ABSTRA CTSires heterozygous for Z sex chromosome replicates from two Golden Sebright Bantam cocks and one broiler-type male were mated to Leghorn and 1/4 Sebright dams. The sex chromosome of the broiler-type male was marked by the genes K and Id. The sex chromosomes of the Sebright Bantams were marked by the k and id genes.The K daughters of the Leghorn dams were statistically heavier than their k sisters (P<0.01) at 8 and 16 weeks of age, while the K daughters of the 1/4 Sebright dams were heavier than their k sisters (P<0.05) only at 24 weeks of age. Mature shank lengths of K daughters from both kinds of dams were significantly longer (P<0.01) than those of their k sisters. The weights and shank lengths of Id daughters of the Leghorn dams were similar to those of their id sisters.The differences between the 8-week body weights of slow and rapid feathering brothers were statistically significant for the sons of the Leghorn dams (P<0.01) and for the sons of the 1/4 Sebright dams (P<0.05). Sex dimorphism for body weight at 8 weeks of age was higher among the rapid feathering progeny of the Leghorn dams, the males being 36% heavier than their sisters.The data presented give additional evidence that a recessive sex-linked gene near the K locus is responsible for part of the small body size in the Sebright Bantams. It is suggested that this "bantam gene" is possibly an allele of the dw gene and the symbols dw + and dw B are proposed for the normal and bantam alleles.

Three egg-type stocks segregating dwarf (dw) and bantam (dwB) genes in female progeny were produced from the same 18 heterozygous (dwB/dw) sires used to inseminate dams of three different genotypes: normal (dw+), dwarf (dw) and bantam (dwB) dams. The heritability of 8-week body weight estimated from full-sibs of the same phenotype of progeny was 0.40, and that estimated from paternal half-sibs of the same phenotype (dwarf or bantam), and from the same genotype of dam was 0.38. Therefore, maternal and non-additive effects within genotypic classes of dam made little contribution to the genetic variance for 8-week body weight among their progeny. The interaction of sires (S) with genotypes (dw+, dw and dwB) of dam (G) was significant at the 5% level. This indicates that the rankings of the sires within each one of the three genotypes of dam were not the same, probably due to non-additive genetic variation among genotypes of dams. The evidence indicated that in general the genes from individual sires combined differently with each type of dam (G). Those genes which combined well with the genes from normal (dw+) dams combined poorly with both the genes from the dwarf (dw) and the genes from the bantam (dwB) dams. The interaction of sires (S) with phenotypes (dwarf and bantam) of progeny (P) was significant at the 10% level. The results indicated a probable gene x genotype interaction for 8-week weight between genes at the dwarf locus (dw and dwB) and the background genotype (single and/or polygenes). The correlation among paternal half-sibs was influenced more by the S x G than by the S x P interaction, but the effects tended to be cumulativ

Foram estimadas repetibilidades (r) e herdabilidades (h²) de características reprodutivas de três populações de galinhas para corte do Setor de Aves da ESALQ/USP Piracicaba, SP. Cento e quinze galinhas foram inseminadas segundo um esquema hierárquico, com sêmen de 23 galos amostrados das populações I, II e III no experimento E1 e de outros 23 galos no experimento E2. Foram utilizadas quatro incubações, ou blocos, em cada experimento. Estimativas de r e h² foram obtidas dentro de experimento, pela análise de variância de médias de galinha em cada incubação. As estimativas de r da produção de ovos (POST) foram significativas (P<0,01) e iguais a 0,19±0,05 e 0,32±0,04 nos experimentos E1 e E2, respectivamente. Quanto a eclodibilidade (ECLOD), as h² estimadas de componentes de variância de galos foram 0,14±0,14 no E1 (P>0,05) e 0,26±0,17 no E2 (P<0,05). No tocante a nascimento de pintos (NASC), as h² estimadas (P<0,05) foram 0,18±0,15 (E1) e 0,26±0,17 (E2). No entanto, h² estimadas com base em componentes de fêmea foram significativas (P<0,01) e maiores: no tocante a ECLOD, as estimativas foram 0,77±0,09 e 0,48±0,20 no experimento E1 e E2, respectivamente, e 0,58±0,21 e 0,48±0,20 quanto a nascimento (NASC). Os resultados confirmam que ECLOD e NASC apresentam variabilidade genética aditiva baixa.

The present study describes the production of stocks segregating dwarf (dw), bantam (dwB) and normal (dw+) alleles, as well as the characters, shank length, adult body weight, age at sexual maturity and egg production. Heterozygous K dw+/k dwB sires were mated to normal (dw+) dams to produce stock D6.a, and mated to dwB females to produce stock D6.b. Stock D4.a came from mating F1 heterozygous dwB dw sires to dwarf Leghorns. In a third series of matings, 7/8 Sebright and 1/8 dw-Leghorn dwB dw sires were crossed to three groups of dams of different genotypes. The progeny of the normal (dw+), dwarf (dw), and bantam (dwB) dams were designated as stocks D4.b, D4.c and D4.d, respectively. The dw+ dams were White Leghorn strain cross females. The difference between the rate of laying of normal (69.7%) and their bantam sisters (68.6%) was not statistically significant when the average 32-week body weight of the dw+ sisters was 1,897 g. However, when the 32-week body weight of the normal daughters from the same sires and smaller dams was around 1,646 g, the difference between the rate of laying of the normal (78.1%) and their bantam sisters (75.9%) was significant (P < 0.05). The dwB gene may have a similar but smaller effect on the rate of egg laying than its dwarf allele. The difference between sexual maturity of normal and bantam daughters of either the largest or the smallest dams was not statistically significant, even though the smallest dwB pullets were in average 2.9 days older at first egg. The use of shank length combined with adult body weight allowed a precise discrimination between bantams and dwarfs
Neste trabalho descreve-se a obtenção de seis plantéis experimentais, segregantes para os alelos ligados ao sexo, dwarf (dw), bantam (dwB) e normal (dw+), em galinhas para ovos. Comparações entre desempenhos entre plantéis hemizigóticos para genes maiores no locus dwarf também foram efetuadas com relação a comprimento de canela medida na 16ª semana de idade, peso do corpo adulto, produção de ovos e maturidade sexual. Machos heterozigotos (K dw+/ k dwB) foram acasalados com fêmeas normais (dw+) e com fêmeas bantam (dwB). As progênies fêmeas, nos referidos acasalamentos, foram denominadas de D6.a e D6.b, respectivamente. Galos 7/8 Sebright e 1/8 dw-Leghorn heterozigotos (dwB dw) foram acasalados com três grupos de galinhas de diferentes genótipos (dw+, dw e dwB). As progênies das mães normais (dw+), dwarf (dw) e bantam (dwB) foram denominadas de plantéis D4.b, D4.c e D4.d, respectivamente. As seguintes conclusões foram relatadas: a) a redução no peso corporal adulto de fêmeas dwarf, em todos os plantéis, em relação a fêmeas bantam, foi menor que a relatada em relação a galinhas normais do tipo ovo; b) a diferença entre a taxa de postura de galinhas normais e suas irmãs bantam não foi estatisticamente significativa em fêmeas dw+ (filhas de mães dw+), pesando 1897 g. Porém, em galinhas dwB com peso médio de 1646 g (filhas de mães dwB), a diferença entre a taxa de postura de galinhas normais e de suas irmãs bantam...