out to compare the chemical composition, gas production kinetics, ME, NE_L and OMD values using General Linear Model (GLM) of SPSS 12.0 package programs. Significance between individual means were identified using the Duncan’s multiple range test.

Results and discussion 

Chemical compositions of MH, GH, AH and VH are given in Table 1. There were significant (P<0.001) differences among chemical compositions of forages. 

The gas production and some estimated parameters are given in Table 2.  As can be seen from Table 2 there were significant (P<0.001) differences among forages in terms of gas production.

The gas production of GH at 3, 6, 9, and 12 h incubation times were significantly(P<0.001)  lower than those obtained for other forages whereas gas production of GH at 24, 48, 72 and 96 h incubation times were only significantly(P<0.001)  lower than those obtained for MH.

The gas production kinetics and some other estimated parameters are also given in Table 2. There were also significant(P<0.001)  difference among forages in terms of gas production kinetics and the other estimated parameters such as ME, NEl and OMD values.

The gas production rate of GH was significantly(P<0.001) lower than those of MH and AH whereas b and a+b of  MH were significantly(P<0.001)  higher than those obtained for the other forages. This result is consistent with findings of Mertens et al (1997) and Getachew et al (2004) who found that gas production rate and extent of roughages including grass and ve legume hays are different . In vitro gas production, gas production parameters, estimated energy values from these parameters and OMD values are largely influenced by the differences in the chemical compositions of feedstuffs. The increase in ash and NFE of feedstuffs leads to the decrease in amount of gas produced (Menke and Steingass 1988). Although feedstuffs with the lowest ash content are generally expected to result in the highest gas production values, this is not always the case. In the present study, the gas production of MH, which had the highest NFE content was also found higher. Therefore it is not possible to rule out that the feedstuffs with the highest ash and NFE contents provide the lowest gas production amounts. On the other hand, ME, NE_Land OMD of GH were significantly(P<0.001)  lower than the others.

There is a strong relationship between the OMD of feedstuffs and the rate of gas production (Chenost et et al 2001). It is well known that the OMD of feedstuffs is low in  cellulose-rich feedstuffs,  a similar finding was found in GH of the hays in the present study. The OMD of GH, whose c value was the lowest among the hays was also low. AH was one of the hays with the highest EE content and had the highest OMD values. This finding aggres with the statement by Menke and Steingass (1988) that forages with high EE content also have high digestibility.

Although the feedstuffs with high CP results in low gas production (Chenost et et al 2001), feedstuffs should contain at least 10% CP for optimum microbial activity in the rumen (Norton, 2003). Feedstuffs with below 10% CP can cause a reduction in the microbial activity in the rumen, thus can lead to less gas production.  The hays used in the present study did not affect microbial activity significantly.

GH was the hay with the highest NDF content and had the lowest gas production values (Abdulrazak et al 2000). This can be due to the low digestibility of NDF in GH. However the NDF of MH was higher than that of AH and VH, but MH was found to provide the highest gas production. The finding that the gas productions of grass hays with the highest NDF content were greater than the gas productions of legume hays is in aggrement with the reports by Pell et al (1997) and Mertens et al (1997).

Correlation coefficient (r) of relationship of chemical composition with in vitro gas production kinetics and estimated parameters of forages were given in Table 3.  

NDF and ADF contents were negatively correlated with a, c, ME, NE_L and OMD of forages although NDF content was not significantly correlated with b and a+b.

Conclusions

• The potential nutritive of alfalfa and vetch hay had a significantly higher than thoso for maize and grass hay when chemical composition, gas production kinetics and some estimated parameters such as ME, NEl and OMD of forages were taken into consideration.

  
  

• However, in vivo experiments are required to evaluate how these differences in chemical compositions of forages will affect the ruminant animal performance.

References 

AOAC 1990 Association of Official Analytical Chemists. Official Methods of Analysis, 15th Edition, Volume 1. AOAC, Washington, DC, pp. 69-79

Abdulrazak S A, Fujihara T, Ondilek J K and Ørskov E R 2000 Nutritive evaluation of some Acacia tree leaves from Kenya. Animal Feed Science and Technology 85:89-98

Ammar H, Lopez S and Gonzalez J S 2005 Assessment of the digestibility of some Mediterranean shrubs by in vitro techniques. Small Ruminant Research 119:323-331

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Getachew G, DePeters E J and Robinson P H 2004 In vitro gas production provides effective method for assessing ruminant feeds. California Agriculture 58 (1):54-58

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Pell A N, Doane P H and Schofield P 1997 In vitro digestibility and gas production.  http://www.sbz.org.br/anais1997/simp/palest7.pdf 

Van Soest P J 1982 Analytical systems for evaluation of feeds. In: Nutritional ecology of the ruminant. Cornell University Press. Chapter 6. Ithaka. NY. Pp.75-94

Received 21 February 2008; Accepted 15 March 2008; Published 1 May 2008

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