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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Animal Biosciences & Biotechnology Laboratory » Research » Publications at this Location » Publication #339761
Title: Identification of gene expression differences associated with high and low egg production in turkey hens

Author
item BRADY, KRISTEN - University Of Maryland
item Long, Julie
item PORTER, TOM - University Of Maryland

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/11/2017
Publication Date: 7/17/2017
Citation: Brady, K., Long, J.A., Porter, T.E. 2017. Identification of gene expression differences associated with high and low egg production in turkey hens. Meeting Abstract. 96:68.

Interpretive Summary:

Technical Abstract: Variation in egg production exists in commercial turkey hens, with low producing hens costing more per egg produced. Ovulation is governed by the hypothalamic-pituitary-gonadal (HPG) axis, and total egg production is correlated with ovulation frequency. Each ovulation is stimulated by a preovulatory surge (PS) of progesterone and luteinizing hormone (LH), caused by release of gonadotropin releasing hormone (GnRH). Ovulation can be inhibited by release of gonadotropin inhibiting hormone (GnIH). Differences in the HPG axis between low and high egg producing turkey hens were explored by determining mRNA levels for key genes of the HPG axis, both outside and during the PS. From the top and bottom 15% in egg production of 200 commercial line hens, six high egg producing hens (HP) and six low egg producing hens (LP) were sampled, taking the hypothalamus, pituitary, as well as the granulosa layers of the largest follicle (F1G) and the fifth largest follicle (F5G), half outside of the PS and half during the PS (n=3 per group). The mRNA levels of key genes in the HPG axis involved in progesterone production were examined using RT-qPCR. An ANOVA using the mixed models procedure of SAS compared normalized mRNA levels between LP and HP, both outside and during the PS. LP exhibited increased mRNA levels for genes associated with ovulation inhibition, such as hypothalamic GnIH and pituitary GnIH receptor (GnIHR), as well as decreased mRNA levels for genes associated with ovulation stimulation, such as pituitary follicle stimulating homone (FSHß) and LH (LHß)(p<0.05; n=3). Interestingly, LP demonstrated increased mRNA levels for both the FSH receptor (FSHR) and the LH receptor (LHCGR) in the F5G, as well as the progesterone receptor (PGR) in the hypothalamus (p<0.05; n=3). Genes associated with progesterone production, steroidogenic acute regulatory protein (STAR), cholesterol side-chain cleavage enzyme (CYP11A1), and 3ß-hydroxysteroid dehydrogenase (HSD3B1), tended to be up-regulated in the F1G of HP; while, in LP, these genes appear to be up-regulated in the F5G instead (p<0.05; n=3). Different degrees of stimulation and inhibition within the HPG axis at the mRNA level were noted in LP and HP turkey hens, requiring further investigation into the mechanisms by which these differences could ultimately influence egg production.