The Genetic Architecture of the Chickens Dropping Moisture by Genetic Parameter Estimation and Genome-Wide Association.

Tao Zhu,Weifang Yang,Yaxiong Jia,Zi Guan,Xueze Lv,Liang Wang,Zhonghua Ning,Yu Chen,Xiaoyu Zhao,Junhui Wen,Lujiang Qu,Tong-Yu Zhang

doi:10.3389/fgene.2020.00806

Abstract

Dropping moisture (DM) refers to the water content of feces. High DM in chickens could be disadvantageous to pathogen control and fecal treatment in chicken farms. DM can be affected by environment, nutrition, disease, and genetics. In the present study, significant individual differences were presented in the DM of Rhode Island Red (RIR) chicken population, indicating that genetics could contribute to DM in the chickens. Subsequently, we estimated the genetic parameters of DM and conducted a genome-wide association study (GWAS) to find the potential genomic regions related to DM. The results showed that the heritability of DM ranged from 0.25 to 0.32. Furthermore, 11 significant loci on chromosome 7 were found to be associated with DM levels by the GWAS. The SNP rs15833816 within the COL6A3 gene was the most significant SNP related to DM. Hens carrying the G allele including GA and GG produced higher DM (P < 0.01) levels than those carrying the other genotype AA. Our results showed that DM is a medium-inheritable trait and that COL6A3 could be a potential candidate gene that regulates DM level in chickens.

Highlights

The cloaca in laying hens is a passage at the end of the digestive, urinary, and reproductive systems and includes the urethra, ejaculation canal, and anal canal
In order to study the relationship of Dropping moisture (DM) to cage height and chicken performance, cage height, egg number (EN), and egg weight (EW) at age 48 weeks were recorded for further analysis
The variance component was estimated by Eq 1; Strategy 2: To avoid the artificial bias, DM level numbers were added for the five times to represent the severity of DM (SDM) for each chicken, consider that SDM is not normal distribution as SDM is an integer between 5 and 20, SDM was divided into norm (SDM ≤ 6), slight (7 ≤ SDM ≤ 9), medium (10 ≤ SDM ≤ 14), and severe (SDM ≥ 15) according to the SDM distribution (Figure 2), and the variance component was estimated Eq 2

Summary

Introduction

The cloaca in laying hens is a passage at the end of the digestive, urinary, and reproductive systems and includes the urethra, ejaculation canal, and anal canal. Because of the unique excretory organ of chickens, feces and urine are mixed together and excreted through the cloaca, and the moisture content of hen feces is typically higher than that of some other animals. Excess dropping moisture (DM) can severely affect the economic benefits of the laying hen industry. High DM can reduce the digestibility of chicken. Water-like feces attract more insects and bacteria in the summer, and high-DM feces are prone to releasing NH3, H2S, and other harmful gases that threaten the biological safety of laying hens (Jongebreur and Monteny, 2001; Achiano and Giliomee, 2005)

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Results

Conclusion