Water requirements of captive reindeer hinds with artificial feeding

Abstract

Winter (February to April) water re­ quirements of 40 reindeer (Rangifer tarandus ta- randus L) were studied at the Kaamanen Re­ search Station (69°10'N) (Soppela et al 1987). In 1985 28 hinds were divided into four groups and fed with equal rations of (I) lichens (Cladi- na spp.) with 3% crude protein (CP): (II) li­ chens and dry hay (Phleum pratense) with 12% CP, (III) pelleted reindeer feed with medium (12%) CP and (IV) pelleted feed with high (17%) CP. The study was done with 12 hinds (feeding I and II) in 1986. The hinds were kept in outdoor enclosures, where clean snow was available ad libitum for free water intake. The animals were weighed monthly. Total body wa­ ter (TBW) and daily water turnover (WTR) was measured by the tritiated water method (Holle- man et al 1982). Total body fat (TBF) was cal­ culated from TBW according to Pace and Rathbun (1945). Drinking water intake was measured indirectly by subtracting the intake of feed water and metabolic water from the daily water influx or WTR. The amount of energy re­ quired to melt and warm the drinking water to body temperature (39°C) was calculated from the specific heat values of water, snow or ice at different ambient temperatures. Total body water remained unchanged (mean TBW 68.8±0.7%) in each group from February to March. Body weight decreased in all groups except for hinds fed with high protein feed (Group IV). Total body fat decreased from 6.9 to 3.0% in hinds fed with hay and lichens from February to March (P<0.05). Mean TBW in- April. In April, hinds fed with lichens (Group I) weighed less and had a higher TBW (74.6 to 68.8%) than hinds fed with medium protein feed (Group III) (P<0.01), whereas their (Gro­ up I) TBF was smaller (0.3 to 6.1%, P<0.01). The mean daily water turnover was smaller in February in hinds fed with lichens (Group I) or with hay and lichens (Group II) than other gro­ ups of hinds. The mean daily WTR remained unchanged from February to March in Group I hinds but increased in the others. The mean dai­ ly WTR in Group I increased slightly from March to April, but was still smaller than in other groups. There was a strong positive corre­ lation between the intake of digestible CP and WTR (r=0.738, n=35, P<0.001). Daily drinking water intake was smallest (P<0.001) in the lichen-fed hinds (Group I) throughout the feeding period. It was rather constant in this group, while it increased in other groups from February to March. The li­ chen group drank 0.11/day in March. Groups II, III and IV drank 2.0, 3.2 and 3.5 1/day respecti­ vely. In April drinking water intake was smaller in Group I than in Group III (0.1 and 3.7 1/day resectively) (P<0.001). The energy costs of melting and warming drinking water were smal­ lest in the lichen-fed hinds in each month during the trial (mean 0.1 MJ/day), while hinds fed with pelleted feeds had the largest energy costs. Hinds fed with hay and lichens (Group II) had energy costs of 0.5 MJ/day in February and 1.2 MJ/day in March. The energy costs of hinds fed