The uptake of volatile fatty acids (VFAs) from bacterial fermentation of forage in the rumen is enhanced by the presence of papillae which greatly increase the surface area of the mucosa of the rumen. The degree of papillation, expressed as the surface enlargement factor (SEF), seems to be closely related to the level of microbial activity and the rate of production of VFAs in the rumen. In several species of wild ruminants the SEF decreases markedly in winter, apparently in response to a decrease in the quality and availability of forage and also, presumably, in the level of ruminal microbial activity. Contrary to expectation, however, no reduction in the rate of production of VFAs in winter has been detected in semi-domesticated reindeer at natural pasture in northern Norway. We investigated the body mass, the composition and quality of the diet and the morphology of rumen papillae in adult female reindeer free-living at natural pasture. Animals were slaughtered in matched aged groups of nine on four occasions: in autumn (September) and winter (November, February and March). The composition and quality of the diet was determined by morphological and chemical analysis of plant fragments recovered from the rumen. The carcass mass of the animals did not differ signi®cantly between collections. The animals ate vascular plants and lichens from 37 different genera. The composition of the diet varied little between months except for the inclusion of a substantial proportion (25.8% of fragments) of lichens in March. The mean density of rumen papillae increased from 55.6 papillae/cm 2 in September to 75.7 papillae/cm 2 in March (P < 0.001). All other parameters, including the length and perimeter of the papillae and the SEF of the rumen, were lower in March compared with September. However, the mean SEF increased from 8.8 in February to 10.6 in March (P < 0.05), indicating increased ruminal fermentation in late winter. We propose that the increase in the SEF in March might be associated with the increase in the proportion of lichens in the diet. Lichens are highly digestible in reindeer but do not score highly in conventional analyses of diet quality owing to the unusual chemical structure of the structural carbohydrates of which they are composed.

No abstract

Microbial fermentation end products were investigated in Svalbard reindeer at two different locations, on Nordenskioldland (NL) (»=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/1 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/1 and 90.4 ± 10.9 mmol/kg, respectively. On NA ruminal [VFA] was 85.7 ± 12.4 mmol/1 and 59-6 ±1.3 mmol/kg in the DFC in winter, compared to 107.3 ± 18.4 mmol/1 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/kgW 0 75 /d, of which 6.5% originated from the DFC. On NA in winter, a total of 121.3 kJ/kgW 0 7S /d was estimated of which 17% originated from the DFC, compared to a total of 380.4 kj/kgW" 7 '/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 aim of this investigation was to compare the size of salivaty glands in Svalbard reindeer {Rangifer tarandus platyrhynchus) and in Norwegian reindeer (Rangifer t. tarandus) in relation to feeding strategy, season and reproductive status. The mean body mass (BM, standard deviation j) in adult non-lactating female Svalbard reindeer was 72.0, s = 4.2, kg (n = 8) in September and 46.7, s = 7.1, kg (« = 4) in April. The mean BM of adult non-lactating Norwegian reindeer was 67.5, s = 7.7, kg (» = 8) in September and 59.2, s = 9.6, kg (n = 9) in March. In non-lactating female Svalbard reindeer the mean combined mass of parotid glands was 82.7, s = 4.5, g in September and 58.8, s = 8.7, g in April (P < 0.05). In the Norwegian reindeer the mean combined mass of the parotid glands was 95.2, s = 14.4, g in Septembet and 68.1, s = 9.5, g in Match (P < 0.05). We wete not able to find any sub-species differences in the size of the salivaty glands which could be related to phenotypic difference in feeding strategy. Both sub-species had parotid glands sizes similar to that of intermediate ruminant types, ranging from 0.11-0.14% of BM. The larger absolute size of salivaty glands in summer compared to winter reflects the importance of high rates of production of saliva when the dry matter intake and microbial fermentation is high.

Seasonal changes in the species composition and ®bre content of plant fragments in the rumen and the gross anatomy of the gastrointestinal tract were investigated in Svalbard reindeer Rangifer tarandus platyrhynchus in western parts of Spitsbergen (Nordenskio È ld Land (NL), 788N), where the tundra vegetation is relatively abundant, and on the island of Nordaustlandet ((NA) 818N) where, in the polar desert, plants are scarce. Reindeer were killed while grazing on NL in autumn (n = 19) and in winter (n = 10) and on NA in summer (n = 10) and in winter (n = 3). Rumen contents included mainly mosses and grasses in specimens from NL and mainly Saxifraga spp. in specimens from NA. The plant cell wall content of the dry organic matter in the rumen-reticulum (RR) ranged from 55% to 77% and from 43% to 57% in NL and NA specimens, respectively, and did not vary between seasons. In autumn, the wet weight of the contents of the RR ranged from 13% to 20% of body mass (BM) in females on NL and from 14% to 24% of BM in adult reindeer in winter. On NA, the wet weight of the contents of the RR in adult animals ranged from 15% to 20% of BM in summer and from 15% to 17% of BM in winter in NA. The ratio of the wet weight of the contents of the distal fermentation chamber (DFC) to the wet weight of the contents of the RR was 1:8 in females in autumn, compared to 1:6±1:7 in adult animals on NL in winter. The ratio of the wet weight of the DFC to the wet weight of the RR ranged between 1:8±1:10 in summer, compared to 1:7 and 1:8 in winter. There were no signi®cant differences in the size of plant particles in the RR contents in females from the two areas in any season, indicating that ruminal plant particle size was not in¯uenced by the concentration of plant cell walls in the rumen contents. We conclude that the degree of ®lling of the gastrointestinal tract of these reindeer was therefore principally a function of plant ®bre chemistry. Svalbard reindeer are adaptable intermediate feeders but they have, nevertheless, developed a large DFC similar to that of concentrate selectors.