African
Journals Online
Transactions of the Zimbabwe
Scientific Association
VOLUME
74 (2000)
ABSTRACTS
Development of an Isoelectric Focusing Technique for
Characterising Isoenzyme Variability in Aphid Taxa
P. OTTINO, A. MATIBIRI and A. MBAYA
Biotechnology Department, Tobacco Research Board, P.O. Box
1909, Harare, Zimbabwe
Abstract
An isoelectric focusing (IEF) method was developed for
characterising differences in isooenzyme banding
patterns in aphids. In this study, 18 enzyme systems namely
adenylate kinase (AK); alkaline phosphatase (ALK-P) and acid
phosphatase (ACID-P); -amylase ( -AMY); esterase's (EST);
glucose-6-phosphate dehydrogenase (G-6-P-DeH); glutamate
oxaloacetate transaminase (GOT); -glycerophosphate dehydrogenase
( -GPD); hexokinase (HK); leucine-alanine peptidase (LeAP);
malate dehydrogenase (MTDH); malic enzyme (ME); malic enzyme
dehydrogenase (MDH); peptidase P (PEP-P); peroxidase (POD);
phosphoglucomutase (PGM); sorbitol dehydrogenase (SOD) and
tetrazolium oxidase (TOD) were screened in an attempt to identify
isoenzymes that might be useful in distinguishing between various
aphid taxa at or above the species level or within the
populations of single species. In this study the enzymes found to
be most effective in distinguishing three morphologically
distinct (but not critically identified) species of aphids
collected from tobacco, cabbage and lemon plants were ACID-P, EST
and GOT, while the remaining enzymes found to have limited
discriminating power. The method developed in this study offers a
cheap, sensitive and rapid technique for detecting expresed
genmetic differences between single aphic individuals.
Production, Fertility and Hatchability of Ostrich Eggs on a
Farm in Zimbabwe
0. MADZINGIRA1 , K. DZAMA1 AND J.H.
TOPPS2-3
1 Department of Paraclinical Veterinary Studies, University
of Zimbabwe, BoxMP167, Mount Pleasant,
Harare, Zimbabwe. e-mail: [email protected]
2 Department of Animal Science, University of Zimbabwe and
Department of Agriculture, University of
Aberdeen, Scotland.
3 Dr Topps died in January 2000 before this paper could be
published.
Abstract
The production, fertility and hatchability of 1229 ostrich
eggs from a farm outside Harare was recorded from April to
November, 1996. The average egg production and egg weight was
27.6 and 1494.6 g per hen, respectively. Egg weight at lay was
significantly affected by month of lay and hen (p<0.05). Egg
weight and number of eggs laid improved with time, reflecting an
improvement in the condition of the hen. Peak egg production and
egg weight occurred in September even though there was no
significant correlation (p<0.05)
between mean monthly egg weight and mean monthly egg
production. Even though the breeding season incorporated most of
the winter, there was no significant correlation (p<0.05)
between mean monthly temperature and egg production. The mean
weight loss from laying to hatching was 16.4% and eggs laid from
May to August tended to lose more weight than those laid from
September to November (p<0.05). It may be necessary,
therefore, to adjust the temperature and relative humidity of the
incubators accordingly rather than keeping them constant
throughout incubation. The overall fertility and hatchability was
67.1% and 46.8%, which is low. These parameters can be considered
low but can be explained by the fact that the ostriches on this
farm were generally young and that ostrich production is a
relatively new enterprise in Zimbabwe.
Attitudes of Ostrich Producers to Factors Influencing
Ostrich Farming in Zimbabwe
ROSS G. COOPER
Department of Physiology, University of Zimbabwe, P.O. Box
MP 167, Mount Pleasant, Harare
e-mail: [email protected]
Abstract
This investigation determined the attitudes of 59 producers to
the management of ostriches. The responses were mostly dependent
on question type (p<0-05) thus indicating the
management-intensive nature of ostrich production. Most
respondents agreed that ostrich fanning is productive in any area
depending on the seasonal replacement of breeding birds and on
the need to determine feed waste. The number of preferred
breeders was variable. Most did not vary the type of feed and
agreed that it must contain nutrients from usable sources and
bird weight must be controlled. Training workers and daily egg
monitoring were considered important, as was the need to herd
chicks, scrub their pens and heat them at night. The majority
agreed on the use of rough floors and rubber mate in brooder
houses to prevent chicks slipping. Most agreed on quarantining
birds prior to slaughter, developing the local market, performing
cost-benefit analyses, being totally committed, improving the
local payment system, adjusting the pricing structure, addressing
land designation policies, exporting through abattoirs and
tanneries, and on a Zimbabwean market dependence on Europe.
The Guppy Poecilia reticulata Peters,
1859 (Poeciliidae): a New Fish Species for Zimbabwe
BRIAN GRATWICKE1
Department of Biological Sciences, University of Zimbabwe,
P.O. BoxMP167, Mount Pleasant, Harare.
1 Present address: Department of Zoology,
University of Oxford, South Parks Rd.. Oxford 0X1 3PS, UK
e-mail: [email protected]
Abstract
A population of feral guppies was discovered in a dam in the
Mazowe valley. This is the first record of a wild population of
this species in Zimbabwe and it should therefore be added to the
list of fishes known from the country. It is a potentially
harmful invasive species, but its ecological impact in Zimbabwean
waters is unknown.
The Diet of Five Cichlid Fish Species from Lake Kariba,
Zimbabwe
L. MHLANGA
University Lake Kariba Research Station, P.O. Box 48,
Kariba, Zimbabwe. e-mail: [email protected]
Abstract
The diet of five cichlid fish species from the littoral areas
of Lake Kariba was investigated in 1996-97. Serranochromis
macrocephalus, Pseudocrenilabrus philander and
Pharyngochromis acuticeps fed mostly on calanoid copepods,
chironomid larvae, rotifers, phytoplankton and fish fry. Oreochromis
niloticus and 0.
mortimeri fed mainly on detritus mixed with diatoms.
There was no ontogenetic dietary shift in fish between
20-70 mm in length for any species. A dietary overlap existed
between the omnivorous species S. macrocephalus, P. philander and
P. acuticeps, and between the microphagous species 0.
niloticus and 0. mortimeri. There was no difference in gape
width between P. acuticeps and P. philander and
competition between them may be reduced by their habitat
preferences while S. macrocephalus only competes with them
as juveniles since adults switch to a piscivorous diet. Direct
competition between species 0. niloticus and 0. mortimeri
may result in the exclusion of the latter. The diets of P.
acuticeps and P. philander have changed since the
1970s reflecting the influences of Salvinia molesta that
was widespread at that time
A Model for Quantifying Sources of Variation in Test-day
Milk Yield of Holstein Cows
F.N. MHLANGA. E.F. DZOMBA and T. MAPHOSA
Department of Animal Science, University of Zimbabwe. P.O.
Box MP167, Mount Pleasant, Harare,
Zimbabwe. e-mail: [email protected]
Abstract
A cow's test-day milk yield is influenced by several
systematic environmental effects, which have to be removed when
estimating the genetic potential of an animal. The present study
quantified the variation due to test date and month of test in
test-day lactation yield records using full and reduced models.
The data consisted of 54 237 edited daily teat-day milk records
from 372 Holstein cows from Glenara Estates in Zimbabwe that were
milked between 1 May and 31 December, 1996. Three models were
used for analysis. The reduced model contained the fixed effects
of parity, days in milk, the month and year of calving and random
cow effects. The full models included either test-date or month
of test in addition to the afore- mentioned variables. Analysis
was done using the Henderson's method III in SAS (1994). Parity,
days in milk, month and year of calving, test date and month of
test all had significant effects on test-day milk yield
(p<0.001). Both test date and month of test (SS = 12 287.40).
The R-square values were 76.3%, 76.8% and 77.8% for the reduced,
full model with test date and full model with month of test
respectively. The results indicate that there is scope for
genetic improvement from use of test-day lactation records.
The Influence of Wetting Rate and Electrolyte Concentration
on the Matrix Failure Patterns of a Degraded Red Earth
W. H. VERBOOM1 and M. A. ADEY2
1 Department of Soil Science and
Agricultural Engineering, University of Zimbabwe, P.O. Box MP
167,
Mount Pleasant, Harare. Present address; Agwest, 10 Doney
Street, Narrogin 6312, Western Australia.
e-mail: [email protected]
2 Department of Agricultural &
Environmental Science, The University. Newcastle Upon Tyne, NE1
7RU,
UK.
Abstract
The hydrologic response of a degraded red earth's topsoil to
varying wetting rates (w) followed by falling
electrolyte concentration (c) was investigated. Rapid wetting
and the resulting structural failure increased total porosity and
water retention across the 0 to 1500 kPa matric potential range.
Substantial macroscopic swelling of rapidly wetted soil was
attributed to air compressed into the largest available voids.
Consequent soil matrix failure resulted in macroscopic swelling
and increased sorption of water. Hydraulic conductivity appeared
to be a non-linear function of wetting rate over the range w
= 0-30 mm min-1. Similarly, for a given wetting rate,
hydraulic conductivity increased with c, over the range
0.2-12 mmolc dm-3, according to the function log[1/Kr
– 1] = a + blogc where Kr = K(c,w)/K(12,w).
The slope b decreased as w increased indicating an
increased sensitivity to low electrolyte concentrations at high
wetting rates.
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