Early vine harvesting of dual-purpose sweet potato (ipomoea batatas) increases feeding quality and total biomass without comprising tuber production

Sweet potato is an important food crop throughout much of sub-Saharan Africa with the important attribute as a dual-purpose crop. While tuberous crops are grown for human consumption, the sweet potato can also provide substantial vine biomass suitable for feeding animals without competing for human feed resources. Sweet potato is generally low in nutrient other than carbohydrate. The newly developed orange-fleshed varieties of sweet potato, high in beta-carotene yield large quantities of vines with very little exploration of their agronomic attributes to date. Intermediate vine harvesting (ratooning) has been promoted as a strategy to further increase the value of sweet potato as a dual-purpose human/animal feed crop. The results of this practice on yields of other types of sweet potato have been equivocal or highly variable. Production effects on three new orange-fleshed dual-purpose sweet potato (Kenspot 1, SPK 013, SPK 117) developed by the International Potato Centre (CIP), of intermediate plus final (INT) versus final only (FIN) vine harvesting were assessed in a randomized block with a split plot trial. Cultivar SPK013 produced the greatest vine, tuber and total biomass yield of the three varieties tested, but also the greatest decline in tuber yields after intermediate vine harvesting. While intermediate harvesting increased vine yield in all varieties (p<0.05), in cultivar SPK013, it caused a 58% decline in tuber yield (p<0.05). The variation in performance between cultivars assessed in this study, reflects what is seen in the general literature. What is clear from the present study is that, there is a substantial interaction between environment/cultural practice and genotype. As such, it seems impossible to generalize that Intermediate vine harvesting is beneficial for vine production in the cultivars studied. It should be borne in mind that this practice may also be associated with a substantial decline in tuber yield in some cultivars. Thus, results should not be extrapolated to other varieties without investigation

Sweet potato (Ipomoea batatas) vine silage: A cost-effective supplement for milk production in smallholder dairy-farming systems of East Africa?

Context: Dairy production in East Africa is dominated by smallholder production systems, but is dogged by suboptimal milk production mediated by poor nutrition. Grain-based concentrates can be used to make the energy and protein deficits in rain-fed systems, but this strategy faces several hurdles. For livestock production systems to be sustainable, it is important that less human-edible food is fed to animals and sweet potato can serve both as a source of human food (tuber) and animal feed (vines). Smallholder scale-appropriate technology has been used to allow feed preservation of the perishable sweet potato vines for use throughout the year. Aims: We assessed the efficacy of sweet potato vine silage plus wheat bran (SPVSWB) as a supplement to maintain milk production at a lower cost than that of grain-based commercial dairy concentrate (CDC). Methods: Multiparous Holstein–Friesian cattle (n = 12) were given a basal diet of Napier grass (Pennisetum purpureum cv. South Africa), ad libitum, plus a fixed amount of either SPVSWB or CDC, (designed to be both isonitrogenous and iso-caloric) during late (LL) and early (EL) lactations. Key results: Daily milk yield was lower for SPVSWB than for CDC groups, although comparable (not significant), in both LL (6.2 vs 7.5 L/day) and EL (14.2 vs 16.0 L/day); however, the lower cost of production for SPVSWB (23.2 vs 48.7 KES/kg DM) ensured that margins on milk income over feed (per cow per day) were greater for SPVSWB in both periods. (LL: 71 vs 14.5; and EL: 426 vs 400 KES/day). The lower intake for SPVSWB than for CDC is most probably due to high neutral detergent fibre content in the supplement and the lower milk production, owing to either, or both, of lower energy and protein intake. Conclusions: It is suggested that some reformulation of SPVS, replacing in part or in whole the Napier grass with rejected sweet potato tubers, will decrease the neutral detergent fibre content, increase the metabolisable energy content, reducing the need for additional wheat bran and may, thereby, enhance the production response to equate with that of CDC. Implications. It is clear that, despite SPVSWB eliciting lower milk production (LL 6.2 and EL14.2 L/day) than does CDC (LL 7.5 and EL 16.0 L/day), SPVSWB is a cost-effective, accessible alternative to grain-based supplementation in small-holder dairy-farming systems of Kenya

Calculation of new enteric methane emission factors for small ruminants in western Kenya highlights the heterogeneity of smallholder production systems

Context: African livestock play a critical role in food security and the wider economy, while accounting for >70% of African agricultural greenhouse gas emissions. Accurate estimates of greenhouse gas emissions from livestock are required for inventory purposes and to assess the efficacy of mitigation measures. While there is an increasing number of studies assessing methane (CH$_{4}$) emissions of cattle, little attention has been paid to small ruminants (SR). Aims: Enteric CH$_{4}$ emissions were assessed from 1345 SR in three counties of western Kenya to develop more accurate emission factors (EF) for enteric CH$_{4}$ from sheep and goats. Methods: Using on-farm animal activity data, feed samples were also analysed to produce estimates of feed digestibility by season and region. The combined data were also used to estimate daily CH$_{4}$ production by season, location and class of animal to produce new EF for annual enteric CH$_{4}$ production of SR. Key results: Mean dry-matter digestibility of the feed basket was in the range of 58–64%, depending on region and season (~10% greater than Tier I estimates). EF were similar for sheep (4.4 vs 5 kg CH$_{4}$/year), but lower for goats (3.7 vs 5 kg CH$_{4}$/year) than those given for SR in developing countries in Intergovernmental Panel on Climate Change (Tier I) estimates. Conclusions: Published estimates of EF for SR range widely across Africa. In smallholder systems in western Kenya, SR appear to be managed differently from cattle, and EF appear to be driven by different management considerations. Implications: The findings highlighted the heterogenous nature of SR enteric emissions in East Africa, but also suggested that emissions from SR are quantitatively less important than other estimates suggest compared with cattle

A simplified approach for producing Tier 2 enteric-methane emission factors based on East African smallholder farm data

Context: Accurate reporting of livestock greenhouse-gas (GHG) emissions is important in developing effective mitigation strategies, but the cost and labour requirements associated with on-farm data collection often prevent this effort in low- and middle-income countries. Aim: The aim of this study was to investigate the precision and accuracy of simplified activity data collection protocols in African smallholder livestock farms for country-specific enteric-methane emission factors. Method: Activity data such as live weight (LW), feed quality, milk yield, and milk composition were collected from 257 smallholder farms, with a total herd of 1035 heads of cattle in Nandi and Bomet counties in western Kenya. The data collection protocol was then altered by substituting the actual LW measurements with algorithm LW (ALG), feed quality (FQ) data being sourced from the Feedipedia database, reducing the need for daily milk yield records to a single seasonal milk measurement (MiY), and by using a default energy content of milk (MiE). Daily methane production (DMP) was calculated using these simplified protocols and the estimates under individual and combined protocols were compared with values derived from the published (PUBL) estimation protocol. Key results: Employing the algorithm LW showed good agreement in DMP, with only a small negative bias (7%) and almost no change in variance. Calculating DMP on the basis of Feedipedia FQ, by contrast, resulted in a 27% increase in variation and a 27% positive bias for DMP compared with PUBL. The substitutions of milk (MiY and MiE) showed a modest change in variance and almost no bias in DMP. Conclusion: It is feasible to use a simplified data collection protocol by using algorithm LW, default energy content of milk value, seasonal single milk yield data, but full sampling and analysis of feed resources is required to produce reliable Tier 2 enteric-methane emission factors. Implications: Reducing enteric methane emissions from the livestock is a promising pathway to reduce the effects of climate change, and, hence, the need to produce accurate emission estimates as a benchmark to measure the effectiveness of mitigation options. However, it is expensive to produce accurate emission estimates, especially in developing countries; hence, it is important and feasible to simplify on-farm data collection

A simplified approach for producing Tier 2 enteric methane emission factors based on East African smallholder farm data

Context: Accurate livestock greenhouse gas (GHG) emissions reporting is important in developing effective mitigation strategies, but the cost and labor requirements associated with on-farm data collection often prevent this effort in low-and-middle-income countries. Aim: The aim of this study was to investigate the precision and accuracy of simplified activity data collection protocols in African smallholder livestock farms for country-specific enteric methane emission factors. Method: Activity data such as live weight (LW), feed quality, milk yield, and milk composition were collected from 257 smallholder farms with a total herd of 1,035 heads of cattle in Nandi and Bomet counties in Western Kenya. The data collection protocol was then altered by substituting actual LW measurements with algorithm LW (ALG), feed quality (FQ) data sourced from the Feedipedia database, reducing the need for daily milk yield records to a single seasonal milk measurement (MiY), and using a default energy content of milk (MiE). Daily methane production (DMP) was calculated using these simplified protocols and the estimates under individual and combined protocols were compared with values derived from the published (PUBL) estimation protocol. Key results: Employing the algorithm LW showed good agreement in DMP with only a small negative bias (7%) and almost no change in variance. Calculating DMP based on Feedipedia FQ, by contrast, resulted in a 27% increase in variation and a 27% positive bias for DMP compared to PUBL. The substitutions of milk (MiY and MiE) showed a modest change in variance and almost no bias in DMP. Conclusion: It is feasible to use a simplified data collection protocol by using algorithm LW, default energy content of milk value, seasonal single milk yield data, but full sampling and analysis of feed resources is required to produce reliable Tier 2 enteric methane emission factors. Implications: Reducing enteric methane emissions from the livestock is a promising pathway to reduce the effects of climate change hence the need to produce accurate emissions estimates as benchmark to measure the effectiveness of mitigation options. However, it is expensive to produce accurate emission estimates especially in developing countries, hence important and feasible to simplify on-farm data collection

Farm-level emission intensities of smallholder cattle (Bos indicus; B. indicus–B. taurus crosses) production systems in highlands and semi-arid regions

Ruminants are central to the economic and nutritional life of much of sub-Saharan Africa, but cattle are now blamed for having a disproportionately large negative environmental impact through emissions of greenhouse gas (GHG). However, the mechanism underlying excessive emissions occurring only on some farms is imperfectly understood. Reliable estimates of emissions themselves are frequently lacking due to a paucity of reliable data. Employing individual animal records obtained at regular farm visits, this study quantified farm-level emission intensities (EIs) of greenhouse gases of smallholder farms in three counties in Western Kenya. CP was chosen as the functional unit to capture the outputs of both milk and meat. The results showed that milk is responsible for 80–85% of total CP output. Farm EI ranged widely from 20 to >1 000 kg CO$_{2}$-eq/kg CP. Median EIs were 60 (Nandi), 71 (Bomet), and 90 (Nyando) kg CO$_{2}$-eq/kg. Although median EIs referenced to milk alone (2.3 kg CO$_{2}$-eq/kg milk) were almost twice that reported for Europe, up to 50% of farms had EIs comparable to the mean Pan-European EIs. Enteric methane (CH$_{4}$) contributed >95% of emissions and manure ∼4%, with negligible emissions attributed to inputs to the production system. Collecting data from individual animals on smallholder farms enabled the demonstration of extremely heterogeneous EI status among similar geographical spaces and provides clear indicators on how low EI status may be achieved in these environments. Contrary to common belief, our data show that industrial-style intensification is not required to achieve low EI. Enteric CH$_{4}$ production overwhelmingly drives farm emissions in these systems and as this is strongly collinear with nutrition and intake, an effort will be required to achieve an “efficient frontier” between feed intake, productivity, and GHG emissions

Weight gain and enteric methane production of cattle fed on tropical grasses

Context: Planted grasses are becoming an increasingly important feed resource for tropical smallholder ruminant production; yet, limited research has been conducted to quantify productivity or enteric methane (CH$_4$) production of animals consuming these grasses. Aim: An experiment was conducted to assess yields and nutritional attributes of the following three tropical grasses: Cenchrus purpureus var. Kakamega 1 (Napier), Chloris gayana var. Boma (Rhodes) and Urochloa brizantha var. Xaeres (Brachiaria), and quantify enteric CH$_4$ production of cattle fed on them. Methods: Yearling Boran steers (n:18; initial liveweight 216 ± 5.8 kg (mean ± s.e.m.) were allocated to one of three grasses, in a completely randomised design and fed ad libitum for two feeding periods, each period lasting for 70 days. Intake, liveweight (LW), apparent total-tract digestibility and enteric CH$_4$ production were assessed. The grasses used were grown on site and biomass yields were monitored over a 2-year period. Animal growth was also simulated to a final weight of 350 kg, and the amount of feed and size of land required to produce, and days to reach final weight, were estimated. Key results: Mean voluntary dry-matter intake (DMI) and ADG were higher (P 0.05) within period. Methane yield (MY; CH$_4$ g/DMI kg) was similar among treatments (26.7–28.5, P = 0.26) but Napier had a higher CH$_4$ conversion factor [Ym; CH$_4$ (MJ)/gross energy intake (MJ)] than did Rhodes and Brachiaria (0.0987 vs 0.0873 and 0.0903 respectively; P = 0.013). Our modelling indicated that steers consuming Rhodes took at least 30 more days to reach the target LW, required larger land area for feed production and produced more enteric CH$_4$ than did the other two diets. Conclusion: Even though animal performance and MY among treatments did not differ, the animals had higher MY and Y$_m$ than currently estimated by the Intergovernmental Panel on Climate Change. Implication: The three grasses supported similar animal growth rate, implying that growing of higher-yielding grasses such as Napier offers an opportunity to optimise land productivity in the tropics. However, suitable feeding practices such as protein supplementation need to be explored to enhance ruminant production and reduce enteric CH$_4$ production

Vines of the sweet potato (Ipomea batatas): A valuable feed supplement for ruminants in small holder systems

Availability of suitable feed, and in particular sources of protein-rich food, is a major constraint to increasing the productivity of smallholders in sub-Saharan Africa it is difficult to justify diverting land from growing crops for human consumption. The roots of the sweet potato are a high energy cash crop, and the leaves and vines (SPV), usually treated as rubbish, are high in protein and have been identified as a valuable livestock feed