A biotyping scheme for Salmonella livingstone

Salmonella livingstone is one of the more common salmonella serotypes isolated in the United Kingdom. The characterization of 70 different isolates of S. livingstone using biochemical tests and plasmid profile analysis is described. The isolates could be divided into four groups by their ability to grow in d-tartrate, l-tartrate and Stern's glycerol. Further subdivision was achieved by the use of plasmid profile analysis; 24 of the isolates possessed light plasmids (less than 9.5 MD) and four possessed heavy plasmids (greater than 30 MD). The combination of biotyping and plasmid profile analysis can be used as the basis of a scheme to 'fingerprint' S. livingstone for epidemiological studies.     

The Effects of Replacing Dicalcium Phosphate with Busumbu Rock Phosphate on Performance and the Mechanical Properties of Bone in Growing Chicks

Three hundred, day-old broiler chicks, with an average initial weight of 41.8±1.79 g, were used in a 15-day study (10 birds per battery cage) to characterize their performance and fluorine status when dicalcium phosphate (DCP) was replaced by Busumbu rock phosphate (BRP) as the source of phosphorus in the chicks' ration. The treatments comprised a standard ration with BRP replacing 0, 25%, 50%, 75% or 100% of DCP. Replacing DCP with BRP significantly reduced the final weight of the chicks (p<0.01), feed intake (p<0.01), weight gains (p<0.01) and dry matter digestibility (p<0.05) but increased (p<0.05) the feed-to-gain ratio. True phosphorus absorption and the percentage of phosphorus in the tibia were not affected by increasing amounts of BRP in the diet. Increasing levels of BRP in the diet linearly reduced (p<0.01) the percentage bone ash, calcium, Ca:P ratio, ultimate breaking force, bending moment, stress, and modulus of elasticity. Leg stiffness, lameness, reduced feed intake, and a decline in general health were recorded in 10–40% of the chicks on 75% and 100% BRP, respectively. These results suggest that excessive ingestion of fluorine from the BRP caused the reduction in the chicks' performance.     

Leishmania major infections in Phlebotomus duboscqi fed on murine models immunized with L. major subcellular antigens and sandfly gut antigens

The ability of antibodies in bloodmeals of mice and hamsters immunized with Leishmania major subcellular fractions and sandfly (Phlebotomus duboscqi) gut antigens to inhibit development of L. major in its vector P. duboscqi was examined. Antibodies from animals immunized with either L. major subcellular fractions alone or sandfly gut antigen alone were not very effective in inhibiting development of L. major in the sandfly. When P. duboscqi were fed on blood from animals immunized with both parasite flagella and sandfly gut antigen, development of L. major was significantly inhibited (P<0,05). Control sandflies fed on naive animals displayed a normal pattern of parasite development to the metacyclic stage. Electron microscopy studies showed that one of the mechanisms through which antisandfly gut antibody can cause inhibition of parasite development is by lysing sandfly gut epithelium. This study has demonstrated that it is possible to reduce transmission of leishmaniosis through immunization against both the parasite and its sandfly vector.     

Effects of supplementing fish oil in the drinking water of dairy cows on production performance and milk fatty acid composition

The objective of this study was to determine the effects of supplementing fish oil (FO) in the drinking water of dairy cows on production performance and milk fatty acid composition. Sixteen multiparous Holstein dairy cows (741 +/- 84 kg of BW; 60 +/- 2.3 d in milk, mean +/- SD) housed in a tie-stall facility were used in the study. The study was conducted as a completely randomized design with repeated measurements. The cows were blocked by days in milk and allocated to 1 of 2 treatments: 10 g of menhaden FO/kg of DM top-dressed on the total mixed ration (FOT), and 2 g of menhaden FO/L delivered in the drinking water (FOW). The trial lasted for 5 wk: a 1-wk pretreatment adjustment period and 4 wk of treatment. The animals were fed and milked twice daily (feeding at 0830 and 1300; milking at 0500 and 1500) and had unlimited access to water. Dry matter intake (21.3 kg/d for FOT vs. 22.7 +/- 0.74 kg/d for FOW), milk yield (38.2 kg/d for FOT vs. 39.5 +/- 1.9 kg/d for FOW), and water intake (101 L/d for FOT vs. 107 +/- 4.4 L/d for FOW) were not affected by treatment. The mode of delivery of FO had no effect on milk fat percentage, but milk fat percentage declined linearly with time. The fatty acid contents of 7:0; 8:0; 9:0; 10:0; 12:0 in the milk of FOT cows were lower than for FOW cows, whereas 18:1 trans-12; 18:1 trans-13 and 14; 18:1 trans-16; and trans-9, trans-11 plus trans-10, trans-12 CLA were greater for FOT than for FOW. The contents of 24:1 in the milk of FOW cows were 48% greater than for FOT cows, although the concentrations were low in both groups. There was a tendency for the contents of 14:0 and 22:5n-6 to be greater in FOW cows than FOT cows and for the contents of iso-18:0 to be lower for FOW cows than for FOT cows. Although it appears that the amount of FO added in the study did not bypass the rumen as hypothesized, these results suggest that drinking water can be an alternative for supplementing FO to dairy cows without decreasing feed or water intake relative to cows fed FO in the diet.     

Diallel analysis of grain yield and resistance to seven diseases of 12 African maize (<Emphasis Type="Italic">Zea mays</Emphasis> L.) inbred lines

Maize (Zea mays L.) is grown on 15 million ha in eastern and southern Africa. Several diseases are of common occurrence in the region and regularly result in significant yield losses. A collaborative regional disease nursery (REGNUR) project was initiated in 1998 to identify and increase access to disease resistant germplasm, generate and disseminate information on disease and insect resistance sources, and facilitate the development of resistant cultivars by project partners. A diallel among 12 elite inbred lines was formed with the specific objective of evaluating the combining ability of these inbred lines for grain yield and resistance to seven diseases. The trial was grown at six sites in 2001. Results showed that both general (GCA) and specific combining ability effects were significant for most diseases. On the average, GCA accounted for 69% of resistance to diseases and only 37% of variation for grain yield. Correlations between GCA effects for disease scores were generally non-significant, implying that it is possible to pyramid genes for disease resistance in inbred lines. This underscores the need for screening for resistance to prevailing diseases using artificial inoculation or reliable hot-spots. Based on GCA effects for grain yield and across diseases, P12 and P6 were the best inbred lines. The crosses P4 × P9 (6.7 t ha⁻¹) and P4 × P12 (6.9 t ha⁻¹) were the best hybrids in the earlier maturity group, while P3 × P9 (8.3 t ha⁻¹) and P2 × P8 (7.4 t ha⁻¹) were the best hybrids in the late maturity group.     

Effects of mild heat stress and grain challenge on acid-base balance and rumen tissue histology in lambs

The effect of heat stress (HS) and grain challenge (GC) on acid-base balance and rumen tissue histology in lambs was investigated using 24 yearling wether lambs (58 +/- 4.5 kg of BW) in a 2 x 2 factorial experiment with repeated measures for day (10, 14, and 17) of sampling. The factors were temperature [thermoneutral zone (TN) vs. HS] and diet (control vs. GC). Lambs were blocked by BW and assigned to 1 of 4 treatments in temperature-controlled rooms: 1) TN (temperature = 18 to 20 degrees C; relative humidity = 30%; 2) TN + GC; 3) HS (temperature = 35 degrees C for 9 h/d, 20 degrees C for 15 h/d; relative humidity = 40%); and 4) HS + GC. Venous blood samples were collected at 1800 on the first day of GC (d 10), in the middle of GC (d 14), and at the end of the trial (d 17) by jugular venipuncture and analyzed for pH, gases, hematocrit, plasma ions, and total protein. After all measurements in live animals were taken on d 17, lambs were slaughtered, and tissue samples were obtained from the ventral sac of the rumen for histological assessment. Except for the concentration of plasma glucose (P = 0.04) and total protein (P < 0.01), there were no (P > 0.05) diet x temperature interactions. With HS, the concentration of Na+ and Cl- in the control group decreased at d 14 and then increased by d 17, and respiration rates in the control group decreased linearly (P < 0.05). Compared with the control group, respiration rates and the concentration of Cl- in the GC lambs increased linearly over time, whereas the concentration of Na+ decreased linearly (P < 0.05) across time. Under HS, the partial pressure of carbon dioxide, total carbon dioxide, the partial pressure of oxygen and oxygen saturation, and the concentration of Mg2+, glucose, and HCO3- showed quadratic (P < 0.05) responses with time. In both treatments, DMI, base excess of extracellular fluid, base excess of blood, and standard bicarbonate increased linearly (P < 0.05), and hematocrit, plasma protein, Ca2+, anion gap, and plasma strong ion difference decreased linearly (P < 0.05) across day. Compared with the control group, the GC group had decreased papillae count in the ruminal ventral sac (1.3 vs. 1.5; P < 0.05). These results suggest that under HS the acidifying effects of GC on acid-base balance in lambs were counteracted in the short-term through respiratory adaptation.     

Adaptation and stability analysis of sweet potato varieties for low-input systems in Uganda

Sixteen sweet potato varieties were evaluated for fresh storage root yield in 20 trials during 2000–2001 for three seasons in four locations in Uganda. Of the 16 varieties, 11 were developed by farmers and five by a central breeding programme. The behaviour of the varieties was quantified in terms of wide adaptation (genotypic mean across trials), specific adaptation (genotypic predictions for specific locations) and stability (Shukla stability variance). With respect to all three aspects of yield behaviour, farmer varieties performed on average better than the official varieties. The results illustrate the potential that farmer varieties can have in the improvement of sweet potato in Uganda and other regions where high diversity of sweet potato landraces exists.     

Introduction of the System of Rice Intensification in Kenya: experiences from Mwea Irrigation Scheme

There are various avenues for intensifying agricultural production, the most common being increased use of fertilizers, supplemental irrigation of crops, and adoption of high-yielding varieties. These options are rather widely known to farmers around the world, but they have not been widely adopted by smallholders in sub-Saharan Africa. The low adoption rate is related to complex technical and socio-economic issues, such as poor extension services, lack of capital, failure to mobilize the requisite water, or simply, poverty. The System of Rice Intensification (SRI) is in a special category of innovation in that, farmers stand to gain multiple benefits from its use, including the possibility of increasing rice yields substantially, saving water, and getting better grain quality, using differently the assets that they already have. A major impediment for the adoption of SRI in Africa has been lack of knowledge about this intervention, especially for farmers already practicing irrigated agriculture. Farmers generally have good business sense and will adopt technologies or practices once the benefits are proven and the risks are seen as minor. SRI should be attractive for these reasons, but there are various issues to be resolved before large numbers of farmers can adopt the method. This article reports on the steps taken and the technical and socio-economic issues addressed in efforts to introduce SRI and promote it in Kenya, specifically in the Mwea Irrigation Scheme. A diverse set of individuals and institutions in Kenya together embarked on the evaluation and dissemination of SRI methods in this East African country beginning in July 2009. If the new methods can perform in Kenya as in other countries, this will bring much benefit to rice farmers and rice consumers in the region. SRI is coming to Kenya relatively late, as it was the thirty-ninth country from which favorable SRI results have been reported. This means that Kenyans can learn from others’ experience and evaluations, and there is also now more of a supportive institutional framework. The initial results from on-farm SRI trials have been positive, although not conclusive. They have given impetus to Kenyan farmers and institutions to collaborate within a multi-sectoral, multi-level coalition that has provided an informal, multi-faceted platform for the evaluation, adaptation and dissemination of SRI practices. The initiative in Kenya is now gaining more formal status and more resources. This experience is presented to show the kinds of things that have been and can be done to utilize the SRI opportunity for raising land, labor, and water productivity in the rice sector.