FOOD-INTAKE, DIGESTIBILITY AND RUMEN FERMENTATION IN REINDEER FED BALED TIMOTHY SILAGE IN SUMMER AND WINTER

Reindeer calves (Rangifer tarandus tarandus) were used in parallel fee ding trials with two different qualities of round-bale timothy silage in September 1992 (summer) and April 1993 (winter) in northern Norway, to determine the effect of season on their food intake and ability to utilize silage of different fibre contents. The silages were prepared from first-cut (FC) and regrowth (RG) timothy. The FC silage containe d (on a dry matter (DM) basis) 12.3% crude protein, 30.4% cellulose an d 6.2% water soluble carbohydrates (WSC), whereas the RG silage contai ned 14.3% crude protein, 18.7% cellulose and 30.0% WSC. For each trial , six male calves were taken directly from a natural range and divided into two groups of three animals. One group was offered FC silage and one RG silage ad libitum, for 46 days. Mean daily DM food intake (g/k g liveweight) was not significantly different in summer compared to wi nter (P > 0.05), but significantly higher in the animals fed RG silage compared to the animals fed FC silage (P < 0.0001). The apparent dige stibility coefficient of DM was high for both silages both in summer a nd winter, ranging from 74.4 to 86.6%. However, the digestibility in w inter was significantly higher than in summer (P < 0.002) and the dige stibility of RG silage was higher than that of the FC silage (P < 0.00 9). The ruminal VFA concentration was significantly higher in winter t han in summer (P < 0.03) and in the animals fed RG silage (range 55.3- 104.9 mM) compared to the animals fed FC silage (range 35.2-61.7 mM) ( P < 0.002). In spite of the high digestibility of both the FC and RG s ilages, the nitrogen balance was significantly higher in the animals i n winter compared to summer (P < 0.0001) and in the animals fed RG sil age compared to the animals fed FC silage (P < 0.0001). Thus, utilizat ion of grass silage in reindeer appears to be influenced both by seaso n and by plant quality.