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by
Z.P. Yang |
Total Records (
3 ) for
Z.P. Yang |
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W. Sun
,
H. Chang
,
H.H. Musa
,
Z.P. Yang
,
K. Tsunoda
,
Z.J. Ren
and
R.Q. Geng
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Multivariate analysis was used to investigate the influence of environmental factors from animal habitat on the genetic diversity of sheep populations. Populations were classified based on their morphological features and environmental indices into 2 groups, the 1st group includes Mongolia sheep and Tan sheep, they were distributed in the pastoral and agro-pastoral area, respectively. The area was characterized by high elevation, low rainfall and low annual mean temperature. The 2nd group includes Han large-tailed sheep, Han small-tailed sheep, Tong sheep and Hu sheep, they were in agricultural area and the area was characterized by low elevation, high rainfall and high annual mean temperature. The result showed that the elevation and annual rainfall were play important role in the distribution of sheep populations. |
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D.J. Ji
,
H. Chang
,
Z.P. Yang
,
Y.J. Mao
,
L. Zhang
,
X.L. Ren
,
D.L. Wang
,
G.M. Son
and
H.Y. Chen
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Using probability matrix, the efficiencies of 4 different breeding systems, animal cloning, superovulation and embryo transfer, breeding of hybrid animals with desirable phenotype in themselves and multiple testcross, in maintaining general genetic diversity were probed while restoring Mondelian characteristics of fine breed in cattle. The results showed that the ratio between the cull rates of neighboring generations was also the ratio between inbreeding increment and the loss of genetic diversity under different systems. In the restoration of characteristics of the fine breed, system is far higher in efficiency than system III. Using the wild type and 3 mutation types of Drosophila melanogaster as subjects, the selection and breeding process were simulated and the results conformed to theoretic investigation. The findings demonstrated that, in the project to rescue fine breeds in cattle, the multiple testcross system is a better way to reshape the good Mondelian breed characteristics.
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T.P. Lanyasunya
,
H.H. Musa
,
Z.P. Yang
,
D.M. Mekki
and
E.A. Mukisira
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The relationship between
nutrition and reproduction is a topic of increasing importance. Many
research reports have clearly demonstrated that energy, protein and
minerals intake are the most important nutritional factors affecting
reproduction and therefore milk production in dairy farms. This is particularly
evident on smallholder farms in the tropics where feed is often inadequate.
On these farms, voluntary feed intake in relation to the feed required
for maintenance is the most important factor determining the animal`s
body condition. Many of the dairy animals on smallholder farms cannot
build sufficient body reserves (particularly energy and protein) due
to lack of adequate feed. As a direct consequence of feed inadequacy,
dairy stock on most smallholder resource-poor farms are often in poor
body condition (emaciated). Conception rate and calving intervals have
been shown to be highly correlated, to by weight and body condition.
The study revealed that animals with low body weights showed low conception
rate and long calving interval. Energy and protein have shown to maintain
essential levels of blood cholesterol and improve pregnancy from 42
to 72% respectively. Correlation of reproductive hormone cycle, calf
and lamb birth rates, weaning rates, lactation length and yield with
plane of nutrition, have been adequately illustrated. This is evidenced
by the current high incidences of dairy cow infertility on smallholder
farms in Kenya. Based on the literature reviewed, the current study
concluded that poor nutrition is a major contributor to the current
poor reproductive performance of dairy cows on smallholder farms. Poor
nutrition is also largely incriminated for predisposing animals to diseases
leading to high mortality and morbidity rates on these farms. It is
therefore perceived that improvement of ruminant livestock diets on
smallholder farms will greatly improve reproductive performance and
therefore herd productivity on smallholder farms. In the long run, this
will also impact positively on the economic status of the household. |
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