5. Production parameters of ruminants in traditional systems

This chapter presents a review and analysis of the production parameters of cattle, sheep and goats in the traditional production systems described in Chapter 3.

Information on different production parameters was compiled for cattle and small ruminants from scientific and grey literature spanning the period 1973 to 2000. For each species, the data were collated by production system and AEZ within the previously defined four subregions of sub-Saharan Africa, namely Central, East, southern and West Africa. The hypothesis that livestock production parameters differ across the systems and zones on account of differences in feed resources and in the pressure imposed by various constraints (Jahnke, 1982) was investigated.

The following production parameters were selected for the analysis:

• mortality risk, defined as the probability of an animal dying during a specified time period (six months for lambs and kids, and one year for other classes of small ruminants and cattle);^[6]

• age at first parturition, expressed in months;

• parturition rate, defined as the number of parturitions per female per year;

• prolificacy, defined as the number of live offspring per parturition;

• milk offtake per lactation, defined as the milk used for human consumption (i.e. excluding that consumed by the calf/kid/lamb);

• offtake rate, defined as the proportion of animals sold or consumed in a year; and

• mean live weight of breeder females and males (uncastrated adult males used for breeding).

Information on mortality was compiled for the following classes of animals:

• young stock (up to 6 months of age for sheep and goats, and up to 12 months for calves);

• replacement females (from 12 months of age to first parturition for cattle and from 6 months to first parturition for small ruminants);

• replacement/fattening males (above 6 months for small ruminants and 12 months for cattle);

• breeding females (animals with at least one parturition); and

• breeding males.

The parameters were selected because they determine population dynamics and gross productivity. The gross productivity of livestock production systems is generally closely linked to the basic production parameters of fertility and mortality, the difference between which allows management decisions on the trade-off between sale, consumption and investment in herd growth (Putt et al., 1987). The data were analysed using descriptive statistics and the general linear model (GLM) procedure of the Statistical Package for Social Sciences (SPSS) 9.0.

Cattle

Tables 23 and 24 (and Appendices 6 and 7) present the reported production parameters of cattle in pastoral and mixed systems respectively. Although for some parameters very wide ranges are reported, both the mean and median values show that cattle production in traditional systems is uniformly poor, without striking differences between pastoral and mixed systems. In general, traditional systems are characterized by high mortality risks, low fertility rates, low milk offtake and low cattle offtake.

Table 23. Mean cattle production parameters of pastoral systems in sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

Table 24. Mean cattle production parameters in mixed systems of sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

² n.r. = no reference

The overall calf mortality risk in traditional systems is high, at 21.7 percent, and the mean calf mortality risks are practically the same between pastoral (21.4 percent) and mixed (22.6 percent) systems. The distribution of calf mortality risk in pastoral and mixed systems is presented in Figure 2, which shows that the median calf mortality risk is high across the different systems, ranging between 17 percent in the humid mixed system and 25 percent in the arid pastoral system.

The mortality risk for replacement stock in the traditional systems is also high, at 7.2 percent and 8.5 percent for male and female replacement cattle respectively. A further comparison of mortality risks among replacement stock between the pastoral and mixed systems shows that they are very similar: mean reported female replacement mortality risk in the pastoral system is 6.4 percent, while it is 7.5 percent in the mixed systems; mean male replacement mortality risk is 7.3 percent in the pastoral system and 8.7 percent in the mixed systems. Although the mean cow mortality risk in mixed systems is high, at 5.8 percent, it is significantly lower than that prevailing in pastoral systems, at 7.9 percent (p = 0.013). Overall mean cow mortality risk in the traditional systems is high, at 6.3 percent.

Figure 2. Reported calf mortality risks in pastoral (P) and mixed (M) systems of sub-Saharan Africa

Since stock mortality is one of the most important parameters determining population dynamics and hence the gross productivity of livestock production systems (Putt et al., 1987), high mortality risks, especially among calves, may be viewed as a major constraint in traditional cattle production systems in sub-Saharan Africa.

In general, cattle in traditional systems have a delayed mean age at first calving of 47.9 months, with a wide range from 33.4 months to 62.5 months. The mean ages at first calving are virtually the same in pastoral (48.1 months) and mixed (48.8 months) systems. Calving rates in traditional cattle systems are low, at 58.7 percent (median of 58 percent), and reported values have a very wide range, from 28.0 to 89.9 percent. The mean calving rates for pastoral and mixed systems are similar, at 60.8 percent and 58.2 percent respectively. Figure 3 presents the distribution of reported calving rates in pastoral and mixed systems. It shows that the median ranges between 44 percent in the highland mixed system and 61 in the subhumid mixed system.^[7]

Milk offtake per lactation in traditional systems is generally low, at an average of 252 kg (median of 251 kg). It ranges from 60 kg to 508 kg per lactation. The mean milk offtake per lactation reported in pastoral (252 kg) and mixed (253 kg) systems is virtually identical and very low. Figure 4 presents the distribution of reported milk offtake per lactation. The median is between 200 and 300 kg, with a particularly narrow range in pastoral systems.

Figure 3. Reported calving rates in pastoral (P) and mixed (M) systems of sub-Saharan Africa

The mean of reported offtake rates for cattle in traditional systems is 9.9 percent (median of 9 percent) and ranges from 1.2 to 20.0 percent. Although the mean of reported offtake rates for cattle in pastoral systems (12.0 percent) is higher than in mixed systems (9.3 percent), the difference is not statistically significant. The mean offtake rate for southern Africa is 6.7 percent, which is lower than for the other regions (13.6 percent, 12.3 percent and 10.8 percent for Central, East and West Africa respectively).

The mean weight of mature cows in traditional systems is 244 kg (median of 250 kg), ranging from 152 kg to 357 kg. The mean weights of mature cows in pastoral (249 kg) and mixed (243 kg) systems are similar. Based on the unweighted GLM procedure, the weights of mature cows are different across the subregions (p < 0.001). They are also different across the systems (p = 0.034), with a significant interaction between systems and subregion (p = 0.019). Mature cow weights in southern Africa (297 kg) are significantly higher than in Central (228 kg), East (244 kg) and West (233 kg) Africa.^[8] Mature cow weights in the mixed systems in the semi-arid and subhumid zones are higher than those in mixed systems in the humid zone and in the highlands.

Figure 4. Reported milk offtake per lactation (kg) in pastoral (P) and mixed (M) systems of sub-Saharan Africa

The mean weight of mature bulls in pastoral systems is 322 kg, which is similar to the 326 kg reported in mixed systems. The mean weights of mature bulls by subregion are as follows: 334 kg, 322 kg, 380 kg and 290 kg in Central, East, southern and West Africa respectively.

Sheep

The production parameters of sheep in the traditional systems of sub-Saharan Africa are presented in Tables 25 and 26 (and Appendices 8 and 9) and are characterized by high mortality risks, especially for lambs. The mean of reported lamb mortality risks in the traditional systems is around 26.7 percent (a median of 25 percent) and ranges from 6.5 to 51.5 percent. The mean (and median) lamb mortality risks in pastoral (29.3 percent) and mixed (25.4 percent) systems are similar (Figure 5). The mortality risk for replacements is also high, at 9.4 and 10.9 percent for female and male replacement stock respectively. Although the replacement mortality risk is generally higher in pastoral systems (11.6 percent and 11.7 percent for female and male replacement stock respectively) than in mixed systems (9.0 percent and 10.8 percent), the difference is not statistically significant. Furthermore, adult mortality risks are also high, with a mean ewe mortality risk of 11.1 percent. The mean ewe mortality risk in pastoral systems (13.4 percent) seems higher than in mixed systems (10.4 percent). However, this apparent difference is not statistically significant.

Table 25. Mean sheep production parameters of pastoral systems in sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

Table 26. Mean sheep production parameters in mixed systems of sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

² n.r. = no reference

The mean age at first lambing is 17.5 months, with a median of 15.6 months and a very wide range of 11.0 months to 48.0 months.^[9] The age at first lambing in pastoral systems (18.7 months) is higher than in mixed systems (16.7 months); however, this difference is not statistically significant. The mean lambing rate reported in traditional systems is 109.8 percent, with a median of 113.4 percent and a wide range of 50 to 160 percent. The mean lambing rate in pastoral systems (96.1 percent) is significantly lower than in mixed systems (114.9 percent) (p = 0.009). The mean reported prolificacy is 1.12, with a median of 1.08 and range of 1.00 to 1.50. Reported prolificacy of sheep in pastoral systems (1.06) is significantly lower than in mixed systems (1.13) (p = 0.041).

Figure 5. Reported lamb mortality risks in pastoral (P) and mixed (M) systems of sub-Saharan Africa

The mean offtake rate for sheep in traditional systems is 20.8 percent, being very similar between pastoral systems (21.6 percent) and mixed systems (20.8 percent).

The mean weight of ewes in traditional systems is 28.7 kg (median of 29.5 kg), but ranges widely from 15.0 kg to 43.8 kg. The mean reported weights of ewes in pastoral systems (30.9 kg) and in mixed systems (27.9 kg) are similar. Pairwise comparisons using the Bonferroni and Tahmane procedures shows that the weight of ewes in semi-arid pastoral, semi-arid mixed and highland mixed systems is higher than in subhumid mixed systems. Furthermore, in West Africa, it is also higher in pastoral systems (29.8 kg) than in mixed systems (24.7 kg) (p = 0.042). The mean weight of rams in traditional systems is 31.2 kg, with a median of 30.0 kg and a wide range of 16.4 kg to 48.7 kg. The mean weight of rams in pastoral systems (36.9 kg) is also higher than in mixed systems (28.9 kg) (p = 0.004).

Goats

The production parameters of goats in the traditional system are presented in Tables 27 and 28 (Appendices 9 and 10). Traditional goat production systems in sub-Saharan Africa are characterized by high mortality risks, especially for kids (27.8 percent, with a median of 28.6% and a very wide range of reported values from 2.5 to 53.2 percent). The mean kid mortality risks in pastoral systems (29.7 percent) and in mixed systems (27.2 percent) systems are not only high but also similar. The median kid mortality risks range from 15.6 percent in highland mixed systems to 34 percent in the semi-arid pastoral systems (Figure 6). Although kid mortality risks are similar across different systems, within East Africa they are significantly different between pastoral systems (29.3 percent) and mixed systems (21.9 percent) (p = 0.007).

Table 27. Mean goat production parameters of pastoral systems in sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

Table 28. Mean goat production parameters in mixed systems of sub-Saharan Africa by agro-ecological zone

¹ Numbers in brackets represent number of studies

² n.r. = no reference

The mortality risks for replacement stock in the traditional systems are high: 12.6 percent and 13.6 percent for female and male replacement goats respectively. Adult mortality risks are also high, at 12.2 percent, with a median of 12 percent and a wide range of 5 to 33.0 percent. It is worth noting that in general the mortality risks are similar between pastoral and mixed systems, with the exception of East Africa, where female replacement and doe mortality risks are significantly lower in mixed than in pastoral systems - i.e. 8.8 percent versus 15 percent (p = 0.003) for female replacements and 7.6 percent versus 15.3 percent for does (p = 0.013).

The age at first kidding in pastoral systems is 16.5 months, which is essentially the same as that in mixed systems (16.4 months). The mean reported kidding rate in traditional systems is 121.1 percent, with a median of 116.2 percent and a wide range of 73.3 to 208 percent. Although the mean kidding rate in pastoral systems (109.4 percent) is lower than in mixed systems (126 percent), the difference is not statistically significant. Mean prolificacy is 1.34, ranging from 1.02 to 1.83. Reported prolificacy of goats in pastoral systems (1.22) is significantly lower than in mixed systems (1.36) (p = 0.015).

The means of the reported weights of does and bucks are 27.8 kg (median 27.2 kg and range of 17.2 kg to 43.7 kg) and 32.0 kg (median 30.0 kg and range of 19.4 kg to 47.0 kg) respectively. The mean weights of does in pastoral systems (27.1 kg) and in mixed systems (27.8 kg) are similar, while the mean weights of bucks reported in pastoral systems (36.9 kg) are significantly higher than in mixed systems (29.5 kg) (p = 0.005).

Figure 6. Reported kid mortality risks in pastoral (P) and mixed (M) systems of sub-Saharan Africa

The mean offtake rate for goats is 21.4 percent, with a median of 21.4 kg and a wide range of 13.4 to 34 percent. The mean offtake rate for goats in pastoral systems (23.7 percent) is slightly higher than in mixed systems (21.9 percent), but the difference is not statistically significant.