Estimating body composition of caribou and reindeer using bioelectri-cal impedance analysis and body condition scores

The use of non-destructive methods to assess body composit ion of w i l d cervids allows clarification of the dynamic influence of the environment on nutrient reserves w h i c h , in turn , affect reproductive success. Bo th bioelectrical impedance analysis (BIA) and body condit ion scores (BCS) have been used elsewhere to estimate in vivo body composit ion. B I A relies on the differential conductivity of lean and fatty tissues, while B C S are numerical indices of overall condit ion. This is a prel iminary report on the efficacy of B I A and B C S as predictors of fat content ( F A T ) and total body water ( T B W ) . N i n e captive male reindeer and 10 w i l d female caribou of the Central A r c t i c H e r d ( C A H ) were used in this analysis. A n additional 5 female caribou of the C A H were rated using B C S only . Each animal was weighed ( B W , nearest kg), and body measurements (body length, L , chest girth, G , metatarsal length, M T , all in cm) were taken. W h o l e body resistance (Z) was determined using a bioelectrical impedance analyzer (BIA-101A, R J L Systems, Inc., Detroi t MI) and 2 pairs of electrodes w h i c h were inserted under the skin at each of 2 sites (Fig. 1): on the legs w i t h the animal ly ing on its side (Z j J , and along the back w i t h the animal ly ing on its chest (Zt>). B C S was determined as the sum of numerical rating (1-5, 1 being low) of the amount of soft tissue covering bone at each of 3 sites: withers, ribs, and hips. A body reserve index (BRI) was computed as the product of B C S and body weight. A l l animals were k i l led and processed for chemical analysis (Huot and Picard 1988). Water content was determined by freeze drying; fat content was determined by petroleum ether extraction. Stepwise linear regression was used to examine relationships between dependent ( T B W , l i ters, and F A T , kg) and independent variables (BCS, B W , B R I , M T , L , G , 1 / Z B , 1 / Z L , ( M T or L ) 2 / Z L or Z ^ ) . Impedance values were expressed as ( l eng th )VZ, since body water volume is theoretically related to conductor length squared divided by resistance. Corre la t ion between T B W and body weight (eq. 1) was stronger than that between T B W and any impedance term. Impedance expressed as L V Z L was most strongly correlated w i t h T B W (eq. 2). T B W was not correlated w i t h Z ^ .


Rangifer, 12 (3): 185-186
The use of non-destructive methods to assess body composition of wild cervids allows clarification of the dynamic influence of the environment on nutrient reserves which, in turn, affect reproductive success.Both bioelectrical impedance analysis (BIA) and body condition scores (BCS) have been used elsewhere to estimate in vivo body composition.BIA relies on the differential conductivity of lean and fatty tissues, while BCS are numerical indices of overall condition.This is a preliminary report on the efficacy of BIA and BCS as predictors of fat content (FAT) and total body water (TBW).
Nine captive male reindeer and 10 wild female caribou of the Central Arctic Herd (CAH) were used in this analysis.An additional 5 female caribou of the CAH were rated using BCS only.Each animal was weighed (BW, nearest kg), and body measurements (body length, L, chest girth, G, metatarsal length, MT, all in cm) were taken.Whole body resistance (Z) was determined using a bioelectrical impedance analyzer (BIA-101A, RJL Systems, Inc., Detroit MI) and 2 pairs of electrodes which were inserted under the skin at each of 2 sites (Fig. 1): on the legs with the animal lying on its side (ZjJ, and along the back with the animal lying on its chest (Zt>).BCS was determined as the sum of numerical rating (1-5, 1 being low) of the amount of soft tissue covering bone at each of 3 sites: withers, ribs, and hips.A body reserve index (BRI) was computed as the product of BCS and body weight.All animals were killed and processed for chemical analysis (Huot and Picard 1988).Water content was determined by freeze drying; fat content was determined by petroleum ether extraction.
Stepwise linear regression was used to examine relationships between dependent (TBW, liters, and FAT, kg) and independent variables (BCS, BW, BRI, MT, L, G, 1/ZB, 1/ZL, (MT or L) 2 /ZL or Z^).Impedance values were expressed as (length)VZ, since body water volume is theoretically related to conductor length squared divided by resistance.
Correlation between TBW and body weight (eq. 1) was stronger than that between TBW and any impedance term.Impedance expressed as LVZL was most strongly correlated with TBW (eq.2).TBW was not correlated with Z^.

Figure 1 .
Figure1.Placement of electrodes for bioelectrical impedance analysis.Impedance was determined in 2 positions: With a pair of electrodes on the front and hind leg and the animal lying on its side (Z\), or with a pair of electrodes at 2 sites along the back and the animal lying on its chest (Zb)