Search Results

You are looking at 1 - 10 of 77 items for :

  • "sex ratio" x
Clear All

References M. Ansari-Lari M. Saadat 2002 Changing sex ratio in Iran, 1976

Full access
Authors: Jean-Louis Arcand and Matthias Rieger

C. Alessandrini A. Volpe 2004 Influences of maternal weight on the secondary sex ratio of human offspring Human

Full access

339 354 Vala, F., Van Opijnen, T., Breeuwer, J. A. J. and Sabelis, M. W. (2003): Genetic conflicts over sex ratio: miteendosymbiont interactions. Am. Nat. 161, 254

Full access

Since early fertility decline is a permanent problem of broiler breeders, the aim of this study was to test the effects of various sex ratios, spiking strategies and additional artificial inseminations (AI) on their breeding efficiency. Six breeder flocks were analysed during the whole reproduction cycle. In Flock A the sex ratio was maintained at 10% during the whole cycle (control), while in Flock B the number of males was increased to a final ratio of 16%. In Flocks C (technological control), D, E and F the ratio of males was gradually decreased from 10% to 6.5% until the end of the cycle. Moreover, at the age of 44 weeks in Flocks D and E 50 and 100% of cockerels were replaced by young ones, respectively, while in Flock F additional artificial inseminations were applied in the second half of the reproduction cycle. The increase of sperm transport was successful only in Groups B (increase in male numbers) and D (50% replacement of old cockerels with young ones); however, it was not sufficient for increasing the fertility rates in either group. Nor did additional artificial inseminations (Flock F) have an effect on fertility. As a conclusion, it can be established that increasing the sperm count in the hens’ oviducts in any way could not improve fertility in the last third of the production cycle. The results also suggest that the expensive and labour-intensive spiking technique used in broiler breeder management is useless. The prime factor responsible for the shortened persistence of fertility may be the reduced ability of the female oviduct to accept and store sperm.

Full access

Burley, N. (1981): Sex ratio manipulation and selection for attractiveness. Science 211 :721-722. Sex ratio manipulation and selection for attractiveness Science

Full access

References W.F. Bodmer A.W.F. Edwards 1960 Natural selection and the sex-ratio

Full access

Atlantoscia floridana (van Name, 1940) (Crustacea, Isopoda, Oniscidea) in southern Brazil . Acta Oecol. 28 : 289 - 298 . Arrontes , J. 1992 . Sex-ratio variation in

Full access

Momen, F.M. (1996): Effect of prey density on reproduction, prey consumption and sex ratio of Amblyseius barkeri (Acari: Phytoseiidae). Acarologia 37, 3–6. Momen F.M. Effect of

Full access
Authors: T. Landete-Castillejos, A. Garcia, S. Langton, I. Inglis, L. Gallego and J. Garde

References Arnbom , T. , Fedak , M. A. and Rothery , P. ( 1994 ): Offspring sex ratio in relation to female size in southern elephant seals, Mirounga leonina . Behav

Full access

with sex ratios in primate groups? Proceedings of the National Academy of Sciences (USA) 99 11252 11255 . G

Full access