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Author: Tahir Usman
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659482182
Category :
Languages : en
Pages : 100
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Book Description
Dairying is a vital enterprise and important source of income generation for rural families of many developing countries of the world. Although, Holstein is imported by many tropical countries with the idea to improve the milk production but their performance in these environmental conditions is considerably low compared to the temperate environments. The expression of the inherit genetics worth differs from one environment to another and is significantly swayed by non-genetic factors. Environment and genetic (G x E) interaction plays key role in the expression of full genetic worth of an animal. The range of comfortable temperature in lactating Holstein cattle is between 4-24oC. Above 24oC, heat stress effects can be observed on the cattle, and milk yield markedly decreases above 27oC. In most of the tropical and subtropical countries the ambient temperature rises above 40 C, which is obviously suboptimal for Holstein to maintain their health and production performance. The present study was designed to investigate the effect of various environmental and genetic factors on various productive and reproductive traits of this breed under sub-tropical conditions."
Author: Tahir Usman
Publisher: LAP Lambert Academic Publishing
ISBN: 9783659482182
Category :
Languages : en
Pages : 100
Get Book Here
Book Description
Dairying is a vital enterprise and important source of income generation for rural families of many developing countries of the world. Although, Holstein is imported by many tropical countries with the idea to improve the milk production but their performance in these environmental conditions is considerably low compared to the temperate environments. The expression of the inherit genetics worth differs from one environment to another and is significantly swayed by non-genetic factors. Environment and genetic (G x E) interaction plays key role in the expression of full genetic worth of an animal. The range of comfortable temperature in lactating Holstein cattle is between 4-24oC. Above 24oC, heat stress effects can be observed on the cattle, and milk yield markedly decreases above 27oC. In most of the tropical and subtropical countries the ambient temperature rises above 40 C, which is obviously suboptimal for Holstein to maintain their health and production performance. The present study was designed to investigate the effect of various environmental and genetic factors on various productive and reproductive traits of this breed under sub-tropical conditions."
Author: Nadum Jalal Ismaiel
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Author: Claudio Napolis Costa
Publisher:
ISBN:
Category :
Languages : en
Pages : 394
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Book Description
Genetic relationships between Brazilian and U.S.A. Holstein cattle populations were studies using firstlactation 305-d ME milk and fat records of 29,413 daughters of 705 sires in Brazil and 726,932 daughters of 701 sires in the U.S.A. There were 358 sires with daughter records in both countries. Data sets consisted of all herds and low and high herds stratified by within-year standar deviation for milk (HYSD) computed within counthin country. Components of (co) variance, heritability, and genetic correlations for milk and fat yields were estimated using three data groupings: all, low and high HYDS data sets form within-country and between-country bivariete and multivariate analyses, simutaneous milk and fat yields in both countries. A sire model was solved with a restricted Maximum Likelihood (REML) derivative-free algorithm. Heritabilies for milk and fat yields using all the data were smaller in Brazil (.26 and .23) than in the in the U.S.A. (.33 and .36). Genetic correlations between milk and fat were .79 in Brazil and .62 in the U.S.A. Sire and residual variances for milk yield in Brazil were 59% and 81% (all herds), 51% and 58% (low HYSD herds), and 59% and 101% (high HYSD herds) as large as those obtained for all the U.S.A. data. corresponding percentage values for fat yield were 39% and 65%, and 48%, and 41 and 80%, respectively. Genetic correlations obtained from biavariate analyses between countries ranged from .79 to .87 for milk yield and were .89 or .90 for fat yield. Parameter estimates using all data for bibariate and multivariate analyses were essentially the same. Correlated response from sire selection using the U.S.A. information increased with average HYSD Brazil: daughter response was greatest (.77 kg/kg for milk yield and .63 kg/kg for fat yield) based on information from U.S.A. half-sisters in low HYSD herds. Unequal daughter responses from unequal genetic (co) variances under restrictive Brazilian conditions support the presence of an interaction between genetype and environment, which affects the yield expectation of daughters of U.S.A. sires performing in Brazilian herd enrironments.
Author: Jarmila Bohmanova
Publisher:
ISBN:
Category : Heat
Languages : en
Pages : 216
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Book Description
The objective of this study was to explore the genetic component of heat stress in U.S. Holsteins using national milk yield data consisting of 57 million first-parity test-day records of 6 million Holstein cows that calved from 1993 through 2004 and weather records from 202 public weather stations. Seven temperature humidity indices were compared in a humid and semi-arid climate for their ability to detect a decline of milk yield due to heat stress. The index with a higher weight on humidity was the best in the humid climate. The index with a larger weight on temperature was the best heat stress indicator in the semi-arid climate. National genetic evaluation for heat tolerance was conducted using a repeatability test-day model. Based on estimated heat tolerance PTAs, the 100 most and 100 least heat-tolerant sires were selected. For each of the 200 sires, official U.S. PTAs from February 2006 were obtained. Sires that were the most heat tolerant transmitted lower milk yields with higher fat and protein contents than did sires that were the least heat tolerant. Daughters of the most heat tolerant sires had better udder and body composition, better type, lower dairy form, slightly higher TPI, longer productive life, higher daughter pregnancy rate, were easier calving and had better persistency than did daughters of the least heat tolerant sires. Heat stress was evaluated as a factor in the genotype x environment interaction on milk production in the United States. Data for the Southeast and Northeast were extracted from the national data set and analyzed separately. Two repeatability models with and without the effect of heat stress were implemented. Both models were fitted with the national and regional data sets. Correlations between breeding values of sires with [equal to or greater than] 100 and [equal to or greater than] 300 daughters in two regions were calculated. When heat stress was ignored (first model), the correlation of regular breeding values between regions for sires with [equal to or greater than] 100 ([equal to or greater than] 300) daughters was 0.85 (0.87). Heat stress as modeled here explains only a small amount of genotype by environment interaction, partly because test day records provide only snapshots of heat stress over a hot season.
Author: Sara Elizabeth Juliette McClintock
Publisher:
ISBN:
Category : Cattle
Languages : en
Pages : 474
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Book Description
Author: Mizeck Gift Gibson Chagunda
Publisher: Cuvillier Verlag
ISBN: 9783897128521
Category : Dairy cattle
Languages : en
Pages : 114
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Book Description
Author: Ivan Campos
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Heat stress is the major issue accompanying climatic changes to all agriculture sectors. For the dairy industry, additional attention is paid, since high producing cows have lower thermal tolerance. This thesis presents the identification of temperature-humidity index (THI) thresholds where milk production starts to decrease in Ontario and Quebec, the genetic parameter estimates for heat tolerance in the Canadian Holstein population, and, the potential re-ranking of breeding values when accounting for heat tolerance in the genetic evaluation model. Average THI thresholds of 68, 60, and 57 for milk, protein, and fat yield were identified, respectively. A negative genetic correlation between general additive genetic effect and additive genetic effect for heat tolerance was observed, which shows the antagonistic relationship between production and heat tolerance. Genetic variability for heat tolerance, as well as substantial re-ranking of estimated breeding values were observed especially for high THI. Therefore, selection for heat tolerance is possible and would be particularly interesting for environments with a high average THI.
Author: National Research Council
Publisher: National Academies Press
ISBN: 0309031818
Category : Science
Languages : en
Pages : 169
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Book Description
Author: National Research Council (U.S.). Committee on Physiological Effects of Environmental Factors on Animals
Publisher: National Academies
ISBN:
Category : Science
Languages : en
Pages : 390
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Book Description
Bioclimatic factors and their measurement. Physiologic functions and measurement techniques. Animal characteristics in relation to environmental response. Environment and physiopathology. Design and execution of experiments using domestic animals. Development of research facilities. Research under field conditions.
Author: Larissa Carolina Novo
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
The availability of new technologies, as well as a greater attention to the needs ofconsumers and society, has promoted the development of novel traits in dairy cattle. However, several steps must be followed from the proposal until the implementation of novel traits into breeding programs. This process requires efforts from the definition of the new trait, exploration of the genetic basis of the trait, the development of proper methods, and finally the implementation of a national genetic evaluation. This thesis addresses different aspects of the development and implementation of novel traits, including definition of the phenotype, better understanding of the biological processes affecting the trait, identification of putative causal variants and genes, and finally a feasibility study of a national genetic evaluation. Specifically, this thesis evaluated different body temperature phenotypes as potential indicators of feed efficiency traits, investigated visceral fat deposition and its relationship with metabolic disorders, uncovered putative causal variants for periparturient hypocalcemia, and explored the implementation of a national genetic evaluation for Johne's disease. The first study showed that body temperature can be used as an indicator of feed efficiency and energy-related traits. The second study revealed that visceral fat accumulation is associated with inflammation, insulin resistance, and immune response, and its genetically linked to displaced abomasum. The third study identified genetic variants and individual genes affecting postpartum blood calcium concentration. The last study showed that a national genetic evaluation for Johne's Disease in Holsteins is feasible. Overall, this work has performed a comprehensive investigation of the different steps required for the development and implementation of novel traits in dairy cattle.
