|MAHNANI, ABOLFAZL - Isfahan University Of Technology|
|SADEGHI-SEFIDMAZGI, ALI - Isfahan University Of Technology|
|ANSARI-MAHYARI, SAEID - Isfahan University Of Technology|
|GHIASI, HEYDAR - Collaborator|
Submitted to: Theriogenology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2022
Publication Date: 4/14/2022
Citation: Mahnani, A., Sadeghi-Sefidmazgi, A., Ansari-Mahyari, S., Ghiasi, H., Toghiani, S. 2022. Genetic analysis of retained placenta and its association with reproductive disorder, production, and fertility traits of Iranian Holstein dairy cows. Theriogenology. 189:59-63. https://doi.org/10.1016/j.theriogenology.2022.04.008.
Interpretive Summary: Retained placenta (RP) is a costly postpartum reproductive disorder in multiparous dairy cows. It increases the culling rate in the herd due to decreased milk production and increased incidence of other diseases in early lactation. The objectives of this study were to: 1) investigate the proper model for estimating the genetic parameters of RP using pedigree information 2) identify the genetic relationship between RP with reproductive disorders, production, and fertility traits in dairy cattle. The results have shown low heritability for RP using linear (0.03) and threshold (0.09) model. The threshold model was more suitable for estimating genetic variance for binary traits like RP, but the computation could be slow and expensive for large datasets or result in a lack of convergence in some instances. The estimated genetic correlation between RP and fertility and reproductive disorder traits was moderately positive indicating that cows susceptible to RP were genetically more prone to fertility and health issues. As a result, selecting against RP incidence in a dairy herd will simultaneously improve the fertility and reproductive disorders. In contrast, the estimated genetic correlation between RP and milk components in different days in milk was moderately negative, implying that cows with higher production, especially in earlier lactation, are less likely to develop RP incidence. Incorporating traits such as reproductive disorder or health traits, in a selection index will enable us to better rank the most profitable animals in the dairy herd.
Technical Abstract: The objectives of this study were to infer genetic parameters for retained placenta (RP) and its genetic correlation with reproductive disorder, production, and fertility traits in Iranian Holstein dairy cows. Data consisted of 154,048 lactation records of 59,610 Holstein dairy cows from 9 herds and collected between 2011 and 2018. Records of fertility were obtained for days from calving to first service (DFS), number of inseminations to conception (NIC), days open (DO), and success in first insemination (SFI) and reproductive disorder traits measured for dystocia, stillbirth, and twinning. The estimates of genetic parameters for RP trait were implemented by using univariate linear and logistic animal models using ASREML software. The former animal model used to implement bivariate analysis to investigate the presence of genetic correlations between RP with reproductive disorder, production, and fertility traits. Heritability estimates for RP trait was low in both linear (0.031) and logistic (0.09) animal model. Estimated genetic correlations between RP and twinning (-0.04), stillbirth (0.32) and dystocia (0.34), in both cows and heifers, implying that selection against RP could indirectly select against dystocia and stillbirth except for twinning. Estimated genetic correlations between RP and milk production components across 100, 200, and 305 days ranged from -0.12 to -0.29, and the highest correlation (-0.29) was associated with the first 100 days in milk period. In addition, a moderate positive genetic correlation (0.25) between RP and fertility traits (DO, DFS, NIC) was estimated, while a low and unfavorable genetic correlation (-0.09) was estimated between RP and SFI. In general, the pedigree-based genetic analysis of RP showed that this trait has low heritability and has unfavorable genetic correlation with reproductive disorder, production, and fertility traits. Selection against RP can reduce the incidence of reproductive disorder and improve fertility and production traits.