Study area description
This project contributes to a larger project, called Senegal Dairy Genetics Project (https://senegaldairy.wordpress.com/ and Marshal et al. 2016; Marshall et al. 2017; Marshall et al. 2020). The Senegal Dairy Genetics project was conducted in two regions within Senegal namely Thiès (Khombole and Tivaouane departments) and Diourbel (Mbacke and Touba departments). In these sites there has been a variable magnitude of dairy production intensification, including the introduction of exotic breeds (mainly through the government AI programs) and better feeding schemes (Seck et al. 2016). For more information on site selection and for site descriptions see Tebug et al. ( 2018) and Marshall et al. (2020).
Households
Two hundred and twenty (220) dairy cattle keeping households were included in the overall Senegal Dairy Genetics project. Cattle enterprises were defined as dairy if they produced milk for human consumption (though many could also be considered dual-purposes, as they also sold animals for meat). These households were selected, amongst other, to ensure a diversity of cattle breed-types (Marshall et al. 2020). For the analysis presented in this paper, households were excluded if they went transhumant over the survey period (as it was not possible to collect full data over this period (51 households), if they did not have full data for other reasons (26 households), or if the household did not have any lactating animals over the survey period (14 households). Finally, sixteen (16) households were excluded for having a NR component (such as a cost or benefits) 3.5 standard deviations above or below the mean, so that these outliers would not affect the interpretation of trends in subsequent analysis. The final number of households considered for inclusion in this analysis was thus 113 (though for the analysis comparing breeds, 6 additional households were excluded for either not having a predominant breed-type or keeping breeds other the main breed-types being compared).
Data collection
Data collection comprised baseline surveys (conducted May to July 2013) and longitudinal surveys (July 2013 to April 2015). During the longitudinal survey, households were visited 13 times, at approximately equal time intervals, with information collected for the time-period back to the previous visit. Both baseline and longitudinal surveys collected a range of information, including information on economics (costs and benefits) of the household dairy cattle enterprise as well as animal level data, such as milk yield, reproductive events, and animal movements (including purchases and sales). Trained enumerators in the local language of Wolof conducted all surveys. See Marshall et al. (2020) for more details, including links to the surveys and data.
Calculation of economic performance of the household dairy cattle enterprises
Net returns (NR) and gross margins (GM) for each household dairy cattle enterprise were calculated based on household-level data collected through the surveys. NR considered all income and benefits, whereas GM only considered income and cash costs (see more details below). Both were calculated as per household herd per annum (phpa) and per cow per annum (pcpa). Data was collected in the local Senegalese currency (CFA), but presented here in USD, with a conversion factor of 580 CFA per 1 USD used.
NRphpa and GMphpa were calculated as below.
Where income components (I) comprise that from the sale of milk and milk products (Imilk sale), animal sale (Ianimal sale) and other incomes (Iother incomes). Benefit components (B) comprised milk consumed by the household members (Bmilk consumed), milk given away to others for consumption (Bmilk given away), animals gifted to the household as dowry or inheritance (Banimals gifted in) as well as those given away as inheritance, dowry, or for ceremonies (Banimals given away). Cash costs components (C) comprise the costs associated with the animal purchase (Canimal purchase), animal feed (Cfeed), hired labour (Chired labour), health-care of the animals (Chealth), animal housing (Chousing), cow reproduction (Creproduction), repayment of loans associated with the household dairy cattle enterprise (Cloan repayment), water for the animals (Cwater) and any other expenses (Cother expenses). Other costs (OC) comprised milk given away (OCmilk given away), animals given away (OCanimals given away) and household-labour (OChousehold-labour)). Note that milk given away and animals given away were included both as benefits and as costs: benefits because they are products of the farm and costs because the household members do not utilize them.
NRpcpa was calculated as NRphpa divided by herd size in cow years (similarly for GMpcpa). One cow year was considered as a cow being in the herd for a full year (for example, one cow year could be equal to two cows in the herd for six months each). A cow was defined as a female of 2 years of age or greater.
Calculation of the different components is described below. In all cases, these were initially calculated per household herd over the specific time-period that household was monitored (which ranged from 481 to 565 days). The resultant values were then converted to an annual time-period. See also the supplemental data for more on the components.
Imilk sale, Bmilk consumed, Bmilk given away,OCmilk given away Milk quantities were recorded for each lactating cow, for morning and evening milking, each data collection data (test-day), with the sum of these giving test-day milk yields (milk suckled by calves was excluded). Missing morning or evening milk records were predicted as per ICAR (2017) using the Liu et al. (2000) modified method. The survey collected information on how the test-day milk was used, including whether it remained ‘fresh’ or was processed (for example, into ghee or curd) and whether the fresh or processed milk was sold, consumed by the household, given away to others for consumption, or wasted. When sales occurred, the sale price was recorded. This data was used to determine the total value of fresh and processed milk sold for each test day (as the number of units of a product sold multiplied by the sale price for that unit, summed over the different milk products). The value of milk and processed milk for each day between the test-days was determined as the average of the proceeding and following test-days, with all daily values summed to give Imilk sale over the monitoring period. Bmilk consumed, Bmilk given away, and OCmilk given away were determined by the same process, with the fresh or processed milk valued at the same price as that which the household would have sold it. In the case of missing data on the sale price of fresh milk or processed milk for a particular survey round, the mode of the relevant sale prices from other rounds was used.
Ianimal sales, Banimals given away, OCanimals given away Ianimal sales was calculated as the summed value of all animals sold, whether alive or after slaughter. The value of animals sold was the sale price of animals as given by the farmers less any costs associated with the sale (such as transport or brokerage). The value of the animals sold but who had a missing sale price was determined as the modal sale price of the animals of the same sex, age, and breed type. The value of Banimals given away and OCanimals given away were determined analogously.
Iother incomes Income from other sources (Iother income), which was typically from taking care of animals belonging to other households, was summed over survey rounds.
Canimal purchase, Banimals gifted in Canimal purchase was calculated as the summed value of all animals purchased including transportation costs and other purchasing costs. The value of animals purchased but who had a missing purchase price was determined as the modal purchase price of the animals of the same sex, age, and breed type. The value of Banimals gifted in was determined in an analogous method.
Cfeed, Cfeed was determined by summing all feed purchases, including the cost of transporting the feed to the households. In cases where a specific feed purchase was reported, but without a purchase price, the purchase price was determined as the modal feed price for that feed type and quantity.
Chired labour, OChousehold-labour Chired labour was determined based on the salary of hired laborer (and did not include other benefits laborers may receive, such as meals or accommodation). If the labourer also provided labour to other household activities outside of the dairy cattle enterprise, the labour cost was prorated accordingly. Household labor (OChousehold-labour) was valued based on hired labour costs. Specifically, the modal labour cost per hired labourer was determined across all households, and this was used to determine the household labour cost prorated for the time the household members contributed to the household dairy cattle enterprise.
Chealth Chealth was determined as the total cost of all animal health care, whether preventative or curative. It was inclusive of medical supplies and payment of the service providers. Where there was missing data for Chealth the modal cost for the same type of care, for the same animal type and number, was used.
Chousing Chousing was determined by summing depreciation costs and maintenance costs of animal houses and other structures used by a household for cattle keeping. Depreciation costs were calculated over 15 years (Marshall et al. 2020). Structure construction cost (on which the depreciation was based) was taken as reported by the farmer in the baselines survey round. This cost was prorated cattle only used part of the space. Where structure construction cost was missing, the mode cost of constructing the same structure type was used. For households renting structures for dairy, the rental price was used.
Creproduction Creproduction was the sum of all costs associated with cow servicing by AI and that for hiring a bull for natural mating. AI services provided by the state had zero cost.
Cloan repayment Cloan repayment was the sum of interest incurred on loans taken out to support the household dairy cattle enterprise. Loan repayments were calculated using loan interest rates and grace periods for each loan.
Cwater Cwater was determined by summing water purchase costs and their associated transport costs. Where purchased water was also used for purposes other than the household cattle enterprise, the purchase and transport cost were pro-rated accordingly.
Cother expenses This comprised the cost of other expenses incurred concerning the household dairy cattle enterprise (Cother expenses) other than those listed above, for example co-operative fees, and the cost of buying ropes and milking buckets.
Comparisons between groups of households
Comparisons of economic performance were made between households grouped by (a) ranking on NRpcpa and (b) main breed-type kept. For NRpcpa households were grouped into five groups of approximately equal numbers, referred to as groups 1 to 5, with group 1 having the lowest NR and group 5 the highest. For main breed-type kept, households were grouped by the predominant breed-type they kept (see below for how animals were assigned a breed-type, and also note that most households kept a mix of breed-types but with a predominant type). Comparison of means between the groups was performed using a one-way analysis of variance (ANOVA) with a significance level (alpha) of 0.05. For cases of significance differences, the post-hoc test Tukey’s honestly significant difference (HSD) was used to further explore mean differences, with a family-wise error rate of 0.05.
Assignment of breed-type
Cattle involved in the study were assigned a breed-type based on either genomic information or (for those animals not genotyped) farmer recall as described in Marshall et al. (2020). The breed-types assigned were indigenous Zebu (IZ); Indigenous Zebu and Bos taurus cross (IZ x BT), Indigenous Zebu and Guzerat cross (IZ x GZ), and High Bos taurus (HBT). Note that within each group there was a range in the mix of breed type. For example, animals were assigned to the IZ group if they were 88% or more IZ according to genotype analysis for breed composition. As another example, animals were assigned to the IZ x GZ if their proportion of IZ from the genotype analysis was between 0.39 and 0.86: see Marshall et al. (2020) for the specifics of other cases. The most common Zebu breeds were Zebu Gobra and Zebu Maure. The Bos Taurus breeds were mainly Montbeliarde and Holstein Friesian, both bred for their high milk production. The Guzerat breed is a tropical breed developed from Indian Krankej cattle and Brasilian Crioulo cattle of European origin (Peixoto et al. 2010).
Drivers of net returns
Multi-variable regression analysis was used to determine what other factors (outside those included in the NR calculations) affected NRpcpa and NRphpa. See Table 1 for the list of independent variables included in the full model. We also considered including gender of the household head, but there were too few female headed households (7 in total). The final (reduced) model was determined using stepwise regression with backward elimination based on Akaike’s Information Criterion (AIC), in R Core Team (2021) and the MASS package (Venables and Ripley 1999).