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On a effectué une expérience de sélection massale sur la vitesse de croissance entre le sevrage (30 j) et 77 j dans une souche de lapin. La souche sélectionnée se composait de 12 mâles et 60 femelles pendant les 4 premières générations puis de 8 mâles et 40 femelles pendant les 4 suivantes. La souche témoin se composait aussi de 8 mâles et de 40 femelles. On a réalisé une intensité de sélection de 0,95. La vitesse de croissance postsevrage est améliorée de 6,9 g pour 8 générations, soit un progrès de 0,83 g par génération. L'héritabilité réalisée est égale à 0,23. Pour une augmentation d'un g de la vitesse de croissance post-sevrage, on observe une diminution de 0,10 du nombre de lapins vivants à la naissance par portée. Simultanément, le nombre de lapins vivants à 77 j produits par femelle mise à la reproduction a tendance à diminuer. Cette réduction de la fitness est due principalement à une diminution du nombre de femelles ayant fait au moins une portée avec un lapin vivant à 77 j. lapin -sélection -vitesse de croissance post-sevrage -taille de portée -fltness Summary -Selection experiment for post-weaning growth rate in rabbits. A selection experiment was made on the growth rate between weaning (30 days) and 77 days in a rabbit strain. There were 12 bucks and 60 does in the selected strain during the first 4 generations, then 8 bucks and l,0 does during the next 4 generations. There were 8 bucks and 40 does in the control strain. Selection intensity was 0.95. The response in post-weaning growth rate was 6.9 g after 8 generations, i.e. 0.83 g per generation. The realized heritability was 0.23. The increase in post-weaning growth rate was accompanied b an increase in 77-days body weight (58 g) and by a decrease in litter size at birth (-0.10! At the same time, the number of rabbits alive at 77 days per reproductive doe decreased. The main reason for the decrease of fitness was a decrease in the number of does with at least one rabbit alive at 77 days. rabbit -selection -post-weaning growth rate -litter size -fitness

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Heritabilities were found to be low (0.094, 0.107, 0.118, 0.160, 0.169, 0.191 and 0.201 for ES40, ES30, NEGG52, NEGG40, FL20, EYW40 and AGE.1EGG, respectively), to medium (0.327, 0.329, 0.353, 0.425

Three hundred and four female ducks of the Chinese indigenous Shan Ma breed, progeny of 11 sires and 104 dams, were used to study laying traits. Among them, 264 ducks were used to study the egg shell quality traits of eggs laid at 300 days of age. The mean age at first egg was 109 days with an average egg weight of 49.6 ± 3.7 g. Between 210 and 300 days of age, egg weight increased from 65.0 ± 3.9 g to 67.0 ± 4.2 g and the mean of the number of eggs laid up to 300 days was 161 ± 15.0. Egg length was 59.57 ± 3.01 mm and egg width was 45.02 ± 1.98 mm, leading to a shape index of 1.32 ± 0.08. Egg shell thickness was about 0.31 mm whatever the shell region, and the breaking strength was 28.80 ± 8.29 N. The heritability's estimated using restricted maximum likelihood (REML) methodology were high for egg weights (ranging from 0.43 to 0.61), intermediate for the number of eggs laid (ranging from 0.38 to 0.43), and low for the age at first egg (0.13). Heritability's for egg shell quality traits varied from 0.20 for the breaking strength to 0.44 for egg length, with in-between values of 0.28 for shell thickness and 0.34 for the shape index. The number of eggs laid was not genetically correlated with the age at first egg or egg weight, but was correlated with body weight (r g = +0.54 ± 0.23). High positive correlations were found between egg weight and body weight traits, and both of these traits (except egg weight at first egg) were highly and positively correlated with egg length and width. Breaking strength was genetically correlated with egg shell thickness (r g = +0.54 ± 0.19) and the shape index (r g = +0.71 ± 0.23). These results suggest that an efficient selection strategy could be implemented to improve the egg production of the pure Shan Ma duck line.