Pertanika 7(3),89-94 (1984)

The Effect of Protein (as Fish Meal) on Rumen VFA Patternsof Molasses-fed Sheep

NORHANIABDULLAH*Department of Biochemistry and Nutrition,University of New England, Armidale 2351

Key words: Molasses; fish meal supplementation; VFA pattern.

RINGKASAN

Percubaan-percubaan in vivo terhadap Kambing Merino yang diberi molasses telah dilakukan untukmelihat kesan meal ikan ke atas pengambilan molasses dan corak fermentasi asid lemak meruap (VFA)dalam rumen. Meal ikan diberi semasa rawatan yang berbalik. Perbezaan dalam pengambilan molassesdisebabkan oleh protein dilihat dalam masa rawatan dan analisis regresi ke atas bahagian-bahagian VFAmelawani molasses di masa rawatan menunjukkan bahawa tahap pengambilan adalah satu fak tor pengaturdalam corak V.FA yang terhasil. Propionat dan butirat didapati berkorelasi positif, manakala asetat ber­korelasi negatzj dengan pengambilan molasses. Kesan pengambilan dan nisbah tenagajprotein ke atas corakVFA juga dibincangkan.

SUMMARY

Experiments in vivo with molasses fed Merino sheep were carried out on a treatment reversal patternexamining the effects of fish meal (FM) supplementation on molasses intake and rumen volatile fatty acid(VFA) fermentation pattern. Differences in molasses intake due to protein supplementation were obsen'edin the different periods. Regression analysis of VFA proportions against molasses intake during treatmentperiods indicated that the level of intake was a controlling factor in the patterns of VFA produced.Propionate and butyra'te were found to be positively, while acetate was negatively correlated with themolasses intake. The effects of intake and energyjproterin ratio on VFA pattern are also discussed.

INTRODUCTION

Rumen bacteria obtain their N for biosyn­thesis not only from NH

3(Allison, 1969) but

from amino acids and peptides (Pittmann andBryant, 1964). With unconventional diets, suchas those based on molasses (Preston et al., 1967)or sugar cane (Leng and Preston, 1976) the proteincontent of the basic energy component is lowand N is supplied as urea and supplementaryprotein. This supplementary protein may undergodigestion In the rumen and simply contribute tothe NH pool or it may be used directly by the

. 3 h' fmIcro-flora for growt or It may escape ermenta-tion and undergo partial or total digestion inthe abomasum and small intestine.

One of the common protein supplementswhich has been used with high sugar diets hasbeen fish meal because of its low solubility and

low rate of rumen degradation (Whitelaw andPreston, 1963). However the presence of someamino acids and peptides may affect microbialactivity and can be detected in the patterns ofVFA pr:oduced.

This paper describes the effects of additionor removal of fish meal on the daily ruminalfermentation pattern of molasses oaten chafffed sheep.

MATERIALS AND METHODS

Three fistulated Merino wethers (about 30to 40 kg) were kept in single pens with woodenslatted floors. They were adapted to either diet1 (100 g oaten chaff fed once daily and molasses­urea fed ad libitum) or diet 2 (100 g oaten chaffwith 60 g fish meal fed once daily and molasses­urea fed ad libitum) for about 10 weeks. The

*Present address: Department of Biochemistry and Microbiology, Faculty of Science and Environmental Studies, UniversitiPertanian Malaysia.

89

NORHANI ABDULLAH

animals had free access to drinking water. Molassescontained 3% urea and 0.135% mineral mix.

During the period of study, the sheep weregiven the solid ration at 8 a.m. and about 20 mlsor rumen liquor were withdrawn at 11 a.m.Each experiment lasted for about five weeks.The sheep were initially sampled for about a weekon the adapted diet, then 60 g of fish meal waseither given or withdrawn depending on theorder of diet each one followed. Daily samplingwas carried on for the next two weeks on thisration, after which the previous ration (with orwithout supplementation of fish meal) was startedagain and the sheep sampled for another twoweeks.

Molasses intake was monitored by differencesin the weight of containers. However, some lossesfrom dribbling were unavoidable. The rumensamples were examined immediately for pHand then acidified. Volatile fatty acids wereanalysed by the method of Geissler et al., (1976)and NHg-N by steam distillation and titration.

RESULTS

pH

pH values of samples stayed within the rangeof pH 6.4 to 7.8.

Effect of Fish Metal on VFA Pattern and Nhg-N

The result of VFA patterns for each sheepwas considered separately as there were differencesin the proportions of acetic (C2.), propionic (C g)and butyric (C4) acids. Table 1 shows the mean(± S.E.) molar proportions, of each held duringthe periods of with and without protein supple­mentation.

The results of Students's t-test applied to thedifferences in the means during the two treat­ment priods failed to show significant differencesin fatty acid patterns attributable to the fish mealtreatment.

Table 2 shows the mean (± S.E.) of NH -Nconcentrations (mg 100 mr!) of rumen samp1es.The mean values of NH

3-N of the three periods

for each sheep were not sIgnificantly different.

Effect of Molasses Intake on VFA Pattern During.Periods with and without Protein Supplementa­tion.

Table 3 shows the mean (± S.E.) molarpercentage values of Cz ' Cg and C4 acids, and the

90

mean (± S.E.) molasses intake for the three sheeprespectively. When the molar % of each acid wasregressed against molasses intake at differentperiods (+ fish meal and - fish meal), the majorityof the relationships were not significant. However,there were indications of some significant correla­tions between the molar % of acetate, propionateand butyrate with molasses intake. Acetate wasnegatively correlated to molasses intake in oneunsupplemented period (sheep 1) and duringone supplemented period (sheep 2). Propionatewas positively correlated to molasses intake intwo supplemented periods (sheep 2 and 3) whilebutyrate showed a positive correlation withmolasses intake in one supplemented period(sheep 1) and one unsupplemented period (sheep3).

Effect of Fish Meal on Molasses Intake

Table 3 also shows the mean (± S.E.) ofmolasses intake for the different periods. Sheep1 and 3 clearly showed differences in in~ke ofmolasses due to treatment. In the presence offish meal, the amount of molasses consumedwas significantly higher for sheep 1 (p<O.OO 1)and sheep 3 (p < 0.05).

DISCUSSION

The pH values of rumen samples for thesesheep are fairly high. Rumen pH of 6.4 has beenobserved in Holstein bulls fed high molassesby Reyes (1973).

The high rumen pH in molasses fed sheepis in contrast to the low pH observed when solublecarbohydrates are fermented (Eadie et al., 1970).The high pH could be due to the way the animalconsumed the molasses, that is, in small quantitiesthroughout the day.

NHg-H content of rumen liquor are slightlyhigher in the periods of fish meal supplementation.This could be partly due to urea as the levels ofmolasses-urea intake increased during this period.

For sheep 1 where the molasses intake washighest and consequently there was a low ratioof fish meal to molasses, the fermentation waspredominantly high in butyrate in both theearly periods but re-inclusion of fish meat led toa propionate rich pattern. At this period, molassesintake was significantly (P < 0.001) lower thanthe first period.

For sheep 2, with a much lower molassesintake and consequently a high protein molasses

Mean (± S.E.) molar Mean (± S.E.) molarAcid Sheep % % t-test

± fish meal - fish meal...

Acetic 1 44.4 ± 3.5 (31)* 41.7 ± 2.9 (14)

2 54.3 t 5.6 (14) 58.1 t 3.5 (19) NS

3 57.7 ± 2.1 (20) 54.0 ± 1.9 (14)

Propionic 1 24.0 ± 6.2 (31) 24.3 ± 3.4 (14)

2 31.1 ± 4.6 (14) 24.8 ± 4.1 (19) NS

3 33.4 ± 3.1 (20) 37.4 ± 2.5 (14)

Butyric 1 29.3 ± 7.1 (31) 30.5 ± 5.6 (14)

2 12.8 ± 2.4 (14) 15.0 ± 2.9 (19) NS

3 6.7 ± 1.8 (20) 6.8 ± 1.2 (14)

t..O.......

NS

*

TABLE 1The mean (± S.E.) molar proportions of acetic, propionic and butyric acids during theperiods of with and without protein supplementaion, and the result of Student's t-test

applied to the differences in the means.

Not significant

Number of samples

...,::c:t'Tj

tTl"I'j"I'jtTl

~o"I'j

"'0:;tIo@Z'>en"I'j

en::c:~tTl;I>

Soz:;tIc::~tTlZ<"I'j;I>-

~

;J>""'l...,tTl:;tIZeno"I'j

~o~enentTlen~tTlt:1en::c:tTltTl"'0

t.D~

TABLE 2Means (± S.E.) of NH

3-N concentrations (mg 100 ml- 1 ) for the three treatment periods of

Sheep 1,2 and 3. The results of analysis of variance on the daily samples are shown.

Analysismg NH

3---N 100 ml- 1 for treatment period of

Sheep variance+ fish meal - fish meal -f fish meal -- fish meal

1 14.4 -t 3.2 (8) * 13.9 ± 2.8 ( 1.+) 14.0 t 1.6 (21 ) NS between

periods

2 9.8 ± 3.5 (5 ) 16.3 ± 1.2 (14) 12.2 ± 1.3 (14) NS between

periods

3 18.8 ± 4.5 (7) 1.'i.2 ± 2.0 (14) 18.1 ± 1.7 (14) NS between

periods

zo:;0::c;J>

~;J>t:OoCl'r;l>::c

NS

*

Not significant

Number of samples

THE EFFECT OF PROTEIN (AS FISH MEAL) ON RUMEN VFA PATTERNS OF MOLASSES-FED SHEEP

TABLE 3The mean (± S.L) molar proportions of acetic (C

2), propionic (C

3) and butyric (C

4)

acids of samples, the man (± S.L) molasses intake and the relationship betweenmolar percentages and the molasses intake for Sheep 1: 2 and 3.

Sheep Period

No.ofobser­vations

Acid

Molar %(mean ± S.E.)

g Molassesintake day-1(mean + S.L)

Correlation between molar% and molasses intake

1.

2.

+ fish meal 10

10

10

- fish meal 14

14

14

+ fish meal 21

21

21

- fish meal 5

5

5

+ fish meal 14

14

14

- fish meal 14

14

14

C

C

43.4

19.7

34.6

41.7

24.9

30.8

45.0

25.8

26.7

59.9

24.5

14.3

54.0

31.2

12.8

57.9

24.7

15.3

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

±

1.3

0.7

1.1

0.8

1.1

1.3

0.8

1.3

1.5

2.1

1.3

1.4

1.5

1.2

0.6

0.9

1.3

0.8

1444

1182

1105

460

484

474

±

±

±

±

±

±

34

NS

Positive correlation(r2

= 0.47, P < 0.05)

S

N~gative correlation(r 0.35, P <,0.05)

NS

Positive correlation(r2 = 0.38, P < 0.05)

NS

NS

NS

NS

NS

NS

Negative correlation(r2 = 0.41, l' < 0.05)

Positive correlation(r2 = 0.44, P < 0.05)

NS

NS

NS

3. + fish meal 6

6

6

57.8

36.0

4.8

±

±

±

0.5

1.2

0.3

713 ± NS

NS

NS

- fish meal 14

14

14

54.0

37.4

6.8

±

±

±

0.5

0.7

0.3

696 ± NS

NS

NS

+ fish meal 14

14

14

57.7

32.2

7.7

±

±

±

0.7

0.7

0.4

811 ±. 34" NS

NS

Positive correlation(r2 = 0.34, P < '0.05)

ab means without letter in common differ at P < 0.001

abc demeans without letter in common differ at P < 0.05

NS - Not significant

93

NORHANIABDULLAH

ratio, the fermentations were proprionate richcompared to butyrate (with a higher percentagein the supplemented period).

REFERENCES

For sheep 3, where molasses intake was abouthalf way between the intake of sheep 1 and 2, thefermentation pattern was propionate predominantover butyrate.

It is interesting to note that the two periodsin which propionate proportion rose significantlywith molasses intake are both in protein supple­mented periods. Sutherland (1977) suggestedthat the appropriate conditions for propionatebeing the preferred hydrogen acceptor would beunder good conditions of microbial nutrition.

The two factors of molasses intake andprotein to molasses ratio obviously do not coverall the variation in the VF A patterns observed.Animal factors are important. Sheep 1 and 3,although consuming a high amount of molassesand following similar feeding conditions, differedmarkedly in the predominant VF A patterns andobviously a great deal remains to be discoveredon the factors controlling such patterns.

There are many reports in literature whereaddition of protein has led to increasing voluntaryintake, particularly in the case of low qualityroughage (Weston, 1967). The same applies withmolasses where daily molasses intake increasedwi th increased proportions of dietary nitrogen(as fish meal) in fattening bulls (Preston, 1972).The greater part of fish meal could be expectedto escape rumen degradation due to its relativeinsolubility, which implies that the amount ofamino acids entering the sites of metabolism playa determinant role in intake control.

CONCLUSION

Molasses intake and protein energy substrateratios seem to be important controlling factors forthe pattern of volatile fatty acids produced insheep fed molasses urea.

ACKNOWLEDGEMENTS

The author wishes to thank Dr. T.M. Suther­land for guidance and advice on the work carriedout; Universiti Pertanian Malaysia for the studyleave; and the Australian Government for thescholarship.

94

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(Received 12 March, 1984)