Digestive physiology of East African wild ruminants

Camp. Eiothem. Phvsiol. Vol. 76A. No. 2, Printed in Great B&in

DIGESTIVE

pp. 319-333,

1983 8

PHYSIOLOGY OF EAST AFRICAN RUMINANTS

0300-9629/X3 $3.00 + 0.00 1983 Pergamon Press Ltd

WILD

E. T. CLEMENS and G. M. 0. MALOIY Department of Veterinary Physiology, University of Nairobi, Nairobi, Kenya, East Africa and Department of Veterinary Science, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln, Lincoln. NE 68583-0905, U.S.A. Telephone: (402) 4’72-2952 (Recessed 18 January 1983)

Abstract-I. The physiology of digestion of wild ruminants in their natural habitat was determined. The study consisted of fifty-one adult male animals representing sixteen species. 2. While diet and body weight were both related to the gastrointestinal composition, body weight

appeared to he the more influential factor. 3. Reticula-rumen and caecal-colon composition, relative to abomasal and small intestinal composition, showed the greater species, diet and body weight effects. 4. The buffalo, oryx and gerenuk were somewhat more unique in gastrointestinal composition than were other species of wild ruminants, and were deserving of special consideration.

INTRODUCTION

With the continued studies of both domestic and wild ruminants, knowledge of reticula-rumen physiology is rapidly expanding. Comparative information and, to a lesser extent, post-ruminal digestion studies have not been as fruitful. Furthermore, quantitative information derived from studies of different species is difficult to compare, owing to the variation in technique. The present investigation allowed for an intensive, comparative study without the variance due to technique. In addition, these animals were studied in their natural habitat, thus providing a more reaiistic comparison of wild ruminants. MATERIAL AND METHODS Fifty-one adult, male animals representing 16 species of East African wild ruminants were used in the study. These included: five Kirk’s dik-dik (~u~oq~~ ~j~~i), two suni (Nesoiraqus moschatus), three giraffe (Girafla camelopard&s), three gerenuk (Litocrumius walleri), three eland (Turotragus oryx), four Grant’s gazelle (Gazelle gruti), two steenbok (Ruph~ce~ cumpesfrjs), four impala (Aepyceros meiampus), four Thomson’s gazelle (Gazella thomsoni), three buffalo (Bubalus cuffer), two waterbuck (Kobus ellipsiprymmts), three wildebeest (Connochaefes tantinus), three hartebeest (Alcepha~~~ b~se~aph~s), three topi ~DarnuI~sc~ lunatus), three mountain reedbuck (Redunca fuiuorufuia), and four oryx (oryx gaze/la). All animals were collected from their natural habitat in conjunction with wildlife management programs. Field analysis and sample collection were begun immediately after sacrifice and generally completed within 1 hour after the death of the animal. Body weights of the animals were taken as those reported for the average species weight (Hofmann, 1973). The abdominal cavity of each animal was opened immediately after death. Urine and blood samples were collected and refrigerated. Ligatures were used to tie off the oesophagus at the cardia and the large bowel at the rectal-anal junction, and the gastrointestinal tract removed. The gastrointestinal tract of each animal was further separated by ligatures into six selected segments. These consisted of the

reticula-rumen, abomasum, small intestine, caecum, and proximal and distal halves of the colon. TotaI contents were removed from each segment, weighed, and a representative sample refrigerated for later analysis. Additional samples were strained through cheese cloth, the supematant acidified with concentrated H,SO, (approx 0.5 ml per 20 ml sample), and refrigerated for later analyses of volatile fatty acids. The dry matter content was determined by drying a portion of each sample to a constant weight in a forced-air oven at 105°C. Samples of whole gut contents were centrifuged and the supematant collected for laboratory analysis. The osmolality of the supernatant fraction was determined on a laboratory osmometer, the sodium and potassium concentrations by flame photometry, and the chloride concentration was determined with the aid of a chloridometer. The lactic acid concentration of each sample was determined by the methods of Barker and Summerson (1941). Volatile fatty acid concentrations were determined‘ by the steam distillation method of Markham (1942), and by partition chromatography of short chain fatty acids. Data were subject to analysis of variance. Duncan’s Multiple Range test, and regression analysis for determination of significant differences (Steel and Torrie, 1960). RESULTS

The series of Tables 2-8 present the analytical data for seven parameters measured in this study. Tables are further divided according to species, major and sub-feeding groups, and weight of the animal. Table 1 presents the live weight, food selection and mean weight of gastrointestinal contents, by species and for the six primary gut segments. The percent dry matter within the reticula-rumen showed considerable variability for the species investigated, ranging from a low of 10.5% (suni) to 21.8% (oryx) (Table 2A). However, when comparing sub-feeding groups, dry region grazers’ reticuIorumen dry matter was significantly greater (P < 0.05) than other groups (Table 2B). The intermediated feeders also appeared to have a higher dry matter value than most browsers or grazers. Abomasal 319

E. T. CLEMENSand G. M. 0. MALLXY

320

contents showed considerably more variability in dry matter consistency than reiticulo-rumen contents. No correlation was noted with the dry matter content of these two segments. Lowest abomasal values were noted for the buffalo (6.5%), and highest for the oryx (16.273. Intermediate feeders had abomasal dry matter values significantly lower than either browsers or grazers. However, when considering the subfeeding groups, most grazers’ abomasal dry matters were generally lower than browsers’ and comparable to intermediate feeders’, except fcr the dry region grazers. Percent dry matter within the small intestine was the only segment to show a significant (P < 0.01)

relationship with major feeding groups. Dry matter composition decreased with the ingestion of more grasses. There was a noted relationship between dry matter percent and weight of the animal for the small

intestinal contents (P < 0.01) {Table 2C). Caecal dry matters were 2-6 percentage units greater than that of the small intestine (except for the suni) and ranged from a low of 9.5% (suni) to a high of 22.2% (dik-dik). Statistically significant differences (P < 0.05) were not detected for caecal dry matter between feeding groups. However, within the group of grazers, dry region grazers had dry matter percents significantly greater (P < 0.01) than the roughage grazers.

Table I. Average live weight, food selection and total weight (kg) of gastrointestinal contents as observed in sixteen species of wild ruminants Species

Average* live weight (kg)

Food Selection Kirk’s Dik-Dik: Fruit and dicotyledon (Browsers) Suni: Fruit and dicotyledon (Browsers) Giraffe: Trees and shrub (Browsers) Gerenuk: Trees and shrub (Browsers) Eland: Prefers browse (Intermediate) Grant’s Gazelle: Prefers browse (Intermediate) Steenbok: Prefers browse (Intermediate) Impala: Prefers graze (Intermediate) Thomson’s Gazelle: Prefers graze (Intermediate) African Buffalo: Fresh grass (Grazers) Waterbuck: Fresh grass (Grazers) Wildebeest: Fresh grass (Grazers) Hartebeest: Roughage (Grazers) Topi: Roughage (Grazers) Mountain Reedbuck: Roughage (Grazers) Oryx: Dry region (Grazers) *Data

for average

live weight

Section Small intestine ---~ 10.1

of tract

S-6

Reticuiorumen -_-_-_ 0.3

S--l

0.3

500-750

85.9

8.8

7.2

9.2

3.5

I.9

N-52

4.4

0.3

0.3

0.5

0.2

0.1

78.4

6.5

5.3

3.1

3.4

2.6

4.2

0.2

0.2

0.2

0.1

0.1

8-11

0.8

CO.1

CO.1

CO.1

CO.1

53-71

4.7

0.3

0.4

0.2

0.2

22-25

2.1

400-650

4664

Abomasum __ 10.1


10.1


0.1

Caecum

Proximal colon

Distal colon


CO.1

CO.1

10.1

CO.1

10.1


0.3



CO.1

600-850

87.3

4.4

4.7

3.8

3.3

2.6

192-286

31.9

1.9

2.2

2.4

2.0

1.6

171-242

28.0

1.8

2.3

2.0

1.2

0.7

116-160

13.6

1.0

0.9

1.1

0.6

0.4

III-147

13.4

0.9

0.8

0.6

0.6

0.3

23-28

1.8

0.1

25.4

1.7

168-209

and food selection

obtained

from Hofmann,


1.9

1973.

0.2

1.9


1.6


1.4

East African wild ruminants

321

Table 2A. Mean (+ SEM) dry matter percent as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants

Species --___~Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle Steenbok Impala Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi Mountain Reedbuck oryx

Reticula-rumen 16.4 (0.6) 10.5 (1.5) 13.5 (0.5) 17.0 (1.2) 14.5 (1.5) 16.0 (1.8) 16.5 (0.5) 16.2 (1.6) 15.8 (1.6) 18.0 (7.0) 14.0 (1.0) 13.3 (0.7) 12.0 (0.8) 16.0 (1.6) 12.0 (0.6) 21.8

(2.8)

Table 28. Mean (&SEM)

Food selection MAJOR GROUPS* Browsers Intermediate Grazers SUB GROUPS Fruit & dicotyledon (Browsers) Trees & shrub

(Browsers) Prefers browse (Intermediate) Prefers graze IIntermediate) Fresh grass

(Grazers) Roughage (Grazers) Dry region (Grazers)

Abomasum I_____13.0 (1.6) 11.0 (1.0) 14.0 (0.1) 15.0 (1.2) 10.0 (5.0) 9.2 (;:;I (2.1) 8.0 (1.1) 7.8 (0.5) 6.5 (3.5) 7.5

Section of tract Small intestine Caecum 17.0 (0.5) 14.0 (0.1)

22.2 (16) 9.5 (4.5)

14.0 (0.8) 1:‘:)

18.0 (0.9) 17.0 (3.7) 13.8 (1.1) 18.0 (1.0) 18.0 (1.5) 13.2 (1.6) 15.5 (5.5) 13.0 (1.0) 20.0 (3.6) 14.0 (2.1) 16.7 (0.7) 13.0 (0.6) 20.2 (1.5)

(&

lo:o (1.7) 14.5 (1.5) 13.5 (2.5) 12.0 (2.6) (Z) (::I)

(0.5) 12.7

10.0 (1.0) 9.0 (1.2) 11.7 (1.2) 9.3 (1.4) 13.5 (2.3)

(2.6) 12.0 (1.0) 14.3 (3.5) 5.3 (2.3) 16.2

(1.2)

i 6.0 (0.1)

Proximal colon -____ 22.0 (0.4) 20.0 (4.1) 17.0 (4.0) 20.0 (3.9) 22.5 (6.5) 18.2 (1.7) 18.5 (4.2) 18.5 (1.4) 15.0 (0.9) 11.0 (1.0) 18.5 (0.5) 24.3 (2.4) 18.0 0.7) 21.3 (1.2) 16.3 (1.3) 22.6 (l..J)

dry matter per cent as observed at various sites along the gastrointestinal and sub-feeding groups

Reticula-rumen

Abomasum

Section of tract Small intestine Caecum

14.7 (0.9) 15.9 (0.7) 15.9 (1.2)

13.0” (0.8) 8.6h (0.6) 11.2”b (1.3)

14.5 (1.0) I I 8”’ (1:l) 10.5b (0.7)

18.0 (1.9) 15.6 (0.9) 16.7 (1.0)

14.7 (1.2) 14.7 0.2) 15.8 (0.9) 16.0 (1.1) 14.8 (1.8) 13.7 (1.0) 21.8 (2.8)

12.4 (1.2) 14.3 (0.3) 9.4 (1.1) 7.9

16.1 (0.7) 10.7 (1.7) 10.9 (1.4) 12.8 (;.;)

18.6 (2.8) 16.7 (0.7) 15.6 (1.2) 15.6 (1.4) 16.7 (2.2) 14.1 (0.8) 20.2 (1.5)

%) (1.7) 10.1 (2.4) 16.3 (1.2)

*Values within a column with unlike superscripts are

Distal

colon 39.0 (1.1) 27.5 (4.5) 33.5 (7.5) 65.0 (13.2) 27.0 (8.1) 32.2 (4.1) 31.5 (4.5) 29.5 (2.5) 24.5 (4.1) 15.0 0.0) 23.3 (1.5) 29.0 (4.7) 42.2 (7.1) 40.3 (2.4) 32.0 (3.6) 35.0 (6.1)

tract of the major

Proximal colon

Distal colon

20.5 (1.1) 18.1 (1.3) 19.7 (1.1)

39.2 (4.5) 31.4 (1.8) 31.3 (2.4)

21.6 (j-0) 18.0 (2.5) 19.4 (1.6) 16.7 (2.1) 18.9 (2.4) &) 18.7 (0:9) (1.2) 13.5 22.8 (2.3) (1.5) statisticatly different at the 0.0s level of significance.

35.7 (2.5) 47.3 (14.5) 30.8 (2.7) 32.0 (2.4) 23.4 (3.0) 37.0 (2.4) 35.0 (6.1)

E. T. CLEMENSand G. M. 0. MALOIY

322

Table ZC. Mean (+ SEM) dry matter per cent as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants Weight group

Reticula-rumen

Less than 20 kg 20-50 kg 51-100 kg 101-150 kg 151-200 kg 201-300 kg More than 300 kg

15.1 (1.0) 14.5 (1.1) 16.1 (1.1) 16.0 (0.6) 19.8 (2.9) 13.6 (0.5) 15.3 (2.0)

Abomasum 11.7 (1.1) 7.8 (&) (0.6) 14.3 (3.6) 15.4 (1.3) 10.6 (1.9) 10.2 (2.1)

Section of tract Small intestine Caecum 15.x* (0.6) 11.2 (1.4) 11.8 (1.5) 11.7 (1.2) 12.6 (2.0) 9.8 (0.6) 8.3 (1.1)

-18.4 (2.1) 13.8 (1.0) 15.9 (1.2) 16.7 (0.7) 19.0 (1.9) 17.2 (2.6) 16.2 0.8)

Proximal colon

Distal colon

20.9 (0.9) 16.1 (0.8) 18.4 (2.1) 21.3 (1.2) 21.8 (1.5) 22.0 (1.9) 16.8 (2.9)

34.8 (2.1) 38.6 (5.7) 30.9 (2.3) 40.3 (2.4) 36.4 (4.9) 26.8 (2.9) 25.2 (4.4)

-..-._

*Regression analysis (P < 0.006); Y = 15.2 - 0.9X.

Drying of faecal material was readily apparent in the proximal and distal colon of all species except the buffalo. Values ranged from 15% (buffalo) to 65% (gerenuk). Browsers had significantly drier contents ~thin the distal colon than did grazers or intermediate feeders. Considerable variability was observed for the concentration of volatile fatty acids (VFA) within the

reticula-rumen of each species (range, 93.4 mmol/l (buffalo) to 183.5 mmol/l (oryx)) (Table 3A). A relationship was apparent for feeding group and VFA concentration within the reticuio-rumen, with browsers having higher values and grazers having lower values (Table 3B). Sub-feeding groups showed a similar pattern except for dry region grazers. There was also a statistically significant (P < 0.01) re-

Table 3A. Mean ( &SEM) volatile fatty acid concentration (mmol/l) as observed at various sites along the gastrointestinal tract of sixteen species of wild ~minants

.-~ Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle Steenbok Impala Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi Mountain Reedbuck Oryx

Reticula-rumen 151.6 (8.4) 141.2 (9.0) 106.4 (10.6) 154.2 (8.3) 98.6 (1.5) 148.3 (12.3) 127.2 (16.9) 146.1 (21.0) 117.4 (14.4) 83.4 (9.0) 123.9 (6.4) 103.2 (7.2) 84.7 (7.0) 101.6 (6.9) 107.7 (6.1) 183.5 (9.1)

Abomasum 12.5 (3.5) 15.6 (1.5) 17.0 (0.2) $?!5j 17.9 (0.8) 19.9 (7.7) 27.8 (2.9) 19.2 (9.2) 12.9 (;:;I (1.0) 11.0 (4.2) 17.0 (1.8) 17.2 (1.9) 8.2 (1.9) 10.1 (2.0) 29.0 (6.9)

Section of tract Small intestine Caecum 8.1 (1.8) 20.7 (10.0) 10.6 (4.6) 37.0

68.7 (7.6) 59.6 (10.2) 68.8 ($)

(8.4) 16.8 (2.3) 14.9 (2.8) 7.2 (0.7) 14.0 (3.1) 10.2 (2.6) 13.3 (I 1.3) 17.6 (11.8) 7.1 (2.0) 3.0 (1.0) 3.2 (0.4) 9.4 (3.3) 42.8 (6.3)

(6.1) 62.6 (3.6) 71.8 (8.2) 83.1 (13.1) 63.5 (13.6) 59.2 (7.4) 37.0 (12.4) 45.4 (3.0) 43.2 (2.5) 39.8 (2.1) 33.2 (3.8) 49.8 (3.3) 90.6 (5.0)

Proximal colon 64.6 (9.9) 77.6 (6.8) 63.6 (17.0) 52.3 (6.9) 74.9 (10.9) 57.0 (5.1) 61.2 (27.2) 60.6 (13.8) 51.8 (4.6) 18.6 (3.8) 38.8 (12.6) 50.1 (6.2) 51.7 (3.5) 30.8 (4.4) 30.6 (8.1) 74.0 (5.3)

Distal colon ___~ 49.1 (14.6) 57.8 (1.0) 45.4 (16.6) 74.8 (10.3) 54.3 (9.3) 52.9 (7.6) 69.8 (16.2) 53.2 (11.6) 39.0 (13.0) 15.0 (6.3) 33.0 (6.2) 55.0 (12.3) 45.3 (9.9) 42.0 (4.3) 52.5 (20.1) 54.9 (11.0)

East African wild ~minants

323

Table 38. Mean (_fSEM) volatile fatty acid concentration (mmol/l) as observed at various sites along the gastrointestinal tract of the major and sub-feeding groups Section of tract

Food selection MAJOR GROUPS* Browsers Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Rou~a~ (Grazers) Dry region (Grazers)

Small

Proximal

~eticulo-amen

Abomasum _.

intestine

Caecum

colon

Distal colon

149.7’

(10.9)

13.1 (2.1) 18.7 (3.0) 15.2 (2.5)

14.0 (3.5) 12.8 (1.4) 16.4 (4.0)

65.1 (5.9) 66.9 (4.4) 52.5 (5.4)

65.8” (5.9) 59.2” (4.7) 44.3b (5.0)

52.7 (7.8) 51.8 (5.2) 44.7 (5.3)

148.6 (6.4) 122.3 (17.1) 130.6 (10.1) 131.8 (13.0) 89.3 (15.3) 101.8 (4.6) 183.5 (9.1)

13.4 (2.5) 12.5 (4.5) 21.4 (3.9) 16.0 (4.7) 12.3 (2.2) 10.3 (1.6) 29.0 (1.2)

11.7 (3.4) 19.4 (9.2) 13.4 (1.9) 12.1 (2.1) 11.8 (4.1)

66.1 (5.9) 62.6 (16.5) 72.4

68.3 (7.4) 59.9 (;;:;)

(5.3) 61.4 (7.2) 42. I (3.3) 41.2 (3.7) 90.6 (5.0)

(6.6) 56.0 (6.8) 37.8 (6.5) 33.7 (4.6) 74.0 (5.3)

(7.4) 131.2”h (8.0)

I iS.Ob

(:::) 42.8 (6.3)

51.6 0;;) (13:7) 57.5 (5.7) 46.1

(8.5) 36.7 (9.4) 46.9 (8.0) 54.9 (11.1)

*Values within a column with unlike superscripts are statistically different at the 0.05 level of significance.

lationship between the weight of the animal and reticula-rumen VFA concentrations (Table 3C). However, this relationship is less clear when comparing the individual mean values for weight groups.

Abomasal and small intestinal VFA ~oneentrations were considerably lower than that of the reticulorumen contents. VFA concentrations within the animal’s caecum were l/3-1/2 that observed within the forestomach (33.2-90.6 mmolj). WhiIe no significant difference was noted, browsers and intermediate feeders generally had higher caecal VFA values than grazers. VFA concentrations tended to decrease from caecum to distal colon for most species, and feeding groups. VFA concentration and feeding group were

significantly (P < 0.005) related within the proximal colon. Concentrations were noted to increase with the ingestion of more browse. Reticula-rumen lactic acid concentrations were less than 5% of that for VFA’s. Lactic acid concentrations remained low throughout the entire gastrointestinal tract of all species (Table 4A). Caecal and colonic lactic acid concentrations were significantly higher (P < 0.05) in browsers and intermediate feeders than in grazers (TabIe 4B). There was also a signi~cant negative relationship between lactic acid concentrations and an increase in body weight for the caecum and colonic segments of the tract (Table 4C). Reticula-rumen osmolality ranged from 232 mOsm

Table 3C. Mean (_+SEM) volatile fatty acid concentration (mmol/l) 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 lOI--150kg 151-200 kg 201-300 kg More than 300 kg

Reticula-rumen

Abomasum

143.8” (6.4) 118.3 (8.8) 147.2 (11.3) 101.6 (6.9) 163.8 (20.9) 111.5 (6.7) 79.4 (15.0)

16.6 (2.9) 10.7 (1.9) 19.5 (;I;)

*Regression analysis (P < 0.01); Y = 151.26.8X.

(1.9) 26.7 (5.8) 14.6 (2.2) 13.8 (2.3)

Section of tract Small intestine Caecum 10.7 (2.7) 13.3 (3.8) 14.4 (1.9) 3.2 (0.1) 34.8 (9.3) 11.3 (4.7) 13.6 (3.4)

69.9 (0.3) 54.6 (4.0) 67.7 (7.5) 33.2 (3.9) 80.4 (Jo:;) (1.8) 56. I (9.8)

Proximal colon

Distal colon

66.7 (7.4) 43.7 (5.1) 58.8 (6.7) 30.8 (4.4) 69.5 (6.0) 45.6 (5.9) 52.4 (12.0)

55.6 (86) 48.5 (9.9) 53.0 (6.4) 42.0 (4.3) 53.0 (8.8) 26.8 (2.9) 37.5 (9.4)

E. T. CLEMENSand G. M. 0.

324

MALOIY

Table 4A. Mean (+ SEM) lactic acid concentration (mmol/l) as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants

Species Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle

Reticuio-rumen 3.2 (0.8) 12.6 (0.6) 0.6 (0.1) 0.8 (0.2) 1.4 (0.2) 4.2 (1.3)

Steenbok Impala Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi

(Z) 8.2 (2.4) 9.4 (4.8) 1.7 (1 .O) 5.0 (2.1) 3.6 (0.9) 0.6 (0.2) 1.9 (@i)

Mountain Reedbuck oryx

(0.4) 11.7 (4.7)

Section of tract Small intestine Caecum

Abomasum

(6::) 2.9

0.2 (0.1)

(1.0)

($)

(“0::) 0.3 (;:;)

(0.9)

(0.1) 1.1 (0.2) 1.8 (0.1) (Z) (:%) 0.9 (‘;‘.A) (0:i) 0.8 (0.2) ($ (::;) 0.7 (0.1) 2.7 (1.1)

c:::, 0.9 (0.7) 2.8 (1.7) 3.2 (0.2) (ii;,

1.9 (0.8) 0.2 (0.1) 1.3 (0.8) 2.2 (1.1) 0.0 (0.0) 0.1 (0.1) 0.4 (0.4) 0.6 (0.5)

2.5 (0.4) 1.6 (0.4) 1.0 (0.4) 1.1 (0.4) 0.8 (0.5) 3.7 (2.0) 2.4 (0.6) 0.8 (0.3) 1.4 (0.3) 0.4 (0.1) 0.4 (0.l) 0.6 (0.2) 0.1 (0.3) 0.7 (0.2) 0.4 (0.2) 0.4 (0.1)

Proximal colon - _--__ 1.9 (0.3) 0.0 (0.0) 1.6 (1.0) 6.1 (2.0) 0.9 (0.8) 3.2 (0.9) 4.0 (2.0) 0.7 (0.3) 3.4 (1.1) 0.4 (0.2) 0.4 (0.2) 0.4 (0.2) 0.7 (0.4) 0.6 (0.1) 0.3 10.2t 1.8 (1.4)

Distal colon 3.5 (0.8) 0.0 (0.0) 0.1 (0.1) 9.8 (2.7) 1.0 (0.7) (Z) (Z) 4.8 (2.4) 1:::) 0.6 (0.4) (SY) 0.5 (0.3) 1.1

(0.5) 0.6 (0.1) 0.3 (0.2) 1.8 (1.4)

Table 4B. Mean (+SEM) lactic acid concentration as observed at various sites along the gastrointestinal tract of the major and sub-feeding groups Food selection ~-MAJOR GROUPS Browsers Intermediate Grazers SUB GROUPS Fruit and d~cotyiedon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers)

Reticula-rumen --. ----.~-_..~_.--3.3 (1.3) 5.9 (1.5) 4.6 (1.4) 4.8 (1.7) 0.7 (0.1) 2.9 (0.8) 8.8 (::;I (0.8) 1.7 (0.3) 11.7 (4.9)

Abomasum _ (A:!, r:.:, (A::)

(Z, 0.7 (y.;) (0:2) (‘0::) I.1 (0.2) $1 d::)

Section of tract Small intestine Caecum __._ ._~ ___ _ 0.8dh (0.5) 2.0” (0.5) 0.7h (0.3) 0.1 (;:;) (1.0) ($ 1.6 (0.6) 1.4 (0.6) 0.2 (0.1) 0.6 (0.4)

1.9” (0.3) 10:; 0.5h (0.1) 2.4 (0.4) 1.1 (0.3) 2.7 (t-0) 1.1 (0.2) (:::) 0.6 (0.1) 0.4 (0.1)

Proximal colon

Distal colon

2.1” (0.6) 2.4” (0.5) 0.4h (0.1)

3.0” (1.1) 3.4” (0.7) 0.9” (0.3)

1.6 (0.4) 3.3 (1.8) 2.8 (0.4) 2.0 (0.7) 0.4 (0.1) 0.4 (0.1) 0.6 (0.1)

2.9 (0.8) 3.3 (i:i)

*Values within a coiumn with unlike superscripts are statistically different at the 0.05 level of significance.

(0.8) 3.2 (1.3) 0.6 (0.1) 0.6 (0. I)

__

_-

East African wild ruminants

325

Table 4C. Mean (+ SEM) lactic acid concentration (mmol/l) as observed at various sites along the gastrointestinal of the seven weight groups of wild ruminants Weight group Less than 20 kg 20-50 kg Zf-100 kg 101-150 kg 151-200 kg 201-300 kg More than 300 kg

Reticula-rumen

Abomasum

4.0 (1.3) 5.5 (2.9) 4.2

(Z) 1.4 (0.6) 1.5

(1.5) 1.9 (0.3) 9.4 (4.4) 4.1 1.2 (0.9)

(0.4) 0.6 (0.1) 2.2 (0.1) 1.1 (0.2)

(0.4)

(K)

Section of tract Small intestine Caecum

1.1 (0.5) 2.0

I.0 (;:;I

(0.9)

(1.1)

(0”::) 0.4

(i::)

Proximal colon

Distal colon

2.2t (0.6) 2.6 (1.0)

3.8$ (0.9) 2.3 (0.1) (Z)

(:::)

(A:;) 0.6 (0.1) 0.6 (0.1)

(;:;) (0.7) 1.4

(00::) 0.8

(“o?) 0.9

1:::) 0.6 (o”.;)

(0.6)

(0.2)

(0.4)

(0:3)

tract

(oO:t

*Regression analysis (P < 0.01); Y = 2.3 - 0.3X. t(P < 0.~9); Y = 2.7 -0.3X. $iP < 0.005); Y = 4.3 -0.5X.

(buffalo) to 518 mOsm (oryx) (TabIe SA). There was an apparent relationship between osmolality and diet, with browsers having higher values than intermediate feeders, followed by grazers. There was also a highly significant relationship (P < 0.004) between reticula-rumen osmolality and body weight

(Table 32). Abomasal osmolality was generally isotonic to plasma. Only the oryx demonstrated hypertonicity of abomasal contents. Small intestinal contents were consistently hypertonic to plasma for all species (Table 5A). However, small intestinal osmolality significantly decreased (P < 0.006) with the

Table 5A. Mean (k SEM) osmolahty (mOsm) as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants

Species Kirk’s Dik-Dik Suni Giraffe Gerenuk Eland Grant’s Gazelle Steenbok Impala Thomson’s Gazelle African Buffalo Wdterbuck Wildebeest Hartebeest Topi Mountain Reedbuck Oryx

Reticu~o-rumen 456 (27) 500 (3) 314 (15) 444 (26) 362 (5) 420 (30) 571 (64) 335 (31) 405 (44) 234 (59) 349 (75) 287 (18) 242 (24) 353 (44) 400 (28) 518 (48)

Abomasum 308 (26) 318 (9) 300 (20) 348 (19) 314 (58) 344 (32) 359 (11) 284 (31) 282 (68) 216 (8) 278 (18) 247 (61 273 (37) 269 (4) 278 (12) 429 (59)

Section of tract Small intestine Caecum 633 (35) 715 (115) 471 (102) 611 (98) 518 (74) 542 (126) 696 (67) 588 (66) 546 (48) 435 (7) 480 (140) 397 (43) 406 (46) 437 (8) 547 (38) 415 (25)

359 (38) 267 (41) 260 (10) 410 (69) 338 (87) 387 (29) 415 (5) 386 (54) 308 (36) 296 (11) 315 (4) 249 (12) 292 (29) 317 (26) 367 (6) 378 (16)

Proximal colon 355 (13) 257 (3) 274 (33) 302 (30) 408 (83) 350 (41) 347 (32) 314 (34) 329 (29) 222 (15) 296 (33) 271 (44) 326 (54) 277 (34) 345 (44) 333 (40)

Distal colon 206 (18) 306 (80) 218 (40) 445 (38) 377 (62) 348 (89) 456 (34) 375 (43) 245 (16) 205 (3) 298 (83) 302 (34) 190 (45) 309 (8) 321 (74) 352 (52)

326

E. T.

CLEMENSand

G. M. 0.

MALOIY

Table 5B. Mean (+_SEM) osmolality (mOsm) as observed at various sites along the gastrointestinal tract of the major and sub-feeding groups Food selection

Section of tract Small Caecum intestine

Reticula-rumen

MAJOR GROUP* Browsers Intermediate Grazers SUB GROUPS Fruit and dicotyledon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Inte~ediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers)

615”

Proximal colon

Distal colon

435* (25) 407 (24) 367 (27)

293 (18) 312 (21) 298 (21)

(42) 571” (37) 449b (19)

326 (26) 364 (20) 324 (12)

314”h (16) 367” 09) 299h (16)

252b (29) 346” (29) 30Pb (21)

468 (21) 357 (44) 443 (34) 370 (28) 289 (28) 351 (29) 518 (49)

282 (25) 316 09) 340 (19) 283 (35) 246 (11) 214 (5) 439 (59)

656 (38) 518 (99) 547 (67) 567 (39) 431 (38) 480 (28) 415 (25)

333 (32) 310 (50) 382 03) 347 (16) 281 03) 335 (16) 378 06)

321 (20) 284 (21) 382 (33) 352 (22) 264 (20) 313 (23) 333 (40)

234 (28) 293 (79) 383 (46) 310 (32) 273 (30) 297 (33) 352 (35)

*Values within a column with unlike superscripts at-e statistically different at the 0.05 level of significance.

consumption of grasses (Table 5B). The osmolality of caecum and colonic contests were near isotonic to plasma. Only the gerenuk demonstrated a significantly elevated osmolality of distal colon contents. Osmolaiity of the teticulo-rumen, small intestine and caecum contents showed an important relationship to body weight, being higher in lighter animals (Table 5C). Sodium ion concentrations within the reticulorumen of the 16 species of wild ruminants ranged from 55mEq/l (suni) to 122mEq/l (gerenuk) (Table 6A). Intermediate feeders had significantly (P < 0.05) lower reticula-rumen values than did browsers or grazers (Table 68). Body weight was not related to increased

reticula-rumen sodium ion concentrations; these were diminished within the abomasum of all species. However, small intestinal sodium levels were similar to that of the reticula-rumen. Concentrations generally decreased from small intestine to distal colon in all species. No apparent sodium effect was noted at any site for either major feeding group, sub-feeding group or weight group. Potassium ion concentrations within the reticulorumen varied almost four-fold for the species investigated (giraffe 34 mEq/l to dik-dik 126 mEq/l) (Table 7A). Significant regressions were noted for major and sub-feeding groups as well as weight groups (Tables 7B, C). Statistically significant re-

Table SC. Mean (+SEM) osmolality (mOsm) as observed at various sites along the gastrointestinal tract of the seven groups of wild ruminants Weight group

Reticula-rumen

Less than 20 kg 2@-50kg 51-100 kg 101-150 kg 151-200 kg 201-300 kg More than 300 kg

491* (24) 408 (23) 377 (26) 353 (44) 462 (67) 312 (29) 304 (28)

Abomasum 300 (22) 289 (32) 314 (23) 269 (4) 398 (55) 259 (10) 277 (25)

*Regression analysis (P < 0.004); Y = 486.&24.8X.

t(P < 0.001); Y = 658.9-35.8X. :(P < 0.04); Y = 377.1-10.6X.

Section of tract Small intestine Caecum 665t (32) 555 (27) 565 (67) 437 (8) 413 (19) 430 (55) 474 (46)

351$ (27) 343 (22) 2x7 (29) 317 (26) 361 (21) 215 (17) 298 (27)

Proximal colon

Distal colon

332 06) 332 (21) 362 (25) 277 (35) 332 (31) 281 (22) 325 (55)

824 (39) 298 (35) 361 (46) 309 (8) 320 (52) 300 (36) 266 (40)

East African

Table 6A. Mean (k SEM) sodium

Species Kirk’s

Dik-Dik

Suni Giraffe Gerenuk Eland Grant’s

Gazelle

Steenbok Impala Thomson’s African

Gazelle

Buffalo

Waterbuck Wildebeest Hartebeest Topi Mountain

Reedbuck

Oryx

Table 68.

Mean (_+SEM)

Food selection MAJOR Browsers

wild ruminants

327

ion concentration (mEq/l) as observed at various of sixteen species of wild ruminants

Reticula-rumen

Abomasum

91.3 (6.6) 55.5 (4.5) 95.8 (15.8) 121.5 (14.1) 56.1 (29.3) 77.2 (14.8) 76.5 (12.9) 57.4

50. I (7.2) 14.2 (0.6) 48.2 (6.9) 55.0 (9.8) 72.0 (22.0) 49.2 (8.4) 79.9

(7.6) 72.8 (13.4) 63.4 (6.6) 84.8 (14.4) 70.3 (4.0) 63.5 (10.9) 101.0 (22.5) 101.9 (5.8) 97.7 (10.8)

(8.0) 40.0 (7.7) 51.0 (19.0) 47.0 (3.0) 39.7 (8.4) 32.0 (8.7) 65.3 (4.4) 58.0 (4.6) 74.0 (2.6)

sodium

(;;:;)

Section Small intestine ___. 83.1 (5.2) 73.2 (21.2) 77.5 (7.5) 97.0 (13.9) 84.8 (23.1) 85.2 (14.0) 93.8 (10.2) 83.5 (10.1) 62.0 (8.1) 91.0

(1.0) 77.5 (21.5) 65.0 (29.0) 86.0 (21.7) 121.3

Caecum 77.4 (14.4) 24.4 (1.4) 44.8 (14.8) 90.4 (18.7) 40.6 (13.0) 73.5 (6.3) 38.8 (12.2) 60.2 (11.4) 55.9 (13.0) 48.6 (11.4) 64.7 (12.7) 19.8 (3.8) 51.0 (10.0) 81.0 (7.1) 37.4

(7.0) 74.0 (21.3)

(5.9) 85.2 (20.4)

ion concentration (mEq/l) as observed at various of the major and sub-feeding groups

Reticula-rumen

Abomasum

colon 63.9 (10.9) 24.2 (6.4) 32.6 (0.3) 93.3 (19.2) 28.2 (19.6) 55.5 (10.4) 25.2 (2.0) 36.7 (11.1) 58.1 (12.1) 23.4 (11.4) 30.6 (6.8) 30.7 (5.8) 53.1 (8.9) 67.4 (13.9) 28.2 (0.6) 69.6 (27.6)

sites along

Distal colon 21.9 (5.2) 12.4 (3.2) 19.4 (2.8) 30.7 (9.1) 25.0 (20.2) 32.1 (9.3) 30.7 (15.1) 29.7 (16.3) 17.6 (6.3) 14.0 (3.0) 24.1 (19.0) 55.6 (24.0) 16.2 (8.4) 49.0 (22. I) 17.5 (3.1) 27.4 (7.9)

the gastrointestinal

of tract Proximal colon

Distal colon

61.6 (10.6) 57.3 (5.5) 57.4 (7.4)

52.6 (9.0) 44.3 (7.8) 45.5 (7.6)

20.4 (3.0) 26.8 (5.2) 31.6

62.2 (14.1) 60.0 (I 7.4) 56.6 (8.0) 58.0 (8.1) 40.9 (8.8) 58.0 (9.0) 85.2 (20.4)

52.6 (10.6) 52.8 (20.8) 41.1 (8.2) 47.4 (8.6) 28.6 (3.9) 48.6 (9.1) 69.6 (27.6)

19.2

Caecum

GROUPS 88.1

43.0

Intermediate

(7.4) 68.4

$0:

Grazers

(6.1) 87.2

(5.7) 56.3

(5.6)

(3.9)

(5.6) 85.7 (6.5)

81.1

39.8

80.2

(8.1) 104.3 (12.5) 71.8 (9.1) 65.1 (7.7) 72.5

(8.3) 50.5

(5.3) 45.0

(5.1) 96.0 (10.3) 97.7 (10.8)

(5.6) 57.4 (5.1) 74.0 (2.6)

(6.1) 84.0 (7.8) 87.2 (8.3) 72.7 (7.2) 76.0 (6.5) 102.0 (8.1) 74.0 (21.3)

SUB GROUPS Fruit and dicotyleoon (Browsers) Trees and shrub (Browsers) Prefers browse (Intermediate) Prefers graze (Intermediate) Fresh grass (Grazers) Roughage (Grazers) Dry region (Grazers)

(4.5) 62.6 (9.2) 43.8

81.4 (4.7) 80.0

tract

of tract

(9.3) 88.0

Section Small intestine

sites along the gastrointestinal

(6.4)

(4.0) 23.2 (4.1) 30.0 (6.5) 23.6 (8.4) 34.7 (12.8) 30.8 (10.6) 27.4 (7.9)

tract

E. T. CLEMENS and G. M. 0.

328 Table 6C. Mean (+SE?4)

sodium

ion concentration (mEq/l) as observed at various of the seven weight groups of wild ruminants

Weight group Less than

Reticula-rumen RO.I (6.6) 89.8

20 kg

20-50 kg

(9.4) 61.3 (6.8) 101.0 (22.5) 90.9 (10.8) 76. I (6.2) 71.7 (I 1.7)

51~100 kg 101-150 kg 151~200 kg 20@300 kg More than

300 kg

gressions were also noted for feeding groups for all segments

potassium

Abomasum 48.7 (9.7) 48.6 (5.1) 48.5 (5.3) 65.3 (4.3) 65.6 (6.8) 42.6 (5.0) 57.1 (9.0)

and

major

of tract from reticulorumen to proximal colon (Table 7B). Furthermore, potassium ions were observed to decrease in concentration from caecum to distal colon in browsers and to increase in grazers. Reticula-rumen chloride values ranged from 6.0 mEq/l (hartebeest) to 24.2 mEq/l (Grant’s gazelle)

Table 7A. Mean (+SEM)

Kirk’s

Abomasum

Dik-Dik

126.4 (17.3) 125.8 (2.8) 34.4 (5.5) 45.9 (5.9) 47.8 (9.5) 65.4 (7.1) 97.6 (13.6) 62.8 (6.4) 78.6 (8.5) 63.4 (6.6) 58.2 (5.4) 39.8 (5.4) 42.3 (7.8) 37.2 (8.4) 46.9 (5.4) 39.4 (7.5)

17.3 (2.3) 101.0 (42.2) 27.2 (1.7) 24.0 (4.0) 34.2 (1.8) 40.9 (1.8) 54.2 (9.6) 38.8 (2.9) 44.2 (7.2) 30.5 (6.5) 54.0 (2.0) 53.6 (8.7) 60.0 (11.2) 36.0 (4.6) 37.7 (1.7) 26.1 (2.6)

Gerenuk Eland Grant’s

Gazelle

Steenbok Impala Thomson’s African

Gazelle

Buffalo

Waterbuck Wildebeest Hartebeest Topi Mountain

Reedbuck

Section Small intestine

sites along

the gastrointestinal

tract

of tract Caecum

83.2 (5.4) 76. I

57.0 (11.5) 53.2

(7.0) 84.4 (8.1) 121.3 (9.3) 76.4 (16.7) 70.0 (7.6) 84.4 (6.7)

(8.9) 66.9 (6.5) 81.0 (7.1) 78.4 (17.3) 37.8 (11.9) 44.7 (6.5)

Proximal colon

Distal colon

46.5 (9.1) 51.3 (9.8) 46. I (7.9) 67.4 (13.9) 66.3 (21.6) 30.7 (3.8) 28.0 (6.1)

21.7 (4.3) 19.2 (3.5) 30.9 (8.7) 49.0 (22.1) 25.2 (6.5) 43.0 (16.8) 19.5 (5.6)

(Table 8A), and were noted to decrease in concentration with the increase in body weight and grass consumption (Table 8C). There were no relationships between chloride ion and body weight or feeding group for the remaining segments of tract. Chloride ions were highest within the abomasum and diminished in concentration with subsequent distal segments of tract for all species (Table 8A).

ion concentration (mEq/l) as observed at various of sixteen species of wild ruminants

Reticula-rumen

Giraffe

Oryx

potassium

Species

Suni

MALOIY

Section Small intestine 91.9 (9.0) 52.7 (12.2) 33.2 (3.8) 31.0 (8.5) 73.8 (0.6) 26. I (3.6) 53.2 (7.0) 62.8 (8.6) 41.2 (7.3) 38.0 (2.0) 39.0 (3.0) 50.3 (3.1) 34.0 (4.8) 28.7 (2.4) 38.0 (4.0) 26.2 (8.9)

sites along the gastrointestinal

of tract Caecum

Proximal colon

Distal colon

120.6 (19.6) 46.4 (0.4) 90.0 (20.0) 15.1 (2.1) 97.2 (1.3) 33.0 (2.0) 65.2 (0.4) 78.7 (14.8) 64.8 (13.7) 75.3 (12.7) 44.8 (6.2) 81.9 (4.0) 60.8 (3.4) 45.4 (5.8) 66.6 (4.9) 41.1 (15.4)

107.4 (13.5) 37.5 (10.8) 94.4 (13.7) 51.5 (8.3) 100.3 (5.3) 34.0 (5.8) 52.2 (17.6) 75.8 (17.3) 66.4 (4.5) 67.4 (19.5) 69.8 (6.8) 80.3 (8.4) 72.0 (7.1) 45.5 (8.6) 66. I (4.9) 44.8 (14.9)

50.4 (7.0) 31.7 (7.2) 79.9 (15.3) 30.7 (6.4) 93.6 (21.0) 49.6 (11.7) 48.6 (4.8) 87.2 (15.3) 53.9 (7.1) 77.2 (19.6) 74.0 (12.4) 83.8 (14.5) 60.6 (9.3) 71.7 (19.8) 53.9 (15.5) 41.9 (5.7)

tract

East African wild ruminants

329

Table 7B. Mean (It SEM) potassium ion concentration (mEq/l) as observed at various sites along the gastrointestinal tract of the major and sub-feeding groups Food selection

~ --~-. MAJOR GROUPS* Browsers 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)

Reticula-rumen

Abomasum

Section of tract Small intestine Caecum

Proximal colon

Distal colon _______-

99.8” (15.8) 69.9b (4.8) 42.4’ (3.0)

66.7” (I 1.7) 42.0” (2.4) 38.1h (3.4)

66.3” (10.0) 48.2” (5.0) 35.8 (2.7)

89.1” (15.8) 64.4”” (7.0) 5?.7b (5.3)

85.2” (I 1.8) 63.1ah (5.8) 61.2b t5.01

53.7 (6.7) 65.4 (6.9) 64.4 (5.9)

126.1 0;:;’

84.1 (10.3) 26. I (1.4) 42.6 (3.4) 41.4 (3.7) 47.1 (5.6) 35.8 (4.9) 26. I (2.6)

80.7 (9.9) 32.5 (2.3) 44.8 (7.8) 51.6 (6.5) 43.6 (2.8) 33.4 (2.5) 26.2 (8.9)

99.4 (19.3) 65.0 (27.5) 57. I

87.4 (16.1) 80. I (16.4) 55.1 (11.1) 71.1 (8.5) 73.6 (5.8) 58. I (5.7) 44.8 (14.9)

45.0 (6.2) 73.7 (10.8) 60.3 (9.9) 70.5 (10.0) 79.1 (7.7) 62.5 (10.1) 41.9 (5.71

(5.01 69.0 (8.1) 70.7 (5.81 44.6 (5.6) 42. I (4.2) 39.4 (7.5)

(10.1) 71.8 (9.7) 69.4 (7.4) 55.4 (5.4) 41.1 (15.4)

*Values within a column with unlike superscripts are statistically different at the 0.05 level of significance.

DISCU~ION

Twenty-six species of wild ruminants can be found in East Africa (Hofmann, 1973). The majority of

these species still abound and are dispersed throughout the diverse environmental habitat of Kenya. The arld range, mountainous, savanna, and tropical forest regions of this country support a variety of animal life. Wild ruminants inhabit each of these ecosystems. Hofmann (1973) has categorized these animals into three major feeding groups: concentrate selectors (browsers) which have a diet of high nutritive value, low fiber, and high protein content; bulk and roughage eaters (grazers) whose diet is largely grass, which is often of high fiber and low protein content; and

inte~ediate feeders whose diet consists of grasses and browse. He further subdivides the species into seven categories based according to their food preference within the major feeding groups. In the present study sixteen of the twenty-six species of wild ruminants were investigated. These animals represent members from all major and subfeeding groups. The immense diversity of weight range is also present within the sixteen species-from the tightest weight (suni and dik-dik) to the heaviest (giraffe, buffalo and eland). With the exception of the omasum, an analysis of the total gastrointestinal contents was conducted for each species. Composition of the contents at the six

Table 7C. Mean (*SEM) potassium ion concentration (mEq/l) as observed at various sites along the gastrointestinal tract of the seven weight groups of wild ruminants Weight group

-.Less than 20 kg 2g-50 kg 51-100 kg lol--1.50 kg 15I--200 kg 201-300kg More than 300 kg

Reticula-rumen _..119.8* (10.3) 62.6 (7.4) 64. I (4.4) 37.2 (8.4) 40.0 (5.8) 47.2 (5.6) 40.1 (11.6)

Abomasum IlSf (9.2) 39.2 (4.2) 39.8 (1.6) 26.0 (4.6) 32.9 (7.1) 53.8 (4.8) 30.6 (2.2)

*Regression analysis (P < 0.001); Y = 106.l-l I .3X. t(P < 0.002); Y = 63.8-5.0X $(P < 0.003), Y = 43.8 + 5.1X.

Section of tract Small intestine Caecum 74.6 (8.6) 38.7 (3.8) 44.1 (8.0) 28.7 (2.4) 27.8 (7.11 45.8 (3.4) 48.3 (8.2)

91.8 (15.5) 59.3 (9.1) 55.9 (11.1) 42.4 (5.%) 45.0 (12.6) 67.1 (9.5) 87.4 (7.3)

Proximal colon 19.6 (13.6) 64.4 (2.9) 54.9 (I 1.6) 45.5 (8.6) 50.3 (12.8) 76. I (5.3) 87.4 (9.0)

Distal colon 45.81 (4.8) 54.8 (6.0) 68.4 (11.4) 71.7 (19.%) 45.7 (5.8) 79.9 (9.2) 83.6 (9.0)

330

E. T. CLEMENSand G. M. 0. MALOIY

Table 8A. Mean (& SEM) chloride ion concentration (mEq/l) as observed at various sites along the gastrointestinal tract of sixteen species of wild ruminants

Species Kirk’s Dik-Dik Suni

Reticula-rumen

Abomasum

19.5 (2.3) 15.0

128.6 (13.8) 84.0 (9.0) 98.7 (19.7) 152.0 (21.5) 88.2 (5.8) 151.5 (31.8) 110.2 (14.0) 62.6 (5.2) 13.5 (22.5) 117.0 (3.0) 116.1 (8.8) 116.0 (9.3) 123.3 (1.3) 96.7 (4.1) 119.2 (6.6)

(0.1) Giraffe

8.4

Gerenuk

12.2 (1.3) 7.6 (2.5) 10.0 (4.0) 13.4 (2.3) 13.1 (2.1) 7.6 (2.3) 19.5 (5.7) 10.7 (1.8) 6.0 (1.8) 10.9 (1.1) 10.0 (0.4) 10.3 (0.9)

(0.1) Eland Steenbok Impala Thomson’s Gazelle African Buffalo Waterbuck Wildebeest Hartebeest Topi Mountain Reedbuck Oryx

Section of tract Small Caecum intestine 41.9 (1.3) 52.8

(2.8) 61.2

(8.2) 48.3 (4.3) 39.2 (7.2) 46.8 (7.0) 66.2

(8.0) 41.3 (11.2) ‘75.0’ (34.0) 49.0 (1.0) 63.2 (10.9) 105.0 (27.3) 52.7 (4.9) 57.7 (10.4) 54.2 (19.1)

37.8 (2.4) 29.6 (0.8) 32.6 (7.2) 27.1 (3.1) 31.2 (8.1) 37.3 (4.6) 44.4 (3.3) 32.8 (5.6) 36.6 (5.4) 35.6 (3.4) 30.8 (0.9) 48.6 (5.2) 30.9 (1.6) 39.9 (2.4) 33.1 (4.2)

Proximal colon

Distal colon

34.6 (2.0) 17.8 (0.1) 31.8 (1.0) 9.0 (1.1) 36.2 (11.7) 31.2 (2.8) 38.4 (9.3) 39.9 (7.1) 30.9 (9.3) 21.4 (1.6) 37.5

23.9 (4.7) 17.0 (1.4) 28.4 (1.7) 9.0 (2.6) 32.9 (15.5) 29.2 (8.9) 33.8 (5.3) 19.5 (7.6) 27.2 (4.6) 24.2 (3.6) 32.0 (5.3) 12.1 (3.1) 37.3 (7.7) 27.2 (9.6) 5.9 (0.8)

(6.0) 36.0

(2.1) 35.0 (5.2) 45.1 (2.0) 27.2 (4.5)

Table 8B. Mean (k SEM) chloride ion concentration (mEq/l) as observed at various sites along the gastrointestinal tract of the major and sub-feeding groups Food selection MAJOR GROUPS* Browsers 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)

Reticula-rumen 15.7” (1.8) 12.7ab (1.5) 10.9s (1.0)

Abomasum 101.8 (14.0) 97.6 (11.1) 110.1 (4.6)

Section of tract Small intestine Caecum 59.0 (11.5) 52.2 (6.1) 60.7 (5.3)

34.0 (2.1) 37.1 (2.8) 35.0 (1.5)

Proximal colon

Distal colon

32.1 (3.0) 37.3 (3.9) 34.2 (2.3)

22.6 (2.7) 28.1 (4.0) 23.8 (3.3)

115.9 45.0 35.4 29.8 (12.7) (3.4) (2.3) (2.2) 9.6 118.8 61.5 30.7 37.3 (18.0) (1.3) (4.3) (4.5) (5.5) 11.9 119.8 43.0 34.2 33.7 (22.5) (3.5) (4.4) (4.2) (5.1) 13.2 86.4 56.8 38.6 39.2 (11.4) (1.4) (7.3) (3.7) (5.4) 12.3 104.2 62.8 33.8 32.7 (2.4) (9.9) (1.8) (3.5) (9.4) 9.8 110.8 62.3 37.3 39.7 (0.8) (5.4) (2.8) (8.4) (3.0) 10.3 119.2 54.2 33.1 27.1 (19.0) (0.9) (6.6) (4.2) (4.5) *Values within a column with unlike superscripts are statistically different at the 0.05 level of significance. 18.2

(1.8)

22.0 (3.5) 24.0 (4.5) 31.0 (7.4) 26.6 (5.1) 28.4 (2.7) 29.4 (5.8) 5.9 (0.8)

East African wild ruminants

331

Table 8C. Mean (+ SEM) chloride ion concentration (mEq/l) 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

-__

Reticula-rumen 16.4* (1.9) 11.8 (1.1) 15.5 (2.8) 10.9

(2.8) 151-200 kg

9.4

Abomasum 123.8 (12.8) 68.7 (10.3) 110.2 (14.0) 123.3 (1.3) 118.5

(1.1) 201-300 kg More than 300 kg

14.2 (3.0) 7.9 (0.9)

(5.2) 116.5 (4.9) 86.8 (9.1)

Section of tract Small intestine Caecum ._______ 45.4 35.8 (2.1) (1.9) 34,7 (E) (3.2) 66.2 44.4 (SO) (3.3) 52.7 30.9 (5.0) (1.6) 64.4 36.2 (I 7.9) (4.5) 57.6 32.7 (I.71 (6.9) 58.8 33.5 (13.4) (3.3)

Proximal colon

Distal colon

30.1 (2.6) 43. i (3.6) 38.4 (9.3) 35.0 (5.2) 28.9 (3.9) 33.4 (4. Li 33.0 (4.0)

23.6 (3.2) 21.9 (5.0) 33.8 (5.3) 37.3 (7.i) 7.2 (4.1) 28.8 (3.6) 29.5 (4.3)

*Regression analysis (P < 0.008); Y = 16.2-1.0X.

primary sites-the reticula-rumen, the abomasum, the small intestine, the caecum, the proximal, and the distal colon-is presented herein. Additional information concerning the electrolyte absorptionsecretion, partition VFA’s, etc. will be presented in subsequent publications. Analysis of gastrointestinal contents as a means of assessing nutritional and physjoio~cal functions of the digestive tract is an established and accepted procedure (Elsden et al., 1946; Alexander, 1965; Stevens et al., 1979). While limitations are inherent in the technique, such procedures may reveal valuable information, particularly when they are comparative. The forestomach of domestic and wiId ruminants has been the subject of several investigations. Researchers have suggested that both diet (Bath and Rook, 1963; Hoppe et al., 1977a) and size of the animal (Hungate et al., 1959; Hoppe, 1977; Maloiy et al., 1982) influence reticula-rumen fermentation rates. VFA concentrations noted in the present study support these earlier findings, since the VFA concentrations were observed to decrease with the increase in body weight and the increased consumption of grasses. In addition, the molar proportion of propionic acid and the acetate to propionate ratio suggest the occurrence of a more rapid fermentation rate, in accordance with the VFA concentration (unpublished data). However, the reticula-rumen lactic acid values were apparently not altered by the rate of fe~entation, as reported by other investigators. Assuming that both diet and body mass influence reticula-rumen fermentation rate, the question arises as to which factor exerts the more prominent effect. Present evidence suggests that body weight is most influential. Such evidence is derived from the test of higher significance for body weight compared to feeding groups, and from dn vitro fermentation data. For example, the giraffe and gerenuk are both browsers preferring trees and shrubs, yet they have a IO-fold difference in body weight. However, fermentation rates (pm01 gas NTDP/gDM/hr) were 587; more rapid in the smaller animal (Maloiy et ai., 1982). Similar examples are demonstrated with the intermediate feeders (eland and Grant’s gazelle)

(Hoppe et al., 1977b; Maloiy et al., 1982) and for the grazers (buffalo and wildebeest) (Hoppe et al., 1977a; Maloiy et af., 1982). Conversely, those animals of similar weight but different dietary habits (e.g. giraffe and buffalo) have comparable reticula-rumen fermentation rates (Maloiy et al., 1982). Within the pH range of reticula-rumen contents, most organic acids are dissociated and are subsequently osmotically active (Dobson, 1959). Therefore, the association between reticula-rumen osmolality and diet, or body weight, tends to reflect VFA concentrations. Potassium, rather than sodium, ion concentration appears to be the major cation influencing forestomach osmolality. Like osmolality and VFA concentration, potassium concentrations significantly decrease with an increased proportion of grass in the diet, and with an increase in body weight. However, in this instance, dietary effect appears to be a more prevalent factor than body weight. It follows that, in general, dicotyledons (browse) contain greater potassium levels than monocotyledon (grasses). Few investigators of ruminant physiology and nutrition consider the gastrointestinal tract beyond the point of reticula-rumen functions. Thus, the comparative data from the abomasum to the distal colon provides considerable new information. The abomasum of wild ruminants may contain as much as 8.8 kg of ingesta (giraffe) or as little as 0.1 kg (several species). The dry matter consistency of abomasal contents is generally depressed by 1-8 percentage units over that of reticula-rumen contents. Browsers, compared to inte~ediate feeders and grazers, show the least variation between gut segments. Body weight has no measurable relationship to abomasal dry matter. The organ is, however, a major site for electrolyte absorption-secretion and/or dilution. Thus, relative to reticula-rumen contents, abomasal composition is markedly different. VFA concentratjons within the glandular stomach are reduced by 70 to 9.5%. Lactic acid values were much less affected. Significant effects of diet and of body weight on these organic acids, on osmolality, and on chloride values, were not apparent within the abomasal con-

332

E. T. CLEMENS and G. M. 0. MALOII

Only potassium values within the organ appeared to have a carry-over effect from the reticulorumen. The small intestine of all mammals is the site of intensive digestion, absorption and secretion activities. The composition of small intestinal contents of these sixteen species of wild ruminants appears sensitive to diet and body weight. Small intestinal dry matter, osmolality. and potassium concentrations were each influenced significantly by diet and/or body weight, The drier intestinal consistency, hypertonicity and increased potassium concentrations suggest a greater intestinal fluid absorption within browsers and light animals than in their respective counterparts. The caecum-colon of herbivorous mammals represents the second major site of fermentative activity. A recent review (Hoover, 1978) describes the present knowledge of digestive processes within the hindgut of domestic ruminants. Minimal information is available on the hindgut of wild ruminants (Skadhauge et al., 1980; Maloiy et cd., 1982). While the reticulorumen area of browsers is relatively smaller than that of grazers (Hofmann, 1969; Hofmann and Stewart, 1972; Arman and Hopcraft, 1975) the reverse is true for the caecum and colon. From present data, it appears that browsers retain an average of 13. I”/; of the total ingesta within the large bowel compared to I 1.57; for grazers. Reticula-rumen contents were 74.6 and 77.5”: for browsers and grazers, respectively. It is also apparent that the caecum of browsers is the more voluminous segment of the large bowel, while the colon of grazers generally contains more ingesta. The volume of ingesta within the large intestine of domestic sheep has been shown to vary with diet (Grovum and Hecker, 1973). Similarly, hindgut fermentation rates of domestic ruminants respond to available substrate with increased microbial numbers, decreased pH and changing VFA ratios (Mrskov et al., 1970, 1971; Mann and 0rskov, 1973; Allison et al., 1975). However, in the present study, neither VFA concentrations nor acetate to propionate ratios within the hindgut of browsers and grazers were appreciably different (unpublished data). On the other hand, lactic acid values were significantly different for the feeding groups. The data does, however, clearly show the ability of each species to conserve colonic fluid, VFA and sodium, and to a lesser extent. potassium and chloride ions. Certain members within the sixteen species of wild ruminants deserve special consideration. The African buffalo is one such animal. It is unique among East African wild ruminants in that it is the only species which does not form a faecal pellet. The dry matter consistency of contents within the distal colon (15%) was significantly less than all other species investigated. Subsequently, the buffalo’s ability to conserve faecal water loss appears limited. Colonic drying of ingesta entering the large bowel (caecum to distal colon) was evident in all species except the buffalo. However, while a significantly greater proportion of fluids were lost in the faeces of the buffalo, less VFA and sodium ions were excreted per unit of fluid volume, even when these values were adjusted to a comparable dry matter consistency of other species. What appears most unusual is the high dry matter tents.

consistency of the buffalo’s reticula-rumen contents. The 17% dry matter is 2-6 percentage units greater than most wild ruminants. And even though the African buffalo depends on available drinking water (Sinclair, 1974; Field, 1976) these values are comparable only to those of arid range ruminants (i.e. gerenuk and oryx) which rely almost exclusively upon plants for their source of fluids (Hofmann, 1973). The unusually high dry reticula-rumen contents of the buffalo have been reported elsewhere (Maloiy et al., 1982). As mentioned earlier, the gerenuk and oryx inhabit the arid regions of East Africa. The gerenuk is a strict browser, while the oryx is a grazer (Hofmann, 1973). Like the buffalo, they exhibit an elevated reticulorumen percent dry matter, the oryx significantly so. On the other hand, the gerenuk demonstrates a significantly higher faecal dry matter. The data would suggest a greater ability of the gerenuk to conserve faecal water loss, and greater reticula-rumen recycling of these fluids relative to the oryx. The oryx also demonstrated a high reticula-rumen VFA concentration which did not fit well with the pattern of fermentation rate and diet or body size.

Acknow~ledgements-We are most grateful to Mr D. Sindiyo, Director, Department of Wildlife Conservation and Management, for permits and assistance in obtaining research specimens, and to Dr J. Sutton, National Institute for Research in Dairying, Reading, England, for VFA analysis, Mr S. Ngonga of the Nutrition Laboratory, University of Nairobi conducted the proximate analyses for which we are most grateful. The component technical assistance in the field and laboratory from Dr P. Hoppe. Dr V. Langman, Mr J. Gatihi and Mr J. Nturibi. The study was supported by research grants from the University of Nairobi, Dean’s Committee Research Funds. and from the Leverhulme Trust, London, England. Published with the approval of the Director, Nebraska Agricultural Experiment Station, Paper No. 7071, Journal Series,

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