Volume 130, September 2015, Pages 95–100
Highlights
- •
- The part of concentrate of dairy goats can substitute by low quality date palm (LDP).
- •
- LDP inclustion in diet had no effect on dairy goats performance.
- •
- LDP inclustion in diet improve total antioxidant capacity (TAC) in milk and blood.
- •
- LDP is a cheap by-product and is considered as a natural antioxidant source.
Abstract
This study was conducted to evaluate the effect of feeding low quality date palm (Phoenix dactylifera
L.) (LDP) on the performance, antioxidant status, and ruminal
fermentation in Saanen dairy goats. Eight multiparous Saanen dairy goats
averaging 92 ± 9 DIM and 2050 ± 280 g of milk production were used in a
replicated 4 × 4 Latin square design. Each experimental period lasted
21 days: 14 for adaptation, and 7 for measurements. Experimental
treatments were as follows: (1) diet without LDP (control), (2) diet
containing 6% of LDP (LDP6), (3) diet containing 12% of LDP (LDP12), and
(4) diet containing 18% of LDP (LDP18) (DM basis). The dry matter
intake (DMI) and apparent digestibility were not affected by the
treatments. In addition, there was no difference in milk yield, and milk
composition. Inclusion of LDP in the diet increased total antioxidant
capacity (TAC) as LDP18 had the highest and control had the lowest
concentration of TAC in milk and blood, respectively. No significant
difference was seen in malondialdehyde (MDA) content in milk and blood.
Superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity
had no significant effect across treatment in blood. There was
significant difference in ruminal pH among treatments, yet goats fed
LDP12 and LDP18 had the highest ruminal propionate concentration and the
lowest acetate concentration. With increasing of LDP to diet, the
acetate: propionate ratio decreased while concentration of valerate
increased. The results of this study indicate that LDP can be
substituted with partial replacement of diet in dairy goats ration
without negative effects on animal performance. In addition, inclusion
of LDP in ration improved the antioxidant capacity of dairy goats.
Keywords
- Low quality date palm;
- Performance;
- Antioxidant status;
- Dairy goat
1. Introduction
The date palm (Phoenix dactylifera
L.) has always played an important role in the economy and social life
of the people of arid and semiarid regions of the world. The global
production of date fruits was about 7 million tons in 2010 ( FAO, 2010)
with Egypt, Iran, and Kingdom of Saudi Arabia, being the main producing
countries, with a production of 1.13 million ton, 1 million ton and
983.000 ton, respectively.
In
Iran, about 20–30% of date palm production (approximately 200–300
thousands tones) is considered as a waste product (no edible for human)
either discarded or used in animal feed, because of inadequate texture
(too soft or too hard), or simply due to their low quality (MAJ, 2011).
This by-product is rich in nutrients and bioactive compounds (such as
carotenoids, polyphenols especially phenolic acids isoflavons, lignans,
and flavonoids, tannins, and sterols), which can be extracted and used
as value added materials (Cheikh-Rouhou et al., 2006a and Cheikh-Rouhou et al., 2006b). It can also be used to feed animals with high-energy supplements (Al Yousef et al., 1994).
Typically
dates contain carbohydrate (total sugars, 44–88%), fat (0.2–0.5%),
protein (2.3–5.6%), dietary fiber (6.4–11.5%), minerals (the percentage
of each mineral in dried dates varies from 0.1 to 916 mg/100 g date) and
vitamins (such as vitamin C, B1, B2, A, riboflavin and niacin) (Sawaya et al., 1982, Al-Hooti et al., 1997 and Al-Shahib and Marshall, 2003).
In recent years, the price of energy supplements has been increased
dramatically with the increase of demand of feeds for animals. The
increase in feed prices encouraged nutritionists to search for cheaper
high-energy feed ingredients. LDP could be used as an energy source to
replace a part of the concentrates in the ration. Energy level and
source in the diet affect the animal performance and feed utilization (Nunes, 1994). Rumen microorganisms are also affected by the dietary energy source and level (Sandine, 1979 and Saucier et al., 1992). Al-Dobaib et al. (2009) reported that replacing 30% cereal grain with LDP had no effect on milk yield and composition of Aradi goats. El-Hag et al. (1993)
reported that the addition of discarded dates at the levels of 15 or
25% of the whole DM of ration had no effect on performance of sheep.
The
good nutritional value of dates palm is based on their dietary
antioxidants. Antioxidant date palm content in showed very well (Mansouri et al., 2005 and Biglari et al., 2008). Phenolic compounds of fruit mainly phenolic acids and flavonoids have been shown to possess such benefits as antioxidant (Peterson and Dwyer, 1998).
However, evaluation of LDP as a feed for lactating dairy animal has
been little studied, and its potential to transfer antioxidants into
milk is unknown. Therefore, the present study has been carried out to
evaluate the effect of replacing a part of dietary concentrate by LDP on
the performance, ruminal fermentation, and antioxidant status in Saanen
dairy goats.
2. Materials and methods
2.1. Animals, diets and experimental design
Eight
multiparous Saanen lactating goats averaging 42 ± 3 kg of body weight
(BW) and 92 ± 9 days in milk (DIM) and 2050 ± 280 g of milk yield were
randomly assigned to a 4 × 4 Latin square design. Each experimental
period lasted 21 days.
The
animals were kept in individual metabolic cages in a barn, protected
from rain and wind and equipped with individual troughs to facilitate
quantitative measurement of the feed intake.
The goats were taken care of in accordance with guidelines of the Iranian Council on Animal Care (1995).
Experimental treatments were as follows: (1) diet without LDP
(control), (2) diet containing 6% of LDP (LDP6), (3) diet containing 12%
of LDP (LDP12), and (4) diet containing 18% of LDP (LDP18) (DM basis) (Table 1).
- Table 1. Feed ingredients and chemical composition of experimental diets.
Item Treatment1 Control LDP6 LDP12 LDP18 Ingredients, % Alfalfa hay 50.0 50.0 50.0 50.0 Barley grain 20.0 14.0 8.0 2.0 Whole cotton seed with lint 5.0 5.0 5.0 5.0 Soybean meal 4.5 5.5 6.5 8.5 Wheat bran 19.5 18.5 17.0 15.5 Date palm discard 0.0 6.0 12.0 18.0 Calcium carbonate 0.4 0.4 0.4 0.4 Vitamin-mineral Mix2 0.5 0.5 0.5 0.5 Salt 0.1 0.1 0.1 0.1 Chemical composition, % of DM ME (Mcal/kg of DM) 2.3 2.3 2.4 2.4 CP 14.8 14.7 14.7 14.8 NDF 40.3 40.2 40.1 39.8 NFC3 35.0 35.6 36.2 36.9 Ether extract 3.9 3.9 3.9 3.8 Ca 0.9 0.9 0.9 0.9 P 0.6 0.6 0.6 0.6 TPC4 0.83 0.96 1.08 1.26 -
- 1
- Control, LDP6, LDP12 and LDP18 diets contained 0%, 6%, 12% and 18% of LDP(DM basis), respectively.
- 2
- Contained (/kg of premix; DM basis): 330,000 IU of vitamin A, 60,000 IU of vitamin D, 1000 IU of vitamin E, 160 g Ca, 85 g P, 63 g Na, 45 g Mg, 2,100 mg Zn, 1,500 mg Mn, 535 mg Cu, 12 mg Se, 45 mg I.
- 3
- NFC calculated as 100 − (CP + Ash + NDF + EE).
- 4
- TPC Total Phenolic Compounds.
Experimental
diets were formulated to meet the requirements according to National
Research Council (NRC, 2001). Diets were fed as a Total Mixed Ration
(TMR) with 50:50 forage to concentrate ratio and were formulated to have
similar Crude Protein (CP), Neutral Detergent Fiber (NDF) and Non
Fibrous Carbohydrate (NFC) (Table 1). The diets were offered twice daily ad libitum (07:00 and 15:00 h) and the goats had free access to fresh water.
2.2. Sample collections and calculations
NDF
and Acid Detergent Fiber (ADF) were determined during a 7-days
measurement period. The animals were weighed at the beginning and at the
end of each measurement period. For every diet, feed and apparent
digestibility of DM, NDF, CP and Organic Matter (OM) were determined.
Feed intakes and feed refusals were collected before the morning feeding
and weighed daily during the measurement period. DMI was calculated by
the difference between total amount of dry matter offered and refused.
Fecal
samples of each goat were collected through the 5-day collection
periods and then dried in an oven. Daily dried samples were ground and
later composited for each 5-day periods. Feeds and orts were sampled
daily during the collection period and were composited further.
Composite samples of the TMR, feed refusal and feces were dried in an
oven, then ground to pass through a 2-mm screen and stored for later
analysis. Rumen fluid samples were taken from animals by stomach tube
with a vacuum pump 2 h after the morning feeding on days 18 and 19. The
pH values of the fluid samples were determined and recorded using a pH
meter (METROHM 691). Approximately, 100 ml of ruminal content was
strained through four layers of cheesecloth. A subsample of 5 ml was
combined with 5 ml of HCl 0.2 N for NH3-N analysis. Another
sample was put into a plastic bottle containing 1 ml of 0.25 g/ml
metaphosphoric acid and 1 ml of 0.006 g/ml 2-ethylbutyric acid (internal
standard), which was for volatile fatty acid (VFA) analysis.
Ruminal
subsamples were frozen at −20 °C until the conductance laboratory
analyses. On day 21 of each period, 10 ml blood samples were collected
from the jugular vein of each goat, just 2 h after the morning feeding.
Blood samples were then centrifuged at 3000 × g for 10 min,
followed by separation serum finally frozen at −20 °C. One whole blood
sample was collected in a tube containing potassium ethylene diamine
tetra-acetic acid (K-EDTA) for antioxidant activity content and stored
at −20 °C for later analysis. Within 1 h of the bleeding, hemoglobin
(Hb) content was determined by a commercial colorimetric kit (Sigma
Diagnostic, Milan, Italy), blood samples were centrifuged at1400 g for
20 min at 48 °C and plasma was thus harvested. Goats were milked two
times daily at 07:00 and 19:00 h. Milk production was recorded daily for
each animal. A daily composite milk sample from the morning, and
afternoon milking was taken during the collection period. Fresh
subsamples were analyzed daily for chemical composition. One sample out
of each sampling day without preservative was kept frozen at −20 °C to
determine antioxidant concentrations (TAC and MDA).
2.3. Laboratory analysis
Ash
(AOAC 2005, method 942.05) and CP (Kjeldahl N × 6.25) were determined
by the block digestion method using copper catalyst and steam
distillation into boric acid (method 2001.11) on 2100 Kjeltec
distillation unit according to Association of Official Analytical Chemists (AOAC) (2005). NDF and ADF were determined by Van Soest et al. (1991).
The sodium sulphite and α-amylase were not used and both NDF and ADF
were expressed exclusive of residual ash. Total Phenolic Compound (TPC)
was determined by Folin–Ciocalteu reagent using tannic acid as a
standard (Makkar, 2000).
Acid-insoluble ash (AIA) content was used as an internal marker to
determine the apparent digestibility of DM, OM, CP and NDF as reported
by Van Keulen and Young (1977). Ruminal fluid samples were thawed, centrifuged at 1200 × g
for 10 min, where the supernatant fluid was analyzed for VFA by gas
chromatography (Hewlett-Packard,model 5890, Avondale, PA). The NH3-N
concentration of rumen fluid samples was analyzed by the procedure
developed by Weatherburn (1967).
Serum urea N, glucose and protein were determined using an autoanalyzer
(Biosystems A 15; 08030 Barcelona, Spain). Whole blood glutathione
peroxidase was measured using a Randox kit (Randox Laboratories, London,
UK) according to instruction of the kit.
Superoxide dismutase activity was measured using a Randox kit (Randox Laboratories,London, UK), The GPX,
catalase and SOD activity were expressed as U/g of hemoglobin. TAC in
serum and milk was determined by Ferric reducing antioxidant power
(FRAP) method.
The level of malondialdehyde in serum and milk was determined using thiobarbituric acid method according to Placer et al. (1966). the results were obtained in terms of nmol/ml and determined using the colorimetric method.
Milk
samples were analyzed for protein, fat and lactose contents with a
Milko-Scan 605 analyzer (Foss Electric, Hillerød, Denmark). Fat
corrected milk (4% FCM) was defined as milk with 4% fat (National
Research Council, 2001).
2.4. Statistical analysis
Mixed procedure of SAS (9.1) was used to analyze data for a Latin square design.
The
data collected over the time were analyzed using repeated measures
technique. Least squares means procedure (LSMEANS) was used to detect
the difference between dietary treatments.
The data were analyzed using the following statistical model:
Yijk=μ+Ti+Pj+CK+ϵijk

3. Results
3.1. Animal performance
The addition of LDP to the diet of the dairy goats did not affect (P > 0.05) on DMI (Table 2)
since DMI was similar for all treatments. The difference among the four
groups for milk yields, 4% FCM and milk composition (Protein, lactose,
total solids, milk fat, and solids not fat) were not significant (P > 0.05). The mean digestibility of DM, OM, NDF and CP is listed in Table 3. Digestibility of nutrients was similar across treatments not affected by the treatments (P > 0.05).
- Table 2. Effect of treatment on dry matter intake, milk yield and composition.
Item Treatmentc Control LDP6 LDP12 LDP18 SEM P Value Intake of DM (g/d) 1655 1731 1662 1745 95 0.28 Milk production (kg/d)d 1.66 1.62 1.59 1.61 0.10 0.48 4% FCM 1.54 1.44 1.41 1.41 0.12 0.29 Milk Composition (%) Fat 3.39 3.24 3.18 3.12 0.19 0.28 Protein 2.96 2.98 2.95 3.00 0.03 0.57 Lactose 4.40 4.43 4.35 4.46 0.05 0.25 Solid not fat 8.07 8.16 8.06 8.23 0.08 0.34 Total solids 11.46 11.41 11.24 11.36 0.23 0.76 Milk yield (g/d) Fat 56.68 53.32 51.89 51.18 5.75 0.32 Protein 49.50 48.55 47.21 48.51 3.37 0.45 Lactose 73.83 72.10 70.91 72.20 5.18 0.32 Antioxidant activity of milke TAC (mmol/lit) 1.18b 1.50a 1.66a 1.69a 0.10 0.01 MDA (nmol/ml) 2.83 2.92 2.88 2.83 0.09 0.90 -
- c
- Control, LDP6, LDP12 and LDP18 diets contained 0%, 6%, 12% and 18% of LDP(DM basis), respectively.
- d
- 4% FCM was calculated as {(0.4 kg of milk) + (15 kg of milk fat)}.
- e
- TAC = total antioxidant capacity, MDA = malondialdehyde.
- Table 3. Effect of treatment on apparent total tract digestibility of diets.
Item Treatmenta Control LDP6 LDP12 LDP18 SEM P Value Diet digestibility, % DM 67.17 67.64 66.46 64.62 1.30 0.81 OM 64.90 66.99 65.61 67.67 1.26 0.68 NDF 51.92 50.34 50.56 51.72 0.93 0.88 CP 65.99 65.14 66.48 68.11 1.31 0.93 -
- a
- Control, LDP6, LDP12 and LDP18 diets contained 0%, 6%, 12% and 18% of LDP(DM basis), respectively.
3.2. Antioxidant activity and blood metabolites
The effects of diets on TAC and MDA in milk are presented in Table 2. The Effect of feeding LDP on TAC was significant (P < 0.05)
as the control had the lowest TAC compared with other treatments. In
addition, increasing LDP level of TAC content was increased although the
difference between LDP6, LDP12, and LDP18 was not significant (P > 0.05).
The
feeding of LDP had no effect on the content of MDA in milk. The effect
of treatments on antioxidant activity and blood metabolites are
demonstrated in Table 4. Treatments showed no differences with regard to blood metabolites (serum urea N, glucose, and triglyceride) (P > 0.05). The concentrations of TAC of blood among treatments were significant (P = 0.01).
The goats fed with LDP18 diet had the highest content of TAC when
compared to other treatments. Also, the feeding of LDP12 and LDP6 had a
higher content of TAC compare to control with a significant growth (P = 0.01). However, other antioxidant parameters (SOD, GSH-Px and MDA) were not affected by the treatments (P > 0.05).
- Table 4. Effect of treatment on antioxidant activity and blood metabolites.
Item Treatmentd Control LDP6 LDP12 LDP18 SEM P Value Blood metabolites (mg/dl) Serum urea N 17.36 17.70 17.50 17.40 0.32 0.85 golucose 64.64 63.43 63.87 63.13 1.19 0.29 triglycride 75.09 74.62 75.51 74.44 1.74 0.45 Antioxidant activity of bloode TAC (mmol/lit) 0.68c 0.74b 0.79b 0.85a 0.01 0.01 MDA (nmol/ml) 2.31 2.22 2.28 2.25 0.10 0.94 SOD (U per g Hb) 1726 1655 1628 1644 44 0.26 GSH-Px (U per g Hb) 44.13 44.46 46.59 44.57 3.04 0.93 -
- d
- Control, LDP6, LDP12 and LDP18 diets contained 0%, 6%, 12% and 18% of LDP(DM basis), respectively.
- e
- TAC = total antioxidant capacity, MDA = malondialdehyde, SOD = superoxide dismutase, GSH-Px = glutathione peroxidase.
3.3. Rumen fermentation parameters
The mean of ruminal fermentation parameters are presented in Table 5. Goats fed the LDP18 and LDP12 diets had lower ruminal pH compared with those fed the control diet (P = 0.02). Likewise, the difference between LDP6 and LDP18 was significant (P = 0.02); however, the concentration of ammonia-N did not differ between treatments.
- Table 5. Effect of treatment on ruminal fermentation parameters.
Item Treatmentd Control LDP6 LDP12 LDP18 SEM P Value Ruminal parameters Ruminal fluid pH 6.48a 6.35ab 6.24bbc 6.11c 0.05 0.02 Runinal NH3-N, mg/dl 13.52 13.34 13.43 13.35 0.42 0.98 Total VFA (mM) 59.40 60.65 61.60 61.62 1.72 0.74 Individual VFA (proportion of total VFA) Acetate (%) 68.37a 66.02ab 63.43bc 62.88c 0.97 0.01 Propionate (%) 19.28c 20.28bc 23.00ab 23.70a 0.89 0.03 Butyrate (%) 10.23 11.25 10.80 10.86 0.87 0.87 Valerate (%) 0.83b 0.98ab 1.10a 1.13a 0.07 0.04 Isovalerate (%) 1.26 1.44 1.49 1.55 0.09 0.26 Acetate/propionate 3.54a 3.27a 2.78b 2.66b 0.14 001 -
- d
- Control, LDP6, LDP12 and LDP18 diets contained 0%, 6%, 12% and 18% of LDP(DM basis), respectively.
Although total VFA concentration was not affected by the treatments (P > 0.05), increasing dietary LDP content raised ruminal molar proportions of propionate (P = 0.03) and valerate acid (P = 0.04), whereas it decreased the ruminal molar proportions of acetic acid and acetate/propionate ratio (P = 0.01).
4. Discussion
The milk yield was not affected by the treatments (Table 2) possibly due to similar DMI (Table 2). Addition of dates to the ration of ruminants can improve the productivity of lambs and positively affect Animal performance (Al-Dabeeb, 2005). The results of our study are similar to the findings of El-Hag et al. (1993)
who reported that the addition of discarded dates at the levels of 15
or 25% of the whole DM of ration had no effect on feed intakes. It was
contrary to the findings of Al-Dabeeb, (2005)
who reported feeding low quality date palm at the levels of 10 or 20%
in fattening Najdi sheep ration affected on DMI Lambs in the control
group consuming more feed (1167 g/day) than the other two groups fed
date-supplemented diets (1028 g/day for D10 and 877 g/day for D20). Al-Dobaib et al. (2009)
reported that the addition of discarded dates at the level of 30% of
ration had no effect on milk production and composition in Aradi goats,
similar to our study. Apparent nutrients digestion was not affected by
dietary treatments (Table 3). In agreement with our study, Hmeidan et al. (1993)
observed that the addition of 33% discarded dates did not negatively
affect the feed intake, digestibility and nitrogen retention of Najdi
lambs. Al-Dabeeb, (2005)
reported that addition of 10 or 20% ration with low quality date palm
in fattening Najdi sheep ceases the reduction in digestibility of all
nutrients (except EE) as dates in the diets increases. The discrepancies
between the results of the two studies may have been due to the fact
that the animal use in the present study was dairy goat, while the
animal employed in their experiment was fattening Najdi sheep. From the
producers' point of view, our results for DMI and milk yield were under a
hot climate, which may be an encouraging factor for the producers in
the arid and semi-arid countries to overcome the problem of high price
animal food in this area using diets including LDP.
Addition of LDP to diet increased the concentration of TAC in milk (Table 2) and blood (Table 4),
and as LDP concentration was elevated, so did the TAC in both milk and
blood. Antioxidant activity and phenolic content of date fruit have been
reported by many researchers (Al-Farsi et al., 2005; Mans05; Allaith, 2008, Biglari et al., 2008 and Amorós et al., 2009).
Phenolic compounds in plants have protective properties against
oxidation, disease and predation. These compounds, including the large
flavonoid family, are the focus of numerous studies to elucidate their
role in human health (Singh et al., 2007).
Salinas-Rios et al. (2015)
reported that inclusion of coffee pulp (a source of antioxidant) in the
sheep diet had no effect on FRAP levels in the plasma but MDA decreased
with inclusion of 12% coffee pulp in the diet compared to 6% and 0%
levels. The discrepancies between the results of the two studies may
have been due to the fact that in the experiment of Salinas-Rios et al. (2015) coffee pulp was substituted with alfalfa hay which is a forage with high antioxidant content (Cao et al., 1996), while in present study LDP was substituted with wheat bran (Table 1). Similar to this study, Emami et al. (2014)
reported that addition of Pomegranate seed pulp (a byproduct contain
high polyphenol) to kids ration at a level of 15% increased the
concentration of TAC in plasma compared to the control diet. Recently, Aguiar et al. (2014)
found that feeding phenolic compounds from propolis extracts to dairy
cows improved the antioxidant capacity of milk compared with that in the
control. Generally, a higher intake of natural antioxidants results in
transfer of these molecules to animal tissues with a resultant increase
of total antioxidant capacity (Descalzo and Sancho, 2008).
Also, the higher TAC in plasma of goats fed with DPS levels in the diet
was probably a result of increased absorption of antioxidants from the
gastrointestinal tract and transfer of these compounds into milk. As
goats fed with LDP had the highest antioxidant activity in milk, they
may be producing milk with the highest oxidative stability. The effects
of treatments on the concentration of MDA were not significant in the
milk and blood (P > 0.05). As an end product of lipid peroxidation, formation of malondialdehyde is accelerated by oxidative stress (Horie et al., 1997)
and thus detection of MDA can reflect the level of oxygen free radicals
and the extent of lipid peroxidation. Congruent with our study, Zhou et al. (2012)
found that supplementation of tea saponins (Ilex kudingcha C.J. Tseng)
to goat ration had no effect on MDA, SOD and GSH-Px in plasma. Habib and Ibrahim, (2011) reported that feeding 7 or 14% of date seed to rats ration increased MDA content in both serum and liver. Di Trana et al. (2006)
investigated the effect of hot season and nutrition on the oxidative
status in dairy goats. The concentration of SOD, GSH-Px and α-tocopherol
was not affected by nutrition, but these factors were influenced by
season. They concluded that in summer lactating goats may have
experienced moderate oxidative stress. It seems that, seasonal rather
than nutritional factors have a more pronounced effect on oxidative
status markers in dairy goats. As our study was conducted from April to
August, (half of the experiment was in spring, a half in summer), the
goats were in barn and protected against hot stress, and the
temperatures were favorable, so with regard to these factors, the goats
were probably not under oxidative stress. Eventually, note that SOD,
GSH-Px and MDA were not significant. Treatments had no any effect on
blood metabolites (serum urea N, glucose, and triglyceride), as chemical
compounds of all diet were relativity similar, so expect the difference
among treatments were not significant. Date fruit consists of 70–88%
carbohydrates, most of which is in the form of sugars, mainly glucose,
sucrose and fructose. Because of this, the fruits are a great source of
energy and it is approximated that 100 g of the flesh can provide
314 kcal of gross energy (Al-Farsi and Lee, 2008).
Due
to the rapid fermentation of sugars compared to the other carbohydrate
fractions, rumen pH is expected to be lower for diets containing sugars.
However, many studies in the literature showed that rumen pH is not
affected when dietary starch sources are partly replaced by sucrose (Sutoh et al., 1996, McCormick et al., 2001 and Broderick et al., 2008) or lactose (Schingoethe et al., 1980 and DeFrain et al., 2004). Furthermore, some studies reported that rumen pH increases (Chamberlain et al., 1993 and Heldt et al., 1999) or tend to increase (Penner et al., 2009 and Penner and Oba, 2009) with the partial replacement of dietary starch sources with sugar. Recently in congruence with our results, Razzaghi et al. (2014)
reported that feeding sucrose to Saanen dairy goats decreased ruminal
pH in comparison to the control diet. Collectively, there is little
evidence in the literature to support the concept that increasing
dietary sugar concentration decreases rumen pH. Discrepancy between the
current study and the mentioned previous studies may be difference in
sugar type as in present study we used date palm (combination of various
sugars) while in previous studies the sugar directly fed to animals, as
well as the type of animal goat or cow can also affect rumen pH (Moharrery et al., 2014). The feeding of LDP decreased acetate and acetate/propionate ratio and increased propionate and valerate (Table 5).
This finding is contrary to earlier reports (Ribeiro et al., 2005, Mullins and Bradford, 2010 and Martel et al., 2011)
that sugars increase the ruminal concentration of butyrate and not
propionate. Our result is however congruent with the finding of Razzaghi et al. (2014)
who reported feeding sucrose to saanen dairy goats decreased acetate,
acetate: propionate ratio while increased propionate and valerate
concentrations in the rumen. These results confirmed the results related
to milk fat that as LDP to ration increases, the concentration of fat
drops (Table 2).
Some
studies have reported that molar proportion of butyrate in rumen fluid
is not affected by feeding sugars. It should be noted that butyrate
production in the rumen is not the same as butyrate concentration
because the concentration is a function of production, absorption, and
passage of butyrate.
Because absorption of butyrate is faster than that of acetate or propionate (Leek, 1993),
butyrate concentration in rumen fluid, either as molar-% or mM, may
underestimates the actual butyrate production. Studies where sugar
partly replaced dietary starch showed that the molar proportion of
propionate declines (Heldt et al., 1999 and DeFrain et al., 2004) or is not affected (Kellogg and Owen, 1969b and Kellogg and Owen, 1969a; Vallimont et al., 2004).
Some studies have revealed that feeding sugars can increase the
concentration of valerate in the rumen, which can be formed partly from
condensation and reduction of acetate and propionate. Heldt et al. (1999)
noted that feeding sucrose in place of starch increased valerate
concentration in the rumen, consistent with our results. The development
in the proportion of propionate and reduction of proportion of acetate
in diets containing LDP results in decreased rumen pH. Inconsistencies
observed in this study in comparison with others, may be due to greater
dietary non-fiber carbohydrate intake (Table 1) or ruminant species (cow or goat) in the present study.
5. Conclusion
The
results of this study indicated that substitution part of dietary
concentrate with LDP in the ration of dairy goats had no effect on DMI
and nutrients digestibility. Milk yield and composition were not
affected by treatments. Inclusion of LDP in the diet increased TAC in
both blood and milk compare control diet. In regard to, LDP is a cheap
by-product and is considered as a natural antioxidant source. Therefore,
it can be used as an alternative source for small ruminants in arid and
semi-arid regions particularly in the Persian Gulf region.
Acknowledgements
The
authors would like to acknowledge Department of Animal Science of
University of Birjand for their cooperation. Also, we thank H. Rajaei
Sharifabadi for his great assistance in various aspects of this study.
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