Intrinsic and extrinsic factors that influence ovarian environment and efficiency of reproduction in cattle

Abstract

All the somatic cells composing a mammalian organism are genetically identical and contain the same DNA sequence. Nevertheless, they are able to adopt a distinct commitment, differentiate in a tissue specific way and respond to developmental cues, acquiring a terminal phenotype. At the end of the differentiation process, each cell is highly specialized and committed to a distinct determined fate. This is possible thanks to tissue-specific gene expression, timely regulated by epigenetic modifications, that gradually limit cell potency to a more restricted phenotype-related expression pattern. Complex chemical modifications of DNA, RNA and associated proteins, that determine activation or silencing of certain genes are responsible for the 'epigenetic control' that triggers the restriction of cell pluripotency, with the acquisition of the phenotypic definition and the preservation of its stability during subsequent cell divisions. The process is however reversible and may be modified by biochemical and biological manipulation, leading to the reactivation of hypermethylated pluripotency genes and inducing cells to transit from a terminally committed state to a higher plasticity one.These epigenetic regulatory mechanisms play a key role in embryonic development since they drive phenotype definition and tissue differentiation. At the same time, they are crucial for a better understanding of pluripotency regulation and restriction, stem cell biology and tissue repair process.

The Effects of Evaporative Cooling on Folliculogenesis and Ovarian Hormones during the Estrous Cycle of Dairy Holstein Cows during the Summer Months in Saudi Arabia

“…In addition to the reduced number of small follicles, the findings showed that HS negatively affected the number of medium follicles (6 -9 mm diameter), which is consistent with other studies [15]. The decreased number of medium follicles is an indication that HS depresses follicular dominance in the first and second follicular wave [26]. Mediums follicles are sensitive indicators of follicular dominance since the dominant follicle inhibits the growth of subordinate follicles [31].…”

“…The development of follicles has been reported to be damaged [26] or altered [27] by HS during folliculogenesis, with a delayed negative effect on ovarian function. Decreased LH pulse and frequency have been reported because of HS [28].…”

Genetic Parameters and Genome-Wide Association Studies for Anti-Müllerian Hormone Levels and Antral Follicle Populations Measured After Estrus Synchronization in Nellore Cattle

“…In vitro fertilization and cattle embryo production are common practices in beef cattle production systems, especially in Zebu breeds [ 13 , 14 , 15 ]. The measurement of AMH concentration and its association with reproductive and fertility traits were widely studied in livestock, including cattle [ 16 , 17 , 18 , 19 , 20 , 21 ]. These studies indicated that circulating AMH levels are a useful indicator of fertility and reproductive performance.…”

“…These studies indicated that circulating AMH levels are a useful indicator of fertility and reproductive performance. The role of AMH in different aspects of reproductive physiology is noteworthy, and it is involved with AFP [ 16 , 22 ], superovulation responses [ 23 ], in vitro embryo production [ 10 , 24 , 25 ], fertility traits (i.e., age at puberty and postpartum interval) [ 26 ], and longevity [ 27 ] in beef cattle. The definition and use of efficient biological indicators of fertility is a promising path to increase the success of reproductive technologies (e.g., embryo transfer, superovulatory responses), especially in Nellore cattle raised in tropical conditions.…”

Forecasting the Embryo Productivity of Donor Cows on the Basis of Echographic Characteristics of the Ovaries

“…Analysis of reported dataindicates that the effectiveness of the response of the ovaries of embryo donor cows to the exogenous gonadotropin is influenced by many factors [18]. The major are the breed and physiological state of the animals [19,20], especially metabolic [21] and hormonal status [22][23][24][25], genetic predisposition [26][27][28][29][30], ecological and climatic conditions [31,32].…”