Forage chemistry and fermentation chambers in Svalbard reindeer (Rangifer tarandus platyrhynchus)

Seasonal changes in the species composition and fibre content of plant frag ments in the rumen and the gross anatomy of the gastrointestinal tract were investigated in Svalbard reindeer Rangifer tarandus platyrhynchus in weste rn parts of Spitsbergen (Nordenskiold Land (NL), 78 degrees N), where the t undra vegetation is relatively abundant, and on the island of Nordaustlande t ((NA) 81 degrees N) where, in the polar desert, plants are scarce. Reinde er 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 includ ed 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 matte r 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 au tumn, the wet weight of the contents of the RR ranged from 13% to 20% of bo dy mass (BM) in females on NL and from 14% to 24% of BM in adult reindeer i n 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 fermentati on chamber (DFC) to the wet weight of the contents of the RR was 1:8 in fem ales in autumn, compared to 1:6-1:7 in adult animals on NL in winter. The r atio of the wet weight of the DFC to the wet weight of the RR ranged betwee n 1:8-1:10 in summer, compared to 1:7 and 1:8 in winter. There were no sign ificant differences in the size of plant particles in the RR contents in fe males from the two areas in any season, indicating that ruminal plant parti cle size was not influenced by the concentration of plant cell walls in the rumen contents. We conclude that the degree of filling of the gastrointest inal tract of these reindeer was therefore principally a function of plant fibre chemistry. Svalbard reindeer are adaptable intermediate feeders but t hey have, nevertheless, developed a large DFC similar to that of concentrat e selectors.