J.L.N. Sikosana1 and J. Gambiza2
1Matopos Research Station, Private Bag K5137, Bulawayo, Zimbabwe
2Makoholi Experiment Station, Private Bag 9150, Masvingo, Zimbabwe
Summary
Introduction
Materials and methods
Statistical analysis
Results
Discussion and conclusion
Acknowledgements
References
The effects on animal performance and vegetation changes of cattle and goats grazing together at five different stocking rates in a continuous grazing system are being studied at Matopos Research Station. In the long term, the trial is expected to provide information on the impact of climatic cycles. Preliminary results for the first three years are presented. Year effect was significant (P<0.01). The lightest stocking rate (3.3 ha/LU) for both goats and cattle had higher (P<0.01) performance levels compared with other treatments. There was no effect of treatments on density and basal cover of herbaceous plants.
Elevage caprin en système mixte bovin-caprin: effet des taux de charge et de substitution sur la stabilité des formations à épineux sur sol rouge
Résumé
Les effets sur les performances zootechniques et sur l'évolution de la végétation de la mise au parcours de bovins avec des caprins à raison de cinq taux de charge différents ont été étudiés à la station de recherche de Matopos (Zimbabwe). A long terme, l'essai devrait fournir des informations sur l'impact des cycles climatiques. Les premiers résultats des trois premières années sont présentés. L'effet de l'année était significatif (P<0,01). Le niveau de performance obtenu avec le taux de charge le plus faible (3,3 ha/UBT) pour les caprins et les bovins était significativement supérieur (P<0,01) à celui obtenu avec les autres traitements. Les traitements n'avaient pas d'effet sur la densité et la surface terrière pastorale des herbacées.
Many grazing areas of Southern Africa are badly degraded or are in the process of becoming unproductive because of the encroachment of dense bush. Donaldson (1979) reported that it is usually impractical or uneconomical to thin or remove the woody components. It has been suggested that the full production potential of bushveld areas can be realized by integrating goats into cattle farming systems (Aucamp, 1976).
Mixed species grazing has received little research attention, despite the fact that most communal and small-scale commercial farmers in Zimbabwe graze cattle and goats together. Goats seem to survive droughts better than cattle. This has led to the belief that goats degrade rangelands more than cattle. However, it is argued that stocking rate is the most important variable that affects rangeland condition rather than animal species per se (Gambiza and Sikosana, 1989). A multidisciplinary study on the interaction of goats and cattle grazing on redsoil thornveld was started in 1989. The objectives were to study the effects on rangelands of different goat and cattle stocking and substitution rates and the productivity of goats in a mixed goat and cattle system.
A continuous grazing system was used. Preliminary results on the standing biomass of herbaceous plants and animal performance for the three seasons are presented.
The study is being conducted at the Matopos Research Station in the south west of Zimbabwe. The site is at an altitude of 1340 m with a mean annual rainfall of 600 mm which falls between October and April. Marked fluctuation in rainfall brings about corresponding fluctuations in herbage production from year to year. October is the hottest month (mean maximum of 29.4°C) and June the coolest (mean maximum of 20.9°). The land is characterised by clay soil (red and black), thorny acacia species and other shrubs in the browse layer, while the field layer is composed of perennial grasses with occasional annuals. A brief description of the area and its dominant vegetation has been documented (Ward et al, 1979).
Initially the site was subjected to a uniform grazing regime prior to the introduction of treatments. Ten paddocks of 20 hectares each were grazed continuously at a medium stocking rate of 2.8 ha per livestock unit (LU = 500 kg liveweight). In June 1989 the planned stocking regimes were applied (Table 1). Goats were substituted for cattle on the basis of metabolic liveweight. The conversions to LUs assume 1.67:1 for cattle and 10:1 for goats. Additivity is then assumed for the treatments although this is likely to give high estimates of the true rates and is to be the subject of study in the trial. A total of 60 steers were used in the trial. They were maintained in two age groups, weaners and long weaners in equal proportions. The long weaners were slaughtered each year at the age of two and a half years and replaced by weaners. Monthly weights were recorded, and carcasses were assessed as described by Moyo (1991). Slaughter data is used to assess cattle productivity from each treatment.
Table 1. Cattle and goat numbers and stocking density in a mixed species stocking rate trial on redsoil thornveld.
|
Treatment |
Cattle |
Goat |
Ha/LU* |
LU/20ha |
|
1. Light-cattle |
8 |
12 |
3.3 |
6.0 |
|
2. Heavy-cattle |
8 |
36 |
2.1 |
8.1 |
|
3. Light-goat |
4 |
36 |
3.3 |
6.0 |
|
4. Heavy-goat |
4 |
60 |
2.4 |
8.1 |
|
5. Medium: cattle-goat |
6 |
36 |
2.8 |
7.2 |
LU = 500 kg liveweight. The animal species contributing the higher proportion of livestock units has been quoted.
A total of 360 indigenous (Matabele goat) breeding does of stratified age groups were used. All goats were mated in May and June to kid once a year during the start of the wet season (October and November). The offspring from the goats were weaned at an average age of five months and details of birth, deaths and weaning were recorded. Reproductive performance of the does was assessed.
Herbaceous and woody plant dynamics (species composition, basal cover, density of above-ground grass biomass) and soil variables were measured in permanent plots.
The annual rainfall at the experimental site for the duration of the trial is shown in Figure 1. Superimposed on Figure 1 is the long term mean rainfall at the site.
Figure 1. Annual rainfall at the site of the cattle-goat mixed grazing system.
Data were analysed by the analysis of variance (ANOVA) using a General Linear Model (SAS, 1982) fitting replication, treatments and their interactions.
Animals that became sick or died in the course of the experiment were replaced with animals of similar weights. This was done to maintain the prescribed stocking pressure. Data from these animals and their replacements were not included in this preliminary analysis.
Livestock data for different stocking rates are presented in Table 2 (production traits of goats), Table 3 (steer productivity), Figure 2 (total weaner production from goats, kg per 20 ha) and Figure 3 (the overall doe productivity).
Goat performance under the lightest stocking rate was higher (P<0.01) than other treatments. Figure 2 shows that weaner production from goats increased when total and goat stocking rate was low (P<0.01). Other treatments resulted in inconsistent productivity over the three years. This is also the trend in the overall doe productivity (Figure 3).
Table 2. Production traits of goats in a mixed cattle and goat grazing system (1989/90 to 1991/92).
|
|
1 |
2 |
3 |
4 |
5 |
SE |
|
Stocking rate (ha/LU) |
3.3 |
2.4 |
3.3 |
2.4 |
2.8 |
|
|
No. of goats: steers |
12:8 |
36:8 |
36:4 |
60:4 |
36:6 |
|
|
Total no. of does kidded |
51 |
136 |
119 |
157 |
136 |
|
|
Prolificacy1 |
1.6 |
1.4 |
1.4 |
1.3 |
1.4 |
0.05 |
|
Kid birth weight (kg) |
2.0 |
1.8 |
1.9 |
1.8 |
1.8 |
0.14 |
|
Kid weaning weight (kg) |
15.9 |
13.5 |
13.6 |
20.8 |
13.0 |
0.30 |
|
Pre-weaning gain (kg) of kids |
13.0 |
11.0 |
11.0 |
8.6 |
10.7 |
0.37 |
|
Kidding %2 |
127.2 |
97.5 |
95.0 |
71.9 |
104.9 |
5.31 |
1 Prolificacy (litter size)= number of kids born/number of does kidding
2 Kidding % = number of kids born/number of does mated X100
Table 3. Weight gain and carcass characteristics of steers in a mixed cattle and goat grazing system (1989/90 to 91/92).
|
Treatment |
1 |
2 |
3 |
4 |
5 |
SE |
|
Stocking rate (ha/LU) |
3.3 |
2.4 |
3.3 |
2.4 |
2.8 |
|
|
No. of goats: steers |
12:8 |
36:8 |
36:4 |
60:4 |
36:6 |
|
|
Total no. of cattle slaughtered |
16 |
16 |
8 |
8 |
12 |
|
|
Initial weight at 8 months of age (kg) |
191 |
192 |
197 |
197 |
189 |
4.14 |
|
Weight gain per head (kg) |
111 |
115 |
126 |
122 |
109 |
7.19 |
|
Cold carcass weight (kg) |
117 |
115 |
126 |
120 |
112 |
3.29 |
|
Carcass length (cm) |
118 |
117 |
118 |
118 |
115 |
1.26 |
|
Eye muscle area (cm³) |
38.4 |
40.6 |
43.9 |
40.5 |
37.2 |
1.8 |
Figure 2. Total weaner production from goats (kg per 20 ha) in a cattle-goat mixed grazing system.
Figure 3. Overall doe productivity (number of kids weaned X Average weaning weight of kids/Number of does
It is evident that the annual liveweight production of steers (Table 3) was largely dependent on total biomass (Table 4). Steers in treatment 3 had the highest (P<0.05) weight gains over the three years.
Stocking rate is now widely accepted as the major factor associated with livestock output. If productivity is to be maintained, the stocking rate has to be appropriate to the output goal and adjusted to the carrying capacity of the ecosystem. This should also reduce abuse of grazing land, essential in semi-arid areas.
Results from this study suggest that the productivity of indigenous goats, when managed correctly in conjunction with grazers (cattle), is potentially acceptable. This agrees with Aucamp et al (1984). A prerequisite for implementing an integrated system is determining an appropriate mix of cattle and goats in order to utilise efficiently both the herbaceous and woody vegetation. Discussion of mixed grazing at this stage of the trial is restricted due to lack of adequate information. More research is needed to explain the biological processes involved (Nolan, 1979; Shuster, 1986).
These results show that livestock productivity varied across treatments. This could be due to seasonal variations and differences in forage availability during the study, as well as stocking rate.
Livestock equivalents for cattle and goats need further investigation. These may have to vary from region to region depending on the species composition of the grazing areas. Sound animal and veld management practices, together with the correct ratios of cattle and goats, are essential for success.
Table 4. Grass basal cover (%) and peak biomass (tonnes dry matter ha) in a mixed cattle and goat grazing system.
|
Treatment |
1 |
2 |
3 |
4 |
5 | |
|
Stocking rate (ha/LU) |
3.3 |
2.4 |
3.3 |
2.4 |
2.8 | |
|
No. of goats: steers |
12:8 |
36:8 |
36:4 |
60:4 |
36:6 | |
|
Basal cover |
(1990) |
2.9 |
3.5 |
4.0 |
3.4 |
3.3 |
|
|
(1991) |
2.9 |
3.5 |
4.4 |
3.0 |
3.4 |
|
|
(1992) |
2.2 |
1.8 |
3.0 |
1.6 |
1.6 |
|
Biomass |
(1990) |
1.2 |
1.3 |
1.6 |
1.3 |
1.3 |
|
|
(1991) |
0.6 |
0.5 |
0.9 |
0.5 |
0.6 |
|
|
(1992) |
0.12 |
0.16 |
0.08 |
0.01 |
0.01 |
The technical assistance of the Smallstock and Veld and Pasture Teams of Matopos Research Station is gratefully acknowledged. Mr Mario Beffa is thanked for assistance with statistical analyses (livestock data). Dr Smith is thanked for reading and commenting on the original manuscript.
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