Short communication
Live weight and body condition changes of matebele does during
their breeding cycle in a semi-arid environment
L. Majele-Sibanda
a, M.J. Bryant
b, L.R. Ndlovu
c,*aLinds Agricultural Services, PO Box MP 546, Mount Pleasant, Harare, Zimbabwe bDepartment of Agriculture, University of Reading, Earley Gate, Reading RG6 2AT, UK
cDepartment of Animal Science, University of Zimbabwe, PO Box MP 167, Mount Pleasant, Harare, Zimbabwe
Accepted 29 June 1999
Abstract
The live weights of Matebele does kept in seven communally grazed ¯ocks in southern Zimbabwe were established by survey over a two-year period. The does showed a cyclical change in weight around the breeding cycle, the mean live weight at mating, immediately after kidding and 60 days after kidding were 30.0, 35.2 and 32.8 kg, respectively. The month of mating and kidding had a major effect on live weight. The post-kidding weight of does kidding in the late-dry to early-wet season was approximately 25% less than that of does kidding at the end of the wet season. Does mating during the wet season had the greatest gains over the course of the breeding cycle. The mean mating weight of primiparous does was 24.0 kg, approximately two-third that of adult does. Younger does tended to gain more weight over the course of the breeding cycle than older does. There were consistent differences in live weight among ¯ocks. The results illustrate the profound effects of seasonal factors on live weight changes and the abilities of Matabele goats to adapt to their harsh environment.#2000 Elsevier Science B.V. All rights reserved.
Keywords:Matebele goats; Live weight; Semi-arid; Traditional management
1. Introduction
It is generally acknowledged that live weight and body condition are intimately connected to the pro-ductivity of domestic ruminants (Robinson, 1990). Cycles of production frequently involve animals stor-ing surplus energy in the form of body fat in times of
dietary suf®ciency. These reserves are then catabo-lized when dietary energy intake is inadequate to match the demands of production. Furthermore, there is good reason to believe that feedback occurs among dietary energy intake, body energy stores and repro-ductive rate (Lamond, 1970) such that frequency of breeding and litter size re¯ect the nutritional status of the dam.
Matebele goats and the related goat breeds of southern Africa frequently inhabit arid and semi-arid environments where there are marked seasonal con-trasts in the availability of nutrients. Observations on
*Corresponding author. Department of Animal Production,
University of The North, Private Bag X 1106, Sovenga, South Africa 0727. Tel.:27-15-268-2186; fax:27-15-268-2892.
E-mail address: [email protected] (L.R. Ndlovu).
the productivity of the Matebele goat have linked live weight and body condition score of the doe to kidding interval and litter size (Sibanda, 1992). A quantitative assessment of the effects of non-genetic factors that in¯uence the changes in live weight and body condi-tion of goats in harsh environments is important to efforts aimed at improving their productivity. This paper presents an analysis of records of doe live weight collected in a two-year survey of goat herds kept under traditional management in a communal area of southern Zimbabwe.
2. Materials and methods
The survey was carried out over a two-year period in the Guyu communal area of the Gwanda district of southern Matebeleland, south-west Zimbabwe (long-itude 288590
E, 218230
S). The area is approximately 765 m above sea level. There are two distinct seasons, a cold, dry winter (May±August) and a hot summer (September±February) when temperatures average 298C. The rainy season usually begins in November and lasts until April. The annual rainfall varies between 300 and 500 mm. The climate renders inten-sive cropping impossible and the main agricultural enterprise of the region is livestock rearing. The cattle, sheep and goats of the area are entirely dependent on natural vegetation, which is predominantly mopane (Colophospermum mopane) tree savanna woodland. The livestock are individually owned and are kraaled at family homesteads overnight. During the day they are left to range freely, unattended, over the com-munally-shared range land. Since the sexes intermin-gle throughout the year there is no control over breeding activity and kids were born in all months. The goats are mainly kept as a source of cash through sales and occasionally, as a source of protein through home slaughters.
The survey began in the ®rst week of July, 1989, when the goats belonging to seven families were ear tagged and their individual ages determined from the number of permanent incisor teeth (Wilson and Dur-kin, 1984). Each goat was weighed to the nearest 0.25 kg using a mobile cage scale once every 2 weeks and the weights averaged to give a monthly weight. The animals were body condition scored using a 10 point scale (Sibanda, 1992) which was adapted from
the method of Honhold et al. (1989). Fixed effects due to kidding (mating month in the case of live weight at mating), farmer, age of doe and kidding (mating) year and residual error were included in the general statis-tical model. Least squares procedures were used to analyse data on the live weight and body condition scores (BCSs) of the does at mating (interpolated as 150 days before kidding), immediately and 60 days after kidding (SAS, 1990). Birth type (i.e. single or multiple kids) was also included in the models for live weight post-kidding and 60 days post-kidding.
3. Results
The interactions among all main effects were not statistically signi®cant and thus results are reported for main effects only. Month of kidding (mating) had signi®cant effects on all three live weights (Table 1) and body condition scores (Table 2). Monthly live weights began to increase at the start of the rains and generally continued to increase until the early dry period when they declined rapidly. The 60-day post-kidding weights varied from 35.3 kg in May to 26.9 kg in September. Does kidding in May gained approximately 28% more weight and approximately one BCS unit between mating and immediately post-kidding whilst on average the does post-kidding in July±November lost weight and condition during this period.
Year of parturition had a signi®cant effect on BCS at kidding and on BCS change during lactation (Table 2). There were differences among farmers for all three doe live weights and BCSs (P< 0.01; Tables 1 and 2). There was also some consistency in these differences. Farmer D's does, for example, were the lowest in the ranking at each point of the reproductive cycle. Farmer G's does, on the other hand, were always high in the rank order.
4. Discussion
The does showed a cyclical change in weight and condition around the production cycle. Although the pattern of change varied, a ``typical'' doe gained substantial amounts of weight during pregnancy and lost some of that weight in early lactation, making a small net gain over the cycle. The peak of the cycle was at kidding and hence this implies that manage-ment strategies for goats should differ from
recom-mendations for managing weight change in sheep indigenous to temperate climates whose weight cycle peaks during gestation (Robinson, 1990). However, this pattern was modi®ed to a considerable extent by month of kidding. The post-kidding weight of does kidding in the late-dry to early-wet season months was approximately 25% lighter than that for does, equiva-lent in all other respects, that kidded at the end of the wet season months. These large variations seem to be exceptional. Ruvuna et al. (1991), working with Small Table 1
Least squares means and standard errors of the live weights (kg) of does at mating, post-kidding and 60 days post-kidding
Source Live weight
At mating Post-kidding 60-day Post-kidding %Change post-kidding
Does 313 438 439 438
MeanS.E. 30.00.21 35.20.24 32.90.29 ÿ6.5
Month of mating
January 28.1** 32.6** 34.9** 7.1
February 29.8** 33.1** 34.1** 3.2
March 31.7** 34.7** 34.0** ÿ1.5
April 34.7** 36.7** 34.4** ÿ6.1
May 29.2** 37.3** 35.3** ÿ2.2
June ± 39.7** 34.6** ÿ12.7
July 34.0** 33.7** 29.4** ÿ13.4
August 33.9** 32.4** 28.9** ÿ10.8
September 30.8** 30.3** 26.9** ÿ11.2
October 26.0** 27.5** 27.4** ÿ0.4
November 24.9** 23.9** 27.9** 16.7
December 25.8** 30.9** 29.6** ÿ4.2
S.E. 1.26 1.40 1.35
Farmer
A 27.3** 29.3** 29.5** 0.7
B 32.1** 34.1** 31.8** ÿ6.7
C 30.8** 33.7** 32.7** ÿ3.0
D 27.2** 28.2** 29.0** 2.8
E 28.4** 31.5** 31.1** ÿ1.3
F 31.4** 33.3** 33.0** ÿ0.9
G 32.0** 33.7** 33.1** ÿ1.8
S.E. 0.76 0.88 0.83
Doe age (years)
>4 36.4** 38.4** 36.8** ÿ4.2
4 32.3** 33.9** 33.5** ÿ1.2
3 27.0** 28.1** 28.6** 1.8
2 24.0** 27.4** 26.9** ÿ1.8
S.E. 0.72 0.75 0.75
Birth type
Single NSa 31.3* 30.8* ÿ1.6
Twins NSa 32.7* 32.1* ÿ1.8
S.E. NS 0.62 0.63
East African and Galla goats that were grazed on station rangelands in Kenya, reported maximum sea-sonal losses of 8% of live weight. Wilson (1987) quoted seasonal variations in weight of 1.8±2.3 kg for does in central Mali, approximately 10% of their live weight. Goats belonging to the nomadic Turkana,
inhabiting the arid region of north-western Kenya (annual precipitation <350 mm), had seasonal weight changes of 18% of live weight (Coppock et al., 1986). Relative seasonal differences in nutritional resources among the various environments could account for such differences in weight loss. The strategy adopted by nomads is to follow feed resources to reduce the impact of seasonal insuf®ciencies on their livestock. Animals kept by sedentary agro-pastoralists do not have this advantage.
It is also possible that the ability to withstand seasonal extremes may be in part a genetic or adaptive animal characteristic. Bajhau and Kennedy (1990) found that feral goats in Australia could lose up to 21% of their live weight during gestation, compared to only 13% for cross-bred goats. The possible adapta-tion of African indigenous livestock breeds to con-tinual exposure to what can only be described as periods of starvation is currently receiving increased attention as a possible sustainable paradigm for the improvement of smallholder livestock systems (ILRI, 1995). Our results suggest that the Matebele goat has adapted to the nutritional ¯uctuations it is subjected to. The farmer effect is of some interest. Since the ¯ocks were not spatially dispersed over a large land-scape and the does grazed communal rangelands, it seems that differences among farmers may be as a result of interventions on the part of the individual farmers. The interventions could include early release of goats from con®nement, supplementation with Acacia tree pods which are abundant in the area or provision of better shelter during inclement weather. However, as these were not recorded in the study it is dif®cult to surmise which are responsible for the differences. Information on the ``typical'' manage-ment system was acquired from group interviews held at the beginning of the survey. Some follow-up farmer participatory appraisal is necessary to establish pos-sible differences in management among the farmers. The post-kidding weight of does above four years of age should be a good indicator of the mature weight of Matebele does. According to Fitzhugh and Taylor (1971), simply de®ning the mature weight as the weight eventually reached is inappropriate for a char-acter like live weight which may change either posi-tively or negaposi-tively with time, depending on environmental conditions. To reduce the environmen-tal variation on weight, they averaged repeated Table 2
Least square means of body condition scores of does at kidding and net score changes during pregnancy and lactation
weights. The same procedure was used in this study, where the mature live weight was de®ned as the mean post-kidding weight for does, which were at least ®ve years old at the end of the study. This ®gure was found to be 38.9 kg with a range of 28.5±63.5 kg. This large variation in adult weights has been reported in other breeds of goat where breeding is not controlled and has been attributed to inbreeding (Devendra and Burns, 1983). However, it is possible that this variation also may re¯ect the lack of deliberate selection for heavier animals in such systems.
The does kidding for the ®rst time during the survey weighed approximately 66% and 71% of mature weight at mating and post-kidding, respectively. Even though mating was not controlled, the post-kidding weight was very close to the target post-kidding weight (75% of the mature weight) recommended for primiparous does in temperate regions and for tropical goats where breeding is controlled (Eik et al., 1991; Skjevdal, 1981).
5. Conclusion
The results of the survey showed that the changes in live weight and body condition score observed in Matebele does are in part the result of reproductive status but can be extensively modi®ed by various factors, the most important of which are seasonal conditions.
Acknowledgements
The ®nancial support of the International Develop-ment Research Centre (IDRC) of Canada, the Uni-versity of Zimbabwe Research Board and the Rockefeller Foundation, USA, for a study grant at the Bellagio Study Center, Italy awarded to L. Majele-Sibanda and L. R. Ndlovu is gratefully acknowledged.
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