The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform

Izak Hofmeyr - One of the best experts on this subject based on the ideXlab platform.

  • The importance of selection and good genetics
    2016
    Co-Authors: Izak Hofmeyr
    Abstract:

    During a recent visit to Zambia, the positive effects of prudent selection, combined with the use of superior bulls, were illustrated beautifully in a cow herd of 4 000. Stockfarm was invited along when well-known Beefmaster stud breeder, Frans Odendaal of WO Beefmasters, and cattle farmer Chippie Watson from Underberg in KwaZulu-Natal, travelled to select replacement heifers for Zambezi Ranching and Cropping (ZRC), a farming enterprise some 45km north-east of Lusaka.

  • The importance of selection and good genetics : on the farm
    2016
    Co-Authors: Izak Hofmeyr
    Abstract:

    During a recent visit to Zambia, the positive effects of prudent selection, combined with the use of superior bulls, were illustrated beautifully in a cow herd of 4 000. Stockfarm was invited along when well-known Beefmaster stud breeder, Frans Odendaal of WO Beefmasters, and cattle farmer Chippie Watson from Underberg in KwaZulu-Natal, travelled to select replacement heifers for Zambezi Ranching and Cropping (ZRC), a farming enterprise some 45km north-east of Lusaka.

  • The importance of selection and good genetics : production
    2016
    Co-Authors: Izak Hofmeyr
    Abstract:

    During a recent visit to Zambia, the positive effects of prudent selection, combined with the use of superior bulls, was illustrated beautifully in a cow herd of 4 000. FarmBiz was invited along when well-known Beefmaster stud breeder, Frans Odendaal of WO Beefmasters, and cattle farmer Chippie Watson from Underberg in KwaZulu-Natal, travelled to select replacement heifers for Zambezi Ranching and Cropping (ZRC), a farming enterprise some 45km north-east of Lusaka.

  • Who's the boss? : genetics & handling
    2014
    Co-Authors: Izak Hofmeyr
    Abstract:

    Aggressive behaviour and dominant hierarchies are intertwined with animals' natural survival. Therefore it is important to research and be aware of this type of behaviour, says Dr Andy Hentzen, a specialist feedlot veterinarian based in Heidelberg in Gauteng. Among others, he is a veterinary consultant for the Beefmaster feedlot near Lichtenburg.

  • Wie is baas op dié plaas
    2014
    Co-Authors: Izak Hofmeyr
    Abstract:

    Aggressiewe gedrag en dominansie-hierargie is nou verweef met die natuurlike oorlewingsbeginsels van diere, en ook van spesies. Daarom moet dit bestudeer word en deeglik daarmee rekening gehou word, verduidelik dr Andy Hentzen, 'n voerkraalspesialis-veearts wat by Heidelberg in Gauteng gebaseer is. Hy is onder andere die veeartskonsultant van die Beefmaster-voerkraal naby Lichtenburg.

Battan M. Khaemba - One of the best experts on this subject based on the ideXlab platform.

  • Resistance of Tomato Varieties to the Tomato Russet Mite, Aculops Lycopersici (Massee) (Acarina: Eriophyidae)
    International Journal of Tropical Insect Science, 1992
    Co-Authors: A. W. Kamau, J. M. Mueke, Battan M. Khaemba
    Abstract:

    There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersici Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones. Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cloud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker. Des différences significatives existent quant au degré de sensibilité des variétés de tomate testées pour la resistance à A. lycopersici Une tolérance remarquable aux dégâts foliaires a été observée sur les variétés “Early Stone Improved”, et “Beauty”. “Oxheart” et “Bonny” sur lesquelles on observe des densités faibles de mites sont aussi sensibles. La formation de boutons floraux n’est pas affectée de façon significative par les dégâts dus aux mites. Cependant, le nombre de fleurs et de boutons floraux dessechés sur les plantes infestées est significativement plus important que sur celles protegées. Le bruinissement des jeunes fruits dû aux dégâts des mites est significativement différent entre les variétés testées; et il existe une corrélation positive avec le taux d’humidité des jeunes fruits. Les variétés les plus et moins affectées sont “Beauty” et “Red Cloud” respectivement. Le pourcentage de perte en rendement est le plus élevé sur l’hybride “Beef Master” et “Oxheart” alors qu’il est le plus bas sur “Roma” et “Money Maker”.

  • Resistance of Tomato Varieties to the Tomato Russet Mite, Aculops Lycopersici (Massee) (Acarina: Eriophyidae)
    International Journal of Tropical Insect Science, 1992
    Co-Authors: A. W. Kamau, J. M. Mueke, Battan M. Khaemba
    Abstract:

    There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersici Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones. Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cloud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker.

M. L. Spangler - One of the best experts on this subject based on the ideXlab platform.

  • Economic selection index development for Beefmaster cattle II: General-purpose breeding objective.
    Journal of animal science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    An economic selection index was developed for Beefmaster cattle in a general-purpose production system in which bulls are mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Genetic parameters were obtained from the literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits 1 at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values for the objective traits calving difficultly direct (CDd), calving difficulty maternal (CDm), weaning weight direct (WWd), weaning weight maternal (WWm), mature cow weight (MW), and heifer pregnancy (HP) were -2.11, -1.53, 18.49, 11.28, -33.46, and 1.19, respectively. Consequently, under the scenario assumed herein, the greatest improvements in profitability could be made by decreasing maintenance energy costs associated with MW followed by improvements in weaning weight. The accuracy of the index lies between 0.218 (phenotypic-based index selection) and 0.428 (breeding values known without error). Implementation of this index would facilitate genetic improvement and increase profitability of Beefmaster cattle operations with a general-purpose breeding objective when replacement females are retained and with weaned calves as the sale end point.

  • Economic selection index development for Beefmaster cattle I: Terminal breeding objective 1
    Journal of animal science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    The objective of this study was to develop an economic selection index for Beefmaster cattle in a terminal production system where bulls are mated to mature cows with all resulting progeny harvested. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Phenotypic and genetic parameter values among the selection criteria and goal traits were obtained from literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values (REV) for the terminal objective traits HCW, marbling score (MS), ribeye area (REA), 12th-rib fat (FAT), and feed intake (FI) were 91.29, 17.01, 8.38, -7.07, and -29.66, respectively. Consequently, improving the efficiency of beef production is expected to impact profitability greater than improving carcass merit alone. The accuracy of the index lies between 0.338 (phenotypic selection) and 0.503 (breeding values known without error). The application of this index would aid Beefmaster breeders in their sire selection decisions, facilitating genetic improvement for a terminal breeding objective.

  • economic selection index development for Beefmaster cattle i terminal breeding objective
    Journal of Animal Science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    The objective of this study was to develop an economic selection index for Beefmaster cattle in a terminal production system where bulls are mated to mature cows with all resulting progeny harvested. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Phenotypic and genetic parameter values among the selection criteria and goal traits were obtained from literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values (REV) for the terminal objective traits HCW, marbling score (MS), ribeye area (REA), 12th-rib fat (FAT), and feed intake (FI) were 91.29, 17.01, 8.38, -7.07, and -29.66, respectively. Consequently, improving the efficiency of beef production is expected to impact profitability greater than improving carcass merit alone. The accuracy of the index lies between 0.338 (phenotypic selection) and 0.503 (breeding values known without error). The application of this index would aid Beefmaster breeders in their sire selection decisions, facilitating genetic improvement for a terminal breeding objective.

A. W. Kamau - One of the best experts on this subject based on the ideXlab platform.

  • Resistance of Tomato Varieties to the Tomato Russet Mite, Aculops Lycopersici (Massee) (Acarina: Eriophyidae)
    International Journal of Tropical Insect Science, 1992
    Co-Authors: A. W. Kamau, J. M. Mueke, Battan M. Khaemba
    Abstract:

    There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersici Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones. Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cloud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker. Des différences significatives existent quant au degré de sensibilité des variétés de tomate testées pour la resistance à A. lycopersici Une tolérance remarquable aux dégâts foliaires a été observée sur les variétés “Early Stone Improved”, et “Beauty”. “Oxheart” et “Bonny” sur lesquelles on observe des densités faibles de mites sont aussi sensibles. La formation de boutons floraux n’est pas affectée de façon significative par les dégâts dus aux mites. Cependant, le nombre de fleurs et de boutons floraux dessechés sur les plantes infestées est significativement plus important que sur celles protegées. Le bruinissement des jeunes fruits dû aux dégâts des mites est significativement différent entre les variétés testées; et il existe une corrélation positive avec le taux d’humidité des jeunes fruits. Les variétés les plus et moins affectées sont “Beauty” et “Red Cloud” respectivement. Le pourcentage de perte en rendement est le plus élevé sur l’hybride “Beef Master” et “Oxheart” alors qu’il est le plus bas sur “Roma” et “Money Maker”.

  • Resistance of Tomato Varieties to the Tomato Russet Mite, Aculops Lycopersici (Massee) (Acarina: Eriophyidae)
    International Journal of Tropical Insect Science, 1992
    Co-Authors: A. W. Kamau, J. M. Mueke, Battan M. Khaemba
    Abstract:

    There were significant differences in the level of susceptibility among the 12 varieties which were screened for resistance to A. lycopersici Pronounced tolerance to leaf damage was recorded on varieties Early Stone Improved and Beauty. Oxheart and Bonny Best both of which had comparatively lower mite densities were highly susceptible. Flower bud formation was not significantly affected by the mite damage. However, the number of dead flowers and flower buds on infested plants was significantly more than on protected ones. Russetting of young fruits due to mite damage differed significantly among the varieties tested, and was positively correlated with moisture content of young fruits. The least and most affected varieties were Beauty and Red Cloud respectively. The percentage yield loss was highest on Hybrid Beefmaster and Oxheart and lowest on Roma and Money Maker.

K. P. Ochsner - One of the best experts on this subject based on the ideXlab platform.

  • Economic selection index development for Beefmaster cattle II: General-purpose breeding objective.
    Journal of animal science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    An economic selection index was developed for Beefmaster cattle in a general-purpose production system in which bulls are mated to a combination of heifers and mature cows, with resulting progeny retained as replacements or sold at weaning. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Genetic parameters were obtained from the literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits 1 at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values for the objective traits calving difficultly direct (CDd), calving difficulty maternal (CDm), weaning weight direct (WWd), weaning weight maternal (WWm), mature cow weight (MW), and heifer pregnancy (HP) were -2.11, -1.53, 18.49, 11.28, -33.46, and 1.19, respectively. Consequently, under the scenario assumed herein, the greatest improvements in profitability could be made by decreasing maintenance energy costs associated with MW followed by improvements in weaning weight. The accuracy of the index lies between 0.218 (phenotypic-based index selection) and 0.428 (breeding values known without error). Implementation of this index would facilitate genetic improvement and increase profitability of Beefmaster cattle operations with a general-purpose breeding objective when replacement females are retained and with weaned calves as the sale end point.

  • Economic selection index development for Beefmaster cattle I: Terminal breeding objective 1
    Journal of animal science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    The objective of this study was to develop an economic selection index for Beefmaster cattle in a terminal production system where bulls are mated to mature cows with all resulting progeny harvested. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Phenotypic and genetic parameter values among the selection criteria and goal traits were obtained from literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values (REV) for the terminal objective traits HCW, marbling score (MS), ribeye area (REA), 12th-rib fat (FAT), and feed intake (FI) were 91.29, 17.01, 8.38, -7.07, and -29.66, respectively. Consequently, improving the efficiency of beef production is expected to impact profitability greater than improving carcass merit alone. The accuracy of the index lies between 0.338 (phenotypic selection) and 0.503 (breeding values known without error). The application of this index would aid Beefmaster breeders in their sire selection decisions, facilitating genetic improvement for a terminal breeding objective.

  • economic selection index development for Beefmaster cattle i terminal breeding objective
    Journal of Animal Science, 2017
    Co-Authors: K. P. Ochsner, M. D. Macneil, Ronald M. Lewis, M. L. Spangler
    Abstract:

    The objective of this study was to develop an economic selection index for Beefmaster cattle in a terminal production system where bulls are mated to mature cows with all resulting progeny harvested. National average prices from 2010 to 2014 were used to establish income and expenses for the system. Phenotypic and genetic parameter values among the selection criteria and goal traits were obtained from literature. Economic values were estimated by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by 1 unit, while holding the other traits constant at their respective means. Relative economic values (REV) for the terminal objective traits HCW, marbling score (MS), ribeye area (REA), 12th-rib fat (FAT), and feed intake (FI) were 91.29, 17.01, 8.38, -7.07, and -29.66, respectively. Consequently, improving the efficiency of beef production is expected to impact profitability greater than improving carcass merit alone. The accuracy of the index lies between 0.338 (phenotypic selection) and 0.503 (breeding values known without error). The application of this index would aid Beefmaster breeders in their sire selection decisions, facilitating genetic improvement for a terminal breeding objective.

  • Development of Terminal and Maternal Economic Selection Indices in Beefmaster Cattle
    2016
    Co-Authors: K. P. Ochsner
    Abstract:

    Two economic selection indices were developed for Beefmaster cattle, one for a terminal objective and one for a maternal objective. For the terminal index it was assumed that bulls will be mated to mature cows with all resulting progeny harvested. For the maternal index it was assumed that bulls will be mated to a combination of heifers and mature cows, with resulting progeny being retained as replacements or sold at weaning. National average prices from 2010 to 2014 were used to establish income and expenses for each system. Economic values were determined by simulating 100,000 animals and approximating the partial derivatives of the profit function by perturbing traits one at a time, by one unit, while holding the other traits constant at their respective means. Relative economic values for the terminal objective traits hot carcass weight (HCW), marbling score (MS), ribeye area (REA), 12 th -rib fat (FAT) and feed intake (FI) were 91.29, 17.01, 8.38, -7.07 and -29.66, respectively. Relative economic values for the maternal objective traits calving difficultly direct (CDd), calving difficulty maternal (CDm), weaning weight direct (WWd), weaning weight maternal (WWm), mature weight (MW) and heifer pregnancy (HP) were -2.11, -1.53, 18.49, 11.28, -33.46 and 1.19, respectively. Selection criteria were chosen from expected progeny differences (EPD) currently reported by Beefmaster Breeders United (BBU). Phenotypic and genetic parameter values among the selection criteria and objective traits were obtained from literature. Index coefficients for EPD of the terminal selection criteria yearling weight