Journal of Environmental Science (2009) vol. 19 (1):89-106
Effect of different buffers on rumen kinetics of sheep fed halophyte plants
S.A. Attia-Ismail1; H.M. Elsayed2; A.R. Asker1 and E.A. Zaki1
1- DesertResearchCenter, P.O. Box 11753, Matareya, Cairo, Egypt
2- Faculty of Agriculture, AinShamsUniversity, Shobra Elkhema, Cairo, Egypt
ABSTRACT
The purpose of this paper was to investigate the effect of different buffers on rumen kinetics of sheep fed halophyte plants. Three different buffers were used in this study; Bentonite, MgO and KCl. Rumen fluid was withdrawn from sheep fed on Berseem hay and barley grains on maintenance basis. Stomach tube was used to withdraw rumen liquor at 0, 2, and 4 hrs postfeeding randomly from 3 animals.Parameters of incubations were TDS, pH and Ec. Rumen samples were double cheesecloth squeezed and incubated with either berseem hay or atriplex nummularia. Different concentrations of the buffers were 0.25%, 0.5% or 0.75% of total ration dry matter.Parameter measurements were taken at 0, 15, 30 and 60 minutes after the initiation of incubation.
Magnesium oxide (MgO) raised pH value significantly (P<0.05). Both bentonite and KCl had almost identical pH values (6.56 and 6.57 for bentonite and KCl, respectively), while that of MgO was 7.44. Increased bentonite concentrations decreased ruminal pH (6.74, 6.50 and 6.42 for 0.25, 0.50 and 0.75%, respectively). Atriplex produced lower pH value than berseem hay did (6.74 and 6.97 for atriplex and bersem hay, respectively). It was noticed that the effect of time of incubation had no significant effect after 30 minutes as there was no significance thereafter.
Bentonite showed the least values of Ec and TDS (6.74mmols/cm and 3.15 mg/l for Ec and TDS, respectively). Elevated concentrations of bentonite did not affect either Ec or TDS values significantly.Atriplex increased Ec value (7.45 mmoles/cm) significantly than did berseem hay (6.40 mmoles/cm).As time of incubation progressed, the value of Ec increased but not significantly.
Addition of potassium chloride produced the highestTVFA's (10.71 mleqv) significantly (P<0.05). The 0.50% concentration of Bentonite produced the highest TVFA's concentration (10.30 mleqv). The 0.75% concentration of MgO produced also the highest concentration of TVFA's (12.11 mleqv), while the 0.25% concentration of KCl produced the highest concentration of TVFA's (12.11 mleqv). Atriplex significantly (P<0.05) produced more TVFA's than did berseem hay (10.54 and 9.66 mleqv for atriplex and hay, respectively).
It is concluded that under in vitro conditions, both of Bentonite and potassium chloride were not varying that much to use either of them in vivo.
INTRODUCTION
The human requirements for animal protein makes it increasingly important to utilize all available pastureland, which to a large extent lies in climatically unfavorable regions. In these areas, the animals often have to consume the only available feed resource which is halophytic plants. These plants have high concentrations of salts. The ingestion of great amounts of salts has certain impacts and affects rumen metabolism through the influence on rumen kinetics. The impact of such constraint is expected to animal performance.
A goal of ruminant microbiologists and nutritionistsis to manipulate the ruminal microbial ecosystem toimprove the efficiency of converting feed to productsconsumable by humans (Martin, 1998).
If the rumen pH is not optimal (6.2-6.5), microbial yield and efficiency drops, dry matter intake declines, and metabolic disorders can increase. Normally, the ruminants produce large amount of volatile fatty acids and these acids need to be buffered. Additionally, the feeding of salt plants that are present in the desert regions usually places another burden of ions in the rumen and needs more buffering capacity. Ruminants that feed on salt plantsare expected to secrete more saliva and have a higher ruminal pH than those fed grains.Some scientists hypothesized that the ruminal fluid of animals fed forge might have a higher buffering capacity. However, there is little support to thishypothesis. Because homeostatic mechanisms insure that the osmotic pressure of rumen is always in close proximity to the osmotic pressure of the plasma and interstitial fluids, the bicarbonate concentration of the rumen cannot change significantly. When animals are fed forage or halophytes, rumination and saliva flow are stimulated. If the ruminal pH is less than 5.7, the ability of bicarbonate to act as a buffer declines, but volatile fatty acids (VFA's) can prevent additional reductions in pH.
Buffers are a combination of weak acid and its salt which resists changes in pH or hydrogen ion concentration. An ideal rumen buffer should tie up hydrogen ions near the desired rumen pH. An alkalinizing or neutralizing product increases the pH in the rumen fluid. Several products can be incorporated into buffer packs.
Sodium bicarbonate is the standard buffering agent. Ithas been extensively studied.Buffers at a pH 6.25, increase rumen osmolarity, and shift VFA (volatile fatty acids) patterns.
Magnesium oxide is a source of magnesium (54 percent by weight) and functions as an alkalinizer.Magnesium oxide and magnesium carbonate have been used in high-grain, restricted-roughage diets for prevention of reduced milk fat content. These magnesium compounds often are utilized as antacids in ruminant diets, but their effectiveness in neutralizing acid in the rumen differs(Schaefer et al, 1982).
Bentonite is a clay mineral used as a pellet binding agent. It can swell in the rumen, shifts rates of passage, and adsorbs minerals and ammonia. It does not have buffering capacity.Bentonite clays have been used extensively in the feed pelleting process to improve the binding quality of pellets. They have also been shown in some instances to reduce the incidence of acidosis in sheep and cattle changed rapidly to a high grain (Dunn et al, 1979). It appears that Bentonite may act as buffers (Aitchison, et al., 1986) to prevent very rapid reductions in rumen pH during fermentation.
Croom et al. (1982) showed that salts ofsaliva (mainly NaHCO3) and mineral salts increasedruminal liquid dilution rates and, inseveral cases, increased feed intake in steersand dairy cows.As liquid dilution rate increases,the growth of ruminal microbes increasesand the amount of substrate needed formicrobial maintenance decreases (Isaacson etal., 1975), thus increasing efficiency of fermentation.
The purpose of this paper is to investigate effect of different buffers on rumen kinetics of sheep fed halophyte plants.
MATERIALS AND METHODS
This experiment was carried out at Maryout Experimental Research Station, 35 Km south west of Alexandria
1 – Animals and management
Prior to the experiment, animals were drenched for internal parasite control. Twenty four adult Barki rams were used in the experiment. Animals were weighed before the experiment.
2- Feeds
Animals were fed a standard basic ration that consists of berseem hay and barley grains.Diets were formulated according to Kearl (1982) as the 60% of the maintenance requirements were whole barley grains while roughage portion of the diet was left free choice for animals. Diets were offered twice daily. On the other hand, diets that would be fed at later times of the experiment were formulated and representative samples were taken for incubation.
3- Buffers
The buffers used in the experiment were Bentonite, Magnesium oxide (MgO)or Potassium chloride (KCl). Different concentrations of the buffers were 0.25%, 0.5% or 0.75% of total ration dry matter.
4- Experimental protocol
Stomach tube was used to withdraw rumen liquor at 0, 2, and 4 hrs postfeeding randomly from 3 animals. Samples were, then, incubated with representative samples of feeds and the particular buffer. Each incubation tube contained 50 ml of double cheesecloth squeezed rumen liquor, 2.5 gram of either atriplex or hay and either 0.25%, 0.50% or 0.75% of thenominated buffer(bontonite, MgO, or KCl). Parameters of incubations were total dissolved salts(TDS), pH and electric conductivity (Ec). Parameter measurements were taken at 0, 15, 30 and 60 minutes after the initiation of incubation.
5-Rumen liquor preparation
Pens where animals were housed were a few meters away from the laboratory. Rumen samples were transferred quickly to the lab, double cheesecloth squeezed and CO2 was let to pass through samples before and during the incubation period at 39oC.
RESULTS
1-pH values
1.1.buffer type
Table 1. Effect of buffer type on pH, Ec, TDS, and TVFA's
Buffer type / Bentonite / MgO / KCl / ±SEpH / 6.56b / 7.44a / 6.57b / ±0.021
Ec, mmoles/cm / 6.74b / 7.11a / 6.91c / ±0.037
TDS, mg/l / 3.15c / 3.37a / 3.24b / ±0.017
TVFA's, mleqv. / 9.61b / 9.98b / 10.71a / ±0.148
The effect of buffer type on pH, Ec, TDS, and TVFA's is shown in Table (1). Magnesium oxide (MgO) raised pH value significantly (P<0.05). MgO acted as alkanizer as expected. Both bentonite and KCl had almost identical pH values (6.56 and 6.57 for bentonite and KCl, respectively), while that of MgO was 7.44.
1.2.buffer concentrations
Different buffer concentrations had a highly significant (P<0.0001) effect on pH values. Increased bentonite concentrations (Table 2) decreased ruminal pH (6.74, 6.50 and 6.42 for 0.25, 0.50 and 0.75%, respectively). On the other hand, MgO increasedpH values as its concentrations increased (7.05, 7.44 and 7.84 for 0.25, 0.50 and 0.75%, respectively). Seemingly, as potassium chloride concentrations increased, the rumen pH increased (6.44, 6.46 and 6.80 for 0.25, 0.50 and 0.75%, respectively).
1.3.type of substrate
Berseem hay or atriplex as a substrate for microbial incubation had a significant (P<0.05) effect on pH values (Table 3).Atriplex produced lower pH value than berseem hay did (6.74 and 6.97 for atriplex and bersem hay, respectively).
1.4.time of incubation
As time of incubation progressed, the pH value decreased (Table 4). There was a significant effect (P<0.05) of time of incubation on pH value (7.10, 6.82, 6.78 and 6.72 for 0, 5, 30 and 60 minutes of incubation, respectively). It is noticed that the effect of time of incubation had no significant effect after 30 minutes as there was no significance thereafter.
Table 2. Effect of buffer concentrations on pH, Ec, TDS, and TVFA's
Buffer type / Bentonite / MgO / KCl / ±SE / Sig. levelBuffer Conc. / 0.25 / 0.50 / 0.75 / 0.25 / 0.50 / 0.75 / 0.25 / 0.50 / 0.75 / P<
pH / 6.74 / 6.50 / 6.42 / 7.05 / 7.44 / 7.84 / 6.44 / 6.46 / 6.80 / ±0.037 / 0.0001
Ec, mmoles/cm / 6.95 / 6.63 / 6.65 / 7.37 / 7.02 / 6.95 / 6.95 / 6.81 / 6.98 / ±0.065 / 0.02
TDS, mg/l / 3.26 / 3.07 / 3.12 / 3.45 / 3.30 / 3.28 / 3.28 / 3.17 / 3.26 / ±0.029 / 0.348
TVFA's, mleqv. / 9.44 / 10.30 / 9.09 / 10.17 / 10.84 / 12.11 / 12.11 / 9.91 / 10.10 / ±0.257 / 0.0001
1.5.effect of interactions
Table (5) shows the effect of buffer type, substrate type interaction while table (6) shows theeffect ofsubstrate type, buffer concentration interactionon ruminal pH values. Bentonite (Table 5) with hay or atriplex did not show any significant effect on pH values (6.55 and 6.56 for hay and atriplex, respectively).Magnesium oxide showed a difference when it was used with hay than with atriplex (7.59 and 7.30 for hay and atriplex, respectively). Potassium chloride showed the same effect as did MgO did. It increased pH value of the rumen with hay than with atriplex (6.77 and 6.36 for hay and atriplex, respectively). The overall effect of this interaction was highly significant(P<0.0001).
As buffers concentrations increased with hay, the values of pH (Table 6) increased (6.89, 6.91 and 7.10 for 0.25, 0.50 and 0.75%, respectively). The same trend was true when atriplex was used (6.59, 6.69 and 6.94 for 0.025, 0.50 and 0.75%, respectively). The overall effect of this interaction was not significant.
2-Ec and TDS
2.1. Buffer type.
Magnesium oxide (MgO) showed the highest (Table 1) Ec and TDS values (7.11 mmoles/cm and 3.37 mg/l for Ec and TDS, respectively). Bentonite showed the least values of Es and TDS (6.74mmols/cm and 3.15 mg/l for Ec and TDS, respectively), while KCl showed intermediate values (6.91 mmoles/cm and 3.24 mg/l for Ec and TDS, respectively). The differences were significant (P<0.05).
Table 3. Effect of substrate type on pH, Ec, TDS, and TVFA's
Substrate / Hay / Atriplex / ±SEpH / 6.97a / 6.74b / ±0.021
Ec, mmoles/cm / 6.40b / 7.45a / ±0.031
TDS, mg/l / 2.99b / 3.51a / ±0.014
TVFA's, mleqv. / 9.66b / 10.54a / ±0.135
2.2. Buffers concentrations
Table (2) shows the effect of buffer concentration of Ec and TDS. Elevated concentrations of bentonite did not affect either Ec or TDS values significantly. Both MgO and KCl concentration did not affect the values of Ec and TDS significantly. Values of Ec and TDS under different concentrations of either bentonite, MgO or KCl were very similar.
2.3. Substrate type
Atriplex (Table 3) increased Ec value (7.45 mmoles/cm) significantly than did berseem hay (6.40 mmoles/cm). The values of TDS also increased (3.51mg/l) significantly as a result of using atriplex, while hay reduced significantly (p<0.05) lower value 2.99 mg/l.
2.4. Time of incubation
As time of incubation (Table 4) progressed, the value of Ec increased. The value of control (0 time) was significantly (p<0.05)the lowest (6.71mmoles/cm). The increment of Ec values were not significantly different (6.93, 7.02 and 7.03 mmoles/cm for 5,30 and 60 minuets respectively).
2.5. Effect of interactions
Table (5) shows the effect of buffer type, substrate type interaction on Ec and TDS. When atriplex was incubated with different buffers showed significant differences (P<0.04). Bentonite with atriplex had the lowest Ec value (7.33 mmoles/cm) while MgO showed the highest Ec value (7.57 mmoles/cm) and KCl exhibited a medium Ec value (7.44 mmoles/cm). On the other hand, the effect of different buffers with atriplex was not significant (Table 5). The same trend was observed when hay was used as a substrate with different kinds of buffers. The effect of buffers on Ec values was significant (P<0.04) while the effect of buffers on TDS was not significant.
Table 4. Effect of time of incubation on pH, Ec, TDS, and TVFA's
Time of incubation / T1(0 min) / T2
(5 min) / T3
(30 min) / T4
(60min) / ±SE
pH / 7.10a / 6.82b / 6.78bc / 6.72c / ±0.024
Ec, mmoles/cm / 6.71b / 6.93a / 7.02a / 7.03a / ±0.043
TDS, mg/l / 3.13c / 3.25b / 3.31a / 3.31a / ±0.019
TVFA's, mleqv. / 9.92a / 10.11a / 10.12a / 10.24a / ±0.171
Table (6) shows the effect of substrate type, buffer concentrations interaction on both Ec and TDS values. This effect on Ec was significant (P<0.002). The 0.50% concentration produced the least Ec value (6.19 mmoles/cm) with hay, while with atriplex it exhibited a medium value (7.45 mmoles/cm). The highest Ec value was for the 0.25% concentration (6.62 and 7.57 mmoles/cm for hay and atriplex, respectively). The same was true for the effect of substrate type, buffer concentrations interaction, yet the effect was not significant.
3-TVFA's
3.1. Effect of buffer type
Table (1) shows the effect of buffer type on TVFA's concentrations in the tubes of incubation. Potassium chloride produced the highestTVFA's (10.71 mleqv) significantly (P<0.05). Bentonite showed the least TVFA's concentration (9.61 mleqv).
3.2. Buffer concentration
The effects of different buffer concentrations on ruminal TVFA's concentrations are shown in table (2). The highest effect was highly significant (P<0.0001). The 0.50% concentration of Bentonite produced the highest TVFA's concentration (10.30 mleqv). The 0.75% concentration of MgO produced also the highest concentration of TVFA's (12.11 mleqv), while the 0.25% concentration of KCl produced the highest concentration of TVFA's (12.11 mleqv).
Table 5. Effect of buffer type, substrate type interaction on pH, Ec, TDS, and TVFA's
Buffer type / Bentonite / MgO / KCl / ±SE / Sig. levelSubstrate / Hay / Atriplex / Hay / Atriplex / Hay / Atriplex / P<
pH / 6.55 / 6.56 / 7.59 / 7.30 / 6.77 / 6.36 / ±0.0300 / 0.0001
Ec mmoles/cm / 6.15 / 7.33 / 6.56 / 7.57 / 6.39 / 7.44 / ±0.0529 / 0.0436
TDS, mg/l / 2.88 / 3.42 / 3.11 / 3.62 / 2.99 / 3.49 / ±0.0238 / 0.5993
TVFA's, mleqv. / 9.65 / 9.57 / 9.29 / 10.66 / 10.04 / 11.38 / ±0.210 / 0.0005
3.3. Effect of substrate type
Atriplex (Table 3) significantly (P<0.05) produced more TVFA's than did berseem hay (10.54 and 9.66 mleqv for atriplex and hay, respectively).
3.4. Effect of incubation time
As time of incubation time progressed (Table 4), TVFA's concentrations increased (9.92, 10.11, 10.12, and 10.24 mleqv for 0, 5, 30, and 60 minutes, respectively). The increase in TVFA's concentrations was not significant.
3.5. Effect of interactions
Table (5) shows the effect of buffer, substrate interaction. Bentonite produce similar TVFA's concentrations with hay and atriplex (9.65 and 9.57 mleqv for hay and atriplex, respectively), while MgO produced less significant (P<0.05) TVFA's with hay than did with atriplex (9.29 and 10.66 mleqv for hay and atriples, respectively). The potassium chloride (KCl) produced less significant (P<0.05) TVFA's with hay than did with atriplex (10.04 and 11.38 mleqv, for hay and atriplex, respectively).
The effect of substrate, buffer concentration is shown in table (6). As concentrations increased, the TVFA's concentrations decreased with hay (10.46, 9.50, 8.93 mleqv for .025, 0.50 and 0.75% buffer concentrations, respectively). With atriplex, the response was different. The 0.50% buffer concentration produced the highest TVFA's concentration, while the 0.75% buffer concentration produced the least TVFA's concentrations (10.69, 11.10, and 9.82 mleqv for 0.25, 0.50 and 0.75%, respectively).
Table 6. Effect of substrate type, buffer concentration interaction on pH, Ec, TDS, and TVFA's
Substrate / Hay / Atriplex / ±SE / Sig. levelBuffer Conc. / 0.25 / 0.50 / 0.75 / 0.25 / 0.50 / 0.75 / P<
pH / 6.89 / 6.91 / 7.10 / 6.59 / 6.69 / 6.94 / 0.0357 / 0.1766
Ec, mmoles/cm / 6.62 / 6.19 / 6.39 / 7.57 / 7.45 / 7.32 / 0.0534 / 0.0024
TDS, mg/l / 3.09 / 2.89 / 2.99 / 3.57 / 3.47 / 3.48 / 0.0247 / 0.0944
TVFA's, mleqv. / 10.46 / 9.59 / 8.93 / 10.69 / 11.10 / 9.82 / 0.2332 / 0.0245
DISCUSSION
Old man saltbush (Atriplex nummularia) is one of the most popular species for revegetation and rehabilitation of saline soils as it can tolerate high levels of soil salinity as well as extended periods of drought (Grice and Muir, 1988). Saltbush provides a source of feed for sheep during summer and autumn when the only other alternatives are poor quality annual grasses, cereal stubbles, or expensive feed supplements such as concentrate feed mixtures.On the other hand, saltbush has several drawbacks when fed to ruminants (Attia-Ismail, 2008). High salt contents and, hence, the presence of ions and the mineral interaction in the rumen are examples.
In ruminants, feedstuffs are fermented bymicroorganisms in the rumenprior to gastricand intestinal digestion. Ruminal fermentationproduces short-chain acids (primarily acetic,propionic, butyric, and, sometimes, lacticacids), and this acid production must be buffered to prevent adecrease in ruminal pH (Russell and Chow, 1993).
Relationships between in vitro fermentation kinetic parameters, chemical composition and stageof maturity were evaluated in five halophyte shrubs collected from arid salty areas in south eastAlgeria. All shrubs had lower in vitro fermentation characteristics than Medicago sativaused as standard hay (Haddi et al, 2003). The inclusion of buffers might, then, help and that is why the present study was conducted.
Saltbush diet caused an increase in rumen pH because animals fed saltbush diet hadinefficient rumen fermentation explained by high salt content of the diet (Mayberry, 2008).The reduction in volatile fatty acids may explain the rise in rumen pH.
The inclusion of Bentonite in the pellets reduced the total concentration of volatile fatty acids in the rumen (Aitchoson et al, 1986).Bentonite in the present study also reduced the total concentration of volatile fatty acids in the incubation tubes. The reduction of TVFA's as a result of adding bentonite might be due the natural characteristics of bentonite as it can swell in the rumen, shifts rates of passage, and adsorbs minerals and ammonia. It does not have buffering capacity. It did not change the pH or the TVFA's concentrations. Esdale and Satter, (1972) found that the effect of bentonite on ruminal acid concentration is not mediated through the influence of pH. Ivan et al, (2001) concluded that supplementation of Palm Kernel Cake based diets with 2% bentonite had no appreciable effect on rumen fermentation, duodenal flow of AA or digestibility in sheep. Bentonite did not change the pH values as a result of non-changed TVFA's in the tubes of incubationof both hay and atriplex.