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Molar proportions of volatile fatty acids in the gastrointestinal tract of East African wild ruminants
romp. Biochmz. Phwio!. Printed in Great B;italn
Vol. 76A, No. 2. pp. 217-224,
1983
0300-Y629/83 $3.00 + 0.00 (‘8 1983 Pergamon Press Ltd
MOLAR PROPORTIONS OF VOLATILE FATTY ACIDS IN THE GASTROINTESTINAL TRACT OF EAST AFRICAN WILD RUMINANTS E. T. CLEMENS, G. M. 0. MALOIY and J. D. SUTTON* Department of Veterinary Science, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 685X3-0905. U.S.A. Telephone: (402) 472-2952 and Department
of Veterinary
Physiology.
University
of Nairobi,
Nairobi,
Kenya,
East Africa
AbstractI. The molar proportions of seven individual VFA’s were determined at select sites along the gastrointestinal tract of sixteen species of East African wild ruminants. 2. The resulting data were statistically analyzed for species effect. and for effects due to major feeding groups (browsers, grazers. fresh grass grazers, etc.) and for body weight groups (5-750 kg animals). 3. Present data suggest that body weight, rather than diet, is the more influential factor in reticula-rumen fermentation rate, and in the molar proportion of fatty acids present. 4. The molar proportions of VFA’s observed in the mid and hindgut of these wild ruminants appeared more responsive to diet and body weight of the animal than did foregut VFA values.
INTRODUCTION
East African wild ruminants were used in the study. These included: Five Kirk’s dik-dik (Mudoqua kirki), two suni (Nesotrqu.c moscharus ). three giraffe (Giraffe came/opardrr/i.s), one gerenuk (Litocrunius walleri), two eland (Tuurotrugus orys). four Grant’s gazelle (GazrNu granti). two steenbok (Ruphicerus crtmpesfris), four impala (A.y~ceros melrtmpus), four Thomson’s gazelle (Guzeilu tkornsoni),two buffalo (Buhaluh c@er), two waterbuck (Kohus ellipsipr~mntrs). three wildebeest (Connochuetes /rcurinus). one hartebeest (Alccphalus huselaphus). three topi (Danzaliscus km&is). three mountain reedbuck (Redunca fitlcorufitlu), and four oryx (Oryx ga-_e/la). All animals were collected from their natural habitat in conjunction with wildlife management programs. Field analysis and sample collection were begun immediately after death and generally completed within one hour. Details of the field procedures were reported earlier (Clemens and Maloiy, 1983). Representative samples of gastrointestinal contents were collected from select segments of tract (the reticula-rumen, abomasum, small intestine. caecum, proximal colon. and distal colon). These samples were strained through cheese cloth, the supernatant acidified with concentrated HISO, (approx 0.5 ml per 20 ml sample) and the resulting fluids refrigerated for later analysis by gas chromatography). Data were subject to analysis of variance and regression analysis (Steel and Torrie, 1960). Comparisons were made for variance between species, weight of the animal and the major and sub-feeding groups. as reported by Hofman (1973).
Concentrations of short chain organic acids and their molar proportions, have been used as an index for a variety of aspects of ruminant nutrition and physiology. Such components may describe fermentation rates (Hungate rt al.. 1959; Lang and Brett, 1966), diet characteristics (Short et al., 1966; Hoppe et al., 1977a). energy source and available substrate (Bauman ct a/., 1971; Hoppe et d., 1977b; Sutton, 1980), osmotic regulation (Kreulen and Hoppe, 1979; Maloiy and Clemens, 1980), fluid and electrolyte transport mechanics (Dobson, 1959; Stevens, 1973), and a variety of lesser physiological functions. Most studies have been conducted on domestic livestock and, more specifically, within the ruminant forestomach (i.e. the reticula-rumen areas). While the reliability of such index components is in question (Hungate rt ml., 1961; Kay rt cd., 1980) investigators continue to pursue these numerous goals. Such is the case in the present investigation. Opportunity provided for an intensive study of the molar proportions of volatile fatty acids within the tract of sixteen species of East African wild ruminants, collected from their natural habitat. The study was expanded beyond the ruminant forestomach to include six major segments of gastrointestinal tract, from the reticula-rumen to the distal colon. Comparisons were made of gut segments. species, major feeding groups (browsers, grazers, intermediate feeders) and sub feeding groups (dry region grazers, roughage eaters, fresh grass grazers, etc.), and seven weight groups from the 5 kg dik-dik, and suni to the 750-plus kg giraffe, eland and buffalo.
RESULTS The series of Tables I4 present the analytical data for seven individual volatile fatty acids (VFA) recovered from the gastrointestinal contents of wild ruminants. The tables are further divided into mean and standard error values for species, major and subfeeding groups, and seven weight groups. With few exceptions. acetic and propionic acids comprised 8690”;;; of the molar concentration of VFA’s present at each site along the tract. However, butyric acid proportions in browsers were significantly higher within the caecum and colon, relative to the foregut
MATERIALS AND METHODS Forty-five
adult
male animals
*Address: National Shinfield. Reading.
Institute U.K.
representing for
Research
I6 species of Dairying.
217
E. T. CLEMENS el al.
218 Table I A. Food selection
and mean ( + SEM) molar percent of acetate in the total volatile fatty acids as observed sites along the gastrointestinal tract of sixteen species of wild ruminants Reticulorumen
Species: Food selection BROWSERS Kirk’s Dik-Dik: Fruit and dicotyledon Suni: Fruit and dicotyledon Giraffe: Trees and shrub Gerenuk: Trees and shrub
Abomasum _ ~~_ ~
GRAZERS African Buffalo: Fresh grass Waterbuck: Fresh grass Wildebeest: Fresh grass Hartebeest: Roughage Topi: Roughage Mountain Reedbuck: Roughage Oryx: Dry region
Proximal colon
Distal colon
84.4
54.2
47.2
52.4
(1.1) 13.4
(1.8) 53.6 (6.7) 70.8 (2.5) 85.2
(4.2) 65.5 (3.3) 71.2
(4.4) 61.9
(0.6) 80.2 (5.1) 92.0
(2.4) 64.4 (0.8) 70.4 (4.9) 82.7
70.0 (4.6) 12.4 (2.0) 65.6 (1.3) 64.3 (4.9) 71.5 (1.9)
71.3 (0.7) 6X.8 (2.5) 54. I (5.3) 12.5 (1.7) 66.0 (2.6)
73.8 (0.1) 74.4 (4.9) 80.6 (4.0) 66.9 (5.1) x0. I (2.9)
68.7 (4.3) 64.5 (4.6) 69.8 (6.0) 70.8 (1.1) 67.8 (2.1)
65.6 (5.3) 65.6 (1.3) 69.5 (6.7) 69.0 (2.7) 74.0 (1.6)
66.7
60.2 (8.6) 62.0 (0.2) 70.0 (0.8) 65.6
65.4 (9.8) 17.1 (X.3) 75.4 (2.0) 77.7
78.3 (0.8) 14.1 (2.9) 81.0 (2.8) x2.4
78. I (0.X) 71.6
73.8
73.4
13.6 (4.2) 74.9 (0.7) 71.7
(2.0) 70.8
(2.0) 65.8
(1.8) 64.4
69.1 (0.7) 70.4 (0.6) 72.9 (1.2)
72.1 (4.4) 72.1 (1.6) 19.1 (2.4)
77.2 (0.9) 7X.6 (3.8) 77.9 (3.2)
12.7 (1.0) 75.0 (1.9) 73.5 (3.2)
69.9 (2.6) 67.9 (1.7) 70.8 (2.4)
68.7
65.1
INTERMEDIATE Eland: Prefers browse Grant’s Gazelle: Prefers browse Steenbok: Prefers browse Impala: Prefers graze Thomson’s Gazelle: Prefers graze
Section of tract Small intestine Caecum ~~ ~~~ -~ -~ ~
at various
(2.0) 63.8 (2.4) 13.2 (1.6) 69.2
69.6 (2.5) 72.6 (7.8) 72.1
(1.4)
(0.9) 15.3
(6.0) 67.9 (2.3) 68.0 (5.4) 70.5 (1.9) 65.0 (2.5)
(2.2) 69.1 (2.0) 71.5
(5.6) 61.9 (1.7) 70.8 (2.4)
I B. Mean (+ SEM) molar percent of acetate in the total volatile fatty acids as observed at various sites along the
Table
gastrointestinal
Food
selection
MAJOR GROUPS* Brovvsers Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers) *Values within a column
tract
of the major
Reticulorumen
and sub-feeding
Abomasum
groups
Section Small intestine
of wild ruminants
of tract Caecum
Proximal colon
Distal colon
67.1 (1.5) 69.1 (1.5) 68.3 (1.3)
70.l“h (2.0) 67.4h (2.1) 74.5” (1.7)
81.9” (2.1) 75.0h (2.2) 78.3”h (1.1)
63.1” (3.3) 68.0 (1.4) 73.8” (0.7)
58.2,’ (4.3) 69.3h (1.4) 71.8” (0.9)
62.(>’ (3.4) 67.6h (1.3) 69.9h (1.1)
65.1 (1.5) 72.2 (1.5) 70. I (1.6) 68.3 (2.6) 64.9 (2.6) 69. I (0.7) 12.9 (1.2)
70.5 (2.5) 69.6 (4.0) 65.7 (4.0) 68.9 (1.9) 73.2 (3.5) 72.9 (1.9) 79.7 (2.4)
81.2 (2.2) 83.2 (4.6) 75.8 (2.6) 74.2 (3.5) 78.4 (1.6) 78.5 (1.6) 17.9 (3.3)
57. I (2.5) 73.4 (4.6) 66.8 (2.7) 69.1 (1.3) 74.2 (1.3) 73.4 (1.0) 73.5 (1.9)
49.0 (2.2) 74.4 (4.0) 66.6 (1.8) 71.7 (1.7) 73.2 (1.3) 70.6 (1.7) 71.5
56.2 (3.8) 12.2 (1.2) 67.6 (1.9) 67.5 (1.X) 71.6 (1.1) 67.X (2.3) 70.8 (2.4)
with unlike superscripts
are different
at the 0.05 level of significance
(I .O)
VFA’s in East African wild ruminants
219
Table IC. Mean (rtrSEM) molar percent of acetate in the total volatile fatty acids as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants
Weight group Less than 20 kg 20-50 kg 51-100 kg 101-150 kg 151-200 kg 20 l-300 kg More than 300 kg
Reticulorumen Abomasum _ -- _____._..-_~__._ 65.2 66.8 (1.2) (4.0) 70.8 67.5 (1.1) 11.9) 68.3 70.6 (2.9) (1.6) 69. I 72. I (0.7) (4.4) 71.5 79.2 (1.9) (1.7) 66.8 j6.4’ (2.0) (2.9) 68.5 70.0 (3.1) (2.9)
Section of tract Small intestine Caecum 81.1 (1.8)
59.9*
80.9
71.8
(2.3)
(2.2) 67.h
70.6 (3.6) 77.2 (0.9) 78.8 (2.6) 78.5 (2.3) 77.8 (2.2)
Proximal colon
(2.8)
(2.5) 72.7
(1.w 72.9 (i.6) 72.7 (1.3) 72.1 (2.6)
53.61_ (3.6) 74.9 11.7) 67.1 (1.5) 69.9 (2.6) 70.4 (I.41 73.0 (1.4) 70. I (2.2)
Distal colon 58X
(3.5j 67.2 (1.8) 69.2 (1.5) 68.7 (5.6) 69.5 (2.2) 70.x (1.2) 70.6 (1.8)
*Regression analysis (P cc 0.02) Y = 63.3 -I- 1.6X. t(P<0.006), Y =61.1 i 1.8X. $(P c O.OOl), Y = 61.4 + 1.6.X’. and midgut. These levels were also 7--9?; above the butyric acid levels at similar sites in the intermediate feeders and grazers. Acetate levels demonstrated the greatest variability among species, and among the various segments of tract (Table IA). Mean reticula-rumen acetate levels ranged from 60°d in the buffalo to 73:; in the giraffe and oryx. The percent acetate reached highest proportions within the small intestinal contents of all species except the impala and waterbuck. Analysis of acetate and the major feeding groups showed significant differences within the caecum and colonic regions. At each of the three sites, browsers had lower acetate values; grazers had the highest (Table IS). However, within the group of browsers, those animals selecting leaves of trees and shrubs (i.e. the giraffe and gerenuk) had significantly greater acetate levels within the large bowel than did fruit and di~otyledon selectors (the dik-dik and suni). The molar percent acetate within the large bowel was also related to the weight of the animal (Table IC), with heavier animals having higher values. Propionic acid levels were related to the diet and body weight of the animal (Tables 2B, C). However, the effects were signi~cant only within the reticulorumen and/or caecum of these animals. Propionate levels significantly decreased in both the reticulorumen and caecum as body weight increased (Table ?C). Furthermore such values were noted to decrease within the reticula-rumen from browsers, through intermediate feeders, to grazers. The reticula-rumen percent propionate for individual species ranged from a high of 23”;,’ in the 5 kg dik-dik to a low of 13% in the 750-plus kg eland. When the acetate to propionate ratio was considered (Tables 3A-C), significant regressions were observed only for the effect of body weight, and only within the reticula-rumen and caecum. This ratio was observed to increase with the weight of the animal (Table 3C). A near significant probability (P < 0.045) was obtained for the regression of reticula-rumen acetate:propionate ratio and the major feeding groups (Table 3B).
It shoutd be noted that the analysis of three items-body weight. major feeding group. and subfeeding group-on lactic acid concentrations was significant at alf sites in which acetate levels were significant (caecum, proximal. and distal colon) (Clemens and Maloiy, 1983). Five lesser short chain volatile fatty acids-butyric, isobutyric, Valerie, isovaleric and caprojc acids-were measured. The relationship of butyric acid levels and diet was noted earlier in Table 4. The higher levels of other short chain fatty acids (notably isobutyric and isovaleric acids) at select sites along the tract of several species. is worthy of mention. DlSCUSSlON It is generally agreed that the concentration of volatile fatty acids within the reticula-rumen is not a reliable index of their production rate (Hungate L’Ial., 1961; Kay et al., 1980). Several factors may account for this. Most importantly, reticula-rumen VFA concentrations are the combined result of production, dilution, absorption, utilization, and passage to the lower tract (Hodgson and Thomas, 1975). Obviously, when production exceeds removal absorption-utilization-passage), ’ retrculo-rurZ VFA concentrations increase. This is generally the case shortly after feeding (Kreulen and Hoppe. 1979). Consequently, infrequent feeding may introduce considerable diurnal variations (Sutton, 1980). Furthermore, these diurnal variations become more prevalent with concentrate feeding, relative to roughage diets (Hungatc et ~1.. 1961). Similarly, the molar proportion of VFA’s within reticufo-rumen contents is not a reliable index of fermentation (Bath and Rook, 1963) nor can it be construed as an index of the available substrate (Hodgson and Thomas, 1973). The results of the present study confirm the substantial variations in molar proportions of fatty acids between animals fed similar diets. Furthermore, earlier studies have shown considerable variations within the same animal and diet at different sampling times (Ishaque et al.. 1971).
220
E. T.
CLEMENS
ef ul.
Table 2A. Live weight and mean (+ SEM) molar percent of propionate m the total volatile fatty acids as observed sites along the gastrointestinal tract of sixteen species of wild ruminants Species: Live weight Kirk’s Dik-Dik: S-6 kg Suni: 557 kg Giralk: 500-750 kg
Gerenuk: 40--S I kg Eland: 400-650 kg Grant’s Gazelle: 4664 kg Steenbok: XXI I kg Impala: 53371 kg Thomson’s Garclle: 22225 kg African Buffalo: 600-X50 kg Waterbuck: 192-286 kg Wildebeest: 171-242 kg Hartcbeest: 116.-I60 kg Topi: Ill-l47kg Mountain Reedbuck: 23-28 kg Oryx: 168-209 kg
Reticulorumen
Abomasum
Section Small intestine
of tract Caecum
Proximal colon
Distal colon
22.x (I .2) 22.2 (3.1) 14.1 (0.5) IX.8
Il.3 (0.X) 15.0 (5.1) 15.4 (2.1) 9.9
13.7 (1.0) 12.2 (5.2) 10.2 (1.6) 6.3
18.9 (1.2) 13.2 (2.6) I I.0 (1.3) X.6
22.1 (2.5) 21.2 (2.5) 14.4 (3.1) 6.6
74.3 (1.5) 13.5 (2.2) 16.4 (0.5) 10.3
12.8 (2.3) 16.9 (2.3) 22.3 (I.?) 16.6 (1.7) 19.5 (2.4) 20.5 (1.3) 19.6 (0.X) 15.8 (1.2) 16.1
16.3 (0.5) 14.2 (2.4) 22.5 (4.2) 16.9 (1.4) IX.1 (3.6) 24.6 (4.2) Il.7 (2.5) 14.3 (1.4) I I.2
10.0 (0.9) 14.3 (2.3) I I.6 (0.0) 15.1
14.7
17.4 (0.2) 15.7 (2.X) 16.6
16.1 (0.6) 16.1 (0.5) 14.2 (0.4)
15.2 (3.3) 18.4 (2.3) Il.4 (2.2)
(1.X) 15.6 (4.2) 12.8 (2.2) 12.0 (3.8) 12.0 (0.9) 14.X
16.6 (1.1) 17.0 (4.4) IX.1 (1.1) 19.4 (2.1) 13.8 (0.6) 15.2 (1.6) 14.1 (0.9) 16.5
14.4 (2.0) 13.2 (2.5) 15.8 (2.6) 15.0 (0.5) 15.7 (1.2) 21.5
17.4 (2.4) 15.7 (2.8) 16.X (I .8) 17.0 (2.2) 15.9 (2.X) 13.x (2.8) 16.4 (0.2) 14.3 (1.5) 20.9
8.3 (0.2) 9.9 (2.2) 12.8 (0.9)
17.1 (0.4) 14.5 (0.6) 16.0 (1.0)
19.3 (2.0) 13.9 (2.1) 13.4 (0.X)
IX.2 (3.3) 17.6 (1.3) II.6 (1.9)
c1.4)
(1.w
Table 2B. Mean (k SEM) molar percent of propionate in the total volatile fatty acids as observed at various the gastrointestinal tract of the major and sub-feeding groups of wild ruminants
Food MAJOR Browsers
selection
at various
Section Small Intestine
Reticulorumen
Abomasum
19.9” (1.4) 17.7”h (1.1) 16.5’ (0.6)
12.9” (1.1) 17.2” (1.3) 15.2”” (1.3)
(1.1) 14.1 (1.4) II.6 (0.8)
22.6 (1.1) 15.2 (1.2) 17.2 (1.7) IX.2 (1.5) IX.2 (1.0) 16.1 (0.3) 14.2 (0.4)
12.3 (1.4) 14.0 (2.0) 16.8 (1.8) 17.6 (2.0) 16.6 (2.4) 16.0 (1.8) Il.4 (2.2)
13.2 (1.4) 9.2 (1.5) 12.5 (1.3) 15.3 (2.4) 12.6 (1.3) 9.9 ( I .4) 12.8 (0.9)
sites along
of tract Proximal colon
Distal colon
14.8” (1.4) 17.6” (0.9) 15.3” (0.4)
IX.7 (2.1) 14.8 (1.0) 15.8 (0.8)
16.6 (1.2) 16.4 (1.4) 15.4 (1.0)
17.3 (1.5) 10.4 (1.0) 16.2 (1.1) IX.8 (I.?) 14.3 (0.3) 15.9 (0.6) 16.0 (1.0)
22.2 (1.X) 12.5 (2.9) 16.0 (1.3) 13.8 (1.6) 15.5 (0.7) 17.3 (1.6) 13.4 (0.X)
17.6 (1.6) 14.8 (1.6) 16.4 (1.4) 16.4 (2.3) 14.8 (0.9) IX.3 (1.4) I I.6 (1.9)
Caecum
GROUPS*
Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers) *Values within a column
with unlike superscripts
are different
Il.8
at the 0.05 level of significance.
VFA’s in East African wild ruminants
221
Table 2C. Mean (+ SEM) molar percent of propionate in the total volatile fatty acids as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants
Weight group Less than 20 kg 20-50 kg 51-100 kg 101-150 kg 151-200 kg 20 l-300 kg More than 300 kg
Reticulorumen 22.6* (0.8) 18.3 (1.4) 16.7 (1.3) 16.1 (0.1) 14.6 (0.5) 17.3 (1.2) 15.5 (1.4)
Abomasum ~14.6 (1.9) 17.3 (2.2) 15.5 (1.4) 15.2 (3.3) Il.4 (1.7) 13.3 (1.2) 18.3 (2.0)
Section of tract Small intestine Caecum 12.9 (1.1) 12.7 (2.6) 14.7 ( i .4) 8.3 (2.0) 13.1 (0.8) 12.5 (1.3) 10.9 (1.3)
17.2t
(1.3) 16.6 (1.7) 17.4 (0.8) 17.1 (0.4) 16.1 (0.8) 14.5 (0.8) 12.9 (0.9)
Proximal colon
Distal colon
21.0 (1.7) 12.7 (1.6) 14.7 (1.4) 19.3 (2.0) 15.0 (1.7) 15.4 (0.7) 15.6 (1.4)
17.4 (1.2) 15.8
@?I 16.4 (1.6) 18.2 (3.3) 13.5 (2.4) 15.2 (1.0) 15.9 (1.0)
*Regression analysis (P < 0.003). Y = 21.2--0.9X. i(f’ < 0.006). Y = 18.3-0.6X.
While the same or similar diets may provide variations in molar proportions of acids, the question of different diets, available substrate, and the molar proportions of VFA’s needs to be considered. It can be noted that, in spite of the diversity of diets consumed by these wild ruminants, the molar proportion of VFA’s appears to be unrelated to diet, and thus to the available substrate. While reticuio-rumen propionate levels were higher in browsers and less in
grazers, neither the acetate, butyrate or acetate:propionate ratios showed an association with diet effect. From the critical evaluation of the present set of data, it appears that body weight is the more influential factor in both the reticula-rumen fermentation rate and the molar proportions of fatty acids present. Molar proportions of propionic acid are consistently higher, the acetate:propionate ratio
Table 3A. Mean (+ SEM) acetate to propionate ratio as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants
Snckes
Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle Steenbok
Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi Mountain Reedbuck oryx
Reticuiorumen 2.92 (0.23) 2.94 (0.52) 5.21 (0.13) 3.68 5.71 (1.38) 4.65 (0.89) 2.96 (0.22) 3.94 (0.34) 3.92 (0.49) 2.97 (0.60) 3.18 (0.13) 4.48 (0.37) 4.07 4.31 (0.20) 4.38 (0.15) 5.13 (0.1 I)
Abomasum 6.28 (0.44) 5.67 (2.45) 4.92 (0.84) 6.25 4.38 (0.18) 5.26 (0.82) 2.62 (1.67) 4.38 (0.40) 4.27 (0.84) 2.81 (0.87) 7.12 (2.23) 5.30 (0.48) 6.97 5.33 (1.36) 4.08 (0.66) 8.45 (2.53)
Section of tract Small intestine Caecum 6.32 (0.55) 7.33 (3.05) 8.42 (1.88) 14.60 7.44 (0.68) 5.73 (1.17) 6.94 (0.34) 4.58 (0.58) 7.91 (2.88) 6.90 (2.33) 6.95 (2.40) 6.36 (0.56) 5.57 10.33 (2.15) 8.52 (1.41) 6.27 (0.80)
2.91 (3.66) 5.07 (0.94) 4.44 (0.32) 9.62 4.74 (0.74) 3.93 (0.40) 4.52 (1.54) 3.96 (0.26) 3.71 (0.52) 5.67 (0.25) 4.78 (0.59) 5.26 (0.48) 4.29 4.26 (0.16) 5.20 (0.34) 4.68 (0.38)
Proximal colon
Distal colon
2.20 (0.27) 2.60 (0.62)
2.86 (0.48) 5.02
5.44
4.36 (0.17) 7.31 3.94 (0.87) 5.08
(1.28) 12.91 3.79 (0.34) 4.74 (0.82) 4.38 (1.14) 5.05 (0.61) 6.42 (1.10) 4.84 (1.06) 5.00 (0.12) 4.65 (0.48) 3.06 3.71 (0.48) 5.53 (0.96) 5.41 (0.44)
(1.06)
(1.46) 4.14 (0.76) 4.39 (0.63) 5.44 (1.60) 5.62 (1.28) 4.24 (0.09) 5.14 (0.70) 3.08 4.09 (0.89) 3.92 (0.34) 6.77 (1.36)
E. T. CLEMENS
222 Table
38. Mean
Food
(+SEM)
acetate to propionate ratio as observed at various sites along the gastrointestinal major and sub-feeding groups of wild ruminants
Rcticulorumen
selection
MAJOR GROUPS Browsers
3.62 (0.34) 4.19 (0.32) 4.24 (0.19)
Intcrmediatc Grazer\
SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prcfcrs browse (Intermediate) Prefers grarc (Intcrmediatc) Fresh gass (Grarcrs) Roughage
2.93 (0.19) 4.82 (0.39) 4.49 (0.29) 3.93 (0.2’)) 3.6X (0.34) 4.31 (0.10) 5.13 (0.1 I)
(Gra7crs)
Drq region (Grazers)
Abomasum
Weight
3C. Mean
(iSEM)
Proximal colon
Distal colon
7.x3 (0.97) 6.44 (0.89) 7.44 (0.61)
4.88 (0.69) 4.04 (0.24) 4.89 (0.17)
4.13 (1.03) 5.15 (0.44) 4.7x (0.27)
4.07 (0.49) 4.78 (0.58) 4.96 (0.43)
6.1 I (0.62) 5.25 (0.68) 4.38 (0.47) 4.32 (0.47) 5.1 I (0.X6) 5.02 (0.70) X.45 (2.53)
6.61 (0.79) 9.96 (2.04; 6.46 (1.64) 6.43 ( I .64) 6.68 (0.77) X.87 (1.17) 6.27 (0.80)
3.53 (0.48) 7.24 (0.82) 4.28 (0.30) 3.87 (0.30) 5.24 (0.27) 4.66 (5.X7) 4.6X (0.38)
2.31 (0.24) 7.31 (2.07) 4.41 (0.68) 5.80 (0.6X) 4.x0 (0.30) 4.40 (0.58) 5.41 (0.44)
3.4x (0.57) 5.10 (0.74) 4.56 (0.90) 4.97 (0.90) 5.02 (0.44) 3.x7 (0.3X) 6.77 ( 1.36)
1982). and even in non-herbivorous mammals (Banta 1980). Studies suggest that these acids within the lower tract play a vital role in sodium, bicarbonate and fluid transport (Argenzio rt (II.. 1977, 1978). in maintaining osmotic balance (Maloiy and Clemens. 1980a). and as an available energy source (Stevens ct u/., 1980). Few investigators have studied the molar proportion of VFA’s within the lower tract. However, caecal-colonic VFA concentrations within traditional omnivores (i.e. swine, baboon, monkey) (Clemens rt ~1.. 1975: Clemens and Phillips. 1980; Clemens and Maloiy, I98 I ). carnivores (i.e. dog, raccoon) (Banta et trl.. 1979: Clemens and Stevens, 1979) and insectivores (i.e. hedgehog, bushbaby) (Clemens, 1980) approach and sometimes exceed those values observed within the reticula-rumen
ct cd., 1979; Clemens,
acetate to propionate ratio as observed at various sites along the gastrointestinal seven weight .groups of wild ruminants
group
Less than 20 kg 20 50 kg 51 -100 kg 101~150 kg I51 ~200 kg 200~300 kg More
Section of tract Small intestine C&cum
than 300 kg
*Regression analysis (P < 0.003). t(F i 0.007). )’ = 3.66 + 0.25x.
Reticulorumen 2.94* (0.15) 4.04 (0.27) 4.29 (0.46) 4.31 (0.20) 4.92 (0.23) 3.96 (0.38) 4.72 (0.56) ?’ = 3.27 +0.22X
tract of the
5.80 (0.47) 4.35 (0.36) 5.81 (0.73)
lower, and fermentation rates more rapid in small ruminants (Hoppe et ul., 1977a.b; Maloiy et rd., 1982). Although the molar proportion of acetate and butyrate appeared unaffected by body weight. total reticula-rumen VFA concentrations were significantly greater in the smaller animals (Clemens and Maloiy, 1983); thus, acetate and butyrate quantities are greater. It is generally accepted that volatile fatty acids account for 7S--8O’!,, of the energy fermented within the reticula-rumen (Sutton, 1979). However, it is less frequently noted that VFA’s are an important component of gut contents in the lower tract of ruminants (Maloiy and Clemens, 1980a.b; Maloiy et al.. 1983), in the gastrointestinal tract of non-ruminant herbivores (Stevens ct al., 1980: Clemens and Maloiy, Table
er (II
Abomasum 5.33 (0.72) 4.43 (0.53) 4.82 (0.45) 5.33 (1.36) 8.15 (1.98) 6.02 (0.87) 4.16 (0.52)
Section of tract Small intestine Caecum 6.X7 (0.61) X.86 (1.73) 5.16 (0.64) 10.33 (2.15) 6.14 (0.64) 6.60 (0.83) 7.70 (0.92)
3.751_ (0.47) 4.X6 (0.70) 3.Y4 (0.22) 4.25 (0.16) 4.60 (0.31) 5.07 (0.34) 5.74 (0.36)
tract of the
Proximal colon
Distal colon
2.17 (0.40) 6.X4 (1.01) 4.89 (0.48) 3.71 (0.47) 4.03 (0.5X) 4.78 (0.27) 4.x0 (0.61)
3.63 (0.46) 5.14 (0.93) 4.3 I (0.20) 4.0x (0.X9) 6.03 (1.28) 4.7x (0.44) 4.60 (0.44)
VFA’s in East African
contents of domestic cattle. In the earlier study on wild ruminants, VFA concentrations within the caecum and colon reached concentrations equivalent to 65”, of that observed within the forestomach (Clemens and Matoiy, 1983). Furthermore, the molar proportions of VFA observed in the mid and hindgut of these wild ruminants appeared more responsive to diet and to body weight of the animal, than did foregut VFA’s. The reason for such findings is as yet unknown. Conflicting results and confusing theses add to the difficulty of interpretation. TWO schools of thought presently prevail regarding the availability of fermentable substrate within the lower tract. One suggests a more rapid reticula-rumen emptying rate in smaller ruminants (Hoppe, 1977) and in the concentrate selectors (Kay rt ul., 1980), thus creating conditions for a reduction in the time available for reticula-rumen degradation processes. Such conditions Favor the enhancement of more undigested materials reaching the lower tract. The other school of thought suggests a more rapid reticula-rumen fermentation rate in smaller animals and in concentrate selectors (Hoppe er ul., 1977a,b). Under these conditions more fermentable substrates are degraded within the forestomach per unit time, thus reducing the amount of available substrate reaching the lower tract. While both digestive strategies may be occurring simultaneously, the present data would suggest the former to be the more prevalent. This is evident from the higher proportions of acetate and acetate:propionate ratios observed in grazers relative to browsers, and in the large bodied animals relative to smaller ones. Because the ruminant forestomach effectively controls the release of contents to the lower tract, creating a uniform flow of ingesta (Sellers and Stevens, f966). diurnal variations within the caecum and cofonic contents would not be expected. Thus the molar VFA proportions within the lower tract may be more definitive with regard to fermentation activities. The caecum-colonic fermentation rates in wild ruminants, and the importance of such rates is presently under investigation (Maloiy and Clemens. unpublished data). A~,lino~~k~,c!~[,~~~~,~/.s~-Wc are most grateful to Mr D. Sindiyo, Director. Dcpartmcnt of Wildlife Conservation and Management, for permits and assistance in obtaining rescxch spccimcns. and to the National Institute for Research in Dairying. Reading, U.K., for VFA analysis. The competent technical assistance in the field and laboratory from Dr V. Langman, Mr J. Gatihi and Mr J. Nturibi is greatly appreciated. The study was supported by research grants from the University of Nairobi. Dean’s Committee Research Funds, and from the Lcverhulme Trust. London, England. Published with the approval of the Director, Nebraska Agricultural Experiment Station, Paper No. 7070, Journal Series.
REFERENCES Arlrenzio
R. A.. Miller N. and Englchardt W. V. (1977) “Efkct of volatile fatty acids on water and ion absorption frown the: goat colon. Am. ./. Physiol. 233, 977-1002. Arecnzio R. A., Southworth M.. Lowe J. W. and Stevens LC. E. (1978) Interrelationship of Na, HCO, and volatile fatty acid transport by equine large intestine. Am. f. Pl~~~.siol. 233, E46Y-478.
wild ruminants
223
Banta C. A., Clemens E. T., Krinsky M. M. and Sheffy B. E. (1979) Sites of organic acid production and patterns of digesta movement in the gastrointestinal tK3Ct of dogs. J. Nzclr. 109, 1592~1600. Bath 1. H. and Rook J. A. F. (1963) The evolution of cattle foods and diets in terms of the ruminant concentration of volatile fatty acids. J. Agrir. Sri. 61, 341-348. Bauman D. E., Davis C. L. and Bucholtz H. F. (1971) Propionate production in the rumen of cows fed either control or high grain, low fibrc diets. .I. rtairr Sci. 54, 282-287. Clemens E. T. (I 980) The digestive tract: insectivore, prosimian and advanced primate. In Cnmpcrrrr/ic~c~ Phy,siolr~,q~~; Prbniriw Mrm~n~cds (Edi ted by SchmidtNielsen K.
224
E. T. CLEMENS et al.
acid concentrations. pH and osmolality in wildebeest on dry range in Tanzania. A,fi. J. Ecol. 17, 53-63. Lang R. A. and Brett D. J. (1966) Simultaneous measurements of the rates of production of acetic. propionic and butyric acids in the rumen of sheep on different diets and the correlation between production rates and concentrations of these acids in the rumen. Er. J. Nutr. 20, 541-552. Maloiy G. M. 0. and Clemens E. T. (1980a) Gastrointestinal osmolality, electrolyte and organic acid composition in five species of East African herbivorous mammals. J. Anim. Sci. 51, 917-924. Maloiy G. M. 0. and Clemens E. T. (1980b) Colonic absorption and secretion of electrolytes as seen in five specimens of East African herbivorous mammals. Camp. Biochem. Physiol. 67A, 21-28. Maloiy G. M. 0.. Clemens E. T. and Kamau J. M. Z. (I 982) Aspects of digestion and in ritro rumen fermentation rates in six species of East African wild ruminants. J. Zool., Lond. 197, 345-354. Sellers A. F. and Stevens C. E. (1966) Motor functions of the ruminant forestomach. Physiol. Ret>. 46, 634661.
Short H. L., Medin D. E. and Anderson A. E. (1966) Seasonal variations in volatile fatty acids in the rumen of mule deer. J. Wildl. Mgmr 30, 466. Steel R. G. D. and Torrie J. H. (1960) Principles and Procedures qf Sratistics. McGraw-Hill, New York. Stevens C. E. (I 973) Transport across rumen epithelium. In Transport Mechanism in Epitheliu (Edited by Ussing H. H.), p. 404. Munksgaard. Copenhagen. Stevens C. E., Argenzio R. A. and Clemens E. T. (1980) Microbial digestion: Rumen versus large intestine. In Digestire Physiology und Metabolism in Ruminanls (Edited by Ruckebusch Y. and Thivend P.), pp. 6855707. AVI Publishing Co., CT. Sutton J. D. (1979) Carbohydrate fermentation in the rumen-variations on a theme. Proc. Nutr. Sot. 38, 2755281. Sutton J. D. (I 980) Digestion and end-product formation in the rumen from production rations. In Digestive Physiology and Metabolism in Ruminants (Edited by Ruckebusch Y. and Thivend P.), pp. 271-290. AVI Publishing Co., CT.
Vol. 76A, No. 2. pp. 217-224,
1983
0300-Y629/83 $3.00 + 0.00 (‘8 1983 Pergamon Press Ltd
MOLAR PROPORTIONS OF VOLATILE FATTY ACIDS IN THE GASTROINTESTINAL TRACT OF EAST AFRICAN WILD RUMINANTS E. T. CLEMENS, G. M. 0. MALOIY and J. D. SUTTON* Department of Veterinary Science, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, Lincoln, NE 685X3-0905. U.S.A. Telephone: (402) 472-2952 and Department
of Veterinary
Physiology.
University
of Nairobi,
Nairobi,
Kenya,
East Africa
AbstractI. The molar proportions of seven individual VFA’s were determined at select sites along the gastrointestinal tract of sixteen species of East African wild ruminants. 2. The resulting data were statistically analyzed for species effect. and for effects due to major feeding groups (browsers, grazers. fresh grass grazers, etc.) and for body weight groups (5-750 kg animals). 3. Present data suggest that body weight, rather than diet, is the more influential factor in reticula-rumen fermentation rate, and in the molar proportion of fatty acids present. 4. The molar proportions of VFA’s observed in the mid and hindgut of these wild ruminants appeared more responsive to diet and body weight of the animal than did foregut VFA values.
INTRODUCTION
East African wild ruminants were used in the study. These included: Five Kirk’s dik-dik (Mudoqua kirki), two suni (Nesotrqu.c moscharus ). three giraffe (Giraffe came/opardrr/i.s), one gerenuk (Litocrunius walleri), two eland (Tuurotrugus orys). four Grant’s gazelle (GazrNu granti). two steenbok (Ruphicerus crtmpesfris), four impala (A.y~ceros melrtmpus), four Thomson’s gazelle (Guzeilu tkornsoni),two buffalo (Buhaluh c@er), two waterbuck (Kohus ellipsipr~mntrs). three wildebeest (Connochuetes /rcurinus). one hartebeest (Alccphalus huselaphus). three topi (Danzaliscus km&is). three mountain reedbuck (Redunca fitlcorufitlu), and four oryx (Oryx ga-_e/la). All animals were collected from their natural habitat in conjunction with wildlife management programs. Field analysis and sample collection were begun immediately after death and generally completed within one hour. Details of the field procedures were reported earlier (Clemens and Maloiy, 1983). Representative samples of gastrointestinal contents were collected from select segments of tract (the reticula-rumen, abomasum, small intestine. caecum, proximal colon. and distal colon). These samples were strained through cheese cloth, the supernatant acidified with concentrated HISO, (approx 0.5 ml per 20 ml sample) and the resulting fluids refrigerated for later analysis by gas chromatography). Data were subject to analysis of variance and regression analysis (Steel and Torrie, 1960). Comparisons were made for variance between species, weight of the animal and the major and sub-feeding groups. as reported by Hofman (1973).
Concentrations of short chain organic acids and their molar proportions, have been used as an index for a variety of aspects of ruminant nutrition and physiology. Such components may describe fermentation rates (Hungate rt al.. 1959; Lang and Brett, 1966), diet characteristics (Short et al., 1966; Hoppe et al., 1977a). energy source and available substrate (Bauman ct a/., 1971; Hoppe et d., 1977b; Sutton, 1980), osmotic regulation (Kreulen and Hoppe, 1979; Maloiy and Clemens, 1980), fluid and electrolyte transport mechanics (Dobson, 1959; Stevens, 1973), and a variety of lesser physiological functions. Most studies have been conducted on domestic livestock and, more specifically, within the ruminant forestomach (i.e. the reticula-rumen areas). While the reliability of such index components is in question (Hungate rt ml., 1961; Kay rt cd., 1980) investigators continue to pursue these numerous goals. Such is the case in the present investigation. Opportunity provided for an intensive study of the molar proportions of volatile fatty acids within the tract of sixteen species of East African wild ruminants, collected from their natural habitat. The study was expanded beyond the ruminant forestomach to include six major segments of gastrointestinal tract, from the reticula-rumen to the distal colon. Comparisons were made of gut segments. species, major feeding groups (browsers, grazers, intermediate feeders) and sub feeding groups (dry region grazers, roughage eaters, fresh grass grazers, etc.), and seven weight groups from the 5 kg dik-dik, and suni to the 750-plus kg giraffe, eland and buffalo.
RESULTS The series of Tables I4 present the analytical data for seven individual volatile fatty acids (VFA) recovered from the gastrointestinal contents of wild ruminants. The tables are further divided into mean and standard error values for species, major and subfeeding groups, and seven weight groups. With few exceptions. acetic and propionic acids comprised 8690”;;; of the molar concentration of VFA’s present at each site along the tract. However, butyric acid proportions in browsers were significantly higher within the caecum and colon, relative to the foregut
MATERIALS AND METHODS Forty-five
adult
male animals
*Address: National Shinfield. Reading.
Institute U.K.
representing for
Research
I6 species of Dairying.
217
E. T. CLEMENS el al.
218 Table I A. Food selection
and mean ( + SEM) molar percent of acetate in the total volatile fatty acids as observed sites along the gastrointestinal tract of sixteen species of wild ruminants Reticulorumen
Species: Food selection BROWSERS Kirk’s Dik-Dik: Fruit and dicotyledon Suni: Fruit and dicotyledon Giraffe: Trees and shrub Gerenuk: Trees and shrub
Abomasum _ ~~_ ~
GRAZERS African Buffalo: Fresh grass Waterbuck: Fresh grass Wildebeest: Fresh grass Hartebeest: Roughage Topi: Roughage Mountain Reedbuck: Roughage Oryx: Dry region
Proximal colon
Distal colon
84.4
54.2
47.2
52.4
(1.1) 13.4
(1.8) 53.6 (6.7) 70.8 (2.5) 85.2
(4.2) 65.5 (3.3) 71.2
(4.4) 61.9
(0.6) 80.2 (5.1) 92.0
(2.4) 64.4 (0.8) 70.4 (4.9) 82.7
70.0 (4.6) 12.4 (2.0) 65.6 (1.3) 64.3 (4.9) 71.5 (1.9)
71.3 (0.7) 6X.8 (2.5) 54. I (5.3) 12.5 (1.7) 66.0 (2.6)
73.8 (0.1) 74.4 (4.9) 80.6 (4.0) 66.9 (5.1) x0. I (2.9)
68.7 (4.3) 64.5 (4.6) 69.8 (6.0) 70.8 (1.1) 67.8 (2.1)
65.6 (5.3) 65.6 (1.3) 69.5 (6.7) 69.0 (2.7) 74.0 (1.6)
66.7
60.2 (8.6) 62.0 (0.2) 70.0 (0.8) 65.6
65.4 (9.8) 17.1 (X.3) 75.4 (2.0) 77.7
78.3 (0.8) 14.1 (2.9) 81.0 (2.8) x2.4
78. I (0.X) 71.6
73.8
73.4
13.6 (4.2) 74.9 (0.7) 71.7
(2.0) 70.8
(2.0) 65.8
(1.8) 64.4
69.1 (0.7) 70.4 (0.6) 72.9 (1.2)
72.1 (4.4) 72.1 (1.6) 19.1 (2.4)
77.2 (0.9) 7X.6 (3.8) 77.9 (3.2)
12.7 (1.0) 75.0 (1.9) 73.5 (3.2)
69.9 (2.6) 67.9 (1.7) 70.8 (2.4)
68.7
65.1
INTERMEDIATE Eland: Prefers browse Grant’s Gazelle: Prefers browse Steenbok: Prefers browse Impala: Prefers graze Thomson’s Gazelle: Prefers graze
Section of tract Small intestine Caecum ~~ ~~~ -~ -~ ~
at various
(2.0) 63.8 (2.4) 13.2 (1.6) 69.2
69.6 (2.5) 72.6 (7.8) 72.1
(1.4)
(0.9) 15.3
(6.0) 67.9 (2.3) 68.0 (5.4) 70.5 (1.9) 65.0 (2.5)
(2.2) 69.1 (2.0) 71.5
(5.6) 61.9 (1.7) 70.8 (2.4)
I B. Mean (+ SEM) molar percent of acetate in the total volatile fatty acids as observed at various sites along the
Table
gastrointestinal
Food
selection
MAJOR GROUPS* Brovvsers Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers) *Values within a column
tract
of the major
Reticulorumen
and sub-feeding
Abomasum
groups
Section Small intestine
of wild ruminants
of tract Caecum
Proximal colon
Distal colon
67.1 (1.5) 69.1 (1.5) 68.3 (1.3)
70.l“h (2.0) 67.4h (2.1) 74.5” (1.7)
81.9” (2.1) 75.0h (2.2) 78.3”h (1.1)
63.1” (3.3) 68.0 (1.4) 73.8” (0.7)
58.2,’ (4.3) 69.3h (1.4) 71.8” (0.9)
62.(>’ (3.4) 67.6h (1.3) 69.9h (1.1)
65.1 (1.5) 72.2 (1.5) 70. I (1.6) 68.3 (2.6) 64.9 (2.6) 69. I (0.7) 12.9 (1.2)
70.5 (2.5) 69.6 (4.0) 65.7 (4.0) 68.9 (1.9) 73.2 (3.5) 72.9 (1.9) 79.7 (2.4)
81.2 (2.2) 83.2 (4.6) 75.8 (2.6) 74.2 (3.5) 78.4 (1.6) 78.5 (1.6) 17.9 (3.3)
57. I (2.5) 73.4 (4.6) 66.8 (2.7) 69.1 (1.3) 74.2 (1.3) 73.4 (1.0) 73.5 (1.9)
49.0 (2.2) 74.4 (4.0) 66.6 (1.8) 71.7 (1.7) 73.2 (1.3) 70.6 (1.7) 71.5
56.2 (3.8) 12.2 (1.2) 67.6 (1.9) 67.5 (1.X) 71.6 (1.1) 67.X (2.3) 70.8 (2.4)
with unlike superscripts
are different
at the 0.05 level of significance
(I .O)
VFA’s in East African wild ruminants
219
Table IC. Mean (rtrSEM) molar percent of acetate in the total volatile fatty acids as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants
Weight group Less than 20 kg 20-50 kg 51-100 kg 101-150 kg 151-200 kg 20 l-300 kg More than 300 kg
Reticulorumen Abomasum _ -- _____._..-_~__._ 65.2 66.8 (1.2) (4.0) 70.8 67.5 (1.1) 11.9) 68.3 70.6 (2.9) (1.6) 69. I 72. I (0.7) (4.4) 71.5 79.2 (1.9) (1.7) 66.8 j6.4’ (2.0) (2.9) 68.5 70.0 (3.1) (2.9)
Section of tract Small intestine Caecum 81.1 (1.8)
59.9*
80.9
71.8
(2.3)
(2.2) 67.h
70.6 (3.6) 77.2 (0.9) 78.8 (2.6) 78.5 (2.3) 77.8 (2.2)
Proximal colon
(2.8)
(2.5) 72.7
(1.w 72.9 (i.6) 72.7 (1.3) 72.1 (2.6)
53.61_ (3.6) 74.9 11.7) 67.1 (1.5) 69.9 (2.6) 70.4 (I.41 73.0 (1.4) 70. I (2.2)
Distal colon 58X
(3.5j 67.2 (1.8) 69.2 (1.5) 68.7 (5.6) 69.5 (2.2) 70.x (1.2) 70.6 (1.8)
*Regression analysis (P cc 0.02) Y = 63.3 -I- 1.6X. t(P<0.006), Y =61.1 i 1.8X. $(P c O.OOl), Y = 61.4 + 1.6.X’. and midgut. These levels were also 7--9?; above the butyric acid levels at similar sites in the intermediate feeders and grazers. Acetate levels demonstrated the greatest variability among species, and among the various segments of tract (Table IA). Mean reticula-rumen acetate levels ranged from 60°d in the buffalo to 73:; in the giraffe and oryx. The percent acetate reached highest proportions within the small intestinal contents of all species except the impala and waterbuck. Analysis of acetate and the major feeding groups showed significant differences within the caecum and colonic regions. At each of the three sites, browsers had lower acetate values; grazers had the highest (Table IS). However, within the group of browsers, those animals selecting leaves of trees and shrubs (i.e. the giraffe and gerenuk) had significantly greater acetate levels within the large bowel than did fruit and di~otyledon selectors (the dik-dik and suni). The molar percent acetate within the large bowel was also related to the weight of the animal (Table IC), with heavier animals having higher values. Propionic acid levels were related to the diet and body weight of the animal (Tables 2B, C). However, the effects were signi~cant only within the reticulorumen and/or caecum of these animals. Propionate levels significantly decreased in both the reticulorumen and caecum as body weight increased (Table ?C). Furthermore such values were noted to decrease within the reticula-rumen from browsers, through intermediate feeders, to grazers. The reticula-rumen percent propionate for individual species ranged from a high of 23”;,’ in the 5 kg dik-dik to a low of 13% in the 750-plus kg eland. When the acetate to propionate ratio was considered (Tables 3A-C), significant regressions were observed only for the effect of body weight, and only within the reticula-rumen and caecum. This ratio was observed to increase with the weight of the animal (Table 3C). A near significant probability (P < 0.045) was obtained for the regression of reticula-rumen acetate:propionate ratio and the major feeding groups (Table 3B).
It shoutd be noted that the analysis of three items-body weight. major feeding group. and subfeeding group-on lactic acid concentrations was significant at alf sites in which acetate levels were significant (caecum, proximal. and distal colon) (Clemens and Maloiy, 1983). Five lesser short chain volatile fatty acids-butyric, isobutyric, Valerie, isovaleric and caprojc acids-were measured. The relationship of butyric acid levels and diet was noted earlier in Table 4. The higher levels of other short chain fatty acids (notably isobutyric and isovaleric acids) at select sites along the tract of several species. is worthy of mention. DlSCUSSlON It is generally agreed that the concentration of volatile fatty acids within the reticula-rumen is not a reliable index of their production rate (Hungate L’Ial., 1961; Kay et al., 1980). Several factors may account for this. Most importantly, reticula-rumen VFA concentrations are the combined result of production, dilution, absorption, utilization, and passage to the lower tract (Hodgson and Thomas, 1975). Obviously, when production exceeds removal absorption-utilization-passage), ’ retrculo-rurZ VFA concentrations increase. This is generally the case shortly after feeding (Kreulen and Hoppe. 1979). Consequently, infrequent feeding may introduce considerable diurnal variations (Sutton, 1980). Furthermore, these diurnal variations become more prevalent with concentrate feeding, relative to roughage diets (Hungatc et ~1.. 1961). Similarly, the molar proportion of VFA’s within reticufo-rumen contents is not a reliable index of fermentation (Bath and Rook, 1963) nor can it be construed as an index of the available substrate (Hodgson and Thomas, 1973). The results of the present study confirm the substantial variations in molar proportions of fatty acids between animals fed similar diets. Furthermore, earlier studies have shown considerable variations within the same animal and diet at different sampling times (Ishaque et al.. 1971).
220
E. T.
CLEMENS
ef ul.
Table 2A. Live weight and mean (+ SEM) molar percent of propionate m the total volatile fatty acids as observed sites along the gastrointestinal tract of sixteen species of wild ruminants Species: Live weight Kirk’s Dik-Dik: S-6 kg Suni: 557 kg Giralk: 500-750 kg
Gerenuk: 40--S I kg Eland: 400-650 kg Grant’s Gazelle: 4664 kg Steenbok: XXI I kg Impala: 53371 kg Thomson’s Garclle: 22225 kg African Buffalo: 600-X50 kg Waterbuck: 192-286 kg Wildebeest: 171-242 kg Hartcbeest: 116.-I60 kg Topi: Ill-l47kg Mountain Reedbuck: 23-28 kg Oryx: 168-209 kg
Reticulorumen
Abomasum
Section Small intestine
of tract Caecum
Proximal colon
Distal colon
22.x (I .2) 22.2 (3.1) 14.1 (0.5) IX.8
Il.3 (0.X) 15.0 (5.1) 15.4 (2.1) 9.9
13.7 (1.0) 12.2 (5.2) 10.2 (1.6) 6.3
18.9 (1.2) 13.2 (2.6) I I.0 (1.3) X.6
22.1 (2.5) 21.2 (2.5) 14.4 (3.1) 6.6
74.3 (1.5) 13.5 (2.2) 16.4 (0.5) 10.3
12.8 (2.3) 16.9 (2.3) 22.3 (I.?) 16.6 (1.7) 19.5 (2.4) 20.5 (1.3) 19.6 (0.X) 15.8 (1.2) 16.1
16.3 (0.5) 14.2 (2.4) 22.5 (4.2) 16.9 (1.4) IX.1 (3.6) 24.6 (4.2) Il.7 (2.5) 14.3 (1.4) I I.2
10.0 (0.9) 14.3 (2.3) I I.6 (0.0) 15.1
14.7
17.4 (0.2) 15.7 (2.X) 16.6
16.1 (0.6) 16.1 (0.5) 14.2 (0.4)
15.2 (3.3) 18.4 (2.3) Il.4 (2.2)
(1.X) 15.6 (4.2) 12.8 (2.2) 12.0 (3.8) 12.0 (0.9) 14.X
16.6 (1.1) 17.0 (4.4) IX.1 (1.1) 19.4 (2.1) 13.8 (0.6) 15.2 (1.6) 14.1 (0.9) 16.5
14.4 (2.0) 13.2 (2.5) 15.8 (2.6) 15.0 (0.5) 15.7 (1.2) 21.5
17.4 (2.4) 15.7 (2.8) 16.X (I .8) 17.0 (2.2) 15.9 (2.X) 13.x (2.8) 16.4 (0.2) 14.3 (1.5) 20.9
8.3 (0.2) 9.9 (2.2) 12.8 (0.9)
17.1 (0.4) 14.5 (0.6) 16.0 (1.0)
19.3 (2.0) 13.9 (2.1) 13.4 (0.X)
IX.2 (3.3) 17.6 (1.3) II.6 (1.9)
c1.4)
(1.w
Table 2B. Mean (k SEM) molar percent of propionate in the total volatile fatty acids as observed at various the gastrointestinal tract of the major and sub-feeding groups of wild ruminants
Food MAJOR Browsers
selection
at various
Section Small Intestine
Reticulorumen
Abomasum
19.9” (1.4) 17.7”h (1.1) 16.5’ (0.6)
12.9” (1.1) 17.2” (1.3) 15.2”” (1.3)
(1.1) 14.1 (1.4) II.6 (0.8)
22.6 (1.1) 15.2 (1.2) 17.2 (1.7) IX.2 (1.5) IX.2 (1.0) 16.1 (0.3) 14.2 (0.4)
12.3 (1.4) 14.0 (2.0) 16.8 (1.8) 17.6 (2.0) 16.6 (2.4) 16.0 (1.8) Il.4 (2.2)
13.2 (1.4) 9.2 (1.5) 12.5 (1.3) 15.3 (2.4) 12.6 (1.3) 9.9 ( I .4) 12.8 (0.9)
sites along
of tract Proximal colon
Distal colon
14.8” (1.4) 17.6” (0.9) 15.3” (0.4)
IX.7 (2.1) 14.8 (1.0) 15.8 (0.8)
16.6 (1.2) 16.4 (1.4) 15.4 (1.0)
17.3 (1.5) 10.4 (1.0) 16.2 (1.1) IX.8 (I.?) 14.3 (0.3) 15.9 (0.6) 16.0 (1.0)
22.2 (1.X) 12.5 (2.9) 16.0 (1.3) 13.8 (1.6) 15.5 (0.7) 17.3 (1.6) 13.4 (0.X)
17.6 (1.6) 14.8 (1.6) 16.4 (1.4) 16.4 (2.3) 14.8 (0.9) IX.3 (1.4) I I.6 (1.9)
Caecum
GROUPS*
Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers) *Values within a column
with unlike superscripts
are different
Il.8
at the 0.05 level of significance.
VFA’s in East African wild ruminants
221
Table 2C. Mean (+ SEM) molar percent of propionate in the total volatile fatty acids as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants
Weight group Less than 20 kg 20-50 kg 51-100 kg 101-150 kg 151-200 kg 20 l-300 kg More than 300 kg
Reticulorumen 22.6* (0.8) 18.3 (1.4) 16.7 (1.3) 16.1 (0.1) 14.6 (0.5) 17.3 (1.2) 15.5 (1.4)
Abomasum ~14.6 (1.9) 17.3 (2.2) 15.5 (1.4) 15.2 (3.3) Il.4 (1.7) 13.3 (1.2) 18.3 (2.0)
Section of tract Small intestine Caecum 12.9 (1.1) 12.7 (2.6) 14.7 ( i .4) 8.3 (2.0) 13.1 (0.8) 12.5 (1.3) 10.9 (1.3)
17.2t
(1.3) 16.6 (1.7) 17.4 (0.8) 17.1 (0.4) 16.1 (0.8) 14.5 (0.8) 12.9 (0.9)
Proximal colon
Distal colon
21.0 (1.7) 12.7 (1.6) 14.7 (1.4) 19.3 (2.0) 15.0 (1.7) 15.4 (0.7) 15.6 (1.4)
17.4 (1.2) 15.8
@?I 16.4 (1.6) 18.2 (3.3) 13.5 (2.4) 15.2 (1.0) 15.9 (1.0)
*Regression analysis (P < 0.003). Y = 21.2--0.9X. i(f’ < 0.006). Y = 18.3-0.6X.
While the same or similar diets may provide variations in molar proportions of acids, the question of different diets, available substrate, and the molar proportions of VFA’s needs to be considered. It can be noted that, in spite of the diversity of diets consumed by these wild ruminants, the molar proportion of VFA’s appears to be unrelated to diet, and thus to the available substrate. While reticuio-rumen propionate levels were higher in browsers and less in
grazers, neither the acetate, butyrate or acetate:propionate ratios showed an association with diet effect. From the critical evaluation of the present set of data, it appears that body weight is the more influential factor in both the reticula-rumen fermentation rate and the molar proportions of fatty acids present. Molar proportions of propionic acid are consistently higher, the acetate:propionate ratio
Table 3A. Mean (+ SEM) acetate to propionate ratio as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants
Snckes
Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle Steenbok
Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi Mountain Reedbuck oryx
Reticuiorumen 2.92 (0.23) 2.94 (0.52) 5.21 (0.13) 3.68 5.71 (1.38) 4.65 (0.89) 2.96 (0.22) 3.94 (0.34) 3.92 (0.49) 2.97 (0.60) 3.18 (0.13) 4.48 (0.37) 4.07 4.31 (0.20) 4.38 (0.15) 5.13 (0.1 I)
Abomasum 6.28 (0.44) 5.67 (2.45) 4.92 (0.84) 6.25 4.38 (0.18) 5.26 (0.82) 2.62 (1.67) 4.38 (0.40) 4.27 (0.84) 2.81 (0.87) 7.12 (2.23) 5.30 (0.48) 6.97 5.33 (1.36) 4.08 (0.66) 8.45 (2.53)
Section of tract Small intestine Caecum 6.32 (0.55) 7.33 (3.05) 8.42 (1.88) 14.60 7.44 (0.68) 5.73 (1.17) 6.94 (0.34) 4.58 (0.58) 7.91 (2.88) 6.90 (2.33) 6.95 (2.40) 6.36 (0.56) 5.57 10.33 (2.15) 8.52 (1.41) 6.27 (0.80)
2.91 (3.66) 5.07 (0.94) 4.44 (0.32) 9.62 4.74 (0.74) 3.93 (0.40) 4.52 (1.54) 3.96 (0.26) 3.71 (0.52) 5.67 (0.25) 4.78 (0.59) 5.26 (0.48) 4.29 4.26 (0.16) 5.20 (0.34) 4.68 (0.38)
Proximal colon
Distal colon
2.20 (0.27) 2.60 (0.62)
2.86 (0.48) 5.02
5.44
4.36 (0.17) 7.31 3.94 (0.87) 5.08
(1.28) 12.91 3.79 (0.34) 4.74 (0.82) 4.38 (1.14) 5.05 (0.61) 6.42 (1.10) 4.84 (1.06) 5.00 (0.12) 4.65 (0.48) 3.06 3.71 (0.48) 5.53 (0.96) 5.41 (0.44)
(1.06)
(1.46) 4.14 (0.76) 4.39 (0.63) 5.44 (1.60) 5.62 (1.28) 4.24 (0.09) 5.14 (0.70) 3.08 4.09 (0.89) 3.92 (0.34) 6.77 (1.36)
E. T. CLEMENS
222 Table
38. Mean
Food
(+SEM)
acetate to propionate ratio as observed at various sites along the gastrointestinal major and sub-feeding groups of wild ruminants
Rcticulorumen
selection
MAJOR GROUPS Browsers
3.62 (0.34) 4.19 (0.32) 4.24 (0.19)
Intcrmediatc Grazer\
SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prcfcrs browse (Intermediate) Prefers grarc (Intcrmediatc) Fresh gass (Grarcrs) Roughage
2.93 (0.19) 4.82 (0.39) 4.49 (0.29) 3.93 (0.2’)) 3.6X (0.34) 4.31 (0.10) 5.13 (0.1 I)
(Gra7crs)
Drq region (Grazers)
Abomasum
Weight
3C. Mean
(iSEM)
Proximal colon
Distal colon
7.x3 (0.97) 6.44 (0.89) 7.44 (0.61)
4.88 (0.69) 4.04 (0.24) 4.89 (0.17)
4.13 (1.03) 5.15 (0.44) 4.7x (0.27)
4.07 (0.49) 4.78 (0.58) 4.96 (0.43)
6.1 I (0.62) 5.25 (0.68) 4.38 (0.47) 4.32 (0.47) 5.1 I (0.X6) 5.02 (0.70) X.45 (2.53)
6.61 (0.79) 9.96 (2.04; 6.46 (1.64) 6.43 ( I .64) 6.68 (0.77) X.87 (1.17) 6.27 (0.80)
3.53 (0.48) 7.24 (0.82) 4.28 (0.30) 3.87 (0.30) 5.24 (0.27) 4.66 (5.X7) 4.6X (0.38)
2.31 (0.24) 7.31 (2.07) 4.41 (0.68) 5.80 (0.6X) 4.x0 (0.30) 4.40 (0.58) 5.41 (0.44)
3.4x (0.57) 5.10 (0.74) 4.56 (0.90) 4.97 (0.90) 5.02 (0.44) 3.x7 (0.3X) 6.77 ( 1.36)
1982). and even in non-herbivorous mammals (Banta 1980). Studies suggest that these acids within the lower tract play a vital role in sodium, bicarbonate and fluid transport (Argenzio rt (II.. 1977, 1978). in maintaining osmotic balance (Maloiy and Clemens. 1980a). and as an available energy source (Stevens ct u/., 1980). Few investigators have studied the molar proportion of VFA’s within the lower tract. However, caecal-colonic VFA concentrations within traditional omnivores (i.e. swine, baboon, monkey) (Clemens rt ~1.. 1975: Clemens and Phillips. 1980; Clemens and Maloiy, I98 I ). carnivores (i.e. dog, raccoon) (Banta et trl.. 1979: Clemens and Stevens, 1979) and insectivores (i.e. hedgehog, bushbaby) (Clemens, 1980) approach and sometimes exceed those values observed within the reticula-rumen
ct cd., 1979; Clemens,
acetate to propionate ratio as observed at various sites along the gastrointestinal seven weight .groups of wild ruminants
group
Less than 20 kg 20 50 kg 51 -100 kg 101~150 kg I51 ~200 kg 200~300 kg More
Section of tract Small intestine C&cum
than 300 kg
*Regression analysis (P < 0.003). t(F i 0.007). )’ = 3.66 + 0.25x.
Reticulorumen 2.94* (0.15) 4.04 (0.27) 4.29 (0.46) 4.31 (0.20) 4.92 (0.23) 3.96 (0.38) 4.72 (0.56) ?’ = 3.27 +0.22X
tract of the
5.80 (0.47) 4.35 (0.36) 5.81 (0.73)
lower, and fermentation rates more rapid in small ruminants (Hoppe et ul., 1977a.b; Maloiy et rd., 1982). Although the molar proportion of acetate and butyrate appeared unaffected by body weight. total reticula-rumen VFA concentrations were significantly greater in the smaller animals (Clemens and Maloiy, 1983); thus, acetate and butyrate quantities are greater. It is generally accepted that volatile fatty acids account for 7S--8O’!,, of the energy fermented within the reticula-rumen (Sutton, 1979). However, it is less frequently noted that VFA’s are an important component of gut contents in the lower tract of ruminants (Maloiy and Clemens, 1980a.b; Maloiy et al.. 1983), in the gastrointestinal tract of non-ruminant herbivores (Stevens ct al., 1980: Clemens and Maloiy, Table
er (II
Abomasum 5.33 (0.72) 4.43 (0.53) 4.82 (0.45) 5.33 (1.36) 8.15 (1.98) 6.02 (0.87) 4.16 (0.52)
Section of tract Small intestine Caecum 6.X7 (0.61) X.86 (1.73) 5.16 (0.64) 10.33 (2.15) 6.14 (0.64) 6.60 (0.83) 7.70 (0.92)
3.751_ (0.47) 4.X6 (0.70) 3.Y4 (0.22) 4.25 (0.16) 4.60 (0.31) 5.07 (0.34) 5.74 (0.36)
tract of the
Proximal colon
Distal colon
2.17 (0.40) 6.X4 (1.01) 4.89 (0.48) 3.71 (0.47) 4.03 (0.5X) 4.78 (0.27) 4.x0 (0.61)
3.63 (0.46) 5.14 (0.93) 4.3 I (0.20) 4.0x (0.X9) 6.03 (1.28) 4.7x (0.44) 4.60 (0.44)
VFA’s in East African
contents of domestic cattle. In the earlier study on wild ruminants, VFA concentrations within the caecum and colon reached concentrations equivalent to 65”, of that observed within the forestomach (Clemens and Matoiy, 1983). Furthermore, the molar proportions of VFA observed in the mid and hindgut of these wild ruminants appeared more responsive to diet and to body weight of the animal, than did foregut VFA’s. The reason for such findings is as yet unknown. Conflicting results and confusing theses add to the difficulty of interpretation. TWO schools of thought presently prevail regarding the availability of fermentable substrate within the lower tract. One suggests a more rapid reticula-rumen emptying rate in smaller ruminants (Hoppe, 1977) and in the concentrate selectors (Kay rt ul., 1980), thus creating conditions for a reduction in the time available for reticula-rumen degradation processes. Such conditions Favor the enhancement of more undigested materials reaching the lower tract. The other school of thought suggests a more rapid reticula-rumen fermentation rate in smaller animals and in concentrate selectors (Hoppe er ul., 1977a,b). Under these conditions more fermentable substrates are degraded within the forestomach per unit time, thus reducing the amount of available substrate reaching the lower tract. While both digestive strategies may be occurring simultaneously, the present data would suggest the former to be the more prevalent. This is evident from the higher proportions of acetate and acetate:propionate ratios observed in grazers relative to browsers, and in the large bodied animals relative to smaller ones. Because the ruminant forestomach effectively controls the release of contents to the lower tract, creating a uniform flow of ingesta (Sellers and Stevens, f966). diurnal variations within the caecum and cofonic contents would not be expected. Thus the molar VFA proportions within the lower tract may be more definitive with regard to fermentation activities. The caecum-colonic fermentation rates in wild ruminants, and the importance of such rates is presently under investigation (Maloiy and Clemens. unpublished data). A~,lino~~k~,c!~[,~~~~,~/.s~-Wc are most grateful to Mr D. Sindiyo, Director. Dcpartmcnt of Wildlife Conservation and Management, for permits and assistance in obtaining rescxch spccimcns. and to the National Institute for Research in Dairying. Reading, U.K., for VFA analysis. The competent technical assistance in the field and laboratory from Dr V. Langman, Mr J. Gatihi and Mr J. Nturibi is greatly appreciated. The study was supported by research grants from the University of Nairobi. Dean’s Committee Research Funds, and from the Lcverhulme Trust. London, England. Published with the approval of the Director, Nebraska Agricultural Experiment Station, Paper No. 7070, Journal Series.
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