Selection and the reproductive axis

Can on-farm management influence layer flock turnover for the better?
Nerine T. Joseph
Monday, 02 January 2017
By Nerine T. Joseph
Grégoy Bédécarrats and his team are working to find out whether intensive genetic selection of commercial layer chickens has impacted control of the reproductive or  hypothalamic–pituitary–gonadal (HPG) axis.
Grégoy Bédécarrats and his team are working to find out whether intensive genetic selection of commercial layer chickens has impacted control of the reproductive or hypothalamic–pituitary–gonadal (HPG) axis.
The Poultry Industry Council (PIC) funded several research projects in 2016.  The following project addresses the layer sector of the poultry industry directly.
 
Grégoy Bédécarrats and his research team from the University of Guelph will be performing research which investigates the control of reproduction in poultry, within the context of a continuously evolving genetic makeup.

HPG axis
Specifically, the study will seek to reveal whether intensive genetic selection of commercial layer chickens has impacted control of the reproductive or HPG axis. HPG axis refers to the hypothalamus, pituitary gland, and gonadal glands as a single system because these glands often act in concert.

In an interview, Bédécarrats described recent research in which he observed that modern strains of layers no longer fully fit the accepted neuroendocrine models.  He hypothesized, “While doubling egg numbers laid per hen, the past 50 years of genetic selection may have altered the normal physiological controls.”  

Key questions
Bédécarrats highlighted the key questions being formulated through recent analysis of commercial layers, “Why do they tend to mature without stimulation?  Why do they display extended laying persistency?  Is there desynchronization of the ovulatory process?”

Purpose of the strain
The proposed research aims to answer these questions by comparing a strain not selected for egg production versus a modern commercial strain selected for egg production.    The approach is to compare production parameters and relate these to molecular events.  Differences in the function of the HPG axis between the two strains will be identified.  Bédécarrats explains “Identifying differences between strains will give insight into the understanding of the actual mechanisms responsible for maturation, ovulation and persistency of lay.  This will show how genetic selection may have impacted the reproductive axis.”

Study objectives
The initial objective of the study will be to determine the relative importance of photostimulation versus metabolic status to initiate sexual maturation in commercial layers.  The study will then go on to investigate if a previously observed second estradiol peak is specific to modern commercial strains and correlated with laying persistency.  The study will conclude by determining if the second estradiol peak is the result of activation of the entire reproductive axis as opposed to independently ovarian activation.

Outcomes
“Outcomes of this research will assist in adjusting and/or refining on-farm management procedures and could help update codes of practice as it relates to layer flock turnover,” Bédécarrats said.

This research is funded by the Natural Sciences and Engineering Research Council of Canada’s Discovery Program and the Ontario Ministry of Agriculture, Food and Rural Affairs - University of Guelph Research Program.

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