Abstract
Accurate estrus detection method is the need of the hour to improve reproductive efficiency of buffaloes in dairy industry, as the currently available estrus detection methods/tools lack high sensitivity and specificity. Recently, circulating miRNAs have been shown as non-invasive biomarkers by various studies. Hence, in order to evaluate their potential as estrus biomarkers, the objective of this study was to identify and compare the levels of 10 hormone-responsive miRNAs in the urine collected at proestrus (PE), estrus (E), and diestrus (DE) phases of buffaloes (n = 3) pertaining to a discovery sample. Among 10 urinary miRNAs, the levels of bta-mir-99a-5p (E/PE 0.5-fold, P < 0.05; DE/PE 1.9-fold), bta-miR-125b (E/PE 0.5-fold; DE/PE 0.7-fold), bta-mir-145 (E/PE 1.5-fold; DE/PE 0.7-fold), bta-mir-210 (E/PE 1.2-fold, DE/PE 0.7-fold), mir-21 (E/PE 1.5-fold, DE/PE 2-fold), and bta-mir-191 (E/PE 1.3-fold; DE/PE 0.8-fold) were found to be altered during different phases of buffalo estrous cycle. In contrast, bta-mir-126-3p, bta-let-7f, bta-mir-16b, and bta-mir-378 were undetected in buffalo urine. Furthermore, a validation study in an independent group of 25 buffalo heifers showed the increased levels of urinary bta-mir-99a-5p during the DE (3.92-fold; P < 0.0001) phase as compared to the E phase. Receiver operating characteristic curve analyses also revealed the ability of urinary miR-99a-5p in distinguishing the E from the DE phase (area under the curve of 0.6464; P < 0.08). In silico analysis further showed an enrichment of miR-99a-5p putative targets in various ovarian signaling pathways, including androgen/estrogen/progesterone biosynthesis and apoptosis signaling, implicating the role of miR-99a-5p in ovarian physiology. In conclusion, significantly lower levels of bta-mir-99a-5p at the E phase than the DE phase in buffalo urine indicate its biomarker potential, which needs to be further explored in a large cohort in the future studies.
Highlights
Dairy farming is one of the most significant parts of the agriculture sector in India
Several factors lead to poor reproductive performance of buffaloes, including delayed puberty, silent miR-99a-5p in Buffalo Estrus Detection heat, variation in calving interval, and low conception rate [1, 3], but silent estrus is the major cause of concern [3]
An accurate estrus detection in buffaloes is essential for effective reproductive management via successful conception, which is usually achieved by carrying out artificial insemination (AI) generally during ovulation that occurs ∼10– 12 h after the end of an estrus (E) phase in cattle and buffaloes [10]
Summary
Dairy farming is one of the most significant parts of the agriculture sector in India. Buffaloes are usually found in Southeast Asia and the Mediterranean region [1] They are preferred over other farm animals in India for their higher financial returns via milk and meat, better efficiency in utilizing low-quality feed, and resistance to tropical diseases [1, 2]. Several factors lead to poor reproductive performance of buffaloes, including delayed puberty, silent miR-99a-5p in Buffalo Estrus Detection heat, variation in calving interval, and low conception rate [1, 3], but silent estrus is the major cause of concern [3]. An accurate estrus detection in buffaloes is essential for effective reproductive management via successful conception, which is usually achieved by carrying out AI generally during ovulation that occurs ∼10– 12 h after the end of an estrus (E) phase in cattle and buffaloes [10]. There is an urgent requirement to develop a highly sensitive and specific estrus detection method for buffaloes to increase the AI success rate
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