Growth traits of the Dorper sheep. II. Genetic and phenotypic parameters

Presents results of a study undertaken at Magogo, Kenya, to analyse genetic and phenotypic correlations between adjacent weights, between weights and rates of growth, and among growth rates themselves, hence data on 969 lambs collected over a 10-year period (1978-1987) on Dorper sheep were used in the study. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth

Growth traits of the Dorper sheep. I. Factors influencing growth traits

Data on 969 Dorper lambs collected over a 10-year period (1978 to 1987) at Ol'Magogo were used in this study. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth. All the fixed effects studied influenced growth in one way or another. Sex was highly significant for all traits (P<0.01) except growth rates between weaning and six months (GR2), and six to nine months (GR3), and season of birth influenced all traits significantly (P<0.05) except birthweight (BIRTHW), growth rates between weaning and six months (GR2), and between nine and twelve months (GR4). The effect of parity was confined to pre-weaning traits (P<0.05), while period of birth was significant (P<0.05) on all traits except yearling weight (ADJTMW) and growth rate between weaning and six months (GR2)

Growth traits of the Dorper sheep. II. Genetic and phenotypic parameters

Data on 969 lambs collected over a 10-year period (1978 to 1987) on Dorper sheep at Ol'Magogo were used in this study. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth. Heritability estimates from paternal half-sib analysis were: 0.15±0.07, 0.18±0.08, 0.39±0.11, 0.55±0.13, 0.53±0.13, 0.14±0.07, 0.28±0.09, 0.59±0.14, 0.49±0.12 and 0.49±0.12; for birthweight (BIRTHW), adjusted weaning weight (ADJWWT), adjusted six-months weight (ADJSMW), adjusted nine-months weight (ADJNMW), adjusted 12-months weight (ADJTMW), pre-weaning growth rate (GR1), weaning to six months (GR2), six to nine months (GR3), nine to 12 months (GR4), and birth to yearling (OVRGRT), respectively. Post-weaning heritability estimates were generally higher than those for pre-weaning suggesting a lower direct genetic influence early in life. Genetic and phenotypic correlations estimated between weights were mainly positive (0.15 to 0.99 and 0.02 to 0.98, respectively). There were generally high genetic and phenotypic correlations between adjacent weights, between weights and rates of growth, and among growth rates themselves

The performance of the Dorper and Dorper X Red Maasai sheep

Data on 1199 lambs collected over a 10 year period (1978 to 1987) on Dorper and Dorper X Red Maasai sheep at Ol'Magogo were used in this study. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth. In general, crossbred lambs performed better than their counterpart pure Dorpers. The Dorper X Red Maasai crosses performed significantly better than pure Dorpers in three traits namely: six months weight, twelve months weight and growth rate between weaning and six months. This superiority may be attributed to the adaptability of the Red Maasai sheep combined with the inherent fast growth rate in Dorper sheep

A comparative study of the Dorper and Dorper X Red Maasai sheep

Investigates environmental sources of variation influencing growth traits of the Dorper and Dorper X Red Maasai sheep with special reference to the relative performance of various geneotypes. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth

Growth traits of the Dorper sheep. I. Factors influencing growth traits

Presents results of a study carried out to analyse growth traits of the Dorper sheep. Data on 969 lambs collected over a 10-year period (1978 to 1987) at Magogo, Kenya were used in the study. Lamb traits studied were weights from birth to yearling and absolute growth rates between adjacent stages of growth. All the fixed effects studied influenced growth in one way or another

The need to breed crop varieties suitable for organic farming, using wheat, tomato and broccoli as examples: A review

It is estimated that more than 95% of organic production is based on crop varieties that were bred for the conventional high-input sector. Recent studies have shown that such varieties lack important traits required under organic and low-input production conditions. This is primarily due to selection in conventional breeding programmes being carried out in the background of high inorganic fertilizer and crop protection inputs. Also, some of the traits (e.g., semi-dwarf genes) that were introduced to address problems like lodging in cereals in high-input systems were shown to have negative side-effects (reduced resistance to diseases such as Septoria, lower protein content and poorer nutrient-use efficiency) on the performance of varieties under organic and low-input agronomic conditions. This review paper, using wheat, tomato and broccoli as examples, describes (1) the main traits required under low-input conditions, (2) current breeding programmes for organic, low-input agriculture, (3) currently available breeding and/or selection approaches, and (4) the benefits and potential negative side-effects of different breeding methodologies and their relative acceptability under organic farming principles. © 2010 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved