Pattern analysis of genotype × environment interaction for striga resistance and grain yield in African sorghum trials

The parasitic weed Striga hermonthica (Del.) Benth. seriously limits sorghum [Sorghum bicolor (L.) Moench] production in Sub-Saharan Africa. As an outbreeder, S. hermonthica is highly variable with an extraordinary capacity to adapt to different hosts and environments, thereby complicating resistance breeding. To study genotype x environment (G x E) interaction for striga resistance and grain yield, nine sorghum lines, 36 F₂ populations and five local checks were grown under striga infestation at two locations in both Mali and Kenya. Mean squares due to genotypes and G x E interaction were highly significant for both sorghum grain yield and area under striga severity progress curve(ASVPC, a measure of striga emergence and vigor throughout the season). For grain yield, the entry x location-within-country interaction explained most of the total G x E while for ASVPC, entry x country and entry x location-within-country interactions were equally important. Pattern analysis (classification and ordination techniques) was applied to the environment-standardized matrix of entry x environment means. The classification clearly distinguished Malian from Kenyan locations for ASVPC, but not for grain yield. Performance plots for different entry groups showed differing patterns of adaptation. The ordination biplot underlined the importance of entry x country interaction for ASVPC. The F₂ derived from the cross of the striga-resistant line Framida with the striga-tolerant cultivar Seredo was the superior entry for both grain yield and ASVPC, underlining the importance of combining resistance with tolerance in striga resistance breeding. The observed entry x country interaction for ASVPC may be due to the entries' different reactions to climatic conditions and putative differences in striga virulence in Mali and Kenya. This revised version was published online in August 2006 with corrections to the Cover Date.     

Assessment of the socio-economic impacts associated with the arrival of apple snail (Pomacea canaliculata) in Mwea irrigation scheme,Kenya

Background

In Kenya, rice (Oryza sativa L.) is mainly produced under irrigation by small-scale farmers. Mwea irrigation scheme (MIS) in Kirinyaga County accounts for 80–88% of rice production. Here, rice is the main source of livelihood and a source of revenue generation for the county. However, a recently established invasive freshwater snail, Pomacea canaliculata (Lamarck) (family: Ampullariidae), a species of apple snail, presents a serious threat to rice production.

Results

Household surveys, focus group discussions and key informant interviews highlight apple snail as a serious problem in MIS. Households that observed at least a moderate level of infestation (>20% of cultivated area) experienced significant reductions in rice yield (~14%) and net rice income (~60%). Farmers reported increased use of chemical pesticides for management of apple snail. In addition, the cost of hired labor for physical removal of egg masses and snails is resulting in substantial negative effects on net income. Farmer age, area of land owned, responsibility for decision-making, receipt of extension advice, training, and membership of a farmer organization, were all statistically significant variables to explain farmers awareness of the need for area-wide apple snail management.

Conclusion

Strategies to limit the spread of apple snail are urgently needed. A Multi-Institutional Technical Team (MITT) has been established to spearhead management efforts and consolidate advice to farmers on how to manage apple snail. However, without action to mitigate spread, the consequences could be disastrous for rice production and food security in Kenya, and for other rice growing regions across Africa. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Genetic and phenotypic parameters and annual trends for milk production and fertility traits of the Sahiwal cattle in semi arid Kenya

Data comprising 7211 lactation records of 2894 cows were used to estimate genetic and phenotypic parameters for milk production (lactation milk yield, LMY and lactation length, LL) and fertility (calving interval, CI; number of services per conception, NSC and age at first calving, AFC) traits. Genetic, environmental and phenotypic trends were also estimated. Variance components were estimated using univariate, bivariate and trivariate animal models on based restricted maximum likelihood procedures. Univariate models were used for each trait, while bivariate models were used to estimate genetic and phenotypic correlations between milk production and fertility traits and between LMY, LL, CI and NSC within each lactation. Trivariate models were used in the analysis of LMY, LL, CI and NSC in the first three lactations. Heritability estimates from the univariate model were 0.16, 0.07, 0.03, 0.04 and 0.01 for LMY, LL, CI, AFC and NSC, respectively. The heritability estimates from trivariate analysis were higher for milk production traits than those from univariate analyses. Genetic correlations were high and undesirable between milk production and fertility traits, while phenotypic correlations were correspondingly low. Genetic trends were close to zero for all traits, while environmental and phenotypic trends fluctuated over the study period.     

The impact of Theileria parva infections and other factors on calf mean daily weight gains in smallholder dairy farms in Murang'a District, Kenya

The association between mean daily weight gain, Theileria parva infections, clinical East Coast fever and other possible determinants of weight gain were examined in a longitudinal observational study that was conducted in cohorts of female calves from five agro-ecological zone (AEZ)-grazing strata. The strata were upper-midlands (UM) 1 zero-grazing, UM 1 open-grazing, UM 2 zero-grazing, UM 4 zero-grazing and UM 4 open-grazing. In total, 225 calves on 188 smallholder dairy farms were visited within the first 2 weeks of life and thereafter at biweekly intervals up to the age of 6 months between March 1995 and August 1996. During each visit, the calves were weighed and other calf-management practices in the farm during the visit such as housing, feeding and tick control also were recorded. Other events such as morbidity and mortality between or during the visits were also recorded.

The overall mean daily weight gains were 0.24–0.29 kg (S.D.=0.17–0.22 kg) and were lower than the recommended targets for smallholder farms of 0.40–0.50 kg. The major tendency in variability of daily weight gains was due to visit-to-visit variation (especially in calves >3 months old).

Differences in mean daily gains were associated with AEZ-grazing strata and calf-level factors that included breed of calf, calf sickness, incidence of ECF, feeding of milk, concentrate feeds and minerals and interaction between calf age and AEZ-grazing strata (P<0.05). ECF and other calf sicknesses exerted a temporal effect on calf-growth at the height of illness and immediately after; calves later recovered the lost growth except where other factors such as poor calf nutrition prevailed. Improvement in calf-growth in Murang’a District is achievable and extension services should continue to target individual-calf-level management practices.     

Economic profitability of Nile tilapia (Oreochromis niloticus L.) production in Kenya

Economic profitability of Nile tilapia production in Kenya was analysed using a model that simulated individual fish growth and took fish population dynamics in the pond into account. The results suggest that the currently practiced mixed‐sex tilapia culture is economically unsustainable. It is suggested that research and extension efforts be geared towards developing monosex Nile tilapia production systems. Nile tilapia culture with African catfish predation should be viewed as an intermediate step towards all‐male Nile tilapia culture. This will allow accumulation of both physical and human capital to support all‐male tilapia culture. Under all‐male culture, economic returns are high enough to justify investment in Nile tilapia culture using borrowed capital. However, the success of monosex culture will depend on the availability and affordability of quality fingerlings and low‐cost fish feeds. The results have a wide application in Sub‐Saharan Africa where mixed‐sex Nile tilapia culture is common.     

Evaluation of a compensation scheme to bring about pastoralist tolerance of lions

Lions (Panthera leo) are in decline throughout most of their range due to human persecution, largely provoked by depredation on livestock, and there is debate as to the usefulness of financial instruments to mitigate this conflict. Intending to reduce local lion-killing, the Mbirikani Predator Compensation Fund compensates members of Mbirikani Group Ranch for livestock depredation at a flat rate (close to average market value), after the kill has been verified and with penalties imposed for poor husbandry. Despite penalizing claimants, 55% of claims arose because livestock were lost in the bush. Between 1st April 2003 and 31st December 2006, 754 cattle, 80 donkeys and 1844 sheep/goats were killed (2.31% of the total livestock herd each year). Forty-three percent of kills were ascribed to spotted hyaenas (Crocuta crocuta); leopards (Panthera pardus) and cheetahs (Acinonyx jubatus) were blamed for 37% of cases, lions 7%, jackals (Canis mesomelas) 7% and buffalo (Syncerus caffer) and elephants (Loxodonta africana) together 6%. Significantly more attacks took place during months of lower rainfall but the rate of attacks was not related to the density of livestock on the ranch, or the ratio of wild herbivores to domestic stock. There was no correlation between local market prices and the number of claims per month. Despite compensation, at least one lion per year was killed in 2004, 2005 and 2006. We describe some features of large carnivore depredation in the study area and suggest that regional recovery of the lion population may require compensation on a wider scale.     

Characterisation of smallholder pig production in Kikuyu Division, central Kenya

A three-phase study was conducted in high-potential farming and peri-urban area in Kikuyu Division central Kenya to obtain farm and management data and to monitor health and productivity of pigs in smallholder farms. The first phase was a cross-sectional study in which 87 farms (that had been selected from a total of 179 farms using a simple random selection) were visited once and data on important farm and management factors were gathered using semi-structured questionnaires. The second phase was a pilot study that was conducted in the 87 study farms for a period of 3 months to pretest the data-collection tools and to evaluate the general research methodology for the longitudinal study. The third phase was a prospective 12-month observational study in which health and productivity of pigs were monitored monthly in 76 herds that were still active and had participated in the previous studies.

The initial voluntary enrolment among the eligible farms was 99%. The median farm size was 1 acre. All the farms kept crossbreed pigs of Large White or Landrace (median nine pigs per farm). The median number of sows per herd was one. Most farmers engaged in farrow-to-finish pig-production system and most (60%) did not keep a breeding boar. The pigs were stall-fed the year round. Guard rails/piglet devices were present in 22% of the herds. Few (8%) farmers disinfected pig pens (especially the farrowing area). None of the farmers reported the use of vaccination against pig diseases. Most farmers (84 and 96%) indicated that they controlled for mange and worm infestations, respectively. To control mange, 50% of the farmers used acaricides, 34% used engine oil and 12% used both. Anthelmintics were used to control worms. No farmer had a particular control programme in place for both worms and mange. Artificial heating for piglets was not used in any of the farms. High costs of feeds (which were of variable qualities) lack of credit and genetically high-quality breeding boars and diseases were ranked highly by the farmers as the main production constraints. Thirteen percent (11/87) of farmers withdrew during the pilot study; 10 farmers had sold their pigs and one had died. Thirty-three percent (25/76) of the farms withdrew during the longitudinal study for various reasons that included death of pigs (3%; 2/76) and sale of the pigs (30%; 23/76)—mainly because of financial need.     

The impact of Theileria parva infections and other factors on calf mean daily weight gains in smallholder dairy farms in Murang’a District, Kenya

The association between mean daily weight gain, Theileria parva infections, clinical East Coast fever and other possible determinants of weight gain were examined in a longitudinal observational study that was conducted in cohorts of female calves from five agro-ecological zone (AEZ)-grazing strata. The strata were upper-midlands (UM) 1 zero-grazing, UM 1 open-grazing, UM 2 zero-grazing, UM 4 zero-grazing and UM 4 open-grazing. In total, 225 calves on 188 smallholder dairy farms were visited within the first 2 weeks of life and thereafter at biweekly intervals up to the age of 6 months between March 1995 and August 1996. During each visit, the calves were weighed and other calf-management practices in the farm during the visit such as housing, feeding and tick control also were recorded. Other events such as morbidity and mortality between or during the visits were also recorded.The overall mean daily weight gains were 0.24–0.29 kg (S.D.=0.17–0.22 kg) and were lower than the recommended targets for smallholder farms of 0.40–0.50 kg. The major tendency in variability of daily weight gains was due to visit-to-visit variation (especially in calves >3 months old).Differences in mean daily gains were associated with AEZ-grazing strata and calf-level factors that included breed of calf, calf sickness, incidence of ECF, feeding of milk, concentrate feeds and minerals and interaction between calf age and AEZ-grazing strata (P<0.05). ECF and other calf sicknesses exerted a temporal effect on calf-growth at the height of illness and immediately after; calves later recovered the lost growth except where other factors such as poor calf nutrition prevailed. Improvement in calf-growth in Murang’a District is achievable and extension services should continue to target individual-calf-level management practices.     

Evaluation of a preliminary title to protect zero-grazed dairy cattle with insecticide-treated mosquito netting in Western Kenya

The incidence of trypanosome infection was monitored in dairy cattle during a 6-month trial in Busia and Teso districts, western Kenya, to assess the efficacy of insecticide-treated netting for protection against tsetse flies. Frequently, the fragile netting did not last longer than 2 months because of destruction by strong wind or animal movements. Also, many farmers let their cattle graze freely outside the units during the day, despite technical advice, resulting in exposure of the free-ranging animals to habitats suitable for tsetse and thereby an increased risk of trypanosome infections. The trial groups thus comprised 34 animals from 11 dairy units that were continuously protected, and 153 animals from 46 dairy units that were partially protected. The control group consisted of 162 animals in 42 unprotected units. The phase-contrast buffy-coat technique was used for parasitological monitoring. The mean hazard rate for trypanosomes was significantly lower in protected cows, with a value of 0.007 as opposed to 0.02 for the control animals. Mean packed cell volumes (PCV) were significantly higher in protected cattle (29.7%) than in unprotected ones (27.6%). Farmers with protected animals also reported fewer nuisance flies and mosquitoes in their compounds.