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In vivo estimation of body composition from the dilution space
of deuterium oxide in fat-tailed Barbary ewes
a ,
*
b b c c´
Naziha Atti
, F. Bocquier , M. Theriez , G. Khaldi , C. Kayouli
a
Laboratoire de Recherche Ovine et Caprine, INRAT 2080 Ariana, Tunisia
b
´ `
Unite de Recherches sur les Herbivores, INRA Theix 63122 St. Genes Champanelle, France
c
´
Departement de Production Animale, INAT, Tunis, Tunisia
Received 6 May 1999; received in revised form 18 October 1999; accepted 30 November 1999
Abstract
Sixteen dry ewes of the fat-tailed Barbary breed were used to formulate prediction equations of body water, fat, protein and energy content from the live body weight (BW) and the dilution space of deuterium oxide (SD O). Ewes were injected2
with 0.5 g D O / kg BW and four blood samples collected after infusion. The D O content of blood water was determined by2 2 infra-red spectrometry. Ewes were weighed, body condition scored and then slaughtered. The body water, fat, protein, ash and energy were chemically determined. At slaughter, ewes weighed 43.467.0 kg, and contained 26.062.6 kg of water and 9.364.2 kg of fat. A relative lack of variation in the fat-free empty body (FFEB) was confirmed in this particular breed (water percentage, 74.561.6). Adiposity (fat as percent empty BW; EBW) varied between 15.1 and 36.9%. There was a
2
close negative relationship (R 50.96; residual standard deviation (R.S.D.)51.4%) between the fat and the water content of EBW. Body water was significantly correlated with SD O. The body fat and energy content prediction equations from SD O2 2
2
and BW were similar to those published in a thin-tailed ewe breed (R 50.92; R.S.D.51.4 kg). The body fat equation
2
prediction from body condition score and / or BW was significant (R 50.81; R.S.D.51.9 kg) although not as precise as that using D O.2 2000 Elsevier Science B.V. All rights reserved.
Keywords: Fat-tailed sheep; Body composition; Deuterium oxide; Body condition score
1. Introduction which then have to be restored during the more favourable season in order to be able to enter another During its production cycle, the ewe has to cope productive cycle. These reserves play a key role, with energy deficits caused by its physiological state especially in the southern Mediterranean area where or food shortage, often associated with the low feed resource availability is variable. To assess the quality of available food (dry season). In such role of body fat in these adaptations, changes in body situations, ewes have to mobilise their body reserves, composition must be monitored by in vivo methods. Methods for body composition estimation in the live animal are numerous. Among them, the measurement
*Corresponding author: Tel.: 1216-1-230-024; fax: 1
216-1-of the dilution space 216-1-of water tracers has proven to
752-897.
E-mail address: [email protected] (N. Atti) be one of the most reliable (Robelin, 1973, 1982;
Foot et al., 1979; Arnold and Trenkle, 1986; Russel intestines) were determined; the difference between and Reed, 1987; Schmidely et al., 1989). This is these latter weights representing gut content. The possible because the fat-free empty body (FFEB) empty BW (EBW) was calculated as the difference chemical composition is relatively constant (Moul- between SBW and gut content.
ton, 1923); body fat content is then calculated as the For each ewe, the dry matter content of three difference between live body weight (BW) and this blood and gut content samples was determined. mass. For thin-tailed ewes, in vivo prediction equa- Carcasses and all organs were minced and homogen-tions for body composition from BW and dilution ized, and then dried to determine water content. space of deuterium oxide (SD O) have been estab-2 Total body water (TBW) is the sum of blood, gut
´
lished (Tissier et al., 1983; Bocquier and Theriez, content, carcass and organ water. From the dried 1984; Sebastian, 1987; Bocquier et al., 1999) but, to samples, the ash content was determined after oven our knowledge, no results are available for fat-tailed heating at 6008C for 8 h, the N content by the ewes. Because of the specific adipose reserves of Kjeldhal method (protein5N36.25), and the these breeds (Atti and Bocquier, 1999), the goals of energy content using an adiabatic calorimeter. The this study were to establish in vivo prediction fat content was calculated by the difference between equations for Barbary sheep (fat-tailed; main ewe total energy content and the energy content of breed in Tunisia; Khaldi, 1989) and to characterise protein (5.5 kcal / g). The SD O was calculated as the2
the relationship between body condition score (BCS) ratio between the dose of D O infused and its2
and body fat content. theoretical concentration in blood water at the time
of infusion (Tissier et al., 1983).
For the establishment of relationships between
2. Material and methods body components (water, fat, protein, ash and energy) and SD O, data for the whole body were2
Sixteen dry ewes of the Barbary breed were used first used, and then data for the body without the tail for this study. They were chosen from experimental and its components for the establishment of relation-‘National Institute of Agricultural Research of ships between fat contents and SD O. The regression2
Tunisia’ (INRAT) flocks to give a wide range of equations of body fat, protein or energy on the ewes’ BCS. Ewes were kept at pasture (fat ewes) or fed SBW and water content, or on the ewes’ IBW and indoors with a limited amount of straw or hay in SD O were established using the SAS system2
(lean ewes). All ewes ate all water and food offered (1989). Furthermore, the regression equation of body during the blood collection period and until slaugh- fat on BCS and / or SBW was determined.
ter.
The BW of the ewes was measured 1 day before
infusion, at infusion (IBW) and just before slaughter 3. Results and discussion
(SBW), and the BCS in two anatomical regions
(lumbar, Russel et al., 1969; caudal, Atti, 1992) was 3.1. Body composition determined after slaughter measured before slaughter. The D O infusion (0.52
g / kg BW) took place between the hours of 09:00 The ewes’ mean BW6S.D. was 43.467.0 (Table and 10:00 through a catheter placed in the jugular 1), which is within the range (28–65 kg) of adult vein. Blood samples were collected 6, 8, 30 and 31 h ewe weights of the Barbary breed reported previous-after infusion in heparinized glass tubes. The day ly (Khaldi, 1989). Total body water represented after infusion, the ewes were sheared and slaughtered 49–69% of SBW (mean, 61%; Table 1). This range at 16:00. Blood samples were lyophilized and the in water content was slightly different to that of D O concentration in the resulting water was mea-2 thin-tailed ewes (45–74%, Tissier et al., 1983; 52– sured by infra-red spectrometry according to the 70%, Ligios et al., 1995). The water proportion in
method of Tissier et al. (1978). EBW was 56% with a range from 44 to 63%, which
Table 1 The mean6S.D. water proportion of FFEB was Weights of body components in the ewes 74.561.6%. This small variation confirms the first Mean6S.D. Min Max principle of body composition prediction by SD O2
(Moulton, 1923; Robelin, 1973, 1977), namely that
Infusion body weight (kg) 43.467.0 32.5 55.0
Slaughter body weight (kg) 43.166.4 32.5 55.0 the composition of the FEBW is practically constant.
Body weight without tail (kg) 40.865.7 31.3 52.5 This principle has been verified in numerous thin-Empty body weight (kg) 36.466.6 27.1 49.8 tailed breeds with values of 72 (Keenan and Total body water (kg) 26.062.6 21.8 29.7
McManus, 1969), 73 (Cowan et al., 1979), 74.8
Gut content of water (kg) 5.861.8 2.3 8.8
(Tissier et al., 1983), 74.1 (Castrillo et al., 1995) and
Total lipid (kg) 9.364.2 4.1 18.4
Lipid without tail (kg) 7.763.5 3.4 15.9 74.4% (Bocquier et al., 1999), which are close to the
Protein (kg) 5.360.8 4.3 7.2 value obtained in this study. Furthermore, the protein Ash (kg) 1.760.2 1.4 2.0 and ash contents in FFEB varied only slightly, the Energy (kcal) 121.8645.1 64.1 223.5
mean6S.D. being 19.361.6% and 6.160.76%, re-spectively (Table 2).
being in accordance with values reported in thin- All body component weights were closely corre-´
tailed ewes (23%, Bocquier and Theriez, 1984; 22%, lated with SBW (r5 10.73, 10.89, 10.77, Castrillo et al., 1995), while, logically, this per- 10.79 and 10.90 for water, fat, protein, ash and centage can be lower in fasted animals (down to energy, respectively). Considering TBW as a second
17%, Robelin, 1973). independent variable, the precision of fat and energy
The mean fat content was 9.3 kg; it varied estimation was significantly (P,0.01) improved between 4.1 and 18.1 kg. It represented 25% (15– (Table 3); residual variation coefficients (RVC) 37%) of EBW (Table 2). This result was similar to changed from 21.1 and 16.3% to 5.7 and 2.0%, values reported in the literature for thin-tailed breeds respectively. These results are comparable with those (25%, Tissier et al., 1983; 26%, Castrillo et al., reported in the literature (for lipid and energy, 1995), although the ranges can be very wide. In respectively, RVC56.5 and 6.1%, Tissier et al., those breeds, the lowest fat was 6 (Tissier et al., 1983; RVC56.5 and 5.2%, Baucells, 1988; RVC5
1983) or 7% (Ligios et al., 1995) of SBW, while in 3.9 and 5.3%, Castrillo et al., 1995). However, the these Barbary ewes, the leanest animals still con- precision of protein prediction was not improved tained 12.5% of fat in SBW. Furthermore, consider- (RVC510.2%), and its precision remained lower ing the body without the tail, the percentage fat in than that found by other authors (RVC55.7%, SBW varied between 9 and 30%, and body water Baucells, 1988; RVC54.8%, Castrillo et al., 1995). content between 51 and 72%; these values were
closer to those observed in thin-tailed ewes. Hence, 3.2. Relationship between lipid and water content the high adiposity of the Barbary ewe is partially due
to its fat tail. The protein and ash contents were 5.3 The ratios of fat and water in SBW were sig-and 1.7 kg, representing 15 sig-and 5% of EBW, nificantly (P,0.001) and negatively correlated
2
respectively (Table 2). (R 50.96; Fig. 1). The linear regression of fat on
Table 2
Chemical composition of empty body weight (EBW) and fat-free empty body (FFEB)
EBW FFEB
Mean6S.D. Min–max Mean6S.D. Min–max
Water (%) 56.3365.41 44.5–63.5 74.5461.58 70.5–76.1
Lipid (%) 24.4666.75 15.1–36.9 – –
Proteins (%) 14.5861.49 11.4–16.6 19.3461.62 17.3–23.0
Ash (%) 4.6360.59 3.7–5.5 6.1360.46 5.3–7.1
Table 3
a
Prediction equations of body components from slaughter body weight (SBW, kg) and total body water (TBW, kg)
2
Regression coefficient (mean6S.D.) Intercept R.S.D. RVC (%) R
SBW TBW
Lipid (kg) 0.581 (60.082) 215.58 1.96 21.1 0.79
Lipid (kg) 0.882 (60.032) 21.021 (60.078) 22.07 0.53 5.7 0.99
Protein (kg) 0.100 (60.023) 10.95 0.55 10.4 0.60
Protein (kg) 0.129 (60.033) 20.098 (60.080) 12.26 0.54 10.2 0.64
Energy (Mcal) 6.011 (60.800) 2142.1 18.96 16.3 0.82
Energy (Mcal) 9.005 (60.139) 210.14 (60.342) 26.9 2.29 1.97 0.99
a
All regressions highly significant (P,0.001).
3.3. Prediction of body water content from the
space dilution of deuterium oxide
There was a significant correlation (P,0.01) between TBW and SD O (r2 50.91; Fig. 2). The linear regression of TBW on SD O was defined by2
the following equation:
TBW (kg)50.954 (60.119) SD O (kg)2 10.955
2
R 50.833 R.S.D.5 61.05 kg RVC54.2%
The low values of R.S.D. and RVC demonstrate a high precision of estimation for this equation.
How-2
Fig. 1. Relationship between proportions of water and lipid in ever, R was less than values obtained in the
2 2
body weight at slaughter. literature (R 50.939, Tissier et al., 1983; R 50.964, 2
Baucells et al., 1989; R 50.931, Castrillo et al.,
2
water (both expressed as %SBW) was defined by the 1995; R 50.94, Ligios et al., 1995). In our study,
following equation: the inclusion of the difference in ewe BW between
Fat (%SBW)5 21.12960.06 TBW (%SBW)
189.889
2
R 50.96 Residual S.D. (R.S.D.)
5 61.3% RVC56.24%
The linear regressions of fat on body water content in SBW or in EBW were similar (R.S.D.51.3 and 1.4%, respectively). They were similar to those established for thin-tailed ewes for SBW ratio (R.S.D.51.4%, Tissier et al., 1983) or for EBW
(R.S.D.51.1%, Baucells, 1988; R.S.D.52.0%, Cas- Fig. 2. Relationship between total body water (TBW, kg) and
infusion and slaughter did not improve the precision components. However, the correlation coefficient
2
of the equation (R 50.835). However, the constant between SD O and body water without the tail was2
term (0.95 kg) in this Barbary equation was clearly slightly greater than that with TBW (0.92 and 0.91, lower than corresponding constants found by other respectively; P,0.05). So, the prediction of water authors (4.42 kg, Tissier et al., 1983; 6.34 kg, content without the tail from SD O, or SD O2 2
´
Bocquier and Theriez, 1984; 2.15 kg, Castrillo et al., adjusted for the difference between SBW and IBW 1995) who found that SD O overestimated TBW, a2 were more precise than those for TBW:
finding not confirmed in this study.
Body water2tail water (kg)
50.946 (60.111) SD O (kg)2 10.710 3.4. Prediction of body components from the space
dilution of deuterium oxide
2
R 50.846 R.S.D.5 60.988 kg RVC54.1% Fat, protein, ash and energy prediction equations
Body water2tail water (kg) from IBW and SD O are reported in Table 4. These2
equations were significant (P,0.05), relatively 50.961 (60.111) SD O
2
accurate for fat and energy, and less accurate for
20.146 (60.328) BW change10.371 protein. They are similar to those already published
for thin-tailed ewes (Tissier et al., 1983; Bocquier 2
R 50.862 R.S.D.5 60.976 kg RVC54.0% ´
and Theriez, 1984; Baucells, 1988; Castrillo et al., 1995; Ligios et al., 1995). For lipid, regression
3.6. Relationship between body fat and body coefficients (a andb) of independent variables (i.e.,
condition score
IBW, SD O) are almost identical (0.76 and 0.77), a2
result in accordance with other studies (0.854 and
The amount of lipid was closely and significantly ´
0.827, Bocquier and Theriez, 1984; 0.9 and 1.0,
(P,0.001) correlated with both BCS, the relation-Castrillo et al., 1995; 0.81 and 0.83, Ligios et al.,
ship with the caudal BCS (r5 10.868) being better 1995).
than that with the lumbar BCS (r5 10.773). How-ever, BCS and BW make it possible to predict fat 3.5. Importance of the fat-tail in prediction of
content, the better prediction being observed with
body composition
BW and caudal BCS: The weight of the tail of these Barbary ewes Lipid (kg)5 211.998 varied from 1.17 to 3.53 kg and was essentially
10.4236(0.197) SBW (kg) composed of fat (25–92%) with a low water content
11.052 (61.198) caudal BCS (20%), and a negligible proportion of protein (3%).
Considering the ewe without the tail, body fat
2
R 50.807 R.S.D.5 61.98 kg RVC521.3% (without tail fat) was estimated from SBW and water
content (without tail water) with a similar precision
2
(R 50.98) to that obtained using the total body These equations were less accurate than those
Table 4
a
Prediction equations of body components from infusion body weight (IBW, kg) and dilution space of deuterium oxide (SD O, kg)2 2
Regression coefficient (mean6S.D.) Intercept R.S.D. RVC (%) R
IBW SD O2
Lipid (kg) 0.762 (60.071) 20.77 (60.212) 23.90 1.4 14.1 0.92
Protein (kg) 0.135 (60.03) 20.131 (60.087) 12.99 0.6 10.2 0.68 Energy (Mcal) 7.931 (60.643) 28.022 (61.910) 221.85 12.6 10.3 0.94
a
2 total body fat in Barbary breed ewes]. Options Med. Ser.´ ´
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´
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that this method (BCS) is sufficient for lipid predic- to underfeeding and re-feeding periods: effects on adipose tion (Russel et al., 1969; Sanson et al., 1993) or tissues]. Ann. Zootech. 48, 189–198.
Baucells M., 1988. [Body composition estimation with the
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tail, which is mainly composed of lipids. We have
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´ ´ ´
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´ ´ ´
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