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Kerala Veterinary and Animal Sciences University, Wayanad

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20211
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Subject: Veterinary Anatomy and Histology × Author: ANNIE V. RAJ × Start date: 2020 ×
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    ThesisItemOpen Access
    FACTORS OF ANATOMICAL AND GENETIC ORIGIN PREDISPOSING TO INFERTILITY IN CROSSBRED DAIRY COWS
    (COLLEGE OF VETERINARY AND ANIMAL SCIENCES MANNUTHY, THRISSUR -, 2021-03-08) ANNIE V. RAJ; K.M. Lucy
    Factors of anatomical and genetic origin predisposing to infertility in crossbred dairy cows were studied using the genitalia collected from 100 dairy cows / heifers from the Meat Technology Unit, Mannuthy. This included six animals culled on account of factors other than infertility with normal reproductive system (control group) and the remaining animals with a known history of infertility. Morphology, morphometry, histology and histochemistry of genitalia, immunohistochemistry of IGFBP-2, scanning electron microscopic peculiarities of various regions of affected genitalia, biochemical analysis of follicular fluid and validation of SNPs of candidate genes were studied. Standard procedures were adopted for histoarchitectural and histochemical studies. Among the group of 100 animals under study, 14 animals showed anatomical defects in the genitalia. Considering the total number of female animals maintained in the farms, the overall incidence of anatomical abnormalities of genitalia was estimated to be 1.24 per cent. Crossbred Holstein Friesian showed a higher incidence of anatomical defects in the genitalia followed by Frieswal and crossbred Jersey. Cervical abnormality was the most common type noticed followed by ovarian hypoplasia, Mullerian duct abnormalities viz., bicornis bicorpus unicollis, uterus unicornis and tubal obstruction. Histologically, fibrous tissue proliferation was the characteristic feature of hypoplastic ovary with the absence of cyclical structures. In the genitalia with tubal obstruction, lamina epithelialis was detached from the mucosa to form clumps in the lumen. The tunica muscularis was approximately twice thicker than the normal oviduct. In uterus unicornis condition, the ovaries showed degenerated primary follicles and degenerating corpora lutea with hyalinised masses. Left uterine horn was absent and in its position, a membranous structure was seen. Right uterine horn revealed an unusual architecture. In the case of bicornis bicorpus unicollis, all the regions were normal. In kinked cervix condition, the cervical wall showed abundance of fibrous tissue and signs of degeneration. Histochemically, carbohydrates, lipids and phosphatases were demonstrated in different regions of the affected genitalia. IGFBP-2 was localized in the primordial and atretic follicles in the hypoplastic ovary. In uterus unicornis condition, invading granulosa cells into the regressing CL and atretic follicles in the cortical region showed a highly positive immunoreaction. Scanning electron microscopic structure of different regions of genitalia with anatomical defects was also explored. Biochemical analysis of follicular fluid revealed that the mean concentrations of potassium, triglycerides, urea, nitrogen, cholesterol, copper and magnesium were higher in group 2 animals. Single nucleotide polymorphisms reported in the study population by ddRADseq in four candidate genes viz., wnt7a, emx2, hoxa13 and lhx1 affecting the development of female reproductive tract were selected for validation. To identify the single nucleotide variations in bovine wnt7a, PCR was performed and the sequence analysis of 273 bp amplicon revealed the targeted SNP at position 89 (A→G transition) and three novel SNPs at positions 119 (A→G transition), 195 (C→ T transition) and 196 (T→A transversion). For identifying the SNP in bovine emx2, PCR - RFLP was performed and confirmed the population as homozygous. To identify the SNP in bovine hoxa13 and lhx1, HRM was performed and did not show any polymorphism. Amplification of exon 2 of foxa2 by PCR revealed polymorphism at 168th position (T→C transition) of the 320 bp product. This highlights the vital role of wnt7a in regulation of reproduction in bovines. The information gathered by this study will provide insights to the extent and causes of infertility among crossbred dairy cattle of Kerala. Biochemical analysis of follicular fluid is a potent tool for assessing reproductive status. The candidate gene wnt7a can be used for genome-wide scans of anatomical abnormality in bovine species at early stages itself so that the route cause can be eliminated by culling such animals. The findings will also be useful for diagnosing and minimizing the anatomical causes of reproductive disorders so that conception rate of the herd can be increased thus reducing economic loss to the farmers.