Measuring heterogeneous preferences for cattle traits among cattle-keeping households in East Africa.

The estimates are validated using the household-level survey data and past studies. Estimates of willingness to pay (WTP) for traits parameters indicate that a trypanotolerant animal is valued at U.S. $25 more than a trypano-susceptible one. According to the survey data, the average cost of treatment or control of trypanosomosis per year per herd varies from U.S. $6 to U.S. $37 in Ethiopia, while in Kenya it is an average of U.S. $36 in crop-livestock systems but can be as high as U.S. $219 in pastoral systems, depending on the herd size and number of treatments per year. The choice experiment estimate of U.S. $25, therefore, appears plausible, although more information can be gained by assessing the distribution of the estimate in the population. An adaptive bounded kernel density approach has been utilized to examine the distribution of the WTP for the various traits that have values that are inherently bounded from below by zero. We employ Gaussian kernels with variable-bandwidth density estimator that supports boundary correction for variables with bounded domain (Jann 2005). (11) However, WTP trait values for traction potential may plausibly take positive and negative values, since it is a highly valued trait in cropping systems, yet most pastoral communities view use of cattle for draft power as a taboo and therefore exhibit negative preference for the trait. Similarly, cattle keepers have a negative preference for cows that require supplementary purchased feeds to boost milk production. This is probably because most of the systems in the study area are subsistence and not market oriented and additional costs associated with production result in a decrease in utility. These distributions are presented in figure 1. The distribution of WTP values for trypanotolerance presented in figure 1(a), shows a bimodal distribution having two peaks at U.S. $19 and 36. This indicates presence of heterogeneity in trypanotolerance trait valuations. Although little is reported in the literature about valuation of trypanotolerance using stated preference methods, Tano et al. (2003) show that disease resistance can be ranked very highly under production systems of similar types to those covered in this study.

The kernel density plot in figure l(b) for traction potential also provides evidence of heterogeneous preferences for traction potential in bulls, indicated by the substantial negative values and the bimodal distribution density having two peaks above zero. The mean of the WTP distribution is U.S. $58 for a bull with good traction potential. This finding is consistent with the finding by Tano et al. (2003) who found that fitness to traction was the highest ranked trait for bulls in West Africa.

[FIGURE 1 OMITTED]

Live-weight increase, which is associated with meat production, is valued at U.S. $1.05 per kg. This is comparable to the average slaughter weight value of U.S. $1.02 per kg found in Scarpa et al. (2003) for a pastoral system in Kenya. A bull that needs to be watered only once every two days, used as a proxy for drought tolerance, is valued at U.S. $7 more than one that needs to be watered twice per day. This is not surprising, since water is a constraint in the study areas especially during the dry seasons. The trait is, however, not significant for cows. The kernel density distribution of WTP values for low watering frequency in figure l(c), is tight with values concentrated around the mean, indicating homogeneity in preference for this trait.

An important attribute in cows is the ability to calve every year instead of once in two years. The Zebu cattle breeds, kept by most of the respondents in the study sites, tend to have relatively longer calving intervals of about 1.8 years. A calving interval trait of one year is valued at U.S. $9.4, which is even higher than the value of U.S. $8.1 for a cow with high milk production. The kernel density distribution of WTP for reproduction ability in figure 1 (f), indicates large variance for positive values. The value of purchased supplementary feeds for cows that cattle keepers would be willing to accept as compensation for utility reduction is U.S. $10.7. Cattle keepers are reluctant to raise cows requiring purchased supplementary feeds to boost milk production. Due to scarce financial resources, the cattle keepers prefer cattle that do not require externally acquired inputs. The kernel distribution associated with the implicit price for supplementary feeds in figure 1(d), has a mean substantially in the negative range indicating significant aversion to this trait, though there is a small fraction in the positive orthant.

The maximum likelihood estimates for the latent class model for cows and bulls are reported in tables 6 and 7. To identify the number of latent classes to be used in the analysis, we employed the Bayesian Information Criterion (BIC) proposed by Boxall and Adamowicz (2002). This criterion is low and more intuitive for the model with three classes for bulls and cows. (12) Therefore, we estimated three-class latent class model (LCM) for cows and bulls. The LCM results indicate significant heterogeneity in preferences across latent classes as revealed by the differences in magnitude and significance of the utility function parameter estimates. For instance, table 6 indicates strongly positive trypanotolerance trait coefficient for class 3 in comparison to the other two classes while the traction coefficient is strongly positive for class 1. The class membership coefficients for the third class were normalized to zero in order to be able to identify the remaining coefficients of the model. The class membership coefficients for bulls and cows estimations indicate that the probability of being in a class is significantly related to the cattle keepers' production system. Table 6 shows that 54% of the respondents who participated in the choice experiment for bulls have a fitted probability to belong to class 1, which is strongly significant for agro-pastoralists. On the other hand, 19% and 27% of the respondents have a fitted probability to belong to class 2 and 3, respectively. Class 2 membership coefficients indicate that members of this class are likely to be pastoralists, younger household heads with low levels of education and high income relative to class 3. Class 3 could subjectively be associated with crop--livestock farmers. Class 1 for cow traits in table 7 is strongly significant for agro-pastoralists while class 2 is significant for crop--livestock farmers, who have a lower income, relative to class 3, and practice some tsetse fly control measures to control trypanosomosis. Class 3 could subjectively be associated with being a pastoralist.

Calculations of implicit prices of the traits across the latent classes show marked differences in preference structure as presented in table 8. Cattle keepers in class 1 attach a high value to good traction potential in bulls, which is even higher than the value they attach to trypanotolerance and high fertility in bulls. This is not totally unexpected since agro-pastoralists, the most likely members of this class, consider draft power capacity in bulls for ploughing and threshing grains an important reason for keeping cattle. This is further supported by the fact that their cattle herd contains more males (average of 2.2) than females (average of 1.7). Reproductive potential in cows is also an important trait for this class, while milk production is not statistically significant, suggesting that the trait is not important for this class.

Class 2, mainly associated with pastoralists (for bull traits), exhibits a different preference structure from the other two classes. In this class, high fertility in bulls is a highly valued trait, while trypanotolerance and live-weight have the same weight. Traction fitness is not highly valued in this class, a finding that is in line with expectations, since pastoralists do not use cattle for traction. They are more concerned with obtaining larger herd sizes, which is linked to high fertility trait in bulls. This class is also associated with crop-livestock farmers for cow traits who exhibit negative preferences for cows that need supplementary purchased feeds. High milk production is an important trait for this class, though reproduction potential was not found to be significant. Class 3, comprising mainly the crop-livestock farmers (for bull traits), displays a high-preference for trypanotolerant animals and bulls with good traction potential. High fertility in bulls is not a significant trait in this class. In this system, bulls are used for ploughing crop fields. For cows, high milk yield and high reproduction potential are valued by the pastoralists.

Conclusions

This article has employed mixed logit and latent class models to examine farmers' preferences for cattle traits in Kenya and Ethiopia, using choice experiment data for bulls and cows. The empirical results provide several insights to understanding cattle keepers' choice behavior. The results from the mixed logit model revealed significant preference heterogeneity among cattle owners, based on the environment and production system. Good traction potential, fertility, and trypanotolerance were found to be the most preferred traits in the model of bull preferences. The most valued traits in the cow preference models were trypanotolerance and reproductive performance.