摘要:

The potential benefits of cloning domestic animals in animal breeding and production are considered. It is concluded that cloning will not make a significant contribution to increasing the rate of genetic gain in selection programmes. It seems that only marginal advantages can be derived from the use of cloning in other areas of livestock production. If costs are reduced and embryo transfer technology continues to advance, the dissemination of genetic material in the form of cloned embryos could be a reality. It will lead to the introduction of greatly increased risk in animal production and the consequences can be substantial.

ISSN:0906-4702    

DOI:10.1080/09064709709362388

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Estimates of posterior distributions of genetic and phenotypic parameters and functions of them for individual test day milk yield are obtained for 28 873 British Holstein‐Friesian heifers, the progeny of 40 proven and 649 unproven sires, using restricted maximum likelihood (REML) and Gibbs sampling methods with a univariate sire model. Results from the two methods are then compared. It is found that the posterior expectations and REML estimates of the parameters are fairly similar. The marginal posterior expectation and REML estimate of heritability for lactation milk yield are 0.49 and 0.50, respectively. Heritability estimates for individual test day records range from 0.27 to 0.40, whilst the posterior expectations are between 0.28 and 0.42. Generally, heritabilities for test day records were lowest at the start and highest in the second half of the lactation. Gibbs sampling requires substantially more computing than REML estimation, but provides a more informative analysis.

ISSN:0906-4702    

DOI:10.1080/09064709709362389

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Estimates and posterior distributions of genetic and phenotypic variance matrices for test day milk records are obtained for 23 873 British Holstein‐Friesian heifers, the progeny of 40 proven and 649 unproven sires, using restricted maximum likelihood (REML) and Gibbs sampling methods with two different prior specifications in a multivariate sire model. Results from the two methods are then compared. The REML estimates and posterior expectations of heritability and individual test day records range from 0.28 to 0.42. Generally, heritabilities for test day records are lowest at the start and highest in the second half of the lactation. Estimates of genetic correlations between test day milk yields range from 0.59 to 0.99, whilst those of phenotypic correlations are between 0.30 and 0.76, the correlations being highest for adjacent tests. Bayesian inferences are more informative, but require much more computer time.

ISSN:0906-4702    

DOI:10.1080/09064709709362390

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Variation in ultrasonic scanning measures, muscularity scores and body measures was studied. Ultrasonic scanning measurements of a cross‐sectional area of m. longissimus dorsi were recorded for 137 Swedish Red and White (SRB) and 246 Swedish Friesian (SLB) performance‐tested bulls. Estimated heritabilities were 0.49 for SRB and 0.36 for SLB. Body measures and muscularity scores were recorded for 638 performance‐tested SLB bulls that were divided into two age groups. Estimated heritabilities for most of the body measures and muscularity scores were between 0.2 and 0.7. Heritabilities were larger for traits expressing height than width or length of the body and larger also for older bulls. The predictive value of body measures and muscularity scores on carcass traits was investigated. Carcass and muscle weight were determined principally by live weight or age at slaughter. The coefficients of determination decreased by 5 to 12% for carcass conformation and 15% for dressing percentage when breed origin, muscularity scores and/or body measures were excluded from the model.

ISSN:0906-4702    

DOI:10.1080/09064709709362391

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Records of 4103 scanblack mink kits born in 1989–94 were used to estimate genetic parameters for body weight and body length during the growth season with special emphasis on the suckling period. Maternal additive and direct additive effects and effects of permanent maternal and specific litter environment were estimated, using restricted maximum likelihood (REML) in univariate and bivariate animal models. The maternal additive effect was constant during the first 4 weeks after parturition ath2m≈ 0.30 for weight, and decreased thereafter. The heritability estimate for direct additive effect for body weight decreased fromh2a≈ 0.19 at birth toh2a≈ 0.12 at 4 weeks but increased toh2a≈ 0.50 in August to December. The maternal permanent environment was important only at 2 and 4 weeks,c2p≈ 0.10. The specific environment, common within the litter, increased fromc2s≈ 0.24 at birth to c2s≈ 0.40 at 2 and 4 weeks, but decreased thereafter toc2s≈ 0.10 in December. Estimates for body length showed a slightly different pattern,h2avarying from 0.07 to 0.17 in the lactation period, but increased to 0.46 at pelting. The heritability of maternal additive effect(h2m)for body length varied from 0.17 to 0.24 during the lactation period and decreased thereafter to 0.06 at pelting.

ISSN:0906-4702    

DOI:10.1080/09064709709362392

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

Heal and total tract digestibilities of dietary components and energy in eight oat diets varying in chemical composition were studied with growing pigs in two 4×4 Latin square experiments. The diet with partially dehulled oats had the significantly(P <0.05) highest ileal and total tract digestibility of organic matter, crude protein, total fibre and energy. The metabolizable energy value of the oat batches tested varied between 15.4 and 10.9 MJ kg‐1dry matter. Significant correlations(P <0.05) were found between both total tract and ileal digestibilities of organic matter and energy, respectively, and the content of fibre components, starch, crude fat and nitrogen‐free extractives. Differences in the correlations as predictors between the content of crude fibre, total fibre, neutral detergent fibre or acid detergent fibre and the ileal and total tract digestibility of organic matter and energy, respectively, were limited.

ISSN:0906-4702    

DOI:10.1080/09064709709362393

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

摘要:

A total of 1584 Lohmann Selected Leghorn hens were kept in 144 modified cages furnished with—perch, nest and sandbath for 5, 6, 7 or 8 hens per cage or in 162 conventional cages for 4 hens. Cage floor area was 600 cm2per hen excluding nest and sandbath. Doors to nests and sandbaths were time monitored. Production, mortality, exterior egg quality, health, integument and the birds use of facilities were registered from 20 until 80 weeks. No effects of group size or keeping system on production or mortality were detected, but the furnished cage gave more cracked and less dirty eggs than the conventional cage. Hens in the furnished cage had better plumage condition, less toe pad hyperkeratosis, shorter claws, less rear body wounds and stronger humerus, but dirtier feet than hens in the conventional cage. Hens in the larger group sizes had the dirtiest feet. In the furnished cage, on average, 86% of all eggs were laid in the nests and 0.6% in the sandbaths. The rolling out efficiency from nests was best in the larger group sizes. During night less than 0.5% of the hens stayed in the sandbath and less than2%stayed in the nest. Average use of perches was 28% during the day and 91% at night. Hens in the small group sizes used the sandbath most. Dust‐bathing behaviour also occurred on the wire floor.

ISSN:0906-4702    

DOI:10.1080/09064709709362394

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0906-4702    

DOI:10.1080/09064709709362395

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor

ISSN:0906-4702    

DOI:10.1080/09064709709362387

出版商:Taylor & Francis Group    

年代:1997

数据来源: Taylor