Controlling reproductive hormone levels to optimize fertility in lactating dairy cows

Adequate fertility in lactating dairy cows is important to optimize milk production and profitability on dairy farms. Despite this, fertility has generally been declining on dairy farms over the last 60 years. This is, at least in part, due to the high metabolic demand and substantial feed intake of modern dairy cows which may result in decreased hormone levels in lactating cows. Previous work has been done to devise methods to help control hormone levels and thereby improve fertility, but more refinement of these methods is necessary to make them available to a wider range of farms. Towards this aim, an additional injection of GnRH was added 7 days prior to presynchronization with simultaneous PGF2α and GnRH in order to improve ovarian responsiveness of subsequent hormonal injections of the synchronization protocol, however this additional injection did not improve ovarian response or pregnancies per artificial insemination in lactating dairy cows. Next, cows were treated at the time of artificial insemination after estrus detection with an injection of GnRH aimed at increasing ovulation rate, progesterone concentration post-insemination, and increase pregnancies per artificial insemination, however no overall improvement in fertility was observed in cows treated with GnRH. While GnRH has been commonly used on dairy farms to induce ovulation or luteinization, approaches using novel signaling molecules may improve ovulation rate or be luteotropic and to that end a seminal plasma protein, nerve growth factor-β (NGF), was used next to augment the effects of GnRH within a synchronization protocol. In this study NGF was administered concurrently with GnRH for the GnRH treatment given immediately before insemination. While there was an interaction between treatment with NGF and parity (primiparous vs. multiparous) for plasma progesterone concentration, there was not an increase in pregnancies per insemination in NGF-treated cows compared to saline treated controls. Finally, I aimed to refine the case definition for early post-partum metabolic disease related to energy metabolism to better target cows that may respond to glucose-precursor treatment, regarding reproductive outcomes. This was done by measuring both whole blood glucose and ketone concentration and randomly assigning cows to treatment followed by measurement of reproductive outcomes. Cows with hypoglycemia with or without hyperketonemia produced more milk and surprisingly cows with hypoglycemia did not have poorer reproductive performance than cows without metabolic abnormalities. Treatment with a glucose precursor did not improve fertility for cows with hypoglycemia. In conclusion fertility treatments in these studies did not produce overall improvements to pregnancies per insemination, however this investigation did highlight possible subpopulations of cows which may demonstrate improved fertility from treatment.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

VMS - Comparative Biosciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Hubner, Andrew

Contributors dc:contributor

• Canisso, Igor
• Lima, Fabio
• Ko, CheMyong
• Flaws, Jodi
• Spinella, Michael
• Cardoso, Phil

• cow
• fertility

Statement dc:rights

• Copyright 2022 Andrew Hubner

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/115328

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F115328