Document Type

Dissertation/Thesis

Date Created

5-10-2020

Abstract

The corpus luteum is a transient steroidogenic endocrine gland that forms from the remnants of the ovulatory follicle. This gland is responsible for the synthesis and secretion of the hormone progesterone, which is critical for the establishment and maintenance of pregnancy. In a non-pregnant cow, PGF2a is released from the uterus to regress the corpus luteum. However, in the case of pregnancy, the embryo must mitigate PGF2a synthesis to prevent corpus luteum regression. If the embryonic signal is either too late or too weak, uterine PGF2a secretion may result in corpus luteum regression and termination of pregnancy. Omega-3 fatty acids from fish byproduct may provide a nutraceutical approach to reduce luteal sensitivity to PGF2a, which provides a potential solution to early embryo loss. Recent data show that incorporation of omega-3 fatty acids into luteal tissue reduces sensitivity to PGF2a. However, mRNA for key genes that regulate progesterone synthesis were significantly decreased. It was hypothesized that omega-3 fatty acids may allow for a rebound in mRNA or adequate luteal cell protein abundance allowing for synthesis and secretion of progesterone following intrauterine infusions of PGF2a. Additionally, it was hypothesized that omega-3 fatty acids from fish byproduct affect both lipid droplet accumulation and size in bovine luteal tissue and cells, as well as mitochondrial dynamics, providing a lipid rich and healthy environment for steroid synthesis following PGF2a infusions and a low oxygen environment. Data from the present study show that fish oil supplementation was luteal protective in response to PGF2a infusion. Steady-state mRNA for key genes that regulate steroidogenesis was significantly increased at 48 h post PGF2a infusion as compared to animals receiving vegetable oil supplementation. Additionally, fish oil supplementation in vitro improved luteal cell mitochondrial morphology as compared to control cells in a low oxygen environment. In conclusion, supplementation of fish oil improved luteal function during PGF2a infusion and hypoxia. Outcomes from these studies may allow for development of novel feeding strategies to reduce luteal sensitivity during maternal recognition of pregnancy resulting in improved reproductive efficiency in cattle.

Keywords

bovine; reproduction; endocrinology; embryo; progesterone; steroidogenesis

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