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Research Article
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Determination of Digestibility and Nutritive Value of Iranian Alfalfa Varieties Using In vivo Technique in Sheep
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Naser Maheri-Sis,
Afshar Mirzaei-Aghsaghali,
Ali Mirza-Aghazadeh
and
Amir Reza Safaei
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ABSTRACT
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The aim of this experiment was to determine the potential nutritive value of Hamedani (HAM) and Kareyonge (KAR) using the chemical composition, Dry Matter Digestibility (DMD), Organic Matter Digestibility (OMD) and Metabolizable Energy (ME) content. Each of the two alfalfa varieties were offered ad libitum to three Gezel rams. No significant difference found between Dry Matter (DM), Crude Protein (CP), Ash and Ether Extract (EE) contents of two alfalfa varieties, although the difference for Crude Fiber (CF), Neutral Detergent Fiber (NDF) and Acid Detergent Fiber (ADF) were significant (p<0.001). Dry Matter Intake (DMI), Organic Matter Intake (OMI) and Crude Protein Intake (CPI) were similar in HAM and KAR hays (p>0.05). Dry Matter Digestibility (DMD) and organic matter digestibility in HAM hay were significantly (p<0.01) higher than that of KAR hay, whereas Crude Protein Digestibility (CPD) in HAM hay was similar than that KAR hay (p>0.05). Digestible Organic Matter in Dry Matter (DOMD) and ME intake in HAM were significantly (p<0.01) higher than that KAR hay. Calculations based on in vivo digestibility indicate that HAM alfalfa can have a higher inclusion than of KAR alfalfa in diets for ruminants because of lower cell wall (NDF and ADF) contents, greater DOMD and ME intake.
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INTRODUCTION
Forages provide 83% of the protein requirements of beef cattle and 90% of the protein requirement of sheep (Griffith, 1978). Ruminants are the predominant forage utilizer among animals, because ruminant animals possess rumen microbes, which can digest cellulose and use NPN to produce high quality microbial protein (Wechsler, 1981). It is well known that forage has an important role in ruminant nutrition in terms of providing energy, protein and minerals (Chriyaa et al., 1997). Nutritive value of forages depends on their dry matter and digestibility and voluntary dry matter intake. Predictions of voluntary intake and digestibility of forages by ruminant animals have long been a research priority in animal nutrition (Kamalak et al., 2005a). Although the effect of maturity on the nutritive value of forage obtained from different plants is well established (Buxton, 1996; Kamalak et al., 2005b, c; Bal et al., 2006) there are little information about the nutritive value of Iranian hays especially common alfalfa varieties.
The aim of this experiment was to determine the potential nutritive value of KAR and HAM hays harvested at late maturity by using the chemical composition, in vivo method and ME content.
MATERIALS AND METHODS
Sample Collection
Two alfalfa varieties (Hamedani and Kareyonge) used in this study were randomly
sampled from ten alfalfa farms at near West Azerbaijan, Iran (located in the
Uromia and Miandoab cities) in summer 2005. The samples were transported to
the laboratories of Islamic Azad University-Shabestar Branch.
Both alfalfa, at harvested, were estimated to be at late maturity (both verities in mid to late bloom). Samples were collected, oven-dried at 60°C for 48 h, ground (5 mm screen) and prepared for chemical analysis.
Chemical Analysis
Dry Matter (DM) was determined by drying the samples at 105°C overnight
and ash by igniting the samples in muffle furnace at 525°C for 8 h and Nitrogen
(N) content was measured by the Kjeldahl method (AOAC, 1990). Crude Protein
(CP) was calculated as Nx6.25. Neutral Detergent Fiber (NDF), Acid Detergent
Fiber (ADF) and Acid Detergent Lignin (ADL) were determined by procedures outlined
by Goering and Van Soest (1970) with modifications described by Van Soest et
al. (1991) sulfite was omitted from NDF analysis. Hemicellulose and cellulose
were calculated as NDF-ADF and ADF-ADL-AIA, respectively (Andrighetto et
al., 1993).
Estimation of Energy Value|
Gross Energy (GE) was measured in an adiabatic bomb calorimeter. Metabolizable
Energy (ME) values were estimated from in vivo DOMD values according
to AFRC (1993).
Voluntary Feed Intake and Digestibility Trails
Each of the two alfalfa varieties were offered ad libitum to three
Gezel rams (1.5 year old, avg initial BW 55 kg) kept in metabolism cages to
enable accurate determination of feed intake and allow easy collection of faeces.
The forages were fed twice daily at 08:30 and 16:30 h and fresh drinking water
and mineral salt licks were freely available. The animals were adapted each
forage for two weeks, followed by balance trails of seven days (total period
of digestibility trials were 42 days), in which daily measurement of food intake
and fecal excretion were made. Sub-sample of forages was taken and data on their
daily intake (g DM kg-1 LW0.75) and digestibility in
vivo were obtained.
Statistical Analysis
All of the data were analyzed by using software of Statistical Analysis
Systems (1985) and means of both varieties were separated by independent-samples
t-test (Steel et al., 1980).
RESULTS AND DISCUSSION
There was considerable variation between forages in terms of chemical composition
(Table 1). The CF content of KAR hay was higher than that
HAM hay (p<0.05). On the other hand ADF and NDF contents ranged from 29.4±0.8
to 34.4±0.2 and 43.1±0.7 to 49±0.2 for HAM and KAR hays,
respectively. The ADL content of both hays were similar (HAM: 6.3±0.7
and KAR: 7.3±0.1). The cell wall (ADF and NDF) and ADL contents of HAM
hay were similar than those reported by Coblentz et al. (1998), lower
than that reported by Torrent et al. (1994) and higher than that reported
by Kamalak et al. (2005a). The different result reported by several researchers
about alfalfa hay cell wall content may be due to differences in maturity (Coblentz
et al., 1998; Gulsen et al., 2004; Kamalak et al., 2005b,
c), variety, environmental conditions, agronomic factors (Wechsler, 1981; Buxton,
1996) and leaves to stem ratio (Coblentz et al., 1998). It is well established
that the cell wall content of forages increase with increasing maturity (Gulsen
et al., 2004; Kamalak et al., 2005b, c). The GE content for HAM
and KAR hays were similar and ranged from 4219±34 to 4250±89 kcal
kg-1, respectively. No significant differences were found between
crude protein content of HAM and KAR. The CP content of HAM and KAR hays were
lower than that reported by Coblentz et al. (1998) and Kamalak et
al. (2005a) and similar with data of Abas et al. (2005). The ash
content, which is an index of mineral contents, was similar (10.33±0.57)
in HAM and KAR hays. The ash content of both hays consistent with that reported
by Kamalak et al. (2005a).
Table 1: |
Chemical composition of KAR and HAM hays |
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DM: Dry Matter; OM: Organic Matter; CP: Crude Protein; CF:
Crude Fiber EE: Ether Extract; NDF: Neutral Detergent fiber; ADF: Acid Detergent
Fiber; ADL: Acid-Detergent Lignin; GE: Gross Energy; *The data are mean
value±standard deviation (SD) of three replicates; Sig. = Significant
level; NS = Non-significant; **p<0.01; ***p<0.001 |
Table 2: |
A comparison of the DM, OM, CP and ME intake, apparent digestibility coefficients
and digestible OM and CP contents in sheep |
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a: DOMD : Digestible organic matter
in the dry matter; b: ME value predicted after AFRC (1993); Sig.
= Significant level; NS : Non Significant; **: p<0.01; ***: p<0.001 |
DMI, OMI and CPI (kg per day and g kg-1 W0.75) in HAM and KAR hays were similar (p>0.05) (Table 2). DMD and OMD (%) in HAM hay were significantly (p<0.01) higher than that KAR hay; but CPD (%) in KAR and HAM hays was similar (p>0.05). The reason why HAM hay had higher DMD and OMD than that of KAR probably is low cell wall content. Science there have a negative correlation between cell wall content and nutrient digestibility (Kamalak et al., 2005a). The DMD, OMD (%) and DMI (g kg-1 W0.75) for KAR hay were similar with those values reported by Torrent et al. (1994), Kamalak et la (2005a) and Abas et al. (2005) in alfalfa, But lower than HAM hay. The DMD, DMI and CPI of HAM hay obtained in this study were consisted with those reported by Vanzant et al. (1998) and Martin et al. (2000). The DMD, DMI, CPD and CPI contents of HAM hay were lower than those obtained by Phillips et al. (2002). The DOMD, ME and ME intake of HAM hay were significantly (p<0.01) higher than that KAR hay. The calculated ME content of both alfalfa varieties were higher than that of reported Abas et al. (2005).
CONCLUSIONS
In conclusion, results obtained from the present study indicated that, the cell wall content of HAM hay was lower than that of KAR and DMD, OMD, ME content and ME intake of HAM higher than those of KAR. Overall it seems that nutritive value and digestibility of HAM were greater than those of KAR hay.
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