Jean Hanson

Palatability of wilted and dried multipurpose tree species fed to sheep and goats

Palatability indices of dry and wilted 18 multipurpose tree species (MPTs) were determined using 12 wethers and 12 bucks (mean ± SD liveweight 17.5 ± 1.24 kg and 20.5 ± 1.46 kg, respectively), blocked into two groups on liveweight and age, housed in a roofed and half-walled shed with individual feeding pens. The 18 MPTs were randomly grouped into sets of six by form (dried and wilted), such that each animal received three samples of each form. Each animal received 0.5 kg teff straw (Eragrostis tef) in addition to 0.4 kg and 0.2 kg of the wilted and dry forms of the appropriate MPTs, respectively, daily at 08,00 h over a 12-day experimental period. Dry matter intake of MPTs on day 1 (A1), average intakes on days 2–4 (A2), days 5–8 (A3), days 9–12 (A4) and days 2–12 (A5) were compared. A significant (P < 0.0001) decrease in intake, with correlation coefficients of r = 0.92 (A1 and A2), r = 0.88 (A1 and A5) and r = 0.85 (A1 and A3) in sheep, was observed. A similar trend was observed for palatability indices R1, R2, R3 and R4. A close relationship was observed between R2 and R5 (r = 0.91), R3 and R5 (r = 0.97), and R4 and R5 (r = 0.94). R1 was poorly correlated with R5 (r = 0.61). The same trend was found in goats. Linear regressions of A5 on A1 A5 on A2, A5 on A3 and A5 on A4 (adj. r2 = 0.81, 0.95, 0.97, 0.94 and r2 = 0.64, 0.90, 0.97, 0.94 in sheep and goats, respectively) showed that the best relationship existed between A5 and A3. The results of analysis of variance for palatability index R5 showed that the palatability index significantly (P < 0.001) depended on previous clustering and animal species. The cluster means for R5 were 1.34, 1.02, 0.68 and 0.54 for clusters 1, 2, 3 and 4, respectively. However, the palatability indices for goats were more than double those for sheep (1.33 vs. 0.48). There were no significant interaction effects for cluster, form and animal species. In this study the form of feed (wilted or dry) did not affect the palatability index. Acacia persiciflora, Leucaena leucocephala and Chamaecytisus palmensis were ranked high by both sheep and goats.

Palatability of multipurpose tree species: effect of species and length of study on intake and relative palatability by sheep.

The potential forage value and appropriate length of study on intake and relative palatability ranking of 40 multipurpose tree species (MPTs) were determined using 24 sheep blocked on live weight and age. As the MPTs had different dry matter contents, intakes were also expressed as a ratio of quantity offered (Ai/Di). Using daily Eragrostis tef straw offer (TD) and intake (T), relative palatability indices were calculated as Ri = (Ai/Di)/(Ti/TDi).There was a significant (P < 0.0001) decrease in correlation of intake measured in day 1 and subsequent days (r = 0.88, 0.81 and 0.79 for days 2–4, days 5–8 and days 9–12, respectively). A similar trend was observed on corresponding palatability indices. Individual animal preference and blocking did not affect intake and palatability indices significantly (P > 0.05), however significant (P < 0.0001) tree species differences were observed. Results on linear regression, correlation coefficients, palatability ranking and standard errors of means (adjusted palatability indices) indicate that, if palatability is done to predict long-term intake of MPTs, at least 5 days are appropriate in palatability assessment for sheep.Using mean palatability index (days 2–12), the MPTs were grouped into four clusters. The MPTs such as Leucaena leucocephala and Sesbania sesban which are known to have good nutritive value had high palatability. In the same classification group, there were less known species such as Acacia venosa, A. persiciflora, A. melanoxylon, A. hockii, A. polycantha, Tamarindus indica, Chamaecytisus palmensis, Tipuana tipu, Indigofera arrecta and Atriplex nummularia. Flemingia macrophylla, Erythrina abyssinica, Acacia salicina, Acacia coriacea, Albizia schimperiana, Ceratonia siliqua, Casuarina glauca and Erythrina burana had poor palatability. These species seem to have little forage value for animals with short-term adaptation periods. Gliricida sepium and Calliandra calothyrsus although currently being used by farmers had a medium palatability ranking.

Characterisation of germplasm accessions of Napier grass (Pennisetum purpureum and P. purpureum x P. glaucum hybrids) and comparison with farm clones using RAPD

Fifty six germplasm accessions of the important East African fodder crop Napier grass, Pennisetum purpureum, and its hybrids with P. glaucum, were characterised using 67 random amplified polymorphic DNA (RAPD) fragments. No or very low intra-accession variation was found for 49 of the accessions examined, confirming field observations that this species is predominantly clonally propagated. Comparison of intra and inter-accession variation identified several groups of identical/similar accessions that could be targeted if the collection is to be rationalised, and also highlighted two misplantings of germplasm material during transfer to a field trial site. A neighbour joining dendrogram of Jaccards similarity estimates, clearly separated 50 accessions of P. purpureum from three P. glaucum individuals, and placed six hybrid accessions in an intermediate position. These groupings were well supported by a nested AMOVA (P<0.001; 29.5% of total variance due to taxonomic delineation). The main group of P. purpureum individuals could be further differentiated into five sub-groups (designated East Africa, Southern Africa, USA1, USA2 and Miscellaneous, to reflect the majority membership of sub-groups) and examination of the within P. purpureum component of the nested AMOVA, found them to be significantly different (P<0.001; 18.8% of variance). Genetic diversity across all accessions was found to be fairly high (Shannons diversity index 0.306) and thus the collection probably represents a wide genetic base for this species. In addition to germplasm accessions, 25 Kenyan farm clones were also analysed. A principal coordinate analysis found that all but one of the clones clustered with the main P. purpureum group of accessions, indicating that the majority are probably not interspecific hybrids. The origin and pedigree of clones is discussed based on genetic similarity amongst clones and to germplasm accessions.

Determining Sources of Diversity in Cultivated and Wild Lablab purpureus Related to Provenance of Germplasm by using Amplified Fragment Length Polymorphism

To improve understanding of diversity of Lablab purpureus and establish relationships among 103 germplasm accessions collected from diverse geographic origins, amplified fragment length polymorphism markers were used. Four primer sets selected out of 16 produced 289 clear, repeatable polymorphisms. UPGMA analysis of similarity data clustered the accessions according to their subspecific taxonomic organization, i.e., subsp. purpureus and subsp. uncinatus, as well as to cultivated and wild forms. The well-represented landraces from Africa and Asia, belonging predominantly to subsp. purpureus, displayed moderate genetic diversity. Wild forms from Africa showed far greater levels of diversity that would justify taxonomic re-assessment of the wild subsp. uncinatus. The molecular analysis identified forms that were collected in the wild in India but were genetically placed intermediate between wild and cultivated forms. As these plant types did not exist among the African accessions, it is suggested that they might represent escapes from early attempts of domestication. These results support the suggested pathway of domestication and distribution of L. purpureus from Africa to Asia. Additional members to a previously published core collection of the species are proposed.

Acacia angustissima: its anti-nutrients constituents, toxicity and possible mechanisms to alleviate the toxicity - a short review.

In most tropical countries poor nutrition limits ruminant productivity. The main feed resources include native pasture and crop residues, which are low in nitrogen (6.2-10.6 g/kg DM) and high in fibre (676-772 g/kg DM). Nutritional deficiencies of these feeds can be alleviated by supplementation with fodder trees such as Acacia angustissima, which are multipurpose, have outstanding agronomical attributes and are rich in nitrogen (33.2-40.8 g/kg DM). However, feeding A. angustissima without adaptation caused toxicity to sheep. Rats fed diets containing 20% A. angustissima died within 2-5 d. Intake and average daily gain (6.0 and 0.5 g/d) were significantly (P 0.05) reduced in rats fed a diet containing 70% acetone extract compared to the rats fed the control diet (8.8 and 3.1 g/d). Addition of polyethylene glycol (PEG) improved in-vitro gas and ammonia production from A. angustissima leaves (gas, 3.9 to 13.4 ml/100g DM; ammonia, 2.8 to 8.5 mM). PEG also increased DM intake (696 and 860 g /d) in sheep fed A. angustissima. These results suggested that tannin contributed to the negative effects of A. angustissima. Non-protein amino acids (4-N-acetyl-2, 4-diaminobutanoic acid, acetyl diaminopropionic acid, oxalyl diamino butyric, oxalyl diaminopropionic) have also been isolated from A. angustissima leaves. Feeding A. angustissima to sheep by gradually increasing levels in the diet prevented toxicity. Additionally, transfer of rumen contents from adapted to non-adapted sheep prevented toxicity of A. angustissima. These observations suggested that adaptation was at the microbial level. Current work to alleviate the toxicity of A. angustissima is therefore focused on microbial adaptation and detoxification. Tannin-tolerant bacteria have been isolated from sheep adapted to A. angustissima and free-ranging animals. Work on non-protein amino acids is underway. Overcoming the negative effects of the anti-nutritional factors in A. angustissima would not only improve livestock productivity but also result in improvement of the environment.

Forage potential of Erythrina abyssinica: intake, digestibility and growth rates for stall-fed sheep and goats in southern Ethiopia

Feeding value ofErythrina abyssinica leaves were evaluated with native sheep and goats at Soddo, southern Ethiopia in a 21-day digestibility and 80-day growth trial. In the digestibility trial, wilted leaves ofE. abyssinica were fedad libitum, while in the growth trial, animals were offered a basal diet ofP. purpureum with three levels (0, 500, 1000 g/head/day) ofE. abyssinica leaf. No significant (P>0.05) differences were found between sheep and goats in voluntary intakes and digestibilities of organic matter, nitrogen and neutral detergent fiber. Supplementing a basal diet ofP. purpureum with increasing levels ofE. abyssinica leaves resulted in reduced intake ofP. purpureum, but increased total organic matter intake in both species. Liveweight gains of sheep and goats increased linearly (P<0.01) with increasing levels ofE. abyssinica leaf supplementation. Sheep gained weight faster (P<0.04) than goats.Based on the results it was concluded thatE. abyssinica has high forage potential and can effectively serve as a cheap source of protein supplement for low quality diets during the dry season for resource-poor farmers with stall-fed sheep and goats.

The effect of supplementing maize stover with cowpea ( Vigna unguiculata ) haulms on the intake and growth performance of Ethiopian sheep

This study compared the effect of supplementing maize stover (MS) with cowpea (Vigna unguiculata) haulms or commercial concentrate (CC) on feed intake, nutrient digestibility, live weight gain and carcass yield of male Ethiopian Highland sheep. Two cowpea genotypes, 12688 (forage) and IT96D-774 (dual-purpose), were used. A randomised block design was applied with groups of eight sheep, blocked by weight, allocated to one of six treatments; MS ad libitum either unsupplemented or supplemented daily with 150 or 300 g dry matter (DM) of either cowpea or CC. MS contained more neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin than either cowpeas or CC. Crude protein (CP) content of the forage-type cowpeas was higher than either dual-purpose or CC, while MS had the lowest CP content. Relative to the negative control group, cowpea at either level significantly (P < 0.01) increased both MS intake and total NDF and lignin. Supplementation significantly (P < 0.01) increased nitrogen (N) intakes relative to the negative control, with N intake for CC and dual-purpose cowpea (high level) being similar to the intakes for cowpeas at 150 g. N intake with the forage-type cowpea offered at higher levels was significantly (P < 0.01) greater than the other groups. No significant differences (P > 0.01) in MS intake were identified between cowpeas at either level or CC and, although intake level of CC increased, it did not differ significantly from the negative control group. Supplementation significantly (P < 0.01) improved average daily gain, with the negative control group losing weight over the experimental period, and increased final live weight, carcass cold weight and dressing percentage. Supplementation significantly improved the apparent digestibility of DM, organic matter and NDF, with no significant difference found between cowpeas at either level. N retention was negative for sheep offered only MS, but positive with all supplements, with cowpeas improving N retention to a greater extent than CC. Interestingly, N retention/N intake was higher with cowpeas offered at the lower level suggesting an improvement in utilisation efficiency. The results indicate that the supplementation of MS with cowpea enhanced ruminant production through improvements in digestibility and intake. Further, as production improvements associated with the two levels of supplementation did not differ significantly, it is suggested that where limited quantities of cowpea are available, it may be of greater nutritional benefit to offer smaller quantities over an increased number of animal days.

Differences in Sesbania sesban accessions in relation to their phenolic concentration and HPLC fingerprints

Phenolic concentration in the leaves from 103 different accessions of Sesbania sesban (L) Merr was determined and HPLC was used to analyse the extractable phenolics. The chromatograms were subjected to cluster analysis. Large variation was observed between accessions in the soluble phenolic and insoluble proanthocyanidin concentrations. The study further showed that the accessions could be grouped on the basis of their HPLC fingerprints. The results suggest that quantitative and qualitative selection for polyphenolics is possible. This type of information is relevant to future programs aimed at the improvement of the nutritive value in Sesbania sesban.

Wheat growth as influenced by application of agroforestry-tree prunings in Ethiopian highlands

The response of wheat (Triticum aestivum cv. ‘Enkoy’) to application of leaf prunings of nine agroforestry-tree species was investigated in a field trial and a six-week pot trial. The tree species were Grevillea robusta, Erythrina abyssinica, Gliricidia sepium, Albizia schimperiana, Acacia nilotica, Acacia polyacantha, Leucaena leucocephala, Leucaena pallida and Entada abyssinica. L. leucocephala, L. pallida, G. sepium and Entada abyssinica proved to be good pruning sources in the pot trial. G. robusta, A. polyacantha, A. nilotica and E. abyssinica had adverse effects on wheat seedlings with increased pruning loads probably due to immobilization processes or allelopathic effects. N and lignin content, C/N ratio, lignin/N ratio, phenolics/N ratio and (phenolics + lignin)/N ratio of the pruning material were all significantly correlated with shoot dry matter production of the wheat seedlings. With the exception of Entada abyssinica, which performed well under field conditions, a similar ranking as in the pot trial was established in the field experiment, but at harvest differences were not as pronounced as in the pot trial. Gliricidia treated wheat produced by far the highest grain yield with 248 g/m2.

Genetic diversity in Napier grass (Pennisetum purpureum) cultivars: implications for breeding and conservation

Napier grass is an important forage for smallholder dairy farms. However, there has been a comparatively low effort to improve Napier grass. It is necessary to strengthen forage breeding programs for development of cultivars with superior traits like. With a high rich gene pool; correct identification of Napier grass accessions is a prerequisite because the existing germplasm information is scanty and cannot be relied upon for crop improvement. Thus the genetic assessment of various Napier grass accessions from the Eastern Africa region is important for correct cultivar identification in order to fully exploit them in crop improvement strategies.