Genetic relationships between selection for growth and reproductive effectiveness

Abstract

The domestic and international poultry industries have gone through many changes over the last 50 yr. One constant in the meat-type poultry industry has been the emphasis on genetic improvement of growth. Using lines from a double, divergent selection experiment, data are presented on the genetic relationships between growth to different ages and reproductive parameters. During the last three generations of selection an in vitro sperm binding assay was used and evaluated for its usefulness in a selection program for growth-related phenotypes. Growth to different ages can have markedly different genetic architecture, compared to evaluating body weight at a fixed age. Growth is a nonlinear phenomenon and should be evaluated as such within the context of a genetics program. Fertility is positively correlated with growth to 14 d of age (EGR14), but negatively correlated with growth to 42 d of age (EGR42). This difference is primarily due to the high, negative correlation between exponential growth from 14 to 42 d of age (EGR14/42) and reproductive phenotypes. Roosters were also evaluated with an in vitro sperm binding assay, which is highly correlated with fertility. The genetic architecture of the sperm binding assay was very similar to that of fertility, with an additive genetic correlation of 0.75. Further, it was shown that culling the worst 25% roosters on the basis of the sperm binding assay would have very little effect on the growth performance of the resulting progeny, yet increased the number of chicks produced per rooster by 10 to 25% (depending upon the population).

Egg Production Performance in a Nigerian Local Chicken Ecotype Subjected to Selection

“…The mean BWFE of the LE over the three generations for the control line were generally within the range reported for unselected local chicken in southern Nigeria (Okpeku et al, 2003;Ogbu and Omeje, 2011) and by Ndofor-Foleng et al (2010) for the LE. The increase in the BWFE, AFE, WFE and EW in subsequent generations of selection confirms the report of Barbato (1999) that body weight has been shown to be highly responsive to selection such that genetic improvement for growth has resulted in increase in the egg weight and age at sexual maturity.…”

Sperm subpopulations in avian species: a comparative study between the rooster (Gallus domesticus) and Guinea fowl (Numida meleagris)

“…However, the CASA-Morph system shows promise as a valuable tool for male selection and fertility determination owing to: (1) the possible correlation of avian sperm morphometry with fertility, (2) the detection of different morphometric phenotypes characterizing a given male or species, (3) the management of each sperm morphometric phenotype for male selection, (4) the detection of different sperm pathologies, and (5) the possibility of performing new studies for fertility determination, such as the objective analysis of sperm morphometric subpopulations. Therefore, avian males might be screened efficiently at the onset of semen production for certain sperm phenotypes and then be selected or culled depending on their reproductive potential 27. Although the filiform morphology of rooster and Guinea fowl sperm is similar, the results described in the present study suggest that rooster and male Guinea fowl appear to have species-specific differences in sperm morphometry and sperm subpopulation structure.…”

Testis development and gonadotropin secretion in broiler breeder males

“…Genetic selection over the past 55 yr has been associated with loss of reproductive efficiency in males and females (Rappaport and Soller, 1966;Reddy, 1996;Barbato, 1999).…”