Best-fitted regression models for profitability of two egg-type commercial pullets

This study is focused on describing the most important factors which have a great influence on profitability of egg production of two commercial layer flocks under Egyptian conditions, LSL white and brown. The data for each flock has been collected from seven governorates including the Delta and Upper Egypt zones over the period 2005-2012. General linear procedure was generated to get both least square means and separation of means. Application of stepwise regression was carried to predict the most important factors that affect egg production profitability in US dollar. White egg layers had significantly higher net profit per hen than the brown egg type, being as 12.2 vs. 12.1 cents for the white and brown type egg layers, respectively. Closed houses and battery systems were the preferred systems for the white-egg genotype where pullets achieved significantly higher egg income over feed coast by 15.9 and 14.9 cents for closed and battery system, respectively compared to 10.9 and 11.5 cents for the LSL brown one, respectively. Open houses and floor systems were profitable for brown-egg genotype by recording a significantly higher profitability as 13.3 and 12.7 cents, respectively copmared to 8.7 and 9.7 cents for the white-egg genotype.Both white and brown-egg types had recorded significantly higher net profitability under delta zone rather than upper Egypt by 2.2 cents and 2.1 cents, respectively. Application of the stepwise regression procedure was to predict the net profit (Y) from three independent variables, egg weight (X1), egg price (X2), and hen housed egg production (X3). Generally, LSL white layers, egg price (X2) had the highest share in profitability by 44.24% compared to hen housed egg production (X3) that share 29.98%. For LSL brown layers, egg weight (X1) is the most important factor accounting for the profitability in cents. Its relative importance to the profitability is 57.24% followed by egg price (X2) 21.25%. Hen housed egg production (X3) had very little share 0.14%.

Genetic architecture and genomic selection of female reproduction traits in rainbow trout

Background

Rainbow trout is a significant fish farming species under temperate climates. Female reproduction traits play an important role in the economy of breeding companies with the sale of fertilized eggs. The objectives of this study are threefold: to estimate the genetic parameters of female reproduction traits, to determine the genetic architecture of these traits by the identification of quantitative trait loci (QTL), and to assess the expected efficiency of a pedigree-based selection (BLUP) or genomic selection for these traits.

Results

A pedigreed population of 1343 trout were genotyped for 57,000 SNP markers and phenotyped for seven traits at 2 years of age: spawning date, female body weight before and after spawning, the spawn weight and the egg number of the spawn, the egg average weight and average diameter. Genetic parameters were estimated in multi-trait linear animal models. Heritability estimates were moderate, varying from 0.27 to 0.44. The female body weight was not genetically correlated to any of the reproduction traits. Spawn weight showed strong and favourable genetic correlation with the number of eggs in the spawn and individual egg size traits, but the egg number was uncorrelated to the egg size traits. The genome-wide association studies showed that all traits were very polygenic since less than 10% of the genetic variance was explained by the cumulative effects of the QTLs: for any trait, only 2 to 4 QTLs were detected that explained in-between 1 and 3% of the genetic variance. Genomic selection based on a reference population of only one thousand individuals related to candidates would improve the efficiency of BLUP selection from 16 to 37% depending on traits.

Conclusions

Our genetic parameter estimates made unlikely the hypothesis that selection for growth could induce any indirect improvement for female reproduction traits. It is thus important to consider direct selection for spawn weight for improving egg production traits in rainbow trout breeding programs. Due to the low proportion of genetic variance explained by the few QTLs detected for each reproduction traits, marker assisted selection cannot be effective. However genomic selection would allow significant gains of accuracy compared to pedigree-based selection.