W. Sørmo

In vitro digestibility of different prey species of minke whales ( Balaenoptera acutorostrata )

Information on diet composition, daily energy expenditure, energy storage and the utilization of energy in the prey are important factors when evaluating the food consumption of minke whales (Balaenoptera acutorostrata) during their summer stay in northern waters. The purpose of the present study was in this context to obtain information on the digestible energy (DE) of different prey selected by minke whales. An in vitro three-stage digestion technique, simulating the different compartments of the digestive system, has been developed. The initial step simulated the anaerobic microbial fermentation of substrate in the forestomach. The next stage included the addition of pepsin (EC 3.4.23.1)-HCl, simulating ventricle enzymic decomposition, and finally, in the third step, fresh extract from duodenal contents was used to simulate enzymic intestinal degradation of the remaining components of the food. The inoculum was normally obtained from animals which had recently eaten the prey to be tested. In such tests we obtained a dry matter disappearance (DMD) and a DE for herring (Clupea harengus) of 80.4 (SD 5.0)% (n 18) and 92.1 (SD 3.7)% (n 16) respectively, and a DMD of krill (Thysanoessa sp.) of 83.4 (SD 4.9)% (n 6). The DMD of krill was reduced to 73.8 (SD 7.3)% (n 8) while the DE was 70.6 (SD 10.4)% (n 7) when inoculum from whales which had recently eaten cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) was used. These results indicate a high digestibility of the most common species of prey in these animals, and also that the whales have little difficulty in changing from one prey species to another.

Forage chemistry and the digestive system in reindeer (Rangifer tarandus tarandus) in northern Norway and on South Georgia

Comparative chemical and botanical analyses of the reticulo-rumen content (RR) and the fill of the digestive system were carried out in free-living Norwegian reindeer {Rangifer t. tarandus) on South Georgia (SG) in summer (mean body mass (BM) = 74 kg, n - 10), and in northern Norway in late summer (NS) (mean BM = 77 kg, n = 6) and winter (NW) (mean BM = 60 kg, n = 11). The RR of SG reindeer contained mainly grasses, while grasses dominated in NS reindeer and woody plants and lichens in NW reindeer. Mean ruminal plant cell-wall contents (CWC) comprised 37% of organic dry matter (OM) in SG reindeer and 50 and 69% in NS and NW reindeer, respectively. The high CWC in NW reindeer was due to high intake of lichens containing as much as 45% hemi-cellulose. Mean ruminal content of lignin was as low as 5% of OM in SG reindeer, which was different (P < 0.05) from NS (14%) and NW reindeer (15%), respectively. The mean total gastro-inresrinal tract (GIT) (fill and tissue) weight was 27% of BM in SG reindeer, different (P < 0.05) from NS (18% of BM) and NW reindeer (22% of BM), respectively. Wet weight RR content was 14.5% of BM in SG reindeer, not different from NS (12.2% of BM) and NW reindeer (14.2% of BM). The ratio between the wet weight content of the distal fermentation chamber (DFC) and the RR wet weight content was 1:10 in SG reindeer, different (P < 0.05) from NS (1:14) and NW reindeer (1:14). We did not find any significant differences between the intestinal lengths of the groups investigated. It was concluded that the degree of fill of the different parts of GIT in reindeet seems to be related to the lignin content of plants eaten and not only of seasonal changes in appetite and availability of plants. Our data stress the fact that reindeer are highly adaptable to a wide range of different dietary plants, even in the southern hemisphere.

Comparative aspects of volatile fatty acid production in the rumen and distal fermentation chamber in Svalbard reindeer

Microbial fermentation end products were investigated in Svalbard reindeer at two different locations, on Nordenskioldland (NL) (n=7) and in a marginal area on Nordaustlandet (NA) (n=11), at different seasons. The pH ranged from 6.51-6.70 in rumen contents and from 6.78-7.17 in the distal fermentation chamber (DFC=caecum and proximal part of the colon) on NL compared to 6.10-6.71 in rumen contents and 6.50-7.35 in DFC contents on NA. The ruminal volatile fatty acid concentration ([VFAJ) was 84.5 ± 9.5 mmol/l compared to 63-9 ± 17.6 mmol/kg in the DFC on NL in winter. In autumn, ruminal and DFC [VFA] was high at 113.5 ± 13.0 mmol/l and 90.4 ± 10.9 mmol/kg, respectively. On NA ruminal [VFA] was 85.7 ± 12.4 mmol/l and 59-6 ± 1.3 mmol/kg in the DFC in winter, compared to 107.3 ± 18.4 mmol/l and 102.0 ± 12.7 mmol/kg in rumen and DFC, respectively, in summer. Mean acetate/propionate (A/P) ratios in the rumen indicate fermentation in favour of plant fibre digestion in winter (4.8) but not in autumn (3.0) on NL. On NA, the mean A/P ratio was 5.1 in winter, compared to 4.6 in summer. In all DFC investigated the A/P ratio was higher than 8.9. The initial ruminal [VFA] did not reflect the VFA production measured. On NL, the production rate of VFA was low or not detectable in rumen and DFC in winter, while in autumn the total production rate of VFA was 59.3 kJ/kgW0 75/d, of which 6.5% originated from the DFC. On NA in winter, a total of 121.3 kJ/kgW0 7S/d was estimated of which 17% originated from the DFC, compared to a total of 380.4 kj/kgW0.75/d in summer where the DFC only contributed 2.7%. Plants (grasses and mosses) with low quality in winter do not seem to contribute significantly to the VFA production in rumen and DFC. VFA production in the DFC seems to be of significant importance in reindeer when pastures have low availability but high quality. The concenttation and the rate of VFA production in the DFC contents were not related to the size of the chamber, but to the diet eaten.

The bacteriology of the small intestinal mucosa of free-living reindeer

Bacteria in close associaton with the intestinal mucosa are thought to protect the mucosa from pathogenic microorganisms. The pH of the small intestinal mucosa and the viable populations of aerobic and anaerobic bacteria associated with the proximal and distal jejunal mucosa, were measured in four free-living reindeer in winter. The anaerobic bacterial populations were characterized. The median pH of the mucosa of the duodenum was 6.6 (n=4) at point 0.2 m from the pyloric sphincter. The mucosal pH increased along the length of the intestine to 8.3 at 14 m and then decreased to 7.9 at 19.8 m from the pyloric sphincter. Examination by transmission electron microscopy and cultivation techniques failed to reveal any bacteria on the mucosa of the proximal jejunum in two of the animals. In two other reindeer the median anaerobic bacterial densities in the proximal jejunum ranged from 25-2500 cells/g mucosa. The median anaerobic bacterial populations in the distal jejunum ranged from 80 to 20000 bacteria/g mucosa (n=4). The anaerobic population of bacteria in the proximal jejunum was dominated by streptococci and unidentified gram positive rods. Bacteroidaceae, streptococci and unidentified gram positive rods were common in the distal jejunum. The low density and the species diversity of bacteria in the small intestine suggests that these microorganisms are inhibited by components in the natural winter diet of reindeer. Bacteria evidently play a minor role in protection of the mucosa of reindeer in winter.

Digestion of timothy silage and hay in reindeer

Leafy timothy (Phleum pratense) silage (S), silage mixed with molasses (SM) and hay (H) were fed to nine male reindeer (Rangifer tarandus tarandus) calves in winter to investigate rumen function and digestion. Three calves were given S with 18.5% dry matter (DM), three were given SM (21.9% DM) and three were given H (85.0% DM). The content of water soluble carbohydrates (in % of DM) was 8.2% in S, 16.0% in SM and 8.5% in H. Median (range) daily DM food intake per kg BM was 12.9 (9-2-14.4) g in calves fed S, 19.0 (19-0-21.9) g in calves fed SM and 21.0 (19.2¬21.1) g in calves fed H. In vivo digestion of S and SM DM ranged from 78.5-83.1% compared to only 69-9-72.9% in calves fed H. In vitro DM digestion (IVDMD) of cellulose (median) incubated for 48 hours in rumen fluid was, however, significantly (F = 0.05) lower in calves fed S (24.4%) compared to calves fed SM (42.2%). Median IVDMD of cellulose (48 hours) in calves fed H was 36.4%. Total concentration of VFA (range) in the rumen fluid from reindeer fed H (99.7-113.6 mM) and was significantly (P<0.05) higher compared to animals fed S (57.7-85.9 mM) or SM (51.4-72.0 mM). Likewise, the pH of the rumen fluid (range) was significantly (P<0.05) lower in reindeer fed H (6.40-6.78) compared to animals fed S (6.97-7.30) or SM (6.79-7.27). Based on this study it is concluded that leafy timothy preserved as hay seems to be more suitable as emergency feed compared to silage. Supplementation of molasses to silage seems to stimulate food intake and ruminal cellulose digestion in reindeer. The lower intake of S compared to SM or H by reindeer may be explained by ruminal energy deficiency.

Bacteria in the small intestine of lichen‐fed Norwegian reindeer (Rangifer tarandus tarandus)

It has been suggested that lactic acid‐producing bacteria may protect the epithelium of the mammalian gastrointestinal tract from pathogenic micro‐organisms. Consistent with this, bacteria isolated from the mucosa of the small intestine of five lichenfed, semi‐domesticated reindeer included mainly Streptococcus spp. However, the population densities of bacteria associated with the mucosa and in the intestinal contents were generally low and there was a large amount of variation both between animals and with site of sampling. It therefore seems unlikely that Streptococcus spp. are essential for the function of the small intestine in captive reindeer, and their role here remains uncertain.

Digestive physiology of minke whales

Abstract The anatomy and principal function of the gastro-intestinal tract of minke whales were investigated. The stomach consists of four compartments, including an initial non-glandular forestomach followed by a glandular fundic chamber, a connecting chamber and a pyloric chamber. The length of the small intestine of minke whales is short, only four times body length, and the colon and caecum are poorly developed. the forestomach is small, containing between 5 and 80 1 of contents, with as much as 24.8% dry matter (DM). High population densities of anaerobic bacteria were found in the forestomach fluid, and adherent to the food particles. pH in the forestomach fluid ranged between 5.36 and 7.43, and the concentration of volatile fatty acids (VFAs) ranged between 49 and 486 mM. Based on these results we conclude that minke whales primarily utilize the prey they eat by microbial digestion. The contribution from VFAs to the daily energy requirements of minke whales seems to be of less importance than in ruminants. The multi-chambered stomach probably is an adaptation which increases passage time and, hence, microbial and enzymatic digestion. We suggest that the relatively small size of the stomach of minke whales, compared with that of ruminants, reflects their carnivorous diet, but does not neces-sarily indicate any reduced importance of the forestomach microbial digestion.

Cellulolysis in the fermentation chambers in Svalbard reindeer

Introduction Svalbard reindeer (Rangifer tarandus platyrhynchus) are distributed in areas with varying vegetation and rely on symbiotic rumen and DFC (distal fermentation chamber = caecum and ansa proximalis coli) micro-organisms to ferment plant fibres. Rumen wet weight content comprise from 14-24% of body mass (BM) (Staaland et al., 1979; S0rmo et al., accepted). The number of cellulolytic bacteria in the rumen fluid of Svalbard reindeer was 31.5 x 108/ml in summer and 12.6 x 108/ml in winter (Orpin et al. 1985), but only 0.9 x 108/ml and 0.09 x 108/ml in the caecum summer and winter, respectively (Mathiesen et al., 1987). The DFC of Svalbard reindeer is large and comprise 10-17% of the weight of the rumen contents (S0rmo et al., accepted). The volatile fatty acids (VFA) from this organ can contribute as much as 17% to the energy supply of Svalbard reindeer (S0rmo et al., 1997). Ruminal digestion of plant cell walls is influenced by the availability of non protein nitrogen (NPN), amino acids and carbohydrates in the rumen contents (0rskov, 1992). This work describes seasonal diffe-

Adherent bacteria in the small intestine of reindeer

Lichens, one of the most important types of plant eaten by reindeer in winter , contain different polysaccarides compared to those of vascular plants. W e investigated the ruminal bacterial populat ion w h i c h is responsible for l i chen fermentation and also microbia l response to starvation. R u m i n a l V F A consentrations, p H , dry matter content, rumen v o l u m and fluid passage time were further examined in four ad l ib . fed and starved rumen fistulated reindeer. The bacterial populat ion per m l rumen fluid was 33.98 ± 9.98 x 10» when the animals were fed l ichen. Rods and coccies occurred i n the same propor t ion . The bacterial flora decreased by 99.7 % to 0.1 ± 0.08 x 108 p e r m l rumen f luid, after 96 hours starvation. Rods dominated in the bacterial populat ion of starved animals. Adherent bacteria in the small intestine of reindeer Wenche Sormo and Svein Disch Mathiesen. Dept. of Arctic Biology and Institute of Medical Biology, University of Tromso, Box 635, N-9000 Tromso. Summary: The mammalian small intestine normal ly contains a diverse microf lora . The lactic acid bacteria w h i c h adhere to the intestinal epithel ium are thought to protect it against pathogenic bacteria. H o w e v e r , the role of bacteria i n the small intestine of reindeer is not k n o w n . W e investigated the microf lora in the intestines of 5 reindeer fed lichens and i n one reindeer i n w h i c h diarrhoea had been induced artificially by feeding concentrates. Samples of epithel ium were collected at three different sites and the p H and abundance and species composi t ion of viable bacteria at these sites was measured. Bacterial populations, expressed as the mean number of bacteria per gram wet weight of epitheliu m , varied considerably between animals fed l i chens as follows (range of means ± SD): duodenum, 0.09 ± 0.02 x 10 4 to 33.30 ± 5.30 x 10 4 ; je junum, 0.13 ± 0.01 x 10 4 to 1.00 ± 0.81 x 4 ; i leum, 0.23 ± 0.05 x 10 4 to 2.53 ± 1.00 x 10 4. C o c c i occurred more frequently than rods at all three sites in all five animals. Bacteria were more abundant i n the reindeer w i t h diarrhoea: duodenum, 64.90 ± 10.40 x 10 4 ; je junum, 13.50 ± 1.60 x 10 4 ; i leum, 42.90 ± 5.70 x 10 4 . Mos t bacteria in this animal were rod shaped. Rangifer, Special Issue No . 4,1990 13