Citation of this paper |
Body condition scoring (BCS) is a simple and easy technique, which allows
subjective assessment of an animal’s body composition to help in adopting
appropriate management strategy. Information on BCS is not available for
indigenous Tswana goats. The aims of this study were to establish the
relationships among body weight, body condition score and heart girth in
indigenous Tswana goats raised under extensive and
semi-intensive management during the dry and wet seasons in southeast
Season significantly affected BCS, with lower scores (2.17±0.10 to 2.65±0.10) in the dry season than in the wet season (3.17±0.10 to 3.79±0.11), but has no effect on body weight or heart girth. Management did not significantly affect body condition score. There was no apparent relationship between body weight and condition score. Body weight was closely correlated with heart girth under extensive management in the wet season but not in the dry season.
It is concluded that BCS is a more useful indicator of seasonal nutritional effects in goats than body weight or heart girth.
The importance of goats in the livelihood of rural African people cannot
be over emphasized (Aganga and Moganetsi 1998). They play a pivotal role in the rural economy as a source of employment, food
and income generation (APRU 1994), especially to small scale farmers who may
only own this livestock species. In
BCS is a subjective measure of nutrient reserve. It is a useful description of animals based on a simple functional indicator closely associated with the body composition (Rae 2002). Research has indicated a strong link between body condition and weight change; thus as the body condition score increases, weight also increases whereas when body condition decreases, weight also decreases. According to the study of Mellado et al (1996), infertility increased in both bucks and does as body condition score decreased. Information on BCS in indigenous Tswana goats is not available. Therefore, the aims of this study were to establish the relationship between:
· Body weight and body condition score
·
Body weight and
heart girth in indigenous Tswana goats raised under extensive and
semi-intensive management during the wet and dry seasons in southeast
A total of 10 randomly chosen farms were involved in this study. Five
farms were from Kweneng district while the other five were from Kgatleng
district. These two districts form part of southeast
Data were collected over a period of 4-months for the wet (mid September
– mid February) and dry (mid May – mid September) seasons. Goats were
extensively managed with little supplementation and minimal medical care. Goats
were let out to graze natural pasture categorised as
hard-veld between
Body weight, heart girth and body condition score (BCS) for each goat were recorded fortnightly at 08:00h each time after over
night kraaling. Body weight was measured using a commercial hanging scale,
while a weighing band was used to measure heart girth. BCS was assessed using
the 5 point scale (1=very thin to 5=obese) following among others Aumount
et al (1994) and Thompson and Meyer
(2002). Animals were visually assessed followed by palpation of the lumbar
vertebrae area between the back of the ribs and the front of the pelvic bones.
Two experienced persons carried out the assessment with average scores taken to
avoid biasness since the exercise is subjective.
This experiment was carried out at Botswana College of Agriculture farm,
which is also in southeast
The goats were subjected to semi-intensive management with regular
supplementation and adequate medical care. During the
day the goats were let out to graze natural pasture from
The measurements recorded and the frequency of data collection were
similar to those in Experiment 1.
The data were analysed using General Linear Model (GLM) and Correlation procedures (SAS 1999-2000). GLM was used because a few animals either died or were missing during data collection for both experiments and one farmer in Experiment 1 relocated to an unknown place in Kgatleng towards the end of the experiment. Seasons were defined as follows: wet (September, October, November, December, January and February) and dry (May, June, July and August). Due to lack of significant difference (P>0.05) between districts and sexes within a season data were pooled for analyses. Least squares means were separated using a t-test. The results reported are based on least squares means.
Season affected (P<0.05) mean body condition score and in some cases mean body weight and heart girth. The body condition score was significantly higher during the wet than during the dry season. Generally, sex had no significant effect on all measurements recorded (Table 1). The body condition scores during the wet season were significantly higher than those of the dry season. Cissé et al (2002) also report this phenomenon where goats lose body condition in the dry season and gain it during the wet season. As pointed out by Luginbuhl et al (2002) and Rae (2002), this allows body condition scores to be used as a management tool in farm animals since it is so sensitive to seasonal changes.
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Table 1: Mean values (with SE) for effect of season and sex on body condition score, body weight and heart girth of indigenous Tswana goats in Kweneng, Kgatleng districts and Botswana College of Agriculture (BCA) |
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Body condition score |
Body weight (kg) |
Heart girth (cm) |
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|
|
Kweneng |
Kgatleng |
BCA |
Kweneng |
Kgatleng |
BCA |
Kweneng |
Kgatleng |
BCA |
|
|
SEX: Females Males |
2.78±0.03 2.80±0.03 |
2.95±0.06 2.98±0.06 |
2.41±0.03 2.54±0.04 |
20.1±0.35 20.0±0.35 |
18.0±0.38a 19.8±0.38b |
28.7±0.37 29.2±0.44 |
65.2±0.38 64.0±0.39 |
60.5±0.46 62.8±0.46 |
70.8±0.30 70.9±0.36 |
|
|
SEASON: Dry Wet |
2.31±0.03a 3.26±0.03b |
2.50±0.07a 3.43±0.06b |
2.47±0.03 # |
18.5±0.38a 21.6±0.33b |
18.6±0.43 19.3±0.36 |
29.0±0.29 # |
64.9±0.42 64.4±0.36 |
62.7±0.51a 60.6±0.43b |
70.8±0.23 # |
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# indicates an empty sub-class ab Means with different letters within a trait in a column are different at P<0.05 |
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There are no reports available on body condition scoring in Tswana goats. However, the results of the present studies indicate that the goats were in thin to slightly above average score using the 5-point scale of Thompson and Meyer (2002). According to these authors and Luginbuhl et al (2002) such body condition scores are generally ideal for production hence farmers should be assured that their use as a management tool will lead to more productive goats, which are neither fat (body condition score of 4-5) nor emaciated (body condition score of 1). Over-fat does are susceptible to pregnancy toxemia, while emaciated does are extremely weak and may be near death (Luginbuhl et al 2002). Both situations lead to loss in production. Measurements for body weight and heart girth were within literature estimates reported elsewhere for indigenous Tswana goats (Owen et al 1977; Katongole et al 1996); however, there were no consistent effects of sex or season on live weight or heart girth.
Correlation coefficients between body weight and body condition score were moderate and negative; -0.54 and –0.40 in the dry and wet seasons, respectively. It was thus to be expected that attempts to predict body weight based only on body condition score would be of little value (Table 2).
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Table 2: Prediction equations during the dry and wet seasons for indigenous Tswana goats in southeast Botswana |
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Extensive management (on-farm) |
Semi-intensive management (on-station) |
|
|
Dry season |
Wet season |
Dry season |
|
LW=4.79+0.21HG; R2 = 0.04 |
LW=-11.17+0.50HG; R2 = 0.85 |
LW=-181+2.97HG ; R2 = 0.74 |
|
LW=22.3-1.70BCS; R2 = 0.29 |
LW=33.1-3.76BCS; R2 = 0.17 |
LW=3.2+10.5BCS; R2 = 0.17 |
|
LW=-7.23+0.49HG-2.23BCS;R2 = 0.47 |
LW=-8.50+0.49HG-0.56BCS; R2 = 0.85 |
LW=-192+7.99HG+2.84BCS; R2 = 0.84 |
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BCS, HG and LW are abbreviations for body condition score, heart girth and body weight respectively |
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Cissé et al. (2002) report similar results, where changes in body weight in Senegalese Sahel goats did not always parallel body condition scores. These authors attributed this phenomenon to the fact that body condition score reflects body lipids more than body weight, as the latter is affected by gut contents which vary according to the type and quantity of feed available. In support of this statement is the fact that dressing percentages in the Tswana breed ranged from 36 to 42% during the dry season, according to Mannathoko (2002), compared with 42 to 48% during the wet season (Tadubana 2002).
The prediction equations for live weight based on heart girth were good during the wet season and in the dry season with semi-intensive management, but very poor during the dry season under extensive management. This general finding is consistent with those of Mayaka et al (1995), Benyi (1997) and Badi et al (2002), who reported predominantly high coefficients of determination (R2 = 0.80 to 0.99) in different breeds of goats. In agreement with these authors, estimating body weight from heart girth is appropriate and practical in rural areas where resources are poor.
Predicting body weight from both condition score and heart girth
appeared to be satisfactory, but there were inconsistencies in this relationship
as shown by negative terms for body condition under extensive management in dry
and wet seasons, and a positive term with semi-intensive management in the dry
season.
Body condition score appeared to be a more useful trait than body weight or heart girth for assessing nutritional consequences of the dry versus the wet season under conditions of extensive management. It was not a good predictor of body weight irrespective of season and management system.
Body weight and heart girth, although reasonably well correlated, were
not apparently sensitive to effects of season.
The authors
express sincere gratitude to all farmers whose Tswana goats were used in this
study. The authors thank Botswana
College of Agriculture for providing funds for this study and Ms B Mompati and
Mr K Magaise for data collection.
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Received 27 November 2002; Accepted 15 December 2002